Semi trucks on SVO?

[stillsearching]

One thing i'm aware from reading elsewhere is that indirect injection engines are usually more suited to running straight vegetable oil than direct injection engines are, due to viscosity issues which become more important on for instance common rail modern diesels running 25k-30kpsi pressures. Heating the SVO makes it flow easier but i'd still question whether it would run on absolutely anything well.

I'm seeking opinions from anyone who might know about older semi truck engines - since they were direct injection before most others - about their potential suitability for SVO, whether anyone has ever heard of others running SVO, and similar. My guess is that the Detroit Diesel -53, -71,-92 type engines/the 2 strokes with their unit injectors would probably be the most resilent (I HAVE heard of SVO being run on them without issue) however they are not the most efficient - i'm curious whether anything newer might be able to run it without trouble.

[cRiPpLe_rOoStEr]

You might remember IDI is often pointed as more suitable to SVO/WVO, but I've already seen many non-electronic direct-injection engines running on SVO, including big rigs. The most suitable engines are either Scania or Mercedes-Benz (some of those engines can be found in America in Freightliner trucks, a few ones are/were made in Brazil only for export), but it can also work with Cummins 6CT engines and Caterpillars.

[stillsearching]

Why are they more suitable though? What is different about them, very robust injector pumps?

I'm trying to figure out which engines are more or less suited to true SVO (not just biodiesel) use, assuming heated fuel, preferably from people who have actually done and tried and run them for many miles without destroying their engine. So far I can't find a single incidence of a class 8 truck running it anyways...

I'm more interested in older engines than newer, any project I do would have to be on an older truck for economic reasons. (plus i'd never risk a new six figure rig on SVO without evidence of others doing a hundred thousand plus miles on it without trouble - since that's about what a replacement engine would otherwise cost just to break even : P)

[cRiPpLe_rOoStEr]

Originally Posted by stillsearching

Why are they more suitable though? What is different about them, very robust injector pumps?

IDIs are more suitable to SVO because of their higher temperatures and lower injection pressures which are quoted to allow a more complete combustion of the oils. And their injection hardware being cheaper to manufacture and repair while still more reliable is also an advantage

[oil pan 4]

As far as I can tell you don't want to run high concentrations of SVO in anything with a CP3 or new style very high pressure common rail injection system.

[niky]

Direct injection is not the problem so much as high pressure direct injection, due to the finer nozzles on the piezo injectors and the high pressure pumps.

[RustyLugNut]

found in current diesel engines do not work safely with VO (vegetable oil ) because of the reasons listed out by Oil Pan, Rooster and niky.

The low pressure inline pumps found in Pre 1996 Mercedes diesels, Dodge Cummins VP7100 equipped 5.9L and old Cummins 855's easily survive a failure of your VO heating system. I have seen some abusive installations on these engines ( poor or no heating of the VO and insufficient filtration ) and yet the pump survives with no apparent damage. I have seen VE pumps and late model high pressure pumps fail mechanically within seconds with VO. The above listed engines are not the only ones that can run on VO successfully, they are just the ones I have had experience with. A low pressure (2000 psi) inline pump seems to be a necessity to cover for failure modes in running your VO.

As Rooster pointed out, indirect injection is an advantage. More complete combustion can occur within the pre-chamber which helps minimize the problem with VO in direct injection applications - the clogging of rings and lands with polymerized VO which could come about for a myriad of reasons.

Our 1996 Dodge Cummins and a 1996 Van equipped with the Mercedes 606 diesel both have had episodes of ring gumming when running on VO even with proper VO filtration and heating. The variability in our used oil sources is the likely culprit. Constant water/methanol injection has eliminated the problem but the volume of fluid used on a long range over-the-road tractor/trailer could be problematical.

The ideal tractor/trailer would have a low pressure inline pump and indirect injection. I do not have a broad enough experience base to have seen one. Maybe someone else can point you towards a likely solution.

[cRiPpLe_rOoStEr]

Finding an EPA-certified IDI for a big rig might be a challenge...

[RustyLugNut]

Originally Posted by cRiPpLe_rOoStEr

Finding an EPA-certified IDI for a big rig might be a challenge...

The last IDI Class 8 tractor I came across was a 60 year old custom glider in someones personal collection. It was even listed as a "classic car" at the DMV.
The engine had come out of a combine which was even older.

[cRiPpLe_rOoStEr]

Detroit Diesel almost monopolized the over-the-road heavy-duty Diesel market for a while in America...