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The LE5pard - Nix's Ecotec Miata Build

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Sorry, should have asked that question better (was actually thinking about the battery comment). How much weight do you need to gain? Are you tens or hundreds of pound off your goal? 

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9 minutes ago, Just_Hayes said:

Sorry, should have asked that question better (was actually thinking about the battery comment). How much weight do you need to gain? Are you tens or hundreds of pound off your goal? 

Hundreds of pounds. I'm going to weigh it this week now that all the big pieces are built, but I'm estimating I'll need every bit of the allowed 250 lbs of ballast to make competition weight for ST5.

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20 minutes ago, turbogrill said:

What about chump/wrl?

 

It's in the cards for this car. I need to get it shaken down and build a few things for reliability. I know other people running the same swap in endurance have a big issues with motor mount bushings wearing out. I'm building my own with bigger, beefier Hasport bushings. I also want to do the AR5 transmission swap, since it would be more reliable for long run racing.

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A few more pictures!

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I'm planning a shakedown and dyno session next weekend, so I'm working down the list to getting it track worthy.

Once any major issues are addressed, it's on to getting it ST5 legal.

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I pulled the car out for a wash. I saw a chance to get the whole Miata family in a picture...

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For those wondering the rest of the Miata ranch is my black daily ND, the white $200 auction find NB, and a K-swap NA.

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I stuck the leopard car on the scales to see how my weight gain affected the car:

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2190 with driver and a half tank of fuel. Hitting ST5 will just be a matter of adding ballast!

I'm pushing to get the car track-worthy by this weekend and take it out for a shakedown at Chin's single day MSRH event.

 

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Belly pan assembled. The steel frame member makes up part of the belly pan itself, and a rear aluminum plate extends to the front axle line. I used 0.90" aluminum for all of this.

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The flywheel was exposed, so I whipped up a cover for it on the band saw. I used black RTV to attach it.

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I have the "paper on windshield with huge list of things to do" (on the workbench in the below picture to so I could clean the windshield) and have been working away at it. Last night I got the last of the critical items done, so it's ready for a test drive on track!!

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I have another round of mechanical and electrical items to tackle after the shakedown, but figured I would want to find gremlins to add to the list before refining too much. After this weekend we'll see about: oil plumbing with lines to the accusump, oil cooler, and remote filter; aux lighting wiring including headlights and motors; a steel plate ballast system; exhaust clearance work... and so on.

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It's 0.090" - I'm not building Terry Fair splitters here!

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I figured as much..  but you said you needed ballast too, soooooooo..

I saw one of Louie's GT cars using 1/4" alu plate for the flat bottom undertray in the center of the chassis.  can't get the weight any lower than that, and it'll stiffen the car up quite a bit!  I'd just hate to be the one taking off the 50 flat head screws that hold it in place every time you need to work on something!

 

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I took a short test drive and everything seemed to hold together! I did notice the fuel pressure is set static in the ECU at 58 psi, so I upped the regulator to match.

 

I also installed the handheld extinguisher on a quick release bracket, and installed the life support system for this weekend. I couldn't find a DC connector so I just spliced it in with Wago nuts for now.

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Speaking of Wago lever nuts, here's a look inside the center console:

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I put Wago lever nuts on DIN carriers and snapped them in to short pieces of DIN rail. This is all for auxiliary wiring - things like gauges and accessories. This makes it easy to modify and troubleshoot without fussing with screw terminals or splices.

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I dragged the car out to MSRH for Chin and a member day

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There is definitely less front downforce than before, so I overcooked braking zones a few times feeling it out. The air scoop design makes a perfect grass clippings collector.

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On the dyno!

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The shakedown shook loose a few issues. The exhaust flange bolts kept working loose:

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I also found the remote oil pressure sensor leaking, a few clunks and pops from the suspension during hard cornering, and a tuning issue known in the LE5 swap community, where there's some sort of mismatch between throttle position and throttle body, putting the car in limp mode (restarting the motor seems to fix it.) I'll get it up on jack stands this week and do further investigation.

