Boost control Questions

[Supafly]

i started the tuning process the other day on my car. with the boost controller set (HKS EVC4) @10psi the boost holds perfectly fine. it hits 10psi and holds rock steady. once i turned up the boost to 17psi the boost would hit it's mark but immediately fall off back to about 10-11psi toward redline.

last night i did the ghetto external spring trick, and that got me holding 15psi on my higher boost setting but not quite as solidly as i'd like.

so, is it more likely the actuator or the boost controller?

[Hijacker]

are you using the stock T25? if so, the volumetric effeciency of the turbo peaks at 14 or 15, so overboosting the turbo should cause it to fall back down significantly, not to mention you run the risk of damaging the turbo.

[Supafly]

no it's not a stock T25. it's similar to/bigger than the Big T28. i'm not sure if it's the stock actuator or something different that majestic put on it when they rebuilt it, as my stock actuator bolts to the actuator bracket and this one was spot welded to the bracket.

[AznRide]

you might be overboosting your turbo, that's why it falls down. Your turbo is too small for 17 psi then. Try to set it at 15 to see if it will hold.

[Supafly]

i am not overboosting this turbo. i know of someone that has run the same turbo and it held at 20psi no problem and made good power.

[S13240]

I guess if you really want to know if you're overboosting or not go get a dyno run done to see where your power band falls at. Most likely the turbo can't handle that much boost. You can try an hks actuator, but that's only a possibility it may help hold a bit more boost or not at all. And that guy with the 20 psi is a bit insane, he probably has an upgraded t25 to be able to hold 20 psi. Never heard of anyone doing 20 psi on their t25 until now. Some guys barely hold 14 psi.

[Ender_Zero]

....you guys arent listening. he just said that its NOT the stock T25.anyways, i guessing you have an upgraded wastegate? if so, what is it set at?

[Supafly]

....you guys arent listening. he just said that its NOT the stock T25.anyways, i guessing you have an upgraded wastegate? if so, what is it set at?

at least someone reads the thread . it is not an upgraded wastegate to my knowledge, it's whatever majestic turbo threw on there. most likely a repained stock actuator. when hooked directly to turbo pressure the car hits 7psi.

i've ordered the HKS already, it's worth a shot. if that doesn't cut it i'll dig deeper.

[DriftS14]

I'm willing to bet it's not your actuator. Or your boost controller.

[S13240]

....you guys arent listening. he just said that its NOT the stock T25.anyways, i guessing you have an upgraded wastegate? if so, what is it set at?

DUH! :pface Meedah speaka da no englise! :icesangel

[Dori Dori]

I'm guessing it's in the boost controller. The EVC IV, I've heard, can be very difficult to get calibrated properly...something about the fuzzy logic feature. Borrow or make an MBC and see if your car will hold boost...that way you'll know for sure.