Looking for info on high boost, high CR, and e85

[FALaholic]

I'm trying to get more information regarding the max effective compression ratio that e85 can support.
Trying to judge if 10.5:1 and 40psi will work on e85, even up to 12:1.

[vollosso]

I wouldn’t try it.

What you’ll realize after it’s done is that you gained almost nothing and removed 100% of your safety factor.

Leave something on the table, keep some reliability.


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[someguy2800]

The old motor in my car from a few years ago had wiseco pistons, stock non vanos rods, stock gasket, and about half a millimeter machined off the top of the block to raise the compression. That one measured out almost 12:1 compression and I ran that to like 32-34ish psi on pump E85 with an S366. After that I transferred those pistons to another stock height block with a cutring gasket which would be about 10.7:1 compression. I have ran that as high as 45 psi boost with an S476sxe. Neither motor was sensitive to tuneup and seamed to have plenty of safety margin. I felt like the higher compression motor was more responsive and just seamed to make power easier, so I am going to put together another one with about 11.7:1 compression. Would really like to make like 1200 whp.

[someguy2800]

I am changing a bunch of stuff on the car to try to make more power N/A so I don't have to run quite so much boost. I would really like to get it to make like 1000-1100 whp in the low 30's for boost on pump E85 as basically the street tune up, and then to turn it up more than that run a race ethanol like One Ethanol R.

[vollosso]

While it can be done the whole setup comes into play. My car made 1000whp on 9.2:1 I rebuilt it to the same compression and don’t worry if I have e70 or e80 on hand.

I guess I’m getting more conservative than I used to be. Tuning these newer cars with more sophisticated knock systems starts to show you how hard you’re really pushing it.

I’d consider something like 10-10.5:1 and 35-40 pushing it and probably a track only setup.


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[someguy2800]

1000 whp through a 5 speed and 1000 whp through an auto and unlocked converter are two different things. I personally wouldn't build anything with less than 10.5:1 or so unless it also needed to be able to flex fuel to pump gas. I just don't really see the downside assuming the combo is efficient.

[FALaholic]

Thank you guys for your responses.
How would more aggressive cams play into the mix, regarding CR?

[someguy2800]

Some people say with more aggressive cam's the effective compression ratio is lower because the intake valve is open later, and thus you can run more compression with larger cams. I personally think this is a false way of looking at it because your still trapping more air in the cylinder due to inertia of the air, so the real compression will be higher with bigger cams at high rpms. Personally I think its all about managing peak cylinder pressures though tuning and boost control.

[BadBoostedBmwM3]

@ Vollosso’s reply

It’s so interesting that you say that; I remember way back in the recession Days when I joined BF.c and George @ICS was marketing a stage 1 kit kit (mostly OBD2 e36s) the kit ran like 14psi and made damn good power on 93 like 550whp with a .140MLS and a gt40.

Long story short, people starting turning them up 16-17psi, and the head starting lifting because it was knocking. George even mentioned that it was making more power, but knock would be problem. I couldn’t understand that. How just 2-3psi more, and you were at the threshold.

[vollosso]

@ Vollosso’s reply

It’s so interesting that you say that; I remember way back in the recession Days when I joined BF.c and George @ICS was marketing a stage 1 kit kit (mostly OBD2 e36s) the kit ran like 14psi and made damn good power on 93 like 550whp with a .140MLS and a gt40.

Long story short, people starting turning them up 16-17psi, and the head starting lifting because it was knocking. George even mentioned that it was making more power, but knock would be problem. I couldn’t understand that. How just 2-3psi more, and you were at the threshold.

I don’t really see any knock on the dyno with similar headgasket setups, 92 octane, and a gt35-gt40 sized turbo up-to about 18.5psi

Tuning on these setups is critical, Ive seen a lot of setups and tunes since I started and comparing them to what we do now I’d say a lot of stuff used to be overtimed, especially in the midrange.


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[PlayerN07]

Frankenstein 10.5:1, cutring/arp, flex fuel, meth charge cooler, and 40r here!

[FALaholic]

Frankenstein 10.5:1, cutring/arp, flex fuel, meth charge cooler, and 40r here!

3L + e85 + meth inj + GTX40R?
Pressure?

[PlayerN07]

You got it! 18psi on pump 93 + meth & 25psi on e85 + meth. (e85 + meth is a redundancy)

[pbonsalb]

I have run 23 psi on 93 plus water/meth with a GTX4088R. Made 677 rwhp SAE on a Dynojet. E85 would do better since it allows more timing, is oxygenated and burns cooler. I plan to try 24-25 psi with my EFR9180 on 93 plus water/meth at some point and think it would do 725 rwhp (since the GTX4088R dyno, I added a CES extreme ported +1mm valve head, Schrick 264/256 and changed the meth from a single nozzle to 6 nozzles (small one in each runner).

[PlayerN07]

What hot side on the GTX4088R?

[pbonsalb]

It was a 0.95.

[PlayerN07]

The 1.06 seems to be the best balance in letting the motor breathe out of boost and flowing peak power without terrible transient response on these engines.

[pbonsalb]

I did not like the response with the 0.95. That was why I removed it and sold it. I probably would have liked it even less with a 1.06.

[1SLWM3]

Is there a difference when comparing .95 and 1.06 between two different Turbo manufacturers? Are they apples to apples or...?

[pbonsalb]

The principle is the same, but turbos vary in tech and sizes. Is the turbine a 66mm or 74mm? Is it titanium or inconel? Is it 9 blades or 11 blades?

[BadBoostedBmwM3]

The principle is the same, but turbos vary in tech and sizes. Is the turbine a 66mm or 74mm? Is it titanium or inconel? Is it 9 blades or 11 blades?

Does material really matter that much?

[pbonsalb]

Weight matters in anything you want to accelerate.