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Enough of the CFD and armchair calculations, this summer I'm going to do some real-world testing. I could use some help planning what things to tests, and how to test them. I also need a second driver, provided you regularly track a Miata (why else would you be here), and know Watkins Glen like the back of your hand.
I belong to the Pineview Run country club which has a tight and technical 1.1 mile track, with about 50 mph average speed. I can go there pretty much whenever, and so I'll do a lot of initial low-speed testing there this Spring. I'm also 25 miles from Watkins Glen, which is an ideal high-speed venue to test aero. I booked a two-day open track (no run groups) event at WGI in early June. I may also do coast-down tests, as I live in a fairly rural area and nobody will care.
What do you want to know? Do you want to be involved, and in what capacity?
Last edited by Occam’s Racer; 01-24-2019 at 09:18 AM.
This is very open ended. Are you an expert driver giving your services of consistent driving? Do you have an aero package that you think will be competitive for Miatas? Do you have a data acquisition system and the necessary sensors to complete the testing? Are you looking for people to send you their aero package to test on your car? I would spark some discussion with more info on who you are, what you have, what you're trying to achieve, and take a stab at how you're going to achieve it.
Might be useful to mention what you are looking to test.
I’m mostly interested in testing different tops, but I’m also interested in what other people want to test. In another thread someone was wondering about diffuser with side skirts vs dirty floor and flat floor.
I’m being purposely vague about testing, I’d like to know what other people are interested in.
Last edited by Occam’s Racer; 01-18-2019 at 09:28 PM.
This is very open ended. Are you an expert driver giving your services of consistent driving? Do you have an aero package that you think will be competitive for Miatas? Do you have a data acquisition system and the necessary sensors to complete the testing? Are you looking for people to send you their aero package to test on your car? I would spark some discussion with more info on who you are, what you have, what you're trying to achieve, and take a stab at how you're going to achieve it.
I’m a good driver, not expert, and I’m looking for someone who is an expert at WGI. I have an AIM Solo and if that’s not enough perhaps someone will loan me something or participate.
I have a couple Miatas and one of them has competitive aero, but the plan is to make modular pieces so many things can be changed and tested. Fabricating or sourcing parts will not be a problem.
Let me start over. In 1993 the Mazda RX7 had a Cd of .29; the Miata of the same year had a Cd of .38. What would a lap time or top speed look like if a Miata was shaped like an RX7?
So I got to thinking and looking at online Cd calculators and such, and it's a lot of fun, but in the real world, what does it mean to reduce drag by 20%? I do endurance racing, and a 20% decrease in Cd is around an 8% increase in fuel economy. That can be the difference between running an extra stint, and very worthwhile. But what does that drag reduction do for lap times? Or what if you take that drag reduction and put it into downforce, then what?
So let's take a Miata of average weight and power (2300 lbs and 120 hp lets say) and start putting different aero bits on it, see what happens. Fastback. Airdam. Spoiler. Side skirts. Flat bottom. Diffuser. Etc. What do each of these things do individually? What do they do together? What makes sense? If you're running a class like ST6, do yo want to run BTM aero and have another 6 hp, or use an airdam and fastback? Is a wing worth the full point? Or let's say in an endurance series where doing a 2-hour stint (or 2:40 in lemons) may be a big deal, what kind of things will reduce drag?
Some configurations that intrigue me:
1) Cheap stuff you can buy on Amazon and eBay - Does a hardtop spoiler do anything? What about those cheap plastic side skirts? Is a small spoiler worth it? Cheap wings, good or bad? We've all seen those cars pimped out with mostly Chinese parts, and you have to wonder if there's any function to it.
2) Spec Miata plus - What if you add a Supermiata style airdam and spoiler to an otherwise Spec Miata? OK, now add a splitter. And then a wing. Now remove the top. What happened?
3) Tops - I build boats for fun, and hardtops are way easier. I've built a fastback, shooting brake and 70s Supercar style top. How do they compare to a stock hard top? Or a Treasure Coast Chop top? Honestly, I could just test the tops and be done with this, but I have potentially 14 hours of track time to test things at the Glen, so why not do more?
