Compression Ratio on built motors - Page 2 - Competition Diesel.Com

*bdp* · 04-16-2007, 07:30 PM

A low cr like 12 or 13:1 will need somthing to make up for the loss like 100+psi of boost or lots of nitrous. The lower comp will help with pressures but will make the engine less effecient IMO without alot of boost to bring back the ratio on the top end. I have seen engines like this that never stop white smoking with about 12:1 cr and a single turbo. Even at WOT at the end of the pullin track its got a white/dark grey mix in the smoke, to me thats just not gonna make good power.

I would keep it up in the 16:1 range for a street driver, just IMO.

Graphic Man · 04-17-2007, 07:02 AM

CC the top of a piston, gasket thickness and deck height and it will soon tell you what you will have for C/R

Scott

fordcummins · 01-20-2010, 08:26 PM

mine are 15.1 and its a big big pain in the a$$ to start when its cold

markt · 01-22-2010, 07:29 PM

What temperature are y'all calling "cold"?

Crawler · 01-30-2010, 11:42 AM

Holly revived thread Batman!

daithi2 · 01-30-2010, 12:57 PM

PRINCETON_JAKE · 01-30-2010, 05:41 PM

How low of compression ratio can you go on a diesel? I have a friend with a pulling truck that says the c.r. of his truck is under 9 to 1. it is a heavily built motor that requires starting fluid unless its 100 degrees out side.

Jim Fulmer · 01-30-2010, 06:36 PM

Quote:

Originally Posted by Crawler

Holly revived thread Batman!

Were have you been hiding at?

Jim

*COMP461* · 01-31-2010, 03:16 PM

There are many variables, I'm going the other way on a high Dollar 2.6 build up. Around 17.5 static, but there is a lot more to it, such as cam timing and intake runners. You also can run a dramatic amount more compression with a Common rail engine. The common rail has the ability to limit power as the engine goes through the destructive peak torque part of the power curve.
I am adding 20 degrees to the intake-closing event
The cam will have a 115 intake lobe center line, and a 125 lobe separation angle, along with a .450 lobe lift

99Binder · 02-07-2010, 09:07 AM

i know more tractor pullers (at the 3.0 inch) are sticking with a closer to stock compression ratio

*Dalpilot* · 02-07-2010, 10:52 AM

I'm right at 16.5 : 1.

BigDamnCummins · 02-09-2010, 09:58 PM

Somewhere in the 18 to 19:1 range for my cr!

BigDamnCummins · 02-18-2010, 10:27 PM

18.6:1 to be exact, and somewhere between 850 and 900rwhp with a 2.6 inlet.

pwrstrokenstang · 02-19-2010, 05:50 PM

my new motor will be 15:1.

CR785 · 02-19-2010, 09:53 PM

I dont know why some people would want the 12 13 or 14:1 for dd vehicles, i run 12:1 in my 3.0 truck, i struggle each and everytime to start that thing, plus a street ruck isnt going to need that much relief, cause you arent going to be making that much power. I would go no lower that 15:1 on the street, and at that i would think that cold weather starting would be hard sometimes, i think you are on the right track, being aroun 16 16.5:1.

BigDamnCummins · 02-20-2010, 10:36 AM

Is 16.5:1 to low for a motor that runs down the track at 3300rpm?

*COMP461* · 02-20-2010, 04:52 PM

you need to turn it harder the 3300

smokin1997 · 02-20-2010, 05:04 PM

around 14.5:1 on a 12v 3.0 puller
let it sit for a week, or if it gets below 60* overnight, it needs a little assistance to start.

daithi2 · 02-20-2010, 05:57 PM

15/1 on my 12v with 13mm and II race twins. its damn hard to start in cold weather no heater grid and no fuel warmer. It hazes no matter what.

dieseljunky2500 · 02-20-2010, 06:10 PM

compression ratio in hot motors really varies with boost. i am running 40 lbs on stock compression. i would start to lower after 55 to 60 lbs, but not a whole lot.

