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Topic Review (Newest First)
05-29-2013 07:56 PM
NFRs2000NYC
Quote:
Originally Posted by Numbercruncher View Post
The fuel injectors shut off while coasting in gear but if you are in neutral they still fire to keep the engine running. You are better off slowing down in gear than in neutral.

NC
Agree with this. Anyone here own guns? Whats rule #1? You never point it at anything you don't intend on shooting.....a paramount rule with manual transmissions is you do NOT coast in neutral. Why? Simple. If there is an immediate threat, you have no time to react since you have no power. If someone is about to hit you but you have a tiny window to accelerate out of their path, that split second that it will take you to shift and engage a gear is all you need to get hit. It's simply bad practice. If you are rolling to a red light, coast to in in gear, then when you are almost at a dead stop, disengage.
05-29-2013 07:54 PM
NFRs2000NYC
Quote:
Originally Posted by insylem View Post
Sounds like these turn off the fuel injectors like my chevy does then.
All fuel injected vehicles do this.
05-29-2013 07:53 PM
NFRs2000NYC
Quote:
Originally Posted by mgola27 View Post
Do you have any hard info to back this up? Not doubting you, but I'd love some info to have a discussion with my wife about it. She thinks I drive with the revs too high (3k) while I feel she lugs the motor too much (<2k).
Yes I do, just not on my JK. I'll be taking my s2000 out soon, and I vill videotape what I am talking about. It is a 6 speed and turbocharged, so the effect is even more exaggerated.

As for info, you all already know this. Gas being squirted by the injectors isn't controlled by RPM, but rather by throttle position. You can use zero fuel at redline, and a heap of fuel at 1500rpm.
05-29-2013 07:50 PM
NFRs2000NYC
Quote:
Originally Posted by Numbercruncher View Post
I don't agree with this at all. If I am running at 30 mph in top gear at 1,200 rpm vs 2nd gear at 4,000 rpm I am burning way more fuel in the lower gear. Please explain how I can get 50 mpg at 6,000 rpm.

NC
Not what I said. If you are at 30, and want to STAY at 30, then you leave it in a gear that doesn't lug. However, if you at 30 and need to get to 55, you are better off gaswise downshifting.
RPMs have nothing to do with it. Go to a high mountain pass, leave it in second, and roll down the pass in second without hitting the gas. You will roll down at redline the entire time, and use absolutely no fuel. Fuel injected vehicles do not use any fuel when there is enough momentum (while in gear) to roll forward and maintain idle. Fuel is spent at a rate which depends on your throttle position sensor (TPS) and how far you push the loud pedal. RPMs are a byproduct, not the cause. Lets have a little example (it won't be accurate in terms of the JK, just so you can make sense of it.)

Lets say we are cruising at 30mph. We need to get to 55mph on a flat surface. If we are in 4th, lets say we are at 1000rpm and if we are in 2nd we are at 3500rpm. Assuming we do NOT shift out of the above gears, the motor will work HARDER to reach 55 from 1000rpm than it will from 3500rpm. Harder means more fuel will be needed, since you will need to press the accelerator deeper into the carpet to get equal acceleration.

Do not mistake the above that you should be cruising at 70mph in 2nd gear running 6000rpm. The thread was about shiftpoints, and shifting EARLY, contrary to most people's belief is not only more stress on the motor, but more stress on your wallet in terms of MPG.
05-29-2013 07:15 PM
jkjeeper06
Quote:
Originally Posted by Numbercruncher View Post

The fuel injectors shut off while coasting in gear but if you are in neutral they still fire to keep the engine running. You are better off slowing down in gear than in neutral.

NC
Also can someone clear up another question for me: the pentastar has VVT, but the 3.8 does not, doesn't that mean on that engine it cannot shut off the injectors and it would just go back to the minimum fuel input?
05-29-2013 07:14 PM
jkjeeper06
Quote:
Originally Posted by Numbercruncher View Post
I don't agree with this at all. If I am running at 30 mph in top gear at 1,200 rpm vs 2nd gear at 4,000 rpm I am burning way more fuel in the lower gear. Please explain how I can get 50 mpg at 6,000 rpm.

