E85 Safe/Max Dynamic Comp Ratio

[mt-engines]

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.

Will this be EFI? Pump e85 or race e85? Is this a 6000lb truck? Or a 2600lb car? Will it be wide open throttle below peak torque RPM? Stick car? Auto?

There are so many variables and DCR is not one of them to even care about.

14:1 could be safe at say .80 lambda but disastrous at .92 lambda. Even though it might make peak power at .88.

Some things you just have to try yourself. Your 14:1 compression might actually be 12.8:1 measured.

So just because it works for someone else doesn't necessarily mean swing for the moon.

From my experience 13:1 is a good place to start for a beginner on e85 in many applications.

8 o2 sensors will help. Just like anything sneak up on it and be safe.

[Dave B]

No biggee Chris, but if you look into this several car manufactures run higher comp with pump gas.I had a gsxr in 2010. It had 12.85 from factory. It had a warranty and you know peeps run those hard all over country with some pretty junk pump fuel.

[Eroy]

Don't get me started on DCR.. its just a formula for old guys that won't ever build anything in their lifetime, but like to do meaningless math equations.

Yeah that seems to be pretty accurate lol

[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.

Will this be EFI?yes Pump e85 or race e85?yes Is this a 6000lb truck? Or a 2600lb car?3100# desert car Will it be wide open throttle below peak torque RPM? yesStick car? Auto?manual with tq converter



From my experience 13:1 is a good place to start for a beginner on e85 in many applications.I don't disagree at all,hence my question.

I am by no means a beginner with e85. Been running it for about 10 years now. I buy drums of anhydrous e98 from the distiller and blend to e85. Always verified before it goes in tank.I had decided to run the 14:1 but am having second thoughts. I can get it down to 13:1which I know to be safe for my application/engine(sb2.2 headed 427) running a .060" gasket instead of the .041" but the squish would be approx .072 instead of .052. I'm thinking that would be better comp ratio and since the pistons are a 20cc dished the increased squish clearance is pretty irrelevant. Am I thinking along the right lines?

[Dave B]

Unless you have some short jabby camshaft ,I wouldn't sweat it. You know your cam events @.050 ?

[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

[roverman]

Would a knock sensor settle this ?

[fabr]

Not likely,IMO.

[Orr89rocz]

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

[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.

[fabr]

Apparently no one here uses e85 in an endurance application. I understand most here are drag racers as I was for many,many years. Thank you for the replies.

[Orr89rocz]

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.

One R is suppose to be blended with high octane components. Some well known ultra high hp viper tuners say its the best of the ethanols. My buddy however used to mix c12 or c16 with his ethanol sometimes. Worked fine even tho lead doesnt mix well with ethanol. However all drag racers or roll racers in standing half mile or less.

Pump e85 for me has been fine. Ive made 2054 whp on 72% pump in a turbo bbc. For me it hasnt seemed to matter what grade it is as long as its 70% or higher which i never seen it dip below that here, although i never tested it in dec/jan. Spring usually its 70-74% and by may its 80’s.

I since went to renegade pro ethanol. Not sure if its done any different yet but i feel more confident in it. Cutting e98 with premium gas would be nice too, for consistency in percentage but even pump gas blends can vary.

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

[Dave B]

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 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.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. 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.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

[Dave B]

image~2.jpg

And 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.

[Dave B]

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