What compression ratio?

Evan@InglewoodTrans

Evan@InglewoodTrans

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It's time for me to order pistons and I thought I had my mind made up with a 16.5:1 compression ratio but figured I would get some input before ordering. The truck will see alot of street miles in the summer time only and will have 100 overs and s475/gt55 twins when it goes back together.
 
dmaxfireman

dmaxfireman

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Apr 8, 2007
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higher c/r means less timing needed. so if my thinking is correct you can run less timing and more fuel without injection event overlap with a higher c/r
 
ecc_33

ecc_33

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IMHO I wouldn't ever go high compression on a modded duramax. IMHO i think this is why alot of aftermarket rods/parts have been failing is becuase of this. Good luck keeping it together with that much air and high c/p. Just remember, If it were such a good idea to go up in c/r all the tractor pullers/ turboed car guys would be doing it too:thumb: I wouldn't go any higher than what you were going to go for before.
 
Evan@InglewoodTrans

Evan@InglewoodTrans

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ecc_33 said:
IMHO I wouldn't ever go high compression on a modded duramax. IMHO i think this is why alot of aftermarket rods/parts have been failing is becuase of this. Good luck keeping it together with that much air and high c/p. Just remember, If it were such a good idea to go up in c/r all the tractor pullers/ turboed car guys would be doing it too:thumb: I wouldn't go any higher than what you were going to go for before.
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I have no intention on running higher C/R. I guess what I should of asked is how low to go. As far as the air goes i'm not to worried about it things break it is what is, but I would rather have way to much and back it down than have just enough and want more down the road.
 
delong_1

delong_1

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I'm at 16.5/1 since it is a year round dd. Doesn't start too bad considering all that's been done. Personally I wouldn't want anything lower than this if temps get much below 30*
 
02bigstrokin

02bigstrokin

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are you going forged pistons or cast? if forged i would go 17.1. thats what mine are and it doesnt white smoke barely at all even at 32 degress outside. it will cough a little smoke on initial start up for about 5 seconds then just a slight black haze and that is with 100% injectors. cast i probably wouldnt go any higher then stock because your going to be pushing them very hard with that turbo setup already.
 
Evan@InglewoodTrans

Evan@InglewoodTrans

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02bigstrokin said:
are you going forged pistons or cast? if forged i would go 17.1. thats what mine are and it doesnt white smoke barely at all even at 32 degress outside. it will cough a little smoke on initial start up for about 5 seconds then just a slight black haze and that is with 100% injectors. cast i probably wouldnt go any higher then stock because your going to be pushing them very hard with that turbo setup already.
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Cast i'm going to give fingers pistons a try.
 
ecc_33

ecc_33

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lb7dirtymax01 said:
I have no intention on running higher C/R. I guess what I should of asked is how low to go. As far as the air goes i'm not to worried about it things break it is what is, but I would rather have way to much and back it down than have just enough and want more down the road.
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I didn't mean with just the air. I ment if you went with high compression and that much air I would bet you will end up with problems. IMHO with that much air i wouldn't go any highter than 16 to 1 with cast pistons
 
delong_1

delong_1

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Didn't add all the info, it starts just fine to about 30* a bit of white smoke for a few sec then it idles clean. Any colder and it coughs a bit and obviously smokes white longer

My other motor had lower compression and even though it had other issues the new motor is making power a lot easier. could just be because it was assembled properly though
 
jneal

jneal

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With that much air I'd just stay around the 16.5:1 mark. Higher compression pistons have there place in air restricted setups like sled pullers. But in your case you won't have to worry about air. Lol
 
juddski88

juddski88

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Mine are a 16:1 forged Evan, starts up fine. I don't agree with others that higher compression ratio = failure in parts. If you want real cylinder pressure information, talk to Steve Cole or Mick or his tuner Mike or Fingers himself. Your motor and turbos and total setup will be very similar to mine, I look forward to it. Also, my opinion on tractors not using high compression pistons is because they don't need to,static compression ratio isn't everything;)
 
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