thoughts on bumping up compression

Dont you know i do everything that folks say wont work......and for some reason it does......im confused....<<<< That did not take much, did it..LOL


Dave i know your true love is the d-max, just messin...


my compression, yes around 20:1......it's the rest of the puzzel that will getcha!

Compression is free HP....If you know how to applie it in your complete build..
 
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Last year before TS I built 3 duramaxes, a LB7, LLY, and my LBZ. All 3 at approx 20:1 compression. We pulled all year on them and 2 have been torn back down and inspected. The only thing I noticed was increased rod bearing wear. Everything else looked normal.
 
Wade,
20:1 isn't terrible when you only run 40 pounds of boost.... Run 130PSI, spin the bish to 6 grand, and pull 2 shifts before the 330 and call us back LOL
 
jneal said:
Last year before TS I built 3 duramaxes, a LB7, LLY, and my LBZ. All 3 at approx 20:1 compression. We pulled all year on them and 2 have been torn back down and inspected. The only thing I noticed was increased rod bearing wear. Everything else looked normal.
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Wait... so Wade wasn't first? Holy. $hit.
 
Timbeaux38 said:
Wade,
20:1 isn't terrible when you only run 40 pounds of boost.... Run 130PSI, spin the bish to 6 grand, and pull 2 shifts before the 330 and call us back LOL
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I wish i only had to deal with 40psi. I'm hoping i can get by with around 60. Maybe some ratchet straps to help hold the head down.
 
paulb said:
Not that I remember. I replaced the rods with billet, so I wasn't to concerned. The bearings were crushed wider. They looked like classic gasser detonation destroyed bearings, except worse...

Paul
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Had a look back inside yet to see how well cap register held up (not sure which billet you got)?
 
Timbeaux38 said:
Wade,
20:1 isn't terrible when you only run 40 pounds of boost.... Run 130PSI, spin the bish to 6 grand, and pull 2 shifts before the 330 and call us back LOL
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im in third by the 300 mark, but whats it matter....boost does matter in that equation tho......130psi......i cant hang. sorry
Timbeaux38 said:
Wait... so Wade wasn't first? Holy. $hit.
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my engine was built in 2008....just sayin
 
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jneal said:
Last year before TS I built 3 duramaxes, a LB7, LLY, and my LBZ. All 3 at approx 20:1 compression. We pulled all year on them and 2 have been torn back down and inspected. The only thing I noticed was increased rod bearing wear. Everything else looked normal.
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How much more wear real bad needs replaced soon or something that will still last a while.
 
SPEAKSUP said:
How much more wear real bad needs replaced soon or something that will still last a while.
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Nothing too severe. The bearings could have made it a good while longer. But you could definately tell the were taking more of a beating with the upped compression.
 
jneal said:
Nothing too severe. The bearings could have made it a good while longer. But you could definately tell the were taking more of a beating with the upped compression.
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Am I correct in assuming all 3 are single charger trucks?
 
How much is cylinder pressure raised with compression alone? Say you have two identical engines one with 20:1 the other with 16:1. Anybody know that formula? While agree with high compression benefits, it would worry me as these larger displacement motors are already having crank problems... its not like we have a whole bunch of options for crank strength right now without spending a chitload of money.

I understand you wouldnt run the same amount of timing on both motors, just wondering how much more pressure we are talking with that kind of increase.

Also, what are the benefits of running high cr, when timing gives similar results? Just keep the timing and save the money?
 
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SPEEDSHIFT said:
I understand you wouldnt run the same amount of timing on both motors, just wondering how much more pressure we are talking with that kind of increase.

Also, what are the benefits of running high cr, when timing gives similar results? Just keep the timing and save the money?
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are you gonna rely on high boost (and hope your turbo combo is efficient there) to build cylinder pressure? or increase compression ratio and hope your cylinder head can flow enough to make the same power at a lower boost level? (or try and run the same boost as before and look at the new hole in your block)

think about it, when building a turbo gas engine it requires less compression becuase your going to fill it in with boost.

control of cylinder pressure is key to consistency and longevity of a diesel engine.
 
Control of cylinder pressure is the key to longevity on a boosted gasser too.

Compression is generally lowered to keep it pump gas friendly with boost. Some high end race cars on alcohol run 13:1 or more compression and 50+ psi. But they are tuned to the teeth.

Yes, advancing timing DOES increase cylinder pressure on a diesel. But if its too advanced you are gonna knock your rod back into the crank, just like any other internal combustion piston engine. So, when timing is perfect, and you are at whatever boost you want to run, cylinder pressure will be xxxxpsi, advance timing one degree or two or three, yes, cylinder pressure skyrockets, but it is being counterproductive to making more rpms or horspower.
 
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another thought after reading hamiltons post towards drag racing, more compression could be a benefit for a very lightweight rig that has trouble staying on top of the charger beacause at its power level the weight of itself is not enough to put load on the turbine required to support its power or range of operation, but compression might be the trick
 
SPEEDSHIFT said:
How much is cylinder pressure raised with compression alone? two identical engines one with 20:1 the other with 16:1. Anybody know that formula? what are the benefits of running high cr, when timing gives similar results?
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Static compression ratio is completely different from dynamic C/R - no useful formulae, in view of the plethora of variables that affect it, but most of the sim SW does a reasonable job of spitting out D-C/R if accurate data is used.

crackerman said:
Compression is generally lowered to keep it pump gas friendly with boost. Some high end race cars on alcohol run 13:1 or more compression and 50+ psi. But they are tuned to the teeth.
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"High-end" C/R these days, for turbo methanol, is 18-20:1 static.
 
jneal said:
Nothing too severe. The bearings could have made it a good while longer. But you could definately tell the were taking more of a beating with the upped compression.
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What type of oil where you running and where the bearings coated?
 
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