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Compression ratio for flex fuel::::[

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Old 03-04-2018, 09:03 PM
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427V8BB
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Default Compression ratio for flex fuel::::[

Hey guys just out of curiosity what compression do you guys run out there being on e85 primarily. lets say if I ran out of e85 and had to use 91 octane what compression would be safe for that but still have a high enough compression to use the e85s octane.

thanks
Old 03-04-2018, 09:46 PM
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Turbo2L
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I'm at 12.4:1 and I wish I would've gone 13.8:1. I run on 93 without issue when e85 is not available.
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Old 03-04-2018, 10:38 PM
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realcanuk
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Originally Posted by 427V8BB
Hey guys just out of curiosity what compression do you guys run out there being on e85 primarily. lets say if I ran out of e85 and had to use 91 octane what compression would be safe for that but still have a high enough compression to use the e85s octane.

thanks
Unanswerable question without details..... people cant really guys if your boosted, N/A, stock, built, etc, etc.
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Old 03-05-2018, 08:32 AM
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jayyyw
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Originally Posted by Turbo2L
I'm at 12.4:1 and I wish I would've gone 13.8:1. I run on 93 without issue when e85 is not available.
About the same here. We were able to max out my 93 octane tune, timing wise.
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Old 03-18-2018, 12:59 PM
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LLSR N-A 14.1 to 1 run E85 full time but when necessary will get 93 octane to make it to the E85 pump no problems at all just see extra 10 degrees on the engine temps but no overheating or pre-ignition will prob run pretty good on gas but haven't try it nor will I be interested.
Old 03-23-2018, 12:48 AM
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handyandy1496
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e-85 is 105 octane. Max EFECTIVE cr is 10.5. per Wallace racing.
Old 03-23-2018, 11:04 AM
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old motorhead
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Not just static compression ratio at play here. Dynamic compression ratio is an important consideration also. On an 11:1 static compression ratio LS3, the dynamic compression ratio can go from under 8:1 to over 9:1 depending on the camshaft employed. As realcanuck said, there's a whole lot of other variables that need to be taken into consideration too. Just stating the one CR or another is good is just a WAG without knowing the other variables.
Old 03-23-2018, 02:05 PM
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Suns_PSD
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Seems like a question for a good tuner and engine builder.

My engine is flex fuel but I had my head guy give me a compression bump but told him I wanted to be able to run 91 Octane in a pinch. We have 93 here in TX but I want the option of selling it out of state or doing a road trip up the Western coast or something.

The Flex fuel is great during the summer months as it really prevents that really fluffy engine feeling you get on a 105 degree day. In the winter the flex fuel tune is so snappy that traction is really an issue, so I just run 93.

Good luck.
Old 03-23-2018, 10:17 PM
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Originally Posted by handyandy1496
e-85 is 105 octane. Max EFECTIVE cr is 10.5. per Wallace racing.
Yeah true story and midgets are 6 foot 4

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