RomRaider

I'm planning on switching over to E85, and in the future, hopefully running straight alcohol.

Anyhow, everything I have read indicates that you need to run more timing on E85. If I were on pure alcohol, I would say that 10 degrees more advance across the board would be a good starting point.

But what would you say with E85? And with turbo subarus in general, which run a lot of timing as it is?

Would 5 degrees across the board be a good start? Feedback from those that have tuned extensively with E85 would be appreciated.

1st, I'm not running E85 on my car. Also planning to switch in future, and now I have slowly going article write about alternative fuels, mostly E85, M85 CNG & LPG...
You may already read this hotrod's post:
http://forums.nasioc.com/forums/showthread.php?t=803341

and I'd recommend to start with fueling, going to leaner lambda #'s (not AFR's!). It will be useful to modify RR definitions to display lambda. after you can play with timing in small increments (say 2 degrees a time). Dyno can be very beneficial if not absolutely neccesary here.

I generally leave the lower values pretty similar to stock but add more timing under load. you will find the ignition timing not drop as much as load increases. Optimum timing will have to be set on the dyno. You can go way past MBT without getting knock on e85. But at the same time it keeps things pretty safe for tuning on the street. Start out with about 4 degrees of advance at peak power and see where that goes.

Thanks for the response eminehart. That was what I was looking for.

I was wondering if a EGT gauge would help with ignition tuning. My thought was this process (this is assuming everything else is static): You would start with the base timing map, and a known EGT on alcohol at that timing. You would start adding timing, and your EGT's would start to drop a bit. You would continue to add advance until you EGT's would drop anymore, and then pull say 5 degrees at that point.

Does that sound like a reasonable process? With that process, I'm assuming you are getting more and more complete burn and energy conversion. But as your EGT's stabilize, you are combusting too early in the stroke.

I'm fairly unconcerned with fueling. Alcohol is very forgiving on both AFR's and timing. I'm planning to run 14.7:1 AFR at low load (I'm assuming it won't spit and stutter that lean, but if it does, I will go into the 12-13:1 range), lower rpm (cruising ranges) and then jump up to 10-11:1 in lower mid ranges. Finally, for best power, I would target the 8-9:1 ranges.

I'm sure some will think I'm nuts for planning to tune AFR's on alcohol that lean, but many have done it that way. Alcohol is very forgiving. That, and I'm trying to have my cake and eat it too:) I want to try to maintain my current fuel economy and perhaps enjoy a little bit more power.

Those are amazingly lean if you are talking e85 afr's.

I wouldn't go leaner than 1.1 stoich at cruise and target and somewhere between .85-.80 stoich. I wouldn't go leaner than that. It is still a turbocharged Subaru and requires richer mixtures than other cars.

I think we may have a misunderstanding or miscommunication issue here....



My Wideband reads 15:1 under CL... but my mixture is no where near the same as it would be if I was running gas and seeing 15:1 on the gauge.

The Wideband is a Results Gauge... it shows the result of the burn. How you get to the same result with E85 and Gas are way different.

In other words, E85 won't burn with an actual 14.7 parts of air to each part of fuel.... even if the wideband says so.


It depends on what type of Wideband you have... I found it very easy to leave mine in gasoline AFR's... since we are pretty much all more familiar with what AFR's we want to see when running gas... for example, maybe you would target 11.1 on the top end under WOT. I leaned my mixture out a little bit after switching to E85... up around 11.4 now (on the wideband).... This is also easier to keep simple because the fuel map still reads gasoline targeted AFR's.... (adjusting the injector scalar takes care of the actual approx~30% difference.) To me it made more sense to do it this way........

First, leave your wideband and RomRaider fuel tables so that they are in terms of gasoline AFR. Otherwise you just confuse yourself and everyone else.

hotrod's E85 FAQ suggests that best torque from e85 is obtained with 15% excess fuel, relative to stoichiometric. So tuning fuel is easy. In the normal open loop fuel table, just change every non-14.7 value there to 12.7 and you're done.

Tuning spark advance can't be done without a dyno.

I'll put it terms of lamba...My assumption is E85 stoic is 10:1...

I was planning on in some spots on the fueling map, running as lean as 1.47. I did that, and the motor ran, but not great. It died on me at times. I have successfully run it as lean as 1.2 without the motor quitting on me. That would put it at 12:1 AFR.

Of course, this is only in a handful of cells in the region that I cruise on the highway. Otherwise, standard fueling rules still apply.