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Thread: How many miles to a full tank of gas?

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Posts: 41-50 of 108
2012-08-04 21:50:28
#41
no throttle rolling in gear = no fuel until a certain rpm where it would try to resume idle.

ever notice you can slowly let the clutch out in first an the car will take off with no throttle.
2012-08-04 21:53:54
#42
Originally Posted by lynchfourtwenty
no throttle rolling in gear = no fuel until a certain rpm where it would try to resume idle.

ever notice you can slowly let the clutch out in first an the car will take off with no throttle.


Makes sense, but my neutral switch isnt even hooked up. Guess mine wouldn't do this then, which makes my logic make sense.
Last edited by WingmanSR20 on 2012-08-04 at 21-55-01.
2012-08-04 22:05:15
#43
it'll do it with out it just fine..

one way of knowing your neutral isn't working right is when u clutch in while rolling an your rpms ride high till you come to a complete stop, they sometimes will bounce around too.
2012-08-04 23:28:59
#44
Originally Posted by sugarwaterpurpl
damn i get around 400 on 10 gallons hahaha. Baws! And i didnt know that about rolling in neutral. The injectors stop?


Other way around, rolling in neutral = using gas. Going down hill in gear = usually means no gas used.

One time I was low on gas and still had a ton of hills to go through in West Virginia on 64. Well I decided to coast on as many as it was safely to do so. I get to the gas station, my mpg is similar to what it was usually, actually I think it was 1mpg less. That's when I thought coasting in neutral was good for gas.

Originally Posted by WingmanSR20

Here's what I never got. If you are sitting in your driveway holding at 3K rpm, and take your foot off the gas, the car idles. Air is cut down to idle air, the MAF reacts to that, injectors supply idle amout of gas to match idle air for an idle mixture, and the engine revs down until it reaches idle RPM. So if you do the same while driving, whether in gear or not, why would it be any different?

The injectors are supplying enough fuel for idle as the air supply with your foot off the gas is for idle. It doesn't care how fast you're going, doesn't care if your clutch is in or not, it's just going to supply gas to match the incoming air. It simply engine brakes until you get to idle RPM since that's all the power it's making at that throttle location.

The only true way to conserve is to turn off the ignition when coming to a stop. Nobody's going to do that.


Using no fuel is always going to be better then using fuel, for MPG's. Something to keep in mind while idling you are getting 0 mpg, since your not moving. This is why a lot of new cars turn off on stop lights and then start back up when you depress the clutch.

If you use a wideband, while going down hill in proper gear, (small hills generally are fine up to 3rd gear, if you go to say 5th gear on a small hill, your not rolling fast enough to keep the engine running properly thus you will need gas to keep engine running), anyway while in proper gear going downhill you will see your afr's go to the way lean, mine reads 23afr (because gauge itself doesn't read any leaner), but when datalogging it shows afr's above 50. That's no gas being used. If you have a ScanGauge 2, you can see your MPG's go from 20-30 to 100-200mpg easily.

Originally Posted by WingmanSR20
Nope, never had a reason to do a wideband. What criteria would a regular car use to decide when to cut injectors though?


Mainly when decelerating and when going on a hill that's steep enough to keep you rolling without needing fuel support.
2012-08-04 23:36:36
#45
Originally Posted by Vadim


Mainly when decelerating and when going on a hill that's steep enough to keep you rolling without needing fuel support.


Not like that, I was asking more on what criteria does the ECM use to determine when do to it. There has to be set parameters for this to work.


Originally Posted by Vadim

you can see your MPG's go from 20-30 to 100-200mpg easily.



Whats the change when going in neutral then? I'm just curious as I don't have a scangauge or anything like you do.
Last edited by WingmanSR20 on 2012-08-04 at 23-54-01.
2012-08-04 23:51:48
#46
Originally Posted by Vadim
Originally Posted by sugarwaterpurpl
damn i get around 400 on 10 gallons hahaha. Baws! And i didnt know that about rolling in neutral. The injectors stop?


