tadeuzagallo skrev:

cirs skrev: The small complication, and I know how this is gonna sound, was that my brakes were done...

Brake is speed's worst enemy....

Welcome to the forum! I'm sure you'll enjoy your stay and I'm looking forward to reading about your build.

tadeuzagallo skrev:

cirs skrev: Welcome to Sweden. I would spend next season driving as many tracks as possible to see what you are building your car for, especially if you are looking at a specific series to test those tracks out. It might not be the big power you need on technical tracks compared to aero or seat time. There is a good rejsa calender here to find trackdays, and the mx5racingclub are great to drive with and have good trackdays. And what is needed to register you car as there can be some nice loop holes you can use as you are importing the car. Thanks! That was my original plan, and it might still happen. In either case I plan to drive all the tracks where I'd be competing, but worst case scenario I'll drive the other car. The small complication, and I know how this is gonna sound, was that my brakes were done. They were overheating and overheated my wheel bearings as well. There were other possible solutions, but considering I didn't like the pads I was using, my calipers needed rebuilding and I would have to upgrade the brakes soon anyway, I just went for it and got the biggest brakes that could possibly fit with the 15" wheels. These are 300x32mm discs and the kit uses 20mm brake pads. As expected though, none of my wheels fit anymore, and going to larger wheels would mean moving up to 245 tires, which is way too much tire for 135whp. That is gonna be slower than the 225s I was running, but it's just the first season to learn the tracks, so whatever. The other question is whether I'll resist getting started once the parts start overflowing in the garage... but my hope is that there's enough to do that I can get started without completely taking the car out of commission for next season.

A lot of us drive with Wilwood calipers, VW g60 discs with brake cooling (or the mx5 big brakes but the pads are a lot more expensive), and this works nicely. And nearly all 15" wheels fit. You can repack the bearings with high-temperature grease when they are new to extend their life. I used the Redline CV-2 but any quality high-temperature grease should work nicely.

cirs skrev:

A lot of us drive with Wilwood calipers, VW g60 discs with brake cooling (or the mx5 big brakes but the pads are a lot more expensive), and this works nicely. And nearly all 15" wheels fit. You can repack the bearings with high-temperature grease when they are new to extend their life. I used the Redline CV-2 but any quality high-temperature grease should work nicely.

The calipers I'll be using are also Wilwood, the 4-piston Superlite, but unfortunately it takes a 10" wheel to clear it. I could get the right 9" to fit with spacers, but my 9" wheels have terrible clearance, and even with 25mm worth of spacers it still wouldn't fit. I'll consider repacking the bearings, I always hear people recommending it, but I've always dreaded it.

My 8.5" wheels have slightly better clearance, but even spacing it out 15mm it was still too close for comfort. I'll probably put my 2 sets up for sale and get a set of 10" wheels.

As promised, here's a small background on the car:

I moved to California at the end of 2019, rushed to get my driver license, bought a (different) car and went to the track a couple of times, all within a few months. I quickly realized that I wanted a cheaper, dedicated track car, a shitbox or a beater if you will. Miatas were by far the most popular beginner track car, so I started looking on Facebook Marketplace and within a few days I found this mostly stock 1990 1.6 Miata, for just over $3k. I met some random guy at a random parking lot and drove it home:



It was supposed to be a cheap, simple "seat time car". The plan was to change tires and brake pads and add basic safety items and get on track. I scrambled to get it ready for its first track day in March 2020, but the event got canceled the day before, it was the start of the Covid lockdown in California.



With some spare time in my hands, and going crazy during lockdown, I started fiddling with the car. Before I even made it to the track for the first time I ended up replacing the radiador, shocks, bushings and sway bars. I lowered the floorpan for better helmet clearance, installed race seats, a rollbar and harnesses. I removed most of the interior, deleted the AC and power steering and started to get bothered by the amount of unused wires... until I found myself in this situation:



Eventually I managed to get the wiring back together (although it was still pretty bad), and installed an AiM race dash:




This was my first time working on a car, I had only a license for a few months at this point and had never been very mechanically inclined, so this was a great platform to learn, and I had a lot of fun (in between the moments of frustration). Eventually we made it to the track!



For the following year, I sent the car to get a cage from TC Design, one of the best cage shops in northern California. As much as I take pride in doing everything myself, a cage didn't feel like a great first welding project. Since the car was already mostly apart, I decided to paint the interior:







While the car was apart I had the opportunity to buy a 1.8 engine out of a 2005 Miata, which made about 135whp with a tune. Not a lot, but a big improvement over the 30 year old 1.6, which probably had about 90bhp on a good day. With the engine came a new transmission, new clutch, exhaust, intake and ECU.



