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Old 05-07-2007, 08:25 AM   #1
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P&G question for suzuki clone drivers.

Over the weekend I installed my injector kill switch. Now I'm ready to try some serious P&G. What is a good technique for these cars? I want to stay around 40 mph most of the time. This is how I did it on the rural part of my commute this morning; I start a ICE off glide at 45 mph and bump start around 35 mph then pulse up to 45 again using 1/2 throttle in 5th gear. If there are hills I try to time the glide with a down slope in elevation and usually pulse up the next hill. Is this optimal for the average speed I want to maintain? Any tips would be welcome. How are you doing your P&G Peakster, it seems to be working well for you?
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Old 05-07-2007, 09:38 AM   #2
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I'd like to hear Peakster's feedback too - particularly whether he's using the same gears & speeds that he originally tried.

I think I recommended he go to one lower gear for the speed he was pulsing to get the RPM up a little bit (closer to where I think the car's best BSFC area is, and to reduce the pulse length).

It's been so long since I drove the "stock" gearing, I can't remember whether a 5th gear 35-45 pulse is ideal.
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Old 05-07-2007, 11:07 AM   #3
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Most of my 'P&G' is on city streets where the speed limits are usually 50km/h (~30mph), so it's kind of between true non-stop P&G and CODFISH since I still have to accelerate from a complete stop at traffic lights.

I usually pulse in 4th gear at speeds from 25-45mph as the car acclerates better and requires less time of the ICE being on. With my car's gearing and engine, I'd say that 5th gear is too high of a gear for my liking when pulsing from 30-40 mph: the engine feels too laboured. 5th is more suited for 40-55 mph pulsing because the rpms are higher at those speeds.

For example: when pulsing firmly in 5th gear, my SG reads around 28-30mpg, while in 4th gear it's ~22 mpg (while I believe 3rd gear is too low at ~16 mpg). Even though there's 6-8 mpg less while pulsing in 4th compared to 5th, I find that the duration with the ICE on is cut in half if I use 4th instead of 5th.

Try doing the P&G in 4th instead of 5th and see how it turns out. 2300-3000 rpms seems to be the sweet spot during the burn, with my car at least. My last tank was still with P&G, but I was excessively hitting 5000-6000 rpms during the first half of the tank in 2nd gear and it still turned out higher than 60 mpg. Yet more evidence that P&G works.

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Old 05-07-2007, 11:32 AM   #4
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Thanks guys.

Quote:
For example: when pulsing firmly in 5th gear, my SG reads around 28-30mpg, while in 4th gear it's ~22 mpg (while I believe 3rd gear is too low at ~16 mpg). Even though there's 6-8 mpg less while pulsing in 4th compared to 5th, I find that the duration with the ICE on is cut in half if I use 4th instead of 5th.
That makes good sense. I wish I had a tach . Peakster, Any idea what your rpms are in 4th gear @ say... 40 mph? I think our overall gearing is similar between our cars. I believe yours has bigger wheels/tires but a slightly lower final drive to make up that difference. I think mine has 4.10 final with stock 12" wheels/tires (21.75" O.D. I think). Also, how much throttle should I use in 4th gear?
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Old 05-07-2007, 11:58 AM   #5
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If you want, you can calculate your RPM at any speed/gear using the calculator on this page:

http://wildcatent.freeyellow.com/zookmods/calc.htm

... and the gearing/F.D. info for your car found about half way down this page:

http://metrompg.com/posts/tranny-swap.htm

---

Peakster pretty much confirmed what I was expecting, which is you'd probably be better off using 4th between 35/45 mph with an aggressive pulse- at least 1/2 throttle.

I usually go by ear - I try to at least push to the point where I start to hear induction noise/growl. Not scientific, but works well for me. Hearing induction sounds tells me I'm opening up the butterfly enough to be reducing vacuum for the burn.
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Old 05-07-2007, 12:20 PM   #6
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Quote:
If you want, you can calculate your RPM at any speed/gear using the calculator on this page:
I just thought of doing that with all math. Now I can just plug in stuff at your link, thanks .

Quote:
usually go by ear - I try to at least push to the point where I start to hear induction noise/growl. Not scientific, but works well for me. Hearing induction sounds tells me I'm opening up the butterfly enough to be reducing vacuum for the burn.
At least half throttle sounds good to me. I can barely hear my engine now since I put the stock CAI back on for the summer. It was very obvious with CAI removed when I was getting the growl . I may move my vacuum gauge to the metro from my truck for more fun.
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Old 05-07-2007, 12:27 PM   #7
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looks like @ 35 mph 4th gear turns the ICE @ 2031 rpm and 45 mph = 2611 rpms. In 5th 35 mph= 1682 rpms and 2162 @ 45. So 4th looks much better.
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Old 05-07-2007, 06:00 PM   #8
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Definitely. I'm so lazy, I didn't plug the figures in to figure that out for myself. Glad you reported back.

...waits for jwxr7's next fill up report....
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Old 05-08-2007, 06:10 AM   #9
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Tried 4th gear pulses going home yesterday. It seemed to work well at keeping the pulses shorter. It was much easier with the kill switch too .

I have some more questions . There are times when I am ready to pulse back up to speed, but I know that conditions won't be good for a glide right away (Like with an approaching long hill). What should I do? Should I pulse up to speed quickly in 4th then just cruise at speed in 5th until I can glide again, accelerate to speed slowly in 5th, or other? Also, should I glide at all if it will be a shorter glide?
thanks, with your help I may hit 70mpg soon .
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Old 05-08-2007, 06:47 AM   #10
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I avoid hard pulses when I cannot anticipate a decent glide (2-3 times farther than pulse). If you are speaking of level ground approaching a hill I would suggest you do whatever you have done before for now.

Till you get used to it, I would only suggest P&G if you know you can get a +compensating glide. Keep up the good work.
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