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Old 07-27-2010, 01:33 AM   #1 (permalink)
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Pulse & Glide Shifting for 04 Civic VTEC

OK, So I gots me a new (to me) 2004 Civic EX:



Ain't she Purdy?

I want to get the best mileage possible. (within reason) Reading through everything, I have come to understand that in town, Pulse & Glide is the way to scoot about. I have been toying with this and am amazed at what a great glider I have. Now reading posts about other cars, I have come to understand, that I want to accelerate at rather high throttle, 75%, till I get to a speed about 5 mph over the speed limit then coast in neutral (engine on, 5 spd Manual) till a few mph under the speed limit.
My question is.....What RPM should I be shifting?
Givin that I have a VTec engine, and as best I can tell, a power curve like this:



Research has led me to believe, the Vtec function basically activates at 4300RPM fully opening 1 of the 2 intake valves which previously was only opening partially. The other intake valve goes fully open all the time. The 2 exhaust valves open equally the same always.

My guess is if I keep it at 70 or so on the highway, (When legal) I'll be getting OK mileage without feeling too much like the old man I'm starting to become. I made a trip 2 weeks ago and got 40mpg doing 71mph or so over 280 miles. I think it would be madness to pulse & glide cross country for hours on end, So I'm going to be content to just set the cruise control and kick back.

I have another question regarding hills, being I'm in Montana, I do run across a few gentle inclines from time to time. What is my strategy on these? If I'm on the highway, I don't mind fiddling about on climbs to get the most MPGs. I'd be willing to slow down, shift gears, & such.

What would be my most fuel efficient way to handle uphills & corresponding downhills?

I know ScanGauge is wanting to be mentioned, but I'm just too much of a tightwad to spring the $150 right now for it. For the 10% gain I figure I could get, it would take 25,000 miles of driving for it to break even. I'm sure I'll get one, just not real soon. I'll keep reminding myself that I'm likely pissing away an entire gallon of fuel with every fill up, and I'll eventually crack.

Aeromods are for another post. I just want to hear how I'm supposed to drive this Pup.

Thanks!

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Old 07-27-2010, 03:34 AM   #2 (permalink)
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Hi ChazinMT,

Your education is about to start, and you're going to think my answers are extreme. They may or may not be extreme, but they're what will give you the best mpg.

First, forget about going over the speed limit. 5 mph over to 5 mph under is if you want your average speed to be slightly less than the speed limit. If you want best mpg, use the posted speed limit as your upper delta point, and 10-15 mph under the PSL as your bottom delta point. On a highway with PSL >55 mph, I use 60-62 mph as my upper pulse speed when there are cars around, and sometimes only 55 mph. When I set my cruise control for a highway cruise, it's at 50-55 mph. My SE-R gets 26 mpg at 72 mph, and 38 mpg at 55 mph. My xB gets 32 mpg at 70 mph, and over 40 mpg at 55 mph. Your Civic will behave similarly.

Then there's how much throttle and which rpm range to use. 75% throttle doesn't mean that. It means 75 LOD on your Scangauge, and it's moderately brisk in my SE-R, but pretty light on my Scion and your Civic. Your best acceleration for fuel consumed comes from your Brake Specific Fuel Consumption curve, but for most 1.5 to 2.0 liter I-4 engines, you start your pulse at 1500 rpm, and end it around 2000 to 2200 rpm - well below your variable valve actuation.

For hills, lightfoot your way up them, drop speed at the top, and enjoy the free coasting down them. When they're steep enough that you need to scrub off speed, DFCO down them in gear, and you won't use any gas.
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Old 07-27-2010, 08:14 AM   #3 (permalink)
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Very good write up by Darrell. 75% load is not 75% throttle. You'll need a scangauge to calculate load, or a vacuum gauge. 70mph will hurt the mileage quite a bit. Even dropping 5 mph will get you 10%+ better mileage.

I agree with all his info except I use a different technique on hills. I tend to pulse up them, stop accelerating near the top, loose some speed before I peak them, and then use the downside to accelerate back up to speed (w/o the engine if possible).
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Old 07-27-2010, 09:22 AM   #4 (permalink)
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Good advice already listed. I tend to follow Daox's method of pulse-up glide-down, but that really requires a gauge.

Your mileage really starts to go down the drain when you exceed 55 mph. The EPA highway test is 55 mph, so Honda (and others) build their cars to do well at that speed. You'll do better at a steady 55 than anything you can do at 70.

Re: Scangauge. I had a best tank of 42 before I got mine. My first 'gauged tank was 46 mpg, and I haven't been below that level since. I calculate that mine paid for itself in about 4 months.

When I do highway trips (pretty rare), I generally target a 45-60 mph range, or 50-65 if I'm in a hurry. Done right, that can give me 65 mpg (or 60 at the higher speeds). Steady 65 is worth about 43 mpg in my car.
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Old 07-27-2010, 09:09 PM   #5 (permalink)
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With a 5 spd manual you can do some really fun gliding. For me, using P+G around town must be done with timing the lights in mind. On the way home there are a series of lights that I essentially time in accordance with my P+G routine. This means I keep up with traffic, each time the light turns green I am gliding past them. My glides are engine off, which boosts FE, but means A/C is useless. Power steering is immediately lost, although not necessary. Full braking power is retained for 3 full stops.

