what would it take to reduce RPM on highway? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
Home Forum Market Place Garage Lounge (0) Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > GM Diesel Engines > Duramax Second Generation: 2004.5-2005 (LLY)
Register FAQ Forum Rules My Replies My Threads Mark Forums Read Auto EscrowAuto LoansInsurance

DieselPlace.com is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Closed Thread
 
LinkBack Thread Tools
Old 07-26-2008, 08:57 AM   #1 (permalink)
sadolph
Diesel Technician
 
Join Date: Jan 2005
Posts: 103
iTrader Score: 0 reviews

what would it take to reduce RPM on highway?

Hi,

I'm thinking about engine RPMs at highway speed. I have a 5 speed allison tranny in my truck.

I'm spinning 2000 RPM at 60, and 2300 ish at 75 (or whatever).

Seems my mileage sucks and I think it has more to do with engine speed. In other words, I would see a big change in mileage if I was spinning 2000 RMP at 75 and 1700 at 60.

Does anyone know if it is possible to change ratios?

What is the best way to do it?

thanks.
__________________
2004.5 2500HD CC 4x4 shortbox + Raider cap
Bone stock
Offline  
Quick reply to this message
Sponsored Links
Advertisement
 
Old 07-26-2008, 09:14 AM   #2 (permalink)
PoPsRacing
Diesel Specialist
 
PoPsRacing's Avatar
 
Join Date: Mar 2007
Location: Kingsville Ohio
Posts: 837
iTrader Score: 0 reviews

Suncoast sells a 6 speed conversion valve body. Check it out.
http://www.suncoastconverters.com/gmc/gm_products.html
__________________
*2005 Duramax 2500HD CC/SB Sport Red Met. 4X4 111,000 miles
* Allison 1000 5sp Auto
* Quadzilla S2
* ISSPRO Gauges w/pillar pod - pyro/boost
* Silverline 4" SS turbo back - cat deleted - EGR blocked, No finger - PCV Re-route - MP Ported - Resonator plugged
* 285/75R/16 Uniroyal Laredo AWT's - Cognito Idl/Pit Braces & HD Tie Rods
* Garmin GPS installed
* 24' Waderer Wagon Toy Hauler - Honda Toys - Ride Red- Proud Member of the ATVA

*IF YOUR GONNA BE A BEAR - - BE A GRIZZLY*

Last edited by PoPsRacing; 07-26-2008 at 09:15 AM.
Offline   Quick reply to this message
Old 07-26-2008, 10:05 AM   #3 (permalink)
Boge
Diesel Technician
 
Boge's Avatar
 
Join Date: Oct 2007
Location: NY
Posts: 270
iTrader Score: 0 reviews

Anyone running this kit??
__________________
"Give Me Liberty Or Give Me Death"
-Patrick Henry, March 23, 1775


Yes .. I'm back
Offline   Quick reply to this message
Old 07-26-2008, 10:07 AM   #4 (permalink)
colnago
Diesel Specialist
 
colnago's Avatar
 
Join Date: Jul 2005
Location: Ridgecrest, CA (but it's a dry heat ...)
Posts: 538
iTrader Score: 0 reviews

Or taller tires. Just remember that your air/wind resistance goes up as your speed goes up, so dropping the RPMs might not help as much as you think. Also, check the Duramax Third and Fourth Generation areas of the forum. Since those engines came with the six-speed Ally, you might find some interesting reading in there about whether it's worth upgrading or not.

