dmel

I only have a full Magnex system (twin DP, decat CC) and I have also removed the resonator at the intake keeping the standard filter.

The car keeps just over 1 bar (3,76 up to 3,80 Volts on MAP) in 4th or 5th. Boost overshoots sometimes up to 1,1 bar dropping back to 1 bar. I do not have a boost guage, I simply follow the MAP voltage.

Is this boost normal or slightly higher above normal? In lower gears it will hold 0,95 bar. Is the linear relationship of MAP voltage vs. pressure, proven to be correct by more than one people?

Pressure(psi)=(Voltage-2,2623)/0,1036

Beastie

iTrader: (2)

DMEL it is slightly higher than Normal. Normal peak on my car was 14psi dropping to 13psi held. Now that I have all the PPP on bar the ECU the boost has risen so it peaks at 15psi and holds 14.

Sounds much the same as is happening on your car but with the downpipe a little bit higher again. I should have the PPP ECU fitted this week. (Dealer received wrong one)

Cheers

Beastie

john banks

I use PSI = 10.25(MAP-2.29) based on figures Bob Rawle supplied. I find it linear, so did Paul in the DIY FCD thread, and the link manual says it is linear as do several internet sources re MAP sensors. Maybe atmos being slightly higher than 1.0 bar is making me inaccurate. Bob's figures - 0.88 to 4.84 V for -1.0 to +1.8bar. I need to test it some more because an 18 PSI boost target is overshooting on my EBC because I don't think my MAP calculations are accurate.

dmel

My 3,76 Volts held translate to 1,04 bar according to your regression and 1,0 bar according to the I-club regression.

This result, together with the fact that many boost guages are thought to be inaccurate leaves me with the question of how is it possible to know the boost pressure with 5% of error at most?

john banks

I expect it is, but I don't know and would like to know the exact calibration of the MAP sensor.

FOZ STiV5

On this subject my 1999 STiV is over boosting to around 18psi on every full throttle. I thought this was down to a downpipe and system I fitted. Decat 3.5 inch wide throat...but I have changed back to the cat + 3.5 system and still get 18psi. Very worried

I am thinking of fitting a dawes...anyone got any ideas..... help would be much appreciated.

john banks

Don't know why this is happening on your STi. However avoid a Dawes on STi. 18 PSI sounds FAR TOO HIGH for an STi. I would drive it under 15 PSI using your right foot until you can get it looked at. Usual suspects are oil in the restrictor or solenoid. Or with some downpipes blocking the wastegate closed, but you have excluded this by going back to the original downpipe.

[Edited by john banks - 2/13/2002 8:38:13 PM]

FOZ STiV5

John,

I was hoping you would reply....you seem to know your onions. I just go the car and it is mint BUT...it has a brand new engine and I mean brand new. The last owner was minted and I have a £8,500 reciept to prove from SAS. The engine has done 650miles... and before you ask ...I got the boost check by flooring in 4th and not taking it past 4500. I don't know why the boost is so high..... and the ecu should have cut in??????

The car has tarox and lots of goodies.... so I wonder if the ecu is standard.... but 18psi..CRAZY.

How can I check the ecu ....or restrict boost... there are not many Scooby expert dealers near me....I live Chester

john banks

Speak to the previous owner to find out what was done to the ECU?

FOZ STiV5

I know that sounds simple ...but for a long story ...it is not easy. It is up to me now to find out what is going on.....

To be honest I'm an enthusiast and if there is no quick solution I will either have the ecu re-mapped or buy another one. I don't really have the cash....BUT I would rather be safe than sorry??

By the way ...what is up with the dawes on an STi (too limit boost only)

john banks

I posted all the reasons in recent threads, but the long and the short of it is that you will have a flatter boost curve and could easily run lean and kill your nice new engine very easily.

I would find a specialist like Scoobysport even if it means a long drive to get it looked at. No point in remapping if you don't need to - it could be a perfect setup already!

FOZ STiV5

Thanks for the help John,

I will let the engine run in 1200~1500 miles with further gentle driving under 4500. After that I will have it looked at. I wish there were closer specialists to me

Thanks again,

Julian

john banks

Email me if you want and I'll give you my phone number and we can talk.