Mythbusters "tests" efficiency of dimples vs. smooth, and clean vs. muddy car

[shovel]

Originally Posted by RobertSmalls

I dunno, shovel, we do far better testing than they do. .

Sweet! Of golf ball dimples? Where?

[Christ]

Originally Posted by robertwb70

When they say stuff like this "I wonder how long it took them to spray that clay on" it's obvious they didn't watch it...

And there are other examples in posts here but you get the idea, sometimes you CAN tell.

So you're contextualizing that post based on something you still don't know, right?

I mean, you're assuming he didn't go get a drink during the part where they explained how the clay was applied.

Frankly, not everyone really cares about TV all that much, and chances are, several of the people commenting who you feel "didn't watch it", probably did, and just missed the bits and pieces you're going to focus on for proof.

Carry on, please.

Regardless of whether someone watched it or not, or whether the outcome could have been different, the tests are completely invalid. It's one of their worst works to date. There are entirely too many variables, and that just ruins it.

Guess what could account for 11% change in fuel economy? CROSS WINDS.

Oh, we never got any of that data, did we?

[Christ]

Originally Posted by Cd

If dimples really don't work, why did Audi, VW, and Lexus put them on the underside of their cars body panels ?
( Not being 'smart' with this question guys. I'm really sincere. I want to know why that they would go through all the trouble of adding them. )

Thanks

The theory was that, in addition to marketing, they would have been able to create a turbulent boundary layer on the underside of the car, which would act like a belly pan that would keep flow lower than the metal surfaces of the car's underside, essentially reducing the occurrence of under-body drag.

I dunno if it worked or not, I haven't seen any of the test data from it.

Oh - it also reduced in-cabin noise, because the thicker boundary layer acted like an insulator for noise.

[alohaspirit]

personally id watch it again. although honestly it wasnt that entralling. kinda ho-hum. curious if ill catch anything not touched upon here on the 2nd time around

Originally Posted by Christ

Oh - it also reduced in-cabin noise, because the thicker boundary layer acted like an insulator for noise.

shhhh. ive got a patent out on that.

Dyna-clay

[robertwb70]

Originally Posted by Christ

So you're contextualizing that post based on something you still don't know, right?

Yep, just like lots of others, this IS the internet after all...

I mean, you're assuming he didn't go get a drink during the part where they explained how the clay was applied.

Well when something I'm intensely interested in is on I make sure to NOT miss any parts, precisely so that when I discuss said interesting stuff I know what it is I'm discussing.



Frankly, not everyone really cares about TV all that much, and chances are, several of the people commenting who you feel "didn't watch it", probably did, and just missed the bits and pieces you're going to focus on for proof.

Oh I couldn't care less about TV, I believe it's the plague of modern society and should be re-named the "Idiot Box" and all the people that say the test wasn't rigorous enough or didn't apply the scientific method appropriately or whatnot , well it's TV what did you expect? an SAE quality study that could withstand peer review? I mean REALLY? it's just entertainment...

Carry on, please.

Aye, Aye captain

Sorry I couldn't resist, but I will from now on...

[Christ]

Doesn't that last part kind of defeat the purpose of your entire post?

I mean, first you want us to believe that the testing was accurate, and we should believe you because we "didn't watch the show", as you claim... but then you say "It's just TV" and "It can't stand up to peer review"... Contradictory, at best.

Forgive me if you never thought the testing was actually accurate, although that would lead one to believe you were only trolling to get a rise based on someone else's premise that we had commented on something we hadn't physically seen... is that the case?

Lastly, it's plainly irresponsible for Jamie and Adam to think that they should be able to get away with not properly applying the Scientific Method to a test that could have a result which would garner such enthusiastic fodder. Especially when said test is performed on a channel of TV which likes to keep the image of being a channel that one can learn from, or "Discover" new things. What have we "discovered" here? That MythBusters' quality has definitely gone down.

In fact, I'd venture to compare them to a gold digging woman. Sure, she'll cook, clean, take care of you, etc... get married to her, and it's out the window. She knows that she doesn't have to impress you any more, because she's married to you. The game changes.

