e85 ?s

96mustang21

Registered User
1. will i hurt my engine if i run 25% e85 75% 93
2. what would the octane rating be so i can tune for it
3. will i have to change n e thing for only 25% e85
 
I did a test with E85. I didn't figure out the ratios, but what I would do is put 4 gallons of e-85 in the tank, then top it off with 92 octane gasoline (10% ethanol blended).

My car has 60lb/hr injectors and had no real issues driving around. Adaptive appeared to be able to take care of it (this was before I had the QH and can see what is really going on) keeping AFR right around stoic when in closed loop. In Open loop, say WOT, the standard tune was unable to adapt enough to achieve commanded AFR. With 92 octane E10 (all gas in MN is E10, except for a select few) commanded AFR was 11.5 and the car could achieve that. With E85, command AFR was still 11.5, but actual ended up being more like 12.5 to sometimes 13.1.

Drivability wise, i was testing the E85 blend to combat some low rpm high load pinging (snapping to part throttle in low gear. my static cylinder pressures at low rpm are on the high side). for this, the E85 did cure the detonation at those points. And even though I was seeing 12.5 and higher AFR, I was not getting any noticeable detonation, but certainly it wasn't safe.

The BIG challenge with Pump E85 and tuning is that E85 is not a consistently blended fuel. To be called E85 in Minnesota, it can be anywhere from E70 to E90. My guess is that is the same in other states. And this blend ratio can change from one load to another that they get at the station. Thus if you are going to tune for E85 specifically, you will want to start super green safe, and only ease your way up to pretty green safe. You never will want to be just safe, as just safe with Pump E85 isn't really safe at all.

OTOH, if you want to tune it tight, Rocket Brand, and some other Premier fuel suppliers can supply you with 55gallon drums of E85 that is guaranteed to be consistent. (though there can be differences from barrel to barrel)

if you haven't seen this link, you might find it useful.
http://www.e85mustangs.com/tuning.html
 
I've run my 91 on up to 50/50 E85 and regular 87 unleaded without issue. E85 is roughly 105 octane (depending on 85, 70 or 90% ethanol). So the 50/50 mix with 87 comes out to 96 octane give or take. I also have a LM1 wideband that I'd used to watch the AFR and an EEC tuner for the tuning.

The EEC is set for 14.7 AFR (closed loop) unless in open loop (WOT). Load or throttle position will determine open loop. Stock throttle breakpoint is at about half throttle. With 8-9 gals of each fuel in the tank, it was fine in closed loop in the 14-15 range. I tuned open loop for about 10-11 AFR and after some tweaking, and taking the easy way out with the open loop fuel multiplier, it would hold 10-10.5 and seemed to run harder than with standard 93 octane gasoline. I will note that it smell like an alky burning race car with that much E85. As Car Craft wrote when testing E85, "it smells like running gasoline run through a dirty sock"... they're not far off.

Beyond 50% mix, it would lean hiccup and stutter before going to open loop. And I'd changed my throttle breakpoint to 1/4 throttle. If I had the time, and E85 was significantly cheaper, I'd create a file to run open loop all the time.

Above 25% ethanol, make sure to have stainless steel or some type of plastic/rubber fuel lines that can handle alcohol fuels. Make sure to run all the alcohol out and put straight gasoline in if storing for a period of time as alcohol/ethanol will absorb moisture starting immediately to the point of being nearly useless in 6 months.

Steve
 
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