E85,boost,what static compression
#1
E85,boost,what static compression
So we have to get back into the bottom end again - don't ask
After taking some advice and going with 8.5:1 pistons, now that we'll be in there again, we're second guessing that decision and thinking about going to 9:1. Head is slightly milled.
So what are the opinions with e85 and 18-20 lbs of boost?
Anyone can guess. Looking for experience to lead your comments.
After taking some advice and going with 8.5:1 pistons, now that we'll be in there again, we're second guessing that decision and thinking about going to 9:1. Head is slightly milled.
So what are the opinions with e85 and 18-20 lbs of boost?
Anyone can guess. Looking for experience to lead your comments.
#3
Full time e85. Don't want to give up all the timing. Definitely don't want interference . Originally were planning those type of numbers but the machinist got out some chart and did I some figuring and thought we'd be sorry even on e85. He recommended 9:1, but with the slightly milled head ordered the 8.5s.
#9
So is it theory or proven? Saying it's not detonation limited doesn't make sense. At some level of boost, it will detonate. I understand that combustion chamber design and other factors do come into play, but an octane calculator says 9:1 and 20psi requires 110 and 10:1 with 20psi requires 116. I also understand that ethanol has some cooling properties to it, but it's also only roughly 105 octane.
Who has actually run 10:1 or higher successfully on a BP?
Who has actually run 10:1 or higher successfully on a BP?
#10
You can even search and find it yourself actually.
I'm curious what "chart" your silly mechanic referenced to suggest 8.5:1 on e85. Id love to hear that reasoning.
So is it theory or proven? Saying it's not detonation limited doesn't make sense. At some level of boost, it will detonate. I understand that combustion chamber design and other factors do come into play, but an octane calculator says 9:1 and 20psi requires 110 and 10:1 with 20psi requires 116. I also understand that ethanol has some cooling properties to it, but it's also only roughly 105 octane.
Who has actually run 10:1 or higher successfully on a BP?
Who has actually run 10:1 or higher successfully on a BP?
Most recently I ran something like 22psi and 30* of timing on Ryans car and it took it and asked for more.
ran 22* and 14-16-18 on my old '00 (though that was 9:1)
and ran 25+psi on 11:1 on another local guys car
*edit: again, I'm not saying you're gonna have a terrible engine or not make power, but you're just throwing away a ton of response for no reason whatsoever.
#11
me. and dozens of people much smarter and better than me
Most recently I ran something like 22psi and 30* of timing on Ryans car and it took it and asked for more.
*edit: again, I'm not saying you're gonna have a terrible engine or not make power, but you're just throwing away a ton of response for no reason whatsoever.
#12
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My heavy boost experience is in EVO's, but in my last EVO I was running 30 psi of boost on E85 on the stock 8.8:1 pistons. Saying you need 8.5:1 on E85 in the low 20's boost pressure is just silly. Most EVO guys who do a build go at least 9.5:1 on gasoline and higher than that if they plane on E85.
Keith
Keith
#13
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I ran 3deg past MBT on an 8.6:1 motor on E85 at 17psi/350whp and never saw detonation. I had a conversation with eliminator77 years ago where he talked about his E85-specific bottom end, and IIRC he said it was 9.5:1 and he regretted not going higher. If I were building a dedicated E85 bottom end, it would be 10 or even 10.5:1.
#14
Motor and car are here, 12:1 turbo thread here.
12:1 E85 turbo build - Miata Turbo Forum - Turbo Kitten is watching you test compression.
Dann
12:1 E85 turbo build - Miata Turbo Forum - Turbo Kitten is watching you test compression.
Dann
#15
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It looks like SuperTech only offers 9:1 , 9.5:1 or 11:1 pistons for the 1.8L. Is there a 10:1 or 10.5:1 option that would be available for this application? This relates to a thread that I started recently, but also got varying responses.
#18
I am running 11:1 CR with 11psi of Rotrex boost. With a turbo that comes on harder/sooner I might opt to run less.
The whole CR/boost relationship comes down to being able to run ideal timing to get MBT. Having to back off boost or timing because of detonation means you went to far.
In other words:
Choose HP goals and back into boost/CR numbers.
Choose CR and run as much boost as possible to maintain ideal timing and settle for whatever that HP number turns out to be.
I have played with boosted applications on many cars. I have done low CR high boost and high compression low boost builds. I am currently leaning towards the high CR low boost builds. While not quite the excitement of a big boost rush they have an eagerness that can't be matched. Done right they feel like a big high compression NA motor.
The whole CR/boost relationship comes down to being able to run ideal timing to get MBT. Having to back off boost or timing because of detonation means you went to far.
In other words:
Choose HP goals and back into boost/CR numbers.
Choose CR and run as much boost as possible to maintain ideal timing and settle for whatever that HP number turns out to be.
I have played with boosted applications on many cars. I have done low CR high boost and high compression low boost builds. I am currently leaning towards the high CR low boost builds. While not quite the excitement of a big boost rush they have an eagerness that can't be matched. Done right they feel like a big high compression NA motor.