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  #25  
Old 10-13-2010, 04:58 AM
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Re: When can we expect better fuel mileage?

Im not new to MDS or cylinder deactivation methods... I do understand how they work and how in most cases they improve MPG over traditional engines. But I also understand that the drag of 8 cylinders in gear consumes energy.

Try it... you may find that by putting it into nutrual therefor removing the DRAG from your engine while you coast uses LESS fuel. This is not an opinion... We currently are getting over 18MPG city when we apply this driving habbit... It works, and is worth about 2MPG.

Its all good, coasting works well for us... If you find yourself board and willing to try somthing new... give it a shot. You may be pleasently surprised at your MPG gains.

NICK
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  #26  
Old 10-13-2010, 05:30 AM
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Re: When can we expect better fuel mileage?

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Originally Posted by AIR_RAM View Post
...You may be pleasently surprised at your MPG gains...
And perhaps unpleasantly surprised when you have transmission/drivetrain issues. NOT a good idea.
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  #27  
Old 10-13-2010, 06:50 AM
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Re: When can we expect better fuel mileage?

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Originally Posted by Milous View Post
And perhaps unpleasantly surprised when you have transmission/drivetrain issues. NOT a good idea.
+1 for that. Plus you'll be replacing brakes sooner. I am pleased with the mileage I get with the hemi, even with my lead foot.
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  #28  
Old 10-13-2010, 12:44 PM
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Re: When can we expect better fuel mileage?

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Originally Posted by AIR_RAM View Post
Im not new to MDS or cylinder deactivation methods... I do understand how they work and how in most cases they improve MPG over traditional engines. But I also understand that the drag of 8 cylinders in gear consumes energy.....

NICK
I dont think you understand how this system works. Yes 8 cylinders in gear adds drag, but when you are coasting while in gear the computer shuts the fuel injectors OFF. NO energy is wasted because NO fuel is getting burned. The drag is what keeps the engine going without gasoline. If you shift into neutral you force the engine to continue burning gasoline to keep the engine going. Coasting in neutral is a bad idea anyway, not to mention illegal in some if not all states. (I live in VA where it is illegal, I dont know about other states.)
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  #29  
Old 10-13-2010, 01:01 PM
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  #30  
Old 10-13-2010, 01:01 PM
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Re: When can we expect better fuel mileage?

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Originally Posted by AIR_RAM View Post
Try it...It works, and is worth about 2MPG.
You're saying that simply coasting to stop lights while city driving is saving you 2 MPG?

Just to be extra clear --you state that coasting up to stop lights is giving you a fuel mileage improvement greater than 10%??

Wow. Just wow.

B

Edit: As an afterthought, I'd like to hear how you correlate this with the fact that engines idle at higher rpms in neutral than in gear (with an automatic transmission), and that while decelerating, an engine in gear is unloaded.
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  #31  
Old 10-13-2010, 07:35 PM
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Re: When can we expect better fuel mileage?

LOL... This is a feebe guys... It works just as I have posted.. and I have not had any issues with it. So until you try it, all your offering is a personal opinion based on an opinion...

Since I have tested the theory and have been practicing it doing so for several tanks of fuel... Im one up on you with a notch towards the "PERSONAL EXPERIENCE" over your "PERSONAL OPINION".... Take it for what its worth... Just trying to offer some good sound advice on increasing fuel economey that works... your not going to win any debates when your case is built on your own personal OPINION.

In the end it really does not matter to me if you do it or not... So far I have offered some advice to increase fuel economey... what have each of you offered as far as advice goes other then attempt to discredit what I have already found to work well?

It is what is... And I stand by what I have posted as a way to increase your fuel economey with your JEEP.

SPEED SAFE, NICK
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  #32  
Old 10-13-2010, 07:39 PM
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Re: When can we expect better fuel mileage?

