Hi EvoM, I hope this is the right section to post this.

I'm fairly new to Evos and recently had my mostly stock Evo 9 tuned with a Grimmspeed 3-port BCS and 14psi Turbosmart wastegate actuator. The stock ECU was flashed with a Tephra v7 mod and was tuned to a peak boost pressure of 21psi. My Turbosmart WGA has half a hole of preload.

Ever since installing those components and tuning the car I've been noticing that there is a small boost fluctuation when boosting at wastegate pressure. On part throttle it'll make it's way up to around 15psi and fluctuate around 0.5psi in either direction. There is no fluctuation anywhere else, if you boost below 15psi it's steady. If you use more throttle and push past 15psi it's steady. At 21psi peak boost it's steady. It seems to be exclusively when I'm sitting on wastegate pressure.

My question is, would this be normal in this kind of setup? Are these little fluctuations due to the solenoid opening and closing? or perhaps the wastegate opening and closing slightly? You can feel the small boost fluctuations a little bit while it's happening but it's not super noticeable.

Thanks in advance for any input.

 

Took some video clips to demonstrate:

 

That looks pretty normal to me? I think you are probably between cells on the wastegate duty cycle table and it is causing that fluctuation.

Related question, why are you doing that? It seems like a weird way to drive the car?

 

Thanks! I appreciate the explanation. That would make sense now that you mention it.

To answer your question, I'm not exactly trying to do anything when it happens, I'm usually just accelerating at part-throttle. When I apply a certain amount of throttle it will just go to 15psi. To break past 15psi I need to apply a little more throttle. In this small throttle range I think it tends to sort of "catch" at the 15psi mark on the gauge, if that makes sense. That's also when it tends to start fluctuating a little like in the clip.

It's worth noting this is also my first turbo car so I'm still learning about what is/isn't normal.

 

Gotcha, so you saw it once by accident and then had questions, that makes more sense.

It looks pretty normal, it could probably be cleaned up with some tune updates but I don't think it matters.