But lots of positives! The car felt great! I hit 1:49.8 in the nasty heat on Maxxis tires. The engine has a great power curve, particularly coming out of corners. It also stayed cool (when the radiator wasn't completely covered in grass clippings) despite driving hard in the hot weather.

I'm super excited to have this thing back in action.

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I love this build.

Totally noob aero question here. What does having the whole front grill smooth(ish) like that accomplish without some sort of splitter? I get with a splitter that high pressure zone will help push the splitter down, but I don't get what it's doing in this instance.

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The "flat" front air dam forces air over the car instead of 'through it and also smooths the airstream a bit.  this reduces drag and reduces lift/increases downforce.

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Operation: Weight Gain is a go!

I know there is a beautiful commercially available ballast setup for Miatas, which bolts steel plates to the OEM passenger seat mounts. However, I still want to put a passenger seat there.  So I guess I'll build my own! Off to Metal Supermarkets to get some 1/4" plates cut and punched. Punching is well worth it so I don't have to drill 52 holes through 1/4" plate!

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Using 10.2 lbs/sqft for 1/4" steel plate, each one should be about 20 pounds. 12 full plates plus a 13th partial puts me at the NASA TT/ST ballast limit of 250 lbs. 

So here's where I am. With the various NASA ST/TT modification factors, at 162 average whp, the car needs to weigh 2465 lbs for ST5. Depending on tire and wheel combo, and how well the driver has been eating, we're currently right around 2165. 250 lbs of ballast takes us to 2415. I still need to find another 50 lbs to make race weight!

I'll be adding the passenger seat back in (with a strong mounting bracket!,) headlights with popup motors, oil coolers, and a few other things... which should get me close. The nuclear option is to put OEM steel doors back on, but I really don't want to go there if possible!

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regarding cage components, are you allowed "extra support members" in the cage?  I would think so with ST classes.  methinks a 1.5" cage member made from tube w/ 3/4" wall thickness might be necessary somewhere low and central to the car.   But you might want to ensure that covers up something else allowed which you need access, thus you should make it removable if you need to access that widget beneath the allowed extra cage member.

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42 minutes ago, Matt93SE said:

regarding cage components, are you allowed "extra support members" in the cage?  I would think so with ST classes.  methinks a 1.5" cage member made from tube w/ 3/4" wall thickness might be necessary somewhere low and central to the car.   But you might want to ensure that covers up something else allowed which you need access, thus you should make it removable if you need to access that widget beneath the allowed extra cage member.

I could add to the cage, but I'd prefer not to. Ideally I want to keep everything removable so I can run ST4 if ST5 sucks.

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If you read between the lines, that's pretty much were I'm going.  make a removable cage member out of REALLY thick tubing that weighs 50lbs..  "mr tech official sir, that's not 50lb worth of ballast, that's an extra-heavy duty cage member....   and I have to be able to remove it to get to the whateverwhatevermodule just underneath it."

As least with SCCA, they only measure the wall thickness of key structural cage tubes- door bars, main hoop, A pillar. (there's probably some i'm missing).  but ancilliary cage bars aren't checked.  maybe do a very low 3rd door bar on the right side?   or use several  6" x 1/4" "reinforcing washers" to mount your passenger seat and harnesseses..

 

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The problem with "really thick tubing" is getting a good weld on it. I'm pretty sure I'll be able to make weight without resorting to drastic measures. 

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A bit more progress over the weekend!

I drained coolant and oil and took all the hoses off to install the filter bypass adapter and plumb in the accusump, remote filters, and cooler. The filter I ran for two days collapsed - a web search for "ecotec collapsed filter" showed me it's not uncommon for crappy Ecotec oil filters...

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The bypass adapter replaces this filter completely, so I'll be running a remote oil filter setup from now on. But jeez, that's not good!

