Twin charged mischief –a risky parochial build, predicated on twisted logic
 

Quote (loosely translated)
“Ze turbo is good and ze supercharger is good, so having both must be very good!”
Unemployed VW TSI project manager

Who would have thought, that we would ever see OEM twin charged systems on the market?
The VW twin charged TSI engine is a bit of an enigma though.
Why would you add all that complexity and cost, just to get slightly more power and 6% better fuel economy? I think Volvo is doing a bit better in this regard, but they still may not be successful.

Certainly Eaton think there is future in this technology, since they have developed a supercharger specifically for twin charging. (TVS v2)
Read about it here
http://www.google.ca/url?sa=t&rct=j&...e91uf6pSv22sHA

I have always wanted to do a twin charged build.It certainly is not an easy build, but I have always wondered what the performance would really be like, and very little seems to be shared from the few that have successfully done this (although recently I have hooked up with a board member here, who has a twin charged system working). I have not wanted to tackle this project because I thought the control system would be too complex. I then connected with a chap from Sweden, who had twin charged his Volvo with basically just 1 valve controlling things. The trick is to have the supercharger blow through the turbo, with the disadvantage being that you don’t get compound boosting. I don’t have access to E85, so I am am not that concerned about compound boosting. He was using a Volvo valve out of a boat.
It seemed like a good plan.

Here is the system: (note in this drawing the Volvo valve has been replaced with ETB#2)


Attachment 181794

Some twisted logic for tackling this;
-my previous builds have not been reliable, mostly due to the superchargers breaking. I am running them well above "normal" SC boost levels. This will allow me to get better HP, yet still not drive the supercharger too hard. (ie, this could actually be more reliable)
-I'm looking for another project.
-for science.
-this can be done in stages, so I will be able to drive the car during build.
-doing another build with just a leading edge turbo (EFR), or leading edge supercharger (whipple), would likely be more expensive.(well at least until things start breaking)

Some logic for not tackling this;
-very complex build which means high risk of not getting things working or running reliably.
-lots of time and effort for what real gain?
-blah blah blah blah.

on with the build.

So I have built some custom stuff.Pics of my previous 2 supercharger builds, that worked until they broke.

M90

Attachment 181792

MP90

Attachment 181793

I do have 1 turbo project under my belt. (no disrespect intended to churbo owners)

If the embedded video does not work, try this.https://www.youtube.com/watch?v=c2u-EmchGGc&feature=youtu.be

Supporting mods:
Fuel – Walbro255, ID750 injectors, M-Tuned rail, stock press regulator.
Spark –Dual MSD-6A’s, driving stock 90 coils.
Computer –MS2 on custom PCB
Engine –forged rods and oil pump, coated stock 96 pistons, 99 head with 1mm oversize intake valves and minor porting/deshrouding.
Drivetrain –centerforce clutch/pp, 6 speed, 4.1 torsen.
Exhaust 2.5” magnaflow rear muffler and resonator with carsound 200cell cat.

Recent car picture
Attachment 181791




The bad news:
I cannot fab stuff like say Patsmx5. In fact, I am rather slow and at times need to remake stuff when the first attempt fails.
The good news:
I started this project in the fall of 2015, and I expect to be done in the spring of 2017.

So I will update this thread with progress to date, as quick as I am able.

Right on dude! Didn't realize our cars were the same color.

Good luck on the build! I will be following your build to see what's next! I like how your going to plumb the new setup, the simplicity will make the control system easy as you say.

Yah! Mariner Blue is the best Miata color ever! (ok, kidding)

Thanks, I probably need all the luck I can get.



So the first thing I wanted to do, is lay my hands on one of the Volvo valves.Fortunately, a used one came up on Ebay which I snagged for $65. I got it in my hands and was not impressed.The valve was huge, and it used various sizes of connecting pipes, from 3.1” to 3.4”.It had to be mounted parallel with the ground, since it required gravity to operate. It also employed 3 hose connections, which would not work for my setup.
https://cimg6.ibsrv.net/gimg/www.mia...4963b34f13.jpg

I knew this thing would not fit under the hood for sure, so even though I had no idea if I could ever get it to fit, I decided to work on chopping it down in size.
Most of the excess was on the input side of the valve (LHS in picture), so I cut that end off, and rebuilt it using a 3” aluminum pipe, fibreglass mesh and a few tubes of JBWeld glue.

Here is how the valve looked after the downsizing operation.

http://i122.photobucket.com/albums/o...psaehbyksn.jpg

Unfortunately, later testing would reveal that this thing would still not fit.So I ended up modifying a Nissan Maxima throttle body at a later date.

While playing with the Volvo valve, I tried to hone in on the parts I wanted to use on the build.
Unlike a ‘turbo only’, or ‘supercharger only’ build I felt I had more flexibility on how old the technology of the part I was using could be.
If the turbo was large and spooled really slowly, then bring it on (as long as it was efficient where I planned on operating it).
Same goes with the supercharger, but I did need it to pump a reasonable amount of air at lower engine RPM’s.

I set my initial goals at 200ft/lb at 2000rpm and ~350hp at 7000ish and decided to do the turbocharger part of the build first.

I would purchase and install the parts in the winter of 2016 and run the car, “turbo only” during the summer of 2016, working out any bugs which cropped up.This would also give me the opportunity to build some of the SC parts, during the summer, while still giving me the following winter to finish things off.

After quite a bit of watching of Kijiji (like Craigslist), I purchased a used but new Garrett T04E .63AR 50 trim turbo with 3 different flanges at a most excellent price along with a Turbonetics 35mm external wastegate. That, with my cloned HKS blow off valve I already had, and the purchase of a cheap cast Ebay manifold made up the kernel of the system.

Nothing like some mid 80’s technology, paired with some crappy China made knock offs to set things off in the right direction.

My only real concern was how well the Ebay cast manifold would flow and if it would hold up.I was confident everything else would work well.(well, I was almost right…)

Stage 1: Turbo install.

