I just realized I was discussing the new front aero with Cédric, but I never posted the latest renders. I'm currently re-modeling the body of the car in order to get better results with the CFD. I was working off an STL I found on the internet, but it was very low resolution and not watertight.

As I mentioned, it's still a rough draft, and I need to work on the splitter profile, I only spent a few minutes on it.

Awesome work, but that things is hardly gonna move with 450hp , For very low speed tracks, sure, but youre gonna think its superslow at speed
Aim for 700 atleast, or go abit smaller on aero!

My corvette with 509whp only managed 269km/h on Döttinger Höhe with mine in comparsion very moderate aero.

tadeuzagallo skrev:

TexasRx7 skrev: Have you considered running the BMW 7 speed DCT gearbox? But i don't know if that will work better @ 8000R/pm I considered it before I chose the 8HP, I don't think the RPM is a problem with them, but I've seen a lot more people blowing them up due to tuning issues. The 8HP was also a lot cheaper, and should be able to handle as much torque as I'd make even with 1000hp, all with the stock torque converter, so it seemed like a really good fit, I just wasn't aware of the RPM issue. I got a quote from Sellholm, and I'll consider it, but I don't think it's feasible for next season at this point. Looks like the perfect setup, but just the box would cost me almost 5x the 8HP + adapter, which I already have. The other benefit of the 8HP is that I can get rid of the clutch pedal, which would make it a lot easier to fit the air jack. I don't know, considering how popular these swaps are becoming, I might roll the dice and hope for the best.

What's the problem with high RPM? Oil pump drive?

erikjakan skrev:

Awesome work, but that things is hardly gonna move with 450hp , For very low speed tracks, sure, but youre gonna think its superslow at speed Aim for 700 atleast, or go abit smaller on aero! My corvette with 509whp only managed 269km/h on Döttinger Höhe with mine in comparsion very moderate aero.

I still have to run the CFD with the front wing, but with the large splitter + dual element from the previous iteration the drag wasn't TOO bad. The open passages in the front should help with drag, so I think it might be "ok".

For the 2024 season there are 2 rounds at Kinekulle, 2 rounds at Gelleråsen and 1 at Mantorp. I'd imagine that at Mantorp I'd struggle on the straight, but for the other 2 it might be worth it? In any case, I have ZERO hope of being competitive next year for multiple reasons: lack of experience on the tracks here, learning to drive what's effectively a completely new car, lack of power compared to the competition, etc.. so this is all looking further ahead. The following year I plan to get a built engine, which should allow me to max out the power for the class, somewhere between 700 and 800whp depending on the final weight, at which point drag becomes virtually irrelevant.

I'm still going to run it through OptimumLap as Cédric suggested and will report back once I can get to it.

MaZ skrev:

What's the problem with high RPM? Oil pump drive?

I think the oil pump gears. The information I found on the internet suggests that it starts cavitating around 9k rpm, which is quite a bit higher than what ZF recommends.

I'm not sure what is the issue with the output shaft speeds though... my friend said ZF recommends a maximum speed of 6000rpm, which is surprisingly low... it effectively makes it a 5 speed box

For the first year, I think the plan is to send it without any mechanical sympathy and see what happens 🤷‍♂️ if it breaks, then I'll know what is the limit lol (maybe I should buy a spare)

tadeuzagallo skrev:

erikjakan skrev: Awesome work, but that things is hardly gonna move with 450hp , For very low speed tracks, sure, but youre gonna think its superslow at speed Aim for 700 atleast, or go abit smaller on aero! My corvette with 509whp only managed 269km/h on Döttinger Höhe with mine in comparsion very moderate aero. I still have to run the CFD with the front wing, but with the large splitter + dual element from the previous iteration the drag wasn't TOO bad. The open passages in the front should help with drag, so I think it might be "ok". For the 2024 season there are 2 rounds at Kinekulle, 2 rounds at Gelleråsen and 1 at Mantorp. I'd imagine that at Mantorp I'd struggle on the straight, but for the other 2 it might be worth it? In any case, I have ZERO hope of being competitive next year for multiple reasons: lack of experience on the tracks here, learning to drive what's effectively a completely new car, lack of power compared to the competition, etc.. so this is all looking further ahead. The following year I plan to get a built engine, which should allow me to max out the power for the class, somewhere between 700 and 800whp depending on the final weight, at which point drag becomes virtually irrelevant. I'm still going to run it through OptimumLap as Cédric suggested and will report back once I can get to it.