It's the same way with TV. Do things that people like, and do them well, until you build a client base, then don't bother anymore. You'll get more clients from the first set's brainwashed opinions.

[robertwb70]

Originally Posted by Christ

I mean, first you want us to believe that the testing was accurate, and we should believe you because we "didn't watch the show", as you claim... but then you say "It's just TV" and "It can't stand up to peer review"... Contradictory, at best.

WHAT? maybe you could show me the part where I wanted anyone to believe anything?? Maybe you have me mistaken for someone else??

My original point was that if people don't know what they're talking about they shouldn't talk about it, and since I have no idea what you're going on about I'll shut up now.

[MetroMPG]

I finally saw the episode tonight.

I just posted this in the other thread on the same subject, but this one seems to have more meat in it, so I'm copying my message here.

(Too late to merge the 2 threads - would make a mess.)

Yes, some of what I copied below has been said in this thread already. Sorry.

-----

That was pretty darned entertaining!

FYI, you can view the video here: MEGAVIDEO - I'm watching it

When I saw the first test (dirt vs clean), I was sorely disappointed by their fuel measurement technique: note the fuel level in the sloshing tube by eye and mark with magnetic arrows!

I was relieved to see them ditch that method for the smooth vs. dimpled tests and opt for weighing the fuel cell each run.

Originally Posted by botsapper

The now famous 'dimples' car should be retested w/ ecomodders' test suggestions.... Any other suggestions?...

Mine are mostly about the testing methods, either things I saw and took issue with, or things they didn't show which leave big questions.

1) They need to do A-B-A. Return the car to its original state to see if the observed effect disappears. Admittedly not easy to put the dimple material back in and smooth it again, but they should have tried something.

2) It seemed to me they were relying on Jamie to hold the car's speed. That's a no-no! Need to remove the human foot from the most sensitive input in the experiment - the gas pedal. They should have used cruise control or some other speed control.

3) It's fair to assume weather conditions (temp, particularly) would have changed between the two tests - it would have taken some time to carve out those 1082 dimples. They didn't take that into account. (We don't even know for sure if they did it on the same day due to the magic of editing.)

4) We don't know whether the car was equally warmed up for all tests. (Equal engine coolant temp doesn't count.) We're talking full drivetrain temps, including tires.

Their results are also really big (% improvement), which ratchets up the skepticism a bit more. They claimed 26 mpg (US) for smooth vs. 29.65 for dimpled. A 14% improvement! Yikes.

(Actually they said 26-something MPG for smooth. Let's call it 26.5 MPG, and that makes the improvement 11.9% - still massive.)

Has anyone double checked their calcs?

(Yes, they have. Some duplication here...)

smooth clay:

10056 g to 9553 g gasoline
or 503 g burned
26 mpg (US) their figures

dimpled clay:

9450 g to 8972 g gasoline
or 478 g burned
29.65 mpg (US) their figures

Gasoline weighs 6.073 lbs per US gallon (says wikipedia). 1 pound = 453.59237 grams, so 1 gallon = 2754.7 grams.

smooth: 5 mi / 503 grams = 5 mi / 0.182597 gal = 27.38 mpg (US)

dimpled: 5 mi / 478 grams = 5 mi / = 0.173522 gal = 28.81 mpg (US)

That's only a 5.2% improvement by my calcs using their data. So their own calcs seem fishy too. Unless I just screwed it up. (Plausible!)

[MetroMPG]

Originally Posted by Cd

If dimples really don't work, why did Audi, VW, and Lexus put them on the underside of their cars body panels ?
( Not being 'smart' with this question guys. I'm really sincere. I want to know why that they would go through all the trouble of adding them. )

Good question.

From an aero standpoint, dimples don't make sense underneath the car. You can be pretty sure the flow underneath is already turbulent.

Could it be for structural stiffening to prevent otherwise flat panels from oil-canning?

Could it be for favourable acoustic properties?

Could it be a styling exercise that looks neat-o and gets the nerdy people excited? (proof: we're talking about it!)

Wouldn't it be great if we could actually ask the designers/engineers questions like these?

[Frank Lee]

That's only a 5.2% improvement by my calcs using their data. So their own calcs seem fishy too.

They must have attended the same school as the Truck Trend editors