At the shakedown, I was frustrated by the bolted flange from the header. The gasket came apart twice, and the hardware kept backing out. I got out the band saw and TIG welder, and replaced it with a V-Band.

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My ballast plates came in at Metal Supermarkets, so I stuck them on the scale to verify I'm compliant with NASA's 250 lb ballast maximum. I knew I'd be around 260 lbs and would need to cut the top plate to get it exact.

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I welded some thick rectangular steel tube to the floor pan, with captive nuts so I can bolt the plates from the top. The holes were pre-punched at 1/2" using a jig, but their setup was a tiny bit inconsistent between each plate. I had to go back and drill out all the holes with a tiny bit bigger bit. Once I did, the hardware passed through and ballast was done.

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With removable ballast limited to 250 lbs, I had to find a few other places to add weight to the car. I built new, stronger mounts for driver and passenger seats, and installed the passenger seat and harness. A brave passenger could definitely ride with the ballast plates installed; with the seat angle it's actually more comfortable and easy to get in and out with the extra 5" on top of the floor pan!

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It's a pretty hefty stack of steel...

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Since I was bitten with the fabrication bug, I decided to build a catch can out of aluminum chunks I had laying around. With the way everything is situated there are not many places to mount an off-the-shelf tank with a full liter of capacity, so I built my own! I started with a 4x4x0.125 square tube that the metal place "sponsored" me, and some old 0.125 plate I had on the scrap shelf. 

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 My aluminum welding skills have definitely improved, but a trained eye can see a few oops-I-dipped-the-tungsten dark spots. Still, I'm super happy with the end result. I have new tubing on order to replace the old blue scrap, but heck, it looks like something I bought! 

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I'll attach a barb/clear hose on the valve at the bottom to drain the tank, and maybe eventually install an external level gauge, but it will work!

There's still a lot to do with oil hose plumbing, suspension setup, and detail work, but the car is essentially NASA ST5 legal and ready to race!

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holy carp that's a lot of steel!!

and 2 mounting bolts on each?  those are 1/2" gr8..  I know engineering maths says those are more than strong enough, but I'm concerned about those guys snapping spart in a wreck.  I'd hate to see a bunch of huge lawnmower blades flying around inside the cabin!!

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Yep, my car is full of shoddy steam bombs and giant lawn mower blades attached with duct tape. 🙄 I'll stick with engineering math over your gut feelings on this one.

Four 1/2" grade 8 bolts through the stack, with the exception of the 8 pound half plate on top which just has two bolts.  I basically copied East Street's design, used in a bazillion Spec Miatas, but mounted the plates forward of the seat to welded tubes instead of to the spot welded seat mount.

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My post wasn't meant to insult your intelligence or insinuate it was going to fail- just an attempt to make sure all factors are considered and ensure you don't die in a wreck. 
Because of the half plate on top, it looked like two stacks of long strips held by 2 bolts each, not large plates with 4 bolts each-- keep in mind I'm looking at this on my phone so images are thumbnails and everything is robust than is appears.

I did some quick maths on 1/2" gr8 bolt and min shear strength..  with 4 bolts there, it would take >150G impact to break all four bolts.  that's napkin math and not accounting for safety factors, holes being drilled off center and shifting more load to a single bolt, etc..  lots of factors go into it, but 4x 1/2" bolts should be more than sufficient. just doesn't LOOK that way when you have several inches of stacked plates ready to shear off the bolt on the first speedbump and then magically turn into lawnmower blades of death. ;)

Also look at what most people use to hold their racing seats and harnesses in..   it's usually only 4 bolts on the seat, and it's almost always less than 1/2"dia. 
Average driver + seat weight is close to 250lbs (in my case exceeds that by some amount)...  point is, seats don't often go flying loose inside a car and are subjected to a lot more strange forces than what this stack of plates will exert on those bolts...   Again, real engineering and 'offshore engineering' don't often relate.

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