Over boosting

mr2haz · Post by **mr2haz** » Wed Dec 21, 2005 9:29 pm

I have just taken my rev 2 for a test drive after fitting a 2.5" de cat pipe and it is now boosting over 1 bar.

Previously it made about 0.8 bar. Have i done something wrong, what do i need to do because i don't think it a good idea running more than a bar as am still using the standard intercooler.

raptor95GTS · Post by **raptor95GTS** » Wed Dec 21, 2005 11:03 pm

with the decat the car will boost slightly higher than before due to it being more free flowing.

If you have an MBC turn it down a it and you'll be fine

raptor95GTS · Post by **raptor95GTS** » Wed Dec 21, 2005 11:03 pm

grrr mail server error and it still posted both

mr2haz · Post by **mr2haz** » Thu Dec 22, 2005 7:22 am

Where would the MBC be fitted if i have one?

raptor95GTS · Post by **raptor95GTS** » Thu Dec 22, 2005 2:12 pm

should be under the passenger side x brace since thats the place most folks fit them

matt_mr2t · Post by **matt_mr2t** » Thu Dec 22, 2005 2:25 pm

In a more scientific way it's fitted between the turbo and the actuator.

mr2haz · Post by **mr2haz** » Thu Dec 22, 2005 5:49 pm

er... there isn't one fitted there. Is it possibly fit somewhere else or perhaps the boost has been changed in another way?

JekylandHyde · Post by **JekylandHyde** » Fri Dec 23, 2005 3:49 pm

Nothing is "wrong."
You made the exhaust flow freer to make more power and it is.
A side affect of that is you are boosting higher.
1.00 bar is not a problem to be worried about unless you are experiencing fuel cut.

Other wise, relax and enjoy your new power.
You paid for it after all!

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mr2haz · Post by **mr2haz** » Fri Dec 23, 2005 5:49 pm

I put my foot down in third gear on the way home. i have a greddy peak boost gauge with the warning light set at 1 bar i floored it and lifted off then the light came on. boost peak showed 1.2bar. that can't be safe and if i didn't lift off the accelerator i think it would boost more

Century Motorsport · Post by **Century Motorsport** » Sat Dec 24, 2005 12:52 pm

what de cat have you put on it? Ive heard stories of the cheaper ones catching on the wate gate and holding it closed/open causing boost problems.

jimGTS · Post by **jimGTS** » Sat Dec 24, 2005 1:29 pm

mr2haz wrote:I put my foot down in third gear on the way home. i have a greddy peak boost gauge with the warning light set at 1 bar i floored it and lifted off then the light came on. boost peak showed 1.2bar. that can't be safe and if i didn't lift off the accelerator i think it would boost more

i suggest you buy a cheap mbc mate, and fit it and turn down your boost......
you dont really wona be running 1.2bar on a stock ct26....1bar is about what is recommended...

mr2haz · Post by **mr2haz** » Sat Dec 24, 2005 2:11 pm

This is the de cat i have fitted.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

jimGTS · Post by **jimGTS** » Sat Dec 24, 2005 2:21 pm

mr2haz wrote:This is the de cat i have fitted.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

not sure on the make, but either way, £60 for a downpipe is a bargain...

hicks · Post by **hicks** » Mon Dec 26, 2005 10:15 pm

im having a similar problem with my tubby but is overboosting since fitting a ct20b. the problem is that you can use a mbc to turn the boost down only up. still trying to find a solution for mine although i have a feeling it is the downpipe as it is an xs power crap and has been removed 5 times now due to the wastegate sticking. have a feeling its now not opening fully causing it to boost too high. gonna take the downpipe off again soon and grind more of the flange down see if that cures it.

hicks · Post by **hicks** » Mon Dec 26, 2005 10:27 pm

just looked at the downpipe and the area where the wastegate opens looks very shallow. could be that the downpipe is a poor design and there isnt clearence to let the wastgate open fully.

slipping clutch · Post by **slipping clutch** » Wed Dec 28, 2005 8:42 am

I have had the same overboosting problem with my rev 1 since decatting it - its been going on over a year now and no one seems to have an answer foe me but one explanation is/was that the ct26 turbo I have is now spooling up way to quick as I have an aftermarket filter one end and a decat pipe and mongoose system the other end of the turbo - apparently as it was explained to me only about 1 in 10 turbos do it after decatting / filter and pipe fitting. A mate of mine knocked the cat out of his rev 2 and put the stock pipe back in (minus the cat) fitted a mongoose system and his did exactly the same !!!! All way to frustrating I have spent literally hundreds of pounds trying to cure this problem af any one can help or has any comments about the turbo spooling up to quick I would be most grateful! P.S. the actuator opens the waste gate on mine if I pull the pipe off on use a foot pump and and blow in 9psi of pressure so |I dont think its the pipe blocing the actuator - PLEASE HELP!!!!

thebutler · Post by **thebutler** » Tue Jan 03, 2006 9:09 pm

I heard Turbo Technics do a turbo exhaust housing conversion witch addresses this issue. I looked into it as I'm having the same issue myself now, having fitted a 3" downpipe. I have a HKS superflow induction kit, and HKS Super Drager exhaust. Basically there is no back pressure at all!

They quoted 120 + vat.

Will probably go this route if it becomes too annoying. You can always lay off the go pedal!

HTH

Steve

The Morris · Post by **The Morris** » Tue Jan 03, 2006 11:44 pm

thebutler wrote:I heard Turbo Technics do a turbo exhaust housing conversion witch addresses this issue. I looked into it as I'm having the same issue myself now, having fitted a 3" downpipe. I have a HKS superflow induction kit, and HKS Super Drager exhaust. Basically there is no back pressure at all!

They quoted 120 + vat.

Will probably go this route if it becomes too annoying. You can always lay off the go pedal!

HTH

Steve

i bought this, solves the problem. Trouble is putting it on without damaging the ceramic blades. Mine broke and it was a £450 rebuild.

Fred · Post by **Fred** » Wed Jan 04, 2006 2:30 am

I read that when you decat , the exhaust gases have more freedom to flow , so much freedom infact that the waste-gate can't 'waste' enough pressure resulting in overboost .

It sounded right to me at the time .

slipping clutch · Post by **slipping clutch** » Wed Jan 04, 2006 8:20 am

Hi Steve, Thanks for the info - I will check out turbo technics.

www.imoc.co.uk

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