Mark-o

It's a personal proof of concept. So many people have an opinion on how it could/should/can't/won't be done. I build oddball vehicles and this is one I've wanted to tick off the list.

It has always been discussed that once this is said and done, a fall back to an IHI twinscroll or BW EFR could be on the cards depending on outcome.

The engine has previously been supercharged for many years, The twin charge is just another level of the game.

Ryan_G

iTrader: (8)

So it is for science.

Mark-o

No, science is for scientist. Automotive design is for engineers. I'm just a hobbyist who likes to try new things (new to me) and that likes toys that are a little different from the crowd.

Forced induction of any nature has almost never been done on these vehicles (Maruti Gypsy).
There are almost zero practical applications for the vehicle, it's an offroader.

As mentioned earlier, it's personal proof of concept. Making it work, because I think I can. A bit of oddball fun and nothing too serious.

05pearl

iTrader: (4)

I've got a Precision 5857 BB sitting in my office with the hopes of one day using it in a compound set up with my current turbo. Wish there were more people trying to pull off a set up like that so I don't have to be a guinea pig.

Curious to see what happens here in any case.

Full_Tilt_Boogie

iTrader: (1)

1) Its complicated. That little diagram does tell the full story. A lot of electronics would be required to make a system like that function well.

2) His supercharger is going to way out-flow his supercharger. So it only makes sense to put that on the low pressure side. Doing it the other way around would be awful. It would spool slower and make less power than the turbo would by itself.

3) With a setup like that, when the bypass valve is opened, you are going to lose the biggest benefit of the system, which is the improved exhaust scavenging created by a higher differential pressure between the intake and exhaust ports.

With the turbo "feeding" the supercharger you get improved spool and scavenging, at the cost of the parasitic loss and restriction on top end power. Everything is a compromise. That VW setup is a compromise as well, but my suggestion is actually very easy to implement, while the VW way is almost guaranteed to not work properly when designed by some guy in a shed.

Mark-o

With the positioning of supercharger and turbo, it is quite easy to implement a change in plumbing layout to affect the staging of sc/turbo. I expect it is only a days work to redo the plumbing to suit. Something that down the track will most likely occur for comparison on the dyno.

As for the electronics required, I know of 1 very successful Australian built twincharged vehicle that uses only vacuum actuators for the bypass activation. Not everything needs to be overly complicated to achieve reasonable results.

Full_Tilt_Boogie

iTrader: (1)

Define functional.

Its not hard to make it do something, but I suspect logs of boost would show that its not doing its job very well.

Leafy

iTrader: (1)

Not sure why. With his setup, the bypass should open as soon as the turbo pressure differential across the turbo reaches a certain positive amount, super easy to control the bypass valve for the blower that way with just a normal blower bypass can.

Full_Tilt_Boogie

iTrader: (1)

2 superchargers in series, when suddenly one disappears (is bypassed). What is going to happen?
Even if the supercharger was just being used during spool, which would be an apocalyptic waste of the scavenging effect. The turbo would still have to spool to get the boost back up to where it was before the bypass opened. This shouldn't take very long, but it would still happen.
Now if you were doing it correctly, the way I assume VW is doing it, in which you take advantage of the scavenging effect and only open the bypass at high RPM to un-restrict the flow of the turbo, you would be controlling boost with the wastegate while the supercharger bypass is closed. Then in order to make the transition you would want the weastegate closing as the bypass openes in order to smooth the transition and keep the boost up.
Thats just talking about WOT performance. You start talking about how this is going to work when youre working the throttle and thats where the electronics come in. The wastegate and bypass would both have to be integrated into the ECU, looking at TPS, RPM and load in order to make the car drive properly.

None of that matters though, because that VW setup has nothing in common with this setup. Here we have a huge turbo and a tiny supercharger. The supercharger has to be downstream of the turbo, or it will be terrible.
If the OP had an oversized supercharger and a tiny turbo, I would say otherwise, but I would still say that it should not be bypassed.

Mark-o

The turbo used on the VW TSI uses a typical vacuum actuated wastegate, nothing ECU controlled there.
The bypass on the inlet is electronic and ECU controlled, using a butterfly valve manufactured by VDO.

These are readily available and affordable (sub $200AUD). I have a mate who is a mechatronics/automation engineer who is willing to make an interface to it if desired.

The intention is never to have the supercharger "suddenly disappear". Moreso, We will attempt to mimic the ramp of up the turbo spooling with the rate that SC flow is bled off in an attempt to avoid the "valley of death such as the Subaru liberty TT experiences between stages.

Full_Tilt_Boogie

iTrader: (1)

In for results.

nitrodann

Lol, that changed quickly haha.

It occurs to me that a flappy door type bypass which would be pushed closed by the blower and sucked open when the turbo overcomes the blower would do most of this pretty easily?

Dann

triple88a

iTrader: (2)

Because if you put the sc first in line it will limit the amount of air going into the engine to whatever the sc is at... If you actually understand the video you'll see extra butterflys, clutches on the supercharger, bypass valves and tons of extra hardware just to get around the problem.

Mark-o

I appreciate the input, however if you actually understand the plan you will realise:
- The sc14 has an electromagnetic clutch on the supercharger drive pulley. that can be disengaged once the turbocharger is making adequate boost.
- The Supercharger Bypass Valve, currently sized at 80mm opens to allow the turbocharger to freely breathe directly from the airbox.

As you mentioned, the supercharger will limit the amount of air going into the engine to what the actual output of the supercharger is. Up until the point of being bypassed, at which stage it no longer presents an upstream restriction.

As mentioned earlier, I like to try new things so I am all ears for valid arguments/concepts that help me learn and improve the potential.

The main variance I will have from the VW TSI engine is the lack of the "Dynamic compressor operation".
Low revs will be supercharger only, high revs turbocharger only, with a small window of compounded boost at the crossover period.
There will be (at this stage) no programmed logic controlling operational conditions where the supercharger may be engaged based on demand.

Mark-o

I find this variant of the previous image easier to visualise with a few notes included. Excuse the N00bCAD MSpaint.

Identifies:
- Idle bypass valve to avoid heating of the intake charger as the supercharger outputs against a closed engine throttle body.
- Supercharger bypass valve for unrestricted airflow to the turbocharger for greater high end potential.

stinkycheezmonky

Just for ***** 'n giggles, here's an example of a twincharged Honda from several years ago. When it was running, it did so like a raped ape. There were heat/cooling issues though. The tech is a little old, so take it with a grain of salt: Dual-Sequential Chargers - Honda-Tech

There were better threads on the same car, but I couldn't find them in a quick search.

Mark-o

Dann,

Research "Backdraft Damper". They're a commercial valve of the size you need, commonly used in the ventilation industry.
You can get them in 316 stainless, sized to match common duct dimensions which would simplify fabrication.
I can't comment on how well they seal or the forces required to move them.

Onyxyth

iTrader: (2)

If you're thinking of the HVAC type, I think you'll have a hard time finding one under 5" round. The ones we typically work with are 8-14" diameter and don't seal nearly well enough for an automotive application.

FAHREN

in for metal shavings

Full_Tilt_Boogie

iTrader: (1)

Similar to a setup I posted in another thread on this subject