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'97 hatch
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Discussion Starter #1 (Edited)
OK, stuff's at the machine shop and I'm having to make the call. Running a z6 head/y7 bottom, obd2, stock ECU. Keep hearing 10:1 on 92-ish is safe, but I've been getting various advice from the NA guys.

What compression ratio would you guys shoot for? (leaning toward stock P2E .2 overbore pistons, getting the rest through decking)

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BY THE WAY.. should I be looking into milling the head or decking the block to achieve the little compression bump I'm looking for?

Searched and realized tighter quench is good, but didn't see any "one's better than the other" evidence.
 

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91 CRX Si
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I was between 10.75 and 11:1 last build and it was fine. Was running a "chipped" ebay ecu...lol Just ran premium fuel to be safe.
With a good tune I don't see why anyone couldn't run as much as 12:1 on pump gas.
 

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I think his question is using "stock brains" and in stock ECU, and from his post it is an OBD2, non programmable.
I know... My "chipped" ECU was little more than a stock ecu with the rev limiter removed.
 

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you can if you use the OBD2 cam gear and dizzy. Cam gear corrects the timing and dizzy uses the correct connector/signals(crank sensor in crank for OBD2 not Dizzy).
 

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considering you are stil at stock compresion, Id say you cna go from the stock 9.6 to 10:1 as long as you use good quality gas. 91 octane or higher.

Might help to slightly retard the distributor position for reliability. But hey, iuf its not pinging or knocking, no need for adjustment
 

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'97 hatch
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Discussion Starter #9
you can if you use the OBD2 cam gear and dizzy. Cam gear corrects the timing and dizzy uses the correct connector/signals(crank sensor in crank for OBD2 not Dizzy).
Yup, I've got the obd1 dizzy with a jumper harness. I'd heard you could run the z6 crank pulley and time this combo correctly.. is that an either/or thing for swapping the cam gear to y7/8? I'm being lazy.. I think there's a sticky on this, just didnt' know if you had first-hand experience.. plus I'm at work.:pinch:
 

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The cranksensor in teh distributor is what the ecu uses

the second crank sensor on the oil pump is simply used by the ecu to adjust timing.
 

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'97 hatch
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Discussion Starter #12
The state of North Carolina doesn't see fit for my obd2 chassis to run anything but obd2. Thought about air/fuel controller.

This is my daily and wasn't meant to be anything crazy, but I figure I'll learn and down the line find a good ef shell to go balls out on. My main goal is to get this one running for now.
 

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'97 hatch
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Discussion Starter #13
By the way.. should I be looking into milling the head or decking the block to achieve the little compression bump I'm looking for?

Searched and realized tighter quench is good, but didn't see any "one's better than the other" evidence.
 

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99 Hatch
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The safe compression question seems to be more confined by your ability to tune. If you run a 'air fuel' controller don't expect much. In that case I would keep comp down. I've been running 12.7:1 comp daily for about 6 months and have about `15 000km on my engine with no signs of issues. It took a while to get good power out of 94 and no knocking, but totally doable. If I were to have a perfect piston I would shoot for 12.3-12.5:1.
 

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'97 hatch
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Discussion Starter #17
The safe compression question seems to be more confined by your ability to tune. If you run a 'air fuel' controller don't expect much. In that case I would keep comp down. I've been running 12.7:1 comp daily for about 6 months and have about `15 000km on my engine with no signs of issues. It took a while to get good power out of 94 and no knocking, but totally doable. If I were to have a perfect piston I would shoot for 12.3-12.5:1.
That's part of the problem. (OBD2) May try air/fuel controller to experiment in the future, but I'm not expecting to make nasty NA power in the first place.

Trying to keep it simple at this point.
 

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Discussion Starter #19
Ugh. California. I leave OBD2 cars alone.
We've got a little more leeway here, but trust me, after all the reading I've done in the last year or so my next project will be pre-96.
 
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