100 Octane and Compression Ratios

[toolman617]

I am doing a project for my junior year of college this semester, and pending funding, I will be studying the effects of ethanol fuels in engines. I am wanting to convert a car over to ethanol use (using my '89 Stang). Depending on how much funding I can get, I will hopefully be building an engine around the ethanol fuel (around 100 octane). My question is this - with 100 octane fuel and the right components, what compression ratio can I get up to? I know that if I get up into some higher compression ratios, I may need to start with a good block (possibly a nice 4-bolt main) and get all forged components, which again goes back to the whole funding question. As of right now though, I am just looking into what compression ratios can be run with an engine built around the use of 100 octane fuel in mind, so any input would be appreciated. Thanks!

 

[$uperstang]

10:1 or higher

 

[CooterXJ]

I have 11.25:1 and it doesnt care for 93 pump gas too much. But it loves it when i fill the fuel with 110 race fuel (it ends up being about a 50/50 mix of 93 and 110). I do have a 150 shot in the car but i have yet to use it.

 

[Blk91stang]

I'm running static 12.75:1 compression with 93 Exxon Pump gas with no probkems (EVERY engine builder told me I would detonate like CRAZY, yet have never had it detonate EVER! Even on a 150 shot of nitrous.. go figure) I have a timing controller in the car to back the timing down a little but I think you should get away with 13:1 compression on 100 octane pretty easily.

Keep two things in mind, compression builds a lot of HEAT and is very hard on the starter. Be prepared to buy a $300 starter along with a TOP NOTCH cooling system with the highest CFM electric fan you can fit in there.

Good Luck with your project!!

 

[toolman617]

Ok thanks for the input. Depending on how much funding I get for the project, I may just try and push the compression ratio as much as possible until I get detonation (and then just replace and damaged parts). I know there are several ways to increase compression, but what's the easiest?

 

[Bob Hill]

I'm no fuel engineer, but I recall ethanol can be run with a compression ratio of like 14:1. Conversely it must be run a lot richer than gasoline. Where gas likes and AFR of 14.7:1 for ideal combustion, alcohol wants like 9 or 10:1

Bottom line is you can run way more compression but you'll use more fuel.

 

[toolman617]

Yea, I knew about the fuel consumption, but thanks . I actually did a small (6 page) research paper on ethanol use in cars, so I know the basics of it. Just out of curiousity, where did you hear that it could be run at 14:1? If I did run an engine at that high of a compression ratio, would I need a quite hefty block (like the FRPP Siamese bore blocks)?? That much compression has to put a ton of pressure on the block and all the components. I guess it would most likely go without saying that all components would need to be forged, right?

 

[bimmertech]

8:1 compression with 20lbs of boost!!!!!

 

[toolman617]

lol...if only...

Somehow I just don't think that my prof or anyone I get to fund me would take too kindly to that...