[230iZTR]

Originally Posted by F87source

Does the horizontal metal bracket that is currently bolted ontop of everything else touch the inner trunk skin? And is that piece bolted to anything else?

My shop drilled a hole in it and bolted a hard rubber bushing onto the bracket so its touching the trunk. I'll take a photo the next time Ive got the carpet off. They also custom fabbed a thin rubber pad that sits between the bottom of the wing pylon and the trunklid to stop any flex from damaging the paint.

[230iZTR]

Its springtime, and that means another round of mods. Here's what ive got lined up:

- M-Performamce / Drexler 2.81 LSD
- IPOS Motorsports retrofit kit w/m240i half-shafts and aluminum driveshaft
- Turner Derlin Diff Bushings
- Turner Derlin Rear Subframe Bushings
- Replacing APEX 75mm M14x1.25 Studs (they are a wear item!)
- ECS Titanium Locking lugnuts
- M2 LCI open-pore dry carbon interior trim kit (dash, center console, hand brake, gear knob)
- BimmerMasterpiece open-pore dry carbon vents, doorpulls, and gear bezel trim

Im really excited about how the car is coming together overall. Goodbye piano black and grey plastic, hello dry carbon everything. With the diff done, I think I'll have the car as sorted as I can get it until I'm ready to to retire it from daily driving duty.

[230iZTR]

I had a local-ish fabrication shop, Invictus Aero, take my existing eBay front lip and turn it into an air dam by building a proper chassis-mounted alumalite splitter under it.

Its 6mm alumalite composite with around 3" protruding length in front with winglets, extending all the way back to the front axle. Its sized to imitate the F82 M4 GTS's splitter proportions at full extension to offset the F8x M4 GTS wing I already had on the car. I also have some rubber piping on the leading edge to protect it from impacts with autocross cones and SlipLo pucks on the bottom to prevent scraping

I havent seen too many chassis-mounted options for our platform, so it was quite the undertaking. The only similar chassis mounted splitter kit I've seen is from Artwork Bodyshop out of Canada, and their M2 unit was way too big for my narrower 230i. I think MFR Engineering, a staple of SoCal BMW racing, has made similar one-off kits but I couldnt find any info online. Dylan at Invictus knocked it out of the park.

[F87source]

Originally Posted by 230iZTR

I had a local-ish fabrication shop, Invictus Aero, take my existing eBay front lip and turn it into an air dam by building a proper chassis-mounted alumalite splitter under it.

Its 6mm alumalite composite with around 3" protruding length in front with winglets, extending all the way back to the front axle. Its sized to imitate the F82 M4 GTS's splitter proportions at full extension to offset the F8x M4 GTS wing I already had on the car. I also have some rubber piping on the leading edge to protect it from impacts with autocross cones and SlipLo pucks on the bottom to prevent scraping

I havent seen too many chassis-mounted options for our platform, so it was quite the undertaking. The only similar chassis mounted splitter kit I've seen is from Artwork Bodyshop out of Canada, and their M2 unit was way too big for my narrower 230i. I think MFR Engineering, a staple of SoCal BMW racing, has made similar one-off kits but I couldnt find any info online. Dylan at Invictus knocked it out of the park.

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Looks awesome!

But imo (and no offense) if you're serious about aero and down force you should remove the slip low - especially since it's near the leading edge. This is because the slip low will cause flow separation right on the leading edge and that badly hurts down force generation along the entire underside of the splitter.

[230iZTR]

Originally Posted by F87source

the slip low will cause flow separation right on the leading edge and that badly hurts down force generation along the entire underside of the splitter.

I doubt the SlipLo has much effect in the real world. Its like 3/16" thick and tapers down to near-flush. It might be worth a few percentage points of additional downforce to run a splitter thats totally flat and sharp as a knife on its leading edge...but this isnt F1. The car's turbulent and non-flat underdercarriage - and my finite budget! - means I'm never going to be able to implement the theoretically optimal CFD solution.

[F87source]

Originally Posted by 230iZTR

I doubt the SlipLo has much effect in the real world. Its like 3/16" thick and tapers down to near-flush. It might be worth a few percentage points of additional downforce to run a splitter thats totally flat and sharp as a knife on its leading edge...but this isnt F1. The car's turbulent and non-flat underdercarriage - and my finite budget! - means I'm never going to be able to implement the theoretically optimal CFD solution.

The leading edge is one of the most important part of the aero surface, because it influences how the air behaves over the entire aero surface right after it. So I would suspect the slip low being so close to the leading edge - especially with it's serated trailing edge, to have alot of turbulent vortices shed off the end, this will horrificily effect down force generation, and with the limited surface area we have to work with on these cars, every bit counts.

