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E85 Question

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When E85 is injected into the intake port, how does it affect the pressure and temperature profile of the intake manifold?

That is, when injected, some or all of the E85 vaporizes causing significant cooling. Presumably, for some portion of the time that is against a closed intake valve with no flow. Later, it is against a flow swept immediately into the cylinder.

The chilled air would presumably be denser. do the pressures equalize before the air is ingested or is the ingested air colder but at a lower temperature? Since the chilled air is within the intake runner and the port, does any of the chilling effect of the ethanol affect the IAT in the manifold?

Wouldn't port injected water/methanol pictures have the same effect? But what is the effect???

I've found one paper, a Bachelor's thesis, that looked like it had that instrumentation...temperature and pressure sensors in an intake port just before the head...but didn't report those temps and pressures.Effects of Different Fuels on a Turbocharged, Direct Injection, Spark Ignition Engine https://dspace.mit.edu/bitstream/handle/1721.1/59952/676953430-MIT.pdf

There may be some SAE papers, but I don't have access. Some may find this presentation interesting; things like combustion chamber photos (while the fuel is combusting). Ethanol Optimized Engine: [url=https://www.ars.usda.gov/ARSUserFiles/np213/Teleseminars/Robert]https://www.ars.usda.gov/ARSUserFiles/np213/Teleseminars/Robert Stein (AVL) 3-29-11.pdf




The forum software won't let me get the second link right.

Attached Files

On a sequential multiport injected engine, the E85 will cool the air at the intake port making it more dense. However we are talking about an effect that occurs over a very short period of time, on the order of milliseconds, that can't be detected without crank angle based temperature measurement. The same can be said with intake plenum temperatures. That cooling effect needs to basically make cooler air flow backwards into the plenum. There is also a thing called thermal inertia, meaning that it takes time to heat up and cool something down, which doesn't help cool down the manifold.

Your definition of port injected methanol/water is going to affect it. Is it a continuous flow system like an old Bosch K Jetronic? Or is it sequential port injected, like a staged injection system upstream of the port?

You also have to keep in mind the chemical effect of E85. It vaporizes poorly when cold, and leaves a larger pool of fuel in the intake port. Flex fuel algorithms use different wall wetting compensation (called X-Tau on some systems) to account for the different sized puddle.

As for the paper you attached, it is sort of a pitch to Ford based on preliminary results of what they called the Bobcat program. That program was to run a heavy duty truck fuelled by E85 and normal E0/E10 fuel. It was cancelled. The whole thing depended on government subsidies for E85 and fuel economy credits for flex fuel, which the US has since cut. The technical conclusions are interesting though, but it tells us what we already know: E85 reduces knock. Charge cooling is better when sprayed into the cylinder vs the port.

There was a later paper by an MIT researcher that calculated the impact of direct injecting E85 vs port injecting it. See attached. E85 direct injection is like E50 port injection.

Attached Files

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