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Old 06-04-2013, 05:12 PM   #1 (permalink)
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How much can I save from P&G

Ever since I have my gauge set up and tuned, I have been trying to find out how P&G will benefit me. I read on Wiki that P&G will greatly benefit city driving, which is all I do but I am struggling to archive the result.

I have an Automatic, 3500lb car with relatively small 170hp engine (Accord). The car eats up so much fuel when accelerating at 70-80% load but still takes quite a while to get up to 35mph because it is heavy and it FREAKING slow down so fast when in gear that I have to pulse every ten seconds.

Yet, I find that engaging cruise at 35mph gives me better MPG than anything my foot can perform. I swear that if I just hold my foot still at 35mph, it will use 4L/h and the second I enenge cruise, it drops to 3.5L/h. Crazy!

So my question is, do P&G always give you better result than slow accelerate and cruise?

Would medium accelerating is still better than turtle acceleration?

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Old 06-04-2013, 05:46 PM   #2 (permalink)
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It's all vehicle/user/route dependent on if pulse and glide works. The reason it works so well for many is that they engine off coast in manuals trannys.

Considering that your in an automatic you need to make sure that the torque converter is being used on your pulse and then if you choose to leave your engine on the decision to be made is whether neutral or in gear gliding (DFCO) is more beneficial. Pulse and glide works due to the high torque/low rpm pulsing.

Ex. My car benefits from p&g when the speed limit is 55+ because DFCO does not kick in until above 45mph. otherwise it is better for me to drive with load.

Make sure you have some sort of mpg gauge (Scangauge/Ultragauge/mpguino), to measure which would be the best technique
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Old 06-04-2013, 06:30 PM   #3 (permalink)
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I find that 70 to 80% load acceleration doesn't work for me either, same problem using a lot of fuel to get up speed.The best technique for me in the city is to time traffic lights. Key off at red lights is also quite effective when the weather is cooler. Try different things you will find what works best for you.
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Old 06-04-2013, 06:43 PM   #4 (permalink)
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I agree with gealii, pulse and glide is mainly a manual tranny technique.
In my 5spd car i can pulse then eoc for a long time, then bump start and rev match into gear. With an auto the coast down time in gear is usually too small to give benefit and with every auto ive tried it doesn't feel right to toggle between drive and N.
I would just do what seems to work best
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Old 06-04-2013, 06:48 PM   #5 (permalink)
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Quote:
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I agree with gealii, pulse and glide is mainly a manual tranny technique.
In my 5spd car i can pulse then eoc for a long time, then bump start and rev match into gear. With an auto the coast down time in gear is usually too small to give benefit and with every auto ive tried it doesn't feel right to toggle between drive and N.
I would just do what seems to work best
you should try a GM car. our trannys automatically shift into neutral (If in D)when in gear coasting so we get the benefit of neutral gliding with dfco. Yes p&g is much more efficient in manuals, but p&g can work in autos
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Old 06-05-2013, 10:39 AM   #6 (permalink)
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Another reason P&G isn't ideal in automatics is the torque converter. What you want for P&G is high engine load, but low engine rpms. In an automatic, if you want high engine load you can't get low rpms, you get high rpms. High load also creates more heat in the torque converter and you loose some efficiency there too. When I drive an automatic I accelerate moderately fast while trying to keep engine rpms fairly low. You can learn to trick the car into shifting by letting off the gas a bit, waiting for it to shift, then reapplying as much as you can without downshifting too.
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Old 06-05-2013, 01:35 PM   #7 (permalink)
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Quote:
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.....What you want for P&G is high engine load, but low engine rpms.....
I agree.

With the Insight, I'm stepping hard on the throttle at 1500 rpm. I never let it get over 2000 rpm, if I want to get really good mileage.

I don't know if the V-Tec system works, because I never run the engine that high !!

With an outside temperature of 60F and a slight sidewind, the dash was showing 122 mpg when the driveway appeared. Lot's of EOC.

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Old 06-05-2013, 03:19 PM   #8 (permalink)
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From what I know about Honda automatics (odyssey), P&G really only works when you can lock it in top gear and hold it for the pulse. That means you must be above 45 mph, probably more since you're loading it and that makes it want to downshift. I only bother p&g'ing at > 55 mph. Better to focus on low rpm below that point.

Oh. WAIT. You're trying to "glide" in gear? NO. Pop it into N or it's going to engine-brake you down in no time at all. You will get worse mileage doing "Pulse and engine-brake" than steady speed.
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Old 07-13-2013, 01:06 PM   #9 (permalink)
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Quote:
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From what I know about Honda automatics (odyssey), P&G really only works when you can lock it in top gear and hold it for the pulse. That means you must be above 45 mph, probably more since you're loading it and that makes it want to downshift. I only bother p&g'ing at > 55 mph. Better to focus on low rpm below that point.

Oh. WAIT. You're trying to "glide" in gear? NO. Pop it into N or it's going to engine-brake you down in no time at all. You will get worse mileage doing "Pulse and engine-brake" than steady speed.
Yes agreed, you need to shift to neutral to make your glides longer. Coasting in gear promotes engine braking, that's why you are losing so much speed when gliding.
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Old 07-13-2013, 09:36 PM   #10 (permalink)
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Pulse & Glide at low speeds is really only efficient for manual transmission vehicles.

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