Pump Adjustment Theory

[adamdrives]

Hey guys, I know the basics have been covered but they don't seem to describe my situation. I also have a question about theory regarding the pump. The issue I'm having is that after turning down fuel to get less smoke at low rpm/high load, I'm getting grey/white smoke at full boost. Is this a sign of running lean? The greenbook calls the lda a fuel limiter, meant for reducing fuel at low charge pressure. So, I take from this that the d24ts have more fuel overall than the d24s, and the diaphragm is just to limit that at low charge pressure/high load. This seems to be contrary to much of the information on the net. I don't fully understand the description of the operation of the device on the pump, but it is called a fuel limiter, not a fuel enrichment device.

So, the question becomes, to achieve max power/least smoke at low rpm:

Start by tuning main fuel to get max power with least smoke at full throttle, then bring back LDA to limit smoke at low rpm

or

Start by turning main fuel as low as possible to get least smoke at low rpm/full load, then turn in LDA to get more fuel at full boost.

Trying to wrap my head around this.

[anders]

I will try to explain it.
The LDA is a fuel limiter, it actually limits the travel of the tension lever in the pump. When you supply the LDA with boost the control cone is pushed down via the pressure placed on the diaphragm, as this is pushed down the guild pin slides inward changing the point in which the tension lever stops.

The best method to adjust these pumps is to adjust the smoke screw on the LDA all the way out to remove any preload, then disconnect the boost reference line to the LDA and drive the car around at low rpm full load to adjust the smoke via the max fuel screw.

If you can't eliminate the smoke there is something else going on, maybe bad injectors, timing not advanced enough, worn out engine, one cylinder severely low on compression, bad valve guides and seals, ect..

[adamdrives]

I will try to explain it.
The LDA is a fuel limiter, it actually limits the travel of the tension lever in the pump. When you supply the LDA with boost the control cone is pushed down via the pressure placed on the diaphragm, as this is pushed down the guild pin slides inward changing the point in which the tension lever stops.

The best method to adjust these pumps is to adjust the smoke screw on the LDA all the way out to remove any preload, then disconnect the boost reference line to the LDA and drive the car around at low rpm full load to adjust the smoke via the max fuel screw.

If you can't eliminate the smoke there is something else going on, maybe bad injectors, timing not advanced enough, worn out engine, one cylinder severely low on compression, bad valve guides and seals, ect..

Thank you for the recommendation, I will try that. When adjusted properly, should the car not make any/very little smoke at low rpm high load? For instance, lugging along in 4th at 2k or so, putting pedal down, I will get smoke. Is that simply inevitable? I've noticed I tend to try to stay in higher revs (2.5-3k), because if I need to change speeds in high gear it's difficult to do without making a hazy cloud, which I don't like. Getting started in 1st and 2nd gear also seems so leave some smoke.

I would like to have my injectors reconditioned in the future to set a baseline. I have no record of them being replaced or serviced. I have a spare set which would make that process easier.

[anders]

With a healthy engine, good injectors and properly adjusted pump there won't be any smoke. I don't leave my engines at stock settings but I also like to try to get mine not to smoke when off boost.

What is your timing set at?
You should pop test your injectors. ( I will pop test them for free if you want, just pay for the shipping)
Compression test?
Valve clearances?

[adamdrives]

With a healthy engine, good injectors and properly adjusted pump there won't be any smoke. I don't leave my engines at stock settings but I also like to try to get mine not to smoke when off boost.

What is your timing set at?
You should pop test your injectors. ( I will pop test them for free if you want, just pay for the shipping)
Compression test?
Valve clearances?

I haven't been able to test compression yet, but my valves are all within .02mm, and timing is set at .90. That is very generous of you, I appreciate it. Maybe send me a message and let me know where I should send them. Thank you!

I am also running 20lbs of boost, so that might make tuning for no smoke more difficult, right? Logically it seems to me that the pump would have to have dynamic fuel delivery to supply appropriate fuel at low and high boost, which is where I thought the LDA comes into play.

[R.Mojica]

sounds like its time to get those GTD nozzles.

