looking for some advice/help with a few questions.

I have been running modified cars for years now, however never actually switched over to the running E85. I recently bought a new 2017 Grand Sport which I have already done the normal first round of mods including intake, headers, x pipe, cats and tune. The car runs great, but looking to get ~500whp mark and on my research I should be there (or close with E85 change).

I have done quite abit of research on this fuel however I find quite a lot of conflicting information. What I am looking for is anyone who has actually done the switch (preferably on an LT1 motor) and can answer some very basic questions and/or give some advice/comments/suggestions etc..

Overall:

It seems like running E85 has very little downside. The biggest being availability and some slightly lower gas mileage. The upside is more power, running cooler and cleaner. Are there any other major drawbacks I'm not considering?

Hardware:

It looks like only need the DSX Flex Fuel Sensor kit, am I right? Right now I am just NA so would I need bigger/different injectors?

Install and Tune:

The install looks pretty straight forward. If I am understanding it properly the tune is set up to run full e85 and then also regular 93octane, is that correct? (note I am having if custom tuned again by someone who knows what they are doing)

This sounds like a simple question, but if I have not had the sensor installed yet...do I drive it to my installer shop on 95 octane...then drain the entire tank and fill up with only e85 and have it tuned?

Running a Flex Fuel:

It seems to be as simple as installing the flex fuel sensor then whatever I am running straight 93 octane, e85 or half and half the sensor will automatically adjust everything to accommodate? That is what I read, but in reality is it really that simple? Am I missing something here..I mean can I have it tuned to run e85 but then say run 93 octane for the next 2 years then fill up with e85 and bam it will literally pick up that tune seamlessly?

Storing the car with e85 in the tank:

This I know is a concern for many as Ethanol attracts moisture. I live in NC so I pretty much can drive the car year round, however there may be times when I don't drive it for several weeks....or I may have a tank of gas that may take me 2 months to get through. So my question is if it is sitting for how long, with how much in the tank would be considered a problem. Obviously I know that in the winter I can put in 93 octane when I don't drive it as much but I will probably never totally drain the tank so chances are I am always going to have some Ethanol in there (higher than normal gas).


Thanks for the replies, Rick

 

My buddy installed his flex fuel sensor on his new GS and then had it tuned on E85. Bigger injectors are not needed. Car picked up substantial gains. Since E85 requires about 30% additional fuel, I would drive it to the tuner on gasoline and then change fuel there. I would make sure that your pump E85 is very close to 85% ethanol. Winter blend can be as low as 50%. Once properly tuned, just drive it without any worry.

 

Comments inline.

 

It looks like most of your questions were answered above. I'll only add that it is not recommended to keep E85 in the tank if you store your car or drive infrequently. If you plan on letting the car sit more than a week or 2, I would recommend running as much of the e85 out you can and fill up with 93octane.

 

Thanks everyone for the responses. Probably beating a dead horse by asking this, but given most of my research is positive I'm having a hard time understanding why everyone does not just go with the conversion and run 93 and e85 just occasionally. I probably sound paranoid but its almost too good to believe.

To that point, again simplistic question...is there any research that shows that going from 93o in on tank, then mixing e85 half and half...then going full e85 for a tank etc... has any damage or additional where what so ever? I mean changing octane that much, that often having any type of negative effect at all? Does it require more specialized tuning or once you set the tuning does the flex fuel sensor always changing for every sing octane variance. I image it takes a few miles of driving for the computer to sense and learn the octane over and over again.

 

The adjustment tables are built into the ECM. The only "tuning" done is as with gas, optimizing the fuel/air ratio for your combination.

This isn't really magic. Manufacturers have been doing this for at least a decade in regular cars and trucks. The primary difference is their tunes didn't adjust timing for the increased knock protection. That isn't the case with the GenV engines. Look at the ratings for the truck 5.3L L83 on gas vs E85.

And yes, making a significant switch in alcohol content requires a few miles of adaptation. Also, I ran E85 because it was significantly cheaper even accounting for the reduced mileage.

The only real mystery is why the 6.2L (N/A) engines don't have this capability from the factory; truck & performance models.

 

Thanks for the explanation. Yeah I didn't think it was so much magic as to question why didn't they do this from the factory as there doesn't seem to be really any downside...or why people are not doing this with every upgrade. Thus the reason why I was scratching my head as to think maybe I am missing something. When I did my first round of mods (even though its still an NA car with kinda common bolt ons) a friend of mine who has modded several cars actually talked me out of it. Said there were risks involved if the computer does not read the octane correctly (I guess if the sensor malfunctions??). That doesn't seem to be the case that anyone has ever heard before. I wish I would have done it at the same time with the other mods as well.

 

Well the primary reason is it voids your warranty due to the ECM tune.

Beyond that, if you're modding your car, it depends on how far you're going. Superchargers/turbochargers require their own upgraded fueling requirements that stress the limits of the LT4 injectors/fuel pump just on gas.

