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...I know in a NA application alcohol likes high compression, but how does it work with lower CR's like 10-11:1. A buddy was asking and I don't have a clue.
 

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...I know in a NA application alcohol likes high compression, but how does it work with lower CR's like 10-11:1. A buddy was asking and I don't have a clue.

Yes It like's higher comp, but will run on 10-1 just fine,, after you 362 run's 9.60 at 107 with a 10-1 408cid,,not bad !!!! .....Eric:)hand
 

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So with our panel of resident experts, this is all we can come up with? I guess a few guys must be out of town right now. I am the friend Poffy was refering to about the question, so not being certain, I can only guess. I have seen charts, and have them somewhere, the question is where. I want to say that in the 10:1 to 12:1 range every full point of compression was worth approximately a 5% gain in power. As the compression goes up, the gains start to go down. Anyone???
 

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O.K. I found one of my charts, I was off a bit. One example from the chart would be going from 10:1 to 14:1 you could expect around a 5% gain. To qoute something from the source..." As the compression ratio goes up, there is less power gain from each point increase. For example, raising compression ratio from 8.0:1 to 9.0:1 nets greater power increase than a similar power increase from 11.0:1 to 12.0:1 ( 2% versus 1.3% increase in power)." I imagine these figures are based on gasoline though, and not sure how to adjust for alcohol.
 

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O.K. I found one of my charts, I was off a bit. One example from the chart would be going from 10:1 to 14:1 you could expect around a 5% gain. To qoute something from the source..." As the compression ratio goes up, there is less power gain from each point increase. For example, raising compression ratio from 8.0:1 to 9.0:1 nets greater power increase than a similar power increase from 11.0:1 to 12.0:1 ( 2% versus 1.3% increase in power)." I imagine these figures are based on gasoline though, and not sure how to adjust for alcohol.
YEAH , this is true , So If you have a choice in the piston ( new build ) and want max power, this is one case that more is better ,,, If you have a 10-1 motor and want to just change fuel , the alcohol will give you a lil hp and MORE torque , Are you trying to figure at what point of compression you will not gain enough to make it worth the $ to get custom made part's ?? so enough of the mind reading -What is your real question ??..........E:)hand
 

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Maybe this will help.
Local guy....cole flat 468 N/A deal on race gas....12 to 1 compression.....runs 108 mph at local lake (4500 ft. static). Wants to go to alky cause tired of hassle buying race gas and has alky hydro anyway.
So we do the carbs and larger fuel pump for alky. After tuning with pyrometer...the thing needs 40 degrees to run it's best of 109 mph....but the guy swears it leaves harder than with gas.
Now the only reason I went along with the swap is that he had alky for the hydro already.....I have one hell of a carb guy here in town I feel is the best of the best.....and I knew we would eventually go in there and change cam on the flat and as much compression as we could get in it for alcohol....and was curious how it would run against gas.
 

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so enough of the mind reading -What is your real question ??..........E:)hand
The real question is if you have a blown injected alcohol motor with compression somewhere between 10.0:1 and 11.0:1 and you pull the blower off, put a tunnel ram on it, and the injector hat back on, is it going to run like a turd because of the realatively mild compression, or will it still make some beans?
 

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Maybe this will help.
Local guy....cole flat 468 N/A deal on race gas....12 to 1 compression.....runs 108 mph at local lake (4500 ft. static). Wants to go to alky cause tired of hassle buying race gas and has alky hydro anyway.
So we do the carbs and larger fuel pump for alky. After tuning with pyrometer...the thing needs 40 degrees to run it's best of 109 mph....but the guy swears it leaves harder than with gas.
Now the only reason I went along with the swap is that he had alky for the hydro already.....I have one hell of a carb guy here in town I feel is the best of the best.....and I knew we would eventually go in there and change cam on the flat and as much compression as we could get in it for alcohol....and was curious how it would run against gas.
OK , not trying to say your carb guy is not good, but I dont think( my opinion ) that carb's work well with alky, alky work's better with injection,( something about the amount of fuel trying to be drawn in verses being sprayed in under pressure ) , now the way gas burn's and alky burn's is the reason for more torque, ( gas go's boom ,and the resulted pressure created pushes the piston down, ALky light's off and continue's to expand the whole travel of the piston (and then some )like all the way out the pipe ))( that is why a alky motor is louder ) , which create's a lot more torque , ( that is why the driver is saying it leaves harder ) , Again just my opinion I think you might of gained a little mph if you would have used injection , does that help any ,, ..................Eric:)hand
 

