E85 diary
 

I normally don't post anything that is in progress but I thought I'd try something different.

It took a long time to find any real info. This is what I found to be the most helpful:
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http://forums.evolutionm.net/alterna...notes-afr.html
http://forums.evolutionm.net/alterna...ing-notes.html

E85 has a stoichiometric fuel mixture of roughly 9.78-9.8:1 in E85's purest form (Class 1 85% Ethanol summer blend). As the fuel's Ethanol content goes up the stoich range goes down. For instance, 100% Ethanol's stoich is about 9.0:1.

E85 will maintain max brake torque much richer than stoich than gasoline will. But, because of it's excellent detonation threshold(due to lower combustion temps, lower peak cylinder pressures..etc), it can be run much closer to stoich than gasoline safer. E85 reaches max thermal efficiency at about 13% richer than stoich, whereas gasoline is about 16% richer than stoich(with pump gas being even richer). But again, E85 can maintain Max Brake Torque well into the 30% richer than stoich range, unlike gasoline which is limited to about 18% rich of stoich. DISCLAIMER: Just because E85 itself will still make power at super rich AFRs, doesn't mean it's a good idea or even recommened. A whole host of issues come with running super rich AFRs, that you need to be aware of, but i will cover later.

Therefore Max Rich Torque of E85 is 7.1:1- 8.5:1

With that being said, here is what i would consider a very safe and conservative fuel tune on E85. *AFR's listed in bold are for widebands o2s that are calibrated for gasoline, AFR's in ( ) are actual E85 AFR:
http://forums.evolutionm.net/alterna...notes-afr.html

Part Throttle lean (max eco) AFR of 16.5:1(11.0:1) 12.4% leaner than STOICH
Part Throttle rich AFR of 14.7:1(9.8:1)
Spool up... AFR of 13.5:1(9.00:1)
WOT... AFR of 12.1:1(8.06:1) 17.7% richer than STOICH


*If you're using a wideband that is calibrated for gasoline(14.7:1) and cannot change the calibration of the wideband, take your gasoline AFR and divide it by 1.5 to get actual e85 AFR or use the wideband in lambda mode. 1 lambda is 9.8:1

Here are some common AFR conversions(Gas AFR on left, e85 on right):

18.0:1=12.000
17.5:1=11.666
17.0:1=11.333
16.5:1=11.000
16.0:1=10.666
15.5:1=10.333
15.0:1=10.000
14.5:1=9.666
14.0:1=9.333
13.5:1=9.000
13.0:1=8.666
12.5:1=8.333
12.0:1=8.000
11.5:1=7.666
11.0:1=7.333

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All afr numbers that I give are in gasoline numbers and not E85. My brain is too old to translate. This is my summary of the info:

-You can run very lean at cruise, possibly reducing the huge hit on mpg. 16-17:1

-Heavy timing will also help mpg and it is better to err on advancing past the ideal timing than being under.

-E85 won't knock as easily as gas when you pass MBT. Tuning can't be done by ear or det can. It has to be done on a dyno or with an accelerometer.

-Running too rich is bad as you may run into preignition(not knock)

-12.0:1 seems to be the sweet spot for power.

-It will make more power just tuning the fuel but there is massive power in the timing.

-EGT's are reported at 200°C lower.


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A few days ago I swapped out the RX-7 550's for FIC1100's from ZX-Tex. For me, the 550's at 50psi base fuel pressure were hitting 90% duty cycle. I'm not speculating at what boost/whp.

I spent 20 minutes retuning on 93. The next day I drained the tank and filled up with E85. I added 30% fuel and 3° timing across the board. The fuel was close enough to run. I think I had to add a little more fuel but it was in the ballpark. The timing increase is super conservative and I will end up spending a lot of time tuning it.

I need to upgrade my stock 91 coils to the GM LS2 D585's. They've been sitting on the shelf for over a year and I think the E85 is harder to light off.

Had an autox yesterday. At the same boost level as I was running with 93, the car definitely had more power. The other benefit is that the coolant temps barely rose 2°C during the run. I didn't check the actual numbers with the IR but the underhood temps are considerably lower.

After tuning, I'm considering running the engine hotter than the current 84°C. I suspect that if the IAT's and/or coolant temps are too cold then things might go downhill. During tuning I didn't shoot water but I did during the autox. Have to figure that out too.

It will be interesting to see what others have to add to this thread, I'll be getting my 1200cc injectors any day now and will be switching over some time next month after the miata challenge.

