A random thought about twincharging...
 

Back when I had my AW11 MR2, I remember that the supercharger had a magnetic clutch to turn the whole thing on or off. I'm thinking that in a twincharged setup, we could do something like run the supercharger up until around 6 or 7 PSI, at which point the turbo would take over and we could simply turn off the supercharger.

The setup would probably require one-way check valves on the output pipes of both the supercharger and the turbo, to prevent positive boost from one system from entering the other system. I've also thought about something like this instead:

https://www.miataturbo.net/attachmen...ine=1333400308

edit: the last image should be turbo < super PSI, lol.

Basically the bypass flap would prevent the turbo as well as the supercharger from seeing positive displacement from the other system.

Anyways, this all came about because I realized how much extra room I'd have in the engine bay after dropping AC and PS... just something fun to think about.

What do you guys think?

You and Falcone need to get together and :makeout:
https://www.miataturbo.net/diy-turbo-discussion-14/find-me-turbo-fits-these-critera-64606/

I think a properly set up turbo system will outperform a supercharger system at any rpm.

I agree... I'm thinking this is more for someone who wants to build something with a massive turbo and keep their low end. TD04s need not apply.

If you're serious about a twincharged configuration, why not just run the turbocharger and the supercharger in series (air filter -> Turbocharger -> Supercharger -> head) and use the supercharger's internal bypass valve (which is normally open only at idle and light cruise) to bypass the supercharger once the turbo is spun up and making boost?

Quick spool valve? This idea comes up once in a while and usually goes nowhere. If you want to do it just for the neatness of it, then by all means go for it. It would be pretty cool to see. However, I think that a properly sized/tuned turbo only setup will be more effective and certainly easier to build/fabricate.

This seems like an entirely doable idea... someone with a coldside kit should be able to rig something up easily. I don't know if those include a pulley clutch though, i'd still want to be able to turn the SC off above a certain PSI.

Would running all that air through the SC itself cause any issues, flow wise? We'd be aiming to use a rather large turbo i assume, and i don't know how well all that air would flow through a bypassed SC.

How about running the sc into the compressor side? Then use a bypass on the sc that starts to open at preset rpm/psi?
Would the sc help with spool? However minuscule?

Mass air -> sc->turbo->IC->intake.

Either way, torture test-track for air...

I remeber an Opel Manta with Volvo engine that did just this: SC at lower rpms which disconnected in favor for a turbo up high.

I'm at work, so I can't look for it, but search for "Opel Manta Hilmerson" and I'm sure you'll find something.

Use a regular turbo feeding into a positive displacement supercharger. And just put in a 1 way valve between the two for when the turbo is off boost. Using a MAP sensor this would work.

This set up actually compounds the boost; if the turbo was running at 6psi before, and the SC is setup for 6psi, you will see boost pressures over 12psi. Remember that this is using a positive displacement SC that will move a certain volume of air per revolution regardless of pressures involved. The heat added into the air is also compounded at the same ratio as the boost so a massive incercooler is necessary.

I'll dig up some more info on this once I go to sleep and wake back up lol

A certain model of the jdm nissan march uses a twin charge system from factory. There is also a newer vw also uses it. You could look into how they set up their systems.

For motorsport nitrous and other systems are proven to work.

For daily I dont think it would be reliable enough.

Compound turbo charging sounds more inteesting...

Of course one could always spend the kids' shoe money and run a twin-scroll turbo and a pulsed header...

A member (I think it was 1Hot4Pot) of TurboFord.org did just this using a Holset HX35w and reported lower spool times/rpms. HX35's are big. The motor was a 2300 sohc 2 valve with a decent, not great, flowing head. Most 2.3 hx35 combos were spooling from 3-3500. IIRC 1Hot reported 2800 or so with the pulsed header.

Then there's the VNT/VGT route, or just build a 9:1 motor and use less boost 'til the engine really gets turnin'.

Supercharger setups are more reliable than turbo systems anyway. It would be a complicated install but I see no reason why reliability would have to be sacrificed. Check out the information here and calculate theoretical HP figures for a twin setup:

http://horsepowercalculators.net/tun...ncharged-setup

Yes, obviously.

