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Far better than gut instinct, other gauge types, pretty much anything else, if you want improved FE. Requires OBDII which started in '96 so not workable for older cars like mine... |
I don't want to spend the $$$ on a SG. I think my car does fuel cutoff.
Can any other Saturn owners here confirm that s-cars do fuel cutoff? Even if they do cutoff, it seems to me like the glide goes MUCH further out of gear than in gear. In any event, I've changed my commuting route over the past couple days to one that seems to avoid long waits at left turns. Yay! However, my MPG may suffer for a little while yet -- I changed my battery a couple weeks ago, and I think in so doing wiped out the computer's FE knowledge. |
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Rick |
Seriously Jim, you drive a lot, the scangauge will pay for itself in 1/3 the time of a "normal" person.
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On the vacuum gauge, it works more for a carbed vehicle than a fuel injected one. A carb uses airflow across a venturi to create a vacuum at a specific point to mix fuel into the air, but under a situation where the carb is in a full vacuum condition doe to the throttle plate being closed it won't draw as much. On a fuel injected vehicle, the engine is going to put in fuel depending on the O2 sensor in closed loop, with input from the TPS, MAF and IAT with the primary reading coming from the O2. Keeping it in a high vacuum state doesn't make that much difference on fuel injection, at least it didn't when I tried it a few years ago. Pre-computer cars with engine economy gauges were just vacuum gauges.
On the P&G with slight throttle, I think there is something to that. I don't do P&G after trying it and seeing my mileage drop (my engine is too underpowered for the vehicle, takes way too much gas and time to get the speed back up) but I have noticed that if I have a very slight throttle on I can coast farther than I can with no throttle. I figure that with the throttle slightly open, the engine isn't trying to draw air from the tiny idle bleed hole, it's getting it from a much larger area so it isn't pulling nearly as hard. |
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If a driver just doesn't find sufficient control with the engine in neutral I won't disagree with their own perception. However I think it would be difficult or impossible to show that you can coast in gear as well as you can coast in neutral. With or without fuel or wind or anything else. If you're in gear then the car's momentum is being used to spin the engine. If spinning the engine is of value to the driver then OK. But let's not fool ourselves into thinking it's going to get you as far on the same fuel compared with coasting in neutral. If you want to improve on that, you cut the engine off, or install a fuel cut button. I rarely cut the engine on my auto trans car but I know that some standard drivers do it. You can bump start a stick shift car pretty quickly so it's not quite the same as with an auto. |
Jim: my $0.02 worth.
A vacume gauge is not going to be as helpful as a scangauge, no question. However a vacume gauge beats the daylights out of nothing. As far as cost goes, a lot of people who have bought a scangauge have found they have been able to make some significant improvements over what they had been able to do before. I don't think I've heard anyone who's said they didn't think they had gotten enough of a return from their scangauge, to make them feel it had been worthwhile to purchase. However, I don't have one, largely because I don't have the extra cash for one. Consequently, I do the best I can, with what I have. Also I principaly drive a 1989 Honda and I can't use a Scangauge with it. As far as coasting, engine on, in neutral, versus engine on, in gear, their are factors which are at play, that are not all the same. For example, by monitoring the Oxygen Sensor, I can tell that if the engine rpm is above about 1200 and the throttle is fully closed, the ecu quits firing the injectors, totally. Consequently, if I am in a position to coast, in gear, with no throttle position, then I get more effectiveness than if I put the car in neutral and coasted. If I could coast farther enough, in neutral, would it be better? Don't know, but that's where a scangauge might help. I am probably going to try getting a fuel mileage display from an Acura and hook it up on my car, because although it's technically incorrect, the relative efficiencies are what I'm really after. Additionally, since other people on GasSavers have already figured out the wiring and so forth, this seems like a great possible, cost effective way to go, for me. |
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FE-wise, I absolutely agree that coasting in gear can't match NICE-ON coasting... which in turn pales in comparison to EOC. The bit you might have overlooked is this: Quote:
That leaves trying to feather the accelerator into the "Goldilocks region" as one other option to explore, which is all I'm doing: exploring. I'm not offering it as a recommended or even useful technique at this point; I'm too new to all of this... crawl before you walk, and all that. :) I just gave it as another example of where you'd have to weigh this against that to determine which approach was better for a given situation (vehicle, driver, traffic, etc.) Apologies if I muddied the waters by mentioning it at that point. Quote:
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If I can get half the efficiency of a NICE-ON glide I'll be pleasantly surprised. As you both said, I'm giving the engine fuel to keep it at speed the whole time, after all (even if it is unloaded, assuming a perfect rev match). Quote:
Honestly, I want to NICE-ON coast (heck, I want to EOC glide!). I've been playing with it; I love the velvety feel, I love the MPG numbers. But until I feel confident it doesn't put excessive stress on my transmission or TC, I'm not going to push it. In the meantime, I'm playing with whatever other techniques I can think of to see how close I can get to the same fuel efficiency. Maybe I'll settle on coasting in neutral at low speeds and something else on the highway; who knows at this point. Like I said, I'm new. :) I hope that clarifies things a bit? Rick |
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