E85 Safe/Max Dynamic Comp Ratio

[fabr]

Yes,the cooling factor is the reason I'm running it. Have been using an old 2005,I believe, RCR nascar remnant with a slightly different cam in it for the last 4 years or so. Before that in a turbo hayabusa bike engined desert/dune car. Zero issues of any kind.

[bob460]

128 was also not given one second of consideration.

Yes it was the combo you did the cam and valvetrain for on YB. Love the well thought out naturally aspirated stuff that also gets driven and run on pump gas. Must’ve hit my head when I was young.

So no DCR and no 128??? Why did I have you do my valve train and camshaft again? hahaha

Didn't that engine get rebuilt recently, i wonder what happened to it?..........i think he used a different engine builder this time!

[EDC]

Didn't that engine get rebuilt recently, i wonder what happened to it?..........i think he used a different engine builder this time!

Went to a different block (iron vs aluminum) and it was machined for a 60mm camshaft core.

Same heads, intake, valvetrain and "basically" the same camshaft profile but with the 60mm and some .937 lifters.

Working on the clutch and suspension now.

[bob460]

Didn't that engine get rebuilt recently, i wonder what happened to it?..........i think he used a different engine builder this time!

Went to a different block (iron vs aluminum) and it was machined for a 60mm camshaft core.

Same heads, intake, valvetrain and "basically" the same camshaft profile but with the 60mm and some .937 lifters.

Working on the clutch and suspension now.

Thanks Ed, do you know if he will be changing to E85?

[Orr89rocz]

It is absolutely irrelevant to build a engine by dcr number or cranking compression numbers. It means nothing in a continual rpm changing engine. So is common thought a higher cranking number is better ,or going to make more power? In my procharger deal at 2500 plus hp and 30 lbs of boost we had a cam that had less dur on both sides,less overlap. It cranked at 225 lbs. We now have more dur on both sides,way more on ex side,more overlap and it makes more boost at same drive ratio and rpm. That cam cranks at 155 lbs. We now have more rpm ,more boost and getting rid of heat without hurting the engine. Dcr, cranking compression ,quench etc are so over rated and out dated terms to anyone building big power in std type 2 valves per hole ,wedge type head.

That seems odd and backwards. A blower at a fixed speed ratio should not make more boost if the engine is flowing more with the larger cam. Atleast thats how ive seen it On street stuff like lsa blower gm cars and whipples etc. Anytime you cam up it usually makes more power but less boost because boost is just a measure of backpressure in the induction system. Seems strange it could go the other way and make more boost? Guess theres more to it

[skinny z]

It is absolutely irrelevant to build a engine by dcr number or cranking compression numbers. It means nothing in a continual rpm changing engine. So is common thought a higher cranking number is better ,or going to make more power? In my procharger deal at 2500 plus hp and 30 lbs of boost we had a cam that had less dur on both sides,less overlap. It cranked at 225 lbs. We now have more dur on both sides,way more on ex side,more overlap and it makes more boost at same drive ratio and rpm. That cam cranks at 155 lbs. We now have more rpm ,more boost and getting rid of heat without hurting the engine. Dcr, cranking compression ,quench etc are so over rated and out dated terms to anyone building big power in std type 2 valves per hole ,wedge type head.

Are you comparing a boosted / nitrous engine to a NA "street" type deal?
Seems the boosted stuff is on another level altogether and that the more conventional "DCR and quench" thinking goes out the window. Same with cranking compression.
FWIW, it would seem it's not the number so much that matters but comparing apples to apples that counts. In my modest building, I've found a direct correlation between cranking compression and tolerance to detonation, all else being equal (IAT, coolant temperature, etc).
I wouldn't for a second though try to compare that to anything other than that specific platform.
Same goes for DCR (make of that what you will).
Your experience with high horsepower (2500!) leaves me in a position that I can't argue from as I've zero hands on with any of that.
My hat's off to you on that one.
Same goes to all of you who go that route.

[Dave B]

It is absolutely irrelevant to build a engine by dcr number or cranking compression numbers. It means nothing in a continual rpm changing engine. So is common thought a higher cranking number is better ,or going to make more power? In my procharger deal at 2500 plus hp and 30 lbs of boost we had a cam that had less dur on both sides,less overlap. It cranked at 225 lbs. We now have more dur on both sides,way more on ex side,more overlap and it makes more boost at same drive ratio and rpm. That cam cranks at 155 lbs. We now have more rpm ,more boost and getting rid of heat without hurting the engine. Dcr, cranking compression ,quench etc are so over rated and out dated terms to anyone building big power in std type 2 valves per hole ,wedge type head.

