I'm trying to get my MBC set just right. I have two Autometer gauges, one is only boost and the other is boost/vacuum. I started with the boost/vacuum gauge and tuned the MBC to 24 PSI.

Then I switched to the boost only gauge and it was reading 17 PSI. So I tuned the MBC to 24 PSI on this gauge.

Just now I switched back to the boost/vacuum and it showed 30 PSI! It's about 93 degrees out so that isn't helping any.

Obviously one of the gauges isn't correct and I doubt the stock turbo on the IX can make 30 PSI. Do you agree that the boost/vacuum gauge must be bad? How much boost could I see from the stock turbo?

Edit: All PSI numbers are peak and from 3rd gear

 

Sure it can make 30 psi, it just can't hold it. I would invest in a good gauge and figure out what is going on.

 

I've heard that 25 psi is around the max for the stock turbo on a IX. Is this a "spiking" read or a constant read on the boost gauge?

 

It did the normal spike and hold for a second then drop slowly. It showed 30 for a few seconds.

 

as tock evo 8 w/ 10.5 housing turbo can spike 34.5 lbs then drop as the rpms climb.

 

I've had 21.6 and it was droping after I got intercooler pipes I saw 23 PSI but it was droping to it holds like 17 - 18 PSI

 

I would suggest you investing in a better boost guage. The stock one is not too reliable from what I hear. As far as the 30 psi spike... it seems to act just like a like stock boost setting would. My car spikes to 1.4 bar (on a stock boost gauge), holds for a few seconds, and then slowly creeps down as the rpm's rise. I would have to imagine that if your MBC is hooked up correctly and the turbo still spikes and then creeps, that the turbo can't sustain the amount of boost your asking it to provide. I would turn the boost controller down, get a boost guage, and a tune. Just my $.02

 

Whoa, I sure hope you were doing this on race gas. I can't imagine running around on Cali 91pisstane and PURPOSELY setting the boost to 24psi, much less raising the boost when one of the gauges already says 24psi. Yes, of course the stock turbo CAN run 30psi. We've been doing it for 3 years. It does not sustain it at all, so there's no way you held 30psi "for a few seconds." That would indicate the higher-reading gauge is probably way high, but you should have your boost checked by a MAP sensor to verify. Go to a local dyno and do a run to check the boost in the proper manner.

Noogles, not every 10.5 can hit 34.5psi. In fact, most can't even get close.

 

You guys are making me sorry I even asked this question.

I'm looking for solid answers, not "I've heard" or "someone told me", but thanks for the effort


A stock Evo 8 w/ 10.5 housing is kind of irrelevant, but thanks


Again I don't see how this relates to my question, but thanks anyway


You didn't even read my post did you?! Autometer Gauge! Dynoflash tuned! Wow this is amazing.


Real answers only please. Thanks for understanding.

 

Thanks for bringing me some sanity Warrtalon. I am running 94 octane (well crap CA 91 w/ octane booster to help me to 94). The problem is there are no shops within a few hours with a dyno. Is there any other way to have my boost checked by a MAP sensor to verify?

 

91oct with octane booster is not 94oct, and that is NOT enough to be messing around with your boost like that. You are lucky if you didn't damage anything.

You don't have to have a dyno to check your boost, but that's usually the easiest way to get a MAP sensor hooked up and check it while stationary. You may just have to find another Evo owner in the area who has a MAP sensor who will let you use it...or, hook up someone else's known-good gauge to see what it says. Whatever you do, PLEASE TURN THE BOOST DOWN.

 

Well god damn! Sorry for trying to help.

 

I thought the increase in octane depended on the booster used. Can't you make 89 octane into 110 with the right mix?

I thought the ECU will retard the timing to prevent damage from too much boost, right?

I wasn't expecting to see the 30 PSI. As soon as I saw that I turned it down to 24 PSI on the low high gauge until I get this figured out.

 

Your going to mess something up if you dont turn your boost DOWN!!

Its a REAL good idea to put race gas in when your setting your MBC

I agree with all the stuff Warr told you to do

 

Really?

I know i've seen 35lb spike on mine verified by my Innovative dl-32 logger