Second you wouldn't want a razor sharp leading edges (trailing edge is ok), because that makes the front splitter extremely susceptible to flow separation because a sharp leading edge causes a massive adverse pressure gradient. That's why you'll notice all leading edges on f1 wings are rounded and are never sharp. It's why your splitter also has that tape on it to make it rounded.

Here's a video by Kyle (former Mercedes F1 aerodynamic ist explaining it, Kyle also has a PhD in this field and worked for Merc in their glory days - i.e. the w11 which is the fastest F1 car in history):

[230iZTR]

Kyle says in the video you linked that Reynold's effects are not as big a factor as most people would assume. Check it from ~3:00 to 3:32

[F87source]

Originally Posted by 230iZTR

Kyle says in the video you linked that Reynold's effects are not as big a factor as most people would assume. Check it from ~3:00 to 3:32

But that's associated with a generic aero surface and the viscosity of a fluid and the speed of the flow of said fluid. This doesn't have anything to do with the characteristics of an aero surface. So even though Reynolds number is not a major deal, having a crappy aero surface is still a big deal, especially if you're trying to extract the maximum performance out of an aero surface and this is even more important when an aero surface is small.

If you look at verus engineering (makes some incredible aero parts) they try their hardest to keep the aero surface clean and mitigate screws and bolts to key areas to not trip up flow. They also try to recess screws when possible, and use extremely small rounded screw heads to prevent turbulence around the screws.

[230iZTR]

I agree. Im aware it could be made even more efficient in the future. Eventually I'd like to up the thickness to an even stiffer 10mm plane, replace the SlipLo with a few Professional Awesome titanium skid pucks, replace all the hardware with flush mounted pieces, mate the air dam to the splitter a bit better, add diffusers to the splitter's trailing edge, vent the fenders, replace the hood with a GTS carbon unit, flatten out the floor as much as possible, remove the muffler, and fill in the space it left behind with a diffuser that extends all the way to the rear axle.

But for now, 3/16" of SlipLo is fine for intial testing of a one-off prototype. I know I'm leaving some downforce and aerodynamic efficiency on the table that can be improved upon later. But this is better than no splitter at all, and the GTS wing is moderately sized to begin with so it doesnt need to push out huge numbers to balance it out.

The M4 GTS splitter looks like it has some features that introduce turbulence as well (adjustment slots, a big gap at the trailing edge to the front tray) and it still manages to put down 150+ lbs of downforce at 100mph.

[F87source]

Originally Posted by 230iZTR

I agree. Im aware it could be made even more efficient in the future. Eventually I'd like to up the thickness to an even stiffer 10mm plane, replace the SlipLo with a few Professional Awesome titanium skid pucks, replace all the hardware with flush mounted pieces, mate the air dam to the splitter a bit better, add diffusers to the splitter's trailing edge, vent the fenders, replace the hood with a GTS carbon unit, flatten out the floor as much as possible, remove the muffler, and fill in the space it left behind with a diffuser that extends all the way to the rear axle.

But for now, 3/16" of SlipLo is fine for intial testing of a one-off prototype. I know I'm leaving some downforce and aerodynamic efficiency on the table that can be improved upon later. But this is better than no splitter at all, and the GTS wing is moderately sized to begin with so it doesnt need to push out huge numbers to balance it out.

The M4 GTS splitter looks like it has some features that introduce turbulence as well (adjustment slots, a big gap at the trailing edge to the front tray) and it still manages to put down 150+ lbs of downforce at 100mph.

If you're willing to go that extreme you should get cfd work done, OG shark has done that for his m2c and his aero looks legit. Then you should track test with flow vis to verify if the cfd work correlates. Because adding diffusers in and not know the air flow situation around these parts could yield little to no beneficial effects. Verus aimed it at the gap between the tire and chassis in order to promote as much ventilation as possible and thus make the diffuser work - they talk about this on their YouTube channel.


The gts splitter only makes 63 lbs of downforce at 183 mph as per the technical documents. It's no where near the 150 lbs, even the rear wing doesn't make that much down force at 100 mph, and 100 mph is actually pretty low speed for aero.

That image you posted isn't a real GTS car, a real GTS has a stiffening plate cover that improved air flow from the front splitter.




Also the losses induced by the gts splitter hardware is further backwards and in fewer less critical areas vs. the slip low which covers the entire leading edge - an extremely critical area. Your slip low also has a serrated trailing edge and that's more likely (can't confirm without flow vis) to create turbulent vortices across the entire splitter underside, thereby hurting aero.

