CODFISH or Pulse and Glide? - Fuelly Forums

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Old 09-14-2006, 06:03 PM   #1
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CODFISH or Pulse and Glide?

I tried COFISHING on my last tank and am a little disappointed in my results. I only went from 52.08 to 53.78 mpg. I would CODFISH over about a 22 mile distance of a 37 mile drive home home each day. On the way to work in the morning I didn't do it so I wouldn't be late. Anyway I would speed up to about 50-55 mph then coast with engine off to about 35 mpg, bump start, speed up and start all over. It would take about .4 miles to get back up to speed and then about .3 miles to slow down to 35 mph.

Is this to fast a speed to do this? (Should I try Pulse and Glide?)

Should I be able to coast farther than I am? (Is something dragging me down?)

Should I coast to an even slower speed before speeding up?

Should I speed back up quickly or slowly?

I think I need a SuperMid (not in the budget currently ).

Any other technique suggestions? (I'm costing to stoplights trying not to stop, turning it off when I do stop, driving the speedlimit etc.)

Thanks for any input!!
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Old 09-15-2006, 08:05 AM   #2
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Boy, I sure suck at 'search'. What the .... is CODFISHing, and why does it always appear capitalized here?

If I start talking about it I'm going to type "Codfishing" and be a rebel. Then again, if I were a hotdog I'd probably smear mustard & relish all over me & eat myself. hmm.
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Old 09-15-2006, 08:32 AM   #3
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Coast On Demand Forced Ignition Shutoff. Ideally, accelerating in your engine's minimal BSFC are will maximize engine efficiency, and shutting off/ dropping in nuetral will remove driveline friction losses (everything spinning) from a portion of your drive. So, you can do one, the other, or both. You can do coast down tests over a portion of road to figure out how much more energy keeping the car in gear requires, and as a rule of thumb, accelerating in the minimum BSFC region roughly doubles engine efficiency.

Edit- When coasting, the injectors will turn on once the car gets down to a certain rpm, which is really inefficient, so you'll want to stay above that rpm if you're coasting in gear.
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Old 09-15-2006, 09:43 AM   #4
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I distinguish between CODFISHing and P&G like this:

P&G is what I do when I could otherwise just be cruising along at a constant speed unmolested by other cars or stops. It's a continuous, repetitive process.

CODFISHING is more for sub/urban driving where you kill the motor and coast approaching turns, stop signs, lights, etc.

The difference is: to someone watching me P&G would think I'm insane, whereas CODFISHING is pretty much invisible to anyone observing (unless you do it and hold up traffic with extended coasts).
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Old 09-15-2006, 09:58 AM   #5
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...(unless you do it and hold up traffic with extended coasts).
You say that like it's a bad thing.

I tried killing my VW engine on a couple of drives and it started acting very strangely. A blower that I didn't even know existed started running for 30 seconds every minute or two, even when the car was turned off. It's supposed to add air to the exhaust manifold to burn excess HCs when the engine is running rich (cold mode). If it fails, the OBDII will tell on me next time I get it inspected, and it's expensive to replace (damn VW complexity). Ideas?
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Old 09-15-2006, 10:07 AM   #6
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Interesting. Do you know what kind of sensor control the blower uses?

If it runs off a temperature sensor, that might explain it. You likely killed the engine immediately after being under load, and cooler exhaust hasn't had a chance to flush the manifold. Just a theory.
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Old 09-15-2006, 10:27 AM   #7
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Originally Posted by MetroMPG
Interesting. Do you know what kind of sensor control the blower uses?

If it runs off a temperature sensor, that might explain it. You likely killed the engine immediately after being under load, and cooler exhaust hasn't had a chance to flush the manifold. Just a theory.
I'm pretty sure it's temperature controlled (but which temp. sensor, I'm not sure). It's run by a relay that's controlled by the ECU.

By burning the extra HCs in the manifold/head pipe, it probably has a side benefit of heating up the cat. a little faster.

I dealt with it at the time by unplugging the blower motor (no fuse would kill it) to keep it from killing the battery when the engine is off. It's since returned to normal.
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Old 09-15-2006, 06:18 PM   #8
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None of the replies really answered any of my questions.
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Old 09-15-2006, 06:26 PM   #9
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We can't answer some of the specific questions, because we don't know your car. E.g. whether it's coasting well or not, or what your best rate of acceleration is (though omgwtfbyobbq mentioned if you had a BSFC map for your engine, you'd have the answer).

I can tell you that the higher your upper pulse speed, the smaller the benefit of doing it. If you P&G below speeds where aero penalties are worst, you'll have better results.

So that would mean an upper speed of around 45 mph I would say, and a lower speed that would let you engage 2nd gear a little below its best BSFC engine speed.

But again, I don't know how your car is geared. So this is kind of guesswork. Sorry.
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Old 09-15-2006, 06:37 PM   #10
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That helps some, thanks. I noticed it does seem to slow down pretty quickly from 55 but if I'm in town it seems to coast fairly far. So CODFISHING is basically for slower speeds? I should try the pulse and glide at speeds above 45? S far as my BSFC I need instrmentation to figure this out? I guess I can't complain, I've averaged almost 52 mpg for over a thousand miles now.
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