i have a turbo and am turning up my fuel im scared of meting pistons. i cant seem to find high temp pistons if anyone knows some please tell me. or if you know what's the meting point of the pistons and if its enough that i even need to worry about meting.
melting point/high temp pistons
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david85
Full Access Member
EGTs can be measured either before the turbo, or after the turbo. If measuring after the turbo, assume a 300F drop across the turbine (pistons will be 300F hotter than what your gauge is reading).
The general rule for diesel engines goes something like this:
1. Never exceed 1200F. If running at 1200F, this must be only for brief moments. A few seconds, for example. Not 5 min.
2. Running at 1000F continuously is probably ok.
3. If measuring temperature after the turbo, your limits would be 900F and 700F, respectively.
The general rule for diesel engines goes something like this:
1. Never exceed 1200F. If running at 1200F, this must be only for brief moments. A few seconds, for example. Not 5 min.
2. Running at 1000F continuously is probably ok.
3. If measuring temperature after the turbo, your limits would be 900F and 700F, respectively.
Kevin 007
Full-floater
Melting point, as mentioned above....is a bit over 1200 degrees.
Your EGT's are simply that....a measurement of the exhaust gas temps. These are the temps that the pistons and valve train are exposed to. This doesn't mean that your components are necessarily at that temp...yet, it just means thats what they are currently exposed to. It takes a little while before that exposure raises the temps of those components to the same temp as the exhaust.
So you can spike your EGTS over 1200 for short periods of time...like when cresting a hill, passing etc... But if you hold those temps over 1200 for any length of time...like the duration of a mountain pass...thats when you start having problems. These problems may not present themselves right away...but over time, your rings start loosing tension, your ring lands become more deformed, your exhaust valves and seats take a **** kicking... etc... Then you start getting more blow by, more oil consumption, exhaust valve/guide/seat issues, cracking pre cups/heads/pistons etc.
So my rule of thumb is for long extended grades....keep the EGTS (if measured in the manifold), to no higher than 1100 but ideally more like 1000. But there are lots of times where I see 1200-1300 for short times like for short steep hills where the end is in sight, and im trying to keep up with traffic. It'll be at 1300 for maybe 10 seconds, then drop. The pistons themselves don't have a chance to reach 1300 themselves, in that short amount of time. And if you run high EGTs for extended pulls, you start running into coolant temp problems also as the cooling systems have a hard time keeping up in hot weather.
These engines are getting old now. We want them around for years to come yet. So be mindful of EGTs, boost, coolant temps etc. Don't push the limits. Work them hard, yet be considerate and be happy for a long time.
Your EGT's are simply that....a measurement of the exhaust gas temps. These are the temps that the pistons and valve train are exposed to. This doesn't mean that your components are necessarily at that temp...yet, it just means thats what they are currently exposed to. It takes a little while before that exposure raises the temps of those components to the same temp as the exhaust.
So you can spike your EGTS over 1200 for short periods of time...like when cresting a hill, passing etc... But if you hold those temps over 1200 for any length of time...like the duration of a mountain pass...thats when you start having problems. These problems may not present themselves right away...but over time, your rings start loosing tension, your ring lands become more deformed, your exhaust valves and seats take a **** kicking... etc... Then you start getting more blow by, more oil consumption, exhaust valve/guide/seat issues, cracking pre cups/heads/pistons etc.
So my rule of thumb is for long extended grades....keep the EGTS (if measured in the manifold), to no higher than 1100 but ideally more like 1000. But there are lots of times where I see 1200-1300 for short times like for short steep hills where the end is in sight, and im trying to keep up with traffic. It'll be at 1300 for maybe 10 seconds, then drop. The pistons themselves don't have a chance to reach 1300 themselves, in that short amount of time. And if you run high EGTs for extended pulls, you start running into coolant temp problems also as the cooling systems have a hard time keeping up in hot weather.
These engines are getting old now. We want them around for years to come yet. So be mindful of EGTs, boost, coolant temps etc. Don't push the limits. Work them hard, yet be considerate and be happy for a long time.
Olds64
Full Access Member
I wouldn't "turn up" my fuel delivery screw simply to roll coal. I've read about the 1200* EGT limit before though.
If you run above 1200 frequently, the pistons won't melt, but they'll eventually hairline crack because they'll start to soften up at those temps.
If you find a steel piston, that would be the best way to get higher temps, but they are heavier, so performance gains could be debatable.
Not sure if anyone makes steel pistons for these though.
If you find a steel piston, that would be the best way to get higher temps, but they are heavier, so performance gains could be debatable.
