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-   -   How do you Pulse & Glide your diesel vehicle ? (

euromodder 01-14-2011 06:10 PM

How do you Pulse & Glide your diesel vehicle ?
Pulse & Glide is often described as accelerating at less than double the fuel consumption that you'd get at constant speed, then glide with the engine off.

The trouble was, my small displacement diesel simply wouldn't accelerate enough at that rate of fuel consumption to make P & G worthwhile.
Worse still, turning off the engine wasn't an option for me on safety grounds.
End of story ? Not quite !

Some experimenting brought about a different technique :
Accelerating hard in a low gear, then glide in neutral with the engine on.

During the pulse, fuel consumption is really horrible, but fortunately the pulse is short and the glide is long.

That's what works for me, but how do you P & G your diesel ?

UFO 01-14-2011 06:15 PM

That's exactly how to P&G a diesel, as it has no throttle and it's most efficient at the torque peak, usually around 2000 rpm.

I can't do that with my automatic, and as a result, I don't P&G except at low speeds on side streets where I glide to an intersection. At higher speeds I just make sure my torque converter is in lockup (>40mph), and either engine brake to a stop or put the transmission in neutral depending on how far ahead and the slope to the next intersection.

NachtRitter 01-14-2011 07:40 PM

My Jetta TDI pulses nicely (good pull making for relatively quick acceleration) and then glides well (probably because if the weight!). But re-starting when turning the steering wheel is scary because it "over-corrects" and I end up suddenly going several degrees further in the direction I'm turning once the power steering kicks in... so I don't glide with the engine off.

bestclimb 01-15-2011 01:18 AM

85 NA vw diesel, no such thing as fast acceleration. I do accelerate at the maximum throttle setting that I feel an increase in acceleration. Push the pedal down farther and nothing but the amount of noise changes.

I do wish for instant MPG feed back, I suspect I could eek another 5mpg out of it with that alone.

JacobAziza 01-15-2011 01:53 PM

To address the EOC safety factor, I switched to manual steering and electric brake booster.
So all systems work identical engine on or engine off.

I accelerate on the uphills, timed so that the peak speed of the pulse is as close as possible to the apex of the hill.
That way I maximize the use of available torque, and have extra long glides.
On the highway I spend roughly 2/3 - 3/4 of the time with the engine off.

I too would really love some form of instant feedback, unfortunately my truck is pre-computer. It would also be nice to have a transmission with an overdrive.
Maybe someday...

Vekke 01-15-2011 02:11 PM

I use 96% of the throttle (have a stopper under gas pedal)
I also leave the engine on for safety.
Changes should be done at (or close to) peak torgue point.
Use maximum torgue so if 5 gear is too long use 4 to stay on the torgue band. You dont want to fall under best torgue when accelerating. Fifth work best on my diesel with speeds from above 90 km/h, under maybe the best gear is 4, when using P&G. On diesels the acceleration should be as short as possible to see the best results.

I have also tried to push and glide in higher speeds with this technigue:
push to certain speed lets say 130 km/h. Then Glide gear on with slight gas on. I have founded that best results happen if you slow down at rate of 1km/h per 2s. So if you glide to 115 it will take about 30 seconds. I am not sure about results, because my scangauge works only with certain driving technigue where it is at the moment calibrated.

UFO 01-15-2011 04:09 PM


I have been continuously calibrating my SG, lately it's been stable. Amazing how easy it is to mix it up.

COcyclist 01-15-2011 11:05 PM

My glide phase happens at the crest of a hill or on the outskirts of a town with the engine on. The Scanguage shows 250-350 mpg. Not as good as with the engine off but it is less to orchestrate to get the car moving again under power. Sometimes I can anticipate a stoplight and fit a glide in between shifts.

Arragonis 01-16-2011 05:51 AM

I'm refining my technique but what Vekke says seems about right. I glide to the top, or just before allowing the momentum to carry me the last part, and then coast the downhill parts with the engine on (at the moment).

If the hill is quite long then I will pulse a little on the preceding flat and then ease back but stay in gear for the climb just enough to reach the next peak, reducing my losses as much as possible. If the hill is quite long I will aggressively P&G up it too - i.e. quite a sharp pulse. I have one very steep section which I used to lose about 2-3 average MPG in climbing, that loss is down to around 1. Unfortunately this section includes people turning so more often than not I end up having to stop/start on the hill anyway.

If the downhill section is steep enough then I will glide in a high gear to take advantage of the four 9s (9999 MPG) which is more or less like gliding with the engine off. The high gear (I have a 6sp) reduces the engine drag so the glide is still quite long.

I have a section of traffic when it is all stop-start but quite a steep downhill section so I have started cruising slowly with the engine off for that section. On the SG2 it shows me as being at about 45 at the start of this section and still 45 at the end, normally idling will drop this to 35. The downside is that the engine and car are not warm by this point so I have started wearing warm walking socks to keep the feeling in my toes.:cool:

How do people find others reacting to P&G ? I have the technique down reasonably well where passengers are concerned so that they don't feel uncomfortable - the P part is less aggressive. Other drivers can be a pain, one guy I pulsed in front of thought I was starting an acceleration race and decided to try and tailgate until the G part.

Piwoslaw 01-16-2011 06:17 AM

I floor it then glide with engine on. The kill switch is mostly for red lights, but I do use it if I find a nice long, gentle downhill (central Poland is about as hilly as an ice rink;)). EOC is rarely more than 2-4km out of each 1200-1300km tank.

In my case, using the kill switch leaves the PS on, as opposed to keying off.

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