pre turbo or post turbo

[NIsaacs]

Pre turbo works, post turbo works. Any pyro is a win win situation. However you install one, it is good stuff. Having driven, bombed and rebuilt Cummins engines for 30 plus years, with NEVER having a failure caused by high exhaust temps, with either style, I doubt post turbo is a concern. Millions of trucks are running post turbo pyros, no problem.



The 500 degree temp difference on a hill, with a load, under acceleration means very little. The post turbo pyro will keep up within seconds with no engine damage. The Cummins will stand short bursts of hight temps, as all the drag racers and sled pullers prove daily.



Usually a hole burned in a piston means a bad injector or faulty piston cooling. High exhaust temps will expand the piston to the point of contact with the cylinder liner causing instant damage. This damage will show at the piston edges. From small scuff marks to piston seizer as the result.





"NICK"

 

[RustyJC]

The 500 degree temp difference on a hill, with a load, under acceleration means very little. The post turbo pyro will keep up within seconds with no engine damage. The Cummins will stand short bursts of hight temps, as all the drag racers and sled pullers prove daily.

You're missing the point entirely. If I tow a heavy 5th wheel up a 5 mile 6% hill while running a continuous 1000 degF post-turbo, I could well be running 1500-1600 degF pre-turbo. We're not talking a few seconds here, but 5 minutes or more. If you feel comfortable running that hot for that long, it's your money and your choice. I limit pre-turbo EGTs to 1350-1400 instantaneous while accelerating up to speed, 1300 for moderate periods (10-20 seconds) and 1200 for long pulls, but I'm a conservative individual who would prefer not to walk home. Absolutely stock, my truck would hit 1300 degF pre-turbo peak while towing. YMMV.



Rusty

 

[NIsaacs]

Before piston cooling, the industry average max temp, pre turbo was 1200 degrees, post 900 degrees. After piston cooling, pre 1300 degrees, post 1000 degrees. This was set by the truck makers, by the engine makers and by the pyro makers!! This 300 degree difference works. You friends little test was no doubt under acceleration. On a 5 mile uphill grade, steady pull, there will NOT be a 500 degree difference, that is my point! Unless you friends post turbo pyro is down stream in BFE somewhere. Post turbo works, millions of trucks prove this every day.





"NICK"

 

[RustyJC]

Before piston cooling, the industry average max temp, pre turbo was 1200 degrees, post 900 degrees. After piston cooling, pre 1300 degrees, post 1000 degrees. This was set by the truck makers, by the engine makers and by the pyro makers!! This 300 degree difference works. You friends little test was no doubt under acceleration. On a 5 mile uphill grade, steady pull, there will NOT be a 500 degree difference, that is my point! Unless you friends post turbo pyro is down stream in BFE somewhere. Post turbo works, millions of trucks prove this every day.

Yes, there was a continuous 500 degree difference on a similarly modified truck. You can choose to believe this or not. As boost levels increase, turbine drive pressure increases and the temperature gradient across the turbine side of the turbocharger increases as well - the laws of thermodynamics say this must happen as more energy is being extracted from the exhaust stream.



The point I've been trying to make all along is that post-turbo readings may be fine for a stock engine. The manufacturer can run engines on dynos and correlate pre-turbo and post-turbo temperatures at stock fueling and boost levels and make statements such as 900 degF post-turbo equals 1200 degF pre-turbo, but that's only true at stock fueling and boost levels. When I put on the EZ and the DD2 injectors, my fueling level went up and my boost went from 21 PSIG to 34 PSIG - therefore, the 300 degF differential no longer holds true.



IF I were towing a 5th wheel with a stock truck and Cummins said that 900 degF post-turbo was the limiting EGT, I could certainly live with that scenario. With increased fueling and boost, however, I can be running a substantially higher pre-turbo EGT and still show a 900 degF post-turbo EGT, so the validity of a 900 degF post-turbo limit as a safe operating temperature may no longer apply.



Towing heavy with stock trucks is one thing - towing heavy with BOMBed trucks (even moderately BOMBed ones such as mine) is a different matter.



Rusty

 

[NIsaacs]

What you are saying, is good info and I can agree with most of it. What I can't agree with, is, bombed trucks can't use post turbo pyros. We (truckers) have been bombing these dang trucks for years, (way before Dodge Cummins Diesels and TDR) with post turbo pyros, they work.



In 1989 Dodge used the 160 hp/400 trq. engine. I say a post turbo pyro at 1000 degrees is good. Now Dodge uses the 325 hp/610 trq. engine. I still say a post turbo pyro at 1000 degrees is good. Is that not a major bomb? Basicly the same 5. 9 engine is still in use.





"NICK"

 

[RustyJC]

We've beaten this horse to death. Having participated in engine design, testing and failure analysis for over 32 years, I feel strongly about my position. You feel just as strongly about yours. Let's leave it at that and agree to disagree.



Rusty

 

[NIsaacs]

Like I said in my original post "It works for me" Thanks... . I think





"NICK"