Duramax Monotherm Pistons
- Thread starter Trippin
- Start date
That's what I want, and why I went LBZ. So I could "tap-shift" and control the trans. It was fail. Thousands of dollars and about 100 hours down the toilet.
Trust me, I've pondered it. Just don't know how a ZF-6 will handle 900+ rwhp sustained.
Rounded up some pistons this morning and ran them across the scale. These are pistons only, no pins or rings.
LB7/LLY +.020 Piston 845-860 grams. (Cut and Coated 16.8:1 compression)
LBZ/LMM Std. Bore Piston 918 grams. (16.8:1 compression)
LML Std. Bore Piston 834 grams (16.8:1 compression)
Forged Stock Stroke +.020 Piston 847 grams. (16.5:1 compression)
Duramax Billet Monotherm +.020 Piston 1064 grams. (16.5:1 compression)
LB7/LLY +.020 Piston 845-860 grams. (Cut and Coated 16.8:1 compression)
LBZ/LMM Std. Bore Piston 918 grams. (16.8:1 compression)
LML Std. Bore Piston 834 grams (16.8:1 compression)
Forged Stock Stroke +.020 Piston 847 grams. (16.5:1 compression)
Duramax Billet Monotherm +.020 Piston 1064 grams. (16.5:1 compression)
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This is physically/literally impossible on an allison. It is 100% electronically controlled; a clutch-to-clutch automatic needs electronic controls in order to even function at all.
Now that's low........
You cut me deep, very deep.
Inside joke. He is being sarcastic.
This is what Chevy says on the 2012 engine flyer.Guy I was almost positive the LML pistons are 16.0:1, not 16.8:1???
Or did the Allison Eng'g department think it was a crank call?
*Ring* *Ring* *Ring*
Please Press One For English.
Eng Dept: Hello how my I help you?
Caller: Yes good day. The other day I was driving my Duramax Allison equipped vehicle and I noticed that when I creased 120 MPH my Allison would no longer downshift and hunted for a gear. Can you help me?
Eng Dept/caller: Silence
Caller: Hello is there anyone there?
Eng Dept: Excuse me could you repeat that?
Caller: Yes [The other day I was driving my Duramax Allison equiped vehicle and I noticed that when I creased 120 MPH my Allison would no longer downshift and hunted for a gear. Can you help me?]
Eng Dept: Thats what I thought you said. Fred is that you ? (Fred's the guy in the cubicle next to his. ) Real funny Fred don't you have anything better to do?
Caller: No this isn't Fred it's Pat can you help me or point me to someone who can?
Eng Dept: Ya ok Fred err a Pat hold on.
Caller: Ok
Eng Dept: Hello this is Peggy ( think about the Discovery CC Commercial)
Caller: Hello Peggy.
*Click* *Click* *Click*
Caller: Hello Hello
Pat: Dam we got disconnected ,I'll try back later!
Guy I was almost positive the LML pistons are 16.0:1, not 16.8:1???
Ben,
The LML piston bowl volume is the same as the LBZ/LMM at 41cc. So I believe the compression ration is 16:8 just like the LBZ/LMM.
Guy
Hypothetical:
Two pistons, same bowl volume, but one has a shorter distance from wrist pin center to top of piston, you would have different CR...correct?
Not that this is or isn't the case, just wondering as I know some have done exactly that (taken material off the top) and they still function but effectively lowering the CR. Edit: I realize it lowers CR for two reasons (less bowl volume now because it's shallower and material removed from top), but I think you get where I was going (maybe a shorter piston height or is that not feasible for emissions...)
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I know guys on the dyno can use the controls via tech II or efi Live to force the trans to lock into gear, is that feasible for this? Maybe Ben or someone could come up with a black box and switch that would disable downshifts? I don't know, just thinking out loud.
In theory you are correct. shorter compression height = less compression, all else being the same. However, as the piston to cylinder head clearance increases, so does the emissions output, which is why GM has 3 different head gaskets.
In this case, the compression height is equal, at 1.961.
Guy
Or did the Allison Eng'g department think it was a crank call?
*Ring* *Ring* *Ring*
Please Press One For English.
Eng Dept: Hello how my I help you?
Caller: Yes good day. The other day I was driving my Duramax Allison equipped vehicle and I noticed that when I creased 120 MPH my Allison would no longer downshift and hunted for a gear. Can you help me?
Eng Dept/caller: Silence
Caller: Hello is there anyone there?
Eng Dept: Excuse me could you repeat that?
Caller: Yes [The other day I was driving my Duramax Allison equiped vehicle and I noticed that when I creased 120 MPH my Allison would no longer downshift and hunted for a gear. Can you help me?]
Eng Dept: Thats what I thought you said. Fred is that you ? (Fred's the guy in the cubicle next to his. ) Real funny Fred don't you have anything better to do?
Caller: No this isn't Fred it's Pat can you help me or point me to someone who can?
Eng Dept: Ya ok Fred err a Pat hold on.
Caller: Ok
Eng Dept: Hello this is Peggy ( think about the Discovery CC Commercial)
Caller: Hello Peggy.
*Click* *Click* *Click*
Caller: Hello Hello
Pat: Dam we got disconnected ,I'll try back later!
Naw it was more like:
Allison: How is Feb 22 for you?
Me: Nope, can you do Feb 28?
Allison: Nope. How about March 17?
Me: Nope. How about April 12?
...
They wanted the truck on the dyno so they could play with it, and I couldn't get me, Casper, Allison, and the dyno in the same place on the same day. Then other things came up, and next thing you know, we were at Bonneville with the problem still. I lost contact after that.
Come on Ben. All you need to do is control the valves, manually. No TCM brain to figure out if you should be in "fifth" just align the clutches for "fifth" and let her fly. Even one of your little computers can do that!
I'll make one for you Pat. You like it, you buy it.