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Old 12-11-2007, 12:45 PM   #1 (permalink)
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Re-attempting Pulse and Glide (with an automatic)

Thanks to newtonsfirstlaw and his pulse and glide spreadsheet. I had given up on the pulse and glide because after several fail attempts I never got better numbers then just my normal style of driving. I figured it was because of the automatic transmission. After plugging in the numbers and studying the fuel maps I decided to give it another try. I've still got a long way to go to perfect the technique. After plugging in the numbers my best pulse comes with an average speed of 40 mph. That is quite a bit higher then I thought and in the previous attempts I was P&G'ing much lower, in the 25 mph range.

Anyway I was really impressed with the results for the first try. From a cold start I was able to do a round trip commute of 48.6 MPG and that was a 52 mile commute in the rain with light and wipers on the whole time and gusty winds. This beats my previous summertime best by almost 1 MPG. In previous attempts I was not aggressive enough on the pulse.

More to follow once I get the technique down.

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Last edited by Lazarus; 12-11-2007 at 12:48 PM..
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Old 12-11-2007, 01:12 PM   #2 (permalink)
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Vehicle details!

I went to double check your garage to see what you're driving - and just realized your '02 Intrepid ISN'T a Chrysler product. And I'm quite sure it doesn't have wipers.

Anyway - glad to hear you're re-investigating the technique. Looking forward to reading more.
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Old 12-11-2007, 01:39 PM   #3 (permalink)
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Great story! Mehbe I'll pick up where I left off with P&G as well (though not with the 350 mile trip home tomorrow).

Will you be doing the same trip soon or have you just done it? Comparison!
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Old 12-11-2007, 05:49 PM   #4 (permalink)
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Quote:
Vehicle details!
It's the Daewoo. I was planning on putting it in the garage when it was time to fill. I don't drive it much now a days unless the weather is bad so maybe next week or so.

Quote:
Will you be doing the same trip soon or have you just done it? Comparison!
I make that commute a couple of time a week depending on the weather. The last 3-4 time I've been around 43 MPG but today the weather was wet and I hit a lot of the lights wrong. The calculator says in perfect conditions I could hit mid 60's. I'll be happy with anything in th 50's. We'll see what happens as I get better with the P&G and learn the route a little better using those techniques. I am not EOC'ing but that figured into the calculator. Hopefully it was not a fluke.
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Old 12-11-2007, 07:00 PM   #5 (permalink)
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Lazarus: I just remembered that auto trans losses are about 8% (from memory). If you have a torque lockup converter this complicates things, because the TLC has nearly no losses.

I'm not sure whether the auto in neutral is comparable to the manual in neutral, so I don't know what the difference is (if any) in the glide phase. Again, check whether this will wear out your trans, in some cars it can.

However, most autos these days have a lockup converter, which means that at cruising and near cruising loads, the lockup converter will engage eliminating the 8% losses. Whether you can accelerate at 62% of BMEP or not is another thing. However, Even given these 8% losses, you might still be better off P&Ging. You'd have to calculate your constant velocity fuel economy and compare.

But glad things are working out for you.
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Old 12-11-2007, 07:17 PM   #6 (permalink)
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Quote:
Originally Posted by newtonsfirstlaw View Post
Lazarus: I just remembered that auto trans losses are about 8% (from memory). If you have a torque lockup converter this complicates things, because the TLC has nearly no losses.

I'm not sure whether the auto in neutral is comparable to the manual in neutral, so I don't know what the difference is (if any) in the glide phase. Again, check whether this will wear out your trans, in some cars it can.

However, most autos these days have a lockup converter, which means that at cruising and near cruising loads, the lockup converter will engage eliminating the 8% losses. Whether you can accelerate at 62% of BMEP or not is another thing. However, Even given these 8% losses, you might still be better off P&Ging. You'd have to calculate your constant velocity fuel economy and compare.

But glad things are working out for you.
Yes it does have a lock up converter. I don't know about the 62% but the max torque happens about 3200 rpm and that seem to work well for the acceleration portion. I was really surprised about the results of todays run and will work on the technique and see how it works out. I glide in N engine on and don't think that will hurt the transmission. It engages smoothly. I appreciate the hard work that went into the spreadsheet. Now if you could do one for lazy americans.
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Old 12-11-2007, 08:06 PM   #7 (permalink)
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Quote:
Originally Posted by Lazarus View Post
Yes it does have a lock up converter. I don't know about the 62% but the max torque happens about 3200 rpm and that seem to work well for the acceleration portion.
I've drawn on the engine map to indicate how much power you want the engine to be producing relative to what it can do, and why.

Note that if you have a choice, via gearing, you want the engine rpms to be as close to 2300 as possible (assuming 4 valve/cylinder car). At any rpm, you want your engine to be loaded such that you are operating within the two bands I have drawn. I calculated the percentage of possible load on the engine as a percentage - stick around 65% and you should be fine. I'd guesstimate that would equate to 65% throttle, as the technique for actually mapping BMEP to throttle requires an accelerometer or dyno.

Note that 0 BMEP corresponds to a no load state on the engine, which is the same negative acceleration in gear as the equivalent neutral coast, which is just a bit above closed throttle.

100% BMEP corresponds to WOT.

Where 65% of the power generated by the engine is in terms of throttle, your guess is as good as mine, although at lower rpms there appears to be a drop off in BMEP near WOT.

I'd love it someone could actually measure this so that we could get a map of rpm versus TPS for 65% BMEP.


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Last edited by newtonsfirstlaw; 12-11-2007 at 08:22 PM..
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