Its-a-JK

So what your saying is that I think its a radical idea not to mod a Jeep? Well since mine completely stock........ I must be radical. Mod or don't mod, neither is radical.

zstairlessone

It may be radical but it's pretty nice looking for one

karls10jk

Is this really still a topic? Drive a reasonable 55-60mph on the highway and enjoy the mileage. I elect not to do 60 and thus I elect to get 17mpg. Easing to 60 would but me at 21ish, based on multiple runs.

mr72

I don't have the formula in front of me but I am pretty sure you do multiply by the Cd.

Good point. And you won't save any fuel. In fact you should just decelerate in gear and don't put in the clutch because there's a fuel cutoff during deceleration in gear but if you idle you will burn more fuel during deceleration.

Cutman

I think 2 doors are radical these days. Good choice.

EclecticJKU

It appears people can't help themselves but to provide nonproductive comments on threads in which a person new to the wrangler world, me, would like a bit of advise.

13 mpg for driving like a grandma is poor performance, even for an unmodified JKU. As it goes, carbon build up and poorly performing injectors were the culprits, no thanks to a handful of comments. For the positive suggestions, thank you. A motor is a motor is a motor. I'm currently unfamiliar of this particular one, but I am learning there are a lot of jackasses trolling these forums.

mr72

Those are just ordinary Jeep owners, or so I have found. Not necessarily unique to this particular forum, but it seems to be somewhat par for the course on Jeep forums.

This is probably the thing I hate the most about owning a Jeep. I had much higher hopes after nearly two decades on the Miata forum. I just guess there's something about Wranglers that attracts large numbers of a certain type of buyer.

shabbernigdo

I have a miata 97 NA and a jeep 2012 rubi. I think you are just uptight. Im on multiple forums for both vehicles and most of the people on both are just normal decent people. Yeah you have some that add nothing to the conversation and you do have some smart asses but thats just the internet for you.

Prodigy Performance

Yup. The Cd is a multiplier. Part of the confusion of comparing the Cd of the Jeep to the Cd of a motorcycle is that the Cd is only a representation of the shape, but not the size. So the shape of a motorcycle is less aerodynamic than a Jeep. But the Jeep also has a much larger frontal area, which is also a multiplier in the formula. The combined multiple of frontal area and drag coefficient is the correct way to compare the aerodynamics of different vehicles, and is referred to as the "CdA".

Here's a list of CdA values for many motorcycles (in m^2): Motorcycle CdA Values

And this page has Cd, frontal area, and CdA values for many cars (in ft^2): Vehicle Coefficient of Drag List - EcoModder

There's a soft top TJ Wrangler listed there with a CdA of 16.45 ft^2, which comes out to about 1.53 m^2. COmpare that to the CdA of the motorcycles.


Also, the power of aerodynamic drag is proportional to the CUBE of the speed; not the square. It's the force of aerodynamic drag that is proportional to the square of the speed. Revisiting your example of 75 mph vs 55 mph, it takes about 86% more force and 154% more power to maintain 75 mph vs 55 mph.

https://en.wikipedia.org/wiki/Drag_(physics)#Power

~Jeff

mr72

Thanks for the correction!

Lower highway speeds are an important key to good highway MPG in most cars, and particularly the Wrangler. There are rare exceptions such as if the lower speed requires a downshift and the lower gear puts the throttle position and rpm in a range where the engine's computer runs more enrichment or runs in open loop. I doubt this is the case for a JK especially with the Pentastar since it has abundant [enough] torque at very low rpms to sustain even pretty low speeds like 40mph in 6th gear (manual).

Back when we had a Honda Element, it would get nearly 30mpg on the highway if you kept under 60mph but barely above 20mpg at avg. 65mph. It can really make a huge difference.