E85 Safe/Max Dynamic Comp Ratio

[fabr]

Run it on One Ethanol R or similar. Much better and consistent ethanol

I buy drums of anhydrous E98 and blend to 85. Not going to get much more consistent than that. I never use pump e85.

High comp all motor i have no experience with. I would think 14:1 is cutting it close for the rpm range and application in my mind but I have no experience to say otherwise. What advantage does 14:1 give you over say 12:1 or 13:1? Id probably lean to less is more when considering endurance

I tend to agree and hence my question. I can get the compression down easily to 13:1 with a .060 gasket leaving me with approx .072 quench. I think the 20cc dish in the piston leaves an approx .300 wide quench for less than half the circumference. Will that small area of .072 quench likely cause any detonation issue? I have a gut feeling it will not.

[fabr]

Bullet 55mm roller. Dur@50 In.260 Ex269 Lobe Sep 108 @50 In opens 26-closes 54 @50Ex opens 66.5-closes 22.5 Gross lift 766-762

That 54 intake closing will make pretty good cyl pressure. I can't imagine a road race car being planked down like a drag car with a 15" tire.I also run sand with 37"x15" wide paddles that planks it pretty well. I would mach your deal up with gasket you are going to run and get a total pour ,then you will know exactly what your comp is.I know exactly what the comp is doing actual CCing with a burette.We have a drag race BBC with very similar cam events as yours. We are 15.85 and our e85 comes right from our local coop. It always checks 85-87.Like I said earlier get every sharp edge out of comb area.Yes Really flatten edges down or get clear rid of them. Our BBC we run a 3932 plug.I have saw when I get greedy with timing in decent air,38-39 degs it will just start to jag up the edges on plug strap. On our na stuff we are 18%more fuel with e85 over race gas.I log and tune rich.We go near 30% richer on our blown stuff. It's like pushing pump gas ,you must use good fasteners and head gaskets or you will find problems.Our blown stuff over 23 lbs we run top fuel hoops.We also run 11 range plugs.If you zoom in on plug you can see where edges are getting rough. When I'm there it's running hard.IMG_20221203_190319269.jpg

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[fabr]

image~2.jpgAnd here is plugs with 33 lbs boost and 25 deg timing. As you can see I got greedy. If my pistons were not contoured and edged I would of lost these 3 holes.

LOL,yep,a tad toasty.

[Dave B]

image~2.jpgAnd here is plugs with 33 lbs boost and 25 deg timing. As you can see I got greedy. If my pistons were not contoured and edged I would of lost these 3 holes.

LOL,yep,a tad toasty.

It's fixed now, I expect we will be able to run near 40 lbs of boost now. I made a cam change on the ex vents to get more heat out of it. We probably will take some e98 and mix it down to e93 area and let it eat

[fabr]

Endurance application. Anyone have experience in safe/max DCR using E85 N/A? 4" bore,4.125 stroke. I have 14:1 static and 10.88 effective. Am I safe? Thanks for any insight.

Why would you not use gasoline where you lose or use less fuel? You would need bigger cell to do same laps etc. Your weight bias would change considerably more over the event? Just wondering, I understand cost diff between race gas and e85

I run the e85 for the cost/cooling in extended running at 90-110 air temperatures.etc.. I use a lot of fuel even with race gas.I'll burn 10 gallons an hour per day and probably average 4 hours a day x30 or so days a year.1200 gallons a year roughly with race fuel being $5+ a gallon more that adds up real quick.I'd probably only use 900ish race gas. Off the top of my head I save somewhere around $4K a year. This is not a race buggy/prerunner. It is a toy. Regardless,I doubt I'd feel safe with race gas at 14:1 and my use. Maybe I'm wrong,I dunno.

[fabr]

My question is still only concerning the quench dimension and if with my limited quench detonation might be a concern. I believe I'll just have to try it and see.

[Dave B]

My question is still only concerning the quench dimension and if with my limited quench detonation might be a concern. I believe I'll just have to try it and see.

I'm not concerned with quench in most scenarios.i think it's way over rated. I have ran stuff all over the place quench wise. High or low etc. I'm more concerned with getting cam events to match my power range .I have only worked with a couple sand drag racers. It was like pulling, wheel speed is king. Imo you need to get away from your current cam. Move power band up. Add some dur and have it put on a 111-112 lsa. I think your fuel be easier to tune and your engine will make better power.

