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man114

E85 and exhaust system health, steamier exhaust?

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While I have noticed that E85 leaves fewer deposits and cleans what is in there out, I'm wondering if there is a potential downside, that being the health of the exhaust system. Both vehicles I run this in are conversions but I don't know how much a difference there would be in an actual flex fuel.

 

First I'm sure most of us have smelled the exhaust off the E85, or lack of smell. Unlike gas it hardly smells like much, a slight twang of corn seems present, but not much else. However I think it burns wetter. I'm not sure how to quite describe it, but if you've ever started your car on a cold winter day you see the clouds of exhaust from the present moisture byproduct of combustion.

 

E85 seems worse in the moisture department, but I'm not sure the direct cause, if it is the moisture it absorbs or it burns more completely (hence the lack of real smell). I've noticed though that if I just idle the car in the driveway it is quite steamy on a humid day. Its been hovering around 90% humidity so if I just start and idle the vehicle after a few minutes of running steam is present I'm not talking billowy clouds of steam, but if you look its there and noticable and the exhaust feels wetter. If you don't take the vehicle and get it good and hot (as on the highway), there is a quite a bit of moisture in the exhaust seemingly a lot more than if you were running regular gas. Idling you can watch water drip out, if its humid there is noticable faint puffs of steam.

 

I just did some work on the Grand Marquis and this, with new iridium plugs, is actually more noticable than before. I leaned the conversion kit out a bit but I'm not sure if it was from that (perhaps I was running it too rich if the old plugs were inefficient it certainly seems to run better now) or if the E85 absorbed water from the humid air on the week and a half I was doing the work on it (tank was down 1/4).

 

I drove the truck today, and fresh filled it with E85. I noticed that unless I got it up on the highway it was the same basic thing. If I was doing city driving you could see water sitting on the bottom portion of the tail pipe and didn't dry out until I heated up the enigne with highway driving. After letting it sit two hours you got some nice steam out of the exhaust until you actually started driving it until it got hot. I tested this against a modern fuel injected car running gas an an older car running gas, the older car, which seems to run richer at startup behaved more akin to the E85 results.

 

I don't see this posing much of a problem if you drive until you heat the exhaust up, but if you're sitting idling the thing (as I did with the Grand Marquis while testing some of my work), I could see potentially more water building up in the exhaust and rusting things out faster. I can however say that gas isn't quite the same in this respect.

 

I'm not really concerned, the GM is more than due for a new exhaust anyway a little bit over a course of a week and a half is trivial, if it rusts out from whatever moisture I left in the exhaust then fine. I'm just wondering how things would pan out if you had E85 in a car you drove in the winter, and you spent a lot of time idling it keeping it thawed/warm between driving. Or if you frequently idled a car for a long period when running E85, or used mainly for short city trips. I'd think if there actually is extra moisture, which there seems to be, would it rust the exhaust from the inside, or would the fact that its less corrosive and toxic smelling balance things out?

 

 

 

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When you burn ethanol in an internal combustion engine it produces mainly two things. CO2 and water. Gasoline also condenses water in the exhaust, so the same methods we use to prevent the exhaust from rusting with gas will work with ethanol. Getting the engine to operating temperature, everything in the exhaust system hot, and not shutting it off after a short run to the mail box will prolong the life of your exhaust system.

 

Water is a problem in other areas, but not just because of the fuel. It condenses inside the engine and will dilute the oil if the engine is not allowed to get enough heat in the oil to boil off the water. The current high performance thinking in the aftermarket is to run the engine cooler with a 160F thermostat. On ethanol that wont let the engine get hot enough to boil the water out of the oil. Modern cars are more efficient with hotter engines, and they tend to run in the 210F-230F range in normal operation, so provided you arent taking short trips and shutting it off before its warm, the water will be boiled out.

 

Ethanol runs much cooler than gasoline since it has far less waste heat that needs to be expelled through the radiator and exhaust system. That means you might have to run it a bit longer to get it warm enough to control the water that naturally collects in engines from heat cycling and humidity. What that means is if you have a 5 minute commute to work, take the scenic route to ensure your engine gets warm enough, or use a block heater to keep heat in the engine. If your commute to work is 30 min or so, then you shouldnt have a problem. Keep in mind cars are different and warm to operating temp at different rates, so its a general guideline, not a cold hard fact that you have to run it 30 minutes. Usually mine are warm enough within three miles of driving at 55mph.

