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tartar_sammich
Max Compression ratio on pump gas?


We have a 354 Hemi with 11:1 forged true pistons. Can we run it on pump gas? We are trying to save money and want to keep the pistons.
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on: Mon 13 of Jul, 2015 [04:53 UTC] reads: 10151

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330Topolino
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Re: Max Compression ratio on pump gas?
on: Mon 16 of Apr, 2018 [13:36 UTC] score: 0.00
> We have a 354 Hemi with 11:1 forged true pistons. Can we run it on pump gas? We are trying to save money and want to keep the pistons.

No personal experience (yet), but have heard from multiple sources that E85 allows for some significantly higher compression. Requires a much lower A/F ratio, so your mpg will be down. But runs cooler and will make more HP. It’s all a trade-off.

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George
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Re: Re: Max Compression ratio on pump gas?
on: Mon 16 of Apr, 2018 [16:18 UTC] score: 0.00
> No personal experience (yet), but have heard from multiple sources that E85 allows for some significantly higher compression. Requires a much lower A/F ratio, so your mpg will be down. But runs cooler and will make more HP. It’s all a trade-off.

Higher C/R because it has a higher octane rating, but the lower MPG (about 25% reportedly) is because E-85 simply doesn't have the energy (BTUs) in it that E-0 or E-10 has.

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330Topolino
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Re: Re: Re: Max Compression ratio on pump gas?
on: Mon 16 of Apr, 2018 [17:02 UTC] score: 0.00
> > No personal experience (yet), but have heard from multiple sources that E85 allows for some significantly higher compression. Requires a much lower A/F ratio, so your mpg will be down. But runs cooler and will make more HP. It’s all a trade-off.
>
> Higher C/R because it has a higher octane rating, but the lower MPG (about 25% reportedly) is because E-85 simply doesn't have the energy (BTUs) in it that E-0 or E-10 has.

BTU difference is true on gallon for gallon basis, hence the lower MPG. On the other hand, factoring in the lower F/A ratio you can make more HP. Like I said, it’s a trade off.

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Webmaster
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Re: Max Compression ratio on pump gas?
on: Mon 10 of Aug, 2015 [12:56 UTC] score: 0.00
Tarter: With cast iron heads, they like 10 to 1 but over that and you will have detonation problems. I do run 11 to 1 with our aluminum heads. Good luck,
Bob



> We have a 354 Hemi with 11:1 forged true pistons. Can we run it on pump gas? We are trying to save money and want to keep the pistons.

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moparlee
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Re: Re: Max Compression ratio on pump gas?
on: Mon 07 of Aug, 2017 [12:44 UTC] score: 0.00
> Tarter: With cast iron heads, they like 10 to 1 but over that and you will have detonation problems. I do run 11 to 1 with our aluminum heads. Good luck,
> Bob

Hmmmmm.....good to know.

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George
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Re: Max Compression ratio on pump gas?
on: Mon 13 of Jul, 2015 [22:35 UTC] score: 0.00
The general rule of thumb is you can run a 11:1 hemi on the same octane that a 10:1 wedge engine would need.

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hemipwr202
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Re: Max Compression ratio on pump gas?
on: Mon 13 of Jul, 2015 [22:31 UTC] score: 0.00
> Likely gonna have to use sonoco racing fuel sold at the pumps 100+ octane, I think 107. Up here in Wisconsin, it is sold at Kwik Tripand Bs that are fairly cloe to the race tracks.

I'm running 10:1 in a 241 Dodge and have to run Premium the higher the octane the better. 91 to 93.

Todd


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