E85 and boost, what compression ratio could I run? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-08-2016, 04:04 PM   #21
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12.5 or more if you can find the pistons
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Ive got 2 builds at just under 12:1 at over 25psi.

Both are awesome and not even close to knock.

Dann
Thanks. I was thinking around 12:1 or so if I make the switch.

Dann, how much over 25psi? 26, 30, more?
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Old 08-09-2016, 02:43 AM   #22
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Yeah, you can run way more.

19kpa cruise should be 40*
taper to
100kpa should be at least 27-30*
taper to
230kpa 16* is ok but should not be dropping, should be ramping up to redline, to at least 20*

Assuming built engine, competent setup, and at least e70 actual in tank, preferably 80+
Added some timing and smoothed it out a little more. Only briefly ran this map being cautious looking for any signs of knock but I didn't hear any and the logs dont show any more noise than the first map. Definitely pulled much harder and actually got rid of my little stumble/misfire at higher rpm and high boost. I have been trying to figure out what was causing that and couldn't come up with anything. I couldn't imagine 14 degrees or so of timing up top would be to retarded for it to pull cleanly but maybe so. 18psi does this table look a little better for a 10.5:1 high boost e85 engine? Yes its built with supporting mods and at least e70 in the tank. EGT also appeared to drop 100-150 degrees or so in cruise but need to drive around more to be 100% sure



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Old 08-09-2016, 05:24 AM   #23
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Much better.
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Old 08-09-2016, 05:25 AM   #24
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Thanks. I was thinking around 12:1 or so if I make the switch.

Dann, how much over 25psi? 26, 30, more?
Yeah 26-27

I didnt get to the tuning laptop today also guys
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Old 08-09-2016, 05:50 AM   #25
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Yeah 26-27

I didnt get to the tuning laptop today also guys
Bummer. I'm curious to see your map. You said you run 20 degrees at 25psi? So your map still must be considerably higher than my second one
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Old 08-09-2016, 07:07 AM   #26
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Maybe, Im just picking numbers by memory.

Ill show you the exact map.

Dann
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Old 08-09-2016, 09:23 AM   #27
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Yep better, and make sure your AFR's aren't dipping below 11.8 or you might get misfires from that too. You've still room for more advance too, this is on the conservative side
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Old 08-09-2016, 09:41 AM   #28
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Yep better, and make sure your AFR's aren't dipping below 11.8 or you might get misfires from that too. You've still room for more advance too, this is on the conservative side
Really? Damn e85 must really be some magical unicorn gizz. It only takes 11.8 to be rich enough to misfire? I figured it was closer to 11. Because it's definitely dropping below 11.8 at some points. It's already pulling much cleaner and harder so I'll keep playing with it. I'd still like to see what other people are running
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Old 08-09-2016, 09:53 AM   #29
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nah it's probably fine at 11.8, but once you start dippin lower by too much, you'll start losing spark. you're pumping ~30% more of the stuff into your cylinders, it overwhelms the spark
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Old 08-09-2016, 09:56 AM   #30
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Even while running boss d585 coils and a reasonable spark plug gap?
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Old 08-09-2016, 10:01 AM   #31
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with those you're likely fine, but I'd still run 12:1 on the dot cause it should be a wee bit faster and waste less fuel.
On Ryan's built 1.6 we could only go up to 21-22psi due to weak spark, but we still ran 20* midrange tapering up to 30* up top. that car put down 360whp on a 1.6 and a log manifold and a chinacharger. we've done BP4W's similarly and it was over 400whp.

the stuff is pretty nuts
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Old 08-09-2016, 10:05 PM   #32
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Pat I think you're capable enough that I can remind you to disregard static, and focus on dynamic compression ratio. If you **** up and end up with too much static, so you have to pull so much spark it makes less power fix it is just a cam timing adjustment away.
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Old 08-10-2016, 10:30 PM   #33
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Pat I think you're capable enough that I can remind you to disregard static, and focus on dynamic compression ratio. If you **** up and end up with too much static, so you have to pull so much spark it makes less power fix it is just a cam timing adjustment away.
I was just wondering what everyone thought would be doable. Not a lot of high comp, high boost builds in miataland. I haven't looked, but I'm sure there's some folks in other 4cylinder platforms doing it, probably evos and STIs if I had to guess.

I run 17* @ 38 PSI with no knock. Not going higher till I get it on a dyno.
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