Bone stock car with stock intake and exhaust. Overboosting to around 13 psi on heavy throttle. All wastegate lines are attached to the actuator and solenoid and appear to be in good working order. Wastegate rod will move so wastegate not stuck closed. Have not checked wastegate solenoid functionality.

Could bad wastegate solenoid cause overboost? Bad ECU?

 

I dug into this a while back and basically argued that the "10-8-10" pattern is not the only acceptable boost pattern on a stock car. That was based on published stuff from Mazda. Nobody really has a bone stock properly running car with a ton of instrumentation on it to collect data. You can't easily take usable datalogs from a stock ECU.

https://www.rx7club.com/3rd-generati...n-myth-934461/

 

I agree! My 94 stock has always boosted around 12 to 13! Of course I am at a 4800ft altitude

 

Could also just be the gauge.

 

when my JDM was bone stock I use to see 14/12 psi regularly. 14/10/12

 

we used to see about 9.5psi +/- about 1psi on the first turbo, some of you guys that live where its colder might see more...

 

what year is your car? I thought the very first FDs were set to boost higher ( like up to 13) and in an effort to stop warranty claims Mazda dialed it back?

Do you have a very early build date?

 

With intake port matching, K&N drop in and a downpipe I could overwhelm the stock boost control system and hit overboost fuel cut in 4th/5th on the highway.

Fuel cut is only ~11 psi in some places on the stock ECU. You obviously want to stay away from that.

It is my understanding that the stock boost control system only works with a completely stock car. As in no flow mods. Correct me if I'm wrong, but the stock ECU does not change/adapt the duty cycling of the wastegate and precontrol solenoids based on feedback from any sensor: it is what it is.

My solution was to block off the solenoids and use a pair of manual boost controllers. One to the wastegate (post transition boost level) and one to the precontrol (pre transition control). A common problem and solution.

Your precontrol matters just as much as your wastegate.

If you want to maintain the solenoids, a power FC will allow you to change % duty cycling and get your boost under control.

 

the service manual diagrams shows some rudimentary feedback system, but yeah the stock boost control isn't very smart. It was developed in the late 80s/early 90s, remember.