timing???

[PToombs]

If it's like that, it's a good idea to mark the pump before you move it. Then you know how far you have turned it. Or how far to set it back.

[aspoonhour]

Well? Did you do it?

Just go got back from a quick test run. I bumped the timing about 3/16". I was doin' some measuring on my other 2 trucks(no marks on the '91's pump) and noticed that it appeared that the '91's pump was a smidge retarded. I measured from the AFC housing(Lip where the smoke screw cap is) straight over the the head. It looked to be about 1/16"-1/8 retarded. That's why I went 3/16". It was very difficult to do at all. That lower pump hold down nut had me for a bit...Ended up using and old 1/2" distributor wrench. It was about the toughest part of the whole thing. I also loosened some of the injector lines holders, but didn't loosen the lines at the pump(don't have a wrench to get them all).

After I was done, the idle speed seems to be up a little and it actually sounds like the other too. Runs real nice. Seems a bit smoother and seems to have some more power!!! I'll need to get out to the hwy tomorrow.

Strangely, enough, it also got rid of what I was thinking might have been a bad/clogged injector that sounded a lot like a knock in the engine.

Thanks for the tips!!! See anything that concerns anyone?

Andrew

[Ezra]

Anybody got a picture of the s-shaped wrench? I bought a cheapo just for the accasion.

[1991cummins]

i have been postponing getting to the advancement because i cant get to it either ... maybe i have been a little lazy too

[Ezra]

Well I got said cheapo wrench and am just going to heat it up bend it.

[aspoonhour]

I used a distributor wrench. Just lucky that it worked. I don't know what said wrench looks like...

Andrew

[Okie Smokie]

You can get the "S" shaped wrench from Snap-On, but it'll cost you about $65.

[fourwheelininajeep]

For those of you gasser guys this will help you understand the full swing of the pump is a 12 degree advance from fully retarded to fully advanced that is a large improvement over stock just like a gas engine the sooner you get timing in the more complete burn. Now you can go farther than that if you pull the front cover to the timing gears take the injection pump gear off and advance it a tooth. I dont recomend it unless you plan on racing or want crazy power without reliability but I thought I would throw that out there for every tooth is about 10 degrees with 3 being the most you can do before loosing from to much advance. At 3 teeth advanced and full turn on the pump its 32 degrees of advance which is enough to do some serious power if you can get the fuel and get the turbo to light. This will drastically change your driving characterictics, retarded will make it sluggish at top end but lots down low. More advanced will make it good down low but crazy up top so advancing much more than 12 degrees you need to upgrade the governer spring, probably valve springs and make sure the engine is up to it.

[fourwheelininajeep]

I think I got my previous thread backwards, retarded will give you nothing down low, and advanced will give you good down low but not as much on the top. Correct me if Im wrong

[Richie O]

Think you had it right the first time. BUT thats comming from a guy that has his pump timing stock.

[jltait]

According to the dodge ram forum: "Advancing the timing will...

Decrease exhaust temperature
Increase cylinder temperatures/pressures
Increase fuel economy (yes, economy is better)
Increase your output of NOx (a pollutant)
Decrease your output of Hydrocarbons (a pollutant)
Increase the amount of black smoke at peak torque

Raising the cylinder temperatures/pressures after already having increased the fueling (as the TST kit does) pushes the engine that much closer to its design limits, but lowering the exhaust temperature helps balance against the increased heat load from the increased fueling."

To add to this: I believe advancing the timing will cause a slight drop in top end power on a turbo cummins. This I believe is caused by the boost loss. since the cylinder temperatures/pressures increase by advancing the timing, and exhaust temperatures decrease reducing turbo boost...IF it were a 6.2 diesel naturally aspirated (which I have more experiece with) advancing timing would improve power overall. If one of the moderators gives me the go ahead to post the link to the dodg ram sight which has the above information I will post it. Being a newbie I did not want to step out of bounds!! They have lots of other timing information in there as well.

Now a question: on the engine information plate, in the timing box lists "TDC 1.25mm" If i remember correctly. Does this mean the amount of fuel which has been injected at TDC in volume . Can someone help me understand that one? Also what does this all mean in *'s BTDC or ABDC?

[sdstriper]

1.25mm is a specified amount of plunger lift that the injection pump is set to. That particular spec. is generally for the later 1st Gen trucks. The pumps plunger lift can be bench set or set on the truck IIRC. Then you can also advanced or retard the timing from there by rotating the injection pump one way or the other. And for the advanced level enthusiast, you can advance the timing marks on the geartrain as well.

[MUDDY]

According to the dodge ram forum: "Advancing the timing will...

Decrease exhaust temperature
Increase cylinder temperatures/pressures
Increase fuel economy (yes, economy is better)
Increase your output of NOx (a pollutant)
Decrease your output of Hydrocarbons (a pollutant)
Increase the amount of black smoke at peak torque

Raising the cylinder temperatures/pressures after already having increased the fueling (as the TST kit does) pushes the engine that much closer to its design limits, but lowering the exhaust temperature helps balance against the increased heat load from the increased fueling."

To add to this: I believe advancing the timing will cause a slight drop in top end power on a turbo cummins. This I believe is caused by the boost loss. since the cylinder temperatures/pressures increase by advancing the timing, and exhaust temperatures decrease reducing turbo boost...IF it were a 6.2 diesel naturally aspirated (which I have more experiece with) advancing timing would improve power overall. If one of the moderators gives me the go ahead to post the link to the dodg ram sight which has the above information I will post it. Being a newbie I did not want to step out of bounds!! They have lots of other timing information in there as well.

Now a question: on the engine information plate, in the timing box lists "TDC 1.25mm" If i remember correctly. Does this mean the amount of fuel which has been injected at TDC in volume . Can someone help me understand that one? Also what does this all mean in *'s BTDC or ABDC?

feel free to post the link

[sdstriper]

FWIW. The manual states that; One mm of rotation past the timing mark will advance or retard the pump timing by one degree.

And they are referring to the letter timing marks on the geartrain...

[jltait]

Good info! So If a dynamic timing probe were installed does the 1.25 mm plunger lift equate to a specific dynamic timing of X*'s BTDC or ATDC. I know cetane rating of the fuel and other dynamics will affect this, but I am asking in general. I know with the 6.2 diesels an illumination probe is inserted into the glow plug whole and will detect ignition to give a dynamic timing value. They like 5-8*'s BTDC(Before top dead center). I want to understand Cummins timing the best I can.

Here is the link: http://dodgeram.org/tech/dsl/FAQ/timing.htm

Sounds like 15*'s BTDC is the sweetspot for cummins? If I am doing the KDP update should I mod my timing at the gear to get optimal or just do KDP and twist the pump?