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01-24-2020, 05:22 PM
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#41
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Name: Begle1
Title: Too Much Time
Status: Not Here
Join Date: Nov 2007
Location: Kihei, Maui
Member`s Gallery
Posts: 4,143
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Quote:
Originally Posted by j.fondler
I guess i misunderstood and thought you had the big bowl marine style 155* pistons?
Are they “non-intercooled” pistons or the big bowl marine style?
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I bought ".020-over 286210 Mahle pistons".
I don't know what that means or how I ended up selecting that particular piston when I did so over 5 years ago, but it seemed the consensus common recommendation amongst the people I talked to and it's not like I really knew what I wanted in the first place.
I think they're actually the same pistons non-intercooled first gens had stock, right? I'm unclear if they're also referred to as "marine pistons" or anything else?
And do over-sized pistons really have a different compression ratio? They don't modify the bowl a little to compensate?
__________________
1990 D-250 Regular Cab: Automatic transmission, turkey air horn, wires.
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01-24-2020, 07:33 PM
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#42
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Name: JWhite
Title: Trained monkey
Status: Not Here
Join Date: Aug 2009
Location: F Burg Ohio
Member`s Gallery
Posts: 1,817
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I can't offer advice on what Mahle does (if anything) for the compression, but if the bore size increases and nothing else changes, compression ratio will increase
__________________
GMC with a LiLLY
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01-24-2020, 08:42 PM
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#43
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Name: BigPapa
Title: Truckless
Status:
Here
Join Date: Jan 2008
Location: Springfield, TN
Member`s Gallery
Posts: 5,040
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Quote:
Originally Posted by JWhite
if the bore size increases and nothing else changes, compression ratio will increase
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MMmmm......I'm not sure about that one.
NOT definitively saying you're wrong, just don't sound right to me. From what I understand, you have to change stroke, piston compression height, dome/bowl shape, or the length of the cylinder to change compression.
__________________
Scott
2003 Avalanche Z71
Common sense is like deodorant. The people that need it most never use it.
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01-24-2020, 08:50 PM
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#44
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Name: j.fondler
Title: Slow Learner
Status: Not Here
Join Date: Nov 2016
Location: SD/TX
Member`s Gallery
Posts: 560
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Quote:
Originally Posted by BigPapa
MMmmm......I'm not sure about that one.
NOT definitively saying you're wrong, just don't sound right to me. From what I understand, you have to change stroke, piston compression height, dome/bowl shape, or the length of the cylinder to change compression.
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He is correct, bore increase alone raises compression, all else equal.
__________________
51 F5 - 93 w250 chassis - VE/47rh/np205
67 d100 - 89 d350 srw chassis - VE/a518
93 w250 - VE/47rh/NP205 - BAJA!!!!
12 3500 - studZ, deleteZ, tuneZ
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01-24-2020, 08:57 PM
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#45
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Name: 1972RedNeck
Title: Green Behind the Ears
Status: Not Here
Join Date: Sep 2014
Location: Townsend, MT
Member`s Gallery
Posts: 93
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Quote:
Originally Posted by BigPapa
MMmmm......I'm not sure about that one.
NOT definitively saying you're wrong, just don't sound right to me. From what I understand, you have to change stroke, piston compression height, dome/bowl shape, or the length of the cylinder to change compression.
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If you do the math, it does increase ever so slightly. Doesn't really effect the combustion volume at the top of the stroke, but adds a little at the bottom of the stroke.
My brother runs a non I/C engine with about a half million miles in his Fummins. Engine is completely stock, he just put rings and bearings in it and ground the valves and had the pump rebuilt.
Had a the local diesel shop (really good) put together a set of marine 370's (not opened up at all) and skipped the timing a tooth with the pump at the stock mark. It runs great, knocks out the best mileage numbers for a 12V that I have seen, and yet it will sure clear the parking lot at idle. It will put a souped up Big Cam Cummins on a cold winter day to shame.
If the wind is just right at idle, it will choke you out of the cab in 15 seconds flat.
Pulls hard, runs great, never uses a drip of oil.
I think it's the nature of the beast with these injectors but as said, I would get some miles on it and play with the timing before you spend any money.
__________________
1990 F350 4X4, Sterling 10.25, Dana 60, E4OD
4BTA, HX30W/H1C Compounds, 5X16 Injectors
Quote:
Originally Posted by longhorn859
Assemble, floor it.
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01-24-2020, 11:18 PM
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#46
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Name: BigPapa
Title: Truckless
Status:
Here
Join Date: Jan 2008
Location: Springfield, TN
Member`s Gallery
Posts: 5,040
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Well, thanks for the education. I learn new things from you fellows all the time.
__________________
Scott
2003 Avalanche Z71
Common sense is like deodorant. The people that need it most never use it.
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01-25-2020, 07:35 AM
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#47
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Name: biggy238
Title: Too Much Time
Status: Not Here
Join Date: Aug 2008
Location: Just North of Wrong
Member`s Gallery
Posts: 10,868
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Volume increase of the cylinder.
Sent from my motorola one vision using Tapatalk
__________________
Check out @bdmaximusworx
05.5 Campanella White TDi Jetta 5spd 45.5MPG
-Little Sexy
'10 Silver F250 CCLB 4X4 6.4L cummins Swapped
Insta @trash.panda250
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01-25-2020, 07:53 AM
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#48
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Name: BigPapa
Title: Truckless
Status:
Here
Join Date: Jan 2008
Location: Springfield, TN
Member`s Gallery
Posts: 5,040
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I understand you’re increasing cylinder volume and that compression will increase because of it, but I just don’t see a 0.020” increase in a 4” bore making more than a negligible increase in compression. Maybe somebody smarter than me can do the math and tell us how much the CR would increase for the over-bore.
__________________
Scott
2003 Avalanche Z71
Common sense is like deodorant. The people that need it most never use it.
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01-25-2020, 08:01 AM
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#49
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Name: j.fondler
Title: Slow Learner
Status: Not Here
Join Date: Nov 2016
Location: SD/TX
Member`s Gallery
Posts: 560
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Quote:
Originally Posted by BigPapa
I understand you’re increasing cylinder volume and that compression will increase because of it, but I just don’t see a 0.020” increase in a 4” bore making more than a negligible increase in compression. Maybe somebody smarter than me can do the math and tell us how much the CR would increase for the over-bore.
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An example from one Mahle cummins piston is 16.5/16.6/16.8 for stock/.020/.040
__________________
51 F5 - 93 w250 chassis - VE/47rh/np205
67 d100 - 89 d350 srw chassis - VE/a518
93 w250 - VE/47rh/NP205 - BAJA!!!!
12 3500 - studZ, deleteZ, tuneZ
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01-25-2020, 08:46 AM
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#50
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Name: ofelas
Title: Too Much Time
Status: Not Here
Join Date: Oct 2015
Member`s Gallery
Posts: 285
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Cylinder volume divided by combustion chamber volume (& accounting for the head gasket thickness + piston dish/dome) = compression ratio
__________________
Oversized exhaust tips are false advertising, just like the banana shoved down your britches.
Last edited by ofelas; 01-25-2020 at 08:48 AM.
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01-25-2020, 09:24 AM
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#51
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Name: Smokem
Title: Turbler
Status: Not Here
Join Date: May 2006
Location: Iowa
Member`s Gallery
Posts: 5,565
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Quote:
Originally Posted by BigPapa
Maybe somebody smarter than me can do the math and tell us how much the CR would increase for the over-bore.
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0.14:1
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