[dradernh]

Originally Posted by F87source

If you're willing to go that extreme you should get cfd work done

I went to Simon McBeath for a general evaluation and recommendation for improved aero for my E36 race car.

It was money well-spent, especially in terms of his sharing general principles applicable to motorsport-level improvements to a street-based chassis.

I recommend him highly. No affiliation.

http://www.sm-designs.co.uk/

[F87source]

Originally Posted by dradernh

I went to Simon McBeath for a general evaluation and recommendation for improved aero for my E36 race car.

It was money well-spent, especially in terms of his sharing general principles applicable to motorsport-level improvements to a street-based chassis.

I recommend him highly. No affiliation.

http://www.sm-designs.co.uk/

Personally I'd go directly to Kyle Forester, aka the guy in the video, for race car consulting. It's hard to discredit what he has done in motorsports and his track record.

[msendit]

We run a simple flat splitter on my 2er. The racing rulebook for the class we run is pretty limiting in terms of what we can do (vertical air dam, flat 4" splitter back to the front axle). Mounted to the bumper support and front subframe, will probably need an extra support point in the front somewhere. Mostly optimized for cheap and easy to replace -- splitters break all the time in racing.

At least on the 6-cyl B58, with how cramped the engine bay is, opening a hole or two in the bottom (like the OEM undertray) helped significantly with cooling the car overall.

This one folded in half last weekend after an off:


Looks like this usually:

[F87source]

Originally Posted by msendit

We run a simple flat splitter on my 2er. The racing rulebook for the class we run is pretty limiting in terms of what we can do (vertical air dam, flat 4" splitter back to the front axle). Mounted to the bumper support and front subframe, will probably need an extra support point in the front somewhere. Mostly optimized for cheap and easy to replace -- splitters break all the time in racing.

At least on the 6-cyl B58, with how cramped the engine bay is, opening a hole or two in the bottom (like the OEM undertray) helped significantly with cooling the car overall.

This one folded in half last weekend after an off:


Looks like this usually:

Alumalite?

I used to use that stuff all the time on my frs. It was relatively cheap, strong, lightweight, and easy to work with.


I also wanted to mention down force is a function of ride height as well, so just because the GTS makes X amount of down force doesn't mean the same part on a different car will make the same down force.

Rake angle will also help with some down force generation, so naturally the m2 with it's rake from the factory will help with that - however if you run rake it becomes even more imperative to have a rounded leading edge on your splitter. So I suggest you add some rubber edge trim to round off the leading edge on your splitter.

[dradernh]

Originally Posted by F87source

It's hard to discredit what he has done...

Is anyone seeking to do that?

[F87source]

Originally Posted by dradernh

Is anyone seeking to do that?

Generally when I post his videos people immediately discredit him because they think he's just a YouTuber. So the preamble was just there to preemptively quash any of the potential naysayers.

[F87source]

I also wanted to add that op's front splitter is still quite good, it's going to make down force, I'm just nitpicking at the minor details in order to try and squeeze as much down force as possible from the front splitter. Because for a simple splitter like this, it is likely not going to be making huge down force numbers so every single bit counts.

[mecheng77]

Wow quote the extensive build, how much do you got into it?

[230iZTR]

Got some high quality pics!

[Ghost2018]

Originally Posted by 230iZTR

Got some high quality pics!

Hi Mike!! Killer build you have going on there and the wife and I love it! She doesn't do the "forum thing" at all, but I do, so I decided to make a profile here for her. She too has an Alpine White 2018 230i and I was just searching for people and sources that are about the 2 series, or have owners of the same car, which seem to be very few when it comes to the 230i. Are you the only 230i owner here? I can't seem to find anyone else, lol. I myself am a lifelong gearhead so I have had my fair share of performance cars and custom vehicles, but for her this is her first time in terms of any type of automotive modification. She bought the car mainly as something to play with so that we could share the hobby together, but lately she has become extremely frustrated with what seems to be next to zero support for this platform. Yes, she knows that she would have had much more to choose from had she gotten an M2, but something about the 230 drew her to it more. She is more into aesthetics than performance, but she won't turn down the chance to make more power either. The car is mostly stock with only a Dinan CAI setup and an ECS charge pipe kit. The car has been frustrating me also as I have been trying to help source parts in any way possible but continuously come up short. I find it odd that I can't even find simple engine dress up parts like oil caps and other reservoir caps, engine covers, or strut top covers. She also wanted to do a front and rear M bumper swap, but is that even possible? I'm honestly afraid that as much as she does love the car, she will get rid of it out of frustration.