Joseph
__________________
2005 Chevy Silverado 2500HD, "The Beast"
2WD, CC/SB, LLY, D/A, Line-X Liner, Prodigy Brake Controller, SNUGTOP Super Sport Shell
TxC CAI, Partial Nose Shroud, Amsoil Oil Bypass, Chevy 3" Air Dam
Chevy 17" NBS Alloy Rims with 265/70R17 BFG Rugged Trails
Cognito Uni-Ball Upper Control Arms, Leveled with Cognito Shock Extenders and Rancho RS9000X Shocks

Sold to make room for an SUV!!!
Offline   Quick reply to this message
Old 07-26-2008, 11:21 AM   #5 (permalink)
chevman
Diesel Specialist
 
chevman's Avatar
 
Join Date: Oct 2003
Location: Wenatchee,Wash
Posts: 578
iTrader Score: 0 reviews

2000 rpms at 60 seems to be odd to me. 3.73 is the only read gear so are the tires smaller than stock?
chevman 05 2wd duramax 3500 CC dually
__________________
Larry Barnhart
2005 3500 2wd CC duramax dually
2001 35 ft avalon alpenlite
easyrider/reese airhitch
trailair center point suspension
scanguageII
prodigy
KHS 55 gal inbed fuel tank
Garmin 2720 GPS
TD-EOC
Induction Air Overhaul
Offline   Quick reply to this message
Old 07-26-2008, 11:25 AM   #6 (permalink)
PoPsRacing
Diesel Specialist
 
PoPsRacing's Avatar
 
Join Date: Mar 2007
Location: Kingsville Ohio
Posts: 837
iTrader Score: 0 reviews

Quote:
Originally Posted by chevman View Post
2000 rpms at 60 seems to be odd to me. 3.73 is the only read gear so are the tires smaller than stock?
chevman 05 2wd duramax 3500 CC dually
I was thinking the same thing, At 2000 rpm I running 72 mph.
__________________
*2005 Duramax 2500HD CC/SB Sport Red Met. 4X4 111,000 miles
* Allison 1000 5sp Auto
* Quadzilla S2
* ISSPRO Gauges w/pillar pod - pyro/boost
* Silverline 4" SS turbo back - cat deleted - EGR blocked, No finger - PCV Re-route - MP Ported - Resonator plugged
* 285/75R/16 Uniroyal Laredo AWT's - Cognito Idl/Pit Braces & HD Tie Rods
* Garmin GPS installed
* 24' Waderer Wagon Toy Hauler - Honda Toys - Ride Red- Proud Member of the ATVA

*IF YOUR GONNA BE A BEAR - - BE A GRIZZLY*

Last edited by PoPsRacing; 07-26-2008 at 11:25 AM.
Offline   Quick reply to this message
Old 07-26-2008, 12:11 PM   #7 (permalink)
Diesel_Day_Dreamin
Diesel Master
 
Diesel_Day_Dreamin's Avatar
 
Join Date: Feb 2005
Location: Northcentral Maryland
Posts: 2,658
iTrader Score: 1 reviews

DelMarVa Diesel Club Member

I'm guessing your ultimate goal here is to get the best milage you can...

Not to get off topic here, I'll share my mileage gaining trick.

I have found that using the DIC fuel mileage setting, you can ''teach'' yourself to get the best mileage by practicing good acceleration/driving habbits. Using my steering wheel controls, I will reset the MPG calculator at a traffic light or while driving. as you are sitting still, it is ''0''. when you accelerate, the more aggresive you are on the throttle, the slower it is to come up from ''0''. While driving, you will notice that pressing the pedal as lightly as you can to maintain speed keeps your numbers high. I have found myself to not be ''pedal to the floor'' like I used to do (it's fun every now and again). Let the traffic accelerate and de-accelerate while you maintain a steady rate. Everytime you mash your pedal to keep up, only to be on your brakes again, it's wasting your fuel (numbers decrease on the DIC). I have also found that while ''cold'' (cold meaning below normal operating temperature), you are only getting about 12 to 15 mpg until operating temperature is met (approx. 180). Even on a 90 day, I will start my truck and idle it a few minutes before leaving for work/home. I can get 19 to 21 mpg commuting to work. I have seen as high as 22 mpg highway (all highway on a long trip) empty. These are hand calculated MPGs (dividing miles driven by gallons taken to fill back up).

