EGT's and heads?

[85-m1028]

why does the 6.5 have higher max and sustained EGT rating than the 6.2??

[john8662]

What numbers are you looking at for your data? Could you post what you're seeing?

Typically in a Turbo situation, the 6.2 can take less heat that the 6.5 can for one reason that I can think of, the 6.2 pistons have no coating on them for heat reflection. The 6.5TD pistons come coated from the factory to deal with the increased pressure and heat associated with the turbo.

[JeepSJ]

Changes were made to the cooling system in the 6.5, which allows it to move more water through the heads, which in turn allows the engine to handle the higher sustained EGTs.

[85-m1028]

could you use 6.5 heads and cooling upgrades etc. to raise the sustained EGT??

[NH2112]

I believe the main difference between 6.2l and 6.5l heads that allow for higher sustained EGT are sodium-filled valves to help keep them from melting. Injector angle differences probably play some role too. So using 6.5l heads and 6.5l cooling upgrades will help, but unless you have your 6.2l pistons coated they won't be able to handle any more heat and will be the weak spot in the system.

[britannic]

The 506 block had oil sprayed pistons, here's a thread from the 6.5L forum on this topic: Oil Sprayed Pistons (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004550#000007)

[john8662]

A couple more things to ponder here about the "6.5"

The 6.5 was introduced in 92 and had single thermostat cooling and approx 85GPM water pump, so it wasn't any better cooling wise than the 6.2.

In 97 the 6.5 got the previously mentioned piston oil spray coolers and high volume oil pump and 130GPM water pump coupled with Dual thermostats.

The main point I want to make is that the 6.5 wasn't much different from the 6.2 when it was first introduced, I still think the difference in sustained heat EGT with a turbo is due to the coated pistons. Both the 6.5 and the 6.2 have the .0005" #7-8 cylinder clearance for heat too.

The accepted temperature rating for the 6.2 with a turbo has been: 1100*F PRE-Turbo

6.5 is the typical 1250*F MAX PRE-Turbo pyrometer installation.

[85-m1028]

is there a part # for this high volume oil pump?? I can't seem to find it anywhere, there seem to be a lot variables that affect EGT sustainability. I read 900` for the 6.2 and 950 for the 6.5, here http://www.4wheelpartsadventures.com/archive/2004/08-august/0103-tech-finesse-2.asp

[arveetek]

Originally posted by 85-m1028:
I read 900` for the 6.2 and 950 for the 6.5, I'm not sure where he's getting his information, but I don't see why you would have two different figures, a max. and a sustained. To me, max. EGT's means the max. EGT's you can run without doing damage to the engine. So you should be able to pull all day at the max. EGT's. I know I've seen over 1400 degrees on my engine before without it melting down.

Some of his other info on that site isn't quite correct, as well. He says that the bottom end of the 6.5L is stronger than the 6.2L. This is false. There were no improvements made to the 6.5L, other than piston oil spraying, which actually weakened the block. The 6.2L and 6.5L use the same rods, crank, main caps, etc. In fact, the later model piston oiler blocks actually have smaller main bearing outer bolts. I believe that 6.2L is actually stronger than the 6.5L.

I personally believe that the 6.2L and 6.5L are the same blocks, and that the 6.5L is just a bored-out 6.2L. That's why the 6.5L has a higher failure rate (block cracking) than the 6.2L. But that's just my opinion. I'm waiting for proof either way.

Casey

[john8662]

the 900 and the 950 just sounds like post turbo EGT measurements.

I agree with Casey in that the Max EGT is a number that as long as you stay under or at this reading, then you're still safe, but go over, and see melted stuff.

[dieseldummy]

I think part of the difference between the 6.2 and 6.5, aside from the anodized piston crowns, is being turbo charged. When a turbo is added to the combination there is a better scavenging effect in the cylinder. The valve overlap is the same, but now instead of having to draw air into the cylinder it is being forced in. During this brief period of valve overlap some of the hot exhaust gas is pushed out quicker leaving less time for it to "heat soak" into the piston crowns. Just my theory...

Justin