For a turbo designed in the 80’s, the T04E-50 trim has a pretty efficient compressor.Here is the compressor map with a number of flow points marked.
I thought I might need to go as high as 24PSI, but was not initially planning on raising the redline to 7700.
Attachment 181755

Hmm, using the wastegate mounting holes in this cast manifold, means you have the option of having the exhaust port of the wastegate shooting into the block, or into the turbo itself.So I made an adapter plate, using a 1/2" thick piece of steel.Also, a bit of interference between the turbo compressor side, and the manifold had to be ground away.
Attachment 181756

Needed to use one stud in the turbo down pipe flange since the elbow is quite tight.
Attachment 181757

Since I didn’t take any pictures of the downpipe, here is the layout.I was able to coax the 3”od exhaust tubing over the 2.5” short radius elbow, before welding.
Also, you will note that the ID of the piping steps up twice.It comes out of the turbo at 2.5”, into the elbow at 2.635” and then into the 3” pipe at 2.87”.
Not as good as a transition pipe, but not too too bad.
Attachment 181758



Attachment 181759

Had 10mmx1.25 threaded rod from a previous SC build, which I used as studs for the 4 corners of the manifold.The short radius cast stainless elbow, clears the parcel shelf easily.Attachment 181760

Had some 12v MAC valves kicking around, but needed to make a valve manifold and mount.
Attachment 181761

Built the oil in/out flanges for the turbo to attach the AN fittings to.Purchased direct from China (Ebay) the AN hoses and fittings which turned out to be a mistake.
They were very difficult to assemble, and the 45D and 90D elbows failed after 3 months.
Attachment 181762

Hard to tell, but this is a picture of the turbo 8AN drain hose and fitting.The drain hose interfered with the cooling hose, so I ended up modifying the cooling hose mount.Attachment 181763

Cut up a stainless dishwasher door for material for the turbo heat shield.It buzzed, so I removed it after a time.
Attachment 181764

Attachment 181765

From the CAT on, the exhaust is just 2.5” diameter.The CAT flows the same as a 2.5” pipe, so both the CAT and exhaust would need to be replaced to remove this restriction.
So far, I have not found a CAT that will flow close to what a 3” pipe will, so have not figured out what to do long term.
Attachment 181766



Two tools I found useful.
1.If you buy this manifold, do yourself a favour and grind down a 6 point socket, so you can use a ratchet for every nut holding the manifold to the engine.
2.This band clamp was used to fabricate the down pipe.Use the clamp to hold the 2 pipes that need to be welded in the correct position.
Remove the pipe from the car, and tack weld it thru the holes in the clamp.Remove the clamp and test.Then fully weld the joint.Step and repeat.Attachment 181767

Next up: Fuel, spark and wastegate PID tuning, and numbers.

There seems to be a lot of discussion on twin charging and compounding lately. It's interesting.

I will be paying attention.

There has been hasnt there. The more I think about it the more I think rocket anti-lag would be easier to do than any sort of successful twin charging system. Rocket anti lag is actually less harsh on the turbo than the normal exhaust gases so you could just have it running all the time.

I was absolutely thrilled with how the v1 prototype of my system worked out. So much so, that if it hadn't been for excessive blow by on #1, I probably would have stuck with it. For my driving style the compound is/was awesome. I am really excited about getting the v2 on the road. Conservative estimates should put me at 240+ lbft under 3K RPM. Never will be a dyno queen champion, but a freakin kick in the pants drive to and from work.

LOL. I read this earlier, and still smile whenever I think about a rocket being used to drive the turbo. Would you suggest using an afterburner?

Gas Jet Turbine anti-lag just doesnt quite roll off the tongue as well even though its more accurate.

Turbo tune and Phase 2:
After getting the car back onto the road, and getting a rough tune in, I was disappointed to find that the spring in the wastegate was yielding only 6psi.
Attempts to increase this using the EBC in megasquirt resulted in either massive overboost, or wild oscillations.

I was using this procedure for dialling in the PID:

“In my experience with closed loop boost control, I found that you need to lower the P term until you have about 10-15 kPa initial overshoot before trying to tune the I term.Then, add some I and add some P. Each time you increase the I term, increase the P term with about 20% of the increase of I term to keep the system stable Do not touch the D term until you can at least have a kind of flat boost duty. Add some D only to reduce the initial overshoot.”

Another option was to use a higher boost base spring, but I couldn’t find anyone selling anything for this older style unit.
I purchased (then returned) a 15psi spring for a Tial unit, but it would not work.
Attachment 181718



I then found a post with the following suggestion:
“Then I realized that LOWERING P reduced the oscillation.Of course this would result in massive over boost. But instead of following the manual again, I decided to add D to reduce overboost while leaving I at zero. So I'd increase D and then not reach my target, then I'd lower P again which results in more over-boost. More D to get rid of the over boost, and so on.”
Following this procedure allowed me to dial in the wastegate with reasonable success.

During the summer I ran a few autocrosses and did a few upgrades.

At times the turbo sounded like it needed a larger blow off valve, so I purchased a new unit from a BRZ owner who put on a turbo and claimed they sent him 2 valves.
I used aluminum brazing rod to attach this to the turbo outlet pipe.
Attachment 181719

The silicone 90D hose coming out of the turbo was hitting the hood, so I replaced it with a 2” tight radius aluminum cast elbow.
Again I used the aluminum brazing rod but, needed to buy a second torch to get the necessary heat into the compressor housing.
Attachment 181720

At the end of the season, the car was running fairly well at 21psi, so I went to the drags.
Couldn’t get the car to hook up, but did get a better trap speed than I was able to achieve with the supercharger (117 vs 109).
Actually the day was full of fail, as I repeatably hit the rev limiter and on occasion shifted from 2nd to 5th.
Attachment 181721

There was a Honda hybrid at the drags!
Attachment 181722



Attachment 181723

Ran a 4th gear pull while at the drags, to get a data log for virtual dyno, on known flat ground.
I have quite a bit of work to do, in order to hit my target high end power with the supercharger sucking about 20hp (estimated) at 7000RPM.
Spool hurters:
Honda intake manifold, 2.5” exhaust, China cast exhaust manifold, Big sleeve bearing turbo.
Power hurters:2.5” exhaust, China cast exhaust manifold
Attachment 181724
Here is my timing map (94 octane pump)
Attachment 181725

I must have been delusional in thinking this entire project could be done for just $2k.Just for the turbo I am already at 1.2K
Attachment 181726

Aluminum Brazing:In the past, I have tried a number of Brazing rods for aluminum.
Frankly, I have been disappointed with them all.Usually they are very difficult to use, and require special technique to achieve acceptable results.
I am very happy to say that this rod changes everything.It is like soldering.Yes, that easy.
Only thing, is that it does not flow into a joint like solder.
To resolve that, I would apply the filler rod to both pieces first, and then mate them and apply heat.
Then use more filler rod to smooth out the joint. (Check out youtube for videos)
Rod = Benzomatic AL-3 (but other companies make this too)
(Apparently the plastic on these torches can melt, which is why I have the heat shielding on both torches)
Attachment 181727

Next up:Y-Pipe from SC to Turbo

Note that many of the parts that are on the upcoming pages were built in stages, in some cases over several months.
Rather than keep this chronological, I decided to cover each part from start to finish in one post.
Due to this, you will notice discontinuity in some of the photos.

