gzon

To you who is tired of all the boost issue threads I can only say sorry but I have not found a thread that takes care of the spike problem that I have. (I have searched)

My only mod is a 3" downpipe.

My problem is that I get big boost spikes at first turbo, when using the standard pill in wastegate hose, I get 12-13psi spikes and then it gets down to 9psi. Now I have a manual ajustable restrictor on the WG hose so and I have tuned it to get 10psi at the spike but then I only get 7psi of boost when spike is over.

My second turbo gives 7psi at first and second gear, 8psi at 3:d and fourth gear and 10 psi at fifth.

My main concern is the spikes at the first turbo, is this normal? I had the same spikes when the car had precat on. What can cause these spikes?

Thanks!

P'cola FD

The spike (if occuring around 4,500 rpm) is due to the turbos switching from single to twin mode. If you want to control the spikes, you have to install the bleed valve in the precontrol vacuum hose.

Qball

i also heard that going non-seq solves the transistion spike since there's nothing to trans. too..

mine are still seq so i dont have experience to back this up.. can anyone back up the validity of this statement?

Zoomspeed

yes thats true

to control the spike you ahve to put a valve in your precontrol line.

gzon

No its not the 4500rpm spike.

I will try to explain.

If I run from 1500rpm and up at 3:d gear I get a smouth and nice boost. but if I just cruise at 2000-4000 and then "step on it" it spike a big before getting down to a normal boost.

xph

This is from my last dyno, stock turbos, slightly ported wastegate...

red is 3rd gear and blue is 4th

Dan

gzon

well, something like that, but the thing is that my only mods is a DP and nothing else, but Im getting 12-13 psi spikes when using the factory WG pill.

gzon

Yes I use a larger now, but then the spike is at 10psi and the boost after spike only 7psi. I would lika 10psi all the way.

gzon

should the car have these spikes or is it any fault at mine.

toecutter

Im having the same problem and am all stock.
Spikes to around 12psi especially in 4th.
I have installed the valves but also do not want to bring total steady preasure under 10psi.
second turbo runs steady 10 psi.
Any Ideas?
Am I risking engine failure?

Nathan Kwok

I have the same problem and I'm all stock. I'm going to go to a ProfecB which is supposed to control them, but for now I just don't jam down the gas while lugging at 2k rpms...

Flybye

One of the main reasons why you guys are spiking the way you are is because the stock ECU SUCKS at controlling boost.

An easy way to kill the spiking you guys are getting only on the first turbo below 4500rpm is by prespooling the 2nd turbo a little more. Remember that the prespool flap acts as a mini-wastegate. Vent some more exhaust into the 2nd turbo, and you won't spike as much on the first turbo, but be careful not to vent TOO much exhaust otherwise you get a bigger spike at 4500rpm. It comes down to fine tuning it.

I'm not like some people that take the easy way out by going non-sequential.
I'm not pointing fingers at anyone *Looks up and whistles*

jf4828

Just a thought? IMHO I think you do have a problem w the wastegate not functioning as it should or something of that nature. I wouldn't worry too much because you probably won't lean out @ those pressures. If you want to be safe, get a new o2 sensor and put an AF gauge. As long as you are running good ratios I wouldn't worry about a thing. Although you said your only mod is a DP but your signature says"Mods: Custom 3" Full SS Exhaust, Non-seq, Custom PiperX intake, Huge custom FMIC, Pettit ECU." That puts things in a different perspective?

toecutter

Wont prespooling the secondary a bit more limit the total boost on the primary?

ZeroBanger

When I got my power FC ALL my boost problems were solved. What ever I set my power FC to, is exactly what I get, never more, never less. Power FC rules.

gzon

Well. Ive decided to go NON-SEQ insted.

Dan

good 4 U..... If you need help, go to www.dontbearikki.com and if you get stuck e-mail them or send ryan a pm "He was kind enough to help me and he will probly help you to" It makes him happy to see people cross over!!!!!! Good luck, you will luv it.

Wade

iTrader: (1)

This is a common problem, my car did the exact same thing when I first added a downpipe. You need to adjust your precontrol with a valve like you do your wastegate. Open the precontrol restriction slightly and your primary boost will go down. Then you can raise your secondary a little with the wastegate valve. You can have a 10-10 pattern with a very small spike at 4500 RPM.

Wade