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HuskerFlex

lean burn on e85...

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OK, I've been thinking about this for a while, and since Oberbort brought it up on the EToM query...

 

if "running lean" means you are using less fuel in your fuel:air ratio... this means you would be increasing efficiency...

 

you can't run too lean, or you will be running your engine too hot, and will do serious damage, and emissions will be worse...

 

BUT if ethanol burns cooler and burns cleaner... would it stand to reason that you could run leaner on e85 then you could on e0 (regular gas), with out running any hotter or emitting any more pollution?

 

Does my logic make any sense?

 

I was wondering if the on-board diagnostic computer/sensors would agree to this, or if you would have to change them somehow....  ( :-[i'm a complete novice at this, just got me thinking...)

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OK, I've been thinking about this for a while, and since Oberbort brought it up on the EToM query...

 

if "running lean" means you are using less fuel in your fuel:air ratio... this means you would be increasing efficiency...

 

you can't run too lean, or you will be running your engine too hot, and will do serious damage, and emissions will be worse...

 

BUT if ethanol burns cooler and burns cleaner... would it stand to reason that you could run leaner on e85 then you could on e0 (regular gas), with out running any hotter or emitting any more pollution?

 

Does my logic make any sense?

 

I was wondering if the on-board diagnostic computer/sensors would agree to this, or if you would have to change them somehow....  ( :-[i'm a complete novice at this, just got me thinking...)

 

Yes you can run leaner..to a point of course..this is why you see home conversion to E85 getting better MPG than Production Model FFV's..

 

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It also depends on the parameters in the ECM programing. If the ECM is an OBDII and it senses a lean condition, it will tell the injectors to stay open longer in an attempt to add more fuel and at lower RPM with less demand that will cause it to overfuel and run very rich. You wont notice an over rich condition as the power doesnt drop off nearly as much on ethanol as it does on an over rich gas engine, but it will use LOTS more fuel.

 

You still have to get the air fuel ratio close enough for the engine to make decent power without melting anything, you can only go so lean before you start losing power and that will cost you mileage too. Using less fuel doesnt always come from putting less in the engine, you can improve mileage by increasing the power the engine makes provided you increase it at the lower RPM ranges rather than the higher RPM. If the engine isnt working as hard to move the same mass, it will use less fuel doing it than an engine that is laboring to do the same job. Timing, fuel mix, cam timing, and a whole host of other things have an impact on it.

 

Typically people will try to increase an engines power by raising the RPM range it operates in, or by adding more air to it with a supercharger/turbo. It doesnt have to run at a higher RPM if you maximize the power it is making at the RPM it normally sees while driving around on public roads, and that is idle to about 3000 rpm. Camshafts play a HUGE role in that, so does timing and airflow, but you still need to feed the engine enough fuel that it can do its job, and under certain conditions it doesnt need much fuel and it can run very lean. It just cant do it all the time.

 

The Pontiac guys are asking me why I want a 13:1 engine with such a tiny cam and stock heads, because it will be down on power from what it could be with more airflow. I have a race car, this is not it, and it just doesnt make sense to them as most people equate high compression and camshaft swaps with race engines and high RPM. Just like most people equate rich with using too much gas and lean with not using much, when you can use more running too lean than you might running rich.

 

EFI has much better fuel control over the low RPM ranges than does a carb, but a carb can make more power than EFI on the same engine. The difference is how well the fuel is fed to the engine depending on what it needs to do what you are asking it to do. Some carbs can get very close to EFI for mileage and drivability, but it takes more work and trial and error to figure it out for whatever weather conditions you are having than it does to change the parameters in the ECM and the ECM can adjust as it goes to the weather where a carb cannot. So the EFI can run it lean when it is able to do the work needed without as much fuel but not so much that it affects the emissions.

 

Make sense? :)

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ECU's using a wide-band O2 sensor typically do better as well.

 

A wide band ECU is trusted more by the ECU to the point where the vehicle can become undriveable, if set too lean, where a narrow band sensor under the same conditions, will probably just go into open loop.

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Husker, my concern and question, also. The newer (after '96) OBD11 systems appear to adjust better.

 

Non flex vehicles suffer with cold start up. Hard cold start such as stalling and stumbling not dangerous to your engine....just a inconvenience for the first few miles in colder temps.  Either you live with the problem, mix in some regular, or utilize a plug in engine heater. The plug in engine heater the most economical (better mileage quicker) and minimal pollution choice.

 

Lean burn has the potential to burn valves or propagate damaging engine knock. The danger increases with higher hp demands of engine and long duration of subjecting the engine to this high horsepower. Typical conditions with heavy cargo, pulling trailers, uphill mountain, and driving fast. Conditions of maximum torque and/or high rpm. Conditions where the engine is consuming maximum fuel. 

 

Conversely, high altitude driving less of a danger. The danger increases if you attempt to advance timing to obtain better mileage.  Not sure the effect of hot outside temperature or humidity? High temps and low humidity probably more of a threat?

 

Having posted this, I am aware of no actual internal engine damage burning E85. My vehicles usually burn E85 OBD1 vehicles (2 years). Now, I don't travel 80mph nor have a turbo. Your best protection, take it easy and don't demand high hp of your engine.