Yeah it will definetly be faster, but not as fun IMO

With so much aero, it will be very sluggish at speed regardless. SMR porsche is a good example of, even though the miata is much lighter!

https://www.youtube.com/watch?v=UyY3ge85fE8

tadeuzagallo skrev:

erikjakan skrev: Awesome work, but that things is hardly gonna move with 450hp , For very low speed tracks, sure, but youre gonna think its superslow at speed Aim for 700 atleast, or go abit smaller on aero! My corvette with 509whp only managed 269km/h on Döttinger Höhe with mine in comparsion very moderate aero. I still have to run the CFD with the front wing, but with the large splitter + dual element from the previous iteration the drag wasn't TOO bad. The open passages in the front should help with drag, so I think it might be "ok". For the 2024 season there are 2 rounds at Kinekulle, 2 rounds at Gelleråsen and 1 at Mantorp. I'd imagine that at Mantorp I'd struggle on the straight, but for the other 2 it might be worth it? In any case, I have ZERO hope of being competitive next year for multiple reasons: lack of experience on the tracks here, learning to drive what's effectively a completely new car, lack of power compared to the competition, etc.. so this is all looking further ahead. The following year I plan to get a built engine, which should allow me to max out the power for the class, somewhere between 700 and 800whp depending on the final weight, at which point drag becomes virtually irrelevant. I'm still going to run it through OptimumLap as Cédric suggested and will report back once I can get to it.

Most of our tracks are tiny (except maybe Gotland ring, and anderstorp, none of them are run in the TA series), so otpimum for our tracks is very different to larger tracks. In general there are fairly few high speed corners aswell. Drag is not a mega important factor, compared to getting that power down, which most likely will be challening enough with 400whp in an mx5.

If you can block of some aero and trim out the wing i think there should be adjustment enough to find a good spot for the tracks you run on, there will be so much other stuff to sort out anyway

Have you read the AeroBytes by Simon McBeath in race car engineering? Lots of interesting data from both CFD and wind tunnel testing.

Like this one
http://www.sm-designs.co.uk/pdfs/RE-V28N8-PikesPeakCorvette-webres.pdf . . . .

here are some other ones he share on his site:
http://www.sm-designs.co.uk/articles.html

If you want more of them i might be able to help

erikjakan skrev:

Yeah it will definetly be faster, but not as fun IMO With so much aero, it will be very sluggish at speed regardless. SMR porsche is a good example of, even though the miata is much lighter! https://www.youtube.com/watch?v=UyY3ge85fE8

You might be right, I think that's generally true of fast aero cars.

I spent the first 4 years focused on building a fun car, completely analog: no power steering, no ABS, no brake booster, no TC... if you see my video driving on the rain, with less than ideal tires, that is probably the most fun I ever had on a race track.

However... now I want to build something fast, and I think half of the fun is building it. After all, I think most of us spend a lot more time working on the car than driving it. I'm curious found out if 1) I can build something fast, 2) I can drive something fast lol

tadeuzagallo skrev:

erikjakan skrev: Yeah it will definetly be faster, but not as fun IMO With so much aero, it will be very sluggish at speed regardless. SMR porsche is a good example of, even though the miata is much lighter! https://www.youtube.com/watch?v=UyY3ge85fE8 You might be right, I think that's generally true of fast aero cars. I spent the first 4 years focused on building a fun car, completely analog: no power steering, no ABS, no brake booster, no TC... if you see my video driving on the rain, with less than ideal tires, that is probably the most fun I ever had on a race track. However... now I want to build something fast, and I think half of the fun is building it. After all, I think most of us spend a lot more time working on the car than driving it. I'm curious found out if 1) I can build something fast, 2) I can drive something fast lol

Yeah i agree, and especially if planning to win in TA you definetly need alot of aero.

