I know most people say if you're going to the trouble to rebuild your engine, you should spend a little more (ok, a lot more) and go FI. However for curiosity's sake, if one was to do an NA build, how high could compression go so as to yield the best results from 93 octane?

I've heard that as bore size goes up, compression generally has to go down for best results. Though, I imagine there is room for comp. to go higher with 93 octane since our engines can safely run 89 octane (knock sensor pulls timing).

Anyone have ballpark estimates?

I'd love to see (and hear) an NA engine revving to 8k rpm with higher compression. Engine management is probably the biggest challenge though...
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Jeff

 

Well a few Maxima guys are running with VQ30 heads + VQ35 bottom ends which is near 11.5:1 CR without issues on pump gas.

With your superior cooled long reach spark plug VQ35 heads plus dome'd pistons, you should be able to push it higher. However, you guys run far more timing advance, so that could be a limit.

 

Cool. What kind of redline did these guys go for? I assume not too high if they didn't rebuild. Also, how did they tune?

Thanks,
Jeff

 

I was just about to post this very same question. Ive been wondering about running 11.5:1 compression with 92 octane (thats all thats available here). Ive e mailed Technosquare and they say that have a re-flash for this kind of setup. Any other thoughts on this?

 

I know a couple tuners are working on NA rebuilds (to varying degrees). I'd love to see package options soon.

My reasoning on the NA build is this: Normally I would agree that FI is the way to go for the most cost effective method of increasing HP. However, on the Z it appears that you really have to rebuild to be safe with FI. It's luck of the draw if your car can handle even relatively low boost.

If you have to rebuild to safely run FI, then you might as well look at doing an NA-only rebuild. Wouldn't that be like half or nearly half the cost of going built with twin turbos?

I'm thinking that between higher compression, higher RPM, and increased flow, one would have an NA beast. Add the 350evo rear end gearing, and you probably wouldn't even miss the low end torque that will be lost due to poor flow at low RPM and increased valve spring resistance.

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Jeff

 

The reason that Im interested in an NA build up is that I have an extra motor. I can build it up without my car being torn down and when Im done just swap motors. Id like to do pistons, cams, headers, etc.