I, like others, am on the constant search to get my engine operating as efficiently as possible. I've got a recently rebuilt pump and new BB injectors, so the next step is getting the timing dialed in.

The pump was installed and timed by ear (not by me), and I later verified it to be about 2.5 ATDC via a Rotunda lumi meter. It actually seemed to run pretty well, but my MPG still seemed less than optimal. Based upon the factory timing chart that FORDF250HDXLT supplied, I decided that I was probably a bit too advanced and should retard it for safety's sake.

In a nutshell, the chart says that your timing should be between 4-6ATDC at sea level and 5-7ATDC above 3000' depending upon the fuel cetane level with the higher cetane requiring a more advanced luminosity reading.

Conflicting with the above chart is the posted information I keep coming across folks quoting dieseldon's recommendation of 0.5-1.5 ATDC.

A few months ago I bumped my timing back landing at about 7.2 ATDC just going on the assumption that my cetane level was probably closer to the worse case scenario and in the 40-42 range. Fast forward to a little more recent research that shows fuel in Oregon has a minimum cetane of 47 by law. Now, no matter how you look at it I am definitely running retarded by at least 2 degrees.

I hate to beat a dead horse here, as I know a lot of this has been discussed before and believe me I've spend a lot of time reviewing old threads! Just curious if anyone has any new / recent information to share regarding timing with a lumi probe or possibly timing via pulse method and then checking with a lumi probe to see when the fuel is actually lighting?

At this point I feel like I should be shooting for 4-5 degrees ATDC. As much fun as getting to the IP in a van is, I'm hoping to not be doing this for a while after this next go-around!

 

I'm interested too!

There is a boatload of discussion out there about pulse timing with some good consensus of where it should be. However, very little agreement about where lumy timing should be. I've spent hours looking into it, and didn't really get anywhere besides the chart and a few peoples disagreeing observations. I'd really love to see a comparison between the two methods!

Honestly, I'd think luminosity timing should be more accurate, as its when the fuel is actually lighting. I mean they time gas engines when the spark fires, so thats about the same right? or maybe not... hmmm Either way, I'd really love to see a comparison between the two, especially dealing with the ULSD we're running now, not the old stuff the tables were based on.

It would really help those of us that have picked up lumy meters for cheap, and future reference.

 

yeah it really is unfortunate that there is so much conflicting info when it comes to timing via luminosity.those who claim the low numerical ATDC settings when asked,have but one answer; it's not based on anything,just personal experience.
i strongly advise against that.go by those who designed the engine.the odds are they know best.

when timing via this method,it's done so at 1400 rpm with a warm engine,using the glow plug location at #1 or #4 and this chart:


you know,either method though it seems people like the advance side of things as much as they like turning up that fuel screw.they think if a little is good of each,then surely more of both are better.just doesn't work that way with engine tuning.these engine don't like to tow as easy with more advance timing.when you turn 'em back just a bit they pull a lot easier i think and an added bonus,it's not so noisy.
i really enjoyed timing via the old school meters using the lumy probes.it just had a real high cool factor to it lol.my engine ran great at the 6 ATDC.now with more fuel (intercooler and maxxed oem ip) i run 7 BTDC via pulse @ 2k rpm.

you know though what may have been a lot of reason for people thinking 1-2 ATDC via lumy worked best,might be because a lot of these old meters and probes are just no longer any good guys.they're pretty aged lol.best to move on and go with the ferret adapter (or used pulse meters.) when my snap on meter's magnetic pickup started going,i could tell the meter couldn't be trusted any longer so that's why i went to the ferret and timing light w/advance to get the job done.

 

Thanks for posting that chart in this thread, F250. You've been a wealth of knowledge on the subject thus far and I appreciate your time to share your experiences.

 

I would say, honestly, that you should adjust it and see what runs best for you. Use the given points as a starting point, and then adjust it a little, see what gives you more power/better mileage.