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      11-11-2012, 06:11 PM   #28

Drives: 2011 335d
Join Date: Aug 2012
Location: MidWest

iTrader: (0)

Originally Posted by hotrod182 View Post
You are running 70% water? Is there any advantage/harm in trying 100% methanol?

Also, my car is due for the EGR recall, programming update. Any feedback on whether this increases/decreases HP? I know half the owners have complained about mpg decreases.

I was looking at the new mixer diffuser they install during the recall, doesn't that thing look restrictive? Has anyone tried running without it?
Thanks for the pic of the diffuser.

The EGR recall impacted the initial tank mpg's, but the car seemed to adapt rapidly and fuel efficiency returned to normal after that.

Do not have any quantifiable data on before/after power #'s.

Been running just over 50% H2O lately in the d and my Cummins powered Wrangler.

Good question on straight methanol. I've attached a link to an excellent thesis on alcohol injection in diesel engines that also summarizes a lot of previous research. Some areas related to your question that make me think going above ~100 proof (50% alcohol/50% water) is a bad idea is the issue with the peak cylinder pressures and rate of pressure rise (effectively advancing timing). Plus above ~50% alcohol the combination is flammable. And if one is using the OEM washer fluid container as the source of liquid . . .

Some interesting highlights below:

"Baranescu [19] performed alcohol fumigation experiments on a six-cylinder, turbocharged, direct-injection, 7.1-L diesel engine. The alcohols used were methanol, 190-, and 160-proof ethanol. Her results reported that alcohol fumigation caused a substantial increase in maximum in-cylinder rates of pressure rise and peak in-cylinder pressures when compared to regular diesel operation. She concluded that this should be a limiting factor to be taken into account when alcohol fumigation is to be used.

"The following results were obtained when fumigating lower ethanol proofs: The maximum rate of in-cylinder pressure rise was reduced (up to 20%) when compared to absolute (200-proof) ethanol; similarly, the peak in-cylinder pressure levels were reduced; NOx emissions were reduced below diesel levels with low-proof ethanol (proof below 150)"

"They concluded that, in general, it is possible for the NOx emissions to be substantially reduced by alcohol fumigation. This reduction in NOx is more pronounced with lower ethanol proofs, as the increased amounts of water help decrease the peak combustion temperatures."

"The vaporization of ethanol tends to cause a pronounced
charge cooling which lowers the in-cylinder temperatures prior to ignition, thus increasing the ignition delay. A long ignition delay may result in a large amount of ethanol being introduced into the cylinder before ignition occurs. Under such conditions, the combustion of a large mass of fuel results in very rapid burning rates with high rates of in-cylinder pressure rise and high in-cylinder peak pressures. Under extreme conditions, the combustion proceeds so rapidly that an audible knocking sound can be discerned the so-called diesel knock . Under low engine loads, however, the ignition delay caused by the ethanol can become so large that the combustion occurs
very late in the expansion stroke. This results in the quenching of the combustion process, resulting in low peak pressures and temperatures, incomplete combustion, reduced power output, low thermal efficiency, and increased HC and CO emissions (see below). Engine knocking (at high loads) and mis re (at low loads) are usually the factors that limit the maximum amount of ethanol that can be fumigated into a diesel engine. The water contained in lower-proof alcohols appears to inhibit pre-combustion reactions that cause engine knocking."