I'm assuming you mean coasting? My definition of cruising is at part throttle? On the question I would say theoretically this is true but it depends. The EFI engine in question has to have a certain type of programming such that when the engine is being driven by the wheels, i.e. when you are coasting in gear, the injectors stop and thus no fuel is being consumed. I've only seen this on a VW when my friend was tuning it on the street. If he let off throttle and stayed in gear the injector duty cycle would goto zero. I watched on a laptop he had me hold. If you go into neutral then the engine has to idle on its own thus using fuel. I don't know if all EFI computers do this or not. I'd imagine the older ones may possibly not. The VW was a 2000. Do the 4A engines do this? I don't know.
Now if you have a carb, then I'd say whichever mode, gear or neutral, gives you the lowest RPM will use the least fuel. Since a carb doesn't have the ability to shut off fuel, whenever the engine is turning, either by itself or by the wheels, it will be using fuel.
I'm assuming you mean coasting? My definition of cruising is at part throttle? On the question I would say theoretically this is true but it depends. The EFI engine in question has to have a certain type of programming such that when the engine is being driven by the wheels, i.e. when you are coasting in gear, the injectors stop and thus no fuel is being consumed. I've only seen this on a VW when my friend was tuning it on the street. If he let off throttle and stayed in gear the injector duty cycle would goto zero. I watched on a laptop he had me hold. If you go into neutral then the engine has to idle on its own thus using fuel. I don't know if all EFI computers do this or not. I'd imagine the older ones may possibly not. The VW was a 2000. Do the 4A engines do this? I don't know.
Now if you have a carb, then I'd say whichever mode, gear or neutral, gives you the lowest RPM will use the least fuel. Since a carb doesn't have the ability to shut off fuel, whenever the engine is turning, either by itself or by the wheels, it will be using fuel.
Thank you.
Where I live its very hilly, so when im in gas saving mode I cruise up the hills in 5th and *coast* (thank you ) in neutral down.
On a side note what uses less fuel in a scenario like: I have a choice of either 5th gear at WOT or 3rd or 4th at half throttle, which would use less fuel if both meant i stayed at a constant speed up the incline?
Another example - which is more efficient? WOT at 2000rpm or Half throttle at 4000rpm?
From my experience just look at it like this, the lower your engine RPM's are the better and less hard your engine is working, so it needs less fuel. If you're about to go down a big hill, I always stick it in neutral and just coast that beotch. Saves gas in the long run if you do it whenever you can. I dont even downshift to stop, I just throw it in neutral a good ways before the light and just use my brakes. So to answer your question, yeah it does help a lot!
From my experience just look at it like this, the lower your engine RPM's are the better and less hard your engine is working, so it needs less fuel.
I wouldn't recommend looking at it this way.
Consider, instead, a bicycle. Would you go up steep hills in high gears because you have to turn your legs less? No. You use a lower gear because the overall effort is less even though you are turning your legs more.
Replace "bicycle" with "car" in the previous example and also replace "legs" with "engine" and you'll see why you want to keep the car running in its powerband.
Back to the bike analogy, think about how hard it is on your legs and knees to go up hill in high gear. That's the same extra pressure that's being put on the lower end of the engine -- the connecting rods, crank, etc.
I always stick it in neutral and just coast that beotch. Saves gas in the long run if you do it whenever you can. I dont even downshift to stop, I just throw it in neutral a good ways before the light and just use my brakes.
This depends on what the EFI computer is programmed to do. Some are smart enough to cut fuel when coasting in gear, i.e. it can sense when the engine is being driven by the motion of the car. So you would be wasting fuel as you are coasting or braking in idle. If the computer doesn't do that then you are correct.
Problem is I don't think anyone knows what these computers do. Anyone?
This depends on what the EFI computer is programmed to do. Some are smart enough to cut fuel when coasting in gear, i.e. it can sense when the engine is being driven by the motion of the car. So you would be wasting fuel as you are coasting or braking in idle. If the computer doesn't do that then you are correct.
Problem is I don't think anyone knows what these computers do. Anyone?
All this EFI talk is tangential to a thread titled "Cruising in neutral VS in gear - 4AF carb question."
But... Second generation MR2s rolled off the factoryr starting in 1990, the same year that Corollas got EFI. MR2s will cut fuel injector duty to 0% when coasting in gear (as long as revs are above a certain level; at low RPM, fuel is added to keep the car from stalling). I suspect the Corolla is the same way.
Don't hold me to it, but I believe all EFI systems will use less gas in a closed-throttle decelaration, than in an idle-coast.
