PDA

View Full Version : boost control problem


johnplogii
09-05-2005, 02:25 PM
i am having problems controlling boost. long block setup is basically eastern's 700hp buildup (girdle, billet caps, 8.3:1 j & e's, esp cam) with my own heads ported, extrude honed, 1.92/1.50 stainless valves. currently running te44, 60lb inj, duttweiler modified stock intercooler, atr headers & terry houston down pipe. wastegate is ta style stocker that i re-drilled to fit. it seems to function properly but is not doing the job. car also has no exhaust. the 60lb inj are a recent add on as the 40lb ones were running lean at 15psi boost. my problem is no matter how i adjust wastegate or set up boost lines(even direct from compressor to actuator) boost comes on a little slow then increases in stages with rpm & shifts. the way it is set now i get 15lbs in 1st gear then builds to 20 in 2nd & by 3rd gear shift is at 21. car runs pretty good but i would like to see steady boost so i can tune it. i don't want to waste money on a te style gate if that isn't the cure.

ES1
09-05-2005, 06:55 PM
Not sure this would apply but I would
make sure puck is covering the exhaust hole
check and make sure wastegate & turbo hoses are not split
look for holes in IC hoses and IC
make sure IC clamps are tight

kenmosher
09-06-2005, 01:21 PM
It sounds like not enough flow for the wastegate hole ... it's being "swamped" with no exhaust downstream ... can you go with a bigger hole and flapper?

johnplogii
09-06-2005, 04:30 PM
hole can't go any bigger safely. it measures 1 1/8" and the flapper measures 1 3/8. ive got 1/8" sealing all the way around. all boost lines and intercooler hoses are new. do you think some exhaust backpressure would help or this heavy duty (18 #) wasegate?

ES1
09-06-2005, 09:03 PM
You could try a boost control valve like what Race Jace sells.

Keller
09-06-2005, 10:23 PM
A HD actuator with a tighter spring may make the problem worse. It really does sound like a flow problem. Somehow, the bypass flow isn't flowing well. Disconnect the actuator and let it flap open with no actuator attached to prove this. You should get NO boost. If you start getting boost, that means there is a mismatch somewhere. Perhaps the bypass hole and wastegate hole in the dowpipe don't match precisely.

johnplogii
09-07-2005, 10:03 PM
Thanks for all the input. I will post more as soon as I can try running it with the flapper disconnected. Right now the radiator is out being cleaned. I should have it back in tommorrow.

johnplogii
09-10-2005, 01:11 AM
Tried running it tonight with wastegate flapper disconnected & made sure it was wide open. No boost in first gear but 2nd gear by 5000 rpm it built 5-6 psi boost. I guess this explains the extra 5-6 psi in 2nd & 3rd but I don't understand why. Could it be just the velocity of the air at high rpm wanting to spin the turbine instead of turning right & going out the wastegate hole? As I said before the hole is 1 1/8". The carbon ring on the hole shows the puck is sealing perfectly even & I don't see how the houston downpipe could be covering any of the hole since the flapper lines up. Do I need to remove & port the inside of the turbine housing better leading to the wastegate hole? Can you change out flappers for a bigger one? I was told that the terry houston down pipe would control boost for high horsepower applications & my car is only running low 7's 1/8 mi. I thought when I bought it they said 8-900 horspower before you would start having boost control issues. Any more input would be appreciated.

Keller
09-10-2005, 11:13 AM
Good analysis. Looks like you found where the boost creep was coming from. :thumbsup:

Some careful porting may help. As you stated, there is really nothing in the Houston pipe to work with. The turbine housing may have a bit to give up in the wastegate hole area, but not much as you've illustrated. Internally smoothing the turbine housing may help a bit.