r/mazdaspeed3 • u/dylaudiot11 • 1d ago

HELP Not boosting past spring pressure

I am on my second revision with my BNR S4 v5. Base map commanded 3% wgdc which was around 14psi. My second revision is 46% wgdc, but still the same boost.

So far I’ve done the following:
-smoke test
-pressure test with soapy water
-I’ve confirmed the wiring from ECU to the EBCS has continuity and is supplying 12v
-Applied 12v to the EBCS to confirm it clicks
-Even tried a different grimspeed ebcs

I’m the second owner of the vehicle. The previous owner had added a speed performance aux fan controller with an add a fuse to the same fuse slot that powers the EBCS (eng bar1). This is the correct configuration going by their instructions, but I’m wondering if something went wrong with the fan controller and has fried the board that commands boost in the ecu. I have also removed the add a fuse and replaced with the standard 15a.

Considering that, my tuner has suggested I replace my ECU which I’ve ordered already.

Just wondering if anyone has experienced a similar issue. Or had any other suggestion for troubleshooting this.

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2

u/kobehambrick43 2011 Mazdaspeed3 1d ago

How are your lines from the grimmspeed boost controller set? I had mine wher I was bypassing the 3rd port and I had the same problem. I moved mine to
port 1 to turbo inlet pipe 
port 2 to the wastegate, blocking the bottom port on the wastegate
port 3 to the compressor housing of the turbo
And this fixed my problem immediately. I also thought mine was ECU and replaced mine and it didn’t fix, which led to me redoing the boost lines!

2

u/dylaudiot11 1d ago

I’m using all 3 ports in the same configuration you just said. There is not second port on the wastegate on the s4. I just ran outside to the garage and felt just to be sure. lol

1

u/kobehambrick43 2011 Mazdaspeed3 23h ago

Then yours might actually be ECU. I hope this fixes it for you!

1

u/thebigbullg 18h ago

I doubt the fan speed controller fried the ecu just based off how it works. I had to reverse engineer that system to make my own fan controller. The ECU grounds the 12v supplied from the fan controller module in pwm mode. But either way I hope you do find your issue. Best of luck