 

I would like a post or section of E85 to list actual engine damage of E85 fuel. Damage with credible docs or trust worthy testimony. I haven't discovered much. Mechanics often fault E85 for their expensive repairs, but that is suspect as other mechanics have no such experience. It can't be that pervasive if most consumers of E85 have no such experience. Lets come clean like the Toyota executives? Post how many engines you had to throw away? And no, the hot rod exploits don't count. 

 

Not many problems out their. Do a Google and find much information on potential problems. Not much on actual problems. Now, the hot rod group has all kinds of exploits with all fuels. 

 

List problems:

 

fuel pumps

filters

valves

pistons

corrosion

plastic deterioration

Injectors

 

Maybe we can get a handle on any problems? And the severity?

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I would like a post or section of E85 to list actual engine damage of E85 fuel. Damage with credible docs or trust worthy testimony. I haven't discovered much.

 

That is because there is essentially zero problems with E85 "due to the fuel". Just like gasoline it is not the fuel that causes the problems it is stupid tuners that do silly things that kill engines. If you tune it correctly E85 is a much more forgiving fuel than common gasoline. Stunts that will kill and engine on gasoline in a heart beat, will not hurt the engine in almost all cases on E85. If you kill an engine on E85 you would have killed it far sooner doing the same dumb stunt on gasoline.

 

Example: I know guys that had turbo boost control hoses blow off and have boost spikes to over 30psi on E85. The same event on even good racing gasoline would have blown the top out of a piston due to detonation. I have run over 7 psi boost on 15:1 AFR (not intentionally) with no harm to the engine on E85. The same on gasoline would have burned a piston or killed it with detonation.

 

Alcohol fuels are slightly more prone to pre-ignition than gasoline but a sensible tune should never even get close to that situation in the first place. Common summer blend E85 acts about like 112 octane gasoline, so anything you can do in a good racing gasoline you can do on summer blend E85 and in many cases you can do more.

 

E85 has wider flammability limits so it will "allow" both much richer and much leaner fuel air mixtures than gasoline. Just because it will allow you to run those extreme mixtures does not make it a good idea. Same goes for stupid amounts of ignition advance. More engines are killed by advance happy tuners than just about anything else.

 

There is no cure for stupid tuning and no fuel is immune to the consequences of making dumb choices. It is not the "fuels fault" in those cases it is the "fools fault".

 

Larry

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http://e85vehicles.com/e85/index.php/topic,1586

 

So basically, my last three tanks have been within a few tenths of a mpg regardless of whether I ran the [lean burn] circuit 100% of the time, less than half the time - and/or towed 550 pounds of equipment!

 

Info on WBO2S operation:

 

http://e85vehicles.com/e85/index.php/topic,1573.msg8938.html#msg8938

 

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Good point HR, it's not the fuel, but the settings.

 

Question: Has anyone suffered damage with straight E85 in non-flex auto's?

 

This has been asked before with acceptable advice of "don't push your luck within the high hp demands". But nobody recounts of real damage of engine. The worst case seems to trigger a engine fault light. The OBD1 engine control modules not particularly sensitive to that.

 

Some reports of changing fuel filter as precaution. Dan experienced a clogged oil filter, more contributive to short trip cold engine winter operation conditions with a filter known to exhibit this problem.  I've read a report of carburetor accel pumps corroding, one post. 

 

Remember the hype or advice on changing tanks, fuel lines, fuel filters, "O" rings, flexible hose, spark plugs, oil change interval, synthetic lube, timing, injectors, electronic box, etc, etc. ? People were scared to death of fueling with E85. Only the brave souls with old cars to experiment. Funny, how many years have we been gaining knowledge? And whats the verdict? Personally, will run straight E85 in non flex vehicle until credible information presents itself that running lean will hurt the engine under low hp requirements.  Now, when towing a large trailer will switch to E10, as not out to push the envelope as in fools game.  As you post the fuel is more forgiving.  Per Husker question....appears the fuel not nearly as critical upon running lean burn.  Sure a loss of hp, but if you demanding max hp you shouldn't be running E85 in a non flex engine. Right?

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No problem on my 88 and 86 turbo Subaru wagons on E85. The turbo run a bit lean/hot on straight E85 but its radiator needs to be replaced (all the fins are banged shut from rocks hitting the front of the radiator. That is only under high load where it is in open loop fueling (ie reading directly off the ECU fuel look up tables). In closed loop fueling both of them will adapt over time to higher blends but since I have made no compensations for the fuel of any kind I can only run straight E85 in hot weather with both of them as they have major starting problems when temps get down in the 60's and below.

 

With oversized injectors or some other modification such as adjustable fuel pressure to richen the mixture appropriately I am sure they would do as well as the WRX.

 

Lean mixture is only an issue in carburated engines that have not been re-jetted for the fuel and EFI engines in open loop fueling which is usually  not seen except when accelerating or pulling a hill in normal driving. In light throttle cruise EFI setups will try to use the closed loop fuel trims to compensate for the fuel, and seem to do an acceptable job at least up to 30% to 50% blends on almost all cars.

 

Larry

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