I only mentioned it because I noticed on my current car that i think the aero makes a car slighty more boring to drive, or atleast needs alot of power. Before I had more powerful cars with less aero and they were always a handful to drive

Cédric skrev:

Have you read the AeroBytes by Simon McBeath in race car engineering? Lots of interesting data from both CFD and wind tunnel testing. Like this one http://www.sm-designs.co.uk/pdfs/RE-V28N8-PikesPeakCorvette-webres.pdf . . . . here are some other ones he share on his site: http://www.sm-designs.co.uk/articles.html If you want more of them i might be able to help

I have read a few AeroBytes, but not too many to be honest. I'm currently reading his book, Competition Car Aerodynamics, but the progress has been slow... time's been scarce between the day job and building the car.

I appreciate the offer, if you see something particularly relevant I'd definitely be interested. Otherwise, I hope to get back to doing some more research soon.

Oh wow, it's a been a while since I posted an update... I took a break for the past 10 days or so, had a short holiday with the family and was mostly offline.

A lot has happened though, so I'll try to share a brief update on all the areas:

I have two new sponsors: Auto-Gruppen and Nuke Performance! I couldn't be more excited about it! And it was just in time for the TimeAttackNU announcement:



Meanwhile, I've been getting the engine ready to go into the car. In order to fit with the Miata subframe it was necessary to change the oil pump, pickup tube, windage tray, pump chain and oil pan. I finished assembling everything yesterday and the engine is ready to be mated to the transmission for the first test fit. I have been posting small time-lapses of the assembly on instagram, to try and keep some content going without boring people: part 1 and part 2.



For the past couple weeks (and while traveling) I still managed to keep some progress going though. I've been reading a couple of books on aerodynamics, as well as a bunch of articles, papers, etc. I have tested about 50 different versions of the car's front-end, some of them just for learning, and some alternative designs.

A friend helped run some OptimumLap simulations of the existing model I shared with the splitter + the wing vs a dual element front wing vs a triple element front wing, with both 450whp and 750whp. This was an interesting experiment to see if it was worth going with a more extreme hillclimb-style aero vs the original direction I had in mind, and the original design won at every track (Gelleråsen, Mantorp and Kinekulle).



I was struggling to get more downforce out of the original front end, hence the crazy multi-element wings I tested, so I took a step back and started from the ground up, with just a splitter seeing how much I could optimize it. It's been an interesting experiment, and I learned a lot from it. Here are a couple CFD comparisons that I thought were specially interesting:

I ran all the tests with the maximum allowed area for the front splitter: a rectangular splitter that extends 200mm forward of the bumper and 300mm sideways from the wheels. All the tests had the same flat floor, rear diffuser and a dual-element rear wing.

I started with a simple flat splitter with rounded (bottom) leading edge, which was (unsurprisingly) not enough to balance the rear wing, and the front end produced lift. Adding a simple flat 12º diffuser to the splitter changed the front lift coefficient from 0.210 to -0.359, and total lift changed from -1.460 to -1.837. It was a total of 28.5% increase in downforce. In the picture below, the blue areas are producing downforce by sucking the car down, and I thought it was pretty wild how much more efficient the splitter became with such a small change that is so easy to make.



The second big improvement was getting rid of the high pressure areas ahead of the tires. It's common advice that having a diffuser vent into the wheel is bad, but still better than no diffuser, so I tried a few solutions: a few different designs using strakes, to effectively isolate the high pressure zone into a section of the diffuser. Unfortunately, none of them worked. In the end I tried getting rid of the diffuser in front of the tire, basically creating two separate tunnels, one on either side of the wheel. That was again a huge surprise, although it kinda makes sense: by raising the bottom of the splitter right in front of the tire we're exposing the underside to a high pressure zone, probably not a good idea. This increased downforce by 8% on top of the previous result.



Anyhow, not such a brief update after all... 😅 now time to get back to work

Really cool!

Happy new year everyone! My goal was to start the year with the engine in place, and it was a grind until the last hours of the last day, but I made it!



There were a couple hiccups, which meant it took me about 5hrs to do what should have been a 2hr job... a stripped flywheel bolt, a missing starter motor, engine mounts that were harder to assemble than a lego technic without instructions, the subframe needed trimming so the engine had to come out twice... and probably some stuff I'm forgetting, but I persevered!

