normal pyrometer readings?

[fsmyth]

Hello. New to IDI here.
What are normal exhaust temps on one of these?
I just added a pyrometer (digital) to my truck ('91 F350, bone stock, AFAIK).
Temps look like shat I am use to seeing on big trucks, until you nail it.
I managed to get it to 1150 @ 60 MPH very easily, and 1250 by firewalling ot there. Normal?
I am more use to seeing ~950 on a loaded (40.000+) Mack, 800-900 on N14 Cummins. and
700-800 on my 98 24V 5.9 2500 a approximately the same load. All these are turboed, tho.
Also having to adjust a bit to the speed of the 200 mS thermocouple shipped with the
digital guage - not used to seeing the numbers change that fast
TIA

 

[gandalf]

Good morning, and welcome to the forum. You will find many knowledgeable and helpful people here. We're a friendly bunch.

EGTs have been pretty thoroughly covered here. I'll give you my recollection, and let the next guy agree or correct me. The pistons in our engines are aluminum. The melting point of aluminum is 1221°F. You can take the EGTs a bit above that, very briefly. You do that knowing the possible consequences. The rule of thumb is to limit the EGTs to 1150°F, and even there only for a short time.

Something to keep in mind is the location of the probe. The exhaust gases will cool as they travel through the system. The ideal measuring point is as close to the piston as possible. You're measuring temperature at one point, when in fact the danger is further upstream. The probe in my system is in the downpipe just below the exhaust manifold flange. Some members have even drilled and tapped the manifold in order to get the probe closer for a better reading.

Hope that helps. I'm sure you'll get more input soon.

 

[argve]

Yep these IDI's just run a little higher numbers compared to the other engines. Now as for what is the top number to avoid - well some debate, there the thing that you will hear is 1050 is a safe max (all day long pull) and you can peak up to 1200ish but don't hang out there.

My theory is this. The pistons are cooled by cooling jets underneath that are squirting oil on the back side of the piston to carry heat away (if they are working then you are golden). Also the pistons aren't 100% alum so the melting point is much higher. I would run my cummins up to I don't know what because the 1500 degree Pyro couldn't read that high but I would not hang out there for more than a minute or two and when I had the head off the pistons showed no signs of damage. So for me I don't have a pyro and if I had one it would only to give me something to look at and go Gee **** look at that while I kept on trucking. My theory is not for the faint of heart nor the timid. So if you choose to run like I do it's your own choice. But the other thing was I was looking at the air temp not the piston temp which would be different because yes the gasses leaving the chamber are that temp but it takes time for the piston to absorb that heat to meet the gas temp. again my theory is not for the faint of heart.

 

[hesutton]

N/A these IDI's will make some pretty high EGT's without too much effort. I don't know if your truck is N/A, but I'm guessing that it is. The numbers posted above are good advice on sustained maximums. A turbo will drop those EGT's when hauling. That addition of an intercooler will help even more. Before turbo'ing the F350 crew cab, I had to watch the pyro like a hawk. Not so much anymore.


Heath

 

[icanfixall]

Welcome tothe forum. As posted above your temps are telling me they are kind of high but usually the non turbo idi will run hotter than a turbo idi engine. When you have a turbo it forces in more air and that air cools the engine better but only to a point. Boosting above 15 lbs increases the inlet air temp above 300 degrees so you making a hot engine even hotter. So far I feel you don't have a turbo because of your original posting. Can you tell us if the injection pump has been turned up on the fuel or is this how you bought the truck. Some info on who or how the engine was taken care of by the other owner helps. Its generally felt that the injecters and injection pump last around 125,000 miles. Some run longer and some run shorter. It all depends on how the fuel system has been taken care of. Many here will run a fuel additive to lube the injection system because the new fuels are so dry. Some just add a quart of transmission oil to a tank of fuel and other run a additive in every tank of fuel. I add Stanadyne Proformance Formula at 4 oz to every tank full. It has worked well for me. Another note is when Ford installed the turbo on the late 93 1/2 year engines they didn't add any gauges like pyro or boost. That kind of tells us they felt the engines could handle the heat but for many here its like driving blind. I have enough aftermarket gauges to watch what I feel is important.

 

[fsmyth]

Thanks for your answers. I am new to the forum and to Ford N/A 7.3L, but NOT new to
diesels and EGT's. AT my age, have probably driven stuff most of you have never seen.

