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Old 11-08-2012, 03:54 PM   #1
ianto303
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Default Not tuned for e85 but is there a safe ratio to add e85 with 91 oct?

Hey guys, I drive a stage 2 2011 sti. Dp and accessport. My car is not tuned for e85 but I heard it was safe to add e85 as long as you put the right ratio or just not too much. Is this perfectly safe without any damage to the car? Does anyone do this? I heard it can give you a Lil more power and the ratios I was hearing are maybe 60% 91 Oct and 40% e85 or maybe 50-50. If anyone can please give me more info I'd appreciate it I wanna give this a try.
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Old 11-08-2012, 04:27 PM   #2
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Quote:
Originally Posted by ianto303 View Post
Hey guys, I drive a stage 2 2011 sti. Dp and accessport. My car is not tuned for e85 but I heard it was safe to add e85 as long as you put the right ratio or just not too much. Is this perfectly safe without any damage to the car? Does anyone do this? I heard it can give you a Lil more power and the ratios I was hearing are maybe 60% 91 Oct and 40% e85 or maybe 50-50. If anyone can please give me more info I'd appreciate it I wanna give this a try.

It will give you absolutely no more power because the car is not tuned (ie timing and boost are not tuned) for e85. You can make significantly more power on e85 because you can run more timing and boost due to the great knock protect the fuel allows. As far as adding e85 to your tank it's best not to due it. If I remember correctly I've read a 30% e85 70% petrol blend would be considered safe, but even then I'd really want to log the car to make sure the fuel trims aren't all out of wack. Honestly I don't think it's worth it though. There are inherent risks in messing with a new fuel blend that you are not correctly tuned for, and the benefits (more knock protection) really wont do much of anything as long as you are properly tuned for the fuel you currently run. If you want to run e85 I highly recommend it, just do it the correct way.
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Old 11-08-2012, 04:29 PM   #3
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This really belongs in engine management forum.

The stock tune can take a fair amount of E85 before running out of ECU adjustment range. However, a basic stage 2 will run out of injector and / or fuel pump before it runs out of ECU adjustment range. so will lean out even if the ECU is given time to adjust fuel trims for the new mix in the tank.

Some of it also depends on how the car is tuned:

There are multiple load ranges that use different fueling trims. These trims also get applied to the open loop fueling map. (For example: If the ECU is adding 5% in closed loop fueling, it will add 5% to the open loop map at that load range too.)

Some tuners will adjust these ranges so that the highest load range is so high, you never get there in closed loop, so there are never any adjustments to the parts of the open loop map that people are in most. If this is the case, you can cause real issues with running lean on just a small% mix of E85.

However, if a tuner leaves these load ranges reasonable, then you can add 20% or more E85, and the ECU will automatically adjust for that (if there is enough fuel pump and injector to do so.)

So, IF you have larger injectors + fuel pump, you need to confirm with your tuner before you go adding E85 to your current tune. If you don't have larger injectors + pump, you definitely don't want to go adding E85, as a Stage 2 is usually very close to maxing out the fuel system.

Last edited by Concillian; 11-08-2012 at 04:35 PM.
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Old 11-08-2012, 05:21 PM   #4
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Quote:
Originally Posted by ianto303 View Post
Hey guys, I drive a stage 2 2011 sti. Dp and accessport. My car is not tuned for e85 but I heard it was safe to add e85 as long as you put the right ratio or just not too much. Is this perfectly safe without any damage to the car? Does anyone do this? I heard it can give you a Lil more power and the ratios I was hearing are maybe 60% 91 Oct and 40% e85 or maybe 50-50. If anyone can please give me more info I'd appreciate it I wanna give this a try.
Nawww, bro.


A splash for octane boosting is cool, but not 60/40, not even 80/20. I'm talking like 97/3! 105 octane (e85) will boost the crap out of 93 in a flash, no need on the regular.