Good info.
I still run afr close to gasoline just to be safe (I know I know) on mine. 14.7-15.5 in cruise, 13.5 low boost, 11.5-8 full boost.

Guess I'll up everything half a point or so when I get some time to fiddle with the tune again.

Forgot to mention that I was rough tuning the cruise today. I am shooting for 17.0. It might have been bucking in the high 17's but definitely in the 18-19 range. Even at 18 it wasn't as violent as 16 on gas.

I'm not even on my first half tank. It has tuning and an autox on it so this should be as bad as it gets. Maybe I'll fill up tomorrow to check it.

That is right where my tune sits as well.

"Where is max power on E85" is on my to-do list when our dyno finally shows up.

You guys are getting a dyno!!?

That's awesome! Which Dyno setup are you getting ?

- Jason

Interesting reading on the sensitivity to temp variations.

Good post. I can help you work on your car this weekend if you want.

Tuning by ULP afr's...
yeah cant go much past 17.5 without it missing. good power in the high 12's for me, that 10.5:1 NA atm.

Up to 48 degrees of timing on my map (NA!!) no audible ping, id like to see whats up on the dyno with it.

Still cant get great economy, about the same miles per dollar ad pulp though

Dann

Thank you for posting your numbers.

This is the best info I've found on timing vs mpg for E85:
http://e85vehicles.com/e85/index.php...5952c#msg10885

The first 75miles on E85 had one autox, hard tuning and generally very rich cruise afrs gave ~16.5mpg.

The next 70 miles were low speed cruise(40-60mph) with afr's between 15-17 and timing around 40° yielded ~25.5mpg. My average 93 gas mileage is 27-28mpg. I really need to spend time tuning the ignition. I'm going to try 37° and 43° on the next couple tanks.

Yesterday it was a steady (for me) idle at 16. When cruising it would definitely buck at 19. It was sometimes ok at 18. I'm still going to shoot for 17 for now.

Local E85 is $2.80/gal and 93 is $3.34. As long as I get over 22.5mpg then E85 is cheaper to run and that doesn't even take into account the other benefits! Too lazy to do 3rd grade math so: http://e85prices.com/milesperdollar.htm

Ill post a fuel and timing map, along with a log in a few days time when i can. Ill have to provide a link to the software to view the log as I use a kiwi computer.

Dann

PS keep em coming.

22.5mpg mixed driving - same style would have yielded 26.5-27mpg on 93.

E85 - $2.89
Crap 93 - $3.48
Good 93 (Chevron) - $3.59

$/mileage, E85 is slightly cheaper to run. I'm happy so far. Still haven't tuned the WOT timing. Cruise afr's are rough, still going into the bucking zone of >18. It's averaging 17:1.

On a closely related note I drove a different (not DVCN's) E85 turbo Miata over the weekend and it absolutely ripped. The maps have not even been optimized yet. I was impressed. Built motor, GT2871.

Excellent information about being able to get $/mileage so low with lean cruise. I soooo want to convert a non-Miata vehicle of mine.

Haven't done any tuning, too lazy.

Filled up at $3.26/gal the other day but was annoyed since it was $3.09 a week ago. After seeing 93 for $3.95 I didn't feel quite as bad.

At 24.7mpg on E85 it is definitely cheaper to run than 93 and actually equal to 87 right now.

After the last fillup the afr's are .3-.4 leaner. E85 can be anywhere between 70%-85% so it's possible that the current mix has a bit more ethanol in it.

What did you change when you went to E85? Did you mess with the fuel pump or fuel lines at all?

What did you end up adjusting on the timing? Just add 3` across the range?

At last i'm confused by the chart you show. Let say i'm using my regular fuel LC1 Wideband. For gasoline i am looking for 14.7 on the gauge and 12 in low boost. What would the same gauge show when running E85?

I tuned timing properly as if I had no map, just went to base and did it all over, No change to fuel lines or pump, on an LC1 set to Gasoline, your looking at 14.7 for stoich, 17:1 for cruise and 12:1 for full power.

Dann

I may have to give this a try, in a month I could buy a spare BP with the savings :o

Basically the same. The gauge just takes the lambda measurement and converts it to gasoline AFR. The stoich ratio changes, but the lambda measurement doesn't, so the AFRs you see will essentially remain the same between the two fuels. You can run E85 a little "leaner" than gas - exactly how much leaner is on my list of things to play with on the dyno.