Weird mac valve behavior

[mhiscott]

I have a '13 FRS with a turbo setup that was running at 9 psi using ecutek custom output to a 3 port infamous performance mac valve electronic boost control solenoid. It worked fine for quite a while.

Back a few weeks ago I did four hard track days in a row, racking up ~ 200 laps on the car. On the fourth day I noticed the boost had dropped from 9 psi to 7.

I figured either the turbo was giving out, or there was a boost leak. I tested for boost leaks and did notice there was more pressure escaping through the compressor housing to CHRA into the oil drain. I think the turbo took a bit of abuse with all the high temp 30+ minute track sessions, but it still seems to work fine other than the drop in peak boost. There is a decent bit of shaft play, but no oil burning or in the intake tract.

I next figured the MAC valve had stopped working, because the 7 psi I was getting after the 4th day at the track was identical to my WG spring pressure. I ran the car with the 3 port plugged in, and again with it unplugged, and the boost curve was identical.

Feeding 12v to the mac valve, it went from having ports 2 and 3 connected to ports 2 and 1, as it should. This pretty well confirmed to me that the 3 port still was operating fine.

Lastly, I popped on an old manual boost controller I had sitting around, and at only 1 or 2 turns in from the lowest setting had a solid 10-11 psi. Higher than I had the EBC setup for to begin with.

Does anyone know what gives here? Is it possible for a mac valve to still test normally with 12v applied, but not actually work properly with the duty cycle it is getting from the ECUTEK output? Nothing on the map changed... It's just like the 3 port is doing absolutely nothing now to raise the boost level from spring pressure....

[Spartarus]

Originally Posted by mhiscott

Does anyone know what gives here? Is it possible for a mac valve to still test normally with 12v applied, but not actually work properly with the duty cycle it is getting from the ECUTEK output? Nothing on the map changed... It's just like the 3 port is doing absolutely nothing now to raise the boost level from spring pressure....

Thanks for the thorough troubleshooting.

Sure there is. The only way I can see that happening is if the current from the duty cycle signal is never reaching the solenoid. Noticed the only thing you didn't mention checking was that custom output harness. Perhaps hook up a multimeter to the harness and rev the engine? Or drive it? either way, put it in boost and see if there's a pwm voltage applied.

Could have chafed, melted, bad wires to start, or simply come loose? Unrelated note, just simple curiosity, what wire gauge did you use?

[mhiscott]

I'm using the oem harness for the cpc solenoid. Metering the wires while running the car is one of the next troubleshooting steps, I just struggle to see how the oem wiring could give trouble on a harness this new.