You can experiment with engine off glides, when you need to restart the engine while moving, you can partially and momentarily pop the clutch (with the key in the on position) which starts the engine, then choose the appropriate gear. I will use 5th to restart the engine down to about 20 mph. Using a higher gear to restart the engine means a more gentle bump. You can always use the starter too.

Engine off glides are particularly useful when you know from experience you will be stopping and waiting awhile at a red light, or going down hill.

My approach for small hills is to accelerate up to 5-10 MPH above my target speed and hold my foot on the accelerator at that point. Then allow the car to decelerate on the way up (keeping my speed above a reasonable minimum), reduce the throttle as I approach the top, and allow gravity to take me down, usually with an engine off glide.

As for very long hills, I simply take them at a slow and steady speed on the way up. On the way down there are three approaches: With a shallow grade, I use P+G. The grade will both make pulses easier and extend glides. With a medium grade, I glide with the engine off, allowing the car to accelerate up to the max speed allowed by wind resistance. If the grade is steep enough and the car is accelerating past a safe speed, I restart the engine and allow engine-braking to slow the car. Most cars with fuel injection use DFCO (Deceleration Fuel Cut-Off) which means when you take your foot off the gas, the car uses only its own momentum to keep the engine moving. The minimum RPM for this varies but is usually around 1500.

In a nutshell: Waste as little gas on the way up, take full advantage of gravity on the way down. Most non-ecodrivers take the opposite approach: speed up the grade and ride the brakes on the way down.
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Old 07-28-2010, 01:18 PM   #6 (permalink)
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Slightly off topic, but possibly interesting: Quite often I skip gears when accelerating from a light or stop sign. Say start in 1st gear, shift as soon as possible to 2nd, then accelerate in 2nd fairly briskly to around 25-27 mph and then shift to 4th @ 1500 rpm. Same works from 3rd to 5th. It may not be more efficient (don't have a scangauge) but I make use of the higher revs for better acceleration when merging. Then it is also more natural to keep the throttle open wider on a higher gear trying to keep up the acceleration.

Keep in mind that you lose 3% power for every 1000 ft above sea level. So that's almost 5000 ft for you, right? 15% less hp right away. I know I can feel it when heading into Idaho/Wyoming. Experiment with higher octane gas to allow the engine to advance it's valve timing and give you more torque at lower rpm (or rspm?). It may actually give you more miles per dollar than regular unleaded.

Good luck! I am keen to hear more about your high elevation experiences/experiments.
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Old 07-28-2010, 04:50 PM   #7 (permalink)
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I usually shift 1-3-5 or perhaps 1-2-4-5 depending on the grade. My engine produces a healthy amount of torque and so my goal is always shifting around 1-1.2k rpm. I'm into 5th by 25 mph, so no need to run thru all 5 gears for that, unless I need to accelerate briskly.
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Old 07-28-2010, 07:39 PM   #8 (permalink)
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Thanks Superchow....Thats right on "Topic"! When I first read "off topic", I thought you were gonna try & suggest VG's or HHO generators! (I really hate both of those)

Thanks to all for your suggestions!! I have been driving keeping the RPM's <2500, it's funny that the HP/Torque curve I found Starts logging data at 2500 RPM. I wish I could find a Brake Specific Fuel Consumption curve for my engine. I would almost be willing to bet it has 2 areas of "Sweet Spot" on it, one for 3 valve ops (<4200 RPM) and one for 4 valve ops. So I guess if I treat it like a 3 valve engine, I'll be safe.

Also, My gearing is not very "Tall" on my car, I don't have specifics, I just know that at highway speeds 65 or so I'm at 3200RPM, so the DCFO thing has me wondering? Is there anywhere I can find out this setpoint? Does the ScanGauge have this? I suppose really though, a very small percentage of my driving requires engine braking, and if my foot is completely off the gas pedal, I gotta believe my fuel consumption is in the 1/3 GPH or less mode. So at 65, thats 200MPG for the time I'm engine braking.
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Old 07-29-2010, 09:06 AM   #9 (permalink)
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I think you should NOT skip gears. You run the first gear up to a high rpm (costs you mpg) and/or run the next gear too low (no power). Your best best is to try and keep it in the narrow best-mpg band, about 1500-2200 rpm. Use moderate throttle there, maybe 3/4, until your speed gets too high, then you glide.

I often skip first and start in 2nd, because first is just geared SOOOOOO low. On uphills I'll use first for about 10 ft, then 2nd. I'm into 4th at 20 mph, and 5th at 35.
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Old 07-29-2010, 10:39 AM   #10 (permalink)
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I've been looking at all the Brake Specific Fuel Consumption maps and I think that for our engines, (smallish I4's) we should be around 2500 RPM as a safe bet. It seems engines which are diesels or V8's would do better at a 1800RPM avg. Intuition tells me this too because it seems like for having my foot fairly far down, it is a very slow acceleration rate below 2000RPM. I also thought the whole point to this P & G was to take advantage of driving where the BSFC was lowest, and it looks as though other 16V 4Cyl cars do best at 80% HP and 2600RPM or so.

What happens when you try this Pale dude? Have you tried it? It just seems 1500 RPM is too low.

Obviously you are doing something right to get 80 MPG outta yer sled so my Inquiring mind wants to know.

Thanks.

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