Car aero development
06-19-2009, 08:25 PM
#63
It would have to be cut for our exhaust or else reroute your exhaust to be center exit like the Elise. I was hoping to see what Pass did with it. I figured on covering the Elise center exit and cutting my own exit out the right side section of the diffuser.
I've seen Elise diffusers go anywhere from $60 to $200 depending on condition, knowledge and desire to sell. I bought my Elise diffuser and a mid body section for $200 combined. The mid body part goes from the rear axle forward another 3' and has several NACA ducts to route air up toward the engine compartment in an Elise. Figured it might help cool the rear diff and smooth things out more in our cars. I'm hoping by combining those two parts with a mushroom shaped splitter I'd see significant underbody smoothing.
Still have to figure what to do about the front tires.
I've seen Elise diffusers go anywhere from $60 to $200 depending on condition, knowledge and desire to sell. I bought my Elise diffuser and a mid body section for $200 combined. The mid body part goes from the rear axle forward another 3' and has several NACA ducts to route air up toward the engine compartment in an Elise. Figured it might help cool the rear diff and smooth things out more in our cars. I'm hoping by combining those two parts with a mushroom shaped splitter I'd see significant underbody smoothing.
Still have to figure what to do about the front tires.
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06-20-2009, 01:37 PM
#65
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My current exhaust is one of a race car - it ends just before the diff. No normal exhaust with a full muffler under the trunk would fit. Now that the diffuser is mounted when I get around to it I am going to extend my 3" exhaust piping from where it ends at the diff now to the rear, but pipe only - still no muffler as it's a tight fit, but it will either exit with a slight turn down out of the hole that is in the elise diffuser for the center exit exhaust (I currently have an aluminum sheet riveted over that - you can hardly tell unless you look really close) or I will have it exit straight out the back just above the diffuser... haven't decided.
For those of you that don't frequent clubroadster:
For those of you that don't frequent clubroadster:
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06-22-2009, 02:02 PM
#69
How quick can it come off for servicing the rear diff? I'm glad you installed yours first. Now I know that Elise diffuser looks great on our cars. I was hesitant as I wasn't sure if it'd look queer or tough. Definetely looks tough.
Well done and THANK YOU for the pics!
Well done and THANK YOU for the pics!
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06-23-2009, 02:10 PM
#72
Pass,
If you haven't and care to you might contribute your diffuser work over at M.net to this thread...
wings and splitters? - MX-5 Miata Forum
Huge ongoing thread about wings, splitters and other aero stuff.
I worked on mine last night. I'm starting with the 2 hour install method instead of the hard core all weekend job you did!
Mine will be more like the one on the V8 car. Attached the front of it to the sub frame bracing with some spacers to keep it from deforming. Pulled the rear lights, finish panel and bumper skin. Notched the corners of the plastic bumper support high enough that the diffuser just contacts the steel crash supports. Test fit the bumper skin. Used a razor knife to cut the bumper skin just where the two outside sections intrude into it. Cut a slot in the end of the diffuser for the exhaust exit. It's not angled as much as Pass's, won't be nearly as cool or hardcore. Certainly a whole lot less work though. Doesn't require as much cutting and since I have few tools, fewer skills and my car is a daily driver I think this will work for me. Compared to the lotus, Pass' is a little more upright, mine's a little less.
Car's dirty as hell. Sunday's track day in central Oregon at ORP requires a 1 mile drive on a gravel road!
Everything is test fitted and the skin is back on but I have to do proper connections in the rear to support it. The center section of the bumper skin was left uncut so it uses the stock connections. The center of the diffuser fits pretty much flush against the skin. I thought it might look OK left natural but with my black car it stands out WAY to much. Have to paint it black. Took a couple progress pics. Will take a couple more tonight when I finish it up along with the mid body tray.
The way I'm doing this I should be able to remove it in just a couple minutes. If it's not angled up enough I can always go back and cut more out.
If you haven't and care to you might contribute your diffuser work over at M.net to this thread...
wings and splitters? - MX-5 Miata Forum
Huge ongoing thread about wings, splitters and other aero stuff.
