Go Back   EcoModder Forum > EcoModding > EcoModding Central
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 04-30-2008, 09:57 PM   #1 (permalink)
Master EcoModder
 
Join Date: Apr 2008
Location: Earth
Posts: 303

Pushrod - '02 Chevrolet Cavalier
Thanks: 0
Thanked 8 Times in 4 Posts
Pumping loss test

I'm trying to get a feel for how significant pumping losses are. I wanted to test it out but the roads are a bit busy around here. If you've got a manual transmission and direct throttle cable and want to contribute in the name of science please do!

OK, here we go.

1. Find an empty, relatively flat road.
2. Pick out a landmark like a sign or mailbox.
3. Approach the landmark in a given gear and speed (ex: 40mph in 3rd gear to minimize the effects of wind drag)
4. After you cross the landmark, turn your ignition off.
5. First coast with zero throttle until you stop. Note your distance. The second time around, coast with the accelerator to the floor and note your stopped distance.

Measuring exact distance will be hard, but a GPS or your trip odometer might come in handy for this.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 04-30-2008, 10:39 PM   #2 (permalink)
Liberti
 
LostCause's Avatar
 
Join Date: Feb 2008
Location: California
Posts: 504

Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
Isn't (the intake) pumping loss equal to manifold vacuum? I'm lost as to how your method works, but a vacuum gauge should be quick and simple. If you don't mind, could you explain your reasoning?

- LostCause
  Reply With Quote
Old 04-30-2008, 11:09 PM   #3 (permalink)
Master EcoModder
 
Join Date: Apr 2008
Location: Earth
Posts: 303

Pushrod - '02 Chevrolet Cavalier
Thanks: 0
Thanked 8 Times in 4 Posts
Vacuum is known. Most cars will idle around 4.5 psi, WOT around 14.7 psi and engine brake at about 2psi of MAP. What I'm trying to figure is how these pressures translate into drag at the wheels, and how much I could hope to gain by eliminating or reducing manifold vacuum. The engine should exert a greater braking force with the throttle plate shut than with it open but I'm trying to gauge how significant the effect is.
  Reply With Quote
Old 04-30-2008, 11:20 PM   #4 (permalink)
Giant Moving Eco-Wall
 
DifferentPointofView's Avatar
 
Join Date: Dec 2007
Location: The Dale, IL (or A-Dale)
Posts: 1,120

The Jeep! - '95 Jeep Grand Cherokee ZJ Laredo
90 day: 23.75 mpg (US)

The Caliber - '07 Dodge Caliber R/T
90 day: 30.6 mpg (US)

The 'Scort - '98 Ford Escort LX
Thanks: 0
Thanked 7 Times in 6 Posts
Actually, I thought that most cars idle at 15-20 vacuum, WOT at around vacuum of 5, and decell at 30ish+. I think that your thinking of a car that's turbo-charged, in which case the psi (boost) will go up during accel, and down during decel, opposite with vacuum.
__________________


Yea.. I drive a Jeep and I'm on a fuel economy site, but you just wouldn't understand... "It's a Jeep thing!" *Jeep Wave*

Did I Use Too Many Abbreviations? Here's The Abbreviations List
  Reply With Quote
Old 04-30-2008, 11:32 PM   #5 (permalink)
Master EcoModder
 
Join Date: Apr 2008
Location: Earth
Posts: 303

Pushrod - '02 Chevrolet Cavalier
Thanks: 0
Thanked 8 Times in 4 Posts
Quote:
Actually, I thought that most cars idle at 15-20 vacuum, WOT at around vacuum of 5, and decell at 30ish+. I think that your thinking of a car that's turbo-charged, in which case the psi (boost) will go up during accel, and down during decel, opposite with vacuum.
I was talking about absolute pressure in PSI (how Scanguage displays it), not in/hg. atmospheric= ~14.7 psi, perfect vacuum= 0psi. It's called absolute pressure because it's relative to an absolute vacuum. A typical boost gauge will be relative to atmospheric, which means a total vacuum would be -14.7 psi, atmospheric would be 0, and then boost in positive numbers.
  Reply With Quote
Old 04-30-2008, 11:36 PM   #6 (permalink)
Giant Moving Eco-Wall
 
