Dieseldude4x4

Don't know, how hot was this?

https://www.dieseltruckresource.com/...cat=500&page=4


https://www.dieseltruckresource.com/...cat=500&page=4


I know it was about $11000 worth of hot though.

Underpsi

You also melted your pistons though

Bart Timothy

Herb, there's something going on with your '01 which doesn't seem right. Wonder how accurate the pyro is? What boost level, coolant temp, and rpm are you running at on those pulls?

rockjeep73

Get your facts straight, the pistons didnt melt because of high EGT's, in fact the EGT's were well in the safe zone when it happened.

herb

been trying to my my facts straight for two years with thist ruck. Dodge and Cummins both says the pistons melted because the engine got too hot.
the gauges have never indicated it was hot. gauges and thermostat have/had been changed.

linetrash75

Herb, Your Eazy Edge would be my guess as to what is killing your engine. It is advancing the timing so your 1200* is in the cylinder longer plus the fact that your towing a substancial load with truck what 90% of the time. Just look at the big rigs and farm tractors they are designed to be run at or near max engine load all day long, timing is nowhere near as advanced as what a stock ctd runs. The EZ gives the heat more time to work on melting your pistons by igniting the fuel sooner. Advanced timing is great for short runs such as drag racing or pick-pulls,etc.. This is something i have noticed on here several times but, never said for fear of getting whipped .
Also your 01 auto has a HY-35 I think, It might be a step in the right direction to find a HX-35 off a manual tranny truck. this would cool better since you have 275's and the EZ. JMHO

Jed

gwhammy

Over 1700 on the 97 with the hx40 at 50 lbs of boost. I decided to set the boost back at 40 to keep from injesting it threw the motor! Don't have a pyro on the other two trucks!

red12valve

Don't know, guage only goes to 1600

Underpsi

you can't prove that nothing happened previous to the pistons before the meth melted them. 1800 deg is well out of the safe range whihc you said you have taken it many times before.

rockjeep73

Well since you know the whole story then I guess a visual inspection of the pistons and cylinders while the head was off for o-ringing doesnt prove a thing. Thanks for clearing that up.

HOHN

This deserves to be expanded upon.

Does HIGH EGT melt pistons?? NO IT DOES NOT!! How can you say this, Hohn you pompous windbag?


Let's say you see 1300° on your pre-turbo pyrometer. This is the temperature of the gasses in the exhaust manifold.

But those gasses in the manifold have already cooled a LOT. I mean A LOT!

Think about it-- you have a combustion event happening in a confined space, but then that space expands up to 17 times! What happens to a gas when it expands? IF YOU SAID IT COOLS, GO TO THE HEAD OF THE CLASS.

You see this all the time in your daily life. When you use canned air or any aerosol, the can gets cold after you've been spraying. Why? Because as the product is dispensed, the compressed charge expands, and this cools it.

You see the opposite, too with your air compressor heating the air as it compresses it, just like your turbo charger does, and just like the pistons do. Without this thermodynamic law, a diesel engine wouldn't be possible!!!


Let me state the obvious for a starting point: pistons melt when PISTON TEMPS get too hot. They don't melt from high EGT!

Now, high exhaust temps are often an indicator of high piston temps, too. But there's a LOT more that goes into determining piston temperatures than just exhaust temps. In fact, piston temperatures are exhaust temps are NOT related by cause and effect, but rather they are both effects of OTHER causes.

So high EGTs don't cause high piston temps (and therefore can't "cause" melted pistons), but rather they are both a result of a combination of factors, including:
1) Air/fuel ratio
2) Intake air temp and pressure
3) Engine compression ratio
4) Engine TIMING
5) Combustion efficiency (injector pressure/design, etc)
6) Presence of any pre-injection fuel source (propane/methanol, etc)

Now the majority of the above factors are just going into determining the characteristics of the combustion event (rate, temp, pressure, etc).

But some of them also determine HOW that combustion event effects the PISTONS!

For example, a higher compression ratio helps pistons to run cooler. Yes, the peak temperatures at combustion may be higher, but this is only for a moment. The higher compression ratio also means a higher EXPANSION ratio, which means that the temperature drops off from its peak value more quickly. Also, since the peak cylinder pressure just BEFORE injection is higher (with higher compression), the fuel charge will burn more quickly and earlier, which both help to lower EGT and average piston temps.

Timing, as you can see, plays a big role in piston temps because it has such a large effect on peak cyl pressure, which determines how "deep" the heat will penetrate into the piston.

So, remember these basics about how heat works. Some factors to consider:
1) The difference in temperatures
2) The medium though which the heat is conducted, both from one piece to another, and within each piece itself. This determines the RATE that heat is conducted
3) The TIME that the heat differential exists

So, as it related to PISTON Temps, consider this:
1) How hot the combustion event gets
2) HOW LONG the piston sees a given temperature
3) The cylinder pressure, as this determines how a given temp and a given time will heat the piston (less "insulating" effect from a boundary of gases).

Obviously, each of these has a slew of sub-factors, but that's what it boils down to.


All that to say that with radically advanced timing at a sustained high load, I could melt a CTD piston with EGTs that never went past 1000°.

Conversely, at light load with proper timing, the engine can handle short burst of insanely high temps with no melting at all.


EGT is important, but there's a LOT MORE to determining if you are "safe" or not than just the numbers on the pyro.....


Justin

linetrash75

Hohn. That is exactly what i was thinking, i would be willing to bet more aggressive timimng boxes have ruined pistons, than the wildest of fuel boxes ever have or will. People need to understand that when it comes to bombing these trucks you need to make an evaluation of if its a work truck or a play truck. I also felt that timing was the reason Hauln in Dixie had so much trouble. To state it simply if your going to be towing more than golf cart regularly stay away from timing modds and work on fuel and air, If its a play truck or dayly driver go wild. I wish more people would chime in and give their 2 cents on this it would greatly help the Dodge/Cummins community we have here.

Jed

inline6power

i couldnt agree more with both of you. thats y your not suppost to stack 2 timing boxes together..................like me with the drag comp and the VA but i am going to sell them both and go with a smarty TST stack. but i think HoNn nailed it on the head with his explanation very nice and detailed. thanks honn

herb

So if I am understanding correctly, even the small (65 hp gain) Edge effects the timing enough to cause piston failure when using vehicle predominatly for a heavy tow vehilce ?

Bart Timothy

herb,

I've seen what happened to your truck before, and so I ask, again, what boost, rpm and coolant temps were you running when this happened? Did you notice anything different about the rod bearings?

Bart