I would only do this if I had a track day or was beating the piss out of her.
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Old 11-08-2012, 05:57 PM   #5
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Not sure about adding E85 to bump 91 or 93, but by adding race gas you'd be gaining thermal stability (always a good thing in a race/stressful enviornment) and that's about it. Now if your car was tuned to take advantage of racegas, that would be a different matter. But it would be kind of silly to spend the money on a racegas tune for a stock car where you can put the money in going stage 2 and have safe, permanent gains.

edit: Errrr, you're already stage 2...soooo I guess upgrade your fuel system and get a proper tune so you can properly take advantage of the E85. Or if you're on the quest for more power put the money towards a new turbo...which will still require a new fuel set-up sooo I dont know what to suggest
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Old 11-08-2012, 06:56 PM   #6
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Cool thanks for all those who replied. Yea ill just wait and save up for my e85 tune along with the injectors and fuel pump.
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Old 11-08-2012, 08:23 PM   #7
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You can run up to 20%, However, Its not going to add any power.

C
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Old 11-08-2012, 11:52 PM   #8
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Its not going to add any power.
This.

Last edited by NSFW; 11-09-2012 at 03:13 PM.
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Old 11-08-2012, 10:55 PM   #9
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Yeah I've been running 20% E85 for the last couple of years with no problems. The car loves it.
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Old 11-09-2012, 03:24 PM   #10
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Originally Posted by Illicit1 View Post
Yeah I've been running 20% E85 for the last couple of years with no problems. The car loves it.
On an already tuned car that nearly maxes the fuel system before mixing in E85? Or a stock tune?

Because on a stock tune, go ahead, mix in 20% E85, the ECU will adjust and you have room on injectors, it's all good... But on a stage 2 tune that is close to maxing the stock fuel system already? Not a good idea to mix in E85.

This is the point I thought I made in post #3, but I guess it was TL,DR.
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Old 11-15-2012, 03:56 PM   #11
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Quote:
Originally Posted by Concillian View Post
Because on a stock tune, go ahead, mix in 20% E85, the ECU will adjust and you have room on injectors, it's all good...
So could e85 be used as an octane booster for a stock '07 WRX that only has access to crappy 91 gas?
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Old 11-15-2012, 04:00 PM   #12
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So could e85 be used as an octane booster for a stock '07 WRX that only has access to crappy 91 gas?
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Old 11-16-2012, 02:59 PM   #13
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Originally Posted by B1RDD0G View Post
So could e85 be used as an octane booster for a stock '07 WRX that only has access to crappy 91 gas?

E85 is best used consistently, since you won't have to worry about whether the long term fueling trims are in the right place or not. When used periodically, you can have issues. Not only the fueling trims, but if your timing is getting retarded on 91, everytime you move back to 91 from an E85 mix, you're subjecting the engine to re-learning the knock threshold by knocking and pulling timing. re-setting the ECU each time you change your mix might be a better option.

It can be used as an octane booster, but since it changes the fueling, you have to be careful using it that way. You can't just fill a tank 20% E85 and take off, you need to give time for the ECU to adjust it's long term fuel trims, and you need to be careful in how you go back to 91.

A stock tune has the fueling system headroom for an E85 mix, and it won't cause any problems up to the point you get a CEL... provided you take caution to avoid the issues I just discussed.

You can also use an E85 mix to help pass inspection. I ran 2 tanks of ~20% mix through my wife's 230k mile Corolla. It made the cat inefficiency CEL go away and I got it smogged so I don't have to worry about that for another couple years (if it's still running then.)
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Old 11-16-2012, 04:03 PM   #14
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Originally Posted by Concillian View Post
E85 is best used consistently, since you won't have to worry about whether the long term fueling trims are in the right place or not. When used periodically, you can have issues. Not only the fueling trims, but if your timing is getting retarded on 91, everytime you move back to 91 from an E85 mix, you're subjecting the engine to re-learning the knock threshold by knocking and pulling timing. re-setting the ECU each time you change your mix might be a better option.

