Written by Michael Patton Sunday, 15 March 2009 09:27

Diesel Timing

Maybe you have seen the closed circuit gas pump film clips on reality TV? The vehicle at the gasoline pump suddenly bursts into flames while the owner is refueling. Usually the driver starts pumping gas and then goes back into the car to get something. After sliding across the seat, creating a static buildup within his body, he touches the pump handle again with enough stored static spark energy to light the volatile air/fuel mixture at the filler neck. POOF. Then the understandably panicked operator instinctively, but mistakenly, pulls the nozzle out of the filler neck, spewing fuel all over the vehicle and the ground: he has just re-invented the garden hose flame thrower.

If you have started enough camp fires, you may appreciate how dangerous gasoline is. Yet, with a touch of humility, I tell you that the little lady was not impressed with my Boy Scout skills when I nearly burned down the new backyard shade structure after using the gasoline shortcut in the portable fire pit beneath it. The flames leapt out of the pit for 12 feet or so while I stood at the ready: rum and coke in one hand, garden hose in the other. The lesson here? If you need a water hose in your hand, it may be possible that you haven’t quite thought this through. I suspect that some variation of this statement may end up on my tombstone or as part of the narrative for a posthumous Darwin Award.

Introspection aside, have you noticed that not even one of those fiery film clips ever involve a diesel pump? Never diesel, always gasoline. Why is that simple observation important to tuning a diesel motor? And how can you improve your fuel economy with this knowledge? There are answers.

Diesel does not ignite easily compared to other fuels, not at temperatures at which we are comfortable breathing anyway. This is a key to the fuel’s success in high power applications that also benefit from an additional margin of safety. Perhaps if someone had suggested this to me sooner, I might still have a backyard shade structure.

I Want More

In service-department-originated field complaints. Customer A gets 24 MPG, while Customer B is upset with his 11-MPG results. Among the factors that create the disparity: driving style, trip length, weather, vehicle condition, elevation, fuel energy value… the list is long. Tuning is one of the factors that we can control; to our benefit as we shall see.

LLY Duramax Diesel EFI Live Lope Tune

In a perfect world, diesel timing would be constantly varied according to cylinder pressure feedback and a fancy computer algorithm. That technology is being used today in some developments. Diesel injection timing scheduling is only as good as the hardware accuracy used to measure and control it. It is suspected that this may account for a plus-or-minus five degree discrepancy in desired versus actual timing, as commanded by the PCM (ECU). Without fancy cylinder pressure transducers, we are left to determine this experimentally (guess): trial-and-error custom dynamometer tuning is the usual method. This can often be the answer to improved performance and efficiency and it is well worth the expense. What if I told you that it is possible to reap a 30 percent increase in economy, just with tuning? What if I told you that my 8,000-pound 2500HD Duramax gets 24 MPG on the highway… every day? And what if I also said, you can have it too?

In this article...

The Spark is Gone
Injection and Ignition
Ignition Versus Injection Timing
Piston Geometry
Fuel Quality
Diesel Timing Damage
Environmental Factors

Set as favorite

Bookmark

Email this

Trackback(0) TrackBack URI for this entry

Comments (1) add comment

Subscribe to this comment's feed

bgordon61 said:

Excessive timing advance
Michael,

Thanks for a very informative article!

After reading your article several times, I am convinced that my LLY Duramax may have excessive timing advance due to a "loud" engine rattle during heavy acceleration. But, I am running a "stock" tune!

Is it possible that a stock GM tune could include excessive timing advance?

How can I verify the timing advance parameters on my LLY engine?

Thanks,

Bill