I'm now working on fabricating some transmission mounts, which looks like it should be relatively simple. Just building a simple tubular structure that bolts on to the tunnel.

In parallel, the aero development continues. I'm now on iteration #60 just since I started redesigning the frontend... I managed to get a lot of downforce even without the front wing, and now I'm struggling to design a rear wing that can overpower it before I can add the wing back. I was probably a little naive to think that designing a super high downforce multi-element rear wing wouldn't be this hard, but I'm making progress and learning a ton nevertheless. I have now found a design (with a couple tips from a friend) that can make quite a bit of downforce, but the amount of drag may not be acceptable, so I'm still iterating to see if I can find a more efficient solution. I also designed a new diffuser which helped a bit with rear downforce, and I'll get back to that as soon as I find an acceptable rear wing design, as there's still a lot to be gained with the underbody downforce... needs adjustments to the diffuser, side skirts and fenders in order to all work together.


A couple renders from the latest CFD run just to add some color:

These past two weeks I've been working on fabricating the transmission, diff and rear air jack mounts. This is something I have very little experience with, so progress hasn't been as quick as I'd like, but that was expected.

The transmission mount I built on my own, it's super simple, and I'll still add some reinforcements later. The first side took me a ridiculous amount of time, but the second side was 10x faster, so at least I'm learning. The welds range from passable to embarrassing, but they have good penetration.



Then last week I got some help from @nordic_restoration with the rear subframe, to try and learn from someone who actually knows what they are doing. We worked on it all day, and while we couldn't quite finish it, we made some pretty good progress. The first photo is how far we got: we got the rear diff mounts in place and the air jack mount tacked. I'm now working on the front diff mounts in the second picture.



Over the last weekend I also got some time to mess with the 3D model a bit. The rough ideas are pretty close to what I want, but I need more rear downforce and I'm still fiddling with things to try and increase efficiency. One of the big things was just the dirty air from the front tires interfering with both the rear wing and the floor. I added fender vents, barge boards, turning vanes and air curtains to try and work together to control the front tire wake. I also added some fences to the side skirts to try and seal the floor a bit better. Finally I added some extensions to the rear diffuser strakes to create a vortex on the outer edge and try to protect the diffuser from the rear tire wake. I ran the simulation with all these changes combined, as I've been running more accurate simulations and these take a couple of days to run. The whole package seems to work, and had a pretty big bump in efficiency, about 20% better L/D.




I ran some lap time simulations in OptimumLap, and I'd like to target a Cd of 0.8 and Cl of -3, without any major increases to the frontal area. The challenge is that I'm already pretty close to that Cd, but need a lot more rear downforce... about 30% more. I still have a little bit of time to play with this while I finish some other things, but I don't want to go too far, so we'll see what I can come up with in the next few weeks. Looking at the front projection and the drag bubble I think there's a lot of room to reduce the drag. The first that sticks out (literally) is the rear wing. That is tricky because of the added height of the fastback, so even at that maximum allowed height for the wing the low pressure under it is already interfering with the fastback. I'll design a new wing and give it a try, current thinking is a triple element with smaller flaps/higher aspect ratio. The other area is the front fender, the rear part sticks out quite a bit, and although I like how it looks, I suspect it might not be very efficient, specially considering that the current struggle is adding rear downforce.

Lots of things happening !

The big holes in the side of the front, are they curtains or where do the air go?

Do you model the flow through the radiator in any way? Is the cooling flow exiting through the wheel wells? Or will there be some bonnet extraction scoop later ?

Lets hope you can continue to progress at this rate, im looking forward to see more

Cédric skrev:

The big holes in the side of the front, are they curtains or where do the air go?

No, the big holes are straight pass-through that exits out of the fender well. That made more sense in the original design, since there was a wing there. I was a bit too attached to this part of the design, but I'm no longer convinced I can make it work with the means I have for both design and manufacturing. I'm currently simulating a new frontend where those holes are closed and the fenders are a bit more streamlined to reduce drag.

The air curtains were right next to it, kinda hard to find a good angle and I didn't want to slice too much out of the model to not lose context, but hopefully this helps:

Cédric skrev:

Do you model the flow through the radiator in any way? Is the cooling flow exiting through the wheel wells? Or will there be some bonnet extraction scoop later ?