A basic bolt on N/A package should be ok with the stock fuel system on E85; mine was but I didn't have headers. Beyond that (H/C) who knows? I was almost there before I had to do a reboot.

 

Yep, that's where the flex fuel sensor comes in. It detects the Ethanol% in the fuel and sends the information to the ECU, which adjusts the specified timing based on the percentage. There are multiplier tables based on % E.. ie.. 50% ethanol would get 50% of full flex fuel timing or .5 multiplier, and anything above 80% would get a multiplier of 1, which would give the actual timing requested to be added from the flex fuel adder table. This timing is added above and beyond the Base spark table. The base spark (example at 5000rpm may be 17degrees at .92grams airmass), and say 50% E at a multiplier of .5. Then the ECU would see in the flex fuel spark table that you want 4 degrees of timing added for E85 at 5000rpm/.92g, so it would get 2 degrees instead of 4 based on the E%.

There are a few other adder tables also which add to base spark such as IAT, Humidity, ECT etc.

To further add to the equation, there is also separate fuel values for Gas vs Ethanol in Power Enrichment mode(WOT or above certain throttle percentage)

Sorry... got off on a rant there.

 

From what I have gathered you can get away with just having the GM flex fuel function in the ECM turned on. The ECM also requires the addition of a pin too.

 

Sorry to grave dig slightly, if one were to by this conversation, and install it, is there anything additional that needs to be done? Additional tuning of any kind or is it literally a plug and play?

 

You have to get it tuned. It is not plug and play.

 

Tuning for E85 is not that hard, but it certainly isn't as some suggested "plug in the hardware and enable it in the ECU". There are a lot of parameters that need changing in the ECU to run E85. Don't be fooled into thinking you can just install the hardware, buy HPTuners, and toggle the switch. You need a competent tuner with experience tuning GenV for E85.

 

That's correct and to add, most tuners who have done this a few times don't need to retune the vehicle for ethanol if the car is already tuned for 93. The chemical properties of ethanol are the same from car to car and the tables adjusting for most of it will not change. It's a quick tune update in most cases. Going from NA to FI the spark tables will be a little different. I am just saying you don't need a complete retune just to enable flex fuel, it's pretty standard stuff.

 

I was fooled by all of the "easy peasy" posts about flex fuel for the LT1. First off, unless you have very small hands and really good eyes, it is a PITA to get to the ECU plug. The instructions have you loosen all of the connection points for the right front quarter panel. Once I did that the the ECU was just supposed to drop down and I could pull the plug to pin the ECU. My 2017 GS has a cable tie back out of reach that keeps the harness from dropping down. I had to remove the side air vent (black part with the GS logo) to get to the plug. So not much fun at all.

I ordered an HP Pro tuner and had a friend who knows how to tune help me tune on 93 octane. It is very involved. "Just turning on flex fuel" is far from accurate. There are many parameters that need to change when you go to flex fuel. So a flex fuel tune that will void your warranty will cost you at least $300 for the fuel sensor, $650 for the tuner or to have someone tune it and will get you some HP with the ethanol. Even though E85 is cheaper at the pump, your car needs more of it to make the same power as 93 octane so don't think you will save money. Also, if you want to take the sensor off, depending on which one you get, you might have to buy some plastic quick disconnect pieces, trim it down to just the right size and wiggle it in the small gap to get your stock line off of the sensor.

My conclusion is that I would not do this if I had it to do over again. I track my car about 4 times a year so now I have a little faster GS, with no engine warranty and I am out about $1000. I would have been wiser to use that money for another track day or a set of track tires. Just my two cents on the flex fuel conversation.

 

Any powertrain mod to your car, you'll lose the warranty. And if you're modding, you really should tune it. Personally, I consider self-insuring the powertrain and tuning hardware/software, sunk costs when it comes to modding. Which makes E85 the best bang for the buck, IMHO.

 

I agree on the ecu part. I cant even loosen the fenders on my grand sport because the skirts are riveted on and I dont want to drill them out. I saw that you had to pin the ecu, no thanks. The ecu plug on my car is almost agaisnt that fender; and one bolt to take that cover off is super hard to get at. I think tuning goes without saying, if you change a system you need to make it work with those changes. If a mod doesnt require tuning, I think they are mostly just snake oil.

 

 

Like others have mentioned, the hardest part of installing this sensor was getting to the E92 ECM on the C7. You have to jack up car, pull wheel and the carpet wheel well liner. Approx 18 bolts/fasteners between the inner fender to door side of fender, side splitter, and firewall side. After that, getting the ECM out and finding connector #1 (the very top out of 3) pin#38 is tedious and something you want to get right the first time. Finally, once going back together you don't want to end up like me having to unbolt fender hardware to adjust the fender so that the leading edge of the door wont bind against fender when closing (I had to readjust my fender PITA).

Other that that I was really impressed with the numbers my car made with bolt-ons and E55 (C7Z07/M7). I say for the money spent it's low hanging fruit to grab and you'll be happy in the long run.