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04-14-2007, 07:41 AM
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#1
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Name: 99Binder
Title: Diesel Enthusiast
Status: Not Here
Join Date: Sep 2006
Member`s Gallery
Posts: 202
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Compression Ratio on built motors
Well basically I want to talk compression Ratios on hot diesel trucks, right now BWD and i are putting a motor togeather with RR rods, crower valve springs and push rods, WOP main girdle and fire rings, and a TN GTK76. Im just wondering what kind of compression ratios everyone is running on a hot daily drivable truck. a PSD is 17.5 IIRC and im thinking of dropping it to 16.5 thinking that this will be decent starting truck yet. After talking with a neighbor and a another member of this site i was told to keep as close to stock if im going to drive this truck quite abit. Another possibility the going to a heathy set of twins someday should that be taken into account as well? Thanks wyatt
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Cummin Gitcha Sum
"Im spittin in your face cause im a dominating you" -Hank 3
Last edited by 99Binder; 04-14-2007 at 07:44 AM.
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04-14-2007, 08:46 AM
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#2
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Name: Holysmoke
Title: Diesel Enthusiast
Status: Not Here
Join Date: Mar 2007
Location: Utah by way of Iraq
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Posts: 111
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I would consider my truck to be hot. Mine at 14:1. stock is 17.1:1 I believe. The problem with a hot motor is that you use a can of starter fluid a week.
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ATS 5 star TQ, stand alone valve body, all billet internals, O-ring head, Haisley machine fuel pump, HTT custom twins, Race cam and fly cut pistons.
http://www.youtube.com/watch?v=0B8_6kq1QuQ
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04-14-2007, 09:23 AM
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#3
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Name: Jetpilot
Title: Got Fuel
Status: Not Here
Join Date: May 2006
Location: Hershey, PA
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Posts: 770
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12:1 to 13:1 is a great begining point but starting can be fun.
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2007 Mega-Cab 5.9L, With a few extra parts.....
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04-14-2007, 11:54 AM
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#4
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Name: Distributor
Title: Diesel Doctor
Status: Not Here
Join Date: Aug 2006
Location: S.W. Pa
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Posts: 314
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12 or 13 :1 is what we use in pulling tractors that make 2500+ hp with cyl pressures in the scary range. Its way over kill to drop it that low on a psd or a cummins for that matter.....
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One half of Smoke and Mirrors Detective Agency Inc. LLC.
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04-14-2007, 04:07 PM
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#5
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Name: bonesmx2000
Title: supportn the single moms
Status: Not Here
Join Date: Apr 2007
Location: indiana
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Posts: 494
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ive got a97 dodge and i dropped comp just a lil not quite sure what it is now but with the fuel i have and timeing im running it doesnt want to start at all if its cold out like holy smoke said a can a week and if its cold enuff more like a can a day the other week it was like 70 degrees here and it still didnt start had to shoot it once to get it to fire and then crank and crank till it fired so u might think about that if its really cold where you live good luck
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04-14-2007, 05:08 PM
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#6
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Name: 99Binder
Title: Diesel Enthusiast
Status: Not Here
Join Date: Sep 2006
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Posts: 202
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no im just wondering about dropping it to 16.5 not very much just a little.
__________________
Cummin Gitcha Sum
"Im spittin in your face cause im a dominating you" -Hank 3
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04-14-2007, 07:08 PM
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#7
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Name: duke1n
Title: Banned
Status: Not Here
Join Date: Apr 2006
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Posts: 1,834
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On a 24v what is stock ETC c/r and how much do you lower it by using a .020 gasket?
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04-14-2007, 07:27 PM
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#8
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Name: RacinDuallie
Title: Black Sheep Racing
Status: Not Here
Join Date: Apr 2006
Location: Supporting Northeast Diesel Racing
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Posts: 17,369
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Dukey sounds like you are for a Ford killing combo......
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04-14-2007, 10:53 PM
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#9
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Name: bonesmx2000
Title: supportn the single moms
Status: Not Here
Join Date: Apr 2007
Location: indiana
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Posts: 494
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i think a 24 v is close 2 16.5- 17
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04-15-2007, 12:04 AM
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#10
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Name: SledPuller21
Title: Never enough
Status: Not Here
Join Date: Jan 2007
Location: Pa
Member`s Gallery
Posts: 2,214
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24v is 16.3
__________________
2007.5 6.7 QCSB 6in Superlift Murdered on BMF 20's
1995 ECLB-"Strung Out"
2003 QCLB "Strung Out II"
2013 USA-East Open 2.6 points champion
Apex Diesel Performance & Machine
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04-15-2007, 01:34 AM
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#11
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Name: joefarmer
Title: MR. Supreme Overlord
Status: Not Here
Join Date: Jul 2006
Location: ohio
Member`s Gallery
Posts: 6,137
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You'll drop about a point of compression with a +.020 gasket.
brandon.