So this build will have 2 electronic throttle bodies in it.
One at the inlet to the supercharger, and one at the inlet of the turbo, on a Y pipe.The one connected to the Y pipe, will have just 2 positions, open or closed.

These ETB’s usually have a return spring in them, which returns them to a nearly closed position (they remain partially open, to support limp home mode if there is a failure).
One ETB, for the Maxima, has a set screw on the outside of the throttle body which would allow you to change the return position to fully closed.
This, and the fact that this throttle inlet pipe is just a hair over 3” made it perfect for this application.

After picking up one of these from a local wrecker, I found that this adjustment screw was seized. :bang:
So had to take it apart, and grind down the lower post (upper post sets full throttle position).This all worked out ok, it just took longer than expected.Attachment 181654

I needed both ends of this throttle body to connect to silicone hoses, so I machined up a plate to attach to the end of the ETB that would normally attach to the manifold.
Attachment 181655

I need to attach this plate to a short piece of 3” pipe, so brazed it.Here is a close up of the brazed seam between the plate and the aluminum pipe.Attachment 181656

Size comparison of the Volvo valve compared to the Maxima valve.
Remember that the Maxima valve can be in any orientation/position which makes it much easier to fit under the hood.Attachment 181657

So next I needed a Y pipe to connect the supercharger outlet to the inlet of the turbo, and the above valve.
I initially looked around on ebay and such, looking for something that would work, but after I got the turbo installed, I realized that I would need to make something.
The space was tight, so I decided to just modify a silicone coupler.I have modified couplers before, but not to this extent.Marking the cutting location on 3” 90D elbowAttachment 181658
So I started off the hose, with a base of black silicone fusing tape, followed by layers of fibreglass tape and bonding silicone
and finally another layer of black silicone fusing tape.
I built it on an aluminum pipe with oil on it, so the manufactured hose would not stick to the pipe.I really like the Permatex silicone gasket maker.
. Attachment 181659

When you put a layer of silicone on the hose, and then wrap it with the fibreglass, the silicone permeates the fibreglass, creating a strong material.
Attachment 181660

Attachment 181661

After building this up to this point, I found that the silicone fusing tape really didn’t want to let go of the aluminum pipe, so decided to build the pipe right into the unit.

Attachment 181662




Completed Y pipe
Attachment 181663
After a bit of paint to make things look finished.
Attachment 181664

Supercharger

I didn’t take long for me to select the supercharger I wanted to use.Since the supercharger was going to “freewheel” at high RPM, I couldn’t use a screw type that compresses the air, because it would have high parasitic losses.
That really left the roots, and I knew I could get pretty good results with a MP62.
I was planning on building an intake manifold, and then having a plate which the supercharger would mount to, so I really wanted to have a supercharger designed to bolt to a manifold.
There had to be plenty on the used market, and if they were reasonably priced it would be a bonus.

The cobalt supercharger, found on 2005 vintage vehicles met these criteria, however the unit itself was a bit long.
The front of the supercharger was not a problem, because someone in my club gave me the nose off a BRP supercharger that had failed (Thanks Dave).This left the rear of the charger.
I decided to buy one to see what could be done.Right now, these chargers in my area on Car-Part.com (a site for searching wreckers for parts including pricing) are under $200us,
with ~70k miles on them.
Stock internet picture of a Cobalt Supercharger
Attachment 181610

First thing I did after getting and inspecting the charger, was cut 3” off the intake end.
I thought I would be able to get that to barely fit into the available space, but I couldn’t figure out how I would connect the bypass valve, which comes out the bottom of the supercharger.

Since I still had the separate bypass valve I used in the M90 project, I decided to cut a further 3” off, removing the bypass valve, which left about .8” of overhang, past the rear bearings on the supercharger.Attachment 181611

I needed to make an adapter, to connect from this cut off end, to the throttle body.

I was fortunate to source a piece of cored aluminum tubing5.125”od, 3.25”id, 2.75” long on EBAY, which I modified to fit over the end of the supercharger.
I did have to do some minor modifications to this area on the supercharger, and I filled in the area between the 2 rear bearings with epoxy steel,
but figured if this supercharger failed, I could modify a second unit in a reasonable time with hand tools.
Attachment 181612

I drilled and tapped 3 holes for screws, but the main thing that would be holding this together would be silicone.
Attachment 181613



Attachment 181614

By the end of the summer, I had this adapter, as well as the tensioner started, and had reduced the size of the bypass valveand a Chrysler 80mm ETB that I had from an earlier project.Attachment 181615

After locking down a number of other items, I had determined where the bypass valve would go, and how much I could shave off the aluminum adapterAttachment 181616

Machining a slot for the o-ring gasket.
Attachment 181617



Attachment 181618

Hmm, doesn’t exactly flow nicely from the throttle body into the supercharger.Maybe that is a project for next year.
Attachment 181619

Bypass valve location (also, notice I had to add back in a ¼” spacer to the throttle body due to clearance issues)
Attachment 181620

With valve installed (ok 1 screw)
Attachment 181621

Supercharger, pretty much ready for installation
Attachment 181622

So I ran into an issue with the 4 bolts which mount the supercharger to the base plate.
Experience has taught me to always try to pack things in when you are not sure how things are going to ultimately fit.

I decided to position the supercharger as close to the engine as possible (which turned out to be the right decision), however half way through,
I discovered that I would not be able to get a wrench onto the bolt at the rear of the supercharger, closest to the engine due to interference with the injectors.

This was rather late in the game, so I decided to machine down the leg the bolt goes through and tap it for a steel threaded insert.
I will make a small L shaped plate which will attach to this spot, and a future mounting boss that I will put on the manifold plate.

So much for having a mostly stock supercharger that would be easy to swap with a replacement..
Attachment 181623

I picked up a 150mm crank pulley from FFS and a 62.5mm SC pulley from a local Miata owner.
I will re-use the tensioner used in my last build, and fabricate a tensioner bracket when I know what I need.

I still need to figure out how to get cold air to the inlet of the supercharger, but most of the heavy lifting on this assembly is complete.

