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There are other ways to increase front downforce you may want to look into other than just extending the splitter. I've been reading a lot of stuff on Professional Awesome Tech Forums, posts from Johnny C at 9LR, and Occam's Racer. I know all three have their detractors, but the wind tunnel report Occams Racer just published was a very interesting read. Admittedly, a static floor wind tunnel isn't the best way to get data for changes under the car, but the trends shown should be true. Remember that a splitter makes most of it's downforce from negative pressure suction along the entire underside, not just the positive pressure in front of the bumper.
Some things I've learned as I consider adding a splitter to my own car.
Angle and height adjustment. Angle adjustment can increase downforce - imagine a diffuser except at the front of your car. Height, well, so you don't hit things. Also, if a splitter is in hard contact with the ground, it's not getting air under it, and you've lost downforce right as your asking the most of your front tires under braking.
Splitter ramps - mini diffusers into the wheelwell can make for a dramatic increase in downforce for almost no drag penalty. Sadly I've not seen a cheap and easy 3D print file for these yet and off the shelf solutions seem to be pretty expensive.
Round off the bottom front corner of the splitter. The difference is so dramatic that 9LR says they will from now on ship all splitters with a radiused leading edge.
There are other ways to increase front downforce you may want to look into other than just extending the splitter. I've been reading a lot of stuff on Professional Awesome Tech Forums, posts from Johnny C at 9LR, and Occam's Racer.
Funny you'd mention this, I was just reading up on Johnny's FB posts about the raised splitter edge last week haha. Thanks for jogging my memory, splitter tunnels are definitely on my list. No joke about them being expensive, though. Racebred Components is local to me and I have a buddy who's sponsored by them. I actually helped them out a few months ago by letting them take a trace of my GV lip for what I assume was a splitter template for an NC Miata. I hit them up after asking if I could get some help on a set of their diffuser tunnels and was told they had a blemished set they could sell me for $220 instead of the $250 msrp. Needless to say, I didn't immediately pull the trigger but it's ok, I get that they have to make their buck too.
RGR Engineering actually makes a set that's pretty reasonable, but I don't know how these compare performance-wise to the Racebred ones, which look longer and deeper. - https://www.rgr.engineering/product/...splitter-ramps
Otherwise, yeah, you're definitely paying a pretty penny for a pair of those suckers. Doing a quick "universal splitter tunnel" search on Google is pretty demoralizing lol.
I might actually grab a set of those RGR tunnels just since they're reasonably priced. I have to double check with our race series TT director regarding aero rules for my class first, though. The TT5 aero rules state you're allowed "one flat front splitter with no more than 4 inches protrusion from the bottom of the front bumper lip or air dam". I don't know if "flat" means flat in front of the bumper or the entire thing has to be flat. Hopefully I get the go-ahead to throw a set on, though, as it seems the tunnels provide a really substantial benefit for zero downside aside from cost.
Flat 100% means an entirely flat, non-tunneled splitter.
Allowing splitter diffusers is something normally reserved for the higher classes as the complexity and performance can scope and cost creep rapidly.
My next splitter will have tunnels/diffusers, whatever they're called, and I'm starting to think about a rear diffuser. The group I primarily run with for TT has no aero rules, so I might as well take advantage.
The tunnels are stupid expensive for what they are...
I have contacts at a local plastics shop that could probably whip up vacuum formed tunnels for a sell price a hell of a lot cheaper than any of those options..... [[adds it to my ever increasing list of things to consider]]
Flat 100% means an entirely flat, non-tunneled splitter.
Allowing splitter diffusers is something normally reserved for the higher classes as the complexity and performance can scope and cost creep rapidly.
Thanks for the heads up regarding classing with the tunnels. I figured it was too good to be true.
Bookmarking that Thingiverse link for use at a later date.
Mini weekend update. Mitch, one of my 2.5L NC buddies, had a BBQ at his place on Saturday afternoon. In attendance were myself, Frankie, @DUDELOL, and a handful of other SoCal Miata nuts. I forgot Mitch and Greg Peters are good buddies, and actually got to meet Greg that night too. Super cool dude, brought his own homemade hot (HOT!) sauce and guacamole. Greg didn't bring his personal monster Miata (probably for the better as eight or nine dudes would've been asking for ride alongs), but we managed to stack the front of the house with a bunch of humble Miata builds nonetheless.
In keeping with the topic of aero bits that aren't legal in my race class, I've been working on the barge boards/skirts more this week. These won't be used on NASA race weekends, but I assume they're going to provide a bit of benefit and honestly, I love the way they look. One gripe I have with the body of this car is how the doors/rocker panels slope so aggressively inward towards the bottom. Maybe it's just because I read a post from Ryan Passey regarding this topic some time ago.
Either way, I have that Alumalite sheet at my disposal, so I made use of it. Finished up one of the skirts yesterday and mounted it onto the car. I trimmed it flush with the outer wheel lips. Total width ended up at 6.5" compared to the previous 3.5" premade skirts I had for the car. Aside from the chosen width just looking clean, I also wanted to do this so I could make rear wheel spats that covered the entirety of the rear tires.
