For the last couple of years I've been using someone else's "streamer" video as the reference to comments about the hood scoop being a 'ram air'-type of intake on the SRT-10's. It all seems legit, but I still had questions. I recently purchased a digital anemometer (wind speed measuring device). I'll be using it in the coming weeks to test how much air *really* comes in through the hood scoop. I'll also use it to test other areas of the truck. I added an 8' extension cable to the anemometer and installed it earlier tonight. All is working fine and some baseline testing will happen this coming week. I plan on using video whenever possible. Here are some shots of the installation.... Attached to the scoop grille via 1/4-20 bolt and a zip tie as a backup: (not my favorite look, but....) Under the hood it looks like this: Close-up: Here you can see the extension wire coming in from under the hood and its temporary route: Display mounted on the dash (via velcro): I did a quick check to make sure everything was working properly: If I can get the video camera mounted properly, it should show me both truck speed and anemometer speed (intake air speed). In theory, if the scoop does 'ram air', the anemometer speed should be much higher than the truck speed. We shall soon see. :grin:
This is the bomb!!!opcorn:opcorn:opcorn::worthy::thanks::band::headspin: Can't wait to see the results! Again, thanks to Kevan for dreaming up this stuff. "Kevan Da Vinci":smart:
Why would you expect the air speed at the front of the "ram" intake to be higher than the truck speed?
Thankfully, I said "theory". :grin: For a 'ram air' effect to take place, the air should be traveling slightly faster than the vehicle speed. The air is 'rammed' into the intake, thus the name. Took some photos of some quick testing today. Get ready!!!!
Cool tool, I have one, works pretty good. But I think your gonna be a tad suprised with your findings based on your hypothesis. Good luck.
Considering the aerodynamics (or lack thereof) with these trucks, I wasn't really surprised with the results. Here we go..... BASELINE (0 mph truck/ 0.0 mph anemometer) 60 mph (60 mph truck / 23.9 mph anemometer) 75 mph w/cruise control set (75 mph truck / 32.2 mph anemometer) More testing to come.
Badass Kevan. Wouldn't the testing be a bit more effective if the SRT10 badge was not in the way? For all fairness anyway...
Sure. Though I might do that on Keith's new SRT-10 bumper. He doesn't have any obstructions behind those lower grilles (no brake ducts on his 4x4), so attaching it would be considerably easier. I plan on testing in a variety of locations. Next up is over by the CAI. If anyone has requests, or wants to strap it onto their vehicle, let me know. I've got LOTS of zip ties. LOL I don't think removing the "-" and the "1" are going to get me another 40 mph. :grin: If the initial test results were closer to actual truck speed, then I think it would warrant a non-badged intake grille. Jeez....calling it an intake now seems so wrong. HEAT VENT. That's better.
You may be thinking optimistically. They might call it "ram air" because it's air that's just passed over the hood of a Ram truck :bigwink: Actually I think "ram air" is just a loose term to mean that you will benifit from the vehicle's forward movement through the air. So if the intake was behind something so that the air was still whether the truck was moving or not then it would be all vacuum from the engine. With ram air if the truck is moving you get some benefit from that and there would be less vacuum at the intake. So measuring air speed might not be the right thing. If you are measuring air speed then it should take some funnel or wing effect to get a speed higher than the vehicle speed. So measuring at the grill where you are now the only increase in wind speed over vehicle speed might come from forcing the air up over the front edge of the hood (like the top of an airplane wing). Since it's lower than vehicle speed my first guess would be the air stream is coming over the front edge of the hood, continuing up, and then mostly over the hood scoop too. The hood scoop might be down under the main air flow and in slower moving "trapped" air or turbulence. Haha. You need to go the extra mile and put a couple of smoke nozzles on the leading edge of the hood so you can see what's happening. Another thing to try would be to put the anemometer right at the top of your windshield just before the roof line. I'll bet you'd see air speed higher than vehicle speed there. By the way, you did make a pass in both directions right?
