Re-map needed?
 

Evening guys, looking at getting a new de-cat pipe so I can fit my other, quieter exhaust, seeing as my car has been re-mapped as de-cat already would I need to get the map tweaked straight away or could I get away without it for a while?

Regards

Adam.

alot of people say you need to get a map for the decat but when mine went on the rollers that day at ssr they said it was running fine with no issues on the standard map,mine had a full decat system so from what the boys said I cant see it being a problem but many will disagree. best bet mate is to give simon a ring

If its already mapped for a decat then you should be fine as its swapping one pipe for another decat pipe, although how this will quieten it down I'm not sure, unless you are putting a sports cat on, in which case it's worth tweaking the map or at least getting it checked.

If the decat is to similar spec i.e same bore, there should be no issues.
If you have a boost gauge check it before and after for spiking when coming on boost and when changing gears. Also check for any higher then expected mid range and high rpm boost levels.

As long as the new pipe isn't a lot more restrictive, which putting a cat back in would be (which can cause gas exiting issues), or is massively less restrictive causing boost issues as described above, then it should be fine.

If you haven't got a boost gauge, buy one. No modified Scooby should be without one IMHO.

sorry for hyjacking the thread and sounding dumb but what is boost spike?? and also I've just had a boost gauge installed, what is the boost level for a standard blob STI??

Well the exhaust I have on the car at the mo Lucky is a Buddyclub, which has an awesome sound but gets a bit much on long journeys, so hoping my other system will be quieter even when still using a de-cat pipe, good old trial and error :norty:

Will not just changing the back box have the same effect?, or are you going from a 3" decat to a 2.5" decat? Just thinking you could save yourself some time and cost by not changing the decat downpipe as I woudnt think it will not make much difference swapping it for another decat pipe.

I would try the back box first and see how you go.

I know about trial and error, I think I had about 5 different exhausts while I had the hawk lol.

Probably as easy to read this:



"Spiking is when your wastegate hole is large enough, but your actuator can is taking too long to fill with compressed air, so you temporarily overshoot your boost level. Example: you're set for 13 psi, and when you floor it it quickly rises to 16 psi, but then gradually drops downward towards 13 psi again.
A common problem with modded engines is a combination of spiking AND boost creep. That's where you're set for 13 psi, and when you floor if it overshoots to 16 psi, begins to drop back down, but as the rpm rises it goes up again.

• Normal boost rise when set to 13 psi = shoots up to 14, then 13, 13, 13...
• Spiking = shoots up to 16, then 15, 14, 13, 13, 13...
• Boost creep = shoots up to 14, then 13, 13, 14, 15, 16, 17...
• Spiking and boost creep = shoots up to 16, then 15, 14, 13, 14, 15, 16,17...

Set a manual boost control to 11 psi and floor it slowly in high gear. It should go to 11 psi and hold it pretty well. If it starts to slowly climb over 11 psi as the rpm's get high, that's "creeping". The boost creeps higher at high rpm's because there's too much exhaust flow for the wastegate hole to bypass.
Now go to 11 psi again, but tromp on it quickly! It will shoot to 13, or 14, or 15 psi, then drop down to 11 and stay there. That's "spiking."

Thanks steve that helps a lot.

I will make a video tonight and put it on here as i think mine is boosting to 1.5 bar then dropping to 1.3 :paranoid:

That's normal mate. It will only hold 1.5 for so long then begin to drop off.

Sounds about right.

Sadly I can't just change the back box mate, the Buddyclub is a push fit system with retaining springs rather than nuts and bolts.

The reason for wanting to change the downpipe is that I've been told the one on the car is from a classic and won't allow me to straight swap the exhausts, pretty sure from the turbo back is all 3'' at the moment and the other exhaust I have has a much bigger resonator section so it should at least lower the noise a few db's.

Ah, I see. Makes sence then. In which case I would get the map checked.