__________________
brandon'); DROP TABLE Users;--1948 Dodge 1.5t 12v RH swap | 99 F250 12v RE test rkt | 11 X5 'no soup' | 08 F250 CR RE swap | 05 2500 CR 68 standalone
firepunk.com
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04-15-2007, 11:56 AM
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#12
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Name: Smoking S
Title: Too Much Time
Status: Not Here
Join Date: Nov 2006
Location: California Missouri
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Posts: 621
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How do you figure a compression ratio? I cut 100 thousandths off of a 17.5 to 1 Mahle Piston with the larger bowls and i am using the regular head gasket.
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04-15-2007, 11:49 PM
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#13
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Name: joefarmer
Title: MR. Supreme Overlord
Status: Not Here
Join Date: Jul 2006
Location: ohio
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Posts: 6,137
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The math doesn't seem quite right, but I calculate 13.22 CR assuming a 47cc bowl in the Mahle pistons. Here's the calculation:
http://en.wikipedia.org/wiki/Compression_ratio
brandon.
__________________
brandon'); DROP TABLE Users;--1948 Dodge 1.5t 12v RH swap | 99 F250 12v RE test rkt | 11 X5 'no soup' | 08 F250 CR RE swap | 05 2500 CR 68 standalone
firepunk.com
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04-16-2007, 02:33 AM
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#14
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Name: SuperSonic
Title: El Vato
Status: Not Here
Join Date: May 2006
Location: In a Barn
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Posts: 2,036
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I wouldn't run less than 15.5-16 range if you are going to DD it. It really depends on your setup, and your view on what is streetable.
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COMPDEX
Quote:
Originally Posted by longhorn859
Sometimes I feel like giving up....then I remember I have a lot of motherfukkers to prove wrong.
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04-16-2007, 12:08 PM
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#15
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Name: Tcolesanti
Title: ALL NIGHTER
Status: Not Here
Join Date: Apr 2006
Location: Simi Valley, CA
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Posts: 2,753
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'98-'02 24valves
Stock ETC: 16.7:1
Stock HO: 17.3:1
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04-16-2007, 12:34 PM
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#16
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Name: AsTroSS
Title: problems start @80 psi
Status: Not Here
Join Date: May 2006
Location: Europe
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Posts: 4,327
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Quote:
Originally Posted by Jetpilot
12:1 to 13:1 is a great begining point but starting can be fun.
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Do you guys use something like this ?
its copy/paste from Fleetguard homepage:
Heavy-duty Starting Fluid Systems
We offer both electrically and manually actuated starting fluid systems. All kits provide a measured shot of starting fluid into the diesel engine manifold on demand, which aids ignition at low ambient temperatures. Most kits include the most popular atomizers, which are color-coded for easy installation.
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Ram 2500 '98 QC 12V Cummins 4x4 automatic --->project: T-25
Ram 1500 ‘ 97 QC 12V Cummins conversion 4x4 automatic - ->project: T-15
Superb '21 -TDI 2.0 CR-205hp
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04-16-2007, 12:43 PM
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#17
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Name: jkretzer
Title: MegaCrank
Status: Not Here
Join Date: Jul 2006
Location: hunting, fishing or at work
Member`s Gallery
Posts: 1,444
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i run 15.5:1. i used to have a prob starting when it was cold. turned out to be a mis adjusted gov spring. took the pump to a highly qualified pump shop and they tuned it, now the truck starts without a hiccup.
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04-16-2007, 12:59 PM
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#18
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Name: 99Binder
Title: Diesel Enthusiast
Status: Not Here
Join Date: Sep 2006
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Posts: 202
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sweet, i have been in the ballpark of 16-16.5. im going to call BWD and talk it over some more, thanks agian for the input guys
__________________
Cummin Gitcha Sum
"Im spittin in your face cause im a dominating you" -Hank 3
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04-16-2007, 03:44 PM
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#19
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Name: joefarmer
Title: MR. Supreme Overlord
Status: Not Here
Join Date: Jul 2006
Location: ohio
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Posts: 6,137
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13.32 has been driveable through the winter with the truck plugged in if it sets for more than 5 hours. I also unplugged the IAT sensor so that the Wait to Start function runs the grid heater for 30-45 seconds at a time.
brandon.
__________________
brandon'); DROP TABLE Users;--1948 Dodge 1.5t 12v RH swap | 99 F250 12v RE test rkt | 11 X5 'no soup' | 08 F250 CR RE swap | 05 2500 CR 68 standalone
firepunk.com
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04-16-2007, 04:31 PM
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#20
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Name: Signature600
Title: THA MAN!
Status: Not Here
Join Date: Aug 2006
Location: Jeffersonville, Ohio
Member`s Gallery
Posts: 11,961
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13.32 CR would explain why you can run massive amounts of nitrous and timing without hurting anything but the starting...I wouldn't have thought it would be that low!
Chris
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THANKS TO:
Tim Barber @ TRE Diesel
Jeff Mumau @ Mumau Diesel Service
Rip @ Source Automotive
Don Thuren @ ThurenFab Suspension
Columbus Diesel Supply
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