I believe just like a carb engine, the greater the vacuum in the intake manifold, the less fuel you are using at that moment.
To really drive miserly with a carb engine, I suggest you get a vacuum gauge, connect the line to your intake manifold and mount the gauge so you can see it while you drive. Like I said before, the more vacuum you can maintain, the less gas you will be using.
The other thing that many people don;t think of is, the more you use your brakes while driving, the more gas you are wasting.
Try and drive at a steady pace.
Avoid hard accelleration.
Keep enough space between you and the car ahead so you don't have to brake every time they do, but can coast till you can resume your previous speed.
Don't wait till you are ready to brake to take your foot off the gas pedal. Try to predict how far from a stop, you need to let off the gas, to minimize your braking.
Just think that every time you brake, you are wasting momentum that you just used gas to achieve.
So drive slower and brake less.
__________________
'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
Don't hold me to it, but I believe all EFI systems will use less gas in a closed-throttle decelaration, than in an idle-coast.
There may(?) be some early ones that didn't, but as a rule I think you're correct.
For our application, here's a discussion on it in L-Jetronic systems (used in these engines):
Quote:
Originally Posted by Bosch Automotive Electric/Electronic Systems, 2nd Edition (page 99)
Overrun fuel cutoff is the interruption of the supply of fuel to the engine in order to reduce consumption and emissions during downhill driving and braking. When the driver takes his foot of the accelerator pedal while driving, the throttle valve switch signals "throttle valve closed" to the ECU and fuel injection is interrupted. The engine speed switcing threshold for injection pulse cutoff, as well as that for the resumption of fuel injection depend upon engine temperature
Somewhere south of 1500 RPM is where you will always get fuel injected to keep it idling smoothly.
Quote:
Originally Posted by Donald
Just think that every time you brake, you are wasting momentum that you just used gas to achieve.
Agreed completely.
I drive fast and accelerate quickly (as quickly as a carbed Corolla can, at least). I spend a large percentage of the time at WOT and above 4000 RPM. But I also rarely use my brakes. I get a consistent 32+ MPG.
I drive fast and accelerate quickly (as quickly as a carbed Corolla can, at least). I spend a large percentage of the time at WOT and above 4000 RPM. But I also rarely use my brakes. I get a consistent 32+ MPG.
I cruize at 70-75 on the express way, (about 3200 RPM) accellerate on the aggressive side of moderate, or the mild side of hard, and I am getting a fairly steady 29MPG.
I think I could get better if I tried, but I even walk fast most of the time.
__________________
'88 Corolla, AE92 SR-5, 7A-FE swap/GT-S suspension
'87 Corolla, AE82 FX-16, 4A-GZE swap (autocrosser)
'03 Tundra 4X4 Access Cab, (FX tow vehicle/Home Depot runner)
Modification: Changing something to what you thought it should have been from the start!
I almost forgot about this, but the single biggest thing I've done to improve the mileage of my Corolla was change the oil weight from a diesel 15-40 to the cheapest 5-30 I could find. I immediately saw a steady 2+ MPG difference. Surprised the heck out of me but I'm pretty sure because it was the only change I made to the car and my MPG jumped from high 29s to low 32s.
I cruize at 70-75 on the express way, (about 3200 RPM) accellerate on the aggressive side of moderate, or the mild side of hard, and I am getting a fairly steady 29MPG.
I think I could get better if I tried, but I even walk fast most of the time.
Consider, instead, a bicycle. Would you go up steep hills in high gears because you have to turn your legs less? No. You use a lower gear because the overall effort is less even though you are turning your legs more.
Replace "bicycle" with "car" in the previous example and also replace "legs" with "engine" and you'll see why you want to keep the car running in its powerband.
Back to the bike analogy, think about how hard it is on your legs and knees to go up hill in high gear. That's the same extra pressure that's being put on the lower end of the engine -- the connecting rods, crank, etc.
Engine load is a very, very important factor.
So going up hill at low gear with high RPM is better for the engine.
So going up hill at low gear with high RPM is better for the engine.
But what about mileage?
There's no hard and fast rule, it depends on the conditions (speed and hill grade). If I had to make something up, I'd say something like this: "Anytime you are losing speed at 50% throttle, you should probably be in a lower gear."
Your best bet for better fuel mileage is to run a vacuum gauge. Generally speaking, the more vacuum you are drawing, the less fuel you are using. This will also show you how much gear selection affects engine load.
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) in neutral down.
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