Bozeye

As title.The reason i ask is regarding me fitting a de-cat downpipe to my MY00 ppp.
Transient overboost,as i understand,is a possible consequence and im just doing a bit of risk assesment.Can it easily kill my car? Is it a costly repair etc.
Thanks for any comments.

greasemonkey

Transient overboost is also known as boost spiking, and that description tells you all you really need to know.

When you decat the downpipe, the freer breathing makes the turbo spool up quicker. If you're unlucky, you can create a situation where the boost builds so quickly that the ECU (via the boost solenoid and wastegate actuator) isn't able to react quickly enough to contain it, and spiking results.

Obviously the potential consequences depend on how bad it is, and how long it's left unchecked. If it's bad, and left alone, the result could eventually be a blown engine, but that's very much an extreme case.

The ideal solution is a remap to tune the boost solenoid duty cycle into the faster spool characteristics. However, if the problem does present, in most cases you can eliminate it simply and cheaply by increasing the bore of the restrictor in the wastegate actuator pipe.

The easiest way to spot it would be to fit a good boost gauge and a KnockLink before you fit the downpipe. Make good mental notes of the way boost builds and is held, and also make certain that there's no knocking. Then fit the decat, and keep an eye on what the boost needle and KL lights are doing.

[Edited by greasemonkey - 1/30/2004 5:06:39 PM]

Dazza's-STi

Think I'v seen it mentioned in an old Joy of Sex Mag! "remember them"
I'll dig it out and let you know!:

Dazza

loosecannon

IF YOU CONTACT SCOOBY SPORT THEY KNOW ALL ABOUT THIS PROBLEM AND THEY SELL A PUCKER DOWN PIPE TO COMBAT IT

Bozeye

Thanks all.
Excellent explanation and advice greasemonkey.Do you know if the ppp ecu is remapable.Also can you advise on the cost of a knocklink as this project is begining to sound expensive.
But this is exactly what i wanted to know,the safest way to decat.
Thanks.

greasemonkey

Yes, it is, but doing so wouldn't really be the best use of resources. You'd be better off getting a used standard ECU and getting that TeK'd, and then selling the PPP ECU here.

Around £130 by the time you've got the KnockLink unit itself and the sensor. However, you shouldn't really consider this as part of the cost of your decat project, as in my view a KnockLink should be considered pretty much an essential piece of kit for any turbocharged Subaru given its value as a protective device.

In any case, as far as costs go, if you do get any spiking, as mentioned above, you can usually sort it more than adequately without the expense of a remap. You can buy larger bored actuator restrictors for a couple of quid each, and if that sounds like too much of an outlay, you can make them yourself for pennies!

Bozeye

Ok understand now.Actuator restrictors sound much better than remap.