Jeep Garage  - Jeep Forum banner
21 - 37 of 37 Posts

·
Registered
Joined
·
1,036 Posts
That would be amazing to get that kind of meage! So do you also have the 5.7? Were you running the air conditioner? Headwind/tailwind? Oh, Round trip, so it probably evened out.
Thanks for sharing.
Typical of the many trips we’ve taken in our ‘14 V8 is averaging 22-23 mpg on the highway in mixed traffic conditions. The 8 speed combined with the tall 3.09 rear ratio is great for mileage.
 
  • Like
Reactions: Guts

·
Registered
Joined
·
7 Posts
Cold Air Intake. Many people have heard of K&N aftermarket CAI systems. People install them and commonly report no improvement.

The theory is that colder air is denser and, therefore, will deliver more fuel/air mix to the engine. Sometimes hotter air can contribute to pre-detonation (knocking).
The cooler air may enable a "hotter tune" but at no level one could appreciate.

Also, the filter media employed is coarser and requires oiling to catch dirt. This oil, often over-done by amateurish mechanics, is known to foul sensors.
The consensus is that stock systems are best.
The factory's intake is often in the "coldest" location to begin with.

While aftermarket CAI is a Certified High School Boy Toy there'll always be the guy who lives in a hot climate and travels long distances who'll swear to a 40 hp increase.
You don't have to waste energy being skeptical of these things....just laugh at 'em.
I myself installed a AFe CAI on my 2011 did not get any more ponys but did get a little better MPG out of it so not a entire loss
 

·
Registered
2014 JGC Limited 3.6 V6 Alpine Sound, Deep Pearl Blue
Joined
·
47 Posts
Regarding warranty issues, that to me, is really a moot point, as my Jeep is already well beyond the warranty coverage.
Regarding the arguments that the manufacturer has already optimized the performance and economy of every vehicle they make, well, I am not as familiar with gasoline engines, but can say definitively that with diesel engines, that is simply not the case. I have seen considerable improvements in every diesel engine I have owned with the use of aftermarket tuners, exhaust systems, and turbochargers.
So what I am looking for, with all due respect, is some ACTUAL real-world experience having used some kind of device(s) to improve performance, either in terms of power gained, or mileage increases. I understand the reluctance of many of you to do anything to potentially void your warranty, and I respect that. But to project the supposition that anything you might do to your vehicle will be harmful is really not useful to me without also supplying observations from your experience.
Please don't misunderstand me, I value the input each of you have given! And I'm not trying to be harsh in my reply.
Thank you, and happy trails!
From what I get from reading all these posts...many are mixing performance with mileage. To get more performance you need more air. More air means more fuel. Ergo less economy. Warmer air will demand less fuel in order to maintain mixture ratios. Ergo better mileage. I stopped checking the mileage on my 2014 Limited. But I'll say this. I have a Saturn 2001. It gets 30+mpg when the temperature is hot. As soon as the season changes, and temperatures drop...even into the 70's and 60's...mileage goes into the dumper. There used to be a kit for throttle body engines that made the engine think the AC was on which told the ECU/ECM to make the mixture richer. As for the gimmicks sold on the Internet. I too researched them and many are nothing but empty plugs.
 

·
Registered
Joined
·
186 Posts
I've used the "Torque" App for my Android phone through a Bluetooth interface to the OBD2 jack on my prior Mercedes and Cadillac rides to read trans temp cuz they didn't have gauges. Only time they actively altered engine performance was the malfunction of a cheap interface. While I agree the manufacturers give you the best the law allows, this does not mean that you won't find something illegal which increases both your mileage and emissions. I got a gadget for the Mercedes called an O2 Simulator, made in Latvia, shipped from BC, that did the intended job.
 

·
Registered
Jeep
Joined
·
28 Posts
Check out what is called a Motor Minder. It is a small vacuum gauge that sets it's self to the highest vacuum recorded. You hook into the breather system close to the intake for the engine. It will tell you if you have any restrictions in the system. Every diesel truck I drove had one. My 07 Jeep with the 4.7 was fine until I put my foot into it. Then recorded high vacuum. It was in the cold air intake behind the front grill. Made some modifications ( cut holes) and fine now.
 

