916Duke

Just after some advice. I've recently fitted a PPP ECU to my MY99. I'm running a magnex de-cat center, H&S BB and samco hoses. Last night was the first time I've had the time and space to really test the car since fitting the ECU and de-cat center (I've also just replaced the MAF). I'm seeing approx 16psi in 3rd and 4th, but if I WOT at 3000rpm in 5th I'm briefly seeing the needle swing round to approx 17.5-18psi before quickly settling back to 16psi. Is this typical of the PPP ecu or am I needing to eliminate this spike? I guess I'm just after some reassurance before the knocklink arrives. Cheers.

NelsonUK

Did you change the brass boost restrictor ? I do believe the PPP cars run a slightly larger diameter hole in the brass restrictor ? I'm sure someone else will clear this point up ??

This could be your problem

916Duke

Hi, thanks for the reply. I didn't change the restrictor; I believe that the restrictor wasn't changed on MY99-00 cars with the PPP (According to an old post I found by John Banks) - But enlarging the orifice may be an option; I guess that perhaps the exhaust components I'm using are a little less restrictive than the original PPP stuff and that what's leading to the 'spike'. What I don't know is if the 1.5psi overboost in 5th is typical or is something I need to address?

Dibs

My MY99 PPP with full decat only ever peaks at 17psi in 4th/5th, and normally settles back to 16psi. As NelsonUK stated, you probably need to drill out the restrictor by a tiny amount (0.05mm?).

I think the fuel cut is set at just over 18psi, so you need to keep it below that.

Try a search as there are lots of threads on this subject.

Dibs

NelsonUK

My MY00PPP with full decat is running with the restrictor drilled out to 1.3mm but with the cooler weather of late I was finding the same thing - WOT in 4th or 5th would peak at 17psi but drop back to 15/16psi.

ozzy

I'd be surprised if different de-cat centres on back boxes would make that much difference.

It's more relevant when you do a full de-cat, especially the very restrictive downpipe. Can you refit the std catted centre and see if the boost settles?

john banks

916, I would leave it as it is. With Optimax it should be fine. In the cold I used to run mine at 19 PSI held on a PPP ECU with full decat and it didn't det. A brief overboost (as long as it doesn't oscillate or det) is fine. Means you will usually have 15.7 PSI target boost even in lower gears.

916Duke

OK guys, many thanks for your help and advice - it's much appreciated. There is no oscillation and it quickly settles to 16ish, so I'll leave it as is for the time being. The knocklink will be fitted soon anyway. Cheers, Shane.

Dibs

How did you get it to run at 19 psi? Dawes device?

Dibs

Dibs

I'm interested to know how I could run slightly higher boost on my MY99 PPP with decat - any ideas?
Cheers
Dibs

john banks

Yes dibs. Get a knocklink. If it doesn't spike or go above second green at the top, turn it up. With 99/00 decat PPP if the knocklink is working (test it) then it is difficult to go wrong.

Dibs

Thanks John.

I have a knocklink (which I need to check!) and I can read the boost level accurately on the SECS display, so I'll give a Dawes Device a try.
Cheers
Dibs

john banks

No you can't, SECS saturates at 18.4 PSI and will read that even if you go higher.

yhe chod

knocklink is vital it seems what pitfalls should i avoid in fitting it .
it needs to be very accurate after all.
how would you know if its working properly?

john banks

Fit the sensor to the block just behind the OEM sensor near the bellhousing on the passenger side. Run on maximum sensitivity. Hit the bolt holding it in with a spanner and make sure it hits the red.