Exhaust Temperature? L300 with TD

[AKcub]

Not sure why I even reached for it but I did...

After a 50km trip on the freeway with some cooldown time to get my egt temps below 400 I shut the Deli down and when I walked around the back I reached for the tailpipe. A lot hotter than I expected it to be. That got me curious about the rest of the exhaust. Sure enough, hot...

The tailpipe was definitely to hot too touch. Nothing crazy on the drive, I mean 100km/h with what seem like normal cruise egt temps. I have a few other diesels in my life (John Deere 450c Bulldozer, Dodge with 5.9 Cummins, lawn tractor) and with the exception of the bulldozer after a long day of really working it I don't remember the tailpipe getting this warm. Now I will be checking temps every time I get out of a diesel rig!

Anyone else noticed this? Is it normal?

Sorry, I am a little OCD.

Scott

[Growlerbearnz]

Completely normal, especially if you have the stock drinking-straw sized exhaust with all the tight bends. For some reason I used to burn myself every. damn. time. when disconnecting the trailer (before I switched to a side-exit exhaust).

Now that I think of it, it seems larger diameter exhausts never get quite as hot as smaller ones. They certainly rust a lot slower! I'm not sure why that is, but off the top of my head I'd suspect gas cooling as it expands into a larger pipe, more surface area to release the heat, and more chance of laminar flow with a boundary layer in a larger pipe.

[ChuckBlack]

I've completely replaced my exhaust system last year, its 2.5" throughout but instead of running to the back, it's blowing of the right hand side before the rear tire. Got some pep out of it as well as a mean looking look! Before I swapped and back flushed my cooling system from conventional 50/50 coolant my EGT ran at about 800F @ 105 Klm/h. I now run ELC and my EGT runs at about 655F @ 105 klm/h. I have also upgraded my radiator as well. During long hills i down shift to 2nd gear and make my way up around 3000 RPM allowing good coolant flow and at that point i run at about 1000F. I've never had it higher than 1200F. I've got it set up to alarm me when it goes any higher... Hope it helps!

[AKcub]

Thanks for both replies-

I was actually talking about the physical temp of the exhaust pipe. Seems odd that this little motor heats it up that much. Guess the smaller diameter pipe really chokes things off.

Next weeks project is to replace the exhaust. Trying to gather mail order pre fabbed mandrel bits to make up the new setup. The local shops (Seattle) with mandrel benders are booked out 3 weeks. Looks like I can get 75% of it via the interweb and have a local shop put it together.

Can't wait to see what affect the bigger pipe has on EGT's and pipe temps. Don't need to be starting any grass fires this summer!

Thanks,

Scott

[winelover]

I did the same as Mr. black, and mine ran cooler as well. It also exits before the rear tire. Chuck, did you replace the exhaust flange as well, or just cut it off, and replacement everything downstream from it? I did the latter, but have been thinking of getting a 2.5" flange and having it redone to everything is 2.5"

[FalcoColumbarius]

When I first got my wagon, she came with a stock pipe. I changed to a two point five inch stainless steel mandrel pipe. I didn't really notice any power difference and too be honest ~ engine temps appeared to remain the same, as well. She sounds way cooler, 'though.

I have a buddy that works mainly on VWs, Mercedes, Audi's, RRs, &c., he's a serious full time mechanic. I was having lunch with him one day and I told him that I had gone from stock to the bigger mandrel and he explained to me how it works, especially when it comes to turbo diesels. Every time the exhaust valve opens it lets out a specified amount of exhaust, which in turn travels through the pipe. The stock pipe is made to a certain diameter to best conduce the flow of exhaust from manifold to tail pipe. This in turn regulates the turbine, which dictates the compressor (of the turbocharger). If you can imagine a pipe with sausage shaped packages of exhaust gas travelling through it ~ this is what keeps the momentum of exhaust. By going with the bigger mandrel pipe, I have altered the performance of this process. My tail pipe is also very hot to touch after the engine has been working, especially hard. The engine works at a 21:1 compression ratio, that is a lot of heat. Heat is power until it reaches it's zenith, then that power turns on the engine ~ this is when heads crack &c..

I've been toying with the idea of embossing the tail pipe with two dragons then after driving up a long steep hill, getting out and branding my inner forearms, like in Kung Fu!

My mandrel pipe is full length and comes in two pieces: The one from the manifold is roughly twenty inches, then the rest is one piece. It was tricky getting it in.

Falco.

[pluckmyeyeout]

Hey Scott,

Where'd you order the pipe from? How'd it work out?