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Old 04-17-2012, 11:01 AM   #1 (permalink)
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Success with diesel fuel cutoff for EOC

I've been trying a bit of P&G with my diesel Golf for a while. I find that on my 7 mile run (partly downhill) into Cambridge I could, if careful, get as much as 93 -100 mpg.

But I've just tried an experiment with a fuel cut-off so that I can stop the engine while leaving the ignition circuit on and am very happy with the results!

I got an indicated 145mpg going into town - and 119mpg coming back ('up hill')!!

I really didn't expect it to make that big a difference over 'engine on coasting'....

I just have a couple of wires and a toggle switch in series with the fuel solenoid on the injector pump for the moment, and it seems to work very well. The engine dies almost immediately - maybe takes 2 seconds to drop to zero revs.

Bump starting in 5th seems to be the smoothest way to restart.

Now I will have to make something more permanent, so am planning on a normally-closed relay in the engine compartment, and a simple push-switch (normally open -push to close) on the dashboard to earth one end of the solenoid coil in order to open the circuit. Hopefully the result will be reasonably fail-safe so long as all connections are made securely (soldered) and the wiring is routed carefully.

BTW This is a NON-turbo car I'm talking about

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Old 04-17-2012, 11:49 AM   #2 (permalink)
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Very impressive! What were your usual results with engine-on coasting? Assuming no other variables changed this would be a good thread to make a case for engine-off vs engine-on coasting.
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Old 04-17-2012, 12:05 PM   #3 (permalink)
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I have a service tech unofficially looking into installing the same type of switch in the Civic. It is good to find another example of a similar install. If it works for my car, I think it will make the daily commute a little easier. I am hoping that all the electronics, including the ScanGaugeII, remain active after engine shutoff and that there isn't a period of time with the steering locked or without power. As it stands, I switch the key off, wait for the engine to completely stop, and switch it back to on. There is a period of no power assist in the steering and probably a shorter period steering lock.
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Old 04-17-2012, 12:15 PM   #4 (permalink)
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I don't know how your ignition key works, but on older Civics it is OFF-ACC-ON-START. When doing engine off coasting you switch the key from ON to ACC where you cannot have steering lock.

I would advise you to never switch the key to off even for short periods of time. The possibility of an accident with the steering lock is just to risky in my opinion.
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Old 04-17-2012, 01:04 PM   #5 (permalink)
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My Ultraguage stays on - reading several thousand MPG! So I don't really know how realistic the indicated results are. Time will tell when I refill the tank. I was expecting to be doing a fairly long inter-city test-run today - but things got cancelled.

The battery warning light comes on to show I'm not charging - but no other warnings.

It's the standard way of shutting off the engine - so can't imagine I'm doing any harm to the injector pump?

As I said - with engine on and in neutral I was getting between 93 and 100mpg on the 'down-hill' run (if there is such a thing as a hill around here!) - but got an easy 145mpg (indicated) when switching the engine off and coasting.

It's about a mile of narrow roads, 5 miles of dual-carriageway (A428) , then, after a round-a-bout its a mile or so down-hill into town (Madingley Rd for anyone who knows Cambridge)

The steering quickly becomes seriously heavy, and brake vacuum assist doesn't last long.

So it is something that needs to be done with some discretion - and not in the midst of heavy traffic!

I'd love to be able to try an alt. delete too - but not at the expense of needing a big new battery. My alternator connector is readily accessible too. But, although I can easily unplug the cable - to cut and alter the wires is not quite possible - I'd probably have to take the front of the car off to get my big fat fingers in there!
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Old 04-17-2012, 01:52 PM   #6 (permalink)
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Some of the hybrid's and thought I heard even a diesel or gas car in Europe uses a electronic system that turns the motor on and off as needed and when coasting.
You have all that but with a switch,I like it, good job.
If it was mounted on the left side of the steering wheel you could switch it off and on in a heart beat.
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Old 05-01-2012, 06:54 PM   #7 (permalink)
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sounds like success to me. I have a turbo - so not going to try it anytime soon.
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Old 05-02-2012, 10:02 PM   #8 (permalink)
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I put a kill switch and remote starter on the gear shift lever


Just tapped into the ignition from behind the dash and routed the wires over to the switches, one normally closed for the kill, one normally open for the start.
Makes P&G so easy and natural that it just seems like "driving" now.
That also takes care of the danger of locking the steering wheel.

To avoid changing steering feel, remove the power steering. Actually, even if you don't ever plan to EOC, remove the power steering. PS is the stupidest most wasteful thing ever to become universal standard equipment.
To keep my brakes working I replaced the vacuum pump with an electric one.

In addition to bump starting in the highest gear, it may help to double clutch - let the clutch out just enough to get the engine going, immediately depress it fully, try to rev match with the accelerator, then let the clutch back out smoothly. It helps reduce the speed loss when you reengage the engine, decreases the jerkiness for the passengers, and reduces wear on the clutch and transmission.
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A few months ago I returned home just as my neighbor pulled into his driveway. It was cold (around freezing) with some rain and sleet, and he yells to me: You rode your bike? In this weather?!?

So the other day we both returned home at the same time again, only now the weather is warm, sunny, with no wind. And I yell to him: You took the car? In this weather?!?

Last edited by JacobAziza; 05-08-2012 at 01:31 PM..
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Old 05-08-2012, 11:37 AM   #9 (permalink)
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The wear and tear on the clutch is one thing I would be concerned about-those are fairly expensive and time consuming to repair. Now if you could fit an alternator/starter combo that would allow you to use it to start the vehicle instead of the bump start method. In any case what you have done is pretty neat, and since I have a VW Jetta TDI with the ALH motor, and similar IP I may at some point experiment with a similar mod.
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http://forums.tdiclub.com/showthread...=306799&page=4

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Old 05-08-2012, 12:37 PM   #10 (permalink)
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Originally Posted by Josh8loop View Post
..... and since I have a VW Jetta TDI with the ALH motor, and similar IP I may at some point experiment with a similar mod.
I don't think the turbocharger would like that much.

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