Wild air dam claims

[CaseyJones88]

So I’ve read multiple forums. Seems to be full of by the book sallies making claims the air dam on front bumper makes a TWO MPG DIFFERENCE. This has to be the most ridiculous thing I’ve read in 2019. If front bumper air dams made that much of a difference every vehicles underbody would be covered in plastic.


Is there any credit to this claim or is it just a bunch of idiots talking ****. I could see a mpg difference of maybe .1 Maybe even .2 but 1.5-2. That’s ******* ridiculous

 

[Tim Garceau]

2 miles per tank I’d certainly believe.

 

[CaseyJones88]

2 miles per tank I’d certainly believe.

Yeah that’s more believable

 

[carlcochran79]

I do not know about the ram but when I was on the titanxd forum people who removed it claimed a 1-1.5 mpg loss. Never did that myself when I had a titanxd and have not removed it from my ram so I cannot say one way or the other myself.

 

[Jessica Smith]

Chevy Colorado ZR2 Crew cab 4x4 3.6L is 18mpg highway.

The LT Crew cab 4x4 3.6L is 24mpg highway.

Supposedly one of the big reasons for the huge drop in highway fuel economy with the same powertrain is reduced aerodynamics, since to increase approach angles they ditched both the front rake of the regular LT and the ground hugging side skirt.

Not only does the air damn deflect air from going on the unaerodynamic underbody, but I think a big deal may be the front wheel wells that can act as parachutes at speed if it lets the air from underneath flow up in there.

I got up to 30mpg on the highway with a fifth generation Corvette with its low frontal profile and air dam that would constantly scrape the ground and have to be replaced every couple of years, when the same LS1 in a Trailblazer SS would be lucky to hit 20mpg. Aerodynamics are a huge deal at highways speeds, especially when you consider that the average American drives faster on the highway than the 45mph average speed the EPA tests at.

So depending on the speed guys like to cruise at on the highway, could definitely be the case, since drag increases exponentially with speed.

 

[MarshRam]

I wouldn't be surprised if it is true. All the constant changes in design of vehicles can't just be about appeal, aerodynamics for improved mpg has to be in play as well.

If it is true, then I would think as soon as you modify the suspension or even change the size of tires you change the stance/aerodynamics and it wouldn't matter much at that point.

Someone with a stock truck put it to the test and let us know!

 

[CaseyJones88]

Chevy Colorado ZR2 Crew cab 4x4 3.6L is 18mpg highway.

The LT Crew cab 4x4 3.6L is 24mpg highway.

Supposedly one of the big reasons for the huge drop in highway fuel economy with the same powertrain is reduced aerodynamics, since to increase approach angles they ditched both the front rake of the regular LT and the ground hugging side skirt.

Not only does the air damn deflect air from going on the unaerodynamic underbody, but I think a big deal may be the front wheel wells that can act as parachutes at speed if it lets the air from underneath flow up in there.

I got up to 30mpg on the highway with a fifth generation Corvette with its low frontal profile and air dam that would constantly scrape the ground and have to be replaced every couple of years, when the same LS1 in a Trailblazer SS would be lucky to hit 20mpg. Aerodynamics are a huge deal at highways speeds, especially when you consider that the average American drives faster on the highway than the 45mph average speed the EPA tests at.

The biggest reason for the drop in fuel economy is the gear ratios....secondly is the bigger tires, heavier wheels, lift, weight, the very last thing is aerodynamics lol.

I’ve had exact vehicles with 4.10 and 3.55. Let me tell you the 3.55 got about 3 mpg better on the highway.

The last thing about the zr2s fuel economy is its little piece of plastic in the front.

Lastly. You do realize the shape of a truck isn’t aerodynamic. You’re talking about a 3” lip like it turns the truck into a Ferrari. You’re probably the type of guy who thinks putting a spoiler on your tailgate would give you better mileage too. Try it.

 

[CaseyJones88]

I wouldn't be surprised if it is true. All the constant changes in design of vehicles can't just be about appeal, aerodynamics for improved mpg has to be in play as well.