04-16-2007, 07:30 PM	#21
bdp Name: bdp Title: beans diesel performance Status: Not Here Join Date: Apr 2006 Member`s Gallery Posts: 1,730	A low cr like 12 or 13:1 will need somthing to make up for the loss like 100+psi of boost or lots of nitrous. The lower comp will help with pressures but will make the engine less effecient IMO without alot of boost to bring back the ratio on the top end. I have seen engines like this that never stop white smoking with about 12:1 cr and a single turbo. Even at WOT at the end of the pullin track its got a white/dark grey mix in the smoke, to me thats just not gonna make good power. I would keep it up in the 16:1 range for a street driver, just IMO. __________________ www.beansdieselperformance.com The Smokin' Hot Hooker- 2002 F350-6.7 CRD Sponsored by South Bend Clutch, Woodruff Diesel, Floor It Diesel bdp Drag Truck- 81 C10 5.9 bdp built- Sponsors-Arrow Engine Machine, BTS Transmissions, Snow Performance, NX, Carrilo Rods, Mahle Pistons

04-17-2007, 07:02 AM	#22
Graphic Man Name: Graphic Man Title: Too Much Time Status: Not Here Join Date: Aug 2006 Location: Mississauga Ont. canada Member`s Gallery Posts: 963	CC the top of a piston, gasket thickness and deck height and it will soon tell you what you will have for C/R Scott __________________ 08 Mega cab SOLD01 Ram sport 4X4, Monster VP , some big injectors, full billet DTT, and big twins etc. etc.

01-30-2010, 11:42 AM	#25
Crawler Name: Crawler Title: Press the BIG RED button. Status: Not Here Join Date: Apr 2006 Location: NE Texas Member`s Gallery Posts: 837	Holly revived thread Batman! __________________ EIKON Diesel-Where Diesels Become ICONS 95 Dodge-1500 Back Half 4-link 12V 2020 Duramax 2500 HPTuners 2015 Duramax 2500 EFI Live 2017 Powerstroke 3500 EZ Lynk

01-30-2010, 05:41 PM	#27
PRINCETON_JAKE Name: PRINCETON_JAKE Title: Too Much Time Status: Not Here Join Date: Jan 2010 Location: Princeton Minnesota Member`s Gallery Posts: 1,125	How low of compression ratio can you go on a diesel? I have a friend with a pulling truck that says the c.r. of his truck is under 9 to 1. it is a heavily built motor that requires starting fluid unless its 100 degrees out side. __________________ silver 2006 ram 2500 4x4, crew cab short box, 48RE auto with "stuff" done, 5.9 with more "stuff" done

01-31-2010, 03:16 PM	#29
COMP461 Name: COMP461 Title: Comp Diesel Sponsor Status: Not Here Join Date: Apr 2006 Location: Aledo Member`s Gallery Posts: 4,009	There are many variables, I'm going the other way on a high Dollar 2.6 build up. Around 17.5 static, but there is a lot more to it, such as cam timing and intake runners. You also can run a dramatic amount more compression with a Common rail engine. The common rail has the ability to limit power as the engine goes through the destructive peak torque part of the power curve. I am adding 20 degrees to the intake-closing event The cam will have a 115 intake lobe center line, and a 125 lobe separation angle, along with a .450 lobe lift __________________ Greg Hogue Comp461 race page Edelbrock Nitrous Outlet MaxSpool Engineering Exergy Performance

01-20-2010, 08:26 PM	#23
fordcummins Name: fordcummins Title: Showoff Status: Not Here Join Date: Jun 2006 Member`s Gallery Posts: 981	mine are 15.1 and its a big big pain in the a$$ to start when its cold

01-22-2010, 07:29 PM	#24
markt Name: markt Title: Rookie Status: Not Here Join Date: Jul 2006 Member`s Gallery Posts: 26	What temperature are y'all calling "cold"?

