will boost increase enough with 3" piping from turbo to stock mufflers (no pre-silencer) to make the car hit fuel cut?? Im kinda curious about this, cause since I have the car confirmed Im starting to think on what Ill do to it.. Ill change every little stuff that is recomended before I mod it (oils, plugs, plug cables...). but then I think for starters I will just mod the exhaust, cause I have to learn to control the car before I go to really big numbers. and also, the exhaust mod is pretty cheap and I think I will have no big problems because of it, right?

so.. main question, will I need an FCD with that mod?? (custom DP)

(oh.. I almoust forgot the fact that I will have to rebuild the engine )

thx in advance

 

You'll get boost creep, that's for sure. You might want to port the wastegate (if you haven't already). As far as i know the Fuel cut happens at high RPM, not at high boost. I could be wrong though.

 

boost creep ??!! darn.. I tought that boost creep was caused by to much boost... erm.. completelly free exaust for example.
can U explain exactly what boost creep is then?
I tought it was that the pressure was so much that the waste gate wouldn't be hable to bypass enough air causing the turbo to spooled so fast that the boost would increase so high in the engine that it would cause detonation.. isn't that what it is? :\

and about the fcd.. what's the need of a FCD with the RB turbo back system if not cause of fuel cut at high boost? im confused now

 

the stock computer tells the injectors to cut fuel to the rear rotor if the boost goes above 8.6psi. the fcd will trick the ecu into thinking that it is always 8.6psi. even if you are boosting more. Boost creep is exactly what you mentioned and really anything past 5.5psi is boost creep if your not usuing a boost controller to get you there. the stock wastegate spring is 5.5lbs and the stock wastegate hole is not neer big enough to flow enough exhaust out to keep boost that low. So when you get a free flowing exhaust and intake your going to be boosting to 10+psi because of boost creep. If you where to port your wastegate you would only see 5.5psi until you bought a boost controller and then you would boost to whatever boost level you want (reliably)

 

live and learn (me of coarse)
how exactlly does a boost controler works ? eletronic thing? or... humm that kinda makes sense now. it's a valve controls the pressure to that pressure thing (don't know the name) that controls the opening of the waste gate, and that way I can adjust the boost manually.. or is it an eletronic thing?

 

just on a side note....how do you port the wastegate?

 

that one is easy.. use the search function :P

 

Ah, I stand corrected.

 

but remember that it is 3" but then it ends with stock stuff... will it increase boost by that much ??

 

You should hit fuel cut. I had a corksport 3" tapered down to 2.5" dp mated to a bonez high flow cat with stock catback and still creeped.

 

:\ darn.. or not!
how was the sound of it ?

 

sounded quiet. Not as nice sounding or aggressive as racing beat though.

 

u will hit fuel cut only in 3rd(maybe) but for sure in 4th and 5th

 

Those are S4 Turbo II numbers. I think S5 is 1PSI more... above 6.5PSI is boost creep & ~9PSI is fuel cut.

Note I've NEVER hit fuel cut with an open exhaust on a TII, but I have pinged a few times under full boost on cool-damp weather.

I've heard the S4 TIIs normally won't boost creep with an open exhaust & intake, but the S5s DEFINITLY will.

 

Wait a minute, he has a S5 right? The S5 don't have a fuel cut right?

 

Wait a minute, he has a S5 right? The S5 don't have a fuel cut right?

 

yes s5's have fuel cut just like the s4's but it comes on a little later also s4's have a better chance of boost creep because of the inferior wasteage design (one small hole) the s5 wasteage was better because of the 2 flapper system.

 

I have stock exhaust exept for the 3" corksports downpipe and I get boost creep, so you will definitely get boost creep.

 

thx for all the help!
and yes it's a s5. even behing an s5 should I port the wastegate anyway?

 

It's not going to hurt anything...unless you do it wrong. LoL