E85 as a solution to my detonation problems?

[barichardson5727]

During acceleration I experience heavy detonation. My motor has a pretty high compression ration which I believe to be the main culprit of my problems and it seems that 93 octane just isn't high enough with my current motor setup. Since E85 provides equivalent to 105 octane and is readily available in my area I have been considering making the conversion. Decreased mileage and availability are non-issues to me. If I cared about mileage I wouldn't have built this motor.

 

My main concern is that since I am still running SU carbs I do not know if I run the risk of ruining my carbs by running E85 through them since ethanol is more corrosive than straight gasoline. If anyone has tried E85 with SU carbs I am interested in hearing your results. I am not worried about the rest of the fuel system since everything else can be made compatible with ethanol fairly easily.

 

If E85 would not be a suitable solution or if you have any other ideas as to why I am experiencing detonation issues I am open to any suggestions.

 

For reference my motor is a 3.1L L28 w/ 89mm flat-top pistons, E31 head w/ oversized valves. I am also running modified SU carbs to compensate for the greater fuel demads of the larger motor.

 

I have done a bit of searching on this topic, but it seems like every thread goes off-topic with people providing their political beliefs regarding alternate fuels. This is not the place for that discussion. I would like to keep on the topic of whether or not E85 would be a suitable solution to the problems I have been having. Keep any political views to yourselves please.

[jc052685]

I am not sure that su carbs are up to the task of flowing the required amount of fuel you would need. You might want to look into a setup like this.

 

http://forums.hybridz.org/showthread.php?t=124201

 

As far as the them holding up to e85, I think that would be a simple chore. BTW, its methanal that is thr really corrosive one. aaaaaaaaaaaaaaaaaae85 is not nearly as bad.

[Lazeum]

Have you checked other items such as timing or heat range of the plugs?

 

I had some detonation issues I get rid of them by reducing the advance. I've always thought I was running lean with my carbs but that was not true.

I'm running 28-29° TOTAL advance. Which is not that much compare to similar setups I could campare mine with (usually people are at 34-36° total adv.).

My setup is L28, flat top, N42, 3 x Weber, 274° cam, MSD ignition

 

To go back to your original question, E85 should help but that would not solve the issue in my opinion. You should be able to run with 93 if your CR is around 10-11 (higher would be another story....)

I've always heard E85 is kind of corrosive for aluminum. However, most of current cars have aluminum parts (intake, Throttle Body, etc...)

You should also check the fuel pump and the fuel lines to see if this would not be something to check also.

[burninator]

I'd agree that with E85 it'll require a lot more fuel. You'll have to experiment with needles and such possibly even a higher flowing pump. Are you using a stock mechanical fuel pump? I'd be more worried about the ethanol harming the fuel lines or the pump than the carbs. I hadn't heard that it was bad for aluminum, but it will eat plastic and rubber that isn't formulated to handle it.

[jc052685]

E85 will require nearly twice as much fuel flow for the same power levels.

[barichardson5727]

Thanks for the recommendations. I plan to check my advance this weekend, hopefully it turns out to be something easy like that. I am currently using a stock electric fuel pump (4psi iirc). I have a new carter 6psi electric fuel pump that I need to install. That should take care of any issues I may be having with getting enough fuel to the carbs.

 

I was already planning are to convert over to an ITB EFI setup in the future, but I am still looking into all of my options since EFI is pretty new to me and I don't want to spend that much money without plenty of research. That SU EFI setup was pretty cool and I have a few extra manifolds to experiment with if I decide to go that route. I guess the only thing holding me back is that I would have to remove the head again and cut the notches out for the injectors, but that shouldn't be very difficult.

[TimZ]

E85 will require nearly twice as much fuel flow for the same power levels.

 

Probably more like 1.5 - 1.7. Max power rich for turbo engines on e85 is down around 7:1 AFR. You can probably go leaner on an NA setup. Also, at max power rich you should expect ~10% more power.

 

E85 isn't great on bare aluminum, although there seem to be pently of people out there doing just fine with it. Simple fix is to find an anodizing shop and have the aluminum bits anodized (it's not that expensive). Old rubber hoses should be replaced with compatible ones (not expensive and not hard to find - NAPA's fuel hose is compatible).

 

Here's the one that might be a probem with SU's - NO BRASS. I would have guessed that there were brass bits on the inside of an SU. Can you get non-brass replacement parts?

 

Do a search on E85 - I know I've gone over this in more detail before.

 

I will say this - once you are up and running on E85, you won't want to go back to gasoline!

[510six]

The brass parts inside the SU carbs could be nickle plated. I used a few nickle plated brass parts in my E85 secondary injection system, the nickle plating held up just fine even when the setup had methanol in it there were no signs of corrosion.