Not sure if anyone makes steel pistons for these though.
david85
Full Access Member
Apparently the latest versions of the ford 6.7 uses steel pistons. I was surprised to read about that. Aftermarket also offers steel pistons for racing applications (not for IDI's though).
Black dawg
Registered User
I have said this many times on here, but you will run out of cooling system before sustained egt is an issue.
I dont think the idi design transfers heat from combustion into the piston very well....compare to a di piston where there is much more surface area, and fire is deep down in the piston bowl.
Of course the harder you run it, the less time it lasts, so setting a personal limit is good, but I have still yet to see melted diesel pistons due to excessive egt.........lots from failed injectors though.
1250egt has been the stated industry standard since as long as I remember, funny since basically no factory stock turbo diesel will stay below that max.....some a couple hundred degrees more, and seem to have lived pretty long lives.
I dont think the idi design transfers heat from combustion into the piston very well....compare to a di piston where there is much more surface area, and fire is deep down in the piston bowl.
Of course the harder you run it, the less time it lasts, so setting a personal limit is good, but I have still yet to see melted diesel pistons due to excessive egt.........lots from failed injectors though.
1250egt has been the stated industry standard since as long as I remember, funny since basically no factory stock turbo diesel will stay below that max.....some a couple hundred degrees more, and seem to have lived pretty long lives.
nelstomlinson
Full Access Member
If you get the top surface of the pistons hard anodized, that will slightly slow the heat transfer from those brief periods of too-hot EGTs.
Wasn't there someone selling hard anodized pistons?
Wasn't there someone selling hard anodized pistons?
FrozenMerc
Full Access Member
Black Dawg makes a very good point. For a bit of real world data, the company I work for remanufactures Kubota 3 and 4 cylinder, IDI NA and Turbocharged engines. We Hot Test everyone on the dyno before shipment. The engines are monitored for EGT's among other data points. When testing at peak torque and peak power, we limit the EGT's to 1400 deg. F. I have pulled plenty of these engines down for quality checks after testing and have never once seen a melted piston.
I have also seen many, many melted pistons on all sizes of engines ranging from 900 cc to 18 Liters, 99% of the time, it was due to a failure of the injector tip that resulted in severe over fueling. A much more common failure mode in high pressure common rail setups that have a large supply of high pressure fuel in the system that flows to the injector with the damaged tip. Mechanical injection pumps like our old IDI's are somewhat self metering in that regard.
I have also seen many, many melted pistons on all sizes of engines ranging from 900 cc to 18 Liters, 99% of the time, it was due to a failure of the injector tip that resulted in severe over fueling. A much more common failure mode in high pressure common rail setups that have a large supply of high pressure fuel in the system that flows to the injector with the damaged tip. Mechanical injection pumps like our old IDI's are somewhat self metering in that regard.
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asmith
Full Access Member
I know there was talk of ceramic coating the piston. The thought was this would protect the piston from higher temperatures for longer. Some people brought up there may be an issue if pieces ever come off. Not sure if anyone has ever actually done it though.
I try to keep my temps below 1200, and sustained below 1100. I have spiked it for several seconds above 1300 on a few occasions. I haven't torn the engine down, but hasn't seemed to hurt it yet.
As said, it seems most people with modern diesels dont have any issue with running much hotter with their egts. I have never looked into what their pistons are made of. I do know the 6.7 powerstroke uses steel.
I try to keep my temps below 1200, and sustained below 1100. I have spiked it for several seconds above 1300 on a few occasions. I haven't torn the engine down, but hasn't seemed to hurt it yet.
As said, it seems most people with modern diesels dont have any issue with running much hotter with their egts. I have never looked into what their pistons are made of. I do know the 6.7 powerstroke uses steel.
03wr250f
Full Access Member
generally 1250* is considered the safe limit.
I take it with a grain of salt. I have no issue holding 1200-1250 even while towing, and spiking over that for brief periods of time isnt an issue either.
the pistons are made from an aluminum ALLOY, aluminum melts at 1250, but the alloy has a higher melting point, and the pistons are oil cooled, helping pull heat from them.
If towing i tend to keep my egts to 1100-1150, simply because on long grades it will raise oil temps, which in turn raises coolant temps, all this being measured in the manifold
I take it with a grain of salt. I have no issue holding 1200-1250 even while towing, and spiking over that for brief periods of time isnt an issue either.
the pistons are made from an aluminum ALLOY, aluminum melts at 1250, but the alloy has a higher melting point, and the pistons are oil cooled, helping pull heat from them.
If towing i tend to keep my egts to 1100-1150, simply because on long grades it will raise oil temps, which in turn raises coolant temps, all this being measured in the manifold
