Boost Up, then Down (Everything Stock)

[wajouba]

Ok, I have a CA18DET, everything is stock, but the problem is that when I first step on it (WOT) my boost goes up to 0.7 bar at 3500rpm, then while my RPMs go up it goes down to 0.4 bar at 7000rpm, why is that happening what could be the problem?

Need an answer could this is driving me crazy...

[rico05]

What's your setup

[wajouba]

Nothing bro, nothing at all, stock, no exhaust no nothing... just a muffler, thats the only thing we added to the car...

[lostmenoggin]

Check for boost leaks in your sidemount piping. Ripped coupler, loose clamp, stuff like that.

[TurboTec]

Well if you still hav e have std wmic that will restrict flow and the back pressure in the exhaust will do so too and a free flow air fliter would help too upgrade these ie with a 2.5"or 3" with a 740 turbo fmic and a hd stage 1 chip with 255 walbro would see yo to 220-230 max bhp with 15psi on the std T25

Archie

[float_6969]

Agreed. If you're running the stock exhuast it's VERY restrictive and may be preventing the turbo from making boost at higher RPMS.

You could also have a boost leak, or a leak in the exhaust BEFORE the turbo (at one of the exhaust ports, or the turbo flange).

Let us know if that helps.

[wajouba]

Thanks to you bro, and to TurboTec, i'll have to wait for some money to be made first... hopefully by then this thread would still be alive to give you guys feedback ... Could the selisoidle valve have anything to do with this boost thing?

[mmm240]

selisoidle

???

This thread will be hear for years, just remember to post back in this thread and not to make another

[float_6969]

Yea, threads never go anywhere on NICO. They're saved forever. FINDING them can be problematic, but they're there, somewhere.

[rico05]

A factory T25, with factory exhast will do that. It's just out of its efficency range at 7000RPMs. Factor in the restrictive stock intake and exhaust hardware, and there you go. Run 3" off the turbo back, and a hard intake pipe and you will hold boost better. I hold 1bar from about 3200RPM until I shift around 7200RPM. I have HKS SMF filter, KA MAF, hard intake pipe, T25G .80a/r and 3" off the turbo with hard intercooler pipes and an ARC intercooler. Hope that helps.

EDIT: I assume you were trying to refrence the factory boost solenoid? I have never run one as mine is a swap, but I could see the ECU limiting boost higher in the RPM range to reduce boost (and therefore thrust loads on the pistons and rods) to maintain longevity.