coasting

[rh77]

Originally Posted by skewbe

I just did it on our 97 sw2, I found an "inj" fuse under the hood and put a micro switch inline with it and glued the switch to the auto shifter (index finger friendly position), bada bing.

(ok technically an injector kill switch, even better)

That's a good idea -- are you getting a Check Engine code with the switch?

RH77

[skewbe]

no codes on the saturn from the kill switch yet.

[VetteOwner]

what is pulse and glide? is it just shifting without the clutch?

[cfg83]

VetteOwner -

Originally Posted by VetteOwner

what is pulse and glide? is it just shifting without the clutch?

Pulse and guide as I have seen it described is to :

- Drive (Pulse) up to maybe 5-10 MPH over the speed limit
- Put it in neutral
- Coast (Glide) down to anywhere between 10 and 20 MPH below the speed limit
- Re-engage the engine in appropriate gear for speed
- Repeat.

All of the above is with engine on. Here is the same with engine off :

- Drive (Pulse) up to maybe 5-10 MPH over the speed limit
- Put it in neutral
- Turn key to off position to kill engine
- Turn key to on-position
- Coast (Glide) down to anywhere between 10 and 20 MPH below the speed limit
- Bump-Start engine in appropriate gear for speed (there are other descriptions on this that I won't go into)
- Re-engage the engine in appropriate gear for speed
- Repeat.

If you keep the engine going in neutral, then your are coasting down the road at "idle RPMS". If you turn off the engine when you go into neutral, you are in the magic "infinite MPG" zone, 0 gas @ X MPH. This is where an injector kill switch comes in handy (no key off, on step).

Aerodynamic mods help this because it increases the length of the glide.

I keep the engine going because of my LA traffic density.

PS - I have heard that the Prius does this "for free" at street speeds below 40 MPH. If you drive the Prius right up but not over 40 MPH and let your foot off the accelerator, the car will turn off its engine and coast until you hit the accelerator again. In this way, unmodified (2nd gen only?) Prius' have gotten up to 100 MPG.

Hope this helps,

CarloSW2

[MetroMPG]

FYI, P&G primer: http://www.metrompg.com/posts/pulse-and-glide.htm

[Peakster]

I tried the P&G technique last night on a flat road. With the engine on during the glide, I pulsed to 80km/h and then coasted to 70km/h. After a few miles of doing this, the Scanguage was only reading around 46mpg. (compared to mid 60s mpg if I simply set the cruise to 40mph).

For whatever reason pulse and glide doesn't seem to work for me on flat roads. It honestly doesn't surpise me since my cruise control does a mediocre P&G action (you can feel the pulses when it's on, it's actually kind of annoying) and usually I can get better FE just by maintaining a certain GPH number while traveling.

[MetroMPG]

I have the best P&G results at lower speeds, Peakster. I'm not sure the spread between 70 & 80 is large enough to have any positive effect, ie there's too much wind resistance up there, killing the glide length. Also, with the engine idling, you'll need even longer glide lengths to see any benefit.

[rh77]

Driving at Load can be considered another way to pulse and glide on hills:

An example of "Load"
Level Road @ 50 MPH; 17% Throttle
Start Up-Hill; increase throttle slightly and hold (e.g. 20% TPS)
Hill-Climb; Speed Drops (e.g. 43 MPH)
Hill-Summit; Mimimum Speed @ 40 MPH; start to release throttle for down-hill
Hill-Descent; Speed Increases with less throttle (15%)
Leveling again: Speed @ 55 MPH -- then modulate for conditions

I've modified the cruise-control to do this automatically. Essentially the control has been blocked to draw the cable to no more than 20% TPS. I'll get up to speed and set the target speed for 5+ MPH. Letting-off the accelerator will automatically maintain speed on level and down hills (where the 5+ comes-in handy), and will hold the throttle and decrease speed while driving up-hill.

This helps with long trips, relating to fatigue of maintaining an effecient throttle modulation, and the psychologic effect of inadvertently accelerating or inefficiently powering up a grade. You can let the governor, so to speak, be to "blame" for driving slowly -- and you can relax a bit

RH77

[VetteOwner]

yea.. i cant go 40 in 5th and expect it to go up a hill... it just about dies.
pulse and glide might work for my truck but deff not my chevette... ive put it in neutral before and coasting down hills and any speed above 35 mph its in 4th gear and at hgihway speeds its reved so high its not even funny (at 55mph its at 2800 rpm) hard to catch up to that speed without feeling liek the car just got rearended. sometimes i wish that car was partially computer controlled... seems liek i have to constantly keep adjusting the air fuel mix screw on the carb for it to run right in certian temps.