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Old 06-13-2018, 12:56 PM   #7 (permalink)
Cyborg ECU
California98Civic's Avatar
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 4,891

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 59.89 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 1,710
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Originally Posted by Baltothewolf View Post
Well of course you are getting better mpg now, your valvetrain was probably worn, now it's basically a brand new head with way less leakdown. Also, I'm going to assume you had the head shaved to make it flat again? If so, that's also a small compression bump. Not much, but everything counts I guess.
Yes to all of this. I was a little disappointed at the machinist didn't seem to do a check for warpage before flattening. But he did a great job. I'd recommend them to anyone. But you asking these questions reminded me that there's still another modification that I forgot to mention in the original post for this thread. I set the valve lash in a way that was meant to improve internal EGR. The valve lash is still all set within specs but the exhaust valves are open for as little as possible within spec and the intake valves are open for as long as possible within spec.

See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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