swany

I have mounted my pyro about 3" behind the turbo, in the exhaust,how much is too much temperature? I've heard different things about temp, but I did'nt want to drill my manifold. Right now (not towing) about 700*. thanks

rbrettctd

Cummins specs say 9-950 (cant remember which). So 7 should be safe. Your best bet is to go ahead and drill the manifold though. Its a lot more accurate IMO.

swany

OK, what would be the temp. difference between the two places?

steven

I always find this subject interesting. Cummins says 950* post turbo. So, why isnt that accurate? It is. I go with cummins specs. They tell everything this is where we need to be and where to measure it. But can anyone show me a Cummins spec that says manifold EGT should be kept within this limit. I honestly have never read any Cummins spec that says that. It seems to me that someone, somewhere said this is acceptable at the manifold. And I believe it is safe, but too be technical, it was reverse engineering to decide what the manifold EGT should be. You would have to take the cummins spec and then add to that number to get the acceptable manifold temps, not the other way around. So go with what cummins says, it is the most accurate and acceptable to cummins.
V/R
steve

swany

Steve, thanks, that sounds about right to me, Post turbo.

Cowboy_Customs

1/2 the way down this page http://dodgeram.org/tech/dsl/Facts/93specs.html
950 post turbo, 1250 pre turbo.

haloman

Cummins Specs are for non-modded engines. When you go changing timing/fueling parameters, pre-turbo is the best option.

steven

Totally incorrect. Cummins specs are engine/compenent acceptable heat tolerances. Heat doesnt know if it is pre or post turbo and neither does the probe. Cummins specs are acceptable limits regardless of engine configuration. This is why big rigs all have their probes post turbo, not pre-turbo. I am not saying that you dont get a more accurate reading of the current temp at preturbo. You do. But you get that with risks that according to Cummins specifications, are unnecessary. They tell you to put the probe post turbo and they tell you the limit. Which is conservative of course. If you stay within that limit, regardless of how much you have done to your motor, you can expect the parts to all withstand the heat according to the engineers design. If you exceed that limit, stock or tricked out, you can expect there are certain compenents that will fail prematurely. That may mean within 100k miles or 10k miles, but premature for its original design. In fact, making the claim that you should move the probe if you turn up the motor, you should also consider that when you turn up the motor, you should not expect the motor to last as long as it was originally designed. Doesnt mean it wont, but when you apply more heat to a certain design, that heat accelerates the wear and tear of that part. i.e., if a part is designed to go 300k miles at 1000* post turbo, which for all intent and purpose, that's what we are talking about, if you run that part at 1200* you should expect a loss of life expentancy in the range of 20-25%. you can mitigate those risks with the use of other components, such as straight thru exhaust and high flow filters, or synthetic fluids, but mitigate is not the same as eliminate. The point being, that post turbo specs are heat specifications for all components of that engine. If you turn up your engine, you still MUST stay within those or reasonable limits or the parts will eventually fail. Simply moving the probe to the manifold does not increase the life expectancy of the motor or any of its parts. You might have an exception on race tracks where you might, during a 1/4 mile, want faster response of the pyro. But even then, people run max heat for that 1/4 mile anyway and say, as long as it is short bursts, like a 1/4 mile, its okay to do, so why do you need the pyro then anyway???? I dont know, maybe someone else does.

V/R
steve

haloman

I never said moving the pryo would make parts last longer. The pryo pre-turbo is more accurate (quicker). People have shown 300-500 degreee difference between pre and post. I think we can agree that a pryo is better than no pryo, but it has been shown over and over that a pre-turbo pryo will give more accurate egt readings.

SChandler

The problem with post-turbo pyro probes is that the amount of temp drop across the turbo varies. From the Cummins specs, they are allowing for 300* across the turbo (1250 pre-turbo, 950 post-turbo). That 300* is not constant, or guaranteed. Others who have probes in both spots, have reported on long pulls 400-500* differences between pre- and post-turbo temps. So, you are okay at 950 post-turbo, but are at 1350 pre-turbo which is into the imminent danger zone. I mount my probes pre-turbo because I don't want to guess at what factor I should use to be safe.

steven

But it seems like you are guess what is safe when you are having to make the calculation or rely on someone to tell you preturbo is 1350 or whatever. I am saying that if you stay within Cummins specs you are not in ANY danger zone. You and others are correct. You will have a more responsive guage preturbo. It will move faster and farther than preturbo. But if you read 1250 or 1350 more quick, but tell me quick and short bursts of even hotter EGTs are safe, then why do I need to worry if I run my EGTs at or below 950, which is almost always the case pulling a 35' wanderer 5th wheel. I have been to 1050 before, but that is not excessive, even by cummins specs and only once have i done that and felt worried about it. But do you think i would be less worried if i ran the probe preturbo? It would be just a different number that climbs faster, but the same overall acceptable range. One range is 1250 to 1350 one is 900-1000, it only depends on which one you choose.

Regarding the differences between pre and post turbo, you are right, there are differences. Dont you think that cummins engineers knew there were differences when they designed and specified their tolerances. It doesnt matter if you pyro reads 500* hotter pre turbo. if you look at the post turbo, and it says 950, you are okay. If you are running so agressive that you could blow it anyway, then you dont need your guages in the first place, because there going to lie regardless. Lastly, you still have to acknowledge that running a probe pre turbo comes with some certain level of risk, both in installation and in operation, whether you like it or not, it is greater risk than postturbo. So i do away with the risk, go post turbo, sleep better at night, and run my motor according to cummins specs with the mods i have. Just my thought.

Thanks,
V/R
STeve

Ace

Forgive me for pointing out the obvious, but I believe the only thing that really matters is the temperature in the cylinder when the piston starts to melt. No matter where you measure it any further downstream or what numbers you use or what equipment setup you're running, at the end of the day it's a guide (not a hard-and-fast rule) you have to uniquely calibrate in your estimation to help you avoid a meltdown.

So until somebody figures out how to get a pyro probe in the combustion chamber, I guess we'll just have to keep on arguing about this!

MikeThomas

I say: Just mount the probe where you want, run her as hard as you can until you melt a piston, rebuild, and use that temp and a guide. Seems MUCH quicker than arguing .

The Tank

They will take alot of heat, I have ran 1500+ for a 1/4 mile, you will smell the oil getting hot way before the pistons melt.

SChandler

This is almost as bad as arguing politics. Which is why I don't argue politics. Nobody's completely right and the truth lies somewhere in the middle. As has been mentioned before, do what makes you feel good. If pre-turbo works for you, then use it. If you're afraid of a probe destroying your turbo (assuming the turbo didn't fail first from the extreme temps needed to melt a probe), then go with post. I sleep better at night knowing I'm getting a more realistic picture of what's happening in the cylinders (note I did NOT say completely accurate). Either way, it's still just an estimate of the average temp of all six cylinders.