I'm in the middle of building an air dam. Here is how it currently sits:

https://www.miataturbo.net/attachmen...7&d=1373951567

I'll be fastening a vertical plastic sheet to the front just like you've all seen before with an opening for my radiator but I've got a question about the opening. Should I be ducting the air only to the radiator opening? This makes sense to me so I can make the opening as small as possible and reduce drag but what if I don't? Will that create a high pressure zone above the "splitter" and create more down force before pushing out towards the wheels? Making the ducting doesn't seem like the easiest task but I could probably just bend some aluminum sheet for the bottom and 2 sides and be fairly effective.

I've always liked the way the C5R Corvettes ducted air from the upper rear quarter panels. I don't have the guts to cut into my car like that (yet) but it's interesting:
https://www.miataturbo.net/attachmen...ine=1373981018
https://www.miataturbo.net/attachmen...ine=1373981018
https://www.miataturbo.net/attachmen...ine=1373981018

I look forward to reading about how those vents perform.

My experience, from playing around with a manometer, is that opening the windows drastically reduces interior air pressure. That said, this was over a year ago and I don't recall which location I used as a reference point for that test.

Thought some guys are cutting the stock bumper at the crease towards the top if you wrap the ABS in the "EP style"? Then duct from the opening in the wrap all the way to the radiator. Makes it so you can have a more squared off ducting that is easier to fabricate.

Found this today. Ferrari uses fans to "pulse" air from the diffuser to the tail lights in the 599XX

https://www.miataturbo.net/attachmen...ine=1374295725

https://www.miataturbo.net/attachmen...ine=1374295725

https://www.miataturbo.net/attachmen...ine=1374295725

One of these days I'm going to take my manometer, a ball of yarn, a roll of tape and a gopro with a suction cup out for an afternoon drive. I wonder how many speed limit passes I will be able to make before I get pulled over?

Venting lower quarter panels to rear and tail lights? With turbonators? What is the goal of that.

I found that Ferrari piece a few months ago and thought about a fan or a R/C electric turbine to help suck the air out of my drivetrain tunnel. But I am looking at running my exhaust the same way as the Ferrari. The goal I have is to reduce the rear drag by pulling as much air out of my drivetrain tunnel as possible.

Open

https://www.miataturbo.net/attachmen...ine=1374451918

Closed

https://www.miataturbo.net/attachmen...ine=1374451918

One thing you aero is going to change with that car in front of you, but good pics with the GoPro

what do you know, we were right about air being sucked in.

:(. No maybe about it. No I need to get a manometer and find out weather that's good or bad. It doesn't look like it effects flow either way from watching the other areas.

That's an area where higher pressure would aid in drag reduction and down force. Personally, I'd just leave the vents shut or replace the window.

So along the lines of the negative air pressure in the cab... I have slots cut in my trunk lid for an old rear wing mount setup I was playing with. I had been having problems with exhaust gases getting sucked into the cab while out on the track and had tried several things to deal with it.

At the last event, I tried sealing the trunk slots (and all other holes that led into the trunk area) with painter's tape, hypothesizing that was the path for the exhaust getting into the car. That fixed the problem immediately. So, I am not surprised at all about the tufts getting sucked into the rear window vents as shown above.

My exhaust exits past the rear bumper fascia.

Yep.

One thing I noticed though, if you look at the row of strings on the trunk lid: with the vents closed some are pointing up/forward but with the vents open they are all laying down flat and pointing backward like they should. You can only see a couple of them in the pic so its hard to be sure, but they may indicate that the laminar flow is getting back down to the trunk lid faster with them open... not that I have any idea why.

Ohh yea, that's for sure. I had a buddy who raced a civic hatchback and didn't have the weather stripping on the hatch glass. It would suck in enough exhaust fumes to make you feel light headed.

Less turbulent air (some went into the cabin) or just less pressure for the same reason. :dunno:
Are you thinking about ducting the high-pressure turbulent air to some low pressure zone and thereby make the important air under the wing less disturbed?

I'm assuming it's like the base of the windshield or an open truck bed where a high pressure "bubble" (for lack of a better term) is created and the majority of air flows over that high pressure area. Bleed off the pressure and air can follow the shape of the car closer.. but it'll also create a LOT of drag.

Shitty picture I found on google (left side):
https://www.miataturbo.net/attachmen...ine=1374709726

Do any of you guys with quick disconnect splitters have pictures of your mounting setup that you could post? Specifically the rear mounts. I went back through this thread and the "Splitter height" thread and didn't see much. I made a giant splitter last week and was pretty happy with the mounts I made, but I dropped 2 tires on corner exit Sunday and lost the splitter and destroyed my brackets, so it's time to redesign. My mounting setup didn't fail from aero forces, but from the splitter digging into dirt. I'm going to go from 3.5" static up to 4" and try not go off any more lol.

