S4 T2 boost build up too fast
12-21-11, 10:52 PM
#1
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S4 T2 boost build up too fast
Hello,
I have a stock s4 turbo, removed emission, cone air intake with stock piping, intercooler, and a racing beat rev 2 exhaust.
I am on my second turbo, the first one blew on 5000rpm at second gear. (The first turbo was already smoking, but was working) The car also has the hesitation problems that stalls the engine if I floor the pedal.
Now the second one blew the hose to intercooler off with a BOV-like sound although it doesn't have a BOV, I put the hose back on and tightened it even more, and now it has compressor surge whenever I get to around 5000rpm at second gear.
At first I thought it was just a bad turbo that's causing the trouble (the first turbo that was smoking), but after I replaced it with the second turbo, yet the boost problem didn't go away, I started suspecting it's something else. I'm not sure if it's the engine itself that's causing the problem and destroying the turbo in its process. However I am having problem diagnosing the reason why my car is building up the boost too fast and too high.
I need some input on what could possibly be the issue that's causing the boost to build up so high that it blows the hose off or even cause the compressor surge. Also what could be causing the car to stall whenever I floor the pedal?
Thanks for your time
I have a stock s4 turbo, removed emission, cone air intake with stock piping, intercooler, and a racing beat rev 2 exhaust.
I am on my second turbo, the first one blew on 5000rpm at second gear. (The first turbo was already smoking, but was working) The car also has the hesitation problems that stalls the engine if I floor the pedal.
Now the second one blew the hose to intercooler off with a BOV-like sound although it doesn't have a BOV, I put the hose back on and tightened it even more, and now it has compressor surge whenever I get to around 5000rpm at second gear.
At first I thought it was just a bad turbo that's causing the trouble (the first turbo that was smoking), but after I replaced it with the second turbo, yet the boost problem didn't go away, I started suspecting it's something else. I'm not sure if it's the engine itself that's causing the problem and destroying the turbo in its process. However I am having problem diagnosing the reason why my car is building up the boost too fast and too high.
I need some input on what could possibly be the issue that's causing the boost to build up so high that it blows the hose off or even cause the compressor surge. Also what could be causing the car to stall whenever I floor the pedal?
Thanks for your time
12-21-11, 10:59 PM
#2
Slung all my rods
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Its your exhaust. You put a free flowing exhaust on a turbo car you will increase the spool drastically.
My best advice is change to external gate if its not externally gated, use a smaller spring, and get a bov. Your going to make the turbo surge without it. Yes I know some oem system do not have them, but these are generally low pressure turbos, or turbos designed with antisurge housings.
My best advice is change to external gate if its not externally gated, use a smaller spring, and get a bov. Your going to make the turbo surge without it. Yes I know some oem system do not have them, but these are generally low pressure turbos, or turbos designed with antisurge housings.
12-21-11, 10:59 PM
#3
Do you have a boost gauge? If so what's the boost peaking out at. With the exhaust you may be over boosting. If your overboosting just have your wastegate ported. To fix the surging add a bov. The stalling sounds like a fuel issue...when it stalls does it bog down?
12-21-11, 11:27 PM
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Yes, the car bogs down, and if I don't let go, the engine will die. To get out of the bogging I have to tap the pedal until it reaches higher rpm. However the car runs smoother and has less hesitation when I disconnect the pressure sensor for some reason.
Last edited by DairokutenMaoh; 12-21-11 at 11:34 PM.
12-21-11, 11:31 PM
#5
RE EVOLUTION
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Its your exhaust. You put a free flowing exhaust on a turbo car you will increase the spool drastically.
My best advice is change to external gate if its not externally gated, use a smaller spring, and get a bov. Your going to make the turbo surge without it. Yes I know some oem system do not have them, but these are generally low pressure turbos, or turbos designed with antisurge housings.
My best advice is change to external gate if its not externally gated, use a smaller spring, and get a bov. Your going to make the turbo surge without it. Yes I know some oem system do not have them, but these are generally low pressure turbos, or turbos designed with antisurge housings.
12-21-11, 11:32 PM
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No I don't have a aftermarket boost gauge, the stock boost gauge was spiking all the way to the top when I accelerates around 5000 rpm at second gear tho. However the car seem to run smoother when I disconnect the pressure sensor for some reason.
12-21-11, 11:48 PM
#7
The bov will release pressure when ever you let off throttle not during acceleration. Port your waste gate more and it should run better. The engine may be running very lean, with out the proper fuel your engine will die. If the over boosting isn't fixed you may blow your engine. So take it easy till everything is worked out.
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12-22-11, 12:25 PM
#13
Rotary Enthusiast
And to OP, I'd suggest you not let the car spool until you get something like an Rtek ECU. These cars have a system that cuts fuel after slightly above stock boost is hit. You are probably hitting around 12 psi. The exhaust alone is usually enough to cause this.
If you keep boosting it hard like that, you are going to have bigger problems.
12-22-11, 03:51 PM
#25
Rotary Enthusiast
I'd get a form of fuel control first. Slightly bigger injectors and a better fuel pump. With those mods, your engine will be toast in a month. The fact is, you just don't have the proper tune or enough fuel to support the power. Lack of fuel = lack of apex seals.