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

I see way too many threads with people asking the same questions about the best way to tune / set up our cars for E85. I have been running E85 for a few years now and have converted 8 other cars. I have experienced the problems and have found solutions to all of them. Some of what I say in this writeup will be opinion but I will do my best to point out other viewpoints and make it clear when I am stating opinions vs. facts. Lets get started.

One more thing before we begin.

This entire guide will be written from the viewpoint that you have a car that is on the stock tune or at least already properly tuned on gas and set up correctly with the correct supporting mods. I am also assuming you have a fuel system that is already capable / has been upgraded to be capable of supplying 30% more fuel then it already is. Just check your injector duty cycle and make sure its around 60% or less at all times. I will explain some stuff that you might have to fix but you will need to get to a good starting point more or less. As with any modification to your car you should ensure your car is working ok first. If you have +20 long term fuel trims and 15* of kr you should fix that crap first. If you have questions about WOT tuning E85 or timing advance see the 2nd post for a quick guide on how to do it. Also as a disclaimer. I HAVE NO IDEA WHAT I AM TALKING ABOUT. I HAVE NO DEGREE OR FORMAL TRAINING THAT SAYS I KNOW WHAT I AM TALKING ABOUT. ANYTHING RESULTING FROM YOU FOLLOWING THIS GUIDE IS YOUR RESPONSIBILITY. IF YOUR MOTHER DISOWNS YOU AND YOUR SISTER IS NO LONGER GOOD LOOKING BECAUSE OF ANYTHING I SAID IT IS NOT MY FAULT! (Lets be honest here she was already hit with the ugly stick)

Lets get started. Pros of switching to E85.

• It cleans everything including your pistons. This is a great way to prevent hotspots and the kr resulting from it. It will also keep your fuel system, exhaust, and oil cleaner.
• It is around 105 octane. This allows you to run more boost and more compression safely. If you don't know why then check the Wikipedia article. Octane is a measure of resistance to self ignition. Nothing else.
• It has a massive cooling effect. It takes a lot of energy to evaporate alcohol and there is 20 - 30% more of it being injected (and evaporated) then gasoline. This lowers your air charge temps which also allows you to make more power, run more boost, more timing, ect.
• It will not ruin your stock fuel system. Every stock fuel system component is rated for use in alcohol. You will have zero issue with it hurting anything unless you have crappy replacement / aftermarket fuel system components.
• It has a much wider "efficient" range that it will burn at. This means that running 10:1 afr (Gas equivalent) will make almost the exact same power as running 12:1 afr (gas equivalent). This means you can run rich on purpose to better take advantage of the cooling effect that the evaporating E85 has.
• When tuned correctly you can still run gasoline in a pinch. Ill explain later.
• Its cheap!
• You don't have to fight a war to get it.
• Made in Murcia.

Cons of switching to e85

• You WILL get 20 - 30% less fuel economy. No questions. Stop complaining. I still manage 15 in town using minor hypermiling techniques. 7 mpg when I drive like an idoit.
• It will probably ruin your fuel filter a few weeks after switching. This is from it cleaning out your dirty fuel tank. Change your filter and it'll be back to normal.
• It WILL kill cheap rubber / plastic. Don't put that crap in you car in the first place and you wont have any issues.

Why you need a tune (typically)

E85 has a different ratio that it burns best at then gasoline in simple terms. In my experience summer blend e85 requires 25% more fuel and winter blend e85 needs 20% more fuel.

The four methods explained.

#1. Just physically changing your injectors to a size that is 20 - 30% larger then your current injectors is a very crude but somewhat effective way to do it. This will never be 100% correct. You will quite possibly have hard cold starts and you will have messed up MPG / oil life calculations. You will also have no way to tweak it for winter / summer blend changes. The reason it throws off these calculations is because your trip computer uses the injector size and pulse width reported by the pcm to calculate how much fuel is being injected. The other benefit of this method is that it can be done without getting your car tuned. I do not recommend doing this for any car that is running a setup with less then a 3.4" pulley or if you want your mpg gauge / oil life meter to work correctly. Its just too crude to get a steady air fuel ratio at wide open and your fuel trims will always be a bit off. Some people struggle to even maintain fuel trims within 10%. Unless your going to combine this with an adjustable fuel pressure regulator or maf scaling box don't do it.

#2. Scaling your injectors down by 20 - 30%. This method is by far the most common. It has all the same issues of method #1 except you can actually dial in your fuel ratio properly. It can benefit from my cold start tweak outlined below. Not super easy to adjust for blend changes.

#3. Changing all of the air fuel ratio values. Better known as "The stoic method". This works great for the v8 guys because there is one single box where you specify the "stoic" air fuel ratio and then every single other fuel table just adds or subtracts from that. This means that for v8 guys the entire e85 tune involves changing this one box. Everything else except cold starts will work 100% as it did before. Us v6 guys simply cannot do this in my opinion. In our engine computers almost every single fuel related table is a standalone fuel ratio and needs to be changed by hand. Us v6 guys simply have not had our computers mapped out far enough by any company to allow you to change all of them to E85 ratios. People have done it to some success but you will have strange issues related to tables you cannot touch.

