High ethanol mixtures

Somewhat related to an ongoing thread, but different-

Our local newspaper had an article today about folks who do not have flex fuel vehicles, but do burn high ratios of ethanol. They fill from two pumps, one E85, one gasoline, and so tailor their own mixtures.

Since ethanol requires a much richer mixture than gasoline, doesn't this substantially lean out the mixture? I know ethanol will burn quite rich, but how LEAN will it go? Also, doesn't this risk valves and pistons? I remember cases of folks with race cars running lean mixtures and doing a lot of damage.

Also, this brings up a question. I understand flex fuel cars have a sensor in the fuel system that measures the gasoline/ethanol mixture ratio so ithe EFI can adjust the mixture accordingly. What kind of sensor is that? I used to work in sensor R&D, but chemical sensors are not my strong point.

Reply to
Don Stauffer in Minnesota
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All they need to do is keep the mixture within the range that their car's O2 sensors, computer, and injectors can handle. If they do this, then the computer will hold the mixture correctly and nothing bad will happen wrt mixture. as far as higher % of ethanol doing bad things to the seals, plastics, etc... that's another story.

I thought it was all software using a wider band O2 sensor in a typical FFV. I suppose a fuel mix sensor might be needed so there aren't stumbles right after a fillup with a drastically different mixture.

The systems that advance timing and otherwise take advantage of ethanol's octane advantage probably do have some sort of fuel mix sensor but I have no idea how it would work.

Reply to
Brent P

The flex fuel sensor is basically a capacitor, the capacitance changes because the dielectric constant of ethanol differs from gasoline.

Reply to
Mark Olson

I havent researched it, but I doubt these sensors are chemical specific; i.e., I suspect they measure some other parameter like thermal conductivity which can be related back to blends of hydrocarbon fuel with ethanol. That is often the case. It wouldnt, perhaps, be impossible to develop a specific sensor, but I suspect that would be expensive and troublesome.

I have always thought that an alcohol flame was a cooler flame than a gasoline one, but maybe this is just a preconception. Also, alcohol has a reasonably high octane rating, so maybe this offsets some of the preignition and temperature issues.. It is not an area that I have had any reason to research before now.

Reply to
HLS

I tried running on 1/3 E85 and 2/3 normal E05 (gas here have 5% ethanol) in my 1996 audi, and it had no problem adapting to the resulting E32 (by my calculations).

As long as the mixtures AFR for lambda 1 is within the permissable range of the engine management system, it shouldn't be a problem.

Reply to
Thomas Tornblom

If (theres a loaded word) they can keep the mix within the range that the engine and sensors can tolerate it will work BUT they will be losing a lot of power because of the leaner mix. It also is likely to be doing some damage to the engine as well.

They use a fuel composition sensor in the line feeding the engine. On GM flex fuel equipped vehicles it is installed near the fuel filter under the vehicle. On the trucks it is just below the drivers seat location on the cars it is either in the rear near the tank or up front just below the master cylinder.

It looks at conductivity and a couple other items to determine the alcohol content. It is basically preset to look for a few blends though. Straight gasoline - E10 is one mix, Then it looks for E15-about E50 as another step, then E50 - E85 is another step. It then tells the computer to use the sensor maps and mix tables for those different blends.

Reply to
Steve W.

I don't know, but I _do_ know that just having the single feedback loop from the O2 sensor allows you to run pretty outrageous mixtures through a car with EFI.... the sensor output will guide the computer to leaning or enriching the mixture. The problem is that if you get too far out of range, the computer panics and decides something must be wrong with the sensor.

I know that my '85 BMW 535i definitely does not run well on e85, but that with the ECU module that was sold in Mexico, it is able to deal with e85, presumably due to software changes made to accomodate lousy fuels.

And, of course, with an old carb, it's just a matter of drilling the jets out a little bit to enrichen the mixture, but those systems operate open-loop.

The issue with a lot of the older vehicles is that they have hoses and seals that can't handle ethanol. That's was not impossible to deal with in the seventies, and it's probably a lot easier to deal with today. I can state for sure that all of the fuel hoses and seals in my '85 have all been replaced in the last five years and presumably the replacements should all be fine with ethanol. If they aren't, I should know it shortly.

--scott

Reply to
Scott Dorsey

"Steve W." wrote in news:g1phup$2ti$ snipped-for-privacy@aioe.org:

It should do no eng damage, why you think it should I don`t understand. It will not run lean, the O2 sensor will enrichen it as long as it is within range of the fuel inj to richen it up. it my have a slight power loss because of non specific achalol software but other than less milage and power it should do no harm. KB

Reply to
Kevin

It will run lean simply because the alcohol will act as an oxidizer and the extra O2 will cause the sensors to back the mix down to lower the O2 count in the exhaust. That is one of the changes the sensor also makes to the fuel map in the ECM. It changes the O2 mapping to allow the higher O2 and not lean out the E85 mix. Take a look at a the exhaust with a gas tester and you will find the problem real quick.

Reply to
Steve W.

Aha! This is the first good explanation I have heard! Thank you!

--scott

Reply to
Scott Dorsey

snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:g1regc$9d3$1 @panix2.panix.com:

except it is incorect. the changes to a E85 software is to increase the A/F ratio, and timing increase, becaue the lower energy content of ethanol requires it to be richer. the extra oxy in the fuel only helps the burn to be conplete, there is not enough extra to change the ratio to be lean. it is a very slight increase conpaired to the air content already in the cyl. KB

Reply to
Kevin

Because I have seen folks lean out their race car engines and rapidly burn valves and pistons. Engines will run on a lean mixture that will ignite, but provide insufficient evaporative cooling to the top end.

Reply to
Don Stauffer in Minnesota

Don Stauffer in Minnesota wrote in news: snipped-for-privacy@c58g2000hsc.googlegroups.com:

your talking a carb car vers FI not even remotly the same poss of running lean. It would trip a light long before it can cause damage. KB

Reply to
Kevin

If there is more O2 sensed by the oxygen sensor, won't the mixture be richened to compensate, rather than leaned out?

Reply to
Tim B

Yes it will.

Reply to
Mike

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