·
Registered
03 WJ, 4.Slow, 3" IRO
Joined
·
471 Posts
To get more performance you need more air. More air means more fuel. Ergo less economy. Warmer air will demand less fuel in order to maintain mixture ratios.
Not necessarily... a more efficient combustion gives more power out of less throttle which usually means you will have better mileage.

Before my father passed away, he was one of the leading experts in the world on flow dynamics. I am by no means anywhere near an expert, I have learned a couple of things helping him on some of his projects, not to mention dinner table conversations. His expertise did help us considerably building race cars.

There are a dizzying array of factors to consider when designing and building an efficient engine, only part of that is intake and exhaust flow. Plain old physics has a lot to do with it. Valve and ignition timing, compression ratios bore and stroke, etc. Then there are politics, vehicle styling, comfort and let's not forget environmental factors such as temperature humidity altitude, etc. And that is all before you even get rolling where you now have to figure in aerodynamics, surface conditions, drivetrain gear ratios, tire size, and the air pressure in them...

Improvements to fuel mileage and power delivery can be made in many different areas. Leaner fuel mixtures and advance timing can give you better fuel economy under the right conditions. Everything comes at a cost. Better fuel mileage under these conditions come at the benefit and cost of higher combustion temperatures in the engine. Higher temperatures create more expansion force on the pistons causing more power at the cost of pinging/knocking damaging piston, cylinder walls and wrist pins. Higher combustion temperatures have the side effect of creating NOx. This is a big political no no.

CAI can help reduce the overall combustion temperature, but I have not seen a commercial one design correctly to give exceptional intake flow. 30+ years ago a computer chip would improve power and economy but most manufacturers have taken advantage of that now.
 

·
Registered
Grand Cherokee
Joined
·
4,798 Posts
Power=Temp(out)-Temp(in)
Temp(out) is limited to a max that will damage the engine
The smaller the temp(in) the bigger difference in temperature, or heat, or power....

You're at part throttle while you cruise, the throttle plate reduces pressures and you have a gauge vacuum in the intake manifold, decreasing the air density.... ...This is how you modulate power in a gas engine, by modulating the amount of air going in the motor... ...if the same volume of air creates more power than you need, you'd reduce the power more by closing the throttle plate more and creating more of a vacuum....

Its making the most power from the fuel used that gets your efficiency.... Advancing timing gets you more power without using more fuel, up to the point it causes pre-ignition or detonation, and you need to have a bit of a safety margin, cause the detonation will damage your motor and conditions to change the most ignition advance possible to detonation can cause detonation in an instant as conditions change..... ....cooler air could do it also....

Still the amounts of change a CAI can produce, I don't think you'd see much of a difference, it depends on the product and vehicle....

The problem with running lean is that it increases emissions, the manufacturers could double the mileage of their engine overnight, almost overnight, if they did not have to meet emissions.... ....but they do have to meet emissions...

OBDII is a standardized protocol, its not standardized software. Most of these devices are scams, like they said the chips are just performing a light show of the LED's. Another factor against them, is how they claim they work with every vehicle. How? Are there standardized OBDII commands for advancing ignition timing followed by every manufacturer?
 

·
Registered
Jeep
Joined
·
54 Posts
Besides a good tune, lighter wheels and tires will give the biggest mpg and performance gains.

You can go the cheap way with stock JGC 17x8 and stock sized tires, but your rig won’t look as good.

You can go the more expensive 20x10 srt8 5-ten forged wheels which are the lightest stock 20” wheel. This stock wheel tire combo will still be a little heavier than the 17x8 wheels and tires, but it will look much better.
 

·
Registered
Joined
·
182 Posts
when I do my long trips, I tie a helium balloon to my right foot, keep an eye on the road ahead and leave an appropriate length of time for the journey.

These 'mods' to behavior result in a massive boost to economy, on one trip we did over 500 miles and still had a 1/4 tank when we got home.
 

·
Registered
Joined
·
1,116 Posts
With all the oxygen sensors and other monitors throughout the engine all hooked into the computer, wouldn't a check engine light come on with a lean cylinder or cylinders? I believe the engines of yesteryear would self destruct without warning(other than pinging), but I highly doubt today's vehicles would be engine light free until meltdown with any fuel saver device.
 

·
Registered
Grand Cherokee
Joined
·
4,798 Posts
You don't have to lean out the mixture to increase mileage.