In an ever-growing case of "while I'm there I might as well", I figured that since I had to modify the harness for the new engine it was a good time to do away with my hacked wiring harness. I bought an AiM PDM, MSEL Master Switch and lightweight battery. I took an online course with HP Academy and built myself a new wiring harness:




Eventually, the car made it back on track. It had a couple hiccups, mainly a coolant cap I forgot to clamp and resulted in me losing most of the water from the cooling system in my out lap, and then a misconfigured PDM output which resulted in the injectors shutting down at high rpm, but after a couple sessions the car was running great.



After that I ran a few good events, eventually had a coil go bad and took a little too long to diagnose it, but it was mostly smooth sailing. Kept doing some random projects to keep myself busy, but nothing major: replaced my wheel hubs as people were losing wheels left and right due to hub failures, deleted the brake booster and modified the pedal for better pedal feel, gutted my doors even further for more weight savings, deleted the front cross member for easier engine removal and added some better ducting, etc...






It was around July 2021 when things got out of hand again: after deleting the brake booster the pedal effort was manageable, but a little too high. The extra force and change in leverage also changed the pedal position, which made it difficult to heel-toe. So, I put the booster back, right? Well, no. I bough a new pedal box:



Now, the pedal box is a lot closer to the driver than the OEM pedals, and since my fabrication skills aren't that great, this seemed like a great opportunity to move weight further back, so I moved my seat all the way against the rear bulkhead. I'm not very tall, so that was quite a few inches.

Of course, the only problem now was that I couldn't reach the steering wheel, or the dash, which happens to be where all my switches were... so I added a 150mm steering wheel extension and prototyped a center console to relocate my switches.



It was around this time that I had to ship the car here. The car wasn't running and had no brakes, so that was a very questionable decision.



Arriving here, the car was then kept in storage for quite a few months, as we had just arrived and I had nowhere to place it.

This post is already way too long, so I'll continue later with the rest of work I did until my first trackday in Sweden. Meanwhile the parts for the next upgrades are on the way 😬

Have read with pleasure about your impressive build in such a short time. Not too long post at all.
Will continue to follow you and your mx-5 on this forum

Welcome and regards
Kari

WfQC skrev:

Have read with pleasure about your impressive build in such a short time. Not too long post at all. Will continue to follow you and your mx-5 on this forum Welcome and regards Kari

Thanks for the kind words and thanks to everyone else as well for being so welcoming. Ever since I landed in Sweden every single person I met through the car/track/racing community has been incredibly nice and helpful!

---

A small update on the current developments: After several days obsessing over which diff I should use, I finally made a decision!

The most common choice for high hp Miatas is a Ford 8.8, but the axles readily available are either 28 splines or 31 splines, which requires a fairly old diff which I couldn't easily find in Sweden. I was convinced that using a BMW diff would be a better option, considering how popular they are around here. I had a 215K diff laying around, but for some reason there's surprisingly little information about it online, and a 210mm diff seemed like the common answer. I found a couple of those on FB Marketplace, but they were either expensive or in terrible shape. One of them was an M3 e46 diff for 15k, so that was one option, but it seemed too expensive so I decided to consider other options.

In the end, I decided to go with a less popular option, but which seems to be getting more popular: a "Super 8.8" diff. These are the updated 8.8 diffs that come in S550 Mustangs and there's heaps of them to choose from on Bildelsbasen: you can choose cast or aluminum casing, gearing, LSD or open, etc. I went with an aluminum diff (these are from the automatic cars), 3.55 gearing and OEM LSD. With axles it cost me just a bit more than half the price of the BMW diff, all from a car that had less than 10000 km. There's also a huge amount of options for gears and LSD units in the aftermarket, and they seem to be generally cheaper than the equivalent units for the BMW 210mm. The diff internals, in theory, should be stronger than the BMW unit, which is not really relevant in my case since the aluminum case is the weak point, but it should plenty adequate for a 4-cylinder. One nice thing about it is the weight: 34kg (vs 39kg for the 215k diff I have, I'll compare with the Miata's diff once I pull it).

The downside is that the Super 8.8 uses 34-spline axles, so there are no readily available axles (or mounts for that matter). I'll need to fabricate some mounts on the subframe and figure out what to do about the axles. I was considering just welding the Mustang and Miata axles together and sleeving it, but it seems like the diameter difference between the two might be too big. I'll look deeper into it when I pull the axles out of the Miata, but I might try to find some local shops to quote custom axles, so if anyone has recommendations that would be appreciated

Nice car and some impressing work but you seem to be avoiding the biggest question of them all:
Why leave sunny California for the notsosunny Sweden?

oneyet skrev:

Nice car and some impressing work but you seem to be avoiding the biggest question of them all: Why leave sunny California for the notsosunny Sweden?

I get that question a lot, it's almost like people don't like the weather here lol.