4) Underbody - What happens when you add side skirts, a flat bottom, and a diffuser, one at a time, or in different combinations?
5) Open windows - What is the effect of running with open windows, and what can you do to improve airflow?
The list goes on. Not all configurations are worth testing, nor will I have the time or the inclination to test them all, but I have time to do more than just different shaped roofs, and I'm interested to know what are the most compelling things people would like to see tested. I have a couple good Miatas, and I wouldn't be against using someone else's but I need to fabricate brackets and such so that the different tops and front ends can all go on and off easily. So it's easier to do that in my garage on my cars. I have a 93 street car that is more or less a STS build, and a 94 that was a Spec Miata but has been modified well beyond that, with a fastback, wing, airdam, splitter, etc. Both have Megasquirts and could run different maps to simulate different HP, but I'd rather just stick to one each.
Telemetry-wise I have an AIM Solo, but if that's not enough, maybe someone will loan something better. The same goes for parts. I either have or can make most things, but if there's a part someone wants tested, and I can easily put it on, then why not? I'm in this for the info. I want to know. I'm sure there are things you want to know.
I'm looking for like-minded individuals who will spend the time and effort. I'm asking on MT because there's a high level of no-bullshit-allowed here. If you're questioning my ability to drive consistently, well that's why I'm looking for a second driver. I don't even need to drive at all, I'm the parts building and swapping guy. I want this to be a real investigation into Miata aero, and something that will serve as a reference well into the future.
I don't have anything to test? I have two Miatas with six top options (open, hardtop, Treasure Coast chop top, fastback, shooting brake, RF-style), a cheap wing (hoping to get more wings, I'll make a spoiler), side skirts (with and without wheel spats, will make proper barge boards), four front end options (stock, r-package lip, Supermiata style airdam, and a 4" splitter extension for it), and a diffuser. I'd like to make a flat floor. I also have time, money, fabrication skills, 10 track days paid for at a short track, and two days paid for at Watkins Glen (14 hours open track, not a typical HPDE day).
I feel like I can get most of the important data from the AIM Solo, but I'm open to adding more sensors for data acquisition.
At some point I'll meet one of you who's interested in this test, and we can talk about what and how to test these things in a controlled manner.
Last edited by Occam’s Racer; 01-19-2019 at 12:28 PM.
There is going to be way too much noise in your lap times to be able to see much more than a massive change. I think you would get much more useful data using linear travel sensors on the suspension and testing on a smooth flat road to see how much your aero is pushing down on each end of the car. That combined with coast down runs to figure out drag. Pick the highest DF , lowest drag setup that fits your rule set and profit.
Well, Hopefully a little encouragement goes a long way. This is a really cool idea and I applaud the concept and your thoughts/efforts to try.
Personally I would try black and white changes. Coast down and lap times of big differnce items.
WIndows open or shut is a basic one im interested in, we all think we know but (to the best of my knowledge) no one has qualified this.
How much drag does a 3- 4" splitter create in coast down?
I'm not sure roof on or off is pertinent, almost all accept a roof is better than not and race with a roof anyway..?
Maybe roof versus fastback?
Also, 949 style air dam is known to work very well so im not sure there is any point in learning by how much or why....? although with and without splitter would be interesting.
If you believe the CFD work done by the Hancha group, an airdam reduces drag from .36 to .31, and a 3-4" splitter reduces drag further to .29. I don't really trust CFD tests, and that's why I'm doing this. It will be interesting to see if the splitter adds or reduces drag, and that should be apparent in coast-down tests.
There really isn't much reason to test an open top, but I'm interested to see if the HP Wizard drag calculator is accurate for that value.
For sure I'm testing an open top, hard top, Treasure Coast chop top, fastback, shooting brake, and what I call a 70s Supercar top, but is maybe more like a longer RF top. There's 18" of snow between me and the barn, but the tops are in there awaiting final fiberglassing and window cutouts. I'll post some concept drawings and construction photos.