You are correct, the EFI maintains stoichiometric A/F ratio for emissions, you can't change that, the O2 sensors are narrow band and thus can't really accurately measure anything except the switch over across stoichiometric A/F ratio. If you figured out some way to run leaner, you'd be violating emissions, tripping CEL's and codes and possibly burning up Catalytic Converters....

But, if you can increase the amount of power the engine produces per amount of fuel consumed, then you'd use less fuel for the same amount of power demand. Things like advancing ignition timing, volumetric efficiency or getting colder air into the engine will produce more power for the same amount of fuel consumed, thus vice-a-versa for the same amount of power needed to cruise down the road you'd being consuming less fuel. Still the same A/F ratio, just the engine at less throttle to produce the same amount of power as before, and consuming less fuel to make that same amount of power.

You typical CAI doesn't drop the temperature that much, at least not enough to make massive improvement in power/mileage, advancing ignition can be dangerous, the system already tries to use the most advance ignition timing possible and retarding it for safety if the knock sensors shows its too advance. The OEM setup has a bit of safety margin built in, so the most you can advance it is the couple of degrees that OEM backed off as a safety margin, and that comes with a risk since you're eliminating that safety margin built in.

Also keep in mind, the typical EFI uses narrow band O2 sensors that can only provide feedback when the engine is suppose to have an Stoichiometric A/F ratio. So times the engine has to run richer, warm-up and Wide Open Throttle, the system has to run open loop with no feedback from the O2 sensors. Also the OEM's typically set the A/F richer than needed as a safety margin. So thing like volumetric improvements, headers, ported intake, cams, etc... would lean out that richer than necessary A/F at WOT and produce more power. But don't forget the system is adaptive, and applying correction factors to the fuel and ignition tables that also apply during WOT.
 

·
Registered
03 WJ, 4.Slow, 3" IRO
Joined
·
471 Posts
Knock sensors are not just there to protect the engine from damage caused by pre-ignition/detonation but for emissions as well. NOx is produced at higher combustion temperatures. Those temperatures are just above where knock starts to occur. More power can be produced (thus better fuel mileage) from advanced timing but at the cost of increased pollution and longterm engine damage.

If you were just looking to increase fuel mileage, higher octane fuel burns at a slower and cooler rate, reducing engine knock. This rings out more energy from the fuel and increases mileage. If you're wanting to increase fuel mileage for economic reasons, at $5+/gal, its probably not worth the extra money.
 

·
Registered
Joined
·
1,116 Posts
What is the best a person should expect to get with combined driving with these Hemi's? I can't get any better than 18-19 on paper and 20+ on the computer lie-o-meter. No hard throttle, mostly highway with some city.
 

·
Registered
Joined
·
1,036 Posts
Knock sensors are not just there to protect the engine from damage caused by pre-ignition/detonation but for emissions as well. NOx is produced at higher combustion temperatures. Those temperatures are just above where knock starts to occur. More power can be produced (thus better fuel mileage) from advanced timing but at the cost of increased pollution and longterm engine damage.

If you were just looking to increase fuel mileage, higher octane fuel burns at a slower and cooler rate, reducing engine knock. This rings out more energy from the fuel and increases mileage. If you're wanting to increase fuel mileage for economic reasons, at $5+/gal, its probably not worth the extra money.
Higher octane can be beneficial IF the vehicle is programmed to take advantage of the higher octane. As the Jeep owner’s manual says: using premium is not recommended nor beneficial with the Pentastar or non-SRT HEMI.

There must be some truth to this - after experimenting with several tanks of 87, 89 (recommended for the HEMI), and 93 octane I could tell no difference in performance or mileage with the 93 octane.
 

·
Registered
Joined
·
1,116 Posts
Higher octane can be beneficial IF the vehicle is programmed to take advantage of the higher octane. As the Jeep owner’s manual says: using premium is not recommended nor beneficial with the Pentastar or non-SRT HEMI.

There must be some truth to this - after experimenting with several tanks of 87, 89 (recommended for the HEMI), and 93 octane I could tell no difference in performance or mileage with the 93 octane.
Good to know. I only use 89 unless it's not available then I splurge for 91 or 92.
 
21 - 37 of 37 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top