The truck is N/A. I bought it not too long ago to have somethong to drive while I changed
out the VP44 on mt Dodge, and do not know its history. It looks well used, reasonably
maintained, and not in bad shape for a truck its age. It appears bone stock, with the
exception of a missing air funnel and tube to the ait cleaner. The injectors and glow plugs
are cleaner than the rest of the engine, so have probably been replaced at some point.
The IP soes not APPEAR to have been messed with (the little cover is just as dirty as the
rest of the pump) but that does not mean that it has not. But judging by the condition of
the rest of the engine, I woiuld say not.
The probe is inserted in the driver's side exhaust manifold roughly between the 2cd and
3rd ports on that side, so I was expecting the see it a bit hotter than usual, but not
THIS much. As a matter of fact, the position is roughly the same as on my Mack, but
the Mack manifold is much larger and thicker, so the probe is probably farther from the
middle of the gasses. The probe on my Dodge is in the part of the manifold that turns
down to enter the turbo (I.E., in the composite from all the cylinders at the turbo) and
neither of these installations show normal WOT temps above 950-1075, and cruise much
lower (600-800). The Ford under these same conditions is at 1250 WOT and 850.
ALL drop almost immediatly to 300-375 at idle or no load, depending on ambient.
My only concern was the normal operating range of a non-turboed IDI. I always keep
EGT's below 1200, even when hauling loads that eat tires , and prefer to see temps
below 1100 at WOT. I just never drove a diesel that made these temps this fast with
so little effort at the pedal.
I have installed the gauge on this truck to play with: propane, HHO, water injection.
and WMO mixes (probablye in that order). Base on what I find here, will probably
do much the same on the '98 Dodge 5.9 at some point. I Intend to build a centrifuge
and that (and another fuel tank) will determine when the Dodge gets into the game.

 

[jaluhn83]

The max egt numbers have very little to do with the melting temp of aluminum - it's coincidental that they're nearly the same.

The fact is that if your pistons get much above about 250-300* you're in serious trouble. Just cause it melts at 1200 (any actually probably lower due to the alloying) doesn't mean it's solid up to that point. Over a couple hundred degrees it starts getting soft. Beyond that, thermal expansion will cause the piston to start scuffing.

The pistons are cooled by intake air, heat transfer to the cylinder and the oil spray. Having very hot gasses on the surface does not mean that the bulk of the piston is that temp, any more than a pan on your stove is the same temp as the gas fire under it. It's all about heat transfer.

Also remember that the EGT is the temp of the exhaust - during ignition and the power stroke gas temps are actually significantly higher.

As mentioned above, temps will vary significantly depending on location the thermocouple. Pre vs post turbo will cause as much as 200* difference and distance has some effect too.

Many big rigs use post turbo temps, so 800* on one of them is about the same as 1000* pre turbo.

NA engines will always be hotter than turbo cause you've got less air flow.

I prefer to use ~1150 as a max temp but 1200 is safe and even a bit over that most likely.

 

[PwrSmoke]

The max egt numbers have very little to do with the melting temp of aluminum - it's coincidental that they're nearly the same.

The fact is that if your pistons get much above about 250-300* you're in serious trouble. Just cause it melts at 1200 (any actually probably lower due to the alloying) doesn't mean it's solid up to that point. Over a couple hundred degrees it starts getting soft. Beyond that, thermal expansion will cause the piston to start scuffing.

The pistons are cooled by intake air, heat transfer to the cylinder and the oil spray. Having very hot gasses on the surface does not mean that the bulk of the piston is that temp, any more than a pan on your stove is the same temp as the gas fire under it. It's all about heat transfer.

Also remember that the EGT is the temp of the exhaust - during ignition and the power stroke gas temps are actually significantly higher.

As mentioned above, temps will vary significantly depending on location the thermocouple. Pre vs post turbo will cause as much as 200* difference and distance has some effect too.

Many big rigs use post turbo temps, so 800* on one of them is about the same as 1000* pre turbo.

NA engines will always be hotter than turbo cause you've got less air flow.

I prefer to use ~1150 as a max temp but 1200 is safe and even a bit over that most likely.

Very well explained!

