What would happen if I increase compression to 12.5:1? - Honda Civic Forum



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Old 4 Days Ago   #1
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What would happen if I increase compression to 12.5:1?

I know that I can put D17A7 (CNG) pistons in my D17A2 block to increase compression to 12.5:1, but I don’t think that anyone actually tried it on 93 octane pump gas. I Can use use 93 octane gas, but I’m not sure that 93 octane is enough for 12.5:1 compression. So my question is will it work? I really want to try it, but I don’t know what would happen, which unfortunately makes me want to try it more lol. I think it would either work great, or knock and not work. Also, IF it did work, would I gain a noticible amount of power? What do you think about this?
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Re: What would happen if I increase compression to 12.5:1?

I think if your gonna start messing with radical changes to the engine, your going to need a standalone ECU such has Ktuner (the experimental one im running) or Hondata to adjust fuel maps and timing.
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Re: What would happen if I increase compression to 12.5:1?

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I think if your gonna start messing with radical changes to the engine, your going to need a standalone ECU such has Ktuner (the experimental one im running) or Hondata to adjust fuel maps and timing.
What would happen if I donít?
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Re: What would happen if I increase compression to 12.5:1?

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What would happen if I donít?
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Re: What would happen if I increase compression to 12.5:1?

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img]https://cimg4.ibsrv.net/gimg/www.civicforums.com-vbulletin/800x600/80-8piston003_78af86c4fafba21134f6685ddfcd0e835932ca1 d.jpg[/img][img]https://cimg7.ibsrv.net/gimg/www.civicforums.com-vbulletin/1536x1024/80-detonationfailure01_03a270f851b517e404e2053cbfe20f 4612ec4d88.jpg[/img
Why wouldn’t the knock sensor protect the engine?

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Re: What would happen if I increase compression to 12.5:1?

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but I’m not sure that 93 octane is enough for 12.5:1 compression.
Jet fuel is in the 100+ octane range, isn't it?
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Why wouldn’t the knock sensor protect the engine?
Octane and timing aren't the only factors that lead to or prevent detonation
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Re: What would happen if I increase compression to 12.5:1?

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Jet fuel is in the 100+ octane range, isn't it?
Octane and timing aren't the only factors that lead to or prevent detonation
Isnít E85 105 octane or something? That would certainly be enough. If I could afford to convert to it, which I canít. Jet fuel and race fuel is not an option.
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Re: What would happen if I increase compression to 12.5:1?

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Isnít E85
Did you learn all about stoichiometry yet?

How much more fuel (injector) delivery do you have to have available in order to safely run E-85 without going too lean??
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Re: What would happen if I increase compression to 12.5:1?

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Did you learn all about stoichiometry yet?

How much more fuel (injector) delivery do you have to have available in order to safely run E-85 without going too lean??
I said “If I could afford to convert to it, which I can’t.”, meaning that I know that I can’t just fill it up with E85 and be good to go. And yes, I did learn about stoichiometry.
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Re: What would happen if I increase compression to 12.5:1?

I asked that, along with other comments about compression and timing because a lean condition can cause detonation too.
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Re: What would happen if I increase compression to 12.5:1?

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I asked that, along with other comments about compression and timing because a lean condition can cause detonation too.
I see. Thank you for explaining.
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Re: What would happen if I increase compression to 12.5:1?

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Originally Posted by D17VTECPOWER View Post
Isnít E85 105 octane or something? That would certainly be enough. If I could afford to convert to it, which I canít. Jet fuel and race fuel is not an option.
the problem with alcohol is the acidity, it will eat away seals, etc.
Also, low calorific content, need much more fuel per air.
I am from a country that at some point in time 95% of new cars were alcohol, so i should know that.
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Re: What would happen if I increase compression to 12.5:1?

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the problem with alcohol is the acidity, it will eat away seals, etc.
Also, low calorific content, need much more fuel per air.
I am from a country that at some point in time 95% of new cars were alcohol, so i should know that.
You're right about low energy content and acidity. I believe that E85 can be a viable fuel though.
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Re: What would happen if I increase compression to 12.5:1?

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Did you learn all about stoichiometry yet?
You have made about 50 different threads so I'll just stick these thoughts in this thread here
(I've been considering consolidating all your posts into a single thread too )



Stoichiometry isn't the only factor to consider, but I figured it to be a starting point if you want to educate yourself.
I should have asked if you figured out some ideal AF ratios for maximum power using various fuels too.

The gasoline 14.7:1 stoich is not ideal for power, nor economy....It's ideal for emissions. The best balance and control of HC/CO/NOx emissions occurs at this ratio....that's why they make engines run at that ratio or as close as they can to it during low demand conditions.




Best power with gasoline is achieved at what, 12.5:1 (?) and an engine can be run extremely lean, 20:1 and beyond....but only in certain conditions.. Honda marketed some cars with engines designed to run that lean and they could get great fuel economy in the right conditions.

Alky ~97% pure Ethyl Alcohol, 9:1 ratio for stoich, probably 7:1 for power..... (Methyl Alcohol has similar properties, 5:1-6.1 ratio, and is even more corrosive) needs twice as much fuel or more to make the same power because it has half the heat energy of gasoline, it burns half as fast as gas so you have to almost double the ignition timing. You can run very high compression on alky to take advantage of the higher octane.
Cooling system performance becomes a little less critical because it burns so cool

Alky engines do not run great cold nor run well in very cold climates.

Add in....Alcohols are hygroscopic, they absorb moisture....which changes their properties, stability, and shelf life

Plenty of people run E85 in turbo and S/C applications with few or no mods to the fuel system components (other than fatter injectors), because most of todays vehicles are designed to tolerate some amount alcohol in the fuels.
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