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Fuel Choice

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The most practical choice is a turbocharged engine, but it has to have proper engine management changes to make it work. The solution would be to build a small displacement engine (about 2 liters - 122 CID) engine. In most turbocharged engines today they have a base (mechanical) compression ratio of 8:1 so they can run high boost (about 14 psi).

 

Instead of that build the engine with a 9:1 base compression ratio -- that gives it descent gasoline performance off boost on common gasoline, but on E85 you could boost it to 14 psi or even more.

The high performance guys are able to run 35 psi boost on 8:1 compression engines of this size on straight E85.

 

You would also need an engine management system that alters the boost profile based on the fuel composition. It would run 2-3 psi boost on gasoline. Just enough to warm the intake air charge and improve atomization, but not enough to cause detonation. Then as your fuel blend increased toward straight E85 it would richen the fuel air mixture appropriately and jack the boost up to between 14-20 psi max.

 

NA on gasoline the engine would put out around 100-110 hp, on E85 it would cruise at similar power levels but at WOT could deliver 300+ hp.

 

It would not take but one tank of E85 before the owners would run E85 every time they could find it.

 

 

I have essentially this setup in my Subaru 86 turbo wagon. The engine was rated at the factory at about 100 hp on gasoline, but this engine is running the NA short block for a higher 9:1 compression ratio and I limit the boost to 6 psi.

 

I really don't need any more boost that that! It is a front wheel drive and if I try to hard to accelerate from a stop light it just spins the front tires ;)

 

It gets 27 mpg on gasoline in daily driving, E85 fuel mileage is down a bit from that but I have no engine management at all -- it is running the stock injectors and engine management. I can run it on 50%-100% E85 if the weather is hot, but it gets cranky when temps drop down into the 70's or colder because I have no ability to richen the fuel properly for E85.

 

It does however provide a proof of concept for that setup. I broke a cam timing belt last week taking it to red line to out run a BMW that was closing on me fast, so will be going through the engine this summer and doing the full conversion when I can afford the parts I need.

 

 

Larry

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Back from the WUWT anti-ethanol thread wars, I see.  :)

 

Seem to have all your limbs, and most of your sanity, intact.

 

Good job over there.

 

I'm going to try to get you guys some good ammo for that stuff this summer. Next year I could have two identical cars except one runs ethanol with the compression engine, and the other runs gasoline, same cams, intakes, carbs, gears, transmissions, converters... everything except the static compression ratio and the temps they both run.

 

I think the black one can be the gas pig and the yellow one the ethanol beastie.

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Hotrod- my Saab is 2 is a 2L turbo as you describe but is rated at 210 on 90 AON gas. I cannot see the boost #'s as it is only a dummy gauge showing redline for boost w/o stated pressures. W/O the turbo it would be 100 hp less :o ? I do not think it runs much more than 5-6 # of boost on gas but that is only a guess- compression is at least 10:1 maybe higher (I was thinking 10.5:1)- I will have to look.

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Would the throttle plate rob the turbo ability to boost intake pressure in non wot conditions. This the position of a turbo web site selling those electric turbos that only operate for 10 seconds. They claim boost only useful during wot position as in other positions the throttle plate restricts airflow and positions the down stream airflow to vacuum. Is this is true? Now, would this be the reason diesel engines with not such throttle plate be ideal turbo application? Maybe this another reason Ford went with DI as the engine has dual turbo's and probably no throttle plate. Does the multi port injection have a throttle plate?

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Throttle plate pumping losses are one of the primary reasons diesels are more efficient than conventional spark ignition internal combustion engines. Diesels control engine speed by throttling fuel flow not air flow.

 

They always run with excess air, and only use enough fuel to provide the power needed. You can't do that with spark ignition gasoline engines because of low flammability limits of the fuel air mixture (could not light off really lean mixtures) and very high combustion temperature at some fuel air mixtures.

 

Those electric turbos are pretty much useless on most engines, it takes a lot of power to compress air in large volumes.

 

Most turbos are postioned in front of the throttle butterfly so the intake manifold goes into vacuum when the throttle is closed. This is absolutely necessary to allow you to control the engine, as the only way to control the power output of a gasoline engine is to reduce the intake air charge to the cylinder. At idle most engines have a manifold pressure or 18 inches of vacuum (29 inches being a perfect vacuum).

 

Electric turbos are really only useful for very brief increases in power (like passing) and on very small engines.

 

Back from the WUWT anti-ethanol thread wars, I see.  :)

 

Seem to have all your limbs, and most of your sanity, intact.

 

Good job over there.

