Engine Timing

[surfbeetle]

Are there different timing specs for California versus non-California vehicles? If there are, what should they be? I have a '97 Suburban that was originally from Texas. According to the printout from the chevy dealer, is a HO (which I assume is High Output). The dealer here in California just replaced the injection pump and now the car doesn't have the punch and power that it used to. The last pump had been replaced just before I got it, but by a dealer in Texas. Also, what types of tools are needed to be able to set the timing?

[charliepeterson]

The timing specs are the same in all the states. California and Massachusetts have the strictest Emission laws in the country.
The only special tool you need to adjust the timing is a fancy scanner called a Tech II. This scanner is specific to GM only and a GM dealer is the only one who can keep the scanner updated to all the latest vehicles. Anyone can buy one of these for about $2,500.00.
When the dealers adjust the timing on these trucks they are generally conservative with the settings. Most of the members here, myself included are more aggressive. There is more to it than just cranking up the timing numbers.
I would guess that the difference with the old Injection Pump and the new one towards performance issues is the timing settings.

[surfbeetle]

Charlie,
Even before I had the injector pump changed, the dealer had retarded the timing with the old pump and that seemed to lower the power. With the new pump, (same mechanic) it had the same lower amount of power. Do you know what the actual spec should be? What is the difference in a HO 6.5 diesel and a regular 6.5 diesel? Is it the timing or is there more to it than that. With the HO Dodge diesels, there are differences like oil sprayed pistons, advanced timing, different transmissions, to name a few. I am getting a new exhaust system and remote fsd cooler with the better resister. My wife wants this thing to be fast, if not faster than it was before.
thanks for any info.

[charliepeterson]

The dealer will set the timing to -.25 to -.50 TDC. We did some testing a few years ago as to fuel mileage, cold starting and performance. The numbers we came up with are more aggressive but if not watched can be detrimental to engine life.
The numbers were -1.94 to -1.50 TDC. If I remember correctly these come out to about 8 to 12 degrees of actual timing.
The TDC numbers are when the fuel is injected before or after the piston comes up to top dead center.When you inject the fuel earlier the fuel management gets better but the other side of the coin is the exhaust can get hotter from more fuel being used before it gets sent back to the tank. This is where the after market guages are a must. An exhaust pyrometer is the most critical.
Getting back to the testing. We found that the cold starts were better as well as fuel mileage, better fuel management. I do my driving by what the pyrometer says.
Of course now you can get into the computer programming and crank up the fuel rate,transmission shift points, governed RPM then boost pressure. Open up the exhaust system and hold on to your hat. These engines do have a limit but they really aren't your father's diesel either.

[surfbeetle]

Thanks for all of the information. Being that this is my wife's car, I don't think that having her drive by the pyrometer would happen. I will have to stay on the safer side of things, bigger exhaust and a computer, but nothing that will get the exhaust temp that high. I actually wish that my suburban had as much power as my father's diesels, he has a Dodge Cummins with a Banks exhaust, turbo and intercooler on it, his other diesel is a Freightliner with a Detroit.

[patrick m.]

add a charge air cooler, increase boost, and dont worry about EGTs.
I have found: with a "chip", the more boost= less EGT (of course i have a charge air cooler).
get the exhaust, have the TDC offset corrected, install the intercooler, then add boost and fuel.
as long as your wife is not pulling a 5k to 10k lb trailer, EGT will be fine. :D

[ucdavis]

Charlie-
When I did my timing on a borrowed Vetronix 'MasterTech' scanner (same manufacturer & software as the Tech2) it automatically set the offset at -1.25. I don't know whether this is a standard that has changed to a more favorable number, but I didn't do anything to adjust it from the .25-.5 range, just followed the Vetronix software instructions (version 2002). Maybe GM (Vetronix does its software development in conjunction w/GM) is gravitating toward the better timing for drivability?
Surf-
Most important thing on these rigs IMO is attention to cooling system maintenance. Easiest mistake is to look @ outside of AC condensor & inside of radiator, find both clean & not look between the two. More overheating failures seem to come from that little oversight than any other. This hidden space needs at least bi-annual inspection/cleaning if not annual. Next would likely be radiator clogging; this is practically unknown w/Dexcool or other 'permanent' antifreze in proper proportions. W/attention to cooling maint. & w/your wife not towing you should have good service from this rig.

[charliepeterson]

ucdavis:

That's interesting about a possible lock out on the TDC numbers with your program. That setting is better than the stock one though.
Is this program on a laptop or a hand held scanner?