Thread: Pulse & Glide question View Single Post
 12-17-2008, 12:19 PM #3 (permalink) mobilerik TacoModder     Join Date: Nov 2008 Location: San Diego, CA Posts: 108 rik's prerunner - '03 Toyota Tacoma Prerunner Double Cab TRD 4A 90 day: 29.68 mpg (US) Thanks: 0 Thanked 2 Times in 1 Post How to Calculate Your Optimal "Pulse-to-Glide Ratio" Calculating your Optimal "Pulse-to-Glide Ratio" depends on your GPH during acceleration and glide. For instance, Pulse in the Prerunner uses between 3.5-4.5gph. Idle during Glide uses about .35-.45gph. I want to compare that to DWL at 52mph, which uses in the vicinity of 1.3gph. For those who want to see how to compute this: P&G Gas Used = PulseRate x PulseTime + GlideRate x GlideTime DWL Gas Used = DWLrate x DWLtime Plug in your averages: You'll need to choose a cycle time to compare, ex. 5 second pulse and 10 second glide = 15 total seconds.P&G gas used = 4.0 gph x 5 sec + .4 gph x 10 sec = 20 + 4 = 24 DWL Gas Used = 1.3 gph x 15 sec = 19.5 So you can see that using a 5 to 10 pulse-to-glide ratio (or 1 to 2) is not fuel-efficient for me. It turns out that I can break even around a 4 to 9 ratio, and I try to shoot for 4 to 10 or 5 to 12. If I don't think I can get a 10 second glide out of it, I won't bother. Of course your numbers will be much different. Mine reflect the difficulty of accelerating and coasting in a 3600 pound brick. You can of course use the same formulas to find ratios for any variations of P&G. For example, sometimes I use DWL at a throttle position too low to hold speed, then gas just enough to continue the cycle. This only works for me if I can limit gassing to about 1-2 seconds to get a 20-30 second slow deceleration out of it... which generally only succeeds for me downhill. If you're in a small car, your ratios will be much more favorable. NOTE for those bothered by units of measurement: You don't need to convert to "hours" to make the above calculation useful. The final units you'll be comparing are technically "gal/3600" -- it's just scaled. You can think of the above as telling you how much gas you'll use if you do 3600 P&G cycles. Also note: These calculations also don't take into account any other losses during a P&G cycle. For example, rev-matching. As it is, my Tacoma automatically rev-matches coming out of Neutral Glide. It's awesome. But if I'm aborting the glide at too low a speed, it'll sometimes miss overdrive, and I have to give it a "panic pulse" to get overdrive back. If I wasn't "panicking" I could probably read the GPH of the extra pulse and add that in as well. __________________ '03 Toyota Tacoma Prerunner (Ecomodder Thread) "Last 3 Tanks": 31.05mpg (02/06/09) Build Photos: Front Wheel Skirts, Rear Kamm Extension and More! My Trip Log Last edited by mobilerik; 12-17-2008 at 06:02 PM..