Don't mind the edge of the factory skirt bowing out. It lost a fastener and started to warp a while back...
I'm pretty stoked on how the side aero project is coming out. The skirts look like they belong with the bigger splitter and airdam. I won't be able to rock them next weekend but I'll definitely have to do some back to back testing with them once track season's on again in the Fall.
Looks hella functional and definitely racekar. Next time you see ole Preg Geters, let him know we miss him around here. He used to post here a lot before he became miata dad.
The car really is coming together dude, it looks sick! The skirts definitely tie the aero together well. Also super cool you got to meet Greg, he seems like a genuinely nice dude.
Gracias dudes! Pad, I may or may not have taken a bunch of inspiration from the barge board thread you started on here 7 years ago, so thanks for that.
Roda, can't wait to see what you do for aero improvements. Mainly because it'll probably be ten times cleaner than anything I've put together haha. Grassroots aero design is fun. It can be a little time consuming but it's so cheap and easy to make changes that tangibly affect the car's handling. At some point this winter, I gotta do a test and tune day and do back to back sessions with all my mini aero accoutrements equipped vs removed (ducktail, skirts, spats, fender vents plugged, etc). Hopefully there's more than just a slight difference in times with vs without everything attached to the car but I'm pretty confident there will be haha.
Nate, racekar is all I'm going for. Even if it just looks faster, I'm into it. Can't have the same-looking car as everybody else haha. I'll tell Greg to get back on here if ever I do see him again. Looks like everybody involved has probably seen, but his 2-piece driveshaft fix for the ZF transmission vibration would've been great info to have documented on here haha.
Since I'm already typing out a reply, allow me to share with you the most ghetto thing you might see today. Our NASA TT director gave me the ok to run my fenders this weekend as long as I plug the vents and resecure the cut portion to the factory position. This is good because the alternative was driving 40 minutes to my buddy Frankie's, taking the fenders off his car and installing them on mine for the weekend. I was going to make some metal brackets to bolt the fenders back together, but I'm only going to run the fenders like this for four more races this year, and don't want to drill more holes in the fenders than necessary.
So yeah, we're running 'em zip tied next weekend.
On a less haggard note, I popped the spare 2.5 apart today. Looks pretty dang good inside and I haven't found any red flags yet.
Zero varnish on the top end. Cam lobes look about the same as the ones that came in my current motor.
Nothing super offensive in the oil pan. The oil in this thing definitely wasn't new but there's no varnish. A little residue on the bottom, probably bits of something falling out of solution while the engine sat for multiple months. I think my current motor exhibited the same thing when I first popped it open.
Hard to get a pic but no debris in the oil pickup tube screen.
Pulled the balance shafts off. No obviously nuked rod bearings.
Cut open the oil filter and didn't find anything other than oil. The stash of red solo cups I keep at work for this task probably seems supicious, though.
I ran the oil filter oil through a coffee filter and found a small amount of debris at the bottom. Not enough to be seriously concerned about. Everyone's aware of how hard it is to get a photo of oil/oil filter debris, right? I tried my best, man...
Anyways, I think she's a winner! Almost all of my reading has led me to believe that these 2.5L Duratecs have a short expiration date when run on track. Statistically speaking, my 2.5 should be long dead by now. She's got 14 track days and a lot of other hard miles on her at this point but still runs like the day I dropped 'er in and hasn't developed a single issue. I'd like to think that the Fluidampr and oil pan baffles are prolonging the life of the engine, but I have no concrete evidence to support that theory. I'm just going to keep running the car into the ground and worry about the engine when it becomes a problem. It feels good to know I have a backup at the ready. If the worst happens, I'll pull the current engine out of the car, swap over the cams, valve springs, and Fluidampr to the backup motor, and hopefully have the car back up and running in a couple weekends tops.
And since they're a dime a dozen, maybe I'll grab another one later this summer and start tearing it down to stuff some hotter internals into...
Last edited by Z_WAAAAAZ; Jun 13, 2025 at 12:27 AM.
Lucky for us, they're just cheap motors haha. I don't know how many of these Ford made between 2011 and now (they're still used today in the current 4 cylinder hybrids, albeit with Atkinson cycle cams), but there's hundreds and hundreds easily available on the used market. My local LKQ has eight in stock currently haha. This one was just an eBay find from a part-out company in the Midwest. It's out of a 2017 Escape that was totaled due to a rear end impact. The motors are pretty easy to find for under $500 shipped. If you grab one local from an LKQ, they're currently $366 before tax.
I dunno if I'm qualified for any sort of consult work, but I appreciate the indirect compliment. I'm just copying a lot of stuff I've seen on the forum. Stay tuned for sure though, there's no telling what sort of silly idea I might try to copy next haha.
I'm not superstitious or anything, but now that you have a spare on hand it more likely you are gonna have a failure. Recent events have shown me that first hand
Not saying you have to, but if you find a way to clean up some of the oxidation on the aluminum block, let me know... I'll be fighting that battle shortly with the aluminum LSx block/heads that I have.
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but it's ok, I get that they have to make their buck too.
