Boost dropping off?
 

I went tot the dyno today to tune for 10psi and it would drop of to about 7 or 8psi at 6000rpm and stay that way untill redline. My tuner thinks that the turbo is out of its efficiency and thats why it is doing it, but the turbo is a greddy 18g and i thought dsm guys ran 20psi on them no problem? Could it be my boost controller? its the turbo xs high performance manual one. Any ideas?

Re: Boost dropping off? (18G_prelude)
 

What kind of compression are you running? Do you have Vtec?

Re: Boost dropping off? (CivicTurbo12)
 

It's more likelly that it's your boost contorler or your wastegate. Do you have internal or external gate on it?

Re: Boost dropping off? (blown_LS)
 

Its an internal wastegate and the setup is in a 97 prelude, H22a4.

Re: Boost dropping off? (18G_prelude)
 

Must be something fucking up with your boost controller. It could also be your wastegate too. Its not the turbo. Alot of hondas use the 18G turbo and don't have that problem. You're running a vtec prelude so you shouldn't be having boosting efficiency problems. I'd look at your boost controller first than your wastegate. Any boost leaks?? Or could it be that your creaping to 10psi but its really set at 7psi?? I don't know good luck...turbo's are fun but require alot of knowledge, maintenace, and tunning all the time.

EDIT: your wastegate could be set at 8psi and it creeps to 10psi cause of the amount of load that the turbo is taking on cause of the big motor. See your wastegate lets off the wasted air at 8psi but because of the amount of exsaust that is created the turbine just spines faster. Fast enough to create that extra 2-3psi until your engine decides to settle down at 6000rpm. https://honda-tech.com/forums/images/smilies/emthup.gif


Modified by dainteg at 3:07 PM 4/14/2004

Re: Boost dropping off? (18G_prelude)
 

It's the internal wastegate that has to be ported out. My 18g holds fine up to 13-14 psi but any higher it spikes about 3psi and fluctuates from 13-15-14 and this is on a 2"dp. I'll be hitting the dyno again on the 24th with a 2.5"dp and pushing it to 20 psi to see what happens. Hopefully my avcr will try to hold the boost as steady as possible. As you can see in my dyno graph the wastegate opens and closes @15psi https://honda-tech.com/forums/images...s/emthdown.gif

http://www.boosted-hybrid.com/viewtopic.php?t=28

Re: Boost dropping off? (roydogg)
 

If the internal wastegate needed ported out it would spike too high rather than dropping off. I would check the wastegate acuator or you could have other problems, possibly to high of compression, creating to much "turbulence" at higher RPM's for the air to flow smoothly through the turbo. Cam/valve timing could be another thing to look at. Also be sure that your not loosing combustion pressure, from bad rings or out-of-round cylinders. Good luck

my boost began falling off with my turboxs hpbc also.

I then got a profec BII, problem solved https://honda-tech.com/forums/images/smilies/emthup.gif