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Hey everybody, I have a stock block JDM b20b with a GSR head milled .020, OEM cam gears, BC stage 1 cams (super close to ITR cam specs) 70mm TB, skunk2 intake manifold, 4-1 header (not sure on brand name), 2.5” piping all the way back, catless with a resonator, Vibrant 2.5 muffler, etc
What my issue is that compared to other dynos I’ve seen with b20vtecs with a similar setup as mine, it seems like they have a linear powerband that pulls all the way past 8k. However, mine seems to have an issue pulling past 7.5k, and just wants to drop off. I’ve had this car dyno’d before in roughly 40 degree weather this past winter and made 181whp with the factory GSR cams. The problem was power just fell off at 7,500. I replaced them with the BC stage 1 cams and had it retuned to only make 176whp (given it was a LOT warmer, 85ish degrees or so). I understand the difference in ambient temps makes a huge difference in power, but shouldn’t I had gained a good linear powerband instead of still dropping off on power at right around the same RPM?
Im just a little baffled by this and was seeing if anyone had an issue similar to mine and had a solution to gain their upper power band back. Thanks!
Recent dyno tune
Showing where my powerband seems to be struggling around 7500 rpms
Last edited by Bteggy89; Jun 12, 2018 at 08:50 AM.
Reason: More information
I read your post and then looked at your dyno, not nearly the "drop off" that I was expecting.
First thing, you didn't mention which JDM b20b block, low, medium or high compression...
Did you degree the cams?
Your car looks to be pulling well to about 8k, I don't know how much more you could want or expect from stock b20b pistons/rods.
Now if you went forged rods/ pistons, 12:1 compression, bigger cams like pro2's, a real header and 3 inch exhaust, I would expect it to get closer to 225whp at 9000 rpms.
B20vtec top end power band issue