The Treasure Coast chop top is a cheap way to run a lightweight hard top. Some people run a hard top without a rear window, and this top may simulate that situation well enough. This photo is from Treasure Coast Miata. I ran this top at Thompson, but without data, I couldn't tell if it was better or worse than a standard hard top.
This is the fastback I built and raced with last year. Again, no comparative data from the same day. It felt faster. It looks faster! Is it? Who knows?
This is the next top I conceived of over winter break, I like Shooting Brakes.
This is an early photo, it's pretty much complete now, but I couldn't figure out how I wanted to hinge the rear hatch. I got so tired of scratching my head, I started on another top instead.
I call this a 70s Supercar top, because it reminds me of a 512, M1, Pantera, or other 70s car. Also kind of a ND RF, but longer.
It was pretty easy to make using a single sheet of plywood with cuts so that I could bend it. The Shooting Brake is strip built out of individual strips, but slicing up a piece of plywood like this on a table saw is easier. The tops are surprisingly light, being more or less a surfboard style construction, with fiberglass skins over a lightweight core. The gaps are filled with a mixture of epoxy and microballoons. The neat thing about this top is I'll be able to add rear glass and change the height at the rear, so I can effectively test a fastback with different backlight angles.
The next two tops I build will be for 24 hours of Lemons, one is a RX500 (flat top, almost wagon looking), and the other will have a central fin, like a Le Mans Prototype (calling it the LeMons Prototype, of course).
Last edited by Occam’s Racer; 01-20-2019 at 11:22 PM.
Reason: Adding images
Great idea, thanks for attempting this.
For track testing without $$ in sensors/Senna, I'd be interested in only top speed at predetermined point before braking zone. Racechrono with 10Hz booster can easily document this accurately.
-longest straight/ consistent entry speed/pre-determined full acceleration point / end point pre determined and still @full accel.
-hardtop rear window delete. (windows down)
-hardtop vs fastback
I like where you are going. I'd like to see only windows down (what tracks allow windows up?!?). Give us the gold of the testing steps because I myself have considered a million different ways to remove as many variables as possible; but know in my heart I will never be consistent enough to judge laptimes this way. Love the hard top designs.
There is going to be way too much noise in your lap times to be able to see much more than a massive change. I think you would get much more useful data using linear travel sensors on the suspension and testing on a smooth flat road to see how much your aero is pushing down on each end of the car. That combined with coast down runs to figure out drag. Pick the highest DF , lowest drag setup that fits your rule set and profit.
I've looked up linear travel sensors, and there are quite a few available. Has anyone here put one on their car? I suppose I need one each front and back, and some kind of gauge with a max level readout. Is there a plug-and-play solution for this?
Re: noise in my lap times, yes. That's why I'm looking for a Miata driver who knows WGI like the back of their hand. I could put my brother Ian or teammate Evan in the car and they'll be more consistent than me, but I'm looking for someone who is well acquainted with tuning downforce and can instantly feel setup changes and provide feedback. This is not a paying gig, but it is 3 days of free track time.
Great idea, thanks for attempting this.
For track testing without $$ in sensors/Senna, I'd be interested in only top speed at predetermined point before braking zone. Racechrono with 10Hz booster can easily document this accurately.
-longest straight/ consistent entry speed/pre-determined full acceleration point / end point pre determined and still @full accel.
-hardtop, windows up.
-hardtop rear window delete. (windows down)
-hardtop vs fastback
I'll have a RumbleStrip predictive lap timer in the car, and this will help keep a consistent speed at the exit of Turn 1, which determines the speed on the back straight (in a Miata, anyway), and can easily be over 110 mph (even in a Miata). The Aim Solo can get top speed on the bake straight, as well as G-forces in corners, lap times, etc. By overlaying data of multiple runs, large changes should be obvious, small changes probably not so much. I don't think I can test hardtop windows up at the race track, I'll probably be black flagged if I do that. But I'll coast-down test that one for sure. Hardtop window delete and hardtop vs fastback will be tested, as well as the other tops.
01-18-2019, 10:09 AM
Real-world testing
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