It can be used as an octane booster, but since it changes the fueling, you have to be careful using it that way. You can't just fill a tank 20% E85 and take off, you need to give time for the ECU to adjust it's long term fuel trims, and you need to be careful in how you go back to 91.

A stock tune has the fueling system headroom for an E85 mix, and it won't cause any problems up to the point you get a CEL... provided you take caution to avoid the issues I just discussed.

You can also use an E85 mix to help pass inspection. I ran 2 tanks of ~20% mix through my wife's 230k mile Corolla. It made the cat inefficiency CEL go away and I got it smogged so I don't have to worry about that for another couple years (if it's still running then.)
Good info here Thanks.

Don't have to worry about vehicle inspections at all here, much less an emissions test.
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Old 11-09-2012, 03:38 AM   #15
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So Clark and nsfw, you've both run stage2 91oct ap ots maps on 20% e85?

What was the idc? Afr?
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Old 11-09-2012, 03:13 PM   #16
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Nope. Edited accordingly.
There's no E85 in my area, but I'm confident enough in my understanding of the chemical properties to have no doubt that it'd be a waste of time to mix it in without retuning.
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Old 11-09-2012, 03:17 PM   #17
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It just seems like something weird to try on a stage2 car where the injectors are already maxed out.
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Old 11-09-2012, 03:44 PM   #18
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My advice is not to waist time, I agree with the other posters, unless you tune for E85, theres no real gains to it outside of it being cheaper than premium fuel. When you run strait e85 is a different story.
I can tell you that on my tune (1000cc injectors, Stock vf52 turbo, intake, fmic, and 3" turboback catless exhaust) I had my tuner do both an E85 tune and 93oct tune. Same boost levels (20psi becuase I didnt replace my BCS maxed it out at 20) the E85 had 45 more wheel horse power and 40 more wheel torque just by running e85.
This is just my opinion, i do not reguard this as fact haha.
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Old 11-09-2012, 04:24 PM   #19
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The only way I could see it increasing power was if you were consistantly pulling timing. And if you tune is pulling timing on a regular basis, you need better tuning, mixing E85 would only be a band aid fix.
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Old 11-12-2012, 11:07 AM   #20
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Dont bother - get set up specifically to run E or throw a meth kit on top of your 91 - or just stick to your piss water mapping.
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Old 11-12-2012, 11:52 AM   #21
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It's really not great at all for adding power vs what you're tuned for; for lowering your knock threshold, yes, it is good. Again, a 'splash' will raise your effective octane level, make you a little bit safer if you're beating on your motor under tough conditions. (Track, etc.)
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Old 11-15-2012, 04:43 PM   #22
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It sure can. You can use up to 20% without to much trouble. Unless your fuel already has 10 or 15% alcohol in it. There is a label on the pump.

Just dont get carried away with adding to much. Dont expect power gains unless, the tune/setup is octane octane deficient. Then, if it stops the knock it worked.

If the car is in tune and not detonatiing now, Then adding the E85 wont help at all.

C
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Old 11-15-2012, 04:54 PM   #23
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I think the fuel here is very borderline (especially the winter mix) and I have been investigating different ways to bump the octane a point or two. Don't usually notice any problems but sometimes it can be a little "surgy" like the ECU is working too hard to keep everything happy. I had heard that up to a couple gallons of E85 would be OK and give a boost to the octane. I would be perfectly happy with 93 gas if anyone had it around here anymore.
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Old 11-15-2012, 05:23 PM   #24
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Why don't you just flash a 91 octane map see if there is anyone local with a tactrix cable or buy a cobb ap they have 91 oct maps
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Old 11-16-2012, 09:16 AM   #25
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Originally Posted by k04sti View Post
Why don't you just flash a 91 octane map see if there is anyone local with a tactrix cable or buy a cobb ap they have 91 oct maps
Right now, I'm just looking for options for a small octane boost. Car has a factory tune, so should already be set for 91 gas but I think the gas is questionable. I plan some mods in the future, but not right now.
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