When I am at a stop and punch the gas, quickly burning through the gears, I hit 15 PSI consistently. (like you would do for a 1/4 mile run) However when I am on the freeway, lets say 4th gear @3000rpm's "then" stepping on the gas completely, my psi will rapidly shoot to 16-18 psi. No es bueno. I am having quite some trouble tuning this blasted thing. Is this problem common or is it something I will have to deal with? Or is the MBC (turbo xs) broke? Alex, I was going to send you some pics but my camera took a dive into some water. It is installed correctly though.


-Don

 

Hi, the reason your MBC is giving you different boost pressures in the higher gears ie; 4th and 5th is because the engine load, and duration of the gear is longer so the boost has more time to rise, and also the engine is working alittle harder..

I have been using an MBC myself for 25k+ miles, and you HAVE to set it for peak boost pressure in 4th or 5th gear..

If you set it in 4th gear you might not be able to go WOT in 5th without getting more boost than you wanted, but you might have increased performance in the lower gears. But if you set it for like 16.5psi or 16psi in 5th at WOT then you know you will never overboost

Also do you have any other mods, particularly Turboback exhuast, upipe and Samco IC hoses? I HIGHLY recommend them when using an MBC without engine mgm't, it will make using it safer and life less stressfull on your engine and turbo IMO.

 

Yes i have an up and down pipe. Thank you so much for that information. I really apreciate your help you dont even know. It took a while for me to get back on i-club, comp died.

-Don

 

Sure no prob. Also one other thing you might notice that I should tell you about is that sometimes when using an MBC the weather can have an affect on teh boost pressures..

For instance in this cold weather we've been having in the northeast I have my MBC set for 16.5psi in fourth gear now(I just was at track so I set it fairly high), however if the temperature was to rise to 60F tomorrow it would not be uncommon for the peak boost pressure to lower down to 15.5psi without adjusting the MBC.

So without touching the MBC settings colder weather then when you set it can = higher boost and warmer weather can =lower boost.. It usually has to be an 20F-+ difference for me to notice any change in boost pressures.
Paul