Losing the splitter alone didn't upset me too much since I expected it to happen at some point and used plywood and kept it pretty cheap, but what I didn't expect was that the aluminum angle pieces I had attached to the splitter as backing for my airdam ended up taking out 2 fresh hoosiers. :burncash: They didn't puncture the tire enough to damage it, but it was enough force over a small enough area that it caused a giant split in the rubber, down to the belt. Pretty nasty, since I would have likely kept going in a race situation and found out about the tire issue a few laps later. I want my new setup to be completely flat after the bolts tear through the wood, so that if I lose the splitter again I won't have to worry about a high speed tire failure. I've got a couple ideas on how to do that, but still haven't figured out one that retains the quick disconnect for loading onto the trailer.

John just built a new splitter and air dam for Crusher. The install was convoluted enough he had to write instructions for me :(

fuzzy cel phone pics FTW

https://www.miataturbo.net/attachmen...ine=1375500647

Yikes! That's how I backed my air damn too. I've been off twice I can think of and must have got lucky on the shoveling.

Emilio - what is the height to the bottom of the splitter at the leading edge?

3.5"

In for more crappy cell phone pics. The sub frame of my car has only 3" of clearance with the 1/2" splitter material so 3.5" at the leading edge would give me upward rake. I don't have pinch weld heights handy but Crusher sits lower at a glance.

This is exactly how my car sat last weekend. 3" at the subframe, 3.5" at the tip of the splitter. I didn't get any good timed laps in before hte splitter came off, but the car felt the fastest it's ever felt. I'm not worried about a little upward rake.

4.25 F/4.5" R without driver

Does the splitter go under the front of the sub frame or stop somewhere between there and the heat exchangers?

To subframe. Full coverage, all one piece.

So from the subframe to a 3.5" leading edge, you have a bit of upward rake? The bottom of the front subframe seems to be the lowest point on the whole car. I'm considering less underneath coverage so I can get the front closer to 4" while maintaining level to the ground.

This was my first one and it is the same height as the subframe
https://www.miataturbo.net/attachmen...ine=1375578588

No, mine is like Jeff and everyone elses. I think you are assuming we attach to the lowest point of the subframe. Bad idea. You'll tear it up. We make a tongue sorta like 1993ka24det's and slot it in on top of the lip there in between the rack mounts. I haven't measured it's rake but it's pretty close to level I think.

Less crappy cel phone pic from ACS today

https://www.miataturbo.net/attachmen...ine=1375593467

OK - thanks. I was going from the bottom of the subframe which is costing me almost an inch. I'll have to see what clearance I have to the steering rack mounted FM oil cooler. I'll probably need to finish the season with my low clearance and hope I don't have a nasty off. I'll redesign everything from scratch over the winter. :party:

Well, unfortunately, I didn't get much data with the splitter setup as pictured compared to the COT splitter.

Right out of the gate on Saturday, my time with the new setup was good for two seconds over my best time with the COT splitter. Understeer was gone, handling was neutral with the slightest hint of the back stepping out in places. I never bottomed out with the COT splitter, but was making contact several times here and hitting the bumpstops (also confirmed by a few fender marks on the front tires). I didn't want to stiffen the shocks up without more than one run to base it on, but sadly, during run #2, a bump in turn 17 unloaded the suspension, and a slight offroad excursion and contact with a wall and huge tree branch result in the splitter and mounts getting annihilated.

I really would have liked to see what it was capable of. I finished up the weekend using just the air dam and rear wing, and the first run had so much understeer it was terrifying. I ended up with the front Konis nearly full loose, and the rear shocks at about 3/4 stiff, and finished the weekend slipping and sliding my way to about 4 seconds quicker than my best time. I'm confident that I could have bested that time with the splitter had I been pushing as hard as those last couple banzai runs.

I think I will likely go with something comparable to this setup with the spill plates next year, just need to come up with a better mounting solution for getting on and off the trailer with the new nose.

Bear in mind I am a complete amateur and have no aerodynamics experience, I am in no way trying to shit on your design.

If the purpose of the sills in to keep more air on the splitter and in turn more downforce, do the sills need to be so large?

Gurney lips on rear wings have been used for decades. It keeps more air on the wing for longer, would something on splitter edging not work similarly?

If a 1/2" lip on the side edging of the splitter, where you have your sills now, could keep air on the splitter longer, as opposed to spilling off the sides. And without creating the drag the large sills do between them and the front bumper/fender.

