I was looking at the stock LS3 tune in HP Tuners and there is a Stoich table from Gas to E85... actually all the way to pure alcohol. Does this mean I can run e85 bone stock? I haven't heard anything to support or deny this question yet.

It looks like the Flex Fuel option is simply disabled... if I enable it will it actually detect e85 and compensate?

 

I don't think so. These tables and ECM's are very similar and shared with other vehicles like the DOD trucks and cars. I wouldn't think they are "options" for the corvette engine.

 

I think I'm going to try it one of these days. Worst case scenerio I have to change the stoich value.

 

As I understand it other components in the fuel tank and feed system need to be changed before you can run E85. Don't forget, the LS3 is used in other platforms for GM. I wouldn't recommend trying E85. You could damage other hardware.

The owners manual has this entry:

Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines might be available in
your area. We recommend that you use these gasolines,
if they comply with the specifications described earlier.
However, E85 (85% ethanol) and other fuels containing
more than 10% ethanol must not be used in vehicles that
were not designed for those fuels.
5-6

 

Thats because they don't have the flex fuel option turned on... So it'll send the STFT and LTFT in a very rough direction.

Apparently they don't have a sensor anymore, they use the STFT or LTFT to adjust the stoich value. So I'm just going to try it one of these days and see if putting on the flex fuel option actually works.

The problem with E85 besides not being tuned for it is sometimes you run out of injector at WOT. However, I did some WOT runs and it looks like there is enough injector to run E85 on.

I did run my GTO on e85, but didn't have enough in the way of injectors to be able to get about 5000 rpms safely.

 

Any updates?

 

There's a LOT more to it than simply turning on the switch in the software. There are a bunch of other tables in the ECU that you can't see in HPT that determine how a particular engine solves for ethanol content without a fuel comp sensor. These tables just have default GM values in them for the LS3, so it won't work right on the C6.

Further, the flex fuel vehicles have a different spec pump and in-tank sending unit that is engineered to live in the more corrosive environment of ethanol fuels over the life of the vehicle. There's a signifcant difference between oxygenated fuel (E10) and E85 when it comes to materials selection and corrosion resistance. You'd also need to remap the spark tables even at idle and cruise to properly behave with high alcohol content fuels even if you have the right stoich point. And oh yeah, "E85" isn't always 85% alcohol. It can be anywhere between 70% and 85% depending on the seasonal blend, evaporation, water content, etc. This can significantly shift the stoich point, causing some serious headaches if you don't have a precise alcohol % estimation algorithm.

 

The tune simply needs the stoic value changed and thats it. The loss in power is countered by a rise in timing but thats all there is to it. Your car isnt a flex fuel vehicle and doesnt need a sensor to determine ethanol content since you wont be going back and forth between fuels.

Actually the only other thing is to swap to bigger injectors and more fuel pump.

I am runnng a 96 lb injector on a project car with twin turbos and an upgraded fuel system capable of 1500HP. It runs like a champ. 105 octane is awesome.

The rumor mill persists that there are things in your fuel system that wont handle the ethanol and its just that...rumors.

From Jay Leno's E85 vette to the one in this article,late model GM cars (last 10 years) are fine with E85:
http://www.vetteweb.com/tech/vemp_08...ion/index.html

Locals here in Colorado use it all the time since the high altitude causes us to be FI users. They laugh at the rumor of varying amounts of ethanol in the E85 here stating they can see it on a wideband if it varies and its a tune update seasonally at best. They dont have any issues.

The issue with our car is that you need more fuel pump headroom by 30% since it burns the E85 at that percentage rate higher than gas. 30% more injector than your current power isnt the limitation....the fuel pump has to have enough headroom to pump 30% more volume of fuel. At 13:1 a/f you will have enough fuel pump for close to 600rwhp on gas and about (30% less) 465-470rwhp on E85 and then you need a high volume fuel system. Richer applications with 12:1 or 11.5:1 for FI are considerably lower in HP limitations. 700rwhp FI applications would need a fuel system upwards of 1000HP in capacity.

In this video from you-tube, the parts are shown from a torn down 2000 tahoe that was not a flex fuel vehicle. From spark plugs to fuel lines the E85 vehicle looked better. It runs cleaner and damaged nothing.....at 105k miles.
http://www.youtube.com/watch?v=HuOs1yap8mU