Official Milspec Timing Figures

[britannic]

FYI: I finally got the military's timing figures:

6.2L: 4* BTDC @ 1300rpm upto 1989 inclusive
6.2L: 5* BTDC @ 1300rpm 1990 onward
6.5L: 5* BTDC @ 1300rpm

[ 12-09-2003, 05:38 PM: Message edited by: britannic ]

[mhagie]

That would mean that The Diesel depot settings of 10* at idle falling off to 5* at 1100 is not far off?.
Merle

[britannic]

The Diesel Depot timing is probably matched to IP, if they supplied it. A rule of thumb is to rev the engine in steps of 500rpm and check the timing at each increase. It needs to be very close to TDC after 2000rpm, of course this doesn't check the heavy load timing, only the light load advance.

Timing is set for a particular IP to optimize it's timing advance curve. The milspec IP can run on JP-8, Kerosene and #2, so the timing advance is set up to handle that.

The real test is to dyno the engine and assess the timing under load.

[britannic]

Here are the results of experimenting with my timing:

Setting it to the milspec 4* BTDC @ 1300rpm, increased smoke, the shift points increased by about 500rpm and there was less power, boost and torque.

I found that 2.6* BTDC @ 1300rpm, gives hardly any smoke, plenty of torque and power with a slightly quieter engine.

My friend drove the truck last night and told me that it runs like a strong 454 and only the diesel clatter let him know it wasn't actually a gasser :D !

YMMV, but in my case, because the forced aspiration increases combustion speed, it's necessary to slightly retard the timing as compared to a N/A engine.

Interestingly, Animal reported, that Cummins DI tuners retard the timing a little after increasing fuel and boost to prevent damage to the pistons and harvest extra power.

[Dieselboy]

Great info Brittanic! I'm looking forward to getting a quantitative timing figure with my newly-won MT480, and your post will be a great starting point. Now I've got to track down the Snap-On guy and get the right probe!

[britannic]

FYI: with the dual idler timing gears, 2.6 BTDC @ 1300rpm is set with the timing marks perfectly aligned on my engine.

[dieselcrawler]

Originally posted by britannic:

Timing is set for a particular IP to optimize it's timing advance curve. The milspec IP can run on JP-8, Kerosene and #2, so the timing advance is set up to handle that.

[/QB]If I were to have my IP rebuilt, and it is a stock CUCV IP, is it a better IP to rebuild than the domestic version? What do you mean, JP-8? What type of fuel is this? Can this IP be set to 4911 spec's with out problems, and handle a Banks turbo in the future? Any info on this would be great, I want to know if I should look for a temp pump to use while I have this one rebuilt, if need be. Thanks,
Greg

[britannic]

Originally posted by DieselCrawler:
</font><blockquote>quote:</font><hr />Originally posted by britannic:

Timing is set for a particular IP to optimize it's timing advance curve. The milspec IP can run on JP-8, Kerosene and #2, so the timing advance is set up to handle that.

If I were to have my IP rebuilt, and it is a stock CUCV IP, is it a better IP to rebuild than the domestic version? What do you mean, JP-8? What type of fuel is this? Can this IP be set to 4911 spec's with out problems, and handle a Banks turbo in the future? Any info on this would be great, I want to know if I should look for a temp pump to use while I have this one rebuilt, if need be. Thanks,
Greg [/QB]</font>[/QUOTE]JP-8 is jet fuel and it has slightly less BTU's than #2. Since it has even less lubricity than #2, the military IP was fitted with hardened parts. Rebuilders can install the hardened parts, but will charge around $150.00 or more to do so.

I had my milspec IP rebuilt by Tim Wagner @ www.accuratediesel.com (http://www.accuratediesel.com) and he was able to calibrate it's hydraulic head to 4911 specs. He had to use a later model housing though, since they were strengthened to handle the higher 6.5LTD injection pressures. He also installed the 4911 servo and face cam to match the timing specs.

I have 6.5LTD injectors, along with the the 4911 calibrated IP and customized Banks turbo kit. This setup did run quite well with the original Banks T04B turbo, but I wanted better take off and faster spool up, so I installed an MHI TE06H turbo from a Banks Ford 7.3 kit - see my sig. for more details.

For even more power, I installed the dual idler gears. Next up is a Chausson intercooler from a Renault diesel, which has a 3" inlet and 3" outlet. It's going to be a challenge to install, but according to my research should match the turbo's CFM pretty well.