Splitter / Undertray recommendations?

[Mick]

It's long overdue but I finally removed my heavy, and probably useless, "EVO 5" style splitter. I installed it 13 years ago and I must have had 2lbs of fasteners holding it on.

I'm not sure what I'm going to replace it with yet. As I understand it, it's just as important to have the splitter extend under the car as it is to project in front. Unless there's a good solution out there It seems like I'll have to make my own.

Any suggestions, recommendations, humorous anecdotes?

Pic of the old E5 splitter

[Ironhead]

Mick, I'm currently going though this with my "other" car. Surprisingly difficult to find a material affordable, strong enough, and reasonably lightweight.

Carbon fiber: Too expensive in the size needed.

Fiberglass: Also surprisingly expensive...you need a big sheet perhaps .1875" thick.

ABS Plastic: I tried .25" thick ABS. Affordable and reasonably light, but too flexible unless you want to use a LOT of turnbuckles to support it.

Tegris: Used on a lot of high end racing car splitters. Cool stuff, but pretty much as expensive as CF.

Alumalite: Affordable, stiff and light, but very prone to edge damage and then looks like hell. I think it also only comes in white....

Plywood: Lots of racers use .5" plywood....all accounts are that it works well....but...I....just....can't....

Aluminum: Expensive in the size needed and heavy. Also you are basically driving around a car with a knife blade on the front.

Aluminum honeycomb sheet: Checks all the boxes....stiff...light...but expensive. Around $500 for a large enough piece. Also has fragile edges.

I think the best combination of features and cost is .1875" thick structural FRP fiberglass sheet. A 48" X 96" piece (smallest available that would work in one piece) is a bit over $300 from McMaster-Carr...but could probably be had cheaper elsewhere. Also, I've never found it in black....usually is green....so you'd probably want to paint it.

The biggest problem is that I cannot find any of this stuff local, and shipping such large sheets is a killer.

[jimmy p.]

I use Alumalite and then I seal the leading edge with some assorted different things. Epoxy works, so does construction adhesive.
Its pretty light, stiff, pretty tough until you try to punt cones with it at speed. A cone can dent it, but it isn't too hard to repair.
The best part about it is its inexpensive. Splitters are really really almost consumables. I couldnt even begin to fathom using anything expensive for one.
If you go to a local sign company and buy the used "take down" signs they sell them really cheap (your just gonna paint it black anyway lol).

There is another sign material in the same vane as alumalite that I think Dave Swernoff is trying out, I forget the name though. Sounds super promising from the description. It sounds like it might be a better product than alumalite.
I'll probably try a piece next time I need to make one, as I am just about out of splitter size cuts from my last sheet of alumalite.

I usually space it down with around a 1" thick piece of the high density styrofoam to get it lower (kind of a ghetto version of the DTM92 bumper spacer).
I coat the leading face of the styrofoam spacers with a non-solvent based body / seam sealer then spray all of it with a hard kote type of truck bed paint.
Its all fairly light for how large it is and are pretty durable given the abuse they get.

The biggest issue with the Evo 2, the Evo 3, the Evo 5, just fastening a piece of anything to the bottom of the bumper cover is its too high.
We need to space whatever it is down as low as possible to the track.
The old Westchester fiberglass exaggerated Evo 2 type bumpers also incorporated a pretty substantial addition of material to get it lower.
Thats the key.

I am by no means an aero educated person, but I know we want to get whatever option of material we do as low as possible.
If its sitting way up in the air its not really doing much.
Also all this stuff we have to think of not as generating "downforce" like a real race car. None of us are going to do that with a splitter or air dam.
What we are doing is trying to eliminate front end lift. Keeping air from getting under the car with the lowest amount of drag possible.

[Mick]

Thanks for the list Ironhead, that's really helpful. I was also considering ABS but will pass after hearing your feedback.

Jimmy, how far under the car are you extending it? Are you using rear supports?