I'm not gonna lie, 2 years of track days without a single drop of rain was nice haha, except for a few days that were over 40°... I think the worst was 45°, the AiM logger registered 57° inside the cockpit... not fun in a 5 layer suit. I used to run a CoolShirt, I imagine they are not quite as popular here, it's an ice box that runs cold water through your shirt under the suit, but that didn't even last through the outlap lol.

I'm not originally from the US though, I'm from Brazil, and after living in a few different places me and my family decided the US wasn't for us. So we decided to move to Sweden instead, sight unseen lol. Happy to report, no regrets so far though! We actually even enjoy the winter, but maybe not all 6 months of it if I'm being completely honest lol.

The new transmission arrived yesterday! Exciting times! I ordered the transmission and adapter kit from DomiWorks, and I'm super impressed. This stuff is way too nice for my Miata lol. I went with the 8hp70, which is rated to 700nm of torque, but supposedly can handle a lot more. Considering that the 4Piston K24 that dyno'd at 1000hp made just about 750nm peak torque, I should be more than safe. But boy, this thing is heavy! Weighed at 88.5kg, and I haven't weighed the Miata one yet, but the internets tell me it's about 36kg... at least the extra weight is low and right at the center of the car, so it could be worse. I guess it would be hard to make 5x as much power and not gain any weight, specially on a budget.



I also took a minute to put the car back on the scales and recorded some weights as the official baseline. Total weight was 889kg with an empty tank, but all other fluids were complete. 55.7% of the weight in the front, 50.05% on the left side. That was honestly better than I expected for the weight distribution, I thought the rear would be even lighter after I removed virtually everything that had any weight from there. Cross weights were completely out of whack, but that is a problem for another day. Nevermind the sketchy pieces of metal to level the scales, that was all I could find in the moment... I should really get some leveling pads.

Hehe, do you remember what I said at Gelleråsen when we discussed the rules? "This is a PRO car with too little power" I told you the best thing was to just get 500hp and drive. Nice to see you do it!

I will follow your build and hope to see it at the tracks later.

Cammo skrev:

Hehe, do you remember what I said at Gelleråsen when we discussed the rules? "This is a PRO car with too little power" I told you the best thing was to just get 500hp and drive. Nice to see you do it! I will follow your build and hope to see it at the tracks later.

Haha of course I remember! I took it to heart. Might be a minute until it's actually on track with it all said and done, but I look forward to it. And I look forward to seeing your car as well!

For the past couple of days I have been working on designing a new hardtop for the car. Originally, the main motivation was to stay dry: the current top doesn't have a rear window, and I already have to use a rearview camera as there's no visibility, so I figured I could design a closed top. "While I'm there" I figured it was a good time to switch to a fastback top. The shape of the OEM top is not very efficient from an aerodynamic standpoint, as the angle of the rear is too steep, and that causes the air to detach almost immediately. Fastback tops have been a popular way to mitigate that for track Miatas.

However, fastback hardtops can be quite expensive, and their shape also isn't optional (there's an excellent post comparing the available options: https://occamsracers.com/2023/01/15/miata-fastbacks-and-aftermarket-tops/), so I thought this was a good opportunity to design my own hardtop. I used most of the ideas from the blog just mentioned, and this is what I came up with:



The visible squares are because the it has already been split into printable sizes, as I'll be 3D printing it in a 256x256 printer. The goal is to then skin it with carbon fiber, get rid of the printed parts and add some internal reinforcements.

The shape of the top is derived from a template (also mentioned in the blog), used by a website for folks to improve fuel efficiency, which means reducing drag, so it's also very useful here:



Another important thing is that the OEM top of the miata is wider in the B-pillar than the windshield, that increases the frontal area and consequently increases drag. This hardtop fixes that by narrowing down earlier. The reason most tops aren't built this way is that the windows would no longer seal, but that isn't a problem since I don't have windows to begin with. Once I do build myself windows, I will just match the shape of the top.



Another thing I've been trying to learn is to do some basic CFD simulations. The biggest problem with CFD is knowing whether you can trust the results you get, so considering I have virtually zero experience I don't fully trust my results, but I did validate my baseline and ran the results by a few people. I wouldn't make any bold claims based on these results, but they seem reasonable.




In the first picture we can see where the air detaches from the OEM top as soon as it gets near the rear window because the angle is too steep. With the fastback, we can see the air stays attached all the way through the spoiler. We get a larger wake, but due to smaller frontal area and better side taper we still get a 14% drag reduction, while reducing lift by >70%.



I also ran a couple tests with a wing, as I wanted to make sure the spoiler wouldn't interfere with the wing. I used a MSHD airfoil with a 10" chord length, roughly where my current wing sits.

With the OEM top the detached flow at the back disturbs the air going into the wing, which reduces its effectiveness. With the fastback and the wing at the exact same location, the wing becomes 12% more efficient due to the better flow attachment.