I don't simulate it yet. I've been studying how to do it in OpenFOAM, but I haven't yet had time to model it. It's a bit more complicated since at the moment it'd go through multiple bodies in my model. The goal is to have one single big inlet in the middle (as in the current model) and one outlet out of the hood.

The model still needs a lot of work, but it's progressing together with my understanding of the simulations, so I can run longer simulations with more details and higher confidence. I've now set up a faster computer, and the simulation time is down to ~24hrs (from >36hrs).

I think the next big things I'd like to add to the model are
- better wheels/tires: right now it's one big cylinder... pretty bad
- flow through radiator
- wing uprights (right now the wings are wifi in the model lol).

Cédric skrev:

Lets hope you can continue to progress at this rate, im looking forward to see more

Thanks, it's been challenging, specially with the CFD stuff. I have no physics education beyond high school, but I'm trying hard to do it right, not just copying random values and seeing what happens. It can be a lot though... I've lost count of many full days I spent on cfd-online trying to understand all the boundary conditions, numeric schemes, turbulence models, etc. But I've been running some calibration cases as well, and I think I'm making progress.

Currently working on the rear wing, trying to make a more aggressive wing, but with a smaller chord, so I can move it out of freestream a bit and hopefully be able push it harder while reducing frontal area. I'm hoping this will allow me to make a bit more downforce while perhaps increasing Cd a little but maintain or lower CdA. It's still early in the simulations, but I'm testing a few models:

This is the current wing I had in the previous simulations. The total chord is too big, just over 500mm, which is making it difficult with the placement/interaction with other elements of the car:


I'm now trying a few iterations with three elements, using the same airfoil profiles, but much smaller chords: the main plane is 250mm and the flaps are 100mm each. The combined chord is ~400mm.

I started with a more mild setup, with a small angle on the main plane and less angles on the flaps. It worked ok, but I think the gap is too small:



Then I tried a heavily cambered version. In this case the gap was definitely too small, the last flap isn't doing much. I'm current running this setup again, just with a bigger gap between the second and third elements. Looks like it might work.

It's been absolutely hectic, the first test day is on May 6, so there's no time to rest. I wanted to share a quick update nevertheless.

The diff is in the car. Bronson (from bro-fab.com in the US) has finished building the axles, and I should have them soon.



I'm still trying to figure out the driveshaft situation, so in the meantime I started mocking things up in the engine bay. Currently figuring out fittings and hoses that will be necessary, and also all the small bits for the engine (oil cooler, turbo oil, coolant lines, etc). The parts for the exhaust manifold are also coming, so it's gonna get pretty busy in there real soon.



On the electronics side, I'm still removing all the old stuff, so I can figure out how to mount all the new stuff. Got the CanTCU last week, and will making some mounts for these nice paddle shifters.

Just thinking out loud... Could it be a good idea to copy the diffuser "ramps" in front of the front wheels to also be in front of the back wheels?

stilldouble skrev:

Just thinking out loud... Could it be a good idea to copy the diffuser "ramps" in front of the front wheels to also be in front of the back wheels?

Oh hey, sorry I missed this. That might be worth trying, however in the front I had better results with not having the diffuser in front of the wheels. It ended up with a high pressure zone under the diffuser due to air ahead of the tire, and that did more harm than good. But there might be a way of making it work in the rear, perhaps combination of diffusers + strakes/turning vanes? What I've seen more often on GT cars though is some dive planes above the side skirts, which I might try later, but I haven't really tested anything that fancy/finicky.

---

Another quick update: I've been slowly putting together/planning out the engine bay. It's getting pretty tight, specially since I want to keep everything above/within the frame rails to have more freedom with the aero, but it seems like it will work! Most things are laid out:
- Nuke Performance fuel pressure regulator, flex fuel adapter, fuel rail and AN8 PTFE fuel lines
- Speeding/Hurricane expansion tank and AN16 hoses
- T7Design electric water pump adapter
- Supermiata radiator, which will get some AN16 bungs welded to it, plus the filler neck deleted

Still needs to be installed:
- Intercooler, just arrived yesterday, need to be put in place
- Davies Craig EWP150 water pump

After that I can finalize the location for the hoses, catch can, water pump, intercooler piping, etc. This will also allow me to work on the radiator exit duct.