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I usually use a 190 or 195 degree thermostat, maybe higher if the car will allow, this avoids problems in the winter around here plus gives you heat. If you try using a 160 (I did it in my old F150 back in the day to keep the engine cooler during heavy hauling), you get lukewarm heater air if its really cold out which doesn't quite cut it in the cold winter.

 

I just thought of the potential of it rusting the inside of the exhaust if you left it idling around a lot or did a lot of short trips. I had been doing some tuneup work on the Grand Marquis and in the process drained the cooling system, I noticed it mainly when idling the car to refill the cooling system because I had to idle the car until warm to get the thermostat to open since the car has no radiator cap. If the car doesn't get warm, you get quite a bit of steam. Of course changing the plugs and mass airflow sensor probably did some disruption of things too as the car was previously running lean due to the MAF sensor. I also reset the computer too at this time. This coupled with the cooler ambient air temps at this time of year vs. the summer and its been pretty noticable that unless you get it warm there is more steam with the E85 than with gas.

 

The couple of times I did it with the Grand Marquis won't make any long term difference and the exhaust at 78k miles is pretty old as it is, I was less concerned about the engine as I had to let it run until it was hot to open the thermostat and circulate the coolant for a few minutes, but a long exhaust when the weather is cool takes a bit longer to warm up at those low engine speeds.

 

My commute is 10 miles all at 55, either is plenty hot by then that it wouldn't be an issue, however if you're doing a lot of short drives on E85 I could see a problem developing if the car isn't getting hot.

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First - all this 'ethanol sucking water out of the air' crap is mainly a myth.  It may pick up a tiny bit if you leave your gas cap off...in a rain storm...and the temperature changes +/- 80 degrees each day.  But other than that, chances are slim it's going to absorb any notable moisture.  Even if it did, when you work out the numbers, burning a gallon of ethanol makes about a gallon of water, so even if it absorbed 10% water, you'd wouldn't notice a difference in steam.

 

If you look at the chemical formulas:  ethanol = C2H5OH (2 carbon, 6 hydrogen) and approximate gasoline as octane (C8H18)

you can see the ratio of hydrogen to carbon is much higher with ethanol (3:1) vs gasoline (2.25:1)  Other  things would go into the formula as well, but there is certainly a potential for ethanol to make more steam compared to gas, simply because more of the fuel is hydrogen.

 

But the biggest thing is probably the local conditions...temperature, humidity, dew point, etc.  These will have a big impact on how much steam you see and a slight difference in one or the other could make the difference between a huge cloud of steam and a small wisp.

 

As far as the exhaust system, that would be a bit of a toss-up.  E85 is definitely lighter in sulfur compared to gas, so less sulfuric acid.  Hard to say on NOx - sometimes higher, sometimes lower.  E85 doesn't make the carbon soot which can offer a bit of protection to the inside of the pipe.  Overall, I don't think it would be terribly worse, though may not be much better, either.

 

On the good side, most modern exhaust systems are stainless steel - so they should last for years in either case.

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I have not had to replace an exhaust system part in years- maybe I have been lucky but so much of it is stainless, even on FFVs. Of course the fleet cars pound out about 75,000 miles/year so getting to 210,000 or more happens fast on E85. My personal stuff also has not needed exhausts but miles range from 80,000 to 215,000 but are mostly E20+. The '01 S10 is an FFV though and is still all original on E85 fuel.

 

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I don't see any issue if you're driving long distances or warming it up well. I just see this as a potential problem if you were doing a lot of city driving or short trips. I'd imagine it would rust the inside of the exhaust out, maybe not on stainless steel, but if you were driving over a period of many years, regardless you'll eventually need another exhaust, or at least muffler, and often times they'll replace the muffler and the pipes at the same time, this stuff is usually cheap steel.

 

I'm still running the original exhaust from 1997 on the Grand Marquis, however these are all observations. Curious how this would play out in the long term. If it would even amount to anything is debateable. Of course the old Crown Vic circa 1984 would produce steam like no tomorrow during its "warm up" while the engine raced to warm up the throttle body and I can't say it went though exhausts that quickly either.

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