Just a :noob: :2cents:

Bigger is better. Any two things that operate in completely perpendicularly different directions of airflow, such as a gurney flap and a splitter endplate are two things that are so different they probably shouldn't even be mentioned in the same sentence. A smaller lip would help when compared to none at all, but a bigger one will create a larger build up of pressure and therefore downforce than a smaller one. At some cost of drag of course. I have some theories about how that can possibly be minimized while still using a large endplate though.

-Ryan

Gurney lip is used loosely. I was picturing something quite a bit larger, maybe 5-6" tall, but is a fender height side plate really needed?

I think the tall side plate sealed to the bumper/fender at the rear edge would create way too much drag.

But I don't have 400hp pushing me along either.

It's going to produce more drag than without it. "Way too much" depends on a lot of other factors. We know for certain that there are cars for which the benefits of this feature greatly outweigh the drawbacks. Knowing whether it's right for a certain car takes only a bit of real-world testing.
-Ryan

More GTC 250 goodness. Dont judge me on my lack of front aero. Been too busy with research and helping Sonny on his car to finish my car.

https://www.miataturbo.net/attachmen...ine=1375946766

https://www.miataturbo.net/attachmen...ine=1375946766

All I know is that it worked pretty darn well with it. You'd imagine that at some point, some of the drag may be negated by a bubble effect, comparable to the pickup truck bed scenario. I will likely be doing something very similar with the new nose, except that the air forced into the radiator opening will now be ducted straight out the top of the hood, which should provide a marked improvement.

Really ought to spend the bucks on some wind tunnel time next spring up in Mooresville...

Kieth, why are you so resistant to the flat front many of us run now. Your current setup "pac-man mouth" is creating a ton of drag and some slight lift. I bet you could get rid of the splitter completely with a flat front end ala Crusher and keep/gain your front anti-lift the same as the current setup.

"So resistant" is being a little overdramatic. I've never said anything against it. I just haven't done it on my car.

Although plucas's simulations would disagree with your statement. My setup (#4) is considerably more efficient than a flat nose without a splitter (#5). Note both the lift numbers and the drag between those two.

Since I have a little more horsepower than most, drag is not as much of a concern to me as it is to cars like Crusher. And I'm learning more by playing with canards and splitter depth than I would by simply copying other setups. That's important. It's also a setup that I can easily revert to full rally spec if required as well - this is a multi-use car.

Real world testing has confirmed the flat front/small splitter/under tray past axle line to be far more efficient in creating anti-lift. You have a junk yard at your disposal, you should test different front end configurations. I think you will come to the conclusion that many of us already have.

You seem quite offended by the fact that I'm not running the status quo. I apologize for that. I've got some other interesting areas I want to play with at the moment, so the front end is liable to stay the way it is for a while. But thanks for your concern.

It's ugly and Keith is probably using the car as a dual purpose car. Play and sell products. They also cater to a little different crowd then the 949 boys.

Not only this, but if plucas's simulations had the same surface area on both the #4 and #6 splitters the #4 would make more downforce.

Keith, I want to see how your canard experiments go. I need to find some more front downforce somehow, my 6" from the bumper splitter that's the same style as yours doesnt make enough downforce to balance out my massive dual element wing.

I can also see downforce being more important to Keith due to the "low" speed nature of most T&D rallies.

I created the model for Paul's CFD runs based on my car's setup who's main purpose is autocross and some hpde type events. The CFD numbers don't lie, those are results from many runs to verify mesh and quality of the results.

When comparing these setups real world testing is important, but could there be other factors skewing the results? The driver, the setup, the ambient conditions? CFD gives you much greater control over these variables and by that I mean 100% control.

Will the results of our case study change your opinion? Obviously not. However I do feel that the current crusher setup with the flat front and a splitter is pretty ideal at reducing, lift, drag, and creating downforce on these cars.

Note that my comments about the CFD results were comparing jacob's original statement - flat front/no splitter vs stock nose/splitter. Once you put a splitter on the flat front, it starts to perform better. Jacob changed his statements. And some of them were just plain wrong - the CFD shows that my setup does not generate "a ton of drag" and "slight lift".

But I'm okay with that. I get to play with my canards and I have a more flexible setup for different venues. In the rally, I need something that's damage resistant, and my current setup will flex upwards nicely if it grounds out. I hit the same speeds on the Targa Newfoundland as I do at Laguna Seca, BTW. Granted, I could be faster at Laguna Seca, but it's not a night-and-day difference.

Again, I'm not against the flat front. I'm not saying it's a bad thing. If I have, find those statements and prove me wrong. I just haven't gone that way with my car for various reasons of my own. Marketing is NOT one of them, as the Targa Miata is my personal car and I don't make any money from selling parts with it.

