[Diy_efi] LPG injection

Don Sauman donsauman at cythera.net
Thu Nov 28 04:42:43 GMT 2002


Greg

In this part of the discussion you are talking about Methanol. Does that
information also apply to ethanol?

Thanks
Don

Greg Hermann wrote:

> At 1:33 AM 11/25/02, Altaffer, Eric EM2 wrote:
> >>In some ways. It's for SURE why methanol fueled engines tend to foul the
> >>plugs before they are warmed up!!  It also is REALLY bad for the efficiency
> >>and hurts the power output when some of the heat of combustion goes into
> >>evaporating the rest of the fuel !
> >>You're getting right AT the reason why some of the mfgr's have played with
> >>that 80/20 ethanol/gasoline mix. At stoich, the latent heat of vaporization
> >>of that mix is just about PERFECT for having the last of the fuel get
> >>evaporated JUST as the spark plug ignites it.
> >>It seems like methanol would be very good at
> >>surpressing det if this were the case.
> >>This very much IS the case, and methanol IS excellent at avoiding
> >detonation.
> >
> >There is a bog problem with adding methanol to gasoline.  The o2 sensors
> >that are on the cars are trying to maintain a stioch mixture for gasoline.
>
> Nope. The O2 sensor is EXACTLY that. It senses stoich mixture, regardless
> of what fuel or fuel mixture brew you are running.
>
> >When you add the meth, the car is a bit lean at 14.7.  This is BAD for
> >detonation suppression.  I live in California where they have introduced 10%
> >meth into the gasoline and I could not get the darn thing to stop detonating
> >even at low boost.  Luckily they do not add meth to the 100 octane.  That is
> >all I run.
> >
> >>Not to mention that injecting SOME of the methanol pre-turbo (under boost
> >>conditions only) would put some internal coolant into the
> >>compressor--reducing the work needed to do the compression, thus ultimately
> >>reducing backpressure on the motor from the turbine, and possibly
> >>eliminating the need for an IC.
> >>Greg
> >
> >Can you explain that one a little more in-depth.  I would never inject a
> >liquid into the turbo.  Nitrous no problem, but a liquid, never.  I would be
> >worried about the blades destructing not only from thermal shock, but the
> >mechanical shock.  Also the alcohol is taking place of air in the
> >compression cycle.  Since liquid is nearly incompressible, I would think it
> >takes away from compressing the air.  I would however inject the alky after
> >the intercooler, or the turbo for those not running an intercooler.  Just my
> >thoughts.  ERIC.
>
> A SMALL amount of atomzed liqud doen't really have much of a negative
> effect of the compressor blades.
> All I am talking about is enough methanol so that its latent heat is
> sufficient to transform the compression process from (near) adiabatic to
> (near) isothermal.
>
> Greg
> >
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