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HiHo, that looks real good. I've thought about that but in the end it was a lot of work for potentially no huge benefit. It is a cool idea.
Instead I went with the "standard" fender setup using cast aluminum pipe and 4" aluminum pipe. Price wise I could have paid for a K&N setup, but with my custom radiator, I wasn't confident the K&N would fit.
Biggest Issue I had was that I needed to make a tubular front bumper support. Since mine is a DD, I don't feel great about getting rid of the OEM bumper support.
I got ya on the bumper support. Burkhart makes a really nice one for our cars that still has good protection. That's what i have.
A 4" tube does me no good with a 102 tb. The id of the tube is smaller than my tb. I wanted something larger with big area. I am going to attach it to the front bumper somehow.....haven't got that far yet. If everything works out as i expect i could possibly see positive manifold pressure at speed.
Thats what I'm saying. I agree with you. The depression creates drag.
My question is that earlier in the thread, people where saying that a complete flat chop off the rear of the car would actually product a force acting on the car in a forward direction. Thats what I don't understand. A depression or low pressure area is not going to push the car forward.
Nothing is propelling it forward. The arrow in the diagram is only depicting turbulence.
I got ya on the bumper support. Burkhart makes a really nice one for our cars that still has good protection. That's what i have.
A 4" tube does me no good with a 102 tb. The id of the tube is smaller than my tb. I wanted something larger with big area. I am going to attach it to the front bumper somehow.....haven't got that far yet. If everything works out as i expect i could possibly see positive manifold pressure at speed.
I thought you needed to go some ridiculous speed to ACTUALLY see a ram-air effect. Basically a speed faster than a "stock" fbody can even go lol.
I hear anything above 95+ kPa is a fairly efficient intake setup. In terms of a efficient design to get cold air, a front breather seems to take the cake.
Now you just need to build a properly made heat extractor hood to allow the air to pass through the radiator and out the hood. That will be kickin-wing.
Something like this (no idea if this is the correct location or not)
Why is my brain not understanding how the depression (low pressure area at the very back of the car) is going to provide a force to move the car forward. I don't study aero much, but conventional wisdom says that a depression would pull the car backwards, especially with the high pressure building up at the front of the car.......
What am I missing?
I'm totally with you here, the GM engineer specifically said that the bubble, if done right, is pushing the car. He showed the back of the Tahoe in an ANSYS model and red was high pressure pushing the car, blue was low pressure pulling or dragging the car back, and there was some red pushing the car. I didn't want to sound like an idiot questioning him at the time, but now I really regret not asking him to expand on how the NET force on the back of the car could ever possibly be positive, in my mind even if there are areas of positive, there had to be more areas of negative, creating a net loss or drag. The way (if you drink the coolaid and go with it down the rabbit hole) that I picture it is that the bubble is sitting there spinning, and air is going over the bubble, and the edge of the bubble touching the car is high pressure because it's gathering air as it goes over the bubble and spins, allowing the bubble to push on the car. There must be some critical size of the bubble, like it can't be too big or too small, maybe it has to be as long as it is tall, so it's a perfect sphere. And maybe as the air goes over it, it has to be moving forward-back, rather than being sloped.
All I know is he said there's high pressure areas on the back caused more on the hybrid with the squared off c pillars than the standard round c pillars. This is another time that I really wish there was some gearhead GM engineer on this forum that could read this and go meander over to another guy's cubicle and ask for us.
Side note: I just bought a 2002 c240 Mercedes, that little boxy ****** has a cd of 0.27. I wonder if it has to do with the squared off trunk.
Nah.....you should be able to feel even a ok system at 80mph or so.
For instance opening up my stock ss hood and sealing it to the oe airbox was worth a solid 1mph for me in a back to back test.
You already know this but gonna put it out there for others that believe "ram air" doesn't actually exist.
Force of AIR at 100mph (sea level) is about 0.17 psi with no pressure differential. Doesn't sound like much but its enough to knock out a window or a poorly designed structure. Car intake has negative pressure so the effective pressure differential increases thus forcing (ramming) more air into the chambers.
Front breather Camaros need a sealed intake to front bumper to take effect. It becomes a matter of maximizing frontal area of the inlet, building a sort of bulge to allow air to "stack" into the chamber to pressurize then transition down to whatever tube, throttle, or carb. Interesting misconception is being able to "funnel pressure" which flat out does not happen.
Weird things happen with stagnation and stall. There is still quite a bit of very complex physics to consider. Even Pro Mod guys differ opinion on hood scoop design, some use closed scoop that feed 100% of intake air and some have an opening in the rear to let airflow pass through to minimize stall effect.
A front breather would get my attention more if I started to road race or drag race. But autocrossing under 50mph I don't see will be worth the time/effort.