#4. My method. The best and simplest way to do it. Assuming the rest of your tune / setup is correct you will only have to change one table! Everything will work 100% like stock afterwards. Only one additional tweak is required if you need to be able to have nice quick effortless cold starts below 40*F. If you live in the south don't bother. Itll still start in a pinch it will just take a lot of cranking.

How do you do #4?

Like I mentioned before this is done under the assumption you have a working setup / tune already that is set up for gasoline.

1. Open up your current tune in hptuners or pull it from the car if your not sure.
2. Open up Fuel < Power Enrich < Injector Gain vs. Cylinder. This table typically is, and always should be set to 1.0 across the board to start with.
3. Change it to 1.25 for all 6 cylinders if your tuning for winter blend E85 or 1.3 for summer blend. If you want you can shoot for the middle at 1.225. These are just the numbers that work best for me. You may notice your fuel trims aren't quite right so you can always add or subtract from this table to add or subtract fuel to get the tune as close as possible.
   
4. Save the file. Make sure you run your car as low on fuel as possible before continuing.
5. Drive to the E85 station. Shut your car off and start filling up.
6. Open up your laptop and flash the new tune you created.
7. After your car is full start it up. It might fuss and be a little annoying to start / idle at first. Give it a minute to smooth out.
8. Drive the car around for 20 minutes and keep an eye on it with the hptuners scanner. Make sure your fuel trims are within 10%. It might take it a while to figure out whats going on. Otherwise reread step 3.
9. Run a full tank of E85 through the car or drive it until the fuel filter clogs. Whichever happens first. Some cars will never clog the filter. Just depends on how well taken care of it is.
10. Change the fuel filter. Drive it around for half an hour to get it completely heat soaked and warmed up.
11. Scan your car with hptuners. By now most of the gas should be out of the car so you can finally check fuel trims / full throttle fuel ratios if you have a wideband. You want the long term trims to be within 5% + or -. If they are then your effectively done! If they are not reread #3 and tweak that value up or down .01 at a time to get everything dialed in.

How to fix E85 cold starts regardless of how you choose to tune your car.

This is a subject of heavy debate even though the science says that E85 most certainly starts to have major evaporation issues below 32*F. Mostly because some people never have a single cold start issue. "Issue" being a car that takes more then 5 seconds of cranking to start. This could be due to differences ranging from altitude to how much compression your car is running. I know that I had zero issues with my L36 block SSM90 supercharged setup starting in my home town of Sioux Falls. When I moved to the higher altitude Rapid City area it was a bit harder to start but still very manageable all the way down to -30*F. Now with my new L67 setup my car took 30 - 45 seconds of cranking and throttling to get it running any day it went below 10*F. After doing the change I will outline below I now have instant cold starts regardless of outdoor temperature. Your results may vary.

1. Get a copy of your current tune in .bin format. This is because the table we need to access is not available in HPTuners. I am also fairly sure it isn't available in DHP. If you use DHP to tune getting a .bin file isn't an issue because that's what it saves anyways. If you use Hptuners you will have to email their support team a copy of your current tune and request that they convert it to a .bin file for you.
2. Download and set up Tiny Tuner. There are numerous guides on how to do this floating around.
3. Open up your .bin file in Tiny Tuner.
4. Go to Fuel < Base Fueling < Crank Fuel vs Coolant Temp.
   
5. Multiply the 10*C cell by 110%
6. Multiply the 5*C through -40*C cells by 120%.
7. Save the file and flash it to your car. Enjoy your lightning fast E85 starts even when it is so cold you cannot even breath without feeling pain.

Can you really still fill up with gas in a pinch?

If you are careful and don't have a lead foot the answer is yes. Your car has the ability to adapt to extreme fuel changes as long as you stay out of boost. If you go into boost your car can no longer compensate for the incorrect fuel (Gasoline) and will run extremely rich and cause all manor of issues. I have filled with gasoline numerous times and never had issues as long as I had my car properly tuned to within 5% fuel trims on E85. The only side effect was crazy high negative fuel trims and a little bit of stumbling for a few minutes when switching to and from gas.

What now?

Enjoy your E85 burning car. Most people can drop at least 4 pulley sizes after switching. Even if you don't drop pulley sizes you can add timing to get even more power. Even if you change nothing you will quite possibly feel a noticeable improvement in power just from the huge cooling effect that e85 has. You can also change your power enrichment fuel ratio to be richer without a loss in power from being too rich as long as you keep it above 10:1 (Gas equivalent) and take advantage of the huge cooling effect that the evaporating alcohol has. There are plenty of other guides and sources of information on how to add boost and timing from this point forward so I wont go into those details. Just enjoy your corn burning machine.

I hope this guide was helpful. Sticky?