[fabr]

You could be right . Bullet specced the cam with all the info/usage/rpm range known to them. I'm running basically the same but slightly smaller cam overall in my RCR 360,repurposed/recammed nascar engine from 2005 era. It works very well. Only real difference is this engine is 427 with slightly longer cam events and basically same lift.I have no problem tuning whatever. Bottom line is the talk about too large quench got me spooked. I had never considered too large a quench clearance before and will likely ignore it now as in the past,run the .060 gasket,get the comp to 13:1 and run it.

[Orr89rocz]

image~2.jpgAnd here is plugs with 33 lbs boost and 25 deg timing. As you can see I got greedy. If my pistons were not contoured and edged I would of lost these 3 holes.

LOL,yep,a tad toasty.

It's fixed now, I expect we will be able to run near 40 lbs of boost now. I made a cam change on the ex vents to get more heat out of it. We probably will take some e98 and mix it down to e93 area and let it eat

What heat range was that and how much power? I ran something around 33 psi on my 555 bbc (3 bar map i pegged, estimated 33 psi based on dome pressure i was adding) and near 24-25 deg as well on E72 and my heat range 7 ngk were fine. Bit over 2000 hp. Ended up at 8 for safety but not sure i needed it. Afr was in the lower 11’s gas scale

[Dave B]

Iirc those plugs were 8s, we drove car to track and didn't put our colder plugs in. I got the cam from Morris and we were not going to run over 25 lbs boost. You know how that goes. On Dyno we ran it 27 deg and 9 plug and 30 lbs of boost. It made 2620 hp at 7700. We have made some changes since and I'm guessing it is 3000 area at 83-8400 area we shift. New cam I had made and valve spring change I'm hoping to see more boost and run it 8800 area

[Dave B]

Yes 14 to1 should be way safe, we run blower engs at 12.5 with 27 lbs of boost. It's like anything ,attention to detail in combustion area, ring seal yada yada.

Any pictures, videos, or build links? To be clear, you are saying you run E85 and 12.5:1 compression with 27 pounds of boost????? It seems rather unbelievable.E85 in my area averages around 100 octane. Maybe a touch higher. How can it support that? Harder to believe than your claim about 12.5:1 compression with iron head circle track stuff on pump gas. Just have a hard time believing some of your claims.

Here is a plug from this wknd,new cam helped a bunch. 43 lbs of boost ,ran it out @9200 rpm. E93 fuel mixed down from e98. We did mist some water in.But all and all still 12.5 to1 comp static.I don't look at what comp would be with that much boost ,but it would be way up there. We never get our afr fatter than 11.5 on gas scale and make good power up stairs in rpm in 12.3 afr area.I ran a 11 heat range plug after initial heat up of eng with #8 plugs . Again I see no reason that 14 to 1 comp na is even near in trouble with pump e85.Bad tunes and heat kill engines . E85 eliminates both issues imo. That fuel is pretty user friendly.

[Orr89rocz]

Thats gotta be well over 3000 now

[Juho_]

I have no clue what is "the" max compression ratio.
Depends a lot of engine design.

I've ran about 17:1 compression ratio with small cams , and couldn't break it at wot.. on E85.
Dynamic comp wasn't much less than 17:1 - bmw 2.8 liter 24 valve engine.
Part throttle and lambda=1 caused excessive knocking, caused by pre-ignition.
Leaner mixture = no problem.
Wot and lambda=1 or richer/leaner no problem.

It would require a lot of boost , compression ratio / heat in the cylinders to break the engine.

[fabr]

Somehow in these discussions,statements are many times made without clearly defining the use of said component/engine/etc.. We all know what works for one may fail miserably in another application. I appreciate all the comments.

[BrazilianZ28Camaro]

I tend to agree and hence my question. I can get the compression down easily to 13:1 with a .060 gasket leaving me with approx .072 quench. I think the 20cc dish in the piston leaves an approx .300 wide quench for less than half the circumference. Will that small area of .072 quench likely cause any detonation issue? I have a gut feeling it will not.

I would'n set the quench that high, it will favor detonation far more than the CR it got out.

I've seen medium CR engines stop pinging just by setting a piston/quench combo adequate , even when this setting increased the CR by a full point.

BTW, for sake of comparisons, have you guys measured the cranking pressures @ SCR/cam sizes to have an idea of whats inside the engine is ok, or check what a customers engine needs for fuel octane?

I'm just wondering what cranking compression would a 380" SBC show at 14:1 SCR and a 270@050 intake cam lobe.

Cranking compression pressure is a crude whay to compare engines, I know, but might be a reference point.