01-30-2010, 12:57 PM	#26
daithi2 Name: daithi2 Title: Nevermore Status: Not Here Join Date: Aug 2008 Location: Amarillo, Tx Member`s Gallery Posts: 607

02-07-2010, 09:07 AM	#30
99Binder Name: 99Binder Title: Diesel Enthusiast Status: Not Here Join Date: Sep 2006 Member`s Gallery Posts: 202	i know more tractor pullers (at the 3.0 inch) are sticking with a closer to stock compression ratio __________________ Cummin Gitcha Sum "Im spittin in your face cause im a dominating you" -Hank 3

02-07-2010, 10:52 AM	#31
Dalpilot Name: Dalpilot Title: Joe Nobody! Status: Not Here Join Date: Apr 2006 Location: Austin, Texas Member`s Gallery Posts: 11,373	I'm right at 16.5 : 1. __________________ 2017 White f-250 COMPETITIONDIESEL.COM Bringing the best together

02-09-2010, 09:58 PM	#32
BigDamnCummins Name: BigDamnCummins Title: Diesel Enthusiast Status: Not Here Join Date: Jan 2010 Member`s Gallery Posts: 110	Somewhere in the 18 to 19:1 range for my cr!

02-18-2010, 10:27 PM	#33
BigDamnCummins Name: BigDamnCummins Title: Diesel Enthusiast Status: Not Here Join Date: Jan 2010 Member`s Gallery Posts: 110	18.6:1 to be exact, and somewhere between 850 and 900rwhp with a 2.6 inlet.

02-19-2010, 05:50 PM	#34
pwrstrokenstang Name: pwrstrokenstang Title: oil burner pulling team Status: Not Here Join Date: Mar 2009 Location: staunton, va Member`s Gallery Posts: 355	my new motor will be 15:1. __________________ '96 F-250- just another 2.6 7.3l turd with way too much money under the hood.

02-19-2010, 09:53 PM	#35
CR785 Name: CR785 Title: Too Much Time Status: Not Here Join Date: Jan 2008 Member`s Gallery Posts: 302	I dont know why some people would want the 12 13 or 14:1 for dd vehicles, i run 12:1 in my 3.0 truck, i struggle each and everytime to start that thing, plus a street ruck isnt going to need that much relief, cause you arent going to be making that much power. I would go no lower that 15:1 on the street, and at that i would think that cold weather starting would be hard sometimes, i think you are on the right track, being aroun 16 16.5:1.

02-20-2010, 10:36 AM	#36
BigDamnCummins Name: BigDamnCummins Title: Diesel Enthusiast Status: Not Here Join Date: Jan 2010 Member`s Gallery Posts: 110	Is 16.5:1 to low for a motor that runs down the track at 3300rpm?

02-20-2010, 04:52 PM	#37
COMP461 Name: COMP461 Title: Comp Diesel Sponsor Status: Not Here Join Date: Apr 2006 Location: Aledo Member`s Gallery Posts: 4,009	you need to turn it harder the 3300 __________________ Greg Hogue Comp461 race page Edelbrock Nitrous Outlet MaxSpool Engineering Exergy Performance

02-20-2010, 05:04 PM	#38
smokin1997 Name: smokin1997 Title: I Know Nothing Status: Not Here Join Date: Dec 2007 Location: Idaho Member`s Gallery Posts: 899	around 14.5:1 on a 12v 3.0 puller let it sit for a week, or if it gets below 60* overnight, it needs a little assistance to start. __________________ '12 Dodge 6.7 g56. Deleted and tuned 1997 Dodge Super Street puller "Never Ending" SOLD TurboPerformanceProducts.com

02-20-2010, 05:57 PM	#39
daithi2 Name: daithi2 Title: Nevermore Status: Not Here Join Date: Aug 2008 Location: Amarillo, Tx Member`s Gallery Posts: 607	15/1 on my 12v with 13mm and II race twins. its damn hard to start in cold weather no heater grid and no fuel warmer. It hazes no matter what.

02-20-2010, 06:10 PM	#40
dieseljunky2500 Name: dieseljunky2500 Title: Rookie Status: Not Here Join Date: Feb 2010 Member`s Gallery Posts: 5	compression ratio in hot motors really varies with boost. i am running 40 lbs on stock compression. i would start to lower after 55 to 60 lbs, but not a whole lot.