reverus

ANOTHER non-esquential question... im having a really really hard time controling boost, some write ups say to vent the wastegate and precontrol vac lines back into the source (where the soleinoides are), some are saying cap them and install MBC, some are saying leave them to vent....

so i try to look at some diagrams to figure it out and... i divided by zero...

http://www.rx7.org/Robinette/images/TurbochargerBig.jpg

according to this diagram.. and looking at my own extra set of twins.... the secondary turbo has no wastegate?!?!?! only the primary does, the secondary just goes
exhaust mani->turbine-> down pipe!!!?? no bypass whatsoever?? how is boost controlled on the secondary turbo???

the only way i could see is with the turbo precontrol actuartor door in the manifold slowing exhaust to the secondary.. but with this wired open in a non-sequantial.... um... full boost??? full exhaust +no bypass=full boost??

RotaryEvolution

iTrader: (30)

pay attention to the location marked for the pills, they often go missing. the lines should always be hooked up to the solenoid rack, venting them is a really really bad idea..

reverus

they way i have it set up is, the stock pill on the pre-control, and a ball+screw MBC on the wastegate side. at the soleinoid rack i have the solenoides bypassed by just making a loop with vac lines. is that done correctly? or should they be capped?

also.... still dont understand how the wastegate can control boost on the secondary turbo being that it's attached to the primary turbine alone??

RotaryEvolution

iTrader: (30)

consider the solenoids as the dump line. if you cap them then you won't have any boost control and will be running strictly off the wastegate spring for minimal possible boost. a ball screw MBC won't be very accurate for consistent boost. what levels are you seeing at the moment?

reverus

actually got it fixed today, looks like the pre controll actuator still needs to be hooked up to the solenoid and the wastegate is capped on both sides, with the MBC in place of the restrictor pill, with this set up im getting 10psi and holding 100% steady to redline. omg i forgot how fast this car is. i still dont understand how the secondary turbo controls boost, im gussing it uses the pre control as a sort of wastegate to bleed exhaust? unfortunatly now that i can hold my throttle 100% through the 1-2 shift (auto) i can now tell that my tranny is fried.. uugh.

reverus

btw with the both the precontrol and the wastegate control looped into the vac manifold i was getting max boost regardles of mbc settings, so pegging 15psi before i would lift for fear of critical engine damage.

RotaryEvolution

iTrader: (30)

both exhaust runners are semi tied together so the wastegate will dump exhaust from both turbos iirc, i really haven't looked at them that much before. if that isn't the case then the primary turbo dumping boost will eat up the secondary's boost after the charge control flapper opens and the second turbo comes online. think of it as air pushed out the primary turbo backwards(not really the case but it will severely eat up how much boost it produces).

reverus

jesus, no wonder we have trouble controlling boost with mods!!