Quote:
Originally Posted by ryorde View Post
I dont think you understand how this system works. Yes 8 cylinders in gear adds drag, but when you are coasting while in gear the computer shuts the fuel injectors OFF. NO energy is wasted because NO fuel is getting burned. The drag is what keeps the engine going without gasoline. If you shift into neutral you force the engine to continue burning gasoline to keep the engine going. Coasting in neutral is a bad idea anyway, not to mention illegal in some if not all states. (I live in VA where it is illegal, I dont know about other states.)
Really... so the engine shuts off the fuel injectors completley off when in gear... So please tell me, if the engine is not running on fuel... how does it stay on? I would think it would need fuel to stay running... at least in my 25+years working on engines and racing... I never heard of an engine that does not need fuel to stay running.

I beleive you have been misinformed or just dont understand how MDS works. I think what you had meant to suggest is that when not under load the engine goes into MDS and only runs on 4 cylinders... But it never shuts down all cylinders...This is only because Its only capable of shutting down 4 of the 8 cylinders.

Perhaps you may want to go study up on the MDS system before making another post attempting to discredit my advice. Im not the one trying to make you look bad... Your apparantly after me... So please if you would like to debate... get informed first.

Quote:
Originally Posted by bpmcgee View Post
You're saying that simply coasting to stop lights while city driving is saving you 2 MPG?

Just to be extra clear --you state that coasting up to stop lights is giving you a fuel mileage improvement greater than 10%??

Wow. Just wow.

B

Edit: As an afterthought, I'd like to hear how you correlate this with the fact that engines idle at higher rpms in neutral than in gear (with an automatic transmission), and that while decelerating, an engine in gear is unloaded.
Yes... But Im not just coasting mearly 10 feet at a time either... When I see a light turn Yellow and I know I will have to stop I let off the gas and put it into Nutrual... and coast to the stop... The further I can coast the better. Its like driving for free... and the distance you can cover just coasting with no load VS in drive with load is nearly 4 times as far.

RPMS ALONE DO NOT DICTATE FUEL ECONOMEY! Also, rolling in gear will ALLWAYS use more fuel then idle alone.... And there is no way fuel can be cut off 100% if it did the engine would shut off. When coasting in gear your RPMs are higher then when in idle alone. The high idle is more so to the timing advance in idle then it is to do with increased fuel. I can raise and lower my idle on my truck just by adding timing advance... The AFR leans out and in most cases I would add fuel to richen it back up.


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  #33  
Old 10-13-2010, 07:40 PM
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Re: When can we expect better fuel mileage?

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Originally Posted by AIR_RAM View Post
So far I have offered some advice to increase fuel economey... what have each of you offered ...?

Critical thinking.
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  #34  
Old 10-13-2010, 08:06 PM
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Re: When can we expect better fuel mileage?

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Originally Posted by bpmcgee View Post
Critical thinking.
LOL...

I understand your reserves to the idea... but it works.

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  #35  
Old 10-13-2010, 10:13 PM
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Re: When can we expect better fuel mileage?

AirRam,

You are not listening. This is not a function of MDS. As long as the car is in gear and the wheels are turning, the output side of the transmission is turning. That in turn, drives the torque converter which is connected to the crankshaft. As long as the crankshaft is turning, no other energy is required to keep the engine going. You don’t need a gasoline explosion in a cylinder to drive the piston down if the crankshaft is going to pull it down. Inertia alone is providing all the energy required to move the vehicle forward. By keeping the transmission in gear you allow the wheels to transfer that energy into the engine to turn the crankshaft instead of using the energy generated by gasoline to drive the crankshaft. The same principal applies to MDS however. When it shuts off four of the cylinders do you think it disconnects the pistons from the crankshaft??? No the pistons in those cylinders continue to move up and down just as before, simply without gasoline or a spark. So, when coasting, the computer simply turns all of the spark plugs and fuel injectors off, and the rest of the engine continues to move and function just as before. It is simply getting the energy it requires from another source. This is not a complicated concept to understand.

And just to clarify, I don’t “have it out for you”. A forum is meant to be a place to share information. I don’t think you understand what it is I am trying to say. Miscomunication happens frequently through text, and apparently I have left information out of my previous posts that would have helped you to understand what information I was trying to relay. I apologize for any of my previous posts reading in an offensive manor, as that was not my intent.
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  #36  
Old 10-13-2010, 11:31 PM
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Re: When can we expect better fuel mileage?

From what I've heard, I believe we can expect a 25% increase in fuel economy when the ZF 8-Speed makes its debut next summer.
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