One reason I'm hesitating on lowering the splitter is that I'd like to avoid creating a situation where the bumper has to come off every time I load it onto the trailer. I know being low is important but so is making track days a little less painful. Since I have the E5 splitter off of the car right now I can measure the approach to my trailer ramps and see how much drop I have to work with.

I have an old take-off splitter here that's in need of repair. I was considering mending it and giving it a try. It drops the splitter down about 1.75" but it doesn't extend under the car at all. Maybe that's not as much of an issue as I think.

Here's a pic of the old splitter (top). Anyone know who made it?

Another option is to slap my old CF splitter on the bottom of the bumper without the E2 lip. I haven't done it yet because I thought I wanted something that extends under the car further. Also, because it's not lowered I wonder if it's worth having at all.



Because it's a little narrower than the M3 bumper it may have been made for a regular E30

[1990m3]

Jimmy called me out so I’ll show you what I did. I bought a sheet of alumalite from a sign store (it was actually their scrap that I got for free!). It has a foam core and aluminum on each side, about 3/26” thick and seemingly stiff enough. I will be adding rear frame supports to the frame rail as it looks easy to do.

I painted it with plastidip in hopes that it won’t chip out as bad as regular paint. Took about 1.5 hours to make, cut like butter with my jigsaw and bimetal blade

[Ironhead]

If it helps anyone, I think the best/cheapest/most convenient stuff for painting splitters is Raptor Liner. You can get it locally at many auto parts stores, it is a two part product that is tough as hell once cured, and you can apply it with a very cheap spray gun that they sell for that purpose. You can even apply it with a brush or roller and it comes out looking decent.

It has a textured finish so it is also really easy to touch up. Get a scab of it knocked off, just mix up a small batch and dab on some more with a brush. The more I use this stuff the more I like it.

[HANDBLT]

I am using ABS that came on another car I bought. It goes back all the way to the steering rack. It has vertical supports at the wheel wells and is connected to the bumper like Swernoffs. I used the turn buckles on the front because it sticks out pretty far. I know I need to get the car lowered (those are EVO III fenders so the gap looks larger) but I keep my cars at stock ride height to keep the suspension geometry correct. Next winter I will be raising the pick up points so I can get the car down lower. This year is just going to be shake down events to work out all the mechanicals and temps.

[1990m3]

yes, the vertical supports underneath seem like they would help a lot. I briefly looked at it the other night and think it will be easy to do -- add it to the list!!

[jimmy p.]

Mine looks pretty similar to Dave's. I think his might come back a little farther than I make mine.

On my cars I 100% have to remove the bumper to get it in the trailer. I used to be able to squeak by on my old trailer with a silly assortment of wood pieces, but when I got my new trailer in 2016 I ordered it with 5K axles and those come with 16" wheels and way bigger (taller) tires, the deck height from ground was higher, which made the ramp door steeper which made all the assortment of wood bits I needed just ridiculous so I just opted to pull the bumper. I have it down to an easy repetition. I made some support slider wood pieces with teflon sliders I place on the ground in front of the car and it pretty much slides right onto its mounts.

I had (I searched and cannot find it) a picture of a very clever, tubular under bumper structure that someone did on an E30 that incorporated a bumper support for a FG bumper cover AND drop down splitter supports that transferred all the splitter load direct to the chassis and none through the bumper cover. Thats the way to go.
I have a picture of it in my head, I just ned to build it. It requires some tube bending which I'll need outside help with. A project for maybe next winter.

[1990m3]

Mine looks pretty similar to Dave's. I think his might come back a little farther than I make mine.

On my cars I 100% have to remove the bumper to get it in the trailer. I used to be able to squeak by on my old trailer with a silly assortment of wood pieces, but when I got my new trailer in 2016 I ordered it with 5K axles and those come with 16" wheels and way bigger (taller) tires, the deck height from ground was higher, which made the ramp door steeper which made all the assortment of wood bits I needed just ridiculous so I just opted to pull the bumper. I have it down to an easy repetition. I made some support slider wood pieces with teflon sliders I place on the ground in front of the car and it pretty much slides right onto its mounts.

