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Old 05-15-2008, 07:06 PM   #1
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pulse and coast?

Iv been having a little fun with my new car, then coming back to my senses, and coasting a lot, and mileage is going up! On the way home, about a 20 mile drive, 12 or so on the expressway, when I got off scangauge read somewhere around the usual 35 mpg for the current trip mileage. So I juiced it up to the truck I was drafting, then just put it in neutral and coasted until the truck was about 1/4 mile away, then did it again. about 5 miles later, I was up to 38 MPG for the trip, and made it down my little street and into the driveway with a high 37 for the trip. It seems even pulsing, and coasting with the engine ON is still better than steady. Man I need a injector kill switch.... That may just be my next mod...
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Old 05-15-2008, 08:33 PM   #2
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Yeah Pulse and coast works well for me too. Today while doing it in city/suburban I was getting 42mpg on the Scangauge. Traffic always destroys my gas mileage though because later on during rush, I couldn't do it. Stop light grand prixers always get in the way.
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Old 05-16-2008, 06:45 AM   #3
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I just started and it's working great for me, based on my gas gauge it appears that I've gained at least a couple MPG. I'm also doing it with the engine on.

The injector kill switch is an interesting idea. I wonder if it's feasible.
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Old 05-16-2008, 06:59 AM   #4
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When the speed demons block the intersection and destroy your coast, downshift to engage fuel shutoff (highest gear to keep revs above 1000). This way you are using no fuel decelerating while you allow the light to change and traffic to start moving again. Time your deceleration to keep fuel shutoff engaged and retain the highest practical speed as you pass through the intersection.

It works better with a manual tranny.

Also when drafting try the 3 stripes rule with big trucks.

Nowadays when a SUV pulls over 2 car lengths in front of me I just look at it as an opportunity to burn less of my gas and more of his.

This is on I64 between Hampton and Richmond VA, where the traffic can get soo heavy the average distance between vehicles is probably less that 6 car lengths.

Let the weavers and inconsiderate morons pass you, its safer to have them in front of you instead of climbing all over your rear bumper.

regards
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Old 05-16-2008, 07:16 AM   #5
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P&G question: To rev-match or not?

I hate having to rev-match 3000 rpm on the highway. Besides the amount of gas required to do so, I'm really terrible at it.

Also, my car has a rev hang issue (supposedly on purpose for emissions) so if I'm going to engine brake (as Gary described above) it's going to burn gas for a few seconds before DFCO.
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Old 05-16-2008, 07:19 AM   #6
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Pulse & Glide is just about the best way to improve mileage. I did a 150 mile highway trip, pulsing from 45 to 60 and gliding down engine-off for the whole trip. 75mpg.

I do rev-match. It'll wear on the car less that way.
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Old 05-16-2008, 07:37 AM   #7
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theholycow:

Not sure if its the same situation, but in the early eighties Nissan Z car FI setup they had a BCDD valve (boost control deceleration device) that delayed the engine revs dropping to idle. The BCDD would hang up as you described and create the same symptoms. The purpose was to prevent high vacuum as the throttle was closed.

To check and see if your injectors are still working when the "hang up" occurs take a long screwdriver or a metal probe type stethoscope and place the end on the injector housing, with your ear on the other end. You can hear the injectors ticking when they are delivering fuel.

Rev the engine and listen. If the injectors stop ticking you have no fuel delivery regardless of the engine speed.

If that is not the case consider having the problem corrected as long as it doesn't cost you an arm and a leg.

regards
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Old 05-16-2008, 08:48 AM   #8
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There's no turbo on my car, so it wouldn't be a BCDD. I can't imagine what could hold it level at a specific RPM without using fuel; if I put it in gear and dump the clutch it will nearly chirp the tires as it kicks the car forward. Others report the same issue with my model, and have been unable to get it fixed as it's part of the design. Perhaps a custom ECU program could fix it.

I intend to be able to monitor my injectors live while driving, so I'll wait to confirm until I get that working.

It makes for really rough shifts until you get used to it...
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Old 05-16-2008, 11:51 AM   #9
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Quote:
Originally Posted by PaleMelanesian View Post
Pulse & Glide is just about the best way to improve mileage. I did a 150 mile highway trip, pulsing from 45 to 60 and gliding down engine-off for the whole trip. 75mpg.

I do rev-match. It'll wear on the car less that way.

Pale: when you P&G, are you easy on the throttle and keep your revs as low as possible, or do you open the throttle and try to hit a certain RPM?
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Old 05-16-2008, 01:16 PM   #10
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Quote:
Originally Posted by theholycow View Post
I just started and it's working great for me, based on my gas gauge it appears that I've gained at least a couple MPG. I'm also doing it with the engine on.

The injector kill switch is an interesting idea. I wonder if it's feasible.
Well, I checked the wiring diagram, and mine would require cutting the wiring harness. This is not for the average user. As always, don't try this at home! Not that I listen to any of that. Anyway I have one fuse that powers a few things, including the ECU, and the fuel injectors. when I pull that, then put it back in, it wont restart unless I turn the key all the way off. The ground is pulsed via the ECU, so I cant touch that...
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