I worked on mine last night. I'm starting with the 2 hour install method instead of the hard core all weekend job you did!
Mine will be more like the one on the V8 car. Attached the front of it to the sub frame bracing with some spacers to keep it from deforming. Pulled the rear lights, finish panel and bumper skin. Notched the corners of the plastic bumper support high enough that the diffuser just contacts the steel crash supports. Test fit the bumper skin. Used a razor knife to cut the bumper skin just where the two outside sections intrude into it. Cut a slot in the end of the diffuser for the exhaust exit. It's not angled as much as Pass's, won't be nearly as cool or hardcore. Certainly a whole lot less work though. Doesn't require as much cutting and since I have few tools, fewer skills and my car is a daily driver I think this will work for me. Compared to the lotus, Pass' is a little more upright, mine's a little less.
Car's dirty as hell. Sunday's track day in central Oregon at ORP requires a 1 mile drive on a gravel road!
Everything is test fitted and the skin is back on but I have to do proper connections in the rear to support it. The center section of the bumper skin was left uncut so it uses the stock connections. The center of the diffuser fits pretty much flush against the skin. I thought it might look OK left natural but with my black car it stands out WAY to much. Have to paint it black. Took a couple progress pics. Will take a couple more tonight when I finish it up along with the mid body tray.
The way I'm doing this I should be able to remove it in just a couple minutes. If it's not angled up enough I can always go back and cut more out.
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06-28-2009, 03:21 PM
#74
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no offense and it does look great, but it seems as if it would be even more functional if you lower the diffusers to where its more even with the ground and gets cleaner air. and btw cueball, diffusers arent supposed to have much angle but rather leveled with the ground so it could be argued that for a miata yours may work better. Diffusers are adjustable anyways so the pass will probably lower them at the track if he pleases. the elise and exiges are just lower to where the fins will catch air before anything else so thats why they have a slight angle
Last edited by Sam Amporful; 06-28-2009 at 03:40 PM.
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06-28-2009, 10:57 PM
#75
wings and splitters? - MX-5 Miata Forum
This thread has a huge amount of information and discussion regarding diffusers. The effectiveness isn't really determined completely by angle. The idea is having a smooth transition from flat moving upward so the air stays stuck to it as long as possible. This helps prevent the swirling and sucking of the air flow behind the vehicle. Smoother air is also faster air, less drag that way also. There really isn't a set angle that is effective.
Of course I'm just regurgitating info from that thread. Much of it contributed by Emilio and the other SoCal track rats.
Yes, I believe the angle of mine is likely to be effective. It transitions smoothly up to the bumper skin. I don't know that Pass' would be any less effective though. As we don't have wind tunnels available it's all a guess. I can say that with just the diffuser in place at cruising speeds it seems I'm seeing slightly more vacuum. That means the motor is working less which tells me the diffuser is doing it's job of reducing drag. Car is also more stable changing lanes with worn pavement on the freeway.
I'll look at some new logs vs. old logs and figure out exactly the difference in MAP pressure/vacuum.
This thread has a huge amount of information and discussion regarding diffusers. The effectiveness isn't really determined completely by angle. The idea is having a smooth transition from flat moving upward so the air stays stuck to it as long as possible. This helps prevent the swirling and sucking of the air flow behind the vehicle. Smoother air is also faster air, less drag that way also. There really isn't a set angle that is effective.
Of course I'm just regurgitating info from that thread. Much of it contributed by Emilio and the other SoCal track rats.
Yes, I believe the angle of mine is likely to be effective. It transitions smoothly up to the bumper skin. I don't know that Pass' would be any less effective though. As we don't have wind tunnels available it's all a guess. I can say that with just the diffuser in place at cruising speeds it seems I'm seeing slightly more vacuum. That means the motor is working less which tells me the diffuser is doing it's job of reducing drag. Car is also more stable changing lanes with worn pavement on the freeway.
I'll look at some new logs vs. old logs and figure out exactly the difference in MAP pressure/vacuum.
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