Diesel Exhaust Temps

[Craig P.]

While camping over the last several days at the Oasis RV Resort in Las Vegas, I overheard a couple of guys at the pool talking about how high diesel exhaust temperatures can ruin a turbo charger. One of the two said he installed an exhaust temp gauge, and when the temps get too high while pulling a grade, he backs off the throttle to allow the turbo to cool a little.

Both of the gentlemen pull 5th wheels with diesel pickups, but I'm wondering if this would be applicable to a DP

Craig

[Craig P.]

While camping over the last several days at the Oasis RV Resort in Las Vegas, I overheard a couple of guys at the pool talking about how high diesel exhaust temperatures can ruin a turbo charger. One of the two said he installed an exhaust temp gauge, and when the temps get too high while pulling a grade, he backs off the throttle to allow the turbo to cool a little.

Both of the gentlemen pull 5th wheels with diesel pickups, but I'm wondering if this would be applicable to a DP

Craig

[Route 66]

I've been to several diesel engine seminars at FMCA Conventions with reps from Cat, Cummins, and DD, and it's never come up.

They do say to keep the RPMs up by downshifting if necessary, but no other advice.

Our resident Cummins guy, Leo, may have some more info.

[RustyJC]

Chances are these folks had either a "box", bigger injectors or both if they had installed a pyrometer. With more fuel comes more horsepower and torque (my mild Cummins 5.9L HO ISB towing engine was factory rated 245/505 at the flywheel - it now dynos at 347/762 at the rear wheels), but at the expense of higher EGTs. My truck would hit 1300 degF pre-turbo EGT stock, but I've seen a momentary 1450 degF in modified configuration, and the ultimate EGT might even go higher.

That's why those of us with modified engines will monitor EGTs and (if we're smart or don't like walking) back off or downshift if the EGTs get excessive. I generally limit my truck's maximum pre-turbo EGT to 1250 degF or less when climbing steep grades, etc. by pulling my right foot out of the smoke pedal while monitoring the pyrometer.

Factory engines are calibrated to keep the owner out of trouble insofar as EGTs are concerned - that's why most don't come with pyrometers.

(Oh, and before my friend Leo chimes in, Cummins chooses to measure post-turbo EGTs when they do measure them.)

Rusty

[Happycarz]

I put a Banks system on my 99 ISC Cummins and when the Banks sees high exhaust temperature it automatically backs down the fuel. Part of the Banks kit includes a exhaust temperature sensor to monitor the EGT. On some systems, you have to watch the exhaust temp guage and back out of the throttle. That is what you probably overheard.

[sparetire]

I have a '94 diesel pusher with a Cummins 6CTA, 8.3 C.I.D. (mechanical injection) engine which was originally 250 HP and now it's tweaked to 400HP and 300 more lbs of torque (using a TST fuel plate and a different boost regulator. It is like night and day as far as power goes, it really scoots now, no more in the passing lane at 40 MPH with the flashers on on a steep grade. As Rusty said, there is a trade off with more exhaust heat if you don't spin the engine enough on a long grade. You can melt pistons quickly if you push it too far, I stay under 1100 degrees. I installed both boost and EGT gauges and monitor them. I have become used to where I need to downshift and when I need to watch the gauges and pretty much know what the readings will be. I only lost 1 MPG overall and, even at today's diesel prices, that extra HP and torque are worth every penny.

Happy travels,

Sparetire

[Craig P.]

Thanks for the input guys. Sounds like it's something that I don't need to worry about with my stock C7.

Craig

[SargeW]

With the newer common rail engines Cummins has introduced an oiler that sprays oil on the underside of the piston to help with the higher EGT's that it produces. One of the ways that the common rail makes higher HP and torque numbers it to rev it higher. This in itself creates higer temps in the combustion chamber.

The common rail engines supposedly will run at 1400 degrees all day. Can't say iv'e ever tested it though. Don't know how much heat those aluminum pistons would take before they melt.

Sarge