NC
NFRs2000 is exaggerating on the point a little bit but he is correct that lower RPM's don't mean better mileage. If I'm going 30 in 5th gear I'm doing 11-1200rpm. Say I come to a hill, I can hit the pedal harder, and at that point it may barely maintain speed, or I can downshift and be at 2000rpm and have way less throttle. The first is a prime example of bogging down the engine where you are using more gas at a lower rpm. If you floored it in that case and it doesn't accelerate much you are really getting worse mileage than simply downshifting
05-29-2013 07:08 PM
JeepDrum
Quote:
Originally Posted by Numbercruncher View Post

The fuel injectors shut off while coasting in gear but if you are in neutral they still fire to keep the engine running. You are better off slowing down in gear than in neutral.

NC
Does the same thing happen while coasting in gear/ in neutral with the clutch in? Also, if I'm at a red light, would it burn less gas if I sat there with it in gear but with my foot on the clutch? Or, would it be the same as sitting there in neutral? I've only been driving a standard for about 3 months now and I'm still trying to learn how everything actually works.
05-29-2013 05:36 PM
Abnormal-JK
Quote:
Originally Posted by jkjeeper06 View Post
I like shifting at 2000-2500 around town and then 3000 on hills or highways. It gets better mileage as long as you know not to bog it down
Same... generally 23-2500... don't usually downshift to slow the vehicle, and often coast to stops or pick next gear based on coast speed and bring 'er back up...
05-29-2013 05:21 PM
Numbercruncher I don't agree with this at all. If I am running at 30 mph in top gear at 1,200 rpm vs 2nd gear at 4,000 rpm I am burning way more fuel in the lower gear. Please explain how I can get 50 mpg at 6,000 rpm.

NC


Quote:
Originally Posted by NFRs2000NYC View Post
Depends on the desired outcome.

Maximum performance? Obviously at redline.

Maximum MPG? You shift from eco to eco...if you shift too early, your RPMs will drop too much and you will lug the motor, which will require you to press the accelerator harder, causing your throttle position sensor to dump more fuel. I've said this before and I'll say it again so people actually learn. RPMs have absolutely NOTHING to do with MPG. It LOOKS like they do, but they dont. You can do 7mpg at 1000 RPM and 50mpg at 6000 rpm. Your MPG has to do with one thing and one thing only...your throttle position sensor....aka, how hard you need to press the accelerator pedal.

The easy answer to your question.....once you learn the Jeep motor/tranny behavior inside out, you will be able to extract the maximum amount of MPG by simply doing this...when you shift, shift at a point that the next gear will allow you to sustain forward momentum with minimal throttle input. Sometimes that can be as little as 2500 rpm, sometimes it may need to be at 5000rpm. The key is, never needing to press the loud pedal harder to continue forward momentum.

If you need a clearer explanation, just let me know and I'll post up an example for you.
05-29-2013 05:18 PM
Numbercruncher
Quote:
Originally Posted by mgola27 View Post
Do you have any hard info to back this up? Not doubting you, but I'd love some info to have a discussion with my wife about it. She thinks I drive with the revs too high (3k) while I feel she lugs the motor too much (<2k).
The fuel injectors shut off while coasting in gear but if you are in neutral they still fire to keep the engine running. You are better off slowing down in gear than in neutral.

NC
05-29-2013 05:16 PM
Numbercruncher
Quote:
Originally Posted by ghost View Post
There are plenty of videos available on YouTube about driving a manual. With that being said, in the racing world the driver changes up when the rev counter hits the red-line, so they can extract all possible power from the engine. In the everyday world, I change up more often than not (during everyday driving) around 3000 RPMs. The lower the rpms you change at the better you gas millage will be (at least in theory)

As for down shifting I hate it and everything about it, kinda sucks that I have to do so much. With that being said I just match the revs and slip it into gear.
Many redlines are beyond peak hp and at that point you are making less hp and less torque. I can't see a reason to shift at higher rpm than where hp maxes out.

I have also read that if the rpm's don't drop lower than the torque peak in the next gear then you are accelerating as fast as the vehicle is capable of. I am not sure is this is true or not but if I read it in a car magazine it must be . . . lol.

