Crazy boost readings with e30 bm3 stage 2 ots

[Z4m40i]

Hi everyone,

new to the forum, but active on Bimmerpost. Unfortunately the mod scene for the z4 is black badging and window tinting with that crowd.

anywho here are the facts:
-2020 bmw z4 m40i
-BM3 OTS stage 2, e30 + 91ACN fuel
- AA dp, exhaust, intake.

installed BM3 flex fuel kit earlier today and just did it’s first fill with corn. Did some WOT pulls, but manually shifted before redline just to work up to the power/make sure I don’t grenade anything.

car feels and sounds great. Pulls strong with nothing out of the ordinary.. except the amount of boost. From the handful of logs I’ve seen, it looks like most people with similar setups are doing low to mid 20s for boost with ethanol. Before ethanol, my car was logging those boost numbers. But now it’s saying it’s in the 30s. Both MAP and prethrottle boost have similar numbers.

I’d imagine the turbo is well out of its efficiency range, but IATs are still looking good. Any thoughts on this?

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[black_sedan]

doubt your pressure is in the 30 psi range. Subtract 14.7 and that’s your boost minus atmospheric pressure. If you subtract the target boost with 14.7, thats right around 22psi.

 

[Thraxbert]

+1 PSIA vs PSIG.

 

[Z4m40i]

Thanks for the reply!

that sounds very reasonable; although I did double check my settings, and my readout settings for pressure is set as “relative” vs absolute. I’m under the impression that “absolute” would not correct for atmospheric pressure- but this is out of my wheelhouse.

 

[razorlab]

Thanks for the reply!

that sounds very reasonable; although I did double check my settings, and my readout settings for pressure is set as “relative” vs absolute. I’m under the impression that “absolute” would not correct for atmospheric pressure- but this is out of my wheelhouse.

Contact bm3. I had the same issue even when set correctly. They had to do some updates to their software.

 

[Z4m40i]

Contact bm3. I had the same issue even when set correctly. They had to do some updates to their software.

thank you for sharing your experience. @black_sedan reply actually lead me to an old post you made. This seems to be the right direction!
Obviously off putting when the screen shot of my data log shows “psig”

 

[i3igpete]

Obviously off putting when the screen shot of my data log shows “psig”

i suspected that it was a unit labelling bug too, but wanted someone with hands on experience to confirm. sometimes no info is better than bad info.

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