On a side note... My friend and I went on a 480 mile trip. He has a stock extended cab long bed 2006 duramax ''6'' speed and mine a 2005 crew shortbed duramax ''5'' speed with tuner(s) set on economy. He has a 35 gallon fuel tank and mine is a 26 gallon. He was pulling over the same time I needed to for filling up. I was burning 9 gallons less per tank full. He was behind me the whole trip sucking up my wind breakage! Yes tuners help out, but by that much? I'm not convinced on the 6 speed conversion for the money they want for it. I'm doing just fine.
__________________
2005 GMC Sierra 2500HD D/A CC SB 4x4 SLE

Last edited by Diesel_Day_Dreamin; 07-26-2008 at 12:26 PM.
Offline   Quick reply to this message
Old 07-26-2008, 12:20 PM   #8 (permalink)
cuffnup
Diesel Master
 
cuffnup's Avatar
 
Join Date: Apr 2006
Location: Olney, IL
Posts: 1,649
iTrader Score: 0 reviews
Send a message via Yahoo to cuffnup

Illinois Diesel Power (IDP) Member

Midwest Smokers Member

i gained 2 mpg switching to schaeffers...on paper
__________________
2006 CHEVY SILVERADO ..LLY...EXT. CAB 4x4
EFI LIVE (Idaho Rob) DSP 5 Switch
Revmax Valve Body
Diamond Eye 4" Exhaust (Meyer Performance)
TIMBREN SUSPENSION KIT
SWITCHED ALL FLUIDS TO AMSOIL
ONYX INDUSTRIAL SPRAY IN BEDLINER
MASTERCRAFT CT'S....265'S,
PRODIGY BRAKE CONTROLLER
PCV Reroute (Merchant Automotive)
Blocker Plate (Merchant Automotive)
Allison Deep Pan w/ Suncoast Filter Lock (Merchant Auto)
ILLINOIS DIESEL POWER MEMBER #2
Midwest Smokers Member
DieselPlace.com Lifetime Member
Offline   Quick reply to this message
Old 07-26-2008, 12:32 PM   #9 (permalink)
Diesel_Day_Dreamin
Diesel Master
 
Diesel_Day_Dreamin's Avatar
 
Join Date: Feb 2005
Location: Northcentral Maryland
Posts: 2,658
iTrader Score: 1 reviews

DelMarVa Diesel Club Member

Quote:
Originally Posted by cuffnup View Post
i gained 2 mpg switching to schaeffers...on paper
Meaning theoretical or actual? That's a big increase for just an additive.
__________________
2005 GMC Sierra 2500HD D/A CC SB 4x4 SLE
Offline   Quick reply to this message
Old 07-27-2008, 05:11 PM   #10 (permalink)
SLT223
Diesel Master
 
Join Date: Sep 2005
Location: CT
Posts: 1,242
iTrader Score: 0 reviews

Bmping up ignition timing does get noticable gains. At 60mph I went from 21 mpg to 24 mpg on a stock tune with GM's timing tsble C with an otherwise stock 2005 LLY tune.
__________________
'05 D/A 2500HD Extended Cab LT, Black
Stock
Offline   Quick reply to this message
Sponsored Links
Advertisement
 
Closed Thread

Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Reduce Turbo Lag..What can I do ChevyRidinHighh Fuel System, Air, Exhaust, & Emissions Upgrades 14 07-29-2011 08:15 PM
Reduce Engine Power mnmleitch Duramax Fourth Generation: 2007.5-2010 (LMM) 6 12-30-2009 09:43 PM
Tuning to Reduce EGT's? Mitco39 EFILive Tuning Software 24 08-29-2009 12:25 PM
Am I doing this right to reduce MAF limitations? SLT223 EFILive Tuning Software 14 10-02-2008 11:07 PM


All times are GMT -4. The time now is 08:51 AM.


Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide

SEO by vBSEO 3.6.0