Go Back   EcoModder Forum > EcoModding > Hypermiling / EcoDriver's Ed
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 08-15-2012, 04:51 PM   #1 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
How To maintain brakes while engine off coasting

i have been reading up on brakes today and came to a realization that there is a technique to maintain your brake booster pressure while coasting, engine off.

My tdi uses a mechanical vacuum pump that runs off the camshaft, when in neutral with the engine off, the camshaft is not turning, put it in gear and cam turns the vacuum pump, keeping the brake booster loaded.
My theory is that coasting with the key in off ACC on position can provide a unlimited amount of brake use.

In short by putting it in gear before braking i will maintain my brake boosters vacuum without starting the motor.

I am going to the lake later, a 20 mile country highway with lots of hills for me to try this ignition off brake in gear theory of mine.

__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________




Last edited by ecomodded; 08-15-2012 at 05:11 PM..
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 08-15-2012, 05:02 PM   #2 (permalink)
UFO
Master EcoModder
 
UFO's Avatar
 
Join Date: Sep 2010
Location: Denver, CO
Posts: 1,300

Colorado - '17 Chevrolet Colorado 4x4 LT
90 day: 23.07 mpg (US)
Thanks: 315
Thanked 178 Times in 138 Posts
That should work for any manual transmission vehicle, as brake vacuum for gassers can be generated with engine braking.
__________________
I'm not coasting, I'm shifting slowly.
  Reply With Quote
Old 08-15-2012, 05:02 PM   #3 (permalink)
Hypermiler
 
PaleMelanesian's Avatar
 
Join Date: Dec 2007
Location: Texas
Posts: 2,314

PaleCivic (retired) - '96 Honda Civic DX Sedan
90 day: 69.2 mpg (US)

PaleFit - '09 Honda Fit Sport
Team Honda
Wagons
90 day: 44.06 mpg (US)
Thanks: 605
Thanked 422 Times in 277 Posts
I'd go ahead and key back to the "on" position. There's a bunch of electronic stuff you might like to have functioning. Things like ABS and airbags.

I preserve brakes by not using them. You get 3-4 pumps before the vacuum runs out. If I use 2+ pumps, I'll bump-start for a second to restore vacuum, then key off again. That way I have full boost if an emergency appears.
__________________



11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
  Reply With Quote
Old 08-15-2012, 05:07 PM   #4 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
I am thinking stopping with full brakes may prevent the use of the air bags.

I am actually excited about this new technique to try out, it will save ME a LOT of fuel and increase my coasting safety.
I was originally looking into a electric vacuum pump such as the ones used on some VW passats & jettas or this Volvo brake vacuum pump below. I may not need to spend a dime to get the same result.
Attached Thumbnails
Click image for larger version

Name:	Volvo S60 Vacuum Pump.jpg
Views:	40
Size:	33.2 KB
ID:	11338  
__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________




Last edited by ecomodded; 08-15-2012 at 05:29 PM..
  Reply With Quote
Old 08-15-2012, 05:26 PM   #5 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,541

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
Thanks: 1,056
Thanked 630 Times in 396 Posts
A diesel has to have a mechanical pump, which is almost always actuated when the engine is turning. So, if you coast in gear, you can restore your vacuum, but you lose some momentum (energy) in the process. If the 2-4 brake pumps' worth of vacuum in the system isn't enough for you, then I can see three options:
  1. Make a reservoir out of a PVC pipe, increasing your vacuum system's volume by 1-3 liters.
  2. Add a small electrical pump to replenish vacuum while EOC.
  3. Replace your mechanical pump with an electrical one, like from an EV. This will reduce the load on your engine since the electrical pump will turn on only when needed.

BTW: Make an engine kill switch, it should be much better and safer than keying off. In my turbodiesel's case the engine kill switch keeps the power steering on and doesn't reset the computer. It may also keep the airbags and other important stuff on.
__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell

Piwoslaw's Peugeot 307sw modding thread

  Reply With Quote
Old 08-15-2012, 05:39 PM   #6 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
I am thinking technique alone will give me the desired results, which is full brakes while approaching stop lights or vehicles or coasting down hills.
A electric booster was my first thought until i realized i could just put the car in gear and turn the vacuum pump.

Piwoslaw do you have a thread on your engine kill switch mod.
I should be using a killl switch, the key switch is a distraction and a pain to do.
__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________




Last edited by ecomodded; 08-15-2012 at 05:46 PM..
  Reply With Quote
Old 08-15-2012, 05:57 PM   #7 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,541

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
Thanks: 1,056
Thanked 630 Times in 396 Posts
I don't think I started a thread on the details. I just found the crankshaft position sensor and put it on a relay which is actuated by pushing a button in the dash. I get a beep and warning about low oil pressure, and the ventilation fan stops, but other than that everything seems to be fine.
I just can't EOC for longer than 30 minutes at a time or the computer will go into economy mode
__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell

Piwoslaw's Peugeot 307sw modding thread

  Reply With Quote
Old 08-17-2012, 02:22 AM   #8 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
The brakes maintained there effectiveness without losing vacuum, while engine off coasting / in gear for braking.

I feel like the kill switch really is necessary, It is risky to be fooling around with the keys while driving plus there is a possibility of turning the ignition key to far, unknowingly locking the steering wheel.
I do not engine off coast every chance i get now because of brake issues and the key issue.
With a kill switch & in gear braking i could engine off coast in a lot more circumstances, such as shorter coasts with the convenience of the kill switch and steeper hills with the in gear braking ability.

Piwoslaw i am going to look for the crankshaft position sensor. What does the motor think happened when the switch is opened ? it sounds unconventional but effective. I like it.
__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________




Last edited by ecomodded; 08-17-2012 at 02:30 AM..
  Reply With Quote
Old 08-17-2012, 12:31 PM   #9 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: Tampa, FL
Posts: 1,561

Volt, gas only - '12 Chevrolet Volt Premium
90 day: 38.02 mpg (US)

Volt, electric only - '12 Chevrolet Volt Premium
90 day: 132.26 mpg (US)

Yukon Denali Hybrid - '12 GMC Yukon Denali Hybrid
90 day: 21.48 mpg (US)
Thanks: 169
Thanked 345 Times in 240 Posts
Why can't you just go to the junk yard and get a vacuum canister? More than one if you need more vacuum.
__________________




  Reply With Quote
Old 08-17-2012, 01:34 PM   #10 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
I feel if any parts will be bought it would be the electric vacuum pump as the vacuum tank is not unlimited, i want a unlimited amount of braking so the 1 to 10 km steep hills i frequent can be safely engine off coasted.

I live in a mountainous region with many opportunities to coast, One is a 10 km coast from the top of the Pass leading to my city.

__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________




Last edited by ecomodded; 08-17-2012 at 01:47 PM..
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com