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-   -   Oval Piston Roll Call!! (https://www.duramaxdiesels.com/forum/showthread.php?t=50878)

sterlinLBZ 09-16-2013 10:51 AM

Mine with a little lower compression will white smoke just a little on a cold start, and very little blow by if any, I havnt seen any but havnt looked real real hard either

MarkBroviak 09-16-2013 05:52 PM

I don't have any glow plugs or grid heater and she is a little cranky on cold start ups below 60 degrees. Thinking about throwing the glow plugs back in to cure this issue but what do you expect at 15.25:1 comp and 200%inj, lol! I don't have any more blow by than a stocker does. You should see the low compression ones on cold start up...:spit:

MarkBroviak 09-16-2013 05:53 PM

How many sets of these pistons are out there now Jon?

Fingers 09-16-2013 06:47 PM

About 40 total of oval design have been made. 30 cast 10 forged. I really don't know how many are actually in running engines.

Kappa9012 09-16-2013 08:33 PM

15.25:1, and those aren't the low compression!!??!??! holy sheet man how low have you gone so far? Isn't stock compression around 18:1?

coldLBZ 09-17-2013 04:10 PM

Jon, how are you liking your 17.5:1 set? How is your MPG? Thanks.

malibu795 09-17-2013 06:00 PM

Quote:

Originally Posted by Kappa9012 (Post 745731)
15.25:1, and those aren't the low compression!!??!??! holy sheet man how low have you gone so far? Isn't stock compression around 18:1?

Quote:

Originally Posted by coldLBZ (Post 745909)
Jon, how are you liking your 17.5:1 set? How is your MPG? Thanks.

16.8 for lbz and newer
17.5 for lb7/lly
who has the 18:1 set?

after siting for ~12 hours fired up in 10* temps in watertown WI, march of this year,with initial cyclce of the GP 17:1
https://scontent-b-ord.xx.fbcdn.net/...95704119_n.jpg

Kappa9012 09-17-2013 10:40 PM

must have gotten confused with our engines at work. I was thinking the dmax was 18:1. Now that I think about it, I'd have to look at and see what something like a C7 would run for compression.

Malibu is that white smoke with johns pistons? are you running larger injectors? I'm kind of curious what kind of white smoke im going to see this winter with the 60 overs.

malibu795 09-18-2013 09:59 AM

Quote:

Originally Posted by Kappa9012 (Post 746025)
Malibu is that white smoke with johns pistons? are you running larger injectors? I'm kind of curious what kind of white smoke im going to see this winter with the 60 overs.

yep johns, that was ~15-20 seconds after start up, after about 1-2 minutes at high idle it cleared up substantially. iirc i had roughly 10-15k on the engine

stock everything except the pistons

Fingers 09-18-2013 01:25 PM

Quote:

Originally Posted by coldLBZ (Post 745909)
Jon, how are you liking your 17.5:1 set? How is your MPG? Thanks.

MPG is about the same as it was before the pistons. I could use some better injectors. ~15 city 17-18 highway.

If I redo these, I'll drop mine to 16:1 the higher CR rattles too much for my taste.

Haze seems to be more a function of injectors than CR to a point.

MarkBroviak 09-18-2013 05:48 PM

Quote:

Originally Posted by Kappa9012 (Post 745731)
15.25:1, and those aren't the low compression!!??!??! holy sheet man how low have you gone so far? Isn't stock compression around 18:1?

12.5-12.8ish is the lowest I have currently running right now with success. Mine with 200% overs doesn't have any notable haze to it and without glow plugs or grid heater it starts decent for how low the compression is. Will be putting the glow plugs back in soon though, lol! I'm getting a lot better mileage right now than I did with the twins and 100% inj. which is surprising to me.

rgullett83 09-18-2013 06:14 PM

hopefully around the first of the year I can provide feedback.

dirty_max 09-18-2013 09:49 PM

Quote:

Originally Posted by Kappa9012 (Post 746025)
must have gotten confused with our engines at work. I was thinking the dmax was 18:1. Now that I think about it, I'd have to look at and see what something like a C7 would run for compression.

Malibu is that white smoke with johns pistons? are you running larger injectors? I'm kind of curious what kind of white smoke im going to see this winter with the 60 overs.

compression ratio for a c7 is 16.5. for the "wax" and "c7s" anyways

Kappa9012 09-18-2013 10:33 PM

I just double checked, C7's run 16.5:1 like you said, and tier 4i C9's are 17:1.


Malibu what CR are your pistons? also do you still have the grid heater and glow plugs? I'm assuming that was white smoke, and not just steam?

baggedLB7 09-19-2013 06:13 AM

Quote:

Originally Posted by malibu795 (Post 746112)
yep johns, that was ~15-20 seconds after start up, after about 1-2 minutes at high idle it cleared up substantially. iirc i had roughly 10-15k on the engine

stock everything except the pistons

Didnt you say you had some ring gap problems though?


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