Go Back   EcoModder Forum > EcoModding > DIY / How-to
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 06-25-2013, 09:59 AM   #1 (permalink)
BuickModder
 
Join Date: May 2013
Location: Olathe KS
Posts: 13

99ParkAvenue - '99 Buick Park Avenue
90 day: 25.82 mpg (US)
Thanks: 1
Thanked 4 Times in 2 Posts
Under drive pulley - How much improvement?

Looked for previous discussions and did not see one that answered my question, and that is, how much gain in mpg from using an underdrive pulley? I know it make a little more horsepower, but I was wondering how much gain is there from the reduced accessory drag? 2%?

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 06-25-2013, 10:04 AM   #2 (permalink)
MPGuino Supporter
 
t vago's Avatar
 
Join Date: Oct 2010
Location: Cedar Rapids, IA
Posts: 1,766

The Karen-Mobile - '05 Dodge Magnum SXT
Team Dodge
90 day: 26.72 mpg (US)

Fiat Dakota - '00 Dodge Dakota SLT RWD Quad Cab
90 day: 16.67 mpg (US)

The Red Sled - '01 Dodge Durango SLT 4WD
90 day: 16.96 mpg (US)
Thanks: 799
Thanked 681 Times in 437 Posts
Not a whole lot, if my experiences were any indication. I ran a 20% UDP on my truck last year, and did not see any beneficial increase in fuel economy.
__________________
The Fiat Dakota


The Karen-mobile


The Red Sled
  Reply With Quote
Old 07-29-2013, 03:35 PM   #3 (permalink)
EcoModding Lurker
 
Join Date: Jul 2013
Location: Virginia
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
underdrive pulleys do two things well: prolong accessory life and increase peak hp. anything else is pretty trivial in MOST cases.
__________________
Justin
66 Chevelle - 7.2 @ 98 mph
76 Corvette
93 GMC Typhoon 20 mpg
97 Wrangler Sport 4.0 5spd 21 mpg
98 Chevy Metro 3 cyl 5spd 49 mpg
99 Grand Prix GTP 30 mpg
02 Ford Explorer XLT 21 mpg
04 GMC Sierra Z-71 17 mpg
07 Honda 600RR | 85 Honda 125M 3-wheeler
06 Honda HRC TRX450ER | 03 Honda TRX400EX | 04 Honda Rancher 400

Car Club at Va Tech Founder, President 97-00
Mech Eng 2001
  Reply With Quote
Old 07-29-2013, 04:33 PM   #4 (permalink)
EcoModding Newb
 
redpoint5's Avatar
 
Join Date: Aug 2010
Location: Oregon
Posts: 6,283

Acura TSX - '06 Acura TSX
90 day: 28.39 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 57.64 mpg (US)

Mazda CX-5 - '17 Mazda CX-5 Touring
90 day: 28.88 mpg (US)
Thanks: 2,093
Thanked 2,304 Times in 1,695 Posts
The gain probably wouldn't be more than 1%, which is undetectable with my instrumentation. I'm running a 20% under-drive on the TSX and didn't notice anything.

There is the risk of not having enough alternator output to keep up with electrical demands with the under-driven system. Here is a chart showing the measured voltage of a TSX with a 20% under-driven pulley.

Original post
__________________
Gas and Electric Vehicle Cost of Ownership Calculator







Give me absolute safety, or give me death!
  Reply With Quote
Old 07-29-2013, 04:37 PM   #5 (permalink)
Master EcoModder
 
justme1969's Avatar
 
Join Date: Dec 2012
Location: ff
Posts: 459
Thanks: 59
Thanked 38 Times in 30 Posts
effect is dependant on Idle run time, city/ hiway, day or night,
dont expect a miracle though. all things add up over time.
  Reply With Quote
Old 07-29-2013, 06:30 PM   #6 (permalink)
Hydrogen > EV
 
Join Date: Apr 2012
Location: NW Ohio, United States
Posts: 2,017

Snow White and the 6.2 Dwarfs - '11 Chevrolet Corvette LT2
Last 3: 26.46 mpg (US)

Silver Flea - '05 Honda Insight
90 day: 58.96 mpg (US)
Thanks: 981
Thanked 383 Times in 279 Posts
Quote:
Originally Posted by justme1969 View Post
effect is dependant on Idle run time, city/ hiway, day or night,
dont expect a miracle though. all things add up over time.
100% agree. All things add up, over time.

I don't know this for fact, or if it applies to this situation, but I have read a lot about higher performance vehicles who switch to these for increased performance (as mentioned).

I would think that similar to a lighter drive shaft or wheels, no performance is "gained" but there is less parasitic loss. YMMV, and how it works in your vehicle may not be very valuable, but I couldn't even speculate on that.

It seems as engines become more advanced, upgrading this component is less and less effective.
__________________





Best Tanks:
Mustang - 54.83 mpg (US) at the Green Grand Prix
Insight - 82.91966 mpg (US) over 818.5 miles.
  Reply With Quote
Old 07-29-2013, 08:17 PM   #7 (permalink)
EcoModding Newb
 
redpoint5's Avatar
 
Join Date: Aug 2010
Location: Oregon
Posts: 6,283

Acura TSX - '06 Acura TSX
90 day: 28.39 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 57.64 mpg (US)

Mazda CX-5 - '17 Mazda CX-5 Touring
90 day: 28.88 mpg (US)
Thanks: 2,093
Thanked 2,304 Times in 1,695 Posts
Just as a radiator must be sized for worst case scenarios, the water pump, alternator, AC, and other components are over-sized for typical use. They are sized to deliver adequate performance under severe conditions that are not often encountered.

Just as grill blocking may be appropriate for some applications, under-driving various accessory and cooling systems may be appropriate. The gains from under-driving are miniscule to be sure. The overall load of the alternator, for example, still has to meet the demanded draw. While it may not output as much power when under-driven, it will make up the power difference by running longer. The same can be said of the AC.

The fuel savings really just come down to slightly less frictional loss due to spinning all accessories at a slower rate. In an efficient system with good bearings, this represents a very small gain. There are also tiny gains in fuel efficiency by having lighter weight pulleys that spin up to slower maximum speeds; less energy is wasted in accelerating the rotational mass.

__________________
Gas and Electric Vehicle Cost of Ownership Calculator







Give me absolute safety, or give me death!
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com