rpm_pwr

Hi,

I'm running DIY controlled seq. twins with a straight through 3" exhaust and FMIC. I'm pushing 14psi. I wish it was 12psi but the wastegate is overloaded so I don't have a choice. Anyway on the 2-3 shift, in the cooler weather we're having lately, I've been getting big spikes up to 17psi on hard shifting.

What causes this? Is it just that it takes to long for the wastegate to re-open (I shift mad quik yo!) as I grab the next gear? What can be done? I'm not that excited about pulling the turbos off just to port the wastegate. If I set the fuel cut to say 19psi would it be OK but then the 17psi spikes are going to kill my motor. The thing is I went to so much trouble to avoid the transition spike (I get 12-12-14 no dip or spike) but I suspect there's another flaw in the system I wasnt prepared for.

-pete

P'cola FD

Profec B, and/or port the wastegate. I wouldn't mess around with 17psi. I hope you have an upgraded ecu with all that.

Rx-7$4$me

yeah, the wastegate needs to be ported... Im suprised your motor hasen't detonated and blown up already on you! consider yourself lucky! now why you get it when you shift I do not understand. Does it creep at all? does it spike when u stomp on it, or when secondary comes on? Turbo's love cooler weather, so that helps it spike that high too. Does it spike after u stomp on it again? that would just be a huge boost spike from the wastegate not being able to handle it if im not mistaken.

Controll that boost! or poppity pop!

rpm_pwr

Thanks guys but it's really the why that I'm after. I had a Profec B but I wasnt happy with it. I do my own wategate control with a solenoid map. From 15.5psi up the wastegate is wide open.

I ONLY get the spike on gear changes. I do get some pretty mean flames- maybe I'm accidently running anti-lag It's just that porting the wastegate won't help it open faster will it?

I guess the other theory is that grabbing a new gear hard puts extra load on the engine, which equals more exhaust which equals overloaded wastegate. Sound right? So either I pull of turbo's that are going to die in 12 months anyway (they've got 115k on them now and leaking oil) or turn the boost down

"Controll that boost! or poppity pop! "

I love that

-pete

skunks

poppity pop pop, pop BANG!

GsrSol

Porting the wastegate lets more flow by.