NC
05-29-2013 04:21 PM
jkjeeper06
Quote:
Originally Posted by surferdude88 View Post
Alright definitely listening to the engine is the MOST important part to driving a stick.
This. It's a balancing act. Having the RPM's low is good, but you also can't be so low that it can't make enough power and bogs down
05-29-2013 04:17 PM
surferdude88 Alright definitely listening to the engine is the MOST important part to driving a stick. Also, you and your wife are driving fine rpm wise. Your getting better performance and your wife is burning less gas. Sounds like the difference between most husbands and wives. But I personally like to run about 2500 rpms with my jeep... And I read some people saying they start in second. It might work for you but I have an inline six and 33in tires so first is a must. This goes to show it just depends on the car. Just listen and the engine will tell you what it wants.
05-29-2013 04:05 PM
mgola27
Quote:
Originally Posted by NFRs2000NYC View Post
I've said this before and I'll say it again so people actually learn. RPMs have absolutely NOTHING to do with MPG. It LOOKS like they do, but they dont. You can do 7mpg at 1000 RPM and 50mpg at 6000 rpm. Your MPG has to do with one thing and one thing only...your throttle position sensor....aka, how hard you need to press the accelerator pedal. .
Quote:
Originally Posted by NFRs2000NYC View Post
Coasting in neutral burns gas. Coasting in gear doesn't. Any coasting done in gear is free miles!

Do you have any hard info to back this up? Not doubting you, but I'd love some info to have a discussion with my wife about it. She thinks I drive with the revs too high (3k) while I feel she lugs the motor too much (<2k).
05-29-2013 03:55 PM
live_slow
Quote:
Originally Posted by jkjeeper06 View Post
I like shifting at 2000-2500 around town and then 3000 on hills or highways. It gets better mileage as long as you know not to bog it down
I do about that. I'm in 5th by 40-45+- mph with 4.10 gears and 33" tires. Its new. So on Fridays and Mondays I hold gears to 3.5 - 4 k just to remind it what's what :-p
05-29-2013 03:39 PM
jkjeeper06 I like shifting at 2000-2500 around town and then 3000 on hills or highways. It gets better mileage as long as you know not to bog it down
05-29-2013 02:25 PM
insylem
Quote:
Originally Posted by NFRs2000NYC View Post
Coasting in neutral burns gas. Coasting in gear doesn't. Any coasting done in gear is free miles!
Sounds like these turn off the fuel injectors like my chevy does then.
05-19-2013 03:08 PM
NFRs2000NYC
Quote:
Originally Posted by GonzoBobH View Post
At a much higher RPM then most would suspect... just not sure what it is.
but what do I know: I spend half my time popping it into neutral to coast down our Tucson hills.

Anyway, gonna have to pay attention next time I am out.

But as Sgt93 said, the engine will tell you.

BobH
Coasting in neutral burns gas. Coasting in gear doesn't. Any coasting done in gear is free miles!
05-19-2013 02:20 PM
scottmphoto 3:46pm.
05-19-2013 01:04 PM
traitor08 Ok, I have read some good and bad things here. I will give my opinion.

Its a jeep so your probably not going to be drag racing. But if you do, and if you hit the limiter you are doing it wrong. Dyno vehicle, find best rpm for best part of torque/hp curve and set shift light at the high end well before rev limit. It is there to keep from blowing, not for shifting.

Terrain and stituation dictate my rpms. If I am on an on ramp and I don't have to merge at speed, 3k is about right. If I am on a side road pulling onto highway when they are going 65. More like 4500 ish, depending on traffic and room to accelerate. Offroad I prefer to be in a lower gear, keep rpms up and speed down.

Downshifting, I agree with the rule of 10's. For every 10 mph, use that gear. Exception for me is 10mph. I use 2nd all the way to a stop.

The motor will tell you when it is happy.

It isn't rocket science. The motor will lug down to 500rpms or so. As with anything, takes a little seat time to know what it likes. Change technique a little and find where the jeep responds and shifts best.
05-19-2013 12:46 PM
GonzoBobH At a much higher RPM then most would suspect... just not sure what it is.
but what do I know: I spend half my time popping it into neutral to coast down our Tucson hills.

Anyway, gonna have to pay attention next time I am out.

But as Sgt93 said, the engine will tell you.

BobH
05-19-2013 12:39 PM
Rooster76 UPSHIFTING
I agree mpg has more to do with the % of petal pushing vs RPMs. Depending on how much I'm accelerating I tend to shift at around 2500-3000 for 1st-2nd. The rest I will shift in the green area indicated on the tach. Usually above 2000, and below 2400 for around town/highway. If I'm getting on the interstate and need to pass I'll keep it in 5th for the extra acceleration power.