So also during the summer, I started working on the intake manifold.
I measured where I thought things would go, under the hood, and then used a spare head to do the details.
Since this manifold would also be supporting the supercharger, and I don’t have access to aluminum welding equipment, I decided to make it out of stainless.
I did build a header earlier out of stainless, and although it was a pain it was something I was familiar with.
So I ordered some schedule 40 tubing for the runners as well as some standard thickness material for the other parts.

First up was trying to flute the runners.I made a mandrel with the intention of heating up the stainless and pounding it with a hammer.
I intended on doing this with the schedule 40 material, but that was impossible! I could not bend the material.
So I ended up bending some standard thickness stainless, and then machining the schedule 40 material slightly so the thinner material would slide over.
I then bevelled the end of the schedule 40 material, so the air flow would be somewhat “normal”

Sorry for the focus on this one (mandrel on LHS, bent piece on right)
Attachment 181458



Attachment 181459

I bent the end of the schedule 40 tubing that goes into the manifold flange with this, in a hydraulic press.Attachment 181460

Internal manifold pic Not sure I fluted the ends enough, however probably better than nothing.Attachment 181461

After tack welding
Attachment 181462

I was mig welding this with the incorrect gas, which is one reason why the welds look horrible.
The other reason is, well my welding skills are not very refined :).I realize that welding with the wrong gas can cause everything from stress cracking to rusting,
however I didn’t suffer any consequences on the header, so am assuming thingswill work out.

Machining the flange flat.
Attachment 181463

The runner length on this manifold is probably well suited for an engine that turns 13000 rpm, however it’s main purposeis to support the supercharger
and not take up much room, so this was a compromise I had to take.

Time to try it out!Well, I was assuming that I would be mounting the throttle body somewhere near the front of the intake manifoldand I was hoping the IAC
would be on the bottom of the throttle body (the normal spot),but after positioning the supercharger, I realized there was no place for the throttle body
anywhere near I thought it would go.

So I cut off the tack welded on throttle body flange, and considered my options.
Attachment 181464

Expected operation
 

This is how I expect the turbo to spool with the supercharger sharing the work.
Attachment 181457

For this example, let’s assume that the supercharger is geared to produce 15psi of manifold boost, and the electronic waste-gate control on the turbo is controlled to 22psi of manifold boost maximum.

Let’s consider what will happen with regard to boost measurements from 2 locations.
“Manifold boost”, which is the boost pressure at the inlet of the engine, and is used to calculate required fuel, and
“supercharger boost”, which is the boost pressure measured at the output of the supercharger (and input to turbo).
You will notice in the diagram, that both these boost pressures are being monitored by the MS computer.

Operation
At 2000rpm while cruising, you suddenly floor it. ETB2 is closed.
The turbo is barely rotating, and suddenly the supercharger is providing a bunch of air.
The “manifold boost” will now be 15psi, and depending on the restriction the impeller of the turbocharger is making, the “supercharger boost” will be slightly higher (guessing 15-17psi)

At 3000rpm, some time has passed and the turbo is starting to spool.
Let’s suppose that it is doing half of the work. The “manifold boost” will still be 15psi, and “supercharger boost” will be 7.5psi. ETB2 is closed.

At 3900rpm, the turbo is still not fully spooled, but is moving the same amount of air that the supercharger is moving.
The “manifold boost” will now still be 15psi, and “supercharger boost” will be 0psi.
ETB2 is closed.

At 4000rpm, the turbo is still not fully spooled, but wants to generate 16psi of “manifold boost”.
It is sucking more air that the supercharger can provide at 0psi output, so the “supercharger boost” is now -1psi.
ETB2 now needs to be opened, and air from second inlet is introduced which allows "manifold boost" to go to 16psi.
Not entirely sure what will be measured at the "manifold boost" point when ETB2 is still closed and the turbo is trying to pull this extra air.
I expect that the turbo will be able to exceed the 15psi that the supercharger normally provides, but not sure by how much.

At 4300rpm the turbo is fully spooled at 22psi, and ETB needs to remain open until an upshift or throttle off.

The supercharger is always moving air, but above 4000rpm in the above example, it is really like an inefficient fan, moving air from one spot to another.
It will use a lot less power when in this mode though.

So in order to control ETB2, the electronics needs to monitor.
“Supercharger Boost”
“Manifold boost”
“clutch in/out”

some of the electronic logic will probably be.
If clutch is in, then ETB2=closed
If “Manifold boost”>16psi, then ETB2=open
maybe
if “supercharger boost” <0psi and “manifold boost”>16psi, then ETB2=open (with hysteresis on the “supercharger boost” input.
This will require some experimentation, once things are together.

There were not a lot of options for an inlet to the intake manifold.
I considered adding another tapered plenum in parallel with the main plenum, but that would interfere with the manifold support arm and looked like a lot of work.
I considered coming off the bottom of the manifold and having the throttle body somewhere there, but that was just too impractical.
I ended up using a tight radius stainless bend, between the supercharger and throttle body.

It just barely fit!

Attachment 181447



Attachment 181448



Attachment 181449



Attachment 181450



Attachment 181451

Also needed to find a new home for the IAC valve.
I decided to use the stock 94 valve, and reused a plate I had made for the honda manifold.Attachment 181452



Attachment 181453

Had to reposition the hose connection. Used JB weld to seal the top.
Attachment 181454



Attachment 181455

Time for a random autocross picture.Attachment 181456

Whoaaaaaaaa what a sweat read. I'm totally subscribing to this one.

:party:

How to control an ETB
 

Thanks man!
Still quite a bit of work to do, and I really need to get this on the road my mid April.
If I can do that it would give me a full month to debug this before any events.

Connecting and controlling an ETB (Electronic throttle body)
If you’re working on a project and need an electronic valve or throttle body, automotive electronic throttle bodies are not difficult to control.

Here are the steps:
1.Purchase a throttle body of the correct size.
2.If the throttle body has a return spring, open up the housing, and cut it out.(I use a dremel and a grinding wheel,
since space is limited and the spring is like an oversized clock spring).
3.Buy a JRK21v3 brushed motor controller
4.Connect it as shown below
5.Download software, and connect USB cable.
6.Set variables as shown below in shots 1-4
7.Read the website so you have an idea of what the JRK is capable of.
8. Power it up with a low voltage (5v), since you may have the polarity on the motor, or the feedback backwards.
9.Correct the polarity in software, and then calibrate the feedback loop (same as you would for the TPS on MS1-3)
10.Have fun!