Other way around, rolling in neutral = using gas. Going down hill in gear = usually means no gas used.

One time I was low on gas and still had a ton of hills to go through in West Virginia on 64. Well I decided to coast on as many as it was safely to do so. I get to the gas station, my mpg is similar to what it was usually, actually I think it was 1mpg less. That's when I thought coasting in neutral was good for gas.

Originally Posted by WingmanSR20

Here's what I never got. If you are sitting in your driveway holding at 3K rpm, and take your foot off the gas, the car idles. Air is cut down to idle air, the MAF reacts to that, injectors supply idle amout of gas to match idle air for an idle mixture, and the engine revs down until it reaches idle RPM. So if you do the same while driving, whether in gear or not, why would it be any different?

The injectors are supplying enough fuel for idle as the air supply with your foot off the gas is for idle. It doesn't care how fast you're going, doesn't care if your clutch is in or not, it's just going to supply gas to match the incoming air. It simply engine brakes until you get to idle RPM since that's all the power it's making at that throttle location.

The only true way to conserve is to turn off the ignition when coming to a stop. Nobody's going to do that.


Using no fuel is always going to be better then using fuel, for MPG's. Something to keep in mind while idling you are getting 0 mpg, since your not moving. This is why a lot of new cars turn off on stop lights and then start back up when you depress the clutch.

If you use a wideband, while going down hill in proper gear, (small hills generally are fine up to 3rd gear, if you go to say 5th gear on a small hill, your not rolling fast enough to keep the engine running properly thus you will need gas to keep engine running), anyway while in proper gear going downhill you will see your afr's go to the way lean, mine reads 23afr (because gauge itself doesn't read any leaner), but when datalogging it shows afr's above 50. That's no gas being used. If you have a ScanGauge 2, you can see your MPG's go from 20-30 to 100-200mpg easily.

Originally Posted by WingmanSR20
Nope, never had a reason to do a wideband. What criteria would a regular car use to decide when to cut injectors though?


Mainly when decelerating and when going on a hill that's steep enough to keep you rolling without needing fuel support.


Thats what i meant. in gear no gas. I always coasted, so does my dad in his diesel truck. I always thought, More RPM more gas so if you were in neutral it'd be round 1k and in gear in 5th depending on the speed would be around 3k
2012-08-05 00:13:58
#47
360ish in my p11 with bolts and serious blow by
2012-08-05 00:47:13
#48
In neutral, the car has to keep on as long as the key is in the correct position so it will give fuel to idle. If you are cruising down a hill, stay in 5th gear if you can roll all day long and get great mileage. Going down a hill in neutral is using fuel to maintain idle.

Most modern F.I cars did this in the 80's. Would use no fuel is cruising under its own power unless the RPM would drop below idle.
2012-08-05 02:33:59
#49
I get horrible gas mileage in the vvl b14... Its got n1's and a 16ve tranny. I actually WATCH the tank gauge drop when I really get on it through 3 gears. No matter which ones lol. Id say im getting around 200 miles to the tank. MAYBE.

EDIT
Ill put it to the test and report back... I might change that to around 230 for a full tank. I just know that shit goes faster then I had imagined it would. I think it has a lot to do with the tranny. We shall see.
Last edited by Cyrus on 2012-08-05 at 02-41-24.
2012-08-05 03:02:28
#50
Originally Posted by WingmanSR20

Not like that, I was asking more on what criteria does the ECM use to determine when do to it. There has to be set parameters for this to work.


That would be a question @OnTheChip, since he knows our ECU's in and out.

Originally Posted by WingmanSR20

Whats the change when going in neutral then? I'm just curious as I don't have a scangauge or anything like you do.


From what I remember it was 30-40 at max. I'll try it next time I drive wife's car, I don't drive it much. Turbo P11 is more fun to daily
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