OVERDRIVE SHIFTING
If you look in the user manual it will give some hints of MPH to shift. They break it down into accelerating and Cruising times to shift up. It basically works out to be to upshift @ 2000 rpm minimum when cruising (at the speed your going to keep). Maybe on the flattest of roads or on a decline I would consider upshifting at 1800 at the very lowest to gain a few mpg.

DOWNSHIFTING
When starting out I used an equation that would get me in a good working gear. Take the speed/10 + 1 for the gear. So 20mph = 3rd. 30=4th. It's not ideal but will get you close enough. If I'm going to a stop light I keep it in gear and only shift down if the light changes.

HSA=HILL START ASSIST
I like HSA. Once you know it's there and can anticipate it holding the breaks for a bit on an incline its not so bad. Offroad it is really nice.
05-18-2013 03:20 PM
Sgt93 Listen to the engine, it will tell you all you need to know.
05-18-2013 01:31 PM
NFRs2000NYC Depends on the desired outcome.

Maximum performance? Obviously at redline.

Maximum MPG? You shift from eco to eco...if you shift too early, your RPMs will drop too much and you will lug the motor, which will require you to press the accelerator harder, causing your throttle position sensor to dump more fuel. I've said this before and I'll say it again so people actually learn. RPMs have absolutely NOTHING to do with MPG. It LOOKS like they do, but they dont. You can do 7mpg at 1000 RPM and 50mpg at 6000 rpm. Your MPG has to do with one thing and one thing only...your throttle position sensor....aka, how hard you need to press the accelerator pedal.

The easy answer to your question.....once you learn the Jeep motor/tranny behavior inside out, you will be able to extract the maximum amount of MPG by simply doing this...when you shift, shift at a point that the next gear will allow you to sustain forward momentum with minimal throttle input. Sometimes that can be as little as 2500 rpm, sometimes it may need to be at 5000rpm. The key is, never needing to press the loud pedal harder to continue forward momentum.

If you need a clearer explanation, just let me know and I'll post up an example for you.
05-18-2013 01:22 PM
Aeschylus I wind up shifting 2,3,4,6 most of the time. I tend to only use 5th if I am going up a continuous incline at moderate speed and want to maintain speed or gradually accelerate. Otherwise, I just use 4th for power / acceleration and once I am up to ~40 MPH or 2500+ RPM I go straight into 6th. The Jeep will drive fine in 6th down to 35 MPH - not much power there, but it will drive fine.

Got in the habit of only starting in first on really steep hills (and starting in second the other 99.9% of the time) about 10 years ago and been doing it ever since.

Also, I turned off HSA right away.
05-18-2013 01:08 PM
JKWrangler2012 Shift around 3k, as mentioned. Sometimes more, sometimes less.. You're not hurting anything.. There's a rev limiter if you're racing
05-18-2013 12:06 PM
TomL Hi there. I also have a manual 2012, and it's great! I hope you love it! I usually shift at around 3000 rpm. I've tried various methods, and that seems to work best for me. For maximum fuel efficiency, I tend to run it at around 2100 rpm in 4th gear around town. It's hilly around here, so having it in a lower gear helps get up those hills without using so much gas.

When downshifting, I give it a little gas when I clutch in to keep revs up. That way it doesn't put so much wear on the clutch plate. You'll get a feel for where the shift points are, and it will get easy.

Oh, and one other thing. I would recommend turning hill start assist off! I had it on for about a day when I was first learning, but it just got in the way after that.
05-18-2013 12:05 PM
ghost There are plenty of videos available on YouTube about driving a manual. With that being said, in the racing world the driver changes up when the rev counter hits the red-line, so they can extract all possible power from the engine. In the everyday world, I change up more often than not (during everyday driving) around 3000 RPMs. The lower the rpms you change at the better you gas millage will be (at least in theory)

As for down shifting I hate it and everything about it, kinda sucks that I have to do so much. With that being said I just match the revs and slip it into gear.
05-18-2013 11:48 AM
Rickyretana13
When is the best time to shift in a manual?

Hello to all who read this

I just started driving manual and I'm basically wondering when in the best time time to shift?
I drive a 2012 jeep wrangler 3.6L
Also, the best way to downshift as well...

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