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Old 05-26-2008, 06:02 PM   #1 (permalink)
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Beater Deluxe v2.0 - '89 Honda Civic DX
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Any engine builders here?

I've been trading tall tales with one of my ex-Honda buddies, picking his brain about building an engine specifically for efficiency. I'm a fair wrench but not a professional engine builder or machinist, so I found this a bit interesting. Be forewarned it's couched in Honda jargon:

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a few years back i built a d16a6 bottom end with PM3 pistons in it @ .008" piston to wall, yes, 8thousandths. they stuck out about .028" and rocked quite a bit.. were a hair on the clacky side but with new rings and rough hone/hard breakin it burned no oil whatsoever. 230PSI cranking compression with 3% leakdown. the head required opening up the quench pad depth to extend out to the bore diameter. or you could chuck the pistons in a lathe and bevel the compression height edge to get around this.

anyways.. it was otherwise all stock, cam retarded about 6 degrees with a bunch of trial and error intakes where they were very long @ 2" diameter then flared to an abrupt 3" diameter for about 3" long before hitting the TB. that made great lowend without hindering top end at all. compression was low 10's.

it made incredible torque,, i had only one seat and used to haul 3 whole engines at a time all over new england.. it'd go 80 in 5th gear (that was with a STD 4speed converted to 5speed using an HF 5th so you couldnt get any longer of a tranny) right up hills passing cars.. or it'd go around town at 40 mph in 5th without bogging. was quite unbelieveable, probably my biggest success. beating the piss out of it got an average 36 MPG and babying got as good as 41mpg in a 4 door 88 civic. it also would run on 87 octane at 18:1 AFR without audible knock.

i really stand behind the PM3's.
Sounds interesting, I suspect he'd have gotten better peak mpg with the cam more towards the stock location.

Any thoughts?

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Old 05-26-2008, 06:58 PM   #2 (permalink)
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Engine building is really just redesigning an engine. Very real and large gains can be had from designing an engine for fuel economy vs power density. Just look at the Metro vs Metro XFI (small changes).

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