Re: Diesel/Ethanol hybrid thought - modifying an old VW Rabbit

From: Stephen Sprunk (stephen_at_sprunk.org)
Date: 03/24/05 

Date: Thu, 24 Mar 2005 11:30:20 -0600

"George Jetson" <none@hotmail.com> wrote in message
news:tud341p0lutqm2l2th9d4flh8fld0mbn49@4ax.com...
> I was thinking of converting it to Diesel/Ethanol hybrid.
> The car has no value so if it explodes, who cares.
...
> The plan is to run on diesel when idling and starting. Then when power
> is increased, start the ethanol injection and run on as much ethanol
> as the engine will allow.
> So no changes to the diesel injection system, with the possible
> exception of changing the foot pedal to diesel ratio to adjust for the
> extra ethanol fuel injection. IE change the length of the metering
> pump throttle arm.

Both of those steps are unnecessary.

> I don't want to add any ignition system; I want to use the diesel to
> do the ignition.
>
> What I don't have clue about is:
>
> How much ethanol/Diesel ratio will it operate on?

A standard diesel engine will operate (including startup) on a mix of 95%
ethanol and 5% diesel. However, you may need to replace hoses, fittings,
and the fuel tank with corrosion-resistant versions if you want the vehicle
to last; alcohol is very corrosive.

Also, if your vehicle has an oxygen sensor, expect a lot of false alarms.
Ethanol is oxygenated, so it will fool a sensor that doesn't account for it.

> How would the water/Ethanol ratio affect the system?
> IE 190 proof or 160 proof.

I don't know what proof the ethanol sold commercially is; I had assumed
190pf or higher.

> If I lower the compression ratio from 22.5:1 to a lower
> number, would this allow higher ethanol/Diesel ratio's ?

No, it actually makes it worse. Diesel needs a high compression ratio to
ignite, and the less diesel you have the higher it has to be. Ethanol does
not ignite under compression; you need the diesel ignition to ignite the
ethanol.

> If so, I still need to keep it high enough to run it on pure
> Diesel. So what would be the low-end for diesel to still run ?

5% diesel and whatever compression ratio your engine already runs at.

S 

-- 
Stephen Sprunk        "Stupid people surround themselves with smart
CCIE #3723           people.  Smart people surround themselves with
K5SSS         smart people who disagree with them."  --Aaron Sorkin

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