ethanol compression ratios

[metro094]

Hi there. Anyone know where I can get data on the maximum compression ratios for using E85 in both an ignition engine and in diesel applications?

I'm considering modifying a turbo gas or turbo diesel engine for E85 and want to maximize efficiency so I can use the smallest possible block and displacement.

[cleanspeed1]

Depending on bore size, 12:1 - 15:1 static for naturally aspirated; 11:1 to 12:1 static for forced induction. Scania has a diesel based E100 motor that has 28:1 compression plus turbocharging.

E85Forum.com :: View topic - Realistic maximum compression ratio for E85?

[metro094]

Thanks for the info. The Scania engines look awesome, but they are so huge! I'm going to contact them to see if they will tell me whether going from e100 to e85 will drop me to 26:1 or 24:1, or what. I've seen some production cars using 22:1 with diesel, so I'm sure I'd need more than that to get e85 to burn right. I'll also ask them if they make anything small.

Anyone know if there is a big difference between the gas/turbo/turbodiesel 1.0 daihatsu engines like were used in the sprint and metro? I wonder if the gas metro engine is sturdy enough for high pressure.

[cleanspeed1]

The engine can handle more power, but it's abnormal combustion that destroys stuff.

With the small bore, high octane fuel, and low revs, you're not going to kill it unless you get the tune wrong ( highly unlikely, E85 is very forgiving ) or you are ham fisted with the build.

Get a set of pistons made to net you 15-16 to 1 static compression, a Metro XFI cam, and a Megasquirt or Emerald computer to get it tuned in.

[metro094]

Thanks again. So, it looks like you think I should keep with the spark plugs then instead of going the CI route. Should I also use the stock turbo unit, or is it too small for the e85 application? Maybe I could find one from an old chevy sprint turbo.

[cleanspeed1]

If you go the boost route, drop it to 14 to 1 and match it with the appropriate turbo.

If your going for big power, drop the compression a little more. If you are using the turbo to introduce more air into the system, go higher. The cam timing really decides it more than anything.