Sac vs. VCO injectors for WVO in 12v Cummins

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

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Sac vs. VCO injectors for WVO in 12v Cummins

Postby GreenHandle » Sun Nov 10, 2013 10:45 pm

I have a 1998 12v Cummins that I'd like to modify with a 2nd tank to run WVO. The previous owner installed Marine 370 injectors which use a 155 degree spray pattern. The hole size on the 370's is 5.012. The truck has upgraded intake and turbo so airflow supports the mild fuel increase and doesn't smoke much except for a haze at start up and when fueling heavily before boost pressure builds. Post turbo EGT's are always below 900F and usually about 500F at 2k rpm. I think the haze is mostly due to the incorrect spray angle which doesn't help fuel economy either (16 mpg hwy with 3.54 gears at 5,000 ft elev.). The correct spray angle for our piston bowls is 145 degrees. I would like to swap in new injectors with the proper spray angle but stick with a 5.012 nozzle orifice. Stock orifice size on this truck is 5x.01025 so we're only talking about an extra 50-75hp or so over stock, and I already have the air for that.

My question is whether sac or VCO (valve covered orifice) style nozzles would work better with WVO.

Both are available in 5x.012 with the 145 degree angle. They have different characteristics though as outlined here: ... kdown.html

The sac style nozzle seems more durable and runs a little hotter which could be good for WVO. VCO seems to burn cleaner and have more penetration into the air density, also sounds good to me. There are also several types of sac injectors, I'd be looking at the "micro blind" style.

Another option that has gained some popularity is a 7 hole (24v trucks use a 7 hole pattern) Denso sac injector with a 148 degree angle (I believe these were used on John Deere applications) and a .009 hole size. This fuels much like a 5x.012 but MAY have atomization advantages due to more, smaller holes. This has been questioned though.

Interesting discussion here: ... -hole.html

I know this may seem like more of a performance question, but I'm trying to understand how the fuel system from the injection pump to the injection event at the nozzle are affected by WVO vs. diesel and I haven't found much info on that for my application. Certainly volume and spray pattern as well as timing must play a role? Has anybody looked at the affect of a mild timing advance to say 16 degrees? Also wondering about which delivery valves would be optimal for WVO. Anyone with p7100 pump and WVO experience please share your thoughts or experience with tuning a p-pump for WVO and what style injectors are preferable.

2001 Dodge 2500 HO 24v Cummins 6spd ECLB 4x4
1998 Dodge 2500 12v Cummins 5spd ECSB 4x4
1993 Dodge D250 12v Cummins 5spd RCLB 2WD
1991.5 Dodge W250 12v Cummins 5 spd RCLB 4x4
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