Hello all. Great site here, lots of good info.


So, I'm crew chief for the Ziptie Rally Team (http://www.ziptierally.com), We have a '97 K2500 with an L65 and 4L80 that we use as a service rig. The truck has served us well, and while we might be upgrading soon (need a true quad cab so we don't have to bring another vehicle to events) we'd like to take care of it.

Biggest thing, is it smokes.....a LOT. Our last major event was out in Pennsylvania, and one of my service crew members and I were following behind in a Forester, and most of the time our view looked like this:
http://www.sieglerphoto.com/Car-events/rally/STPR-2010/IMG8041/896008214_CQcfs-L.jpg

It's definitely smoking more than it did when we got it. But a year of hauling us to events (trailer, rally car, ~16 wheels/tires, and a few thousand pounds of spare parts/tools/food) has taken it's toll.


My buddy had a 1500 with the 6.5td (I'm assuming an L56), and it smoked quite a bit less when he removed the cat. But from what I've read, the L65 doesn't have one...but has a "soot trap" instead. What is the function of this thing? results of removal?

You probably dont have much if any boost from the turbo. Common problem - usually failed vacuum pump is the culprit. Other possibly causes are faulty wastegate solenoid, cracked vacuum lines, leaking exhaust crossover pipe or severe boost leak somewhere. Usually its the vacuum pump tho. The L65 is the HD 6.5 right? With the "F" vin code and no EGR? I cant keep the L56 and L65 straight. If what you have is the F engine with no EGR, then it almost certainly has to be no boost from the turbo. If you have the LD "S" engine with egr (i doubt it) then you could have an EGR problem.

I dont really see how the catalytic converter would REDUCE smoke (I dont believe the whole soot trap thing anyways... thats essentially what it is, but technically it is a catalytic converter). If anything it would increase the smoke. But either way you should gut it or remove it. It makes a noticeable difference in performance.

Remove the soot trap, turbo will breathe easier.

I agree with the list that Torque suggested. Check the vacuum system.
Better yet, if you want, make or buy a mechanical wastegate aka TurboMaster and see if that will solve your problem instead of replacing the vacuum pump.

Holy smokes(pun intended).

Definitely a boost issue. Either replace your vacuum pump(you need to save the pulley from the old one) or look into a turbomaster.

I bought my truck smoking like that. It had absolutely no go what-so-ever. Couldn't' get out of it's own way. After i replaced the vac pump and got the turbo working again, it was a night and day difference. I ditched the vac system shortly after and wen to the turbomaster once i had the PCM reflashed for more power.

Considering that your towing, the LEAST i would do to the truck.


ditch the soot trap and muffler(a little loud but not super loud)
fix the vac system or get/build a turbomaster
get at least boost and EGT gaugesAfter that you can do the reflash if your looking a a bit more power.

Best of luck

- Dave

I didn't ditch my muffler, i still have the stock muffler, and I didn't notice any difference in power from when I took off the exhaust and ran an open downpipe, to when I put the exhaust back on (with the converter gutted). So the muffler I think is negligible, you can take it or leave it. But definitely should get rid of or clean out the converter. Especially after running it with it smoking like that.

Wow, OK. Thanks for the ideas! yea, the L65 is the HD "F" version.

We weren't thinking it was down on power, just that we were reaching it's limit (really....we're hauling a lot of crap). But, the car owner/driver, who daily drives the truck, says it's been smoking a lot lately even empty.


Yea, my buddy's 6.5 made noticeably less smoke after cat removal. Our theory was that excess diesel wasn't being burned off in the exhaust (whole point of a cat)....and therefore less smoke. Could have also been less exhaust restriction = better turbo spool = more air = leaner mixture.....But I don't know much about diesels, so I'm just guessing :p: .