[adamdrives]

After following anders directions the car is way less smoky (still smokes a little, hill start in 1st or winding up second will leave a decent cloud) and doesn't feel down on power. Got 28 mpg my last highway trip over 150 miles going 70-75 the whole time in 65 deg weather. Not sure why people recommend adjusting that limiter downwards for performance, all it does is add smoke. Has anyone here tried the governor mod? Shimming the springs or adding a stiffer spring? I would still like more power down low. Contrary to what everyone says about diesels and their low end torque, this car feels most powerful on the highway from 4k onwards.

[ngoma]

Has anyone here tried the governor mod?
See this post Governor mod (http://d24t.com/showthread.php?p=11475#post11475). A Simple search brought that up. ;)

[adamdrives]

Thanks, I believe I have read that one, it's just very short and I was hoping to get more than one impression.

[anders]

After following anders directions the car is way less smoky (still smokes a little, hill start in 1st or winding up second will leave a decent cloud) and doesn't feel down on power. Got 28 mpg my last highway trip over 150 miles going 70-75 the whole time in 65 deg weather. Not sure why people recommend adjusting that limiter downwards for performance, all it does is add smoke. Has anyone here tried the governor mod? Shimming the springs or adding a stiffer spring? I would still like more power down low. Contrary to what everyone says about diesels and their low end torque, this car feels most powerful on the highway from 4k onwards.

That's good news, sounds like there might be some more things to take care of if your still getting smoke upon hard acceleration. A slight haze is fine and helps the turbo spool up faster. I have done the governor mod, it was a nice easy mod that helped raise the power band. These engines do produce there power up top, it's the way it was designed, to have similar chartaristics as a gas engine. You can't get much power below 2000 rpm, I think peak torque is at 2800 rpm on these. The NA intake seems to help with the lower end.

[woodfordhalse]

Hi
Sorry to hijack your thread but after adjusting the smoke screw with the lda unscrewed completely am i correct in assuming you then screw the lda back in for less smoke , as much power as possible ratio...

Cheers

[anders]

The adjustment screw on top of the LDA adjusts the pre-boost fueling. Threading the screw in provides more off boost fueling (smoke) threading it out provides less off boost fueling (less smoke).

[adamdrives]

That's good news, sounds like there might be some more things to take care of if your still getting smoke upon hard acceleration. A slight haze is fine and helps the turbo spool up faster. I have done the governor mod, it was a nice easy mod that helped raise the power band. These engines do produce there power up top, it's the way it was designed, to have similar chartaristics as a gas engine. You can't get much power below 2000 rpm, I think peak torque is at 2800 rpm on these. The NA intake seems to help with the lower end.

If I pin it in first without easing on the throttle for first few moments, I'll leave a pretty healthy cloud, but that seems to be the worst of it. I believe I backed off on the LDA as much as possible but I will re-investigate. Going more than a third throttle or so in 2nd and 3rd below 2k (especially when cold) will also leave some light grey haze behind me. My eventual goal is to have it be smoke free, but I'm satisfied by the improvement for now. First gear smoke is annoying as I live in a hilly area and getting moving from a light inevitably leaves some haze behind me. Ideally I would like to be able to drive it without having to compromise power for smoke in some situations.

[adamdrives]

I fixed the throttle so now I am hitting the fast idle screw at full throttle, not the stop on throttle spool, that seems to have helped pick up a bit. Definitely a good thing to check. My throttle cable is still about half an inch too long, I can't get all the slack out of it. I guess they stretch over time. I was able to back out the LDA more but that hasn't affected smoke, I guess it was at it's practical limit already.

I believe peak torque is 2500, that probably changes with a non-stock turbo. I am curious to learn more about this governor mod, but am intimidated by taking my pump apart. On a scale of difficulty how would you rate it? Do you follow any guide or do you know what to do from experience.

[ngoma]

My eventual goal is to have it be smoke free...
Hey it's a diesel from the mid -80's, the design originated in the mid -70's. It's always going to emit some smoke. Not billowing black clouds, but some smoke now and then is part of the package.

[adamdrives]

True, I guess I should revise that statement to read as smoke free as possible, which may be where I have it now. Once I get my injectors tested and installed we'll see if that makes any difference.