The throttle body has 2 feedback wipers (for redundancy).You only need 1.
You need 5 wires going to the throttle body, 2 wires for power, and 2 wires for control voltage input(0-5v).
Attachment 181439

Get the JRK21v3 here.(no affiliation)
https://www.pololu.com/product/1392

Attachment 181440

This page is for selecting the feedback signal type.You need to use analog. Learn function allows you to program the fully closed and open positions of the throttle body.
Attachment 181441

The scaling is programmable , see the learn function, and the output does not have to be linear (but you probably want it that way.)
Attachment 181442


I have used these PID settings for 3 different throttle bodies with good success.
Attachment 181443

Set everything to max on this screen, including current.(current is limited inside the IC to 5A)
Attachment 181444

In order to get the supercharger to sit as close as possible to the engine, the front left mounting bolt would have to co-exist with my fuel system.
So, I re-routed the fuel lines, and fuel injector wires, to run on top of the fuel rail.

Attachment 180954

After welding the supports on the manifold, I cut the main supercharger plate, and then levelled it using a dial gauge on the mill.
I had problems in my last set up, getting the belt aligned, which I don’t want to repeat.
Initially, I was going to mount the supercharger on a 1” plate, but after I found I had clearance, and that I had very little for the outlet, I decided to add an additional ½” to it.
Attachment 180955



Attachment 180956



Attachment 180957
I went a little overboard, with the amount of fasteners holding the upper to lower plate.

Attachment 180958

Since I don’t have an aluminum welder, and the pipe to connect the supercharger mounting plate to the outlet pipe would need to start off “L” shaped,
and avoid various pieces (manifold, alternater etc) I ended up getting 1” thick aluminum plates, and cutting them into the correct shape.
I used styrofoam, to get close to the correct shape and then duplicate it.
The plates are bolted one after another to each other.It worked out ok, but was a lot of work.

Attachment 180959



Attachment 180960

Not much space below the supercharger, to route the charge pipes.

Attachment 180961

The outlet port is a weird shape, but I only have 1.6" between the supercharger belt, and front cover of the engine, so needed to get creative.

Attachment 180962


This location for the tensioner, was found to not work. I couldn't get a ratchet on the tensioner to install the belt.
Attachment 180963



Throttle body

Unfortunately, there was not enough space to mount the previously installed 70mm Honda throttle body.
I had to go with the stock unit, and had to machine the body down considerably.
Made a bracket, base plate and mounted it to the supercharger plate.
There was enough room to bring the 2.5” od piping right back to the intercooler.

Attachment 180964

Throttle body is pretty close to the engine bay walls, but I should have enough clearance there.

Attachment 180965



Bypass hoses nearly sorted out.

Attachment 180966



Exhaust system

With my previous supercharger system, I was running a custom header, and a 2.5” exhaust.
The exhaust consisted of a 200cell carsound cat, a magnaflow 4x22” round resonator and then a 5x11x22” magnaflow main muffler.
These were the largest well flowing components I could find, and were needed to get the car to be reasonable sounding.
When I put the turbo on,I installed a 3” down pipe, and 3” into the cat.The exhaust was incredibly quiet.Like a Buick.In fact, there was no exhaust note at all.
Since the 2.5” exhaust is hurting spool and flow, I decided topick up the same size magnaflow muffler in 3” and some mandrel bent tubing to connect things.
I had a left over 4x18” round resonator in 3” that I had installed at one point which I also installed.

So now I am running 3” front to back.I forgot how much I hate doing exhaust work.

Attachment 180967



Attachment 180968

Tensioner bracket etc is now complete but sI till have quite a number of things to do. The 2 air cleaners is a temporary setup.
Currently I am implementing a single air cleaner solution.

Attachment 180969

Tensioner location

Attachment 180970

I can't believe no one else is commenting on this. I am very entertained by this build, it is very unique.

It's an awesome build, I've been following it closely. I can't wait to see it finished, and see datalogs/dyno plots/time slips/ and driving impressions. This thing is gonna be sweet.

This is absolutely fucking insane. Props.

thanks, hopefully it will be worth the trouble.

thanks Pat. I am very interested in seeing how this thing works, and yes I will be fully transparent, good or bad.

Need some humor. Link to Australian deck stain commercial. (I doubt it's real)

So I spent the last couple of days, finishing off the pipe from the supercharger to the turbo, as well as the piping for the single air cleaner.(ok,
and a bunch of little things)
The pipe leaving the supercharger is oval, since I have very little clearance between the front cover and the supercharger belt.
Even so, I ended up cutting half of the front cover off, to get more clearance.

This component is part of the supercharger mounting, so it needed an o-ring gasket to allow for easy installation of the outlet pipe.
I thought it would be difficult to machine this shape, but it was no problem really.
Attachment 180879

The part below with the brown o-ring, mounts to the supercharger mounting plate assembly.
The other components connect the supercharger mounting plate, to the turbo inlet hose.
I am planning on measuring the temperature of the supercharger outlet, hence the sensor.

Attachment 180880



Attachment 180881

There may be an issue with intake noise.
When the turbo is fully spooling, the ETB2 opens which lets additional air in to the turbo inlet.

If you have ever had a silicone hose pop off on the pressurized side in a supercharged car, you know that the supercharger makes
a lot of noise when moving air. It can be loud and it's not a pleasing sound.

Not sure how bad this will be in this case, as all the air coming out of the supercharger is being gobbled up by the turbo. Maybe not that
much sound will actually be coming out . Anyway, I decided to mount the air cleaner under the fender which will give me cool air
and move any noise further away from the cockpit.

Quite a collection of pipes and silicone couplers, not to mention lots and lots of hose clamps.
Attachment 180882



A look at under the fender.



Attachment 180883

Not sure how long this cover up treatment will last.

Attachment 180884



Current under hood shot. Honestly I am surprised at how easy this is to work on. There is room to access all the fasteners, and
I can remove individual components pretty easily. I am pretty happy with the way this is going from an install point of view.

Attachment 180885

I had a huge setback with the tensioner bracket.I lost it.
I was test fitting it with the tensioner, and after doing that, I removed the tensioner, but forgot to remove the bracket.
The bolts were on finger tight and the bracket violently fell off while I was testing boost control on the highway.
Spent a good amount of time looking for it, but it went off into the grass beside the highway so it’s gone.
I was hoping to go to an autocross tomorrow(turbo only), but the boost control is not working properly (I upgraded to a 4 way valve and now the boost is oscillating badly)
and I don’t feel confident in the car right now.Got some wiring, computer work and the tensioner bracket left to do. Getting closer....