Considering my simulation skills, I don't trust the final numbers, but I do think the relative values are reasonable. With that disclaimer, I calculated the final downforce at 160km/h as 390N (87lbs) for the Fastback+Wing vs 47N (10lbs) for the OEM+Wing.

I've been meaning to update the thread for a few days, but it's been an incredibly busy week. A lot of time went into planing, as I wanted to take advantage of some of the Black Friday deals. I managed to order:
- most of the fuel system (surge tank, filter, fuel rail, injectors, fuel pressure regulator, fuel pump)
- some of the turbo bits (turbo, wastegate, flanges, blow-off valve).
- tires (245/40/15 Nankang CR-S)
- and some random bits (air jacks, catch can, 3D scanner, gas lens kit)



I spent a fair amount of time in the garage, also doing some quality of life improvements:
- I got a heater installed, as it seems I'll be spending a long time in the garage
- I put the car on some rolling jack stands I got from Verktygsboden. I have a single car garage, so this was a major improvement
- Got an engine stand and put the K24 on it so I can start assembling things. Writing it seems silly, but between assembling the hoist, and shifting everything around the garage to make space, this took me a lot longer than I wished.



I also managed to do some actual work on the Miata:
- I printed a bunch of parts of the top and started assembling, I'm about half-way through
- I removed and disassembled everything on the rear subframe in order to prepare it for the 8.8 diff. The plan is to scan both the old diff, the subframe, and the new diff, then make some mounts.
- The engine is almost ready to come out: removed all the fluids, disconnected all the wiring, just need to bleed the clutch and remove the radiator and I can take it out.



Oh, I also did some more 3D modeling and played a bit more with CFD. Finishing the body work and starting to figure out what to do for aero.



I also took advantage of the Black Friday deal and signed up for the full season with TimeAttackNU. My goal is to compete with the Miata, which seems plausible at this stage considering I have most of the parts and 6 months to go, but I made sure to check that I could drive the other car if I couldn't make it in time. I'm hoping that by signing up for the whole season and getting to know some more people it might help me find a sponsor for next year.

Next thing up I gotta get this diff mounted. I need to find a shop to build me some axles ASAP. If anyone has recommendations for a shop that could help me, that would be awesome. I have both the original axles from the Mustang and the Miata, but I need to mount the differential in order to get the final lengths.

Impressive work and tempo 😊😊👍

erikjakan skrev:

Impressive work and tempo 😊😊👍

Thanks 😊 I'm usually quite slow to work on the car, but having a clear goal is always very helpful. Otherwise, it's hard to have the motivation go to out to the garage when it's so cold outside. I still think it will be stretch for me to make it in time for next season, but I'll give it my best shot. At the very least I hope to get the car on track next year, even if I can't make it to the competition.

ok, ill continue the discussion here instead if IG, much more interesting . Here are some random photos i picked up when i did some quick work a while ago to make some printed splitter tunnels, some after market some are from factory race cars.

one pic is from Jacky Dings video, acutally a quite good detailed walk through with verus engineering, you might already have seen it. Lots of CFD details around the splitter, and some quite dramatic improvements with the work theyve done.

Just some inspiration since you are going nuts with the aero

Oh, I see what you meant now, splitter diffusers, not the actual diffuser.

The front end is still just a draft, but I'm trying a slightly different idea. I still haven't ran any simulations, but the whole splitter is airfoil shaped, which then feeds the wing, similar to a dual element wing.



The splitter profile needs a lot of work, and the second element is just a profile I was using as a single element rear wing, so it might not be the best profile, but that's the general idea.

Interesting info on the differentials. I am quite heavily invested in the Sierra diff platform but always nice to get more info on options.

Regarding drive shafts; I have had Dione Kullager i Uppsala make me custom shafts, good to deal with and not very expensive. But I am sure there are more people doing it now for the drifting scene too.

therealpinto skrev:

Interesting info on the differentials. I am quite heavily invested in the Sierra diff platform but always nice to get more info on options. Regarding drive shafts; I have had Dione Kullager i Uppsala make me custom shafts, good to deal with and not very expensive. But I am sure there are more people doing it now for the drifting scene too.

Oh interesting! Is the Sierra the same as an Explorer? 8.8, independent rear suspension, 31 spline? It so, that'd have made my life a lot easier 😅 but I wasn't aware of it...

I'm talking to a friend in the US who has a machine shop and makes Miata parts. He made himself axles using the 930 108mm CV, and I'm trying to talk him into developing axles for Super 8.8 as well. Right now I'm 3D scanning the subframe and both differentials, I'm going to tack the diff into place so I can get measurements, and I'll get quotes for the axles. I knew it was going to be expensive to get custom axles that can handle 1000hp, but damn, it's much worse than I expected.

Do you know if Dione Kullager also makes driveshafts? Either way I'll have a chat with them, maybe I can get some better pricing.