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The real question is if you have a blown injected alcohol motor with compression somewhere between 10.0:1 and 11.0:1 and you pull the blower off, put a tunnel ram on it, and the injector hat back on, is it going to run like a turd because of the realatively mild compression, or will it still make some beans?
It will still make some bean's (but if you were used to the blower motor) you cant compare the 2,, ...............E

the hat on a tunnel ram I have heard run's well......
 

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I have heard though that the tune up on the injection isn't as forgiving as a carb, when elevations and temps change?
 

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I have heard though that the tune up on the injection isn't as forgiving as a carb, when elevations and temps change?
Well not sure about gas and carb's (dont run either ) , But I can say that alky is very forgiving,,( you can run on the rich side and still make power ) but on gas if it get's rich it run's like a turd and foul's plug's ...........Eric:)hand
 

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I think the combination of alky and injection is very forgiving.............E:)
 

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Hey Todd

there is a guy ( his first name is mike , cant remember his last name right now ) running a tunnel ram injection on alky , say's he love's it , just talked to him at cfw on new yr day, He would be a good guy to talk to ,, ........E:)hand
 

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OK , not trying to say your carb guy is not good, but I dont think( my opinion ) that carb's work well with alky, alky work's better with injection,( something about the amount of fuel trying to be drawn in verses being sprayed in under pressure ) , now the way gas burn's and alky burn's is the reason for more torque, ( gas go's boom ,and the resulted pressure created pushes the piston down, ALky light's off and continue's to expand the whole travel of the piston (and then some )like all the way out the pipe ))( that is why a alky motor is louder ) , which create's a lot more torque , ( that is why the driver is saying it leaves harder ) , Again just my opinion I think you might of gained a little mph if you would have used injection , does that help any ,, ..................Eric:)hand
Ok...first....let me say I am not a carb guy and prefer injection. But I have been around long enough to not put injection on some guys who will not follow through with tuning. All you have when you do that is "unhappy everybody."

The carb guy I speak of....is just good enough that when I end up tuned I am within 1 jet size of where he started. Many times I don't even adjust the idle screws...etc. I am saying if he does it then my job is easy. He's done this every damn time....from blown to unblown and gas to alcohol....whatever.

I have run injected alcohol vs injected race gas back in PGF and super eliminator days and my experience was......slight e.t..gain.....left harder....but otherwise about the same.
I will say my opinion....and it is just that...is that the injector on alcohol would leave harder than the carb deal.
I think everybody knows here my preferred fuel is alcohol....and as much compression as can be had when I use it.
 

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O.K. I found one of my charts, I was off a bit. One example from the chart would be going from 10:1 to 14:1 you could expect around a 5% gain. To qoute something from the source..." As the compression ratio goes up, there is less power gain from each point increase. For example, raising compression ratio from 8.0:1 to 9.0:1 nets greater power increase than a similar power increase from 11.0:1 to 12.0:1 ( 2% versus 1.3% increase in power)." I imagine these figures are based on gasoline though, and not sure how to adjust for alcohol.
I'd say from 10:1 to 12:1 you'd get 4% per point (8% total) on a well built engine( good air flow and cam) beyound 12:1 the power increase will fall off. Say 12:1-14:1 wouldn't net an 8% increase maybe only 5-6% increase.

S CP :D
 

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One thing that comes to mind for me is alky at a lower compression might be much more sensitive to engine heat. Warming the engine and making sure it is good and warm would be much more critical to efficient burn since the compression ratio itself won't be compressing it and helping.

Paul
 
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