I mean, how could a huge device with lots of intricately-machined interlocking parts, a belt-drive system, and its own self-contained lubrication system possibly be less reliable than a much smaller device with only one moving part which is externally lubricated and has no gears or belts?

It's just basic logic, really.

I got sidetracked thinking about this the other day too, here's too diagrams I found of the vw tsi engine

https://www.miataturbo.net/attachmen...ine=1333579352

https://www.miataturbo.net/attachmen...ine=1333579352

heres another using the SC's bypass valve, would want to make sure that was big enough not to choke the flow of the turbo. Seems like this wouldn't be the best solution if you're using the sc to spool a big turbo.

https://www.miataturbo.net/attachmen...ine=1333579352

The placement of the turbocharger bypass valve is more optimal in the Audi illustration.


I'd need to see some kind of documentation from VW explaining why they would re-engage the SC at high load. Unless they have undersized the turbo and thus require the additional compression of the SC to achieve maximum boost (which would be stupid) then this doesn't make sense.

Google the wiertech emno twin charged civic. That thing is amazing and built very well. over 300whp on low boost with a d16 SOHC. It runs extremely quick in one lap of america and time attacks in Ontario. Someone should build a turbo/FFS set up. Or build a custom coldside manifold mount with an integrated air to water in the manifold.

https://www.miataturbo.net/attachmen...ine=1333579352

This is pretty much what I'm planning but without an IC between the turbo and super.

You could snag a supercharger off an old toyota previa mini van. We used one a while back to back yard boost a carb'd civic. They are small easy to mount and have an s/c clutch on the front so you can turn it on or off.

I'd thought going with a m45 and a bigger turbo.

the super-first with bypass seems like the way to go

but instead of a bypass, a simple one-way valve would be cool. some sort of lightly sprung piston that the turbo has to suck through, but the super wont push air back through.

honestly the belt driven turbo with "freewheel" is a smarter option.

I don't think that any restriction to the turbo compressor would be a good idea.
Ak Miller usede to make such an animal, but I don't think it's the optimal solution...
(On Edit; I think that may have been a blow-through app. Oops!)

As an aside:
I do question the idea that one would want a sub 2500 full-spool. Drive-line parts stress, cylinder pressure, and internal engine stress come to mind...
I don't mind a 3k spool.
My Mark VIII has taught me a lot about powerband. Below the three-k point she's docile. Good driveability, decent mileage. Above, she wakes up. Fun.

How is increased load on the drivetrain at -2500 going to be any different than the same load at high rpm people are already running?

You could get an m90 off a 1991 thunderbird in a junk yard. The 944 crowd has pulled those and rebuilt them for less than $300. Its better to underwork a large supercharger than over work a smaller one for intake temps and power draw on the crank.

Torque.

the same load at lower RPM means that a higher amount of torque was used to achieve it, which means MASSIVe stresses on the piston crowns, rods and crank. But mostly it means bent rods.

Dann

What type of supercharger are you planning on using?

?? AFAICT stress on rods is a function of peak cylinder pressure. And torque is a function of that. RPM doesn't figure in the equation.

Making the same horsepower at lower RPM is only possible by producing more torque. You know that.

Dann

I have a quick spool valve in my car.

Would it not be true that, for a given VE and spark angle, peak cylinder pressure will be greater at lower RPM, as the piston will be higher up in the cylinder at the moment when complete combustion of the fuel is achieved?

Dann and Joe are on it.
I should say though, my comment was a little blanket-y. If we're only talking of adding a couple of tens of Lb-Ft over stock, probably not a big deal. But if we're trying for 150+ at 2500, well... [And I should add I'm thinking more of pump-gas as opposed to E-85 or real race-gas.]
Then we need stronger, usually heavier, parts, or exotic pricey parts...
Then there's the whole cost/complexity/benefit ratio...

Hey! Here's an article talking (in fairly plain language) about this whole pressure/crank angle/burn-rate/time bit. It's not the authoritative works, but a nice primer, if oversimplified a bit.
Combustion dynamics... It's a PDF so...
Here's one on time/torque/inertia.
Most of this is probably covered in our own 'detonation' thread.

It also takes time for fuel to burn and flamefront to move.

Hydrodynamic lubrication is not as good at low revs.