I didn't run my '86 NA with a pyro and since it's had a turbo since '87, I can't even remember how much smoke it cranked out NA. BUT, I think the numbers are a little high even for NA given the lack of a load. I suspect the pump was turned up long ago OR you have a restricted air filter. I wouldn't expect to see over 1000* @ 60 unloaded. Hauling a heavy load or uphill, maybe. Since you are sucking in underhood air as well, duct missing, that's likely adding some temp to the EGT as well (hot intake = hot exhaust). Since you've been observing, it might be an interesting experiment to get the cool air duct reattached and see if it results in lower EGTs (a little or a lot). Restricted intake air on a mechanical diesel is self-explanatory.

I agree on the upper numbers presented above. Even though I have a turbo, I have set the upper sustained limit at 900-950 and peak short term at 1150. Have seen over 1200 a few times in the past 26 years. The numbers have worked well for me over the years but even so, I could see the evidence of one to many dyno runs or 18K GCWR pulls over the Rockies on the valves, heads and head gaskets when I had it apart. I gave away all my old pistons as souveneirs at the rally last year but I saw no evidence of problems there. It was all head related.

 

[Exekiel69]

If all else fails, You might have a leaking injector there which will cause egt's to be higher. Do You use any additives with Your fuel? Maybe You could use some Power service (gray bottle) and see if the temps go lower or pull the injectors and see if there is an obvious leaker.

 

[vanet]

You might look at the exhaust as well. I bought a truck that someone had stuck 1 3/4 pipe on the exhaust with a small gas muffler and it had real high egt's that would get up there quick. I replaced the exhaust with 3" and a banks diesel muffler and my egt's dropped 300 degrees for the same speed.

 

[fsmyth]

I doubt it is the intake temp - it was a cool night (~50 degrees) and the truck was cold.
Numbers are even prior to truck warming to operating temp. Good call on the exhaust;
it has a very large oval-shaped muffler and is VERY quiet (quietest diesel I have ever
driven). May yank it off and see - was intending to replace it with a spare 6" round
stack muffler from the yard (if I could stuff it under there - they are fairly long).
BTW, I was not asking about max temp operation. I have been around trucks long
enough to know pretty much how to treat them. Just wanted input on THIS engine.
AFA additives, I ran one bottle of Power Service Diesel Kleen through right after I got
the truck on ~10 gals diesel. Just for drill. Did not seem have any effect.
Thanks all.

 

[icanfixall]

I doubt it is the intake temp - it was a cool night (~50 degrees) and the truck was cold.
Numbers are even prior to truck warming to operating temp. Good call on the exhaust;
it has a very large oval-shaped muffler and is VERY quiet (quietest diesel I have ever
driven). May yank it off and see - was intending to replace it with a spare 6" round
stack muffler from the yard (if I could stuff it under there - they are fairly long).
BTW, I was not asking about max temp operation. I have been around trucks long
enough to know pretty much how to treat them. Just wanted input on THIS engine.
AFA additives, I ran one bottle of Power Service Diesel Kleen through right after I got
the truck on ~10 gals diesel. Just for drill. Did not seem have any effect.
Thanks all.

Well from what you just posted here I'm thinking now you have two issues causing the hiher than normal temps. Your timing is retarded causing the heat to be burning more in the exhaust like a retraded gasser does. I have seen the exhaust glow red when they are retarded plenty. then the muffler. those will fill up with soot and restrict the flow thru the system causing high exhaust temps. Getting to engine timed is what I would recomment first.. finding a shop to do that is nearly impossible these days. Post up your location and maybe a member with a meter lives near you.

 

[fsmyth]

Makes more sense. I think I'll drop the muffler, and see if it improves - the only reason
that I have not already is that, from what I have read, these things are LOUD w/o one.
After that, I will just advance the pump a tiny bit, and see what that does.
Other than temps, it seem to run fine. Smokes very little (usually just on startup), so
I doubt it is over-fueling.

 

[icanfixall]

If the pump is as old as the engine the internal timing might be faulty causing the probable retarded timing. Getting a timing meter on the engine is the best way to determine whats going on. finding a shop that has one is even tuffer.

 

[fsmyth]

Well, I just drug a partially loaded trailer about 5 miles, and it was no problem getting it
up to 1300. Backed way off, and finished the run at 50 mph
If I just advance the pump about 30-50 thousands from where it is, will it hurt anything?
That would tell me it was retarded if the EGT's dropped, no?
Seriously doubt that anyone in this town has a timing setup, and if they do, doubt that
they could use it (Conroe, Tx ).