That seems odd and backwards. A blower at a fixed speed ratio should not make more boost if the engine is flowing more with the larger cam. Atleast thats how ive seen it On street stuff like lsa blower gm cars and whipples etc. Anytime you cam up it usually makes more power but less boost because boost is just a measure of backpressure in the induction system. Seems strange it could go the other way and make more boost? Guess theres more to it

Is the restriction in the blower, intake or the engine? It seems when you read articles or talk to cam companies they always suggest these small dur cams. We have saw many times that opening intake side longer let's in larger dense charge. Boost goes up and so does power,look how rpm effects power in a blower. Ask yourself what effect that has through rpm? Everyone says watch your ex side but if you are running big rpm and boost ,you have to get heat out of there or something is going to give. And it's a given that with small cam in supercharger app ,you run out of rpm. Trying to go past that just creates unwanted heat.

[Dave B]

As far as comparing blown to na on dcr, I am asking look at formula ,it asks for intake valve closing. My point is on pump e85 the amount of anti knock value it has doesn't matter as much when you can cool incoming air.
Look how much timing you can run with high pressure air out of a containment bottle at say 3400 psi. I really wonder why more people have not looked into or used this form of super charging?

[Dave B]

I was talking to my brothers and another buddy that built our 800 inch plus pulling deal. It was 17.85 to 1 comp . We ran e85-e93 in it na with a hat ,mfi injected. But most guys will say those big inch engines don't have enough cyl head to hurt themselves. But they are damn timing sensitive or you will split blocks up through mains and or see severe cap walk. Back to 14 to 1 street type engine op has. Make sure your afr is 12.5 on gas scale around peak trq and lean up 12.85 to 13 above that. You can having timing way up at cruise like any other fuel.Get your afr cleaned up or leaner at general cruise,2500 etc or you will have popping in exhaust from it being to fat.

[In-Tech]

Yes,
It's all about peak cyl pressure and heat... Depending on valve events, control the heat. Keep away from preignition and of course meth/eth is very susceptible to preignition if combustion process is not controlled. Meth/eth is very forgiving on the "tune" of the fuel. Ignition, not so much. Preignition can be incredibly rapid with meth/eth.

[Orr89rocz]

[
Is the restriction in the blower, intake or the engine? It seems when you read articles or talk to cam companies they always suggest these small dur cams. We have saw many times that opening intake side longer let's in larger dense charge. Boost goes up and so does power,look how rpm effects power in a blower. Ask yourself what effect that has through rpm? Everyone says watch your ex side but if you are running big rpm and boost ,you have to get heat out of there or something is going to give. And it's a given that with small cam in supercharger app ,you run out of rpm. Trying to go past that just creates unwanted heat.

Restriction is in the engine. I think im understanding your situation to mean you were not at max blower speed yet. And not at max compressor flow either. Hence more cam pulled engine higher and more blower speed was able to make more boost.

Bigger cam and more rpm is only good if the blower can continue to feed. What ive seen with smaller blower setups, usually blower limited so that you cant speed it up any more. Theres no more air flow or boost. When you cam that or put that blower on bigger engine with more head flow, usually see less boost

[Dave B]

[
Is the restriction in the blower, intake or the engine? It seems when you read articles or talk to cam companies they always suggest these small dur cams. We have saw many times that opening intake side longer let's in larger dense charge. Boost goes up and so does power,look how rpm effects power in a blower. Ask yourself what effect that has through rpm? Everyone says watch your ex side but if you are running big rpm and boost ,you have to get heat out of there or something is going to give. And it's a given that with small cam in supercharger app ,you run out of rpm. Trying to go past that just creates unwanted heat.

Restriction is in the engine. I think im understanding your situation to mean you were not at max blower speed yet. And not at max compressor flow either. Hence more cam pulled engine higher and more blower speed was able to make more boost.

Bigger cam and more rpm is only good if the blower can continue to feed. What ive seen with smaller blower setups, usually blower limited so that you cant speed it up any more. Theres no more air flow or boost. When you cam that or put that blower on bigger engine with more head flow, usually see less boost

Yes it can def go both ways.

[Dave B]

IMG_20230902_165752836.jpg

Here is a 358 sprint engine. It has the brodix spec heads. 15.85 to 1 comp . 700 hp na. I threw the blower off my c3 vette and gona spin it 1-1 . It will still make 13-15 lbs of boost I bet. The cam in it is very similar to the ops on intake closing side. It's 56@ .050. We were out on the interstate earlier cruising about 85 and stood into throttle about 2/3 of the way and lit the tires for 200 ft. I didn't have time to see what boost it making .lol. Tmaro it's going to car show. I'm sure it will get a complete beating to and from show.
I pulled a plug and it's pretty clean so I'm gona fatten the barrel a little. 95 degs out and thing never was over 185 degs.1.89 a gal for e85 to our shop. What more could you want.

[Dave B]

Throw above combo in dcr formula. It says dynamic comp 13.35.
Says with boost 25+. Says cranking comp 300 psi. I have a 300 psi guage and it bury it when I check it.

[Orr89rocz]

You are doing things i never heard anyone else do on that fuel. Hats off