Yeah, when I get this close it will probably be 24-7, vacation from work till done.

.

Thanks Art, I hope so too!

Yes, it's hard to sleep, when your mind doesn't want to shut off.


Anyway, here is a video from the drags last year.
No traction, because the tires were picking up rubber. Should have done burnouts before each run.
Normally, I rarely get wheel spin in 3rd (unless the tires/temp are cold).

You Tube

Ok, new tensioner, but maybe not as good as the last one.
When installing the belt, the belt seems to jam on the edges of the bracket. Once it's on, it's golden.

Attachment 180876

Now just have to wire in the additional temp sensor, and supercharger bypass valve and get the MS programmed for these 2 items.
Before the supercharger belt gets installed, I need to fix boost control, which is now out of control. The target in the graph below, is 200kpa!
All with settings that worked fine last year.

Attachment 180877

So I think you changed the exhaust, did you change anything else? It looks to me like you have closed loop activating before full spool and then too much P. I can maybe help you with this offline if you would like.

Post log and tune

Changes were exhaust, and a change from a 3 to 4 way valve. Intake manifold changed too, but I am not sure that would have that much of an effect.

Thanks, posted.

Any suggestions are appreciated. You will note this tune is pretty rich. I added quite a lot of fuel after putting on the larger exhaust, and have not had a chance to pull any.

The 4 way valve, done the only way that makes it worth it makes it much more difficult to have a smooth boost line.

This is what EWGs are for. :)

--Ian

Uh. My boost is quite a straight line. 3psi spring. Dual port wastegate. 4 port valve.

Take a look at this and perhaps give it a shot for boost control. Ideally post a log with this so we can see if it's any better or worse than before.

Man, I am so tired and sore. I need a day off to recover from the weekend!

I have heard from others who have twin charged their car, that boost control is a challenge. I don't quite understand why.

Pat -thanks for the file. I probably won't have the car back on the road till Wednesday for turbo only testing.
I need to make sure the electronics works perfectly out of the car first.

In my case, there are two control loops for regulating manifold pressure, and they are nested. With the limitations of the MS2, these control loops were not synchronized. Basically, I was running an independent loop wrapped around the MS2 loop. The two loops interact, and we have no plant normalization or gain scheduling hooks. The system has operating points where it is purely SC, others where it is purely TC, and then regions where it compounds (both TC and SC).

I don't think you will run into the same challenges with the architecture of your system. I regulate both the SC PR and the TC PR dynamically. ~I think~ your setup will allow for a set-it forget-it on the SC. Once the TC flow reaches a point where SC flow = TC flow you open your huge bypass (the TB) and then control with TC WG. The compound is pretty much handled automatically for you. I ~almost~ adopted this architecture with the version I am building now. Very compelling.

Pat
Got things back together tonight and loaded in these boost control setting. Logs attached.
With boost target set to 200KPI, boost runs straight up to 240KPA (4rth gear pull), which is the current over boost setting.
I also tried reducing the P with my previous set up, but probably reduced it too much (it overshot target by 20kpa, at which point I lifted). (didn't have much time, so need to hit this again tomorrow)


Ted
The people who told me boost control was a challenge when twin charging, were running the same set up as I am running.
I agree with you... Your setup is far more challenging which is one of the reasons I chose to go the simpler route.

Try this if you want. You can bump your overboost protection down a bit if needed for safety if you're worried about that.

The log you tried the new code on, vs your first log, you were spooling the turbo in a low gear so Revs were climbing faster, which is good. Based on how it responded, I doubled the P term, raised the I term some, and left the D term alone. That should result in it catching the boost control before hitting overboost, and once it does that we can see how it settles and go from there.

So for some reason I can't open your log in MLV, I am sure I am doing something wrong ...

Have you characterized the open loop response of the setup yet? That is where I would start. Take a series of pulls (in the same gear) at different fixed duty cycles and see what you get. Start from the bottom (lowest boost) and work up. Plot each curve MAP vs RPM in excel or MATLAB or whatever.

Pat. Unfortunately it still hits the over boost pretty hard.
I do have fixed duty running at about 220kpa now. I think I will leave it ~there for a few days while I get the SC running.

While setting up the ETB on the supercharger, I found the 5v going to the TPS, is not really 5v (it drops under load), which
I still need to diagnose.
I also popped off one of the turbo hoses, after one of the over boost spikes. -It was not on tight enough.

I would start running the D term up now until it stops the overshoot for the most part. Once it does that, you can run the I term up if it's not setting at the right value fast enough, but that will likely require you to lower the D term a bit as you raise the I term. Your solenoid system is very good at causing a change in the system, so the PID has to be just right or it's going to oscillate since small changes in dutycyle have a big affect.

good points, and I will get back to this, but I have been impatient (see below) :)

SUCCESS!
 

So I had a few teething problems out of the gate.
First off, I somehow blew a relay and transistor on the ETB1 controller board (a MS1).
Repaired that and after installation, decided to do a number of runs with just the turbo, using a fixed duty cycle on the boost control variable.
I could only get 6psi boost, regardless of the value I put in.
It looked like everything should work, but it didn’t.
So I decided to install the supercharger belt anyway.

Only issue I had was minor belt interference, which I fixed (sort of).
Then figured that maybe the boost control was not working, because the EBC valve was getting too hot.
I moved the valve and I was back in business (coincidence maybe?).

Anyway, here is a datalog of a 5th gear pull from 1600 to 3600rpm. (note that MAP2, is measured at Turbo inlet and MAP is at intake manifold)

Attachment 180839

Did some further pulls,(up to 4600rpm) and put together this spreadsheet.
Attachment 180840

So pretty much what I was expecting, except the low rpm total boost is higher than I expected.
You can see the supercharger is not really doing that much work once the turbo has started spooling up.
I was counting on that, since I am driving the supercharger pretty hard, and if it is generating much boost for long,
it’s not going to like it (I am using a 150/58 pulley ratio)

I can understand the boost being a bit higher than traditional supercharger setups, since there is more exhaust back pressure
and the supercharger VE does go up, when it has lower output boost.Maybe that accounts for it.

Here is a transient response (I’m still being a little gentle with the throttle).
You can see the boost before the turbocharger, is about 2 psi higher than manifold, (at blue vertical line)
until the turbo begins to spool, at which point this reverses.

