Thread: The defacto guide to tuning your car for e85.

If anyone uses my guide I would appreciate it if you would respond that it worked / didn't work. I know it works for me on the cars I have done but I would like to have some secondary proof as well.

Originally Posted by darkhorizon

I want some data on this elusive no start.

Probably has less to do with ethanol and more to do with the maintenance/condition of the car.

I have seen it on 4 differnt cars. All 4 ran great and were running stock maf tables with great fuel trims. I don't know why there is this dedicated group of guys on this forum that won't let it drop but it is a issue on almost every converted car reguardless of make or model

Originally Posted by Frosty

I have seen it on 4 differnt cars. All 4 ran great and were running stock maf tables with great fuel trims. I don't know why there is this dedicated group of guys on this forum that won't let it drop but it is a issue on almost every converted car reguardless of make or model

A car can run great and still have cold start issues. For example, there are many high volume fuel pumps on the market that will deliver fuel like crazy while running, but have crummy check valves and thus do not maintain good fuel pressure after priming. Another example, gunked up IAC can work perfectly once warmed up, but work crappy in cold temperatures. There's a bunch of other potential factors other than E85.

Also, consider that E85 dislodges all the crap in your fuel system which may gunk up fuel pumps, fuel filters, etc. which might also contribute to cold start issues.

I run a fuel pressure gauge all the time, so I can guarantee that my check valve isn't a problem.

The big 3 auto manufacturers here in the us have taken measures to assist cold starts on flex fuel vehicles. So, it's obvious there is an issue with high ethanol content fuel and cold starts.

Its pointless having this argument with anyone who refuses to not see that ethanol has a diffrent evaporation and burn rate than gas at colder temps. which is why your tune needs to compensate little to help out the process. The other 15% ****ty gasoline part mixed with the e85 dosent help the situation either

The turdbo car... when we towed it up to dave @ tep... car was in nice climate controlled garage... 10* outside, but nice 60* in garage... started right up no problem, with e85.

Spend a few hours towing it up there and probably few degrees colder, and when we got it there. It would not start for the life of us... 20 minutes we tried. Used one of the goofy
cig lighter chargers... nothing. Car had tons of juice. It just would, not, start. We gave up and pushed it into a spot at the shop. Luckly was just plowed but still icey.

Dave tried later on, and still would not start for him. Finally gave up.

He then drained the cell, and put gas in it. Cycled the pump a bunch, then started it right up no problem.

Up until then, car never ever ever ever had an issue firing up in decent weather.

Never touched any of the tables that could possibly help with this, but when I brought it up to PRJ back then, he mentioned changing similar things that Frosty has mentioned.

Tho These changes have never been done yet, cause well.. the car is still up there @ tep since last winter, so ill let ya know the results next winter...

The changes work I assure you. I have been driving all winter and the car is happy as hell in the sub zero temps. My check valve must also be good considering that when I took my rails off the other day I had to bleed off an assload of pressure even though it hadent been ran in 8 hours.

Originally Posted by Frosty

The changes work I assure you. I have been driving all winter and the car is happy as hell in the sub zero temps. My check valve must also be good considering that when I took my rails off the other day I had to bleed off an assload of pressure even though it hadent been ran in 8 hours.

Im sure they will.. I once stumbled across some posts on a Subaru forum about the same issue and some of the things the guy had come up with was very similar if not down to basically
exactly what you came up with.

I cannot take all the credit. The ls guys had a nice thread discussing the theory and science behind it. They settled on 20% being the magic number. All I did was find a table for us 3800 guys that could be used to do the same thing and added 20% fuel to the needed areas. Then I smoothed it a bit and it was a success. I must have gotten it right because I haven't felt the need to change it since then. Have had a few -10*F starts and it took less then 2 seconds of cranking just like it should.

Originally Posted by GTPpower

I run a fuel pressure gauge all the time, so I can guarantee that my check valve isn't a problem.

The big 3 auto manufacturers here in the us have taken measures to assist cold starts on flex fuel vehicles. So, it's obvious there is an issue with high ethanol content fuel and cold starts.

I'm just trying to throw some ideas out there, point is there could be a million reasons why two cars with the same engine management system might react differently to E85. There's obviously significant chemical differences, but it seems that some cars are starting well regardless and some are not.

My guess is that it has to do with how much compression they are running and injector offsets. Since pretty much noone has the correct offsets I think that has a lot to do with it.

Has anyone been able to verify if the stock tune hits the commanded AFR during cold start conditions? Based on the tables, it is open loop... maybe some cars are actually running richer than others, even stock for stock? It might explain why no tune modification is required, some are already running richer or leaner than others during startup.

Might be worth looking into.

I believe most peoples problems are with cranking. I haven't herd of anyone having issues with the car during warmup / open loop with the stock tables. There is a seperate set of tables specifically for cranking fueling specifically for getting the engine lit up.

Yup. Once it fires, no problem. Getting it to fire is the tough part

Originally Posted by darkhorizon

Many degrees below zero here in Michigan. Stock tune with 42s starts great first try every time with less than 1 second of crank time. My starter is also junk as i have had to hit it with a camshaft most times i start it.

Got my 42's today. Posts like this ^^^ is what I like to see

Run engine in open loop. Lean out cruise in your ol/ve/rpm table. Add 35-40% to the ifr table & retune maf table; reference 2005 crank fuel tables. Done this for several years, excellent results in -20°F temps. And if anyone says some of the OL tables aren't mapped correctly for certain years in dhp/hpt your right. But, this can be corrected.

If you fill up on gas; just plug in your front oxygen sensor. Drive on like nothing happened.