Gary Emerald

CNG... they're great for our application, but I certainly wouldn't spend any extra money putting one in my truck!

logskidder

Off-road application?

Gary Emerald

natural gas wells

logskidder

Use them to run a compressor?

Gary Emerald

yes sir

logskidder

Why a Cummins and not something like a BB Chevy......our compressor uses 2 502 Chevy engines, I can get most parts local......same as a 454

Gary Emerald

these are single engine packages... the 8.3 Cummins is the smallest unit in our fleet (though we are no longer buying them because they go through cylinder heads and turbos like popcorn)

we usually use CAT & Waukesha, and we've got some AJAX's also. We've got a pretty good parts support infrastructure, so parts are usually on-hand or only a couple/few hours away

logskidder

When you say cyl head, do you mean valve wear? Do you use watercooled turbos?

Gary Emerald

they burn valves and turbos... just replaced another turbo that had maybe 2700hrs on it. the turbos are watercooled. (HX40's... YUCK!) Cummins says we're running them too rich, but we've got them set at 6.2% exhaust O2 per their spec. I've been setting the valves a little looser than Cummins spec to try to give them a little more time on the seat to hopefully cool them a little better.

logskidder

Do you add anything to the gas to lube the valves?? What do you mean 6.2%

Gary Emerald

6.2% O2 concentration in the exhaust stream

not really feasable to add anything to lube the valves... don't even know how you'd go about that.

logskidder

You would need to install a different fuel filter head if you want to add some type of lube for the valves, Im sure you know how dry cng is and without some type of lube the valves beat themselves to death....its not just a cummins. Im non sure what type of electronics you have C Gas? will it go into closed loop at 167*? Do you have any way of reading your air/fuel compensation and your air/fuel deviation? Can you read your gas mass flow deviation at load??

Gary Emerald

man, try getting a fuel gas analysis from these people... these little units just use an Alltronic mag or coil box. static timing. and just a regular old carburetor... no computer controlled A:F

all of our other emiessions units have computer controlled A:F, but even our non-emissions Cats and Waukeshas don't eat up valves and turbos the way these Cummins do.

I just replaced a head on a 3306 that had just shy of 18,000hrs on it. Compression was good, head looked great when it came off, but it was past due for a 2yr cyl head job.

logskidder

[QUOTE=Gary Emerald;2126528]man, try getting a fuel gas analysis from these people... these little units just use an Alltronic mag or coil box. static timing. and just a regular old carburetor... no computer controlled A:F

I feel you pain!!

Gary Emerald

it's especially annoying when you've got one of these fragile units with no electronic A/F tracking and they've got 8 different well heads feeding into it! who knows what kind of fuel gas BTU you're getting!