With the diff in place, I finally got all the measurements needed for the driveshaft. Bronson (BroFab) will also be helping me with that. It'll be tough to get the car ready for the first test day (May 6), but it's safe to say that without his help I would never have a chance, can't thank him enough!

I also made some progress on the hardtop. In the last picture I shared it looked mostly complete, but not every piece was properly glued together. I forgot to get a picture (d'oh), but i t now sits mostly stitched up, I just need to go over the entire thing and "finish weld" it. It also has some tension points due to small misalignments, but I'm hoping I can use a heat gun to push it back in place. I was stuck for a bit on what to do next (filler/sand/reinforce/etc), but finally decided to add a layer of fiberglass first, then filler, paint and finally use that as the positive mold for the final carbon piece. The deciding factor was that it's just too flimsy as it is (4mm 3d printed panels, 10% infill, just melted together). I'll have more updates on this soon.

As it's been the theme throughout the build, I tend to split my time between the garage and the computer, my natural habitat. I've been juggling a few different things on the 3d front:
- Continued the design of the triple element wing that I mentioned last time. Worked out beautifully in freestream, ran into some issues when I actually tested with the full car model though. Made some tweaks, and it worked, but the drag penalty was just too high, so I ditched that and went back to my previous dual element design.
- Finally modeled the radiator in CFD. The results were interesting, both drag and downforce went up a bit, which I think makes sense. Drag was expected since the air is actually going through the radiator, not just making a bubble up front, and the downforce gain was small, potentially from the shape of the duct. The downside is that I don't have the proper coefficients for the radiator/intercooler combo, but should be better than a blind hole in the bumper.
- I have also been modeling the steering wheel button box, but it's not quite ready yet

And last but not least, I designed yet another front end... so many iterations, but I'm finally happy with this one. It's not perfect, the CFD numbers could be a bit better (drag went up a little more than I'd like), but the aero balance is better, makes the car a bit narrower, it's easier to build, and I love how it looks, so I think overall it's a good compromise. Borrowed some inspiration from the Hoonipigasus, which is my favorite build ever, while keeping some of the original inspiration from the RP968. This is just a rough sketch for now, but it allows me to start building it for real! I'll clean up these shapes, work on the smaller details, and hopefully start printing soon!

Every time I come to post a new update I look at the last time I posted, and every time I get a bit terrified at how much time has passed, and how little time I have before the first test day.

Parts continue to come in, and I'm slowly plugging away on the car. Got a large shipment from AutoGruppen, including the new ECU, injectors, tons of wiring supplies and manifold parts. The exhaust manifold will be built by AG, so I have to get this mocked up ASAP and send it back to them.



In the meantime I finished mounting the radiator and intercooler. I've also been practicing my aluminum welding, which I had never tried before, so I can weld the AN bungs to the radiator. This is the last step before I can plumb the cooling system.



I also made the final model for the bumper, and it's already 3d printed. After learning from my mistakes with the hardtop, I adjusted the printer settings and added some flanges to the model in order to make the assembly a lot easier, and oh boy, what a difference. Completely fixed the warping issues, and everything just lined up right away. Unfortunately, we can't learn everything at once, so I didn't add any flanges to mount it to the little bit of OEM bumper that is left... it's just to be used as a mold though, so it doesn't matter much, I'll just hack something together.



The driveshaft is done, just waiting to finish balancing and Bronson will ship it out to me, so I should have it in a couple weeks depending on customs and shipping. The axles will also arrive at the same time, I asked him to hold onto them to see if it can be shipped together and save some money on shipping.



I think that's all that happened... fenders are printing right now, lots of work to finalize all the parts for printing now. Cleaning up the model, softening the lines, splitting them up, adding flanges, etc. The wings need even more works, sizing the spars, and making the internal structure, but that's all underway.

Next up I need to mount the electronics and get started on the wiring planning. I do like wiring, but I'm dreading the planning a little bit if I'll be honest... anyhow, no time to waste, so back to work.