Attachment 180841

So overall I am quite happy.I spent quite a bit of time, making sure the supercharger belt would line up,
and it does and seems to be rock solid.

I still have a bunch of things to do including:
-EBC, ETB1 and accel tuning
.-SC output temperature and ETB2 switching are not working properly.
-ETB1 position is not being displayed properly, which is making it difficult to tune this throttle.
-still minor belt interference (belt seems to move more as RPM is increased)
-other things I have forgotten about.

Biggest questions:
-how bad will the noise be when ETB1 opens?
-what will power numbers be?

We have a big storm coming in tonight, so I doubt I will get any test time in tomorrow.

Looking good! That thing is making some healthy boost numbers down low. And the turbo is lighting off nicely with the SC assisting it in the mass flow department.

Couple questions, although i know you said some stuff isn't being datalogged right now but I'm mainly curious how you plan to tune it.

What does the ETB look like on your excel graph? I see the SC boost tappers off to zero. Is the ETB gradually tapering?

I would assume if the controls allowed, the best case would be something like:

If boost less than target minus 2 PSI, SC boost = all of it.

If boost between (target - 2 PSI) and (target - 0.5 PSI), interpolate the ETBs position between open/close and also compensate for the non-linearity of flow vs throttle angle so it's a mostly linear process of duty to flow.

If boost above (target - 0.5 PSI) , all turbo.

As for power, I would guess this will be good for 300whp if not more once it's tuned.

The SC boost tapering off, is just a function of how much air the turbo is pulling.
As the rpm increases, the turbo spools harder, which draws more air from the SC lowering the boost it sees.

The SC is only bypassed, when it's the boost at it's output drops below ~95KPA. (and manifold boost is greater than 210KPA)
At that point, ETB2 opens, opening a second path for air to get to the Turbo inlet.
Here are the settings. So ETB2 is only open, or closed.

Attachment 180838

ETB1 is just used as a secondary throttle. I could just use 1 throttle body, but I would have lots of idle issues and having just 1 large throttle
body on the supercharger inlet tends to give you an on/off throttle response. Very difficult to modulate.

Yeah baby YEAH!

Made a case to mount the MS2 and the throttle body controller.
Starting from the RHS of the picture, I have a little PWM board and power resistor, which are to fine tune the current going to ETB2.
If I apply a full 13.6v to the ETB2, I get a little over 5A of current, which is too much on a long term basis.
In the center is a board which is basically a Megasquirt 1, which is controlling ETB1.
On the LHS I have a Megasquirt 2, on a custom board, with a barnacled on secondary Map sensor, which controls the engine.

Attachment 180831
Spent a fair amount of time, getting the center board working properly with ETB1.
I had forgotten that I had set the current limiting to 1A, which was making the ETB very slow and unreliable.
While trying to debug this, I changed a bunch of other settings (I had not documented this board very well) and ended up breaking the set up,
so it started behaving even more erratically.

Eventually got it sorted though, andI have it dialed in very roughly.
In order to improve drivability, I added this 1 way valve and electronic switch.
The problem I was having is that the supercharger bypass valve, would tend to close with small throttle applications, causing noise and surge.
This combination of parts, holds the bypass open, until I open the throttle more than 45%.
The engine will build boost with the bypass held open, just not that much.

Attachment 180832

After getting ETB1 sorted out, I did a number of additional pulls in different gears.
I made an error -my previously stated boost levels were in 6th gear, not 5th as reported.
New numbers are:
Attachment 180833
Some other issues that are resolved/answered:

Noise when bypass valve ETB2 is opened.
Fortunately, the supercharger only makes noise through ETB2 (and a lot of it), when the inlet to the supercharger is at part throttle.
At more than ½ throttle, you cannot hear any noise out of ETB2.

ETB2 is working properly.I was just not patient enough to wait for it to switch on, and as mentioned you can’t hear anything when it is opened at speed.

The boost before the turbo, is never higher than after the turbo, so the turbo itself is never acting as a restriction.(This is good)

I made clearance for the supercharger belt.Maybe even enough.

Still need to tune ETB1, EBC and acceleration enrichment more, but things are much better now, then they were a couple of days ago.

Another issue is throttle response.It is taking about .3 seconds for SC boost to build to its maximum.
With my previous system, IIRC it took about half this time.I need to figure out why.
Still lots of things left to do.
Latest underhood picture
Attachment 180834

I broke the Turbo
 

Pulled a bit of a bonehead move.
Disconnected the supercharger belt, to do some turbo only pulls, with fixed duty cycle on EBC.
I forgot to flip the switch, that opens ETB2, which means the turbo had to pull all it's inlet air, through the supercharger.

This caused the turbo to pull vacuum at it's inlet, and overrev (probably).
I measured 50kpa on the inlet and the turbo would not reach full boost.

After realizing the issue, and flipping the switch, the turbo would still not develop full boost.
Then it would.

Noticed that the turbo had pulled a lot of oil into the intake, and then I looked at the data logs, which confirmed everything.
The compressor also had more up/down play than I was expecting, so I decided to open the turbo up.

The bearing on the turbine side had been overheated. Surprisingly, it measures good, as does the turbine shaft, and
the spots where the sleeve bearings mount. (all measured within .0001 to .0003 of normal spec). The bearings themselves
have a few scratches in them, but the shaft and bearing housing look and feel really good.

Anyway, I do notice a bit of bluing on the shaft, between where the 2 sleeve bearings mount. (the area with the smaller diameter)
Hard to see, but below is a picture, with the bearings in their correct relative position.
Attachment 180801

I have no experience with turbos. Do I need to be worried about anything here, or should I just get the turbo rebalanced,
install new bearings and go?

thanks for your input..

Ended up getting a rebuild kit, and having the compressor/turbine rebalanced, because of a minor amount of foreign object damage (FOD).

Here is the paperwork that came with the rebalance. Not sure exactly what it means but it looks good :)
Attachment 180774
Anyway got things back together on Saturday, and did a bit more testing on Sunday.

I now realize, that having a partial vacuum on the inlet of the turbo, can lead to oil leakage into the inlet of the turbo.
So I spent a bunch of time adjusting the ETB1 map, so I am now maintaining 88-100KPA while at part throttle.
(still some fine tuning to do here)

Logged the temperature on the outlet of the supercharger, and saw a maximum of 225F.
This high temperature occurred after a leisurely run up through the gears, without actually going into boost.
Temperature was typically between 160-175F and when running the supercharger at full throttle I would see temperatures in the low 160's.
I was expecting to see lower temperatures than this, because the graphs I have seen indicate a rise of 150F when running 10psi and 100F when running 5psi. Oh well.

