*Updated 11/11/14*
If you would like help tuning your GM vehicle to run on ethanol, or need tuning help in general, send me a PM. Thx!
With so many questions lately around E85, I figured it was time to create a thread describing all I have learned from running the cheapest race gas out there! Note that this thread mainly addresses those with Supercharged 3800 series II and series III motors. The majority should be able to be leveraged for other platforms as well.
Question: Is E85 worth it?
Answer: YES! If you are running any of the supercharged/turbocharged powerplants that primarily dominate this forum, your car will love you for it. In short, you will have access to 105 octane race gas for far cheaper than you can find race gas of that octane rating anywhere else. And this doesn't even get into the intercooling effects of E85 due to the inherent abilities of liquids to cool the air around them due to specific heat values. The list goes on and on...
Question: Are there any adverse effects from running E85?
Answer: There can be...
1) Your car may take a little longer to start up in the colder weather. I have experienced this after playing with different tunes on my E85 setup, and I have already spoke with others who have encountered the same effects. Nothing to worry about really, just know that it can happen.
2) Your gas mileage will suffer. This is primarily due to the stoichiometric values of E85 being around 9.85/1 AFR vs. that of gasoline at 14.7/1. It will also depend on some other factors but none as great as the one just mentioned.
Question: How do I tune for E85?
Answer: There are two main ways that I know of.
1. EASY METHOD: Simply install larger injectors into the car (usually at least 42.5 lb injectors) and then make sure your injector tables are scaled approximately 30% smaller than the injectors you are running. I have seen multiple stories and testimonials lately of using this method successfully. Technically, you can get away with no tuning at all if you are currently on a stock tune set for stock injectors, and then you simply swap to 42.5 lb injectors and E85 at the same time.
2. MORE THOROUGH METHOD: This is the path that I chose, and have experimented with many many times recently. Here is how I did it:
Fuel Tables:
1) Change stoich. target to 9.85
2) Change PE tables to target 7.3 at WOT (slight adders on that in the throttle position vs. AFR adder section). If you are using a wideband (which you definitely should be if you are changing fuel tables), change the PE-mode base AFR setting to achieve whatever WOT AFRs you desire. This should be somewhere in the 7.3/1 range though.
3) Change Open Loop AFR targets to 9.85 as well (also change the Cat Over Temp AFR targets as well to 9.85 just to be safe)
Timing Tables:
1) MAKE SURE you zero out the AFR Correction Spark Table. Doing this prevents the car from adding 8* of additional timing at all times when running E85. I learned this the hard way through experimentation...
2) I also zeroed out the IAT Spark AFR table. Not fully necessary, but a good idea since E85 won't really require spark reduction at higher inlet air temps due to its intercooling effects.
3) Adjust the Main Spark Advance tables as best as you see fit depending on your application. I have found that my stock timing tables actually have worked best on E85. I have added timing, only to achieve more knock. With stock timing tables, I was able to add considerably more boost, and remain knock free. To each his own, but I have confirmation from others that this approach of not adding much timing and simply adding boost worked well for them as well.
3. And if you are feeling adventurous... You can actually get away with adding E85 and mixing it with regular gasoline up to around 50% ethanol content reliably on a completely STOCK GTP, according to those who have tried on this forum. This can bump up your octane rating on a given tank of gas a bit and likely help you get rid of some knock (if you are seeing any). If you plan on trying this out, it would be a good idea to start off with lower ethanol contents (say E30% or E40%) and see how the car handles it. If the car likes it, and you like it, then E50 may work too. Just make sure you don't get caught looking at your smart phone while you are adding in the E85 mix or you could put yourself walking!
Question: What pulley size can I run on E85?
Answer: That depends on MANY things.
1) Every engine can respond to different mods differently. It should definitely allow you to drop in pulley sizes (if you already aren't knocking through the moon!). However, the pulley size that you drop to will depend on the other mods you have present and your individual setup.
2) It is best to start off large, and work your way down in pulley size. Drop pulley sizes incrementally, scanning your KR and fueling tables as you go. If you start seeing KR, simply try to tune it out first, or bump up in pulley size until it is gone. I have seen several members drop down to nearly 3.2" pulleys on virtually stock setups. Don't bank on your car being able to pull that off, but... it has been done.
Question: What else do I need to modify to run E85?
Answer: There are several other things you can do that will definitely help support your E85 swap.
1) Fuel pump rewire. The stock fuel pump wiring is terrible. Caspers, Racetronix, and ZZP all sell relatively cheap fuel pump rewire kits that increase the pump voltage. Definitely a good idea to help your fueling system supply the extra fuel that E85 demands.
2) New fuel filter. May not be fully necessary, but a good idea since they are cheap, and help guarantee that you are starting with a fresh, clean filter to allow as much E85 to the motor as possible!
3) Injectors. As mentioned above, you will NEED to run larger injectors if you want to do this the right way. The stock injectors just can't keep up with the added fuel needs of E85. I would recommend going to at least 60 lb injectors. Your car will run/idle/cruise just fine on 60 lb injectors. And you will have some headroom to grow as you work your way up in power on E85.
Question: Do I "need" a new fuel pump to run E85?
Answer: Not really.
1) I, as well as many others are running E85 setups on series II and series III motors just fine with plenty of fuel on our stock pumps. I am currently running a 3.1" supercharger pulley with simply a ZZP pump rewire, 60 lb injectors, and a high flow fuel filter. The stock pump is holding up just fine to the fueling needs of my setup.
2) If you have the funds and really are going for a high power build, then by all means, get one! A higher flowing pump can only help. A lot of guys recommend a Walbro 255 lb/hr pump. This will depend on your power/performance goals though. My suggestion is stay stock to start and check your wideband. If your AFRs are where you want them, then that stock pump is doing just fine for now.
Question: Does the ethanol content of E85 change throughout the year?
Answer: Yes it does. In the summer months you will be closer to actual E85 (85% ethanol). As colder months set in, the actual ethanol content gets closer to around 70%. Ever notice that the pump usually mentions "minimum 70% ethanol"? The change is mainly there so that cars have less ethanol content and more gasoline during the colder months to start easier. It's pretty safe to assume that most pumps will run 70% ethanol during winter, 85% during summer, and somewhere in between during the spring and fall. If you plan on tuning yourself, you can take this into account if you actually want to try and target stoichiometric combustion for the actual ethanol content you are putting in.
A great tool to help you dial in your tune for a given ethanol content can be found at: http://www.ecmtuning.com/wiki/e85fuel
I will update this thread with more questions and answers on this topic as time permits. I am experimenting with my tune and E85 regularly, and I will continue to add info as it becomes available. Thanks for reading, and enjoy the smell of popcorn coming from your exhaust
