A case against pulse and glide

[trebuchet03]

I had great success with P&G in my parent's 2006 Altima (2.5L - 4cyl). 40.15mpg versus their best highway mileage of 34.5 (CC). No wind, terrain was flat overall - but I was driving through south Florida hills (highway bridges over surface roads). No EOC - no A/C - tires likely were at 35psi - nighttime driving.

The SG read 40.2 - the on board FE meter said 40.1 IIRC I have a picture of it somewhere

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So, instead of really putting the pedal to the metal - I gave enough gas until the TC locked up, then put down as much throttle as possible to prevent the TC from unlocking.

It's possible to get benefits - you just need to adapt to your transmission logic (as it will vary from car to car)

[landspeed]

Auto gearboxes are VERY bad for accelerating On my car, even cruising at 50mph, uses 25% more fuel if the torque convertor is unlocked, compared to when it is locked. (figures by SuperMID which I recently installed).

I'm looking to see if I can find a way to have a lockup-at-will button, which will get a lot of use in town, but, so far I can't find out how to do it. I know there is a solenoid, but I think it is under a metal cover as part of the gearbox!

[GeekGuyAndy]

I can agree that DWL and coasing when it's beneficial may count as a form of P&G, but the idea that pulsing and gliding for flat terrain jus doesn't work for the 2 autos I drive.

[2TonJellyBean]

Originally Posted by trebuchet03

I had great success with P&G in my parent's 2006 Altima (2.5L - 4cyl). 40.15mpg versus their best highway mileage of 34.5 (CC).

Same average speeds and weight?

[trebuchet03]

Originally Posted by 2TonJellyBean

Same average speeds and weight?

Yep

[2TonJellyBean]

treb, do you think that if the Altima had taller gearing the advantage of using P&G techniques would decrease?

[Zvolen]

I too tried P&G with my auto Saturn and actually did better staying at a constant speed, but like others it could have been me.

[Mr. Pig]

I've tried pulse and glide in my Cavalier which is a 3 speed auto and seen some benefit. My biggest problem is trying not to mess with traffic too much on my way to and from work. Speed limit is 55, so I pulse to 60-65 mph and glide back down to 50 then slowly accelerate back to 55 until I see another chance to pulse. Using this method, I went from an average mpg of 34 on my commute to 37-38 depending on how much I can use it. I wish I had a manual though, as it is a pain to do with auto, and the benefits would be much greater. Anyone want to swap in a metal masher for me?

[trebuchet03]

Originally Posted by 2TonJellyBean

treb, do you think that if the Altima had taller gearing the advantage of using P&G techniques would decrease?

Honestly, I couldn't tell you.... The final drive ratio is 4.425... It could be better, but it's pretty tall be comparison... Although, the thing does have a lot of torque...

I really think it comes down to the transmission shift logic. Which is why there is no one set P&G technique that fits all ATX's. But I'll bet the general rule of thumb is to keep that TCC locked up as much as possible and always accelerate faster than stall speed (which should be really easy on OE torque converters).

[css28]

My experience depends on which car I use.

My commuter is a manual transmission BMW and it thrives on *aggressive* pulse and glide. By that I mean 1/2 throttle surge to 75 mph then glide to 60, rinse and repeat. I'm not shutting off the engine when I do this--just coasting with the clutch in at idle. Good for an extra 2.5 mpg compared to a reasonable DWL at 60 MPH. One reason could be VANOS variable valve timing and variable muffler restriction that both kick in at higher engine speed and power setting. The engine also is apparently much happier when pulling hard than when maintaining speed.

The other vehicle is a Venture with the 3.4L as mentioned above. The good news is that these GM transaxles short shift and lock up their torque converters very willingly if you keep a light touch on the throttle at appropriate speeds. I agree that pulse and glide doesn't seem to work well. The van doesn't seem to glide well at all. On the other hand the final drive is so long-legged, the engine's not much above idle when you're cruising anyhow. The best thing I did was look up the light throttle upshift and lockup speeds so I could feather the accelerator and take advantage of them.