I had (I searched and cannot find it) a picture of a very clever, tubular under bumper structure that someone did on an E30 that incorporated a bumper support for a FG bumper cover AND drop down splitter supports that transferred all the splitter load direct to the chassis and none through the bumper cover. Thats the way to go.
I have a picture of it in my head, I just ned to build it. It requires some tube bending which I'll need outside help with. A project for maybe next winter.

I'm testing it on track on Monday, I'm totally going to have to pull the bumper off for loading and unloading. My wood ramps need work too -- think I'm going to move to some race ramps, everyone has them at the track and they are lightweight, durable, and I'm always jealous

Next up in the front aero dept for me is a hood vent!

[jimmy p.]

I'm testing it on track on Monday, I'm totally going to have to pull the bumper off for loading and unloading. My wood ramps need work too -- think I'm going to move to some race ramps, everyone has them at the track and they are lightweight, durable, and I'm always jealous

Next up in the front aero dept for me is a hood vent!

Honestly the bumper removal now for me is 2nd nature, I dont even notice it, its part of my routine like checking oil and torquing lugs. The nice thing is you never ever have to worry about crunching anything. I drive my car into the trailer just using the ramp door. No extensions at all. I hated carrying around extra wood and ramps, etc. I have two little boards that I bump up to the ramp door when the ground is not level thats it. I like that aspect.

As I told you via text, the hood vent is real world help. I saw the difference in the amount of bulge my FG hood had before and none after.

[1990m3]

Honestly the bumper removal now for me is 2nd nature, I dont even notice it, its part of my routine like checking oil and torquing lugs. The nice thing is you never ever have to worry about crunching anything. I drive my car into the trailer just using the ramp door. No extensions at all. I hated carrying around extra wood and ramps, etc. I have two little boards that I bump up to the ramp door when the ground is not level thats it. I like that aspect.

As I told you via text, the hood vent is real world help. I saw the difference in the amount of bulge my FG hood had before and none after.

I'm tired of the wood ramp routine, but the race ramps will bungee nicely up against the side wall so I'm going for it. As for the hood vent, I have a heavy but very still VIS CF hood. Great hood for a track car and fortunately it doesn't flex at speed. I have a friend with a flimsy fiberglass version and he had to add a third hood pin by the roundel to make it stay down. I'm hoping the vent aids a tiny bit with cooling and puts a little downforce on the front end. I'd be disappointed to chop up my hood if I don't go any faster....

[Mick]

Jimmy called me out so I’ll show you what I did. I bought a sheet of alumalite from a sign store (it was actually their scrap that I got for free!). It has a foam core and aluminum on each side, about 3/26” thick and seemingly stiff enough. I will be adding rear frame supports to the frame rail as it looks easy to do.

I painted it with plastidip in hopes that it won’t chip out as bad as regular paint. Took about 1.5 hours to make, cut like butter with my jigsaw and bimetal blade

Thanks for the pics, that looks like the way to go. I'll call around to some sign shops on Monday and see what I find.

[Mick]

Did you guys do anything to make your brake ducts simpler to release/attach when removing the bumper? Hose clamps aren't a big deal but it would be nice to find something that was quick release.

What about the intermediate undertray that goes between the wheel wells? Ditch it?

[1990m3]

I don't have a tray between the wheel wells anyway, my new splitter takes up that area anyway.

In all honesty I haven't been using my brake ducts lately, been experimenting with letting the brakes get hotter and the results have been good so far. I also haven't tried temp paint yet to get a gauge on what heat I'm seeing but I can say with certainty that I ducted the brakes no matter what in the past and wasn't 100% satisfied with my brake performance, so now I took the hoses off and I believe I can tell the brakes are working better with the additional heat they are getting.

For reference I have Massive front and rear brakes, 300mmx32mm on both axles. 6 piston front and 4 piston rear and I use a manual DTM pedal box with a balance bar and no ABS. Frankly, my brakes are more consistent now than they've ever been