well i have a 4.2L v6 with 1.75 primaries,2.5 cross over,4'' dp with a76gts. i am useing a maneul boost controller that has worked fine in the past. i made a new kit and bigger turbo and now i have boost drop issues. i have looked over everyhose and gasket. it makes 30psi and then from 5400-6200 it drops to 26ish psi. also i have a Racegate with a 9 psi spring.

 

Matt, was it doing this on the first dyno pull with the new setup? If no gaskets or hose connectors are leaking..could it be the rings?

 

is the wastegate bleeding off some exaust pressure?

 

well i doubt it has anything to do with the condition of the engine. it shows no signs of blow bye,oil consumption or anything like that. i will most likely do a compression test and leak down tommrow. just to say i did.

also the wastegate is gonna bleed off exhaust pressure thats what it does. it should allow enough to spin the turbo to make the boost i have it set at(unless i am maxing the turbo and there is no dang way i am doing that).

 

maybe its bleeding off to much. i wouldnt over look it.

 

oh trust me i won't over look it.

i think its in my manuel boost controller i have another one i may try out.

 

You might just need a stiffer spring in the WG. IIRC, Blackmagic94 had a similar problem a while back, except his wouldn't even let the boost go as high as he wanted it to, but after putting a stiffer spring in the WG, he was able to crank it up without any problems. Is there really a need for a 9# spring in the car if you're pushing it all the way to 30? Do you ever really turn it down that low?

 

no need at all. but turbonectics does not make a stiffer spring for the racegate. not realy sure why the hell that is. i would love to have a 18psi spring. cause to be honest i don't think it will ever see less then 18 psi anymore. thats what i like to run on pump gas. and would love to be able to unhook the controler for pump gas boost. and then hook it up for the good stuff and crank the boost to 30 hehe.

 

That IS pretty strange. :scratch:

 

tell me about it. fools.

for the New gen they only make a 15 psi. and for the super new gen they make a 20psi spring

 

controller can keep the gate shut so exhaust pressure is blowing it open at high rpm.

 

ok i can go for that. but why can't the controller keep it shut? cause of the little ass turbonectics spring. since i am trying to make over triple what the spring is rated for.

 

Yep. That's the same thing that I was talking about. Here, I found the thread I was thinking of.

https://www.theturboforums.com/smf/index.php?topic=93447.0

 

I vote exhaust back pressure too. At those RPM's with that mush boost your backpressure to boost ratio is prolly at its highest. Even if you disconnected the boost line to the wastegate it will prolly still open it. Are you running any air to the upper of the wg diaphragm?

 

ok but before i could make 30psi with a smaller turbine wheel and a spilt tang .84 housing. now i have the .96 open tang houseing.

also with the smaller turbo i have to put the controller on teh bottom of the gate and feed straight boost to the top.

when i put it on the 76gts like that it made crazy boost had to let the heck out. put it on the top and turn controller down and made a steady 15 psi. 3 turns later i made 31ish psi. put her on the dyno and thats when we noticed the boost drop.

yes the boost controller feeds the boost into the top of the wastegate jared.

 

Yeah good memory, I had a .3 bar spring when I was told it was a .5 bar spring, installed a .85 or something in it and now it makes the bigger boost, but this problem is different. I never could hit anything over 18-19 psi steady, and he is hitting it and its falling down. I would point the finger at his manual boost controller bleeding pressure off.

 

Would be interesting to see how much backpressure you have.
Is there room for a second spring in the actuator?

 

Who me or the poster?

 

The poster LOL

 

i will measure the backpressure next time its up and running. i am swaping electronics at the moment.

it will be less then i had before. i know the turbo will make close to 40psi on this engine. cause when i first got it up and running with this set-up i was controlling the lower side of the gate. and it made Way over 30psi lol.

also i have not measured to see if i can fit a 2nd spring in it or not. but i will measure a turbonectics evolution gate spring and see if i can't fit it inside the race gate spring. i know its smaller in diameter but not sure if its small enough.