Another thing I have noticed, is that I seem to be solidly in the surge area of the compressor map. I have not noticed any
issues, so I am guessing that the standard compressor map does not apply, if you are ramming air at high speed into the compressor wheel.
I also notice I am reaching full spool a little earlier than I am without the supercharger in there (even if with just the turbo in 6th gear, and I hold the car with the brakes). Not a lot, but it is measurable.
Not sure why, and reports I have received from others, indicate to not expect this. Perhaps it is just because I have the supercharger pushing so much air.

BTW, the supercharger is effectively of moving about 21-22 psi of air (at a 0F increase in temperature from SC inlet to Intercooler outlet) when it does not have to fight any back pressure.
The measured PSI varies a bit, as the intercooler will heat soak a bit, and the temperatures rise.
Anyway, up till now I have been setting the boost control to about 22psi.
Above 4000 rpm this causes the turbo and the supercharger to pass some of the load back and forth between one another
as the EBC tries to maintain target pressure.
I probably need to use a higher boost pressure, or just go with fixed duty cycle.

On the to do list:
1. Get electronic boost control working in some fashion. (right now, no 2 runs are the same)
2. Get protection built in, so if I get partial vacuum on the inlet of the turbo while trying to deliver boost again, it shuts the system down.
3. Figure out if I can run Megatune 2.25 and Tunerstudio on the same computer at the same time (it's a pain taking 2 computers out to the car to datalog).

Out of curiosity, why wouldn't you expect the turbo to spool earlier? The SC is increasing the airflow through the engine, and thus the exhaust energy available to the turbo is it not?

1 reason.

1. People who have done this report, that the turbo does not spool earlier.
My explanation for this has been:

At low rpm the supercharger is doing lots of work, and pumping additional air through the engine. Hence the turbo also does more at
low rpm than it would if there were no supercharger, due to there being more exhaust flow.
As rpm goes up, the boost (backpressure) that the supercharger is seeing goes down because the turbo is starting to spool and
is pulling air away from the outlet of the supercharger.
So the supercharger is doing less work. As the turbo reaches it's spool rpm, the supercharger does less and less, until
eventually it is not building any pressure at all. Since the turbo is doing all the work at this point, why would the spool rpm be any different,
from where there is not supercharger installed.

Again, one explanation is that even though the supercharger is not building any boost near the spool rpm of the turbo, it is pushing
a lot of air in the right direction for the turbo. Perhaps this has a measurable effect.

Regardless, it's not a huge difference, but I'll take it.

Obviously a different topology system, but I was getting a crappy 2871 churbo to spool to 14.7psi in the low 3000s (~3200 RPM IIRC) on a 1.6 with 2.25" exhaust in 3rd gear (5 speed, 4:10).

Edit: At 5280 ft (~85kpa ambient)

I would believe that adding a supercharger as you did will improve torque to the wheels, and time to torque under all transient conditions. (vs if you had the exact same turbo setup, with the SC and hardware required to plumb it and control it as you have designed/built). I would atribute this directly to the increase in mass flow through the motor from the SC being added in.

Thus with the improvement in massflow in all transients, I would also expect the turbo to spool faster*. With faster being defined as, boost at the motor would climb faster vs if you had no supercharger. For example, you're at 4K and floor it, the setup you built will result in the car getting to full boost faster vs just a turbo.

I would actually expect it to be a pretty big difference to be honest. On your car, if the turbo alone can hit say, 25 PSI @ 4,500 RPMs, then with the SC installed, I would expect it to hit full boost at 3,700-4,000 with the SC pushing more, AND, for daily driving, a lot more fun as the car can go from cruise to boost a lot faster vs having only a turbo.

That doesnt make any sense oreo, the supercharger should lower the boost threshold for the turbo on that engine. Increasing the mass flow through the engine will increase the amount of shaft power the turbine will generate. Essentially pushing a blower at 15psi through a 1.8L should give the turbo a boost threshold similar to what it would have on a 3.6L engine. Now why you don't notice it is in the handoff of boost between the blower an the turbo. If you're already making 15psi with the blower the boost pressure considered the boost threshold for the turbo just went from 0psig to 15psig.

The problem is it doesn't get double the airflow with a 15 PSI pulley as in your example. It does before the turbo tries to spool, but as soon as the turbo tries to spool, the SC acts as a restictor that is RPM dependent. It spins X turns relative to engine speed, and displaces Y volume of air per rev. If the turbo tries to spool up and push more air, the SC won't let it. If the turbo kept spinning up forever, eventually you would pull a vacuum on the outlet of the SC. In his case he actually does that, but then opens up a throttle body to let air go to the turbo.

If he swapped the plumbing of the turbo and SC (air filter, turbo, SC, intercooler, engine) then the motor IS getting double the airflow with a 15 PSI pulley all the time. So if the turbo supplies 5 PSI of boost out of the turbo, the SC does double the density of that and throw it to the motor.

So essentially his setup, you're reducing transient response a lot, but the turbo spool improvement won't be what you would get with the arrangement I just described in a compound fashion.

Pat, mine is configured as you described (turbo-super) and I know the turbo spools faster, by a lot. I think that it should still spool faster in oreo's set-up by the "gain" characteristic associated with the turbine/compressor relationship in the turbo. Even with the handoff (which I also do), once you get the turbo going, it takes off progressively.

Yes, I am seeing improved time to torque and improved torque at low rpm. I would expect slightly lower torque vs turbo alone at high rpm, due to SC losses.
Yes, I am seeing this.
Yes, the car goes from cruise to boost a lot faster, but I am only noticing a minor improvement in spool rpm. Note that I am not comparing spool in the same gear. For example, in 3rd gear the turbo probably spools at about 5000rpm or so without the supercharger, while it's much lower than that with the supercharger installed. Having said that, if I slowly accelerate to get what I would call a minimum turbo spool rpm (6th gear, with me slowly allowing the car to accelerate using the brakes, to get the time unlimited spool rpm), it is only slightly higher than the rpm I am getting twin charged.

I think Pat is doing a much better job of describing how this works. Although this is twin charged, it is not compound boosted. In my case (no E85, so limited power capability) I did not feel that the added
complexity of going compound boosted, would yield that much. Still need to measure power levels once I have things dialed in further to know for sure, but so far I am liking it.