please help with overboost

rx7danny · October 22, 2012, 07:40:05 PM

new turbo and 4" exhaust fitted
having trouble with boost control
even with boost controller not connected no vacuum
it will hold .7 bar to about 6500 revs then suddenly shoots up to over 1 bar
any ideas anyone
look forwrd to replies
Danny

clive · October 22, 2012, 08:13:16 PM

Hi Danny,

When you say no boost controller I presume you are just letting what ever spring is in the wastegate take control,

Sounds like the gas flow is overcoming the spring pressure, if so start looking at either a stronger spring or a better bigger wastegate

hope this helps

m1tch · October 22, 2012, 08:15:07 PM

What turbo and wastegate do you have? Sounds like boost creep, hopefully its mapped ok above 0.7 bar just in case, what fueling upgrade did you go with?

rx7danny · October 22, 2012, 08:18:14 PM

borg werner s366 50mm wastegate not sure what make
mapped to over 1 bar but cant control boost
even just using the spring in wastegate

m1tch · October 22, 2012, 09:50:27 PM

What spring is the wastegate running? The wastegate might be too small for the turbo/getting stuck closed if its not a good make.

rx7danny · October 22, 2012, 10:25:13 PM

not sure what spring cheep ebay one
with old turbo used to hold .7 now spikes when reaching higher revs

m1tch · October 22, 2012, 10:45:55 PM

Hmm might be worth looking at getting a decent branded wastegate like a HKS 50mm, I had a 55mm Greddy type C wastegate which was matched with the T88-34D so it might be worth looking into getting a better branded wastegate - how is the wastegate plumbed in at the moment btw? I know you have disconnected the boost controller but im wondering if that might be causing a vac/boost leak which is meaning that the wastegate isn\'t working as it should.

rx7danny · October 23, 2012, 06:00:56 PM

straight into 4" exhaust
trying out hks soon

Indian · October 27, 2012, 10:00:46 AM

hey Danny, sounds like your over flowing your wastegate..especially with the the s366. I just put on of these on my street/strip car and have to run twin 38mm to control them nicely.. a 50mm gate, once working should do fine at around 14psi... Where is the placement of your gate and what manifold are you running?

rx7danny · October 28, 2012, 07:38:50 PM

im afraid cheap ebay manifold
going to try quality hks wastegate

Indian · December 06, 2012, 10:50:30 PM

Did you get this sorted?