If it is true, then I would think as soon as you modify the suspension or even change the size of tires you change the stance/aerodynamics and it wouldn't matter much at that point.

Someone with a stock truck put it to the test and let us know!

Man the constant change is about adding .001 mpg to the vehicle. They’ll do whatever to get .5

 

[Jessica Smith]

The biggest reason for the drop in fuel economy is the gear ratios....secondly is the bigger tires, heavier wheels, lift, weight, the very last thing is aerodynamics lol.

We're talking about a vehicle with an 8-speed transmission, meaning it has top gears that are capable of crazy overdrive regardless.

Vehicle weight plays a huge roll in stop and go traffic, but is pretty insignificant for steady state cruising, where almost all horsepower is dedicated to fighting drag. Its why a bicyclist can go highways speeds when tailgating a semi-truck to block the wind, and why in NASCAR they can whip around a vehicle in front of them as if they are standing still even though their horsepower is almost identical.

Lastly. You do realize the shape of a truck isn’t aerodynamic. You’re talking about a 3” lip like it turns the truck into a Ferrari. You’re probably the type of guy who thinks putting a spoiler on your tailgate would give you better mileage too. Try it.

Spoilers aren't usually intended to decrease drag coefficient but increase rear downforce, and so if anything tend to increase drag for the sake of high speed handling. Manufacturers spend a lot of time and a lot of money with trucks in the windtunnel, and they are surprisingly aerodynamic. Mercedes proved without a doubt that you can even make a seemingly square brick shape aerodynamic with their Bionic concept van that had lower drag than any sports car on the market.

 

[huntergreen]

I have read theead posts from guys who off-road with their Rams and have ripped off the front air dam. They did report dignificans mpg drops on the hwy 2 mpg loss does sound reasonable, but I don't recall the actual numbers.

 

[indept]

They don't just dream this up, it's measured very accurately. That said, it IS under ideal conditions so it may not be easy to duplicate in real world conditions.

 

[CaseyJones88]

We're talking about a vehicle with an 8-speed transmission, meaning it has top gears that are capable of crazy overdrive regardless.

Vehicle weight plays a huge roll in stop and go traffic, but is pretty insignificant for steady state cruising, where almost all horsepower is dedicated to fighting drag. Its why a bicyclist can go highways speeds when tailgating a semi-truck to block the wind, and why in NASCAR they can whip around a vehicle in front of them as if they are standing still even though their horsepower is almost identical.



Spoilers aren't usually intended to decrease drag coefficient but increase rear downforce, and so if anything tend to increase drag for the sake of high speed handling. Manufacturers spend a lot of time and a lot of money with trucks in the windtunnel, and they are surprisingly aerodynamic. Mercedes proved without a doubt that you can even make a seemingly square brick shape aerodynamic with their Bionic concept van that had lower drag than any sports car on the market.

I’m aware of a spoilers purpose. I drift and autocross. I was using it as an example to this ridiculousness claim that an air dam gives you 2mpg.

Overdrive and transmission gears don’t account for an axles gear ratio. The vehicle i mentioned had the same transmission and the lower 4.10 ratio was much worse at highway economy. It’s common sense fact that the higher your gear ratio the better highway mpg you’ll get.



What about the rams that don’t come with such a low front end. They get the same mpg as one like mine with heavy rake. Their air dam isn’t bigger to account for the ride height difference

 

[CaseyJones88]

I have read theead posts from guys who off-road with their Rams and have ripped off the front air dam. They did report dignificans mpg drops on the hwy 2 mpg loss does sound reasonable, but I don't recall the actual numbers.

90% of those guys haven’t recalibrated their Speedo so their numbers are pointless.

 

[CaseyJones88]

They don't just dream this up, it's measured very accurately. That said, it IS under ideal conditions so it may not be easy to duplicate in real world conditions.

I’d pay someone 1000$ to see a direct quote from a dodge engineers tests showing the front air damn gives the truck 2mpg. Do you realize how hard it is to gain 2mpg.

 

[huntergreen]

90% of those guys haven’t recalibrated their Speedo so their numbers are pointless.

Simple solution is to remove your sir dam and take a ride on the hwy.

