Quick boost question

SuBaRiNo · Post by **SuBaRiNo** » Sat Mar 06, 2010 9:47 pm

Would a boost leak, lets just say between the Turbo and the Top mount intercooler, on an ej20 turbo show signs on a boost guage. Is it as simple as... if the factory boost is 6PSI and u are leaking 1PSI then the gauge should show 5PSI?? Or is there more to it?

Or does the wastegate detect only 5PSI and let the turbo work harder to compensate till it gets to 6PSI even with the small leak.??

Dave

Outback bloke · Post by **Outback bloke** » Sun Mar 07, 2010 8:12 am

Second option until it gets to a point where it can't keep up any more and then you start to lose boost pressure. That is actually why I was asking about where you had your boost gauge fitted. I think if it had a major split or crack in one of the pipes you would not still be getting 10psi at the plenum. I don't think the turbo is big enough to keep up.

Definitely worth taking them off and looking for cracks or splits. It is free and will diagnose or eliminate a symptom.

Gannon · Post by **Gannon** » Sun Mar 07, 2010 9:31 am

A boost leak after the turbo will also make the engine run very rich because the afm is reading air that isnt going into the engine. Running too rich can rob you of power.

To check for a boost leak, open your bonnet and with the engine running, quickly snap the throttle open for a few seconds (long enough for the engine to make boost, but let go before the revs get to 6000rpm)

You should be able to hear air escaping.

Does your boost gauge show vacuum when it is idling? If it does, you boost gauge is hooked up the the right place

SuBaRiNo · Post by **SuBaRiNo** » Sun Mar 07, 2010 10:10 am

yeah does show vac at idle... i belive it is in the right spot.

Andrew and I spotted a suspect pipe today that has either been wrapped in heat shield or had a bandaid fix. I will be investigating today... was just asking a few random questions to learn more about this set up.

Finally have been able to borrow another car so today i will be actually be able to rip the car into bits and see if i can find anything. After a test drive with andrew yesterday he thinks it is missing on one cylinder at full throttle only.

Dave

spike · Post by **spike** » Sun Mar 07, 2010 8:01 pm

bit of trivia i heard that may help or might put you too sleep
back in the days of skyline turbos being too expensive for the kids on the street and only being used on the track they were too competitive and the other cars couldnt keep up, dont ask what catagory i got no idea.
well the higher ups decided that to make it fairer they would inforce boost pressure, ie with a wastegate
well the idea worked reasonably untill the drivers and team managers decided that if you just turn the amount of air being turned out of the turbo up the boost gauge would say it was at say 10 psi and open except that inside the manifold the air pressure was going up up up, to about 11 psi or so as the waste gate just couldnt dump enough air.

good story if you can understand it