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Old 05-05-2010, 07:10 AM
cgoodwin's Avatar
cgoodwin cgoodwin is offline
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Default Why are some engines better for VO than others?

There are two factors that make an engine a good engine for running VO. The sturdieness of the injection pump or unit injectors and the completeness of combustion achieved by the engine.

As an illustration of the first point, the Bosch VP44 injection pump used on the dodge/cummins trucks from 1998-2002 and most of the UPS and FedEx trucks of the same vintage was a terrible pump, it had a very high failure rate on diesel fuel suffering a myraid of problems from the weak stock lift pump starving it for fuel overheating and siezing it (codes P0216 or P1693) but by the time you get the code, the IP is damaged. P1284, P0370, P0216, P1688, P0602, P1691 all represent "Death Codes" for the VP44. I was the first person to suyccessfully convert a VP44 fitted vehicle by installing a high quality electric lift pump and a fuel pressure warning buzzer.

The Standadyne DB2 and DB4 IP's used on the Ford IDI, Chev 6.2 and 6.5 respectively also have issues, they need to see fuel pressure in the 8 - 12psi range at all times and have a factory life expectancy of only 70K, many people converting vehicles with 180K on the original IP blame VO when the IP fails in a month. Given adequate fuel pressure I have found them to be reliable pumps.

The Bosch inline pumps are by far the most robust pumps, they are cam driven and each delivery valve is a seperate cam driven piston pump, they can pump gravel and were used on all the Mercedes until 1987, the Cummins 1994-1998, The International DT466, most Perkins and quite a few other motors.

The HPCR systems (almost all are built by Bosch) lend them selves to VO as do many of the Unit injectors like those used by Detroit diesel although special care must be taken with the two stroke motors as they suffer from point two, completeness of combustion, at idle.

The issue with the Duramax engines is that they suffered so many injecotr failures that the warranty was extended to 200K rather than face a callback, the injectors stick filling the crankcase with diesel. Really bad issue on diesel, even worse on VO. Since the VO system would be blamed voiding the fuel system warranty, I elected not to supply a kit for the Duramax and suffer the bad PR from what is an inherant design fault.

Completeness of combustion: Engines that do not completely combust the fuel have high levels of soot, when burning VO this soot can collect as goo in the upper ring land where it turns to carbon, siezes the ring and destroys the cyclinder. Still other motors, like the Detroit two strokes, tend to bypass the rings with fuel when running for extended periods at low temps and load such as idle (now illegal in many states), on these engines special precautions must be taken not to allowing extended idle on VO, although most have been fitted with 10 minute kill devices that will sut the motor down after 10 minutes to avoid the $10K fine the EPA imposed on idling trucks.

The issue here is not only the upper ring land but the contamination of the lube oil with VO. Diesel oils are specifically designed to deal with fuel contamination as long as that fuel is diesel, mixing VO and lube oil in a hot pan with a crankshaft spinning through it tiurnes it to Mayonaise, nice as a sandwich spread, not so good as a lubricant.
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Last edited by cgoodwin; 05-08-2010 at 07:07 AM.
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