OP, you plan on doing any of these mods discussed? Meaning altering the rear end shape?
A front breather would get my attention more if I started to road race or drag race. But autocrossing under 50mph I don't see will be worth the time/effort.
For sure, absolute overkill for autoX. Really the bottom breather setup when sealed air tight has proven to be very efficient and does produce positive manifold pressure at speed. Cold air from below, sealed for positive pressure at speed, and still uses factory design with extremely short piping (throttle response for autoX).
I'm totally with you here, the GM engineer specifically said that the bubble, if done right, is pushing the car. He showed the back of the Tahoe in an ANSYS model and red was high pressure pushing the car, blue was low pressure pulling or dragging the car back, and there was some red pushing the car. I didn't want to sound like an idiot questioning him at the time, but now I really regret not asking him to expand on how the NET force on the back of the car could ever possibly be positive, in my mind even if there are areas of positive, there had to be more areas of negative, creating a net loss or drag. The way (if you drink the coolaid and go with it down the rabbit hole) that I picture it is that the bubble is sitting there spinning, and air is going over the bubble, and the edge of the bubble touching the car is high pressure because it's gathering air as it goes over the bubble and spins, allowing the bubble to push on the car. There must be some critical size of the bubble, like it can't be too big or too small, maybe it has to be as long as it is tall, so it's a perfect sphere. And maybe as the air goes over it, it has to be moving forward-back, rather than being sloped.
All I know is he said there's high pressure areas on the back caused more on the hybrid with the squared off c pillars than the standard round c pillars. This is another time that I really wish there was some gearhead GM engineer on this forum that could read this and go meander over to another guy's cubicle and ask for us.
Side note: I just bought a 2002 c240 Mercedes, that little boxy ****** has a cd of 0.27. I wonder if it has to do with the squared off trunk.
Very interesting for sure. Probably a very minor amount. But those guys are looking for tenths of a mpg so there probably is some weird phenomenon to make tgat happen.
Originally Posted by imma_stocker
You already know this but gonna put it out there for others that believe "ram air" doesn't actually exist.
Force of AIR at 100mph (sea level) is about 0.17 psi with no pressure differential. Doesn't sound like much but its enough to knock out a window or a poorly designed structure. Car intake has negative pressure so the effective pressure differential increases thus forcing (ramming) more air into the chambers.
Front breather Camaros need a sealed intake to front bumper to take effect. It becomes a matter of maximizing frontal area of the inlet, building a sort of bulge to allow air to "stack" into the chamber to pressurize then transition down to whatever tube, throttle, or carb. Interesting misconception is being able to "funnel pressure" which flat out does not happen.
Weird things happen with stagnation and stall. There is still quite a bit of very complex physics to consider. Even Pro Mod guys differ opinion on hood scoop design, some use closed scoop that feed 100% of intake air and some have an opening in the rear to let airflow pass through to minimize stall effect.
Is that confusing enough? LOL
Yea.....I've read up on it some and i have built lots of airboxes and restrictor cones for the race cars back in the day.
I made the opening large with the idea of it maybe having a optimal smaller size hole in the bumper...or if it likes big then so be it. I have little doubt it will probably work better than anything else available tho.
Madman builds the BIG GULP front breather boxes to feed the entire "catfish mouth" up to a sort of lid. IIRC they have proven gains of 3mph in the 1/4. I expect similar gains from yours.
Thanks for the link. His looked like it was feeding the oe airbox set up. Mine will do away with that. 11secSS had a nice clean lokking set up in that thread
HioSSilver, loving your setups for sure, you seem to do professional quality work. I just finished a HOW TO book on fiberglass and CF and Ive been studying up on advanced aerodynamics. As soon as I'm comfortable with fiberglass construction I'm going to start some drastic functional aerodynamic mods to the car, the idea is to have a street legal Le Mans GT car without going massive on front canards and rear spoilers. Changing the intake setup for most efficient power making, removing or improving air restrictions on all parts of the car, chin spoiler, flat floor with dual tunnels, true dual exhaust exiting into said tunnels for added velocity of incoming air, front air dam, diffuser, bulged fenders with rear exit slits for wheel well pressure alleviation, hood heat extractor, careful consideration of rear design for least amount of drag while maintaining high speed stability...alot of work, but I'm gonna have fun with it. I would love to see constant updates of your work, could give me some creative ideas as well as getting to enjoy seeing your work come to life.
Thanks man.....i worked on a alms team for nearly 20yrs( the prototype technologies group yokohama M 3's) if i haven't mentioned that in this thread. I made lits of fiberglass and carbon aero devices. It's fun and ALOT of work. You can pretty much create whatever you can dream up with the stuff.
It won't be long and I'll have a cai made the mold is done. Now just have to get time to make it.
11-14-2016, 07:33 AM