Any further front end experimentation will probably be with end plates on the splitter, because I find this interesting. And that's the important thing to me - it's interesting. I don't learn by following a cookbook. But I've got at least two other aspects of aero that I want to play with first, one of which hasn't been tried on a Miata as far as I know and the other hasn't been closely checked out.

Leafy, the canards work quite well - better than I expected. I don't have any numbers on them showing before/after times, but when I installed them between sessions at High Plains Raceway I picked up some good front end grip. It was most noticeable on turn-in, but the car keeps the same balance at speed as it does in low speed corners.

Sorry if I didn't make it clear, but I was reiterating your point that the CFD results back you up.

And I wasn't saying that you in particular should change to a flat front type setup just throwing my opinion out there on what is likely the ideal setup for most track miatas based on my experience and CFD results. (keep in mind I don't run this on my car)

We will also be doing some CFD experimentation soon with various gurneys on the portions of the air dam in front of the wheels. Based on previous experience with other vehicles there is the potential for increased downforce with little to no increase in drag but this will require some experimentation to be optimized.

I would like to bump this very interesting thread with a question-
I will very soon be doing some bodywork, I wanted to slightly "widebody" the car to fit a bit more tire. I also was interested in running a flat front/splitter, so since the flat front can be "custom" aligned to the fender, can I simply pull the whole fender out a small amount like the red one did to vent air, and do a follower underneath that? I like the idea of the follower but don't like the look of the open rear tire. I know aesthetics don't necessarily deserve a place in this thread, but if my idea is also aerodynamically feasible, it would be the route I would like to take. Looking forward to more interesting research from you fine bunch of fellows, good day.

You're right. You have it very backwards for a place like this. Also, go do a meet-and-greet thread, then we'll talk...maybe.

'Speedricer'.... Lol..


Anyways, for those of you who have done the DIY splitters from plywood, what did you attach the rear of the splitter to at the subframe?


Mike

I didnt.

I'm trying to figure out V2 right now, it probably going to get something back there that just stops it from getting jammed backwards when it gets rammed into the pavement. The transition to the hill at T4 at NHMS and some of the transitions from one concrete block to another at lincoln really bent the shit out of the mounts.

Just skimmed your build thread. Are you considering attaching it to the subframe?

In some way, even its its just something that sticks up and prevents the splitter from getting pushed backwards. Any force from downforce is actually pushing the rear of the splitter up on mine, and the current mounting is more than strong enough for that. Its the front of the splitter hitting things that is bending the mounts. There is that convenient tab right in the middle that could potentially be used.

I was noticing that specifically this morning, as well and the 6mm bolt hole for the splash guard, though I've all but decided against them, thinking they won't be near strong enough on an impact.

There are two convenient threaded tabs you can use. They are at the front of the subframe below the steering rack. They aren't the strongest mounting points, but I'd rather have the splitter break off than bend the subframe.

I used those for my first undertray. They held up fine under aero loads but bent back/down and failed in an impact.

My second iteration (for a splitter) used a round bar bolted on with the front bolts of the steering rack bracket, then hooks attached to the splitter for a quick disconnect setup. The heaviest hooks I could find were still pretty light duty and bent when I dropped two tires on corner exit and the splitter caught dirt.

Current setup that I'm testing this weekend is what emilio alluded to a page or two ago with a "tongue" cut into the splitter that then gets wedged into the area between the steering rack mounting points and rests on that pinch weld on the subframe. It goes under the rack and over the pinch welds. It's a tight fit and has very little vertical play with the front hard mounted. (I'm not a fan of cables for the front.) All of the metal subframe/steering components in that region are pretty beefy, so the expectation/hope is that the wood will just splinter and buckle on impact. My only concern with this setup is that it could buckle upward enough to take out the radiator, but I'd probably have bigger problems than the radiator at that point.

Haven't taken any pics yet since I'm reusing my old cracked and splintered but still functional splitter to test this setup. I can snap a pic or two tonight if anyone can't picture what I'm talking about.

I set mine in place that then drilled and tapped two M6 1.0 into the subframe where the splitter made contact. I haven't dealt with an impact but I'm sure the two small bolts and/or plywood would disintegrate before anything structural bent.

I used turnbuckles and eye hooks. Worked well, and when I crashed, the eye hooks gave way. Made it easy to remove, too.

Anyone here dabbled with side skirts? Trying to figure out how I want to approach mine. I have side exit exhaust, so I'm thinking thin aluminum sheet bent into a 90 to come out and down from the rockers to decrease ground clearance, with a possible taper near the front wheels (again, take a look at the Peugeot T16). Optionally, I can frame them out of aluminum tubing or brake line and make a light pair out of fleece/fiberglass, but it would sure suck to go through all that work and then lose it in an off-track excursion. Would also need some sort of insert to protect it from the exhaust exits, which is why I'd prefer the aluminum.