 

[KeithDVR]

The one thing that I can say Did give me an increase of 2MPG was changing tires. I have a '19 Rebel and going from the stock tires to the 20" wheels and tires did it. Of course the damn wheels have a list price of $400 each! Last week I made a road trip and I averaged 20.4 MPG. Full info that was highway not breaking 75 with the cruise control on and no done with the coffee stops and probably 500lbs in the bed under the cover. The only other change was shifting to Royal Purple oil and filter.

 

[Jessica Smith]

Overdrive and transmission gears don’t account for an axles gear ratio.

They certainly can, at least in theory. When you have a whopping 8 gear ratios to play with, you can afford to have multiple overdrive ratios. As such, if vehicle A is lugging the engine at 1500rpm on the highway in 7th gear and vehicle B is lugging the engine at 1500rpm in 8th gear because of the different final drive, the end result is both are operating at the minimum RPM the engine is capable of running at for that speed.

If you watch the video I linked, the engineer responsible for the team that designed the aerodynamics on the 2019 Ram, Marc Babich, listed the airdam as one of the top three tools they use to fight drag and improve fuel economy, so if you still don't think they are important, I don't think I would be able to convince you otherwise.

And just to clarify, I'm not saying that 2mpg is going to be the case if you're stop and go traffic and what not, but since drag increases with the square of speed, if you drive quick on the highway (like I do on trips to Dallas from Houston), a seemingly small aero change can make a big difference since its an exponential growth factor.

 

[CaseyJones88]

The one thing that I can say Did give me an increase of 2MPG was changing tires. I have a '19 Rebel and going from the stock tires to the 20" wheels and tires did it. Of course the damn wheels have a list price of $400 each! Last week I made a road trip and I averaged 20.4 MPG. Full info that was highway not breaking 75 with the cruise control on and no done with the coffee stops and probably 500lbs in the bed under the cover. The only other change was shifting to Royal Purple oil and filter.

You gained 2mpg from 17” rim to a 20” rim?

 

[CaseyJones88]

They certainly can, at least in theory. When you have a whopping 8 gear ratios to play with, you can afford to have multiple overdrive ratios. As such, if vehicle A is lugging the engine at 1500rpm on the highway in 7th gear and vehicle B is lugging the engine at 1500rpm in 8th gear because of the different final drive, the end result is both are operating at the minimum RPM the engine is capable of running at for that speed.

If you watch the video I linked, the engineer responsible for the team that designed the aerodynamics on the 2019 Ram, Marc Babich, listed the airdam as one of the top three tools they use to fight drag and improve fuel economy, so if you still don't think they are important, I don't think I would be able to convince you otherwise.

And just to clarify, I'm not saying that 2mpg is going to be the case if you're stop and go traffic and what not, but since drag increases with the square of speed, if you drive quick on the highway (like I do on trips to Dallas from Houston), a seemingly small aero change can make a big difference since its an exponential growth factor.

Well my 11 doesn’t have an 8 speed first off.

Nor did the Jeeps I’ve had.

I guess I’ll have to remove mine to really find out. But there are so many factors. What if there’s usually a head wind and then the day I try it without theres no wind. Or even a tail wind

 

[Jessica Smith]

Well my 11 doesn’t have an 8 speed first off.

Nor did the Jeeps I’ve had.

I guess I’ll have to remove mine to really find out. But there are so many factors. What if there’s usually a head wind and then the day I try it without theres no wind. Or even a tail wind

Well, we were talking about my example of why the ZR2 loses so much highway fuel economy, even more according to real world users that drive spirited than the relatively low speeds the EPA tests at on the highway, and that specific example has only a V6 and 8-speeds to work with.

Its a different story from back in the day where you only had say four gears so the final drive made a huge highway difference.

Yeah, I agree, you'd have a hard time being accurate in a non-scientific setting. If you have a standard commute, all I could suggest is to do the test over a long period of time and log it on fuelly.com. If you did 5K miles with it and 5K without it, you could be pretty certain that environmental conditions would likely balance out. Otherwise, IMO, if the engineer that made the thing said its important, don't screw with it if you don't have to.