Gotta give you points for cuteness. LOL If you listen real close, you can hear all the WS6 owners groaning at your humor. :grin: True. The general assumption (and we all know how dangerous those are) is that if it looks like a "scoop", it must be a scoop. If it were any sort of functional intake at all, wind speeds would be MUCH closer to actual truck speed. In the case of the SRT-10 trucks, it's not a scoop. It's a vent. The general shape of the 'scoop' tells us that it's attempting to be (but not actually working as) a funnel. The streamer tests from before show us PLENTY of turburlence on the 'tray' area of the scoop. So I knew that putting the anemometer in front of the grille wouldn't show me much. It needed to go behind...to see if anything happened *after* the turbulence in front. If you look closely at the pictures, you can see the white 1/2" spacer I made to mount the anemometer remote. This places the unit just off the inside face of the grille. The vent is obviously grabbing a LITTLE air and bringing it in; the speed tells us that, but also check out the temp (115F at idle; 80F-ish at speed). At least what it is bringing in is slighlty cooler than the ambient outside temp (around 93F today, with 70% humidity). The cause here is simple aerodynamics and their incorporation into the design of the truck. Take a look at the Viper coupe. It has a NACA-type duct at the front of their hood, approx. the same distance from the leading edge as the SRT-10 trucks. The difference is, aside from duct shape, aerodynamics. On the Viper cars, that is their ONLY intake, and it kicks ass. With the trucks, the aerodynamics don't allow the use of that hood opening as an intake, and with the bigass face there are more options for getting air to the TB. Sure. I'll test it up by the edge of the roof if you want. I doubt it will get past the truck MPH though. Smoke nozzles? Send 'em on over. :grin: This isn't for Guinness, so....no. BTW- did you know that most major colleges offer MASTERS programs just for Computational Flow Dynamics (CFD)? I'm not sure I'm at that level of geekdom quite yet. Not far off, but I've got a little ways to go. :grin:
The bed's a pretty big place, Roy. Be more specific. Also: - With tonneau on or off? - With wing on or off?
Intested in how much difference the tail gate up and down makes on drag...seems to me that an open tail gate would allow for more aerodynamic assistance...but that might sacrifice down pressure...would be interested in wind velocity mid bed, with tail gate open and tail gate closed...if any difference at all...
I'm sure you know this already Roy, but I'll put it up for others that are new to this vehicle: There are (2) wings available for the SRT-10's. I refer to them as "Gen.1" and "Gen.2." Gen.1 part number: 5JR31TZZAB Gen.2 part number: 5JR31TZZAC Gen.1 came on all 2004 models and on the 2005 models without the factory tonneau cover. Gen.2 came on the 2005 models with the factory tonneau cover and all 2006 models. The shape/profile of the wings is also different: Gen.1 is designed to work (provide downforce) with the tailgate in the up/closed position. Gen.2 is designed to work (provide downforce) in conjunction with the tonneau cover. They are easy to spot as well: Gen.1 is longer (LOA) and has no center support on the underside of the wing. Gen.2 is shorter (LOA) and has a center support that mounts to the tonneau cover. Both Gen.1 and Gen.2 are manufactured by Roush. They are high-density foam-filled 1/4" thick ABS plastic.
What?!?! You didn't see the MythBusters test on this? Turns out that tail gate UP is the most efficient. More efficient than tail gate down, no tail gate, and all but one of the nets or open bar types of tail gate replacements. One semi-open tail gate replacement (I think it sort of looked like a very large weave of flat straps) was pretty close to as good as the stock tail gate. [edit] I guess the particular mesh tail gate they had was 5% more efficient. See below. Seems that the tail gate acts as a sort of baffle creating a "roll" of slow moving trapped air in the bed. Subsequent air passes over this more smoothly. Without the baffle back there it's just a bunch of turbulence as the air comes off the roof line. Something like that. Original: http://kwc.org/mythbusters/2005/11/episode_43_seasickness_cures_f.html Re-visited: http://kwc.org/mythbusters/2006/12/episode_64_more_myths_revisite.html
27,359 YouTube vids of the Kari ButtScan episode..... But none of 43 or 64. Bunch of pervs online. :grin:
Thanks for posting this Kevin...I had read an article several years ago about hood scoops..the summery of it was that most scoops created a vacuum and were usless.....this gives me more reason to change my setup on the Roe and duct it to the stock airbox. I was thinking of modifying the stock box to use a cone type filter....also might add a hole to the front of the box to take air in from the grill in addition to the stock vent in the fender... That begs a question..can you test the right side grill area for wind speed?
