Hi not sure if this is the right place for this, other than I'm new, but here goes.

I'm building a 90 S5 Turbo II right now and I have no clue what the rule of thumb is for injector size or flow. This seems a little cart before horse because I haven't even got the car together yet, but I'm trying to do some research. My current set up is:

Mild streetport
Catless downpipe
High flow catted mid pipe
Stock CBE
Stock turbo
Stock tune
k and n filter but stock air box

I've been told I can run up to 550 cc primaries and 720 cc secondaries without tuning. Is that true?

I know the car will benefit with a tune but I'm not there yet and won't be for some time.

I've done some searching and haven't found this kind of info yet maybe to specific. But, if someone could point me in the direction of some good links or their own experience that would be great.

Thanks

 

well, the one missing piece from your tuning question is ... what are you supposedly tuning? the stock ECU is not programmable.

i know boost can exceed stock levels with a higher flowing exhaust system, but all you seem to have is basically a downpipe and cat. i'm guessing CBE = cat back exhaust???, and with the word "stock" in front of it, it's your stock exhaust system.

i don't think you need more fuel on a stock turbo on an aftermarket downpipe with stock exhaust.

that said, i know some guys run/ran GSL-SE injectors on their mildly modded S4 cars and those are between 680 and 720 cc depending on year, so even if you did NEED 720s, it looks like the stock ECU would run them.

 

kind of along the same lines, can you swap the primart and secondary injector location? if we have 550CC secondaries and i need them as primaries, are they swappable?

kinda thread jacking here. im looking at the rtek7 chips for some basic extra power and they said 550 primaries and 720 secondaries.

 

where is the extra boost coming from?

the stock T2 has 550 cc for both primaries and secondaries. the only difference between S4 and S5 is impedance (and connector).