We Got our First Polo GTI in today...

**Corey_R** · 07-01-2011, 09:24 AM

and the Golf 118TSI...
all three just tuned for slightly different purposes.

**weedub** · 07-01-2011, 11:43 AM

Me too. Got a new Polo GTI coming. Not only want to upgrade it - I want to know if it can be reconfigured to compound charge. i.e. with turbo feeding the SC. Anyone know if this can be done?

**Corey_R** · 07-01-2011, 11:50 AM

That sounds like a pointless exercise, at least with the stock hardware. Superchargers start earlier in the rev range and drop off at higher revs. Turbos start higher in the rev range and usually run through to the redline. So the turbo won't be spooled up yet when the supercharger is running and then the supercharger has lost its efficiency when the turbo is on boost. Hence why VW have them switching over at a certain RPM.

**weedub** · 07-01-2011, 12:42 PM

I agree the stock hardware may not work but I am not convinced that the principle can't be workable. There is lots of info out there on the subject. Eg: 8v 2l Twin Charged -my Little Project - Alfa Romeo Bulletin Board & Forums

Rather than sequential in a compound configuration - The turbo should spool earlier as it is driven from more flow from the SC at low revs. When the revs are high the control valve could be used to drop out the SC at high revs.

I'd like to hear from APR on the subject.

**Corey_R** · 07-01-2011, 01:31 PM

I can't read a 82 page thread...
but in all the examples he mentioned, there is still switching happening. The "compound" section is the turbo boosts the supercharger then as soon as the supercharger is inefficient, it switches to the turbo only.

Interestingly he notes that the Golf does this too! So maybe the turbo is already in the path and therefore the Golf is already doing what you want it to be doing...

**Corey_R** · 07-01-2011, 01:48 PM

Ok... so looking at the VW "Self-study programme 359 - 1.4L TSI Engine with Dual-charging", the way it works is this:
1) You have fresh air coming into an air filter
2) You then have the mechnical supercharger with a "parrallel path with regulating flap unit J808" - the position of the regulating flap determins whether the air flows via the supercharger and/or straight to the turbo.
3) Charged/Fresh Air flows through the turbo
4) Charged Air flows via the intercooler into the throttle valve module into the intake manifold.
5) Exhaust gas flows through the turbo (or wastegate) into the downpipe, through the catalytic converter and out the exhaust.

So this confirms that the 1.4TSI is already a "compound" system with the turbo always in the chain and the supercharger being bypassed once its lost its efficiency - just as the Alfa dude you linked to suggested.