Miata Flat Underbody
#61
Good call on the diff cooling though.
I like the shapes of the ports in the undertray on the porsche...
#62
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With the underbody we want the air under the car to move faster than the air around the car. I don't know how a much of NACA ducts disturb the air under the car (would need help, but i know plucas is busy) If any one has details on how much air is disturbed because of it. Or run a NACA duct right before the diff, then right after redeposit the air right after the diff. Or also will pulling the air from under the car up to the trani tunnel cause more downforce?
#64
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Feeding the air back to the outside world is an important point, too. The duct to return airflow after the diff should allow the air to accelerate as it rejoins the underbody airflow for minimal disturbance and maximal airflow over the diff.
At least this is what the book tells me.
#65
I like all the underbody stuff - er, for fuel economy (though I wouldn't mind better accel at low triple digits just for spirited street driving).... It doesn't show, less likely to get you nightsticked and your car taken away. I'd love to do a spoiler for the same reason, but somehow can't imagine that not labeling me as "ricer".
Really like the early post with the rails welded to the stock frame.
Really like the early post with the rails welded to the stock frame.
#66
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You're worried about the exhaust pipe itself heating things? Yes, the exhaust gasses are pretty warm, but much of the engine bay is in the ~200-300 degree range, where 50 degrees will make a substantial difference. I certainly wouldn't wholly discount the ambient temps.
Good call on the diff cooling though.
I like the shapes of the ports in the undertray on the porsche...
Good call on the diff cooling though.
I like the shapes of the ports in the undertray on the porsche...
A properly designed and constructed NACA duct creates almost zero disturbance to the airflow, that's why they are so bad-***.
-Ryan
Last edited by ThePass; 01-24-2013 at 03:15 AM.
#67
It *seems* to me that getting a few vents would fix up your problems... The issue is all the air feeding the tunnel in a sealed box is passing through the radiator. That's not a lot of area (so not a lot of velocity) and it's heated air.
Putting in a few ducts would probably help a ton. As would coolers.
But for pansies like me who just want good gas mileage with the occasional mountain switchback or stoplight race, I don't think I get that much heat in there.....
Putting in a few ducts would probably help a ton. As would coolers.
But for pansies like me who just want good gas mileage with the occasional mountain switchback or stoplight race, I don't think I get that much heat in there.....
#68
flat bottom pictures
We're planning a flat bottom for the Catfish. The floor is flat until the rear diffuser, which should make some free downforce out back. The Thunderhill car had neither flat bottom or the diffuser--time constraints.
Brian Goodwin's race car is also shown from the back. He's got a full flat bottom on his car and he says he notices the downforce going over the start/finish rise at Laguna Seca. Our extends beyond the rear bumper, and has a gap between the bumper and the diffuser to prevent the rear fenders from catching air.
Canards molds are also being made. I'll be making some that fit stock Miatas as well.
Brian Goodwin's race car is also shown from the back. He's got a full flat bottom on his car and he says he notices the downforce going over the start/finish rise at Laguna Seca. Our extends beyond the rear bumper, and has a gap between the bumper and the diffuser to prevent the rear fenders from catching air.
Canards molds are also being made. I'll be making some that fit stock Miatas as well.
#69
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AbeFM - Between man hours and materials, I think it would take a long time for the additional gas mileage efficiency to pay off the cost of making a whole flat underbody... Not worth it IMO. Trying to get 5 more mph at the end of the front straight at a track? Worth it IMO.
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
#70
We're planning a flat bottom for the Catfish. The floor is flat until the rear diffuser, which should make some free downforce out back. The Thunderhill car had neither flat bottom or the diffuser--time constraints.
Brian Goodwin's race car is also shown from the back. He's got a full flat bottom on his car and he says he notices the downforce going over the start/finish rise at Laguna Seca. Our extends beyond the rear bumper, and has a gap between the bumper and the diffuser to prevent the rear fenders from catching air.
Canards molds are also being made. I'll be making some that fit stock Miatas as well.
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Brian Goodwin's race car is also shown from the back. He's got a full flat bottom on his car and he says he notices the downforce going over the start/finish rise at Laguna Seca. Our extends beyond the rear bumper, and has a gap between the bumper and the diffuser to prevent the rear fenders from catching air.
Canards molds are also being made. I'll be making some that fit stock Miatas as well.
Attachment 65501
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#73
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Well, a very gradual curve could probably maintain attached flow even if it ultimately reached an angle steeper than the generally accepted max of ~15*, but that's not gradual, it's pretty sudden. From what I understand too, that doesn't look like a great design.
#76
I'll tell you just how good/bad our diffuser works, once we get it on the track.
My diffuser s hinged and adjustable up and down, so you can consider the angle a "street configuration", which was the plan from the start. The angle is lowered via threaded rods. I'm as anxious as anyone else to test this aero.
The front splitter in the picture mates exactly with the outline of the body. I've made a larger version for track use, and i'll be trying front canards as well.
Can't wait to get it on the track.
#77
AbeFM - Between man hours and materials, I think it would take a long time for the additional gas mileage efficiency to pay off the cost of making a whole flat underbody... Not worth it IMO. Trying to get 5 more mph at the end of the front straight at a track? Worth it IMO.
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
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-Ryan
#79
Cool. I have to ask, is the Catfish something that Tony helped build/design with you guys? Because about a year ago he had a basically tube-frame chassis sitting around with miata seats/engine/trans/wheels/etc. and he was talking about how it was going to be a super lightweight version of the miata once it ever got finished, and when I saw the Catfish come out, it looked like a pretty similar chassis under the skin.
-Ryan
-Ryan
#80
AbeFM - Between man hours and materials, I think it would take a long time for the additional gas mileage efficiency to pay off the cost of making a whole flat underbody... Not worth it IMO. Trying to get 5 more mph at the end of the front straight at a track? Worth it IMO.
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
cordycord - That looks like Tony's (AWR) shop. Is it?
-Ryan
I'm not sure how much I would do - likely not all the diffuser bits, as they'd show from the outside anyway... And I need to do SOME radiator shrouding again. But a certain amount of very thin metal or metal/plastic could work out to have tangible benefits without quite as much work as it seems?