All that sounds good if your going with a V8 pushing 1200hp. But if your only going 400 or less hp. Just go T3/T4.

Superchargers usually have to get to a high rpm (sometimes mid) to get the boost you want. Turbos can kick in sooner.......

I like superchargers for track. turbos for drag.......

I just think for 400hp or less, money would be wasted.

At that point you would have a built motor any way. Run the boost high.

And if your running stock motor,,,, way too much over kill.

Good for Mustangs, but miata's,,,, probably just not going to push the gap between power adders that far......

My T3/T4 spooled under 3000.

And all the hype about getting boost faster is over rated. These cars never had power before 4400 anyway. When you dump that clutch.....Its instantly useless in first and second anyway.........

Some lag is a little better in these cars for take off.....Atleast you move out of spot.

As far as wanting to use a m45 to help you on take off.. bad decision...period.
It is fun. But not the awesome spool your wanting. And you would be tightening belts like no other maxing it out.

If running stock engine. The 2560 pushes more power than you should, and spooles like a mad man.

I just cant see the efficency in turbo plus SC.

But you never know....Prove otherwise...

Turbo Tim once built a twin turbo for a miata. We where all about it. But the comparison between twin and single turbo wasn't awsome like we expected.

why, for manageable tq output, thats why.
The sooner your wheels start spinning from throttle the more mangable the car will be.
A turbo that has to respool causes a lag issue in throttle application.

Let me know what your t3\t4 did in terms of airflow in either lb or grams from 2k to 7k, 3k to 7k, 4k to 7k.

Look at wrc cars, sure they use turbos, but they also use ALS for a reason.

This guy built a 600+ hp Elise using a 6265/ similar turbo and dual fuel systems with E100 in one of them for detonation resistance, then filled in the shiesty mid range with some combination of the parts from one of these kits:

http://visionfunction.com/product.php?id_product=2


He claims that the final product has a magically tame powerband in the video. There is no mention of how he routed the blower and turbo relative to each other, but they do specifically say that they just bolted the kit on and went for it, so they couldn't have used any funny business, and I would guess that they are just blowing through the blower and leaving the bypass valve shut.


Turbo Magazine built something similar with a TRD blower and Majestic T76 on a 1MZ-FE (Camry V6) powered SW20 MR2 in ~02ish. They blew the turbo straight through the blower (which was the only real option with the TRD kit) and made enough power to lift the heads on the 1MZ with what they described as a very docile, linear power band with the blower on the car, and laggy misery without it. They also postulated that the boost passing through the blower actually drove the blower belt and put some power back into the crank. That bit feels a little contrived/ in the realm of massively diminishing returns, but I guess it's plausible. You certainly wouldn't want to try that with an M45, though, as it would present a really serious restriction at any sort of worthwhile power level. A ported MP62 or Whipple 1.2L would be pretty kick ass, though.




In one-day-hypothetical-fairytale-land, I'd love to do something similar with my Ubercharger kit, if I can manage to put the power down in Street Mod autocross trim. Being as how I hear that current Street Mod Miatas are having trouble putting down 300whp, I hold little hope, but it provides an interesting exercise in academia, I guess.

I only said m45 as I noticed they have 1.6l kits and its on the exhaust side, I could make an adapter will some help to bolt other superchargers on, but if I can get a cheap supercharger kit I would go for it.

Wow. The Lotus is sick.

Anyway, just FYI, no comment, circa Jan 2011

RE: The VW 1.4 TSI “Twincharger”
Won "International Engine of the Year" 1.0~1.4 class 4 times consecutive and again 2009:
http://www.ukipme.com/engineoftheyear/previous04.html
"Best New Engine" 2006 + "Green Engine of the Year" 2009 (categories in IEOY)

Autocar (UK):

" ...
[VW's] 1.4-litre engine, which mixes turbocharging and supercharging, is said to be too complex and expensive to produce.

Instead, VW engineers now believe that new turbocharging technology can achieve similar results at a much-reduced cost.
..."

Given spark angle at MBT, not "for a given spark angle"...

I will guess yes, a bit, despite the oft mentioned "you want spark advance such that peak cylinder pressure occurs at 12/15/18* (I forget) ATDC."