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Old 01-18-2010, 12:58 AM   #1 (permalink)
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Join Date: Nov 2009
Location: Raleigh, NC
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D15Z1 build suggestions

Ok, I'm new to the economy thing but have been wanting to build a car that does +75mpg hwy for a while. My current 88 Civic did 57mpg with a cammed D15B VTEC and a VERY short transmission(70mph at 4000rpm). Anyways, I had owned two 88 CRX DXs prior and now I regret scrapping them.

Anyways, I got a hold of a D15Z1 that needs to be rebuild. Previous owner says valve seals were leaking so he had it replaced, changed it, and now it leaks more. He thinks it may be incorrect seals since the parts lady gave him ones that all look the same(little does he know the exhaust and intake use the same size). I think it's either the rings or PCV valve.

Anyways, I plan on swapping in TL1000RR or GSXR750 injectors and have them pointed towards the "primary valve" or the valve that stays open during VTEC-E mode. The injectors are 4-hole type and flow about 270cc at 3bar IIRC. I also have a 7lb flywheel currently on my D15B VTEC that I'll swap over(being replaced with even lighter multi-disc clutch setup) One thing I'm thinking about doing is swapping the pistons from my D15B VTEC and throwing them into the D15Z1. They're slightly dished and will bump compression up to about 11.5:1. The problem with the P08(D15B) pistons is they're not designed to promote swirl like the P07 pistons. Another thing I'm looking to do is extend the runners on my aftermarket header(Z1R header) or would it be better to build a custom one(maybe runners are to large in diameter?)

Would it be more beneficial to have a higher compression ratio that possibly results in higher cylinder pressures and a more complete burn vs. a swirl-flow setup that promotes the ability to run leaner? Any other suggestions to build this "beast" D15Z1?

PS: The stock ECU is ditched and replaced with a chipped P28 or P06 running Chrome along with a Innovate LC-1 wideband O2 sensor instead of the stock one.

btw, I don't have a chassis to put it in but looking for a CRX HF.

Thanks, Kevin

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