DifferentPointofView's Avatar
 
Join Date: Dec 2007
Location: The Dale, IL (or A-Dale)
Posts: 1,120

The Jeep! - '95 Jeep Grand Cherokee ZJ Laredo
90 day: 23.75 mpg (US)

The Caliber - '07 Dodge Caliber R/T
90 day: 30.6 mpg (US)

The 'Scort - '98 Ford Escort LX
Thanks: 0
Thanked 7 Times in 6 Posts
oh, sorry, my mistake ^_^"
__________________


Yea.. I drive a Jeep and I'm on a fuel economy site, but you just wouldn't understand... "It's a Jeep thing!" *Jeep Wave*

Did I Use Too Many Abbreviations? Here's The Abbreviations List
  Reply With Quote
Old 04-30-2008, 11:45 PM   #7 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,534

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 57.73 mpg (US)
Thanks: 4,082
Thanked 6,979 Times in 3,614 Posts
Whether it'd reveal anything practical/usable, I think it'd make for an interesting experiment just to see what happens.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 05-01-2008, 12:00 AM   #8 (permalink)
MP$
 
diesel_john's Avatar
 
Join Date: Jan 2008
Location: SW Ohio
Posts: 595
Thanks: 5
Thanked 19 Times in 14 Posts
Send a message via MSN to diesel_john
psia (absolute)

But my concern is with throttle closed during the intake stroke the pressure above the piston is much less than the pressure below the piston, therefore as the piston is pulled down it requires energy from the flywheel and the car.

Next the piston starts back up and the intake valve closes but now the higher pressure below the piston is helping to push it up. So energy is returned to the flywheel or at least cancels some friction. And when the piston gets to the top it has very little air to compress.

Now both valves are closed and the piston starts down the power stroke, again less pressure on the top of the piston, so energy is taken from the flywheel. But this time near the bottom the exhaust valve opens and exhaust gets pulled back into the cylinder. Then the piston comes up and has to push the gas back out the exhaust port. Exhaust closes, intake opens the cycle repeats.

With wide open throttle (ignition off) the cylinder fills requires energy, requires a lot of energy to compress, returns energy during power stroke, and requires energy to push the air out on the exhaust stroke.

It looks like losses might be higher at WOT. But nothing jumps out at me to say that I have isolated pumping losses.
  Reply With Quote
Old 05-01-2008, 12:17 AM   #9 (permalink)
Liberti
 
LostCause's Avatar
 
Join Date: Feb 2008
Location: California
Posts: 504

Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
In any even number cylinder engine, the piston won't compress air on its underside because another piston will be travelling in the opposite direction. The PCV generally exists only for piston blowby.

I still think you can calculate (intake) pumping losses by vacuum alone, but I'm interested in any results.

- LostCause
  Reply With Quote
Old 05-01-2008, 02:07 AM   #10 (permalink)
Banned
 
Join Date: Feb 2008
Location: california
Posts: 1,329
Thanks: 24
Thanked 161 Times in 107 Posts
The simple solution is to apply manifold vacuum to the crankcase.

  Reply With Quote
Reply  Post New Thread




Similar Threads
Thread Thread Starter Forum Replies Last Post
Test: F-150 pickup "cap on" vs. "cap off" @ 60 mph MetroMPG Aerodynamics 17 11-17-2011 02:44 PM
Proposed braking test: comparing tire pressure @ 50 psi vs 35 brucepick EcoModding Central 55 06-11-2011 09:29 PM
Metro/Swift/Firefly Crash Test Videos! Peakster The Lounge 24 11-15-2009 11:36 AM
Done: A-B-A test on rear wheel skirts - Corolla, Camry Hybrid MetroMPG Aerodynamics 11 06-06-2009 04:49 PM
Converting Emissions test to C02 g/km? cfg83 General Efficiency Discussion 3 01-15-2008 03:07 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com