LB7,LLY, LBZ piston failure question.

Trippin

SoCal Diesel
Aug 10, 2006
663
2
0
Heat, Heat, Heat.

Watch your heat guys, drive pressure, EGT, oil temperature, IAT all play a part.
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
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Wyoming
Heat, Heat, Heat.

Watch your heat guys, drive pressure, EGT, oil temperature, IAT all play a part.

I agree completely. IMO heat is the main reason these pistons fail. You can try the "tuning to reduce cylinder pressure" stuff but it still 'boils' down to the heat the pistons are exposed to.

why dont cummins pistons crack. because they have probably twice the mass of dmax pistons.

thats why I jumped on the opportunity to buy that used set of twins. They offer unbeleivably low drive pressures and EGT's. With lower DP and EGT's comes lower oil temps.
 

sweetdiesel

That's better
Aug 6, 2006
10,390
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Thailand
I agree completely. IMO heat is the main reason these pistons fail. You can try the "tuning to reduce cylinder pressure" stuff but it still 'boils' down to the heat the pistons are exposed to.

why dont cummins pistons crack. because they have probably twice the mass of dmax pistons.

thats why I jumped on the opportunity to buy that used set of twins. They offer unbeleivably low drive pressures and EGT's. With lower DP and EGT's comes lower oil temps.


how much lower drive pressure?
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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Wyoming
not sure. low enough to not allow EGT's to get over 1300* on a 0-110mph run.

stock turbo would see 1800* by that point. BD/HTT was better, but not by much.
 

codyn

Member
Aug 26, 2007
412
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16
urbana ohio
not sure. low enough to not allow EGT's to get over 1300* on a 0-110mph run.

stock turbo would see 1800* by that point. BD/HTT was better, but not by much.

cummins will see over 1300* from 0-110mph run. depends what done to them mine would get up to 1800* sometimes. cummmins pistions could be made of a different cast or different process to.
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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if drive pressure with the HTT is 1:1 then why were my EGT's always high with it. I ran every friggin tune imaginable and they always got to ~1700* during a 1/4 mile run. Almost 2000* on dyno runs.

I dont see how 1:1 is obtainable without a VVT like braydens?
 

sweetdiesel

That's better
Aug 6, 2006
10,390
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if drive pressure with the HTT is 1:1 then why were my EGT's always high with it. I ran every friggin tune imaginable and they always got to ~1700* during a 1/4 mile run. Almost 2000* on dyno runs.

I dont see how 1:1 is obtainable without a VVT like braydens?


I tried many many tunes with the HTT and not a single tune would go over 1:1 ratio it had nothing to do with EGTS some tunes would max egts at 1400f and some upwards of 2000f with duel cp3s on....its simply how you tune it.....not drive pressure IMO and testing
 

LarryJewell

Back with his honey :)
Jan 21, 2007
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San Angelo
if drive pressure with the HTT is 1:1 then why were my EGT's always high with it. I ran every friggin tune imaginable and they always got to ~1700* during a 1/4 mile run. Almost 2000* on dyno runs.

I dont see how 1:1 is obtainable without a VVT like braydens?

And a little less than 1 - 1 is obtainable ;)
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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Wyoming
I tried many many tunes with the HTT and not a single tune would go over 1:1 ratio it had nothing to do with EGTS some tunes would max egts at 1400f and some upwards of 2000f with duel cp3s on....its simply how you tune it.....not drive pressure IMO and testing

Yeah I thought it was my tuning too. But then I tried a bunch of other tunes.

all of mcrats tunes put mine 1700*
 

sweetdiesel

That's better
Aug 6, 2006
10,390
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Thailand
Yeah I thought it was my tuning too. But then I tried a bunch of other tunes.

all of mcrats tunes put mine 1700*

Still you jumped on the chance to buy twins to reduce dp and you dont even know what it was with stock, HTT or the twins.....So how do you even know? Ive read about others with 1:3 ratio on twins:dontknow:

I still i like the idea of lower EGTS,but dont think you can't destroy a block cause you are running twins do to the less heat and DP
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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Wyoming
Ill see how it goes. The general consensus is that twins are much easier on the engine, whether its cooler temps, lower drive pressures, etc...

The only person that has hurt an engine with twins (that I know of) is subman631, and he bent a rod. No cracked pistons or anything.
 

WolfLMM

Making Chips
Nov 21, 2006
4,005
26
48
38
AL
FWIW my truck has never seen over 1500 degrees EGT. Even with the dual pumps. Maybe my gauge isnt reading accurately?