 

Yeah it has been interesting but I have been noticing that over the last year the opposition has been very gradually getting less and less irrational. I saw the same sort of change in attitudes on E85 and water injection on some of the subaru forums a few years ago. It takes about 3-5 years to slowly change the prevailing belief about something like that among a large group.

 

Larry

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Ya, the electric turbos nothing like the hot exhaust turbo. Maybe a benefit if a low amp continuous minimal boost, like .1-.5 psi?

 

I bumped into the ADM study some years ago with a big trucks running E95 vs diesel fuels. Engine modified to run ethanol with changes to electronic control, compression increased from 18:1 to 23:1. Note: Scania E95 diesels run 28:1 compression. Glow plugs on the Detroit Diesel 2 stroke had to be left on for long periods to ignite the fuel during warm-up. These engines highly turbo and super charged. Particulate emissions mostly gone, CO slightly higher as Carbon emissions. Probably due to unburned fuel? Fuel tanks of truck same size, but the E95 trucks had half the range. Scania claims 65% to 70% more fuel use. Ouch. Number 2 diesel 139,000 vs ethanol 78,000 btu rated. One comment on report--  slow burn of ethanol and ignition of fuel unlike diesel. Ethanol DI ignited burns slow and misses the efficient extremely high chamber pressures of diesel burn.

 

So, my thought of the day----diesel ignition of ethanol a poor choice, spark plug ignition more efficient and controllable. May ethanol have a wider burn ratio range of mix since carrying oxygen? That would be good.  Diesel DI ignition works at all volumes of fuel spray as the liquid fuel spray mixes with air and ignites under proper conditions of mix, quickly. IOWs the fuel does not mix with all the air. Ethanol burns longer and decrease max pressures. IOWs the engine not designed to burn ethanol.

 

So, slow long stroke engines a natural for ethanol efficiency. This is the most efficient IC engine in general, but even more so with ethanol.

 

Large bore 2 stroke engine 52-53%

Heavy duty vehicle         44-43%

Auto                 40-41%

 

Large bores more efficient as the cu inch max per piston ring surface (radius squared). Also, high compression mechanical drag increases quickly with high compression ratios and robs engine overall efficiency. A trade off with increasing thermal efficiencies with higher compression. Some have it a losing battle past 11:1 compression. This may explain the Scania 28:1 engine using so much fuel? Sure the ethanol diesel runs better with such high compression but at lower overall efficiency. The dynamics of turbo charging do not apply as much for some reason? So, the logic of lower mechanical compression and high turbo pressures may a good one?

 

Diesel fueled 2 cycle  Detroit engines currently require efficiency robbing super charging as the exhaust turbo does not produce enough pressure to remove exhaust upon idle. Since ethanol carries oxygen this may not be the case with ethanol fuel. If the 2 cycle engine can utilize turbo only boost a BIG efficiency gain. 

 

Would the most efficient engine of ethanol be a two cycle large bore long stroke slow rpm 11:1 compression with max turbo pressure and spark ignition? Four exhaust valves engine.  If this is possible a 30% gain in ethanol mileage.

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I am not sure where the slower burn rate information comes from but when reviewing some of the SAE paper on optimized E85 or the E100 engines, the 90 percent burn rate is faster then gasoline.  The flame speed for ethanol has been demonstrated to be faster then gasoline or diesel and heat release charts can show this.  Even in one project, 100 proof, (50 percent ethanol and 50 percent water) achieve faster heat release then diesel.

 

Some engineering groups have demonstrated near 45 percent brake thermal efficiency and feel that this could have a slight increase with valve control for E85 to E100 fuels.  When you factor in urea and diesel after treatment, at today's prices, ethanol can compete against diesel with spark ignited engines.

 

Amerifuels in Nebraska have demonstrate with some 300 all ethanol engine in service last summer in irrigation, that higher efficiency ethanol engines can come close to equal volumetric use to gasoline.  Just waiting for the next generation engine with higher compression to pass gasoline.

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I got that understanding (and I'm not an expert, just posting to best of my understanding so in need of correction) from the Archer Daniels ethanol/diesel operation comparison study '95. They put on 300,000 miles/truck with half running normal diesel and half running E95. It may have been described as slower ignition speed of E95? Anyways ethanol described as missing max chamber pressure curve due to fuel characteristic. It's not a bad thing, just different from diesel and may be a reason they put 5% ignition enhancer in this E95 fuel? May this be the reason also for spark advance upon burning E85 in gas engines? No premature ignition with ethanol. A description:  "high latent heat of evaporation, which decreases the compressed gas temperature during the compression stroke. In addition to the effect of latent heat of evaporation, the difference of combustion products compared with gasoline further decreases combustion temperature, thereby reducing cooling heat loss." May this characteristic decrease max pressure? And cause problems for the diesel ignition?

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