Really Should Stop Modifying my Daily Driver into a Track Car

[M-Sport fan]

I thought that you were originally talking about wicker bills for the REAR wing element, not the front splitter.

That car is starting to look like it should have big flares over the wheels.

 

[Fusion Works]

Barber with SCCA.

First loser in class. 6th or 7th overall out of 20. I was so slow it wasn't that important.Car was better, had a shit ton of grip. Too much in my opinion. Couldn't get the rear loose enough. Started with 450/550 setup, add four rubbers to each rear spring. Won't know rate until I pull the rear spring and measure its packed rate. I expect the rate to be in the 700lb range. I dropped the rear Wang down to 1 deg up so its not providing a massive amount of down force.

Suspension is -2.25 front camber, .010in toe out. (basically none), 5+deg of caster (need to re-measure), rear camber is -2.5, toe .075 out. Tires are Maxxis VR1. Tires are wearing like iron.

Front splitter was fantastic. I have just a little wear on the bottom near the front edge. Friend said he saw sparks from the Titanium blocks going unto turn 1. YAY.

The car was still pushy. It never tried to kill me and I was sliding it through turn 1 and through the kink. It needs MO LOOSE!!

Still waiting to see who took pics of cars on track and if they got the Fiesta. Should have been many opportunities to see sparks.

 

[Fusion Works]

Tested rear spring. Starting rate was 550lbs. With rubbers as tested, 650lbs/infor the first inch. Yhem it ramps up to 1050lbs/in for the next inch. I didn’t test it past two inches as my scale tops out at 1500lbs. I expect the next inch to be 1800lbs+/in.

 

[WannabeST]

I didn't realize how low the splitter was built until this picture lol. Looks awesome.

 

[Fusion Works]

It meets the SCCA Max 3 rule of 3in to the ground. Now its a piece of LoweDepot Motorsports' finest composite so flatness is +- .500in across the span. LOL. So maybe the center is 3 and the corners might be 2.5in but who is counting the details. Under the hardest braking with the 450lb front spring it won't touch the ground. It barely kisses the ground when the track changes or I brake and go over some of the curbing. To me that is perfect, close enough to seal the ground yet high enough to flow properly at speed.

Yeah I shot a pic over to @dtulley with the garden hose under it for a reference. Hoping the track photograpy folks got some good pics of the car on course so I can analyze how it looks at attitude.

 

[M-Sport fan]

I know you are asking about the stiffer/latter rear beams to help cure this 'push' problem in other threads.

Is the reason you don't want to just put a huge rear bar on it a fear of that causing uncontrollable 'snap' oversteer, and desire something much more subtle?

 

[Fusion Works]

I have an Eibach 21mm solid is there anything bigger in the aftermarket? To answer your question, no I would absolutely put a stiffer rear bar on it. Debating designing a 32mm hollow bar, maybe a .250 wall thickness. Have concerns about heat treating it. In the past have built bars for my Integra using 4130 but they were pretty short. Have to be careful not to go over board. Maybe I can build a couple and test without having to heat treat them and see what happens.

Pretty sure I have the 8.5mm thick beam. Feel like I measured this when I first got the car. Its not covered with the beam panel, so I can't measure it easily with the car on the ground.

The reality is this is probably the answer that I don't want to deal with.

 

[Fusion Works]

If you want to nerd out:
https://www.a-sp.org/wp-content/uploads/2020/08/Lightweight-Twist-Beam-Final-Report.pdf

https://www.slideshare.net/altairhtcus/ukatc2015-gestamp

 

[M-Sport fan]

I think that someone makes a bolt-on 22mm, but that is still too small for your needs.

Given your fabrication skills, the aftermarket would not be your limiting factor (as you've already stated above ).

 

[Fusion Works]

HAHA, it is not. Already playing with calculation and material selections for new BIGGER rear bar.

I currently have the Eibach 22mm bar. Its solid.

 

[Fusion Works]

More beam axle nerd stuff:

https://sci-hub.se/10.4271/810420

http://www.auto-ware.com/ortiz/ChassisNewsletter--October2006.htm

https://www.eng-tips.com/viewthread.cfm?qid=281089

https://www.sae.org/publications/technical-papers/content/2013-36-0232/

https://pdfs.semanticscholar.org/bdf3/c2e39ee4ce99268a72b1377953bd983a802c.pdf

 

[Dialcaliper]

Whiteline makes a 22mm solid rear bar you might look into. The other option if you want the rear stiffer is to double up (rear bar like the Whiteline plus a beam stiffener like the one from Pierce or TB.

Alternately, if you can’t find a front bar closer, I have the 19mm I took out when I swapped in the UR front bar, but I’ll say dropping the subframe is a decent amount of work, and do the steering rack bushings while you’re in there.

Be careful with sizing the rear bar if you try something custom. Sway bars are quite sensitive (4th power) to diameter. 32mm would be ludicrously stiff, probably a lot more than you’d be looking for. Using the front as an example, the Eibach 25mm bar is fully twice as stiff as a the late ST 21mm bar and makes the car understeer even with the biggest rear off-the shelf rear bar.

The rear is a little different because you’re stiffening the torsion beam, but the 22mm Whiteline bar increases rear stiffness by about 50%. A 25mm bar would be close to doubling. 32mm rear and you’re looking at about 4x stiffness compared to stock, which is probably borderline undrivable.

 

[M-Sport fan]

Be careful with sizing the rear bar if you try something custom. Sway bars are quite sensitive (4th power) to diameter. 32mm would be ludicrously stiff, probably a lot more than you’d be looking for. Using the front as an example, the Eibach 25mm bar is fully twice as stiff as a the late ST 21mm bar and makes the car understeer even with the biggest rear off-the shelf rear bar.

The rear is a little different because you’re stiffening the torsion beam, but the 22mm Whiteline bar increases rear stiffness by about 50%. A 25mm bar would be close to doubling. 32mm rear and you’re looking at about 4x stiffness compared to stock, which is probably borderline undrivable.

I understand what you are saying, and I'm sure that Brett does as well.

But, he is using sticky tires, and can dial-in the angle of attack on that rear wing's element to give massive downforce.

I also think that a 32mm rear bar would be ridiculous, even if made out of a thinner wall chromoly, but a 25mm or so made from a medium gauge chromoly might not be.

I suspect that's why he wants to build a few of them and test them all.

 

[Dialcaliper]

I understand what you are saying, and I'm sure that Brett does as well.

But, he is using sticky tires, and can dial-in the angle of attack on that rear wing's element to give massive downforce.

I also think that a 32mm rear bar would be ridiculous, even if made out of a thinner wall chromoly, but a 25mm or so made from a medium gauge chromoly might not be.

I suspect that's why he wants to build a few of them and test them all.

25-27mm would not be unreasonable at all on a car seeing mainly track. It ultimately does come down to testing in real life, that’s for sure. 🤣

 

[Fusion Works]

Yeah I am thinking a 1in peice of solid bar will be a good place to start. Bend it up and bolt it on. See how the car feels when I go back to Barber. I may look and see if I have some 1.25 Chromoly laying around I don't think I do currently, but yeah, the 1in bar is almost twice as stiff as the current 21mm Eibach (1.75times stiffer) and the 32mm bar could be 4.2 times stiffer than the Eibach if i use a solid bar. A .125 wall would get me 2.5 times stiffer than the Eibach.

Should be easy enough to test a few setups. The car needs to rotate better. Its not scary now but I don't want to be running 1000lb rear springs just to get the car to rotate properly.

 

[the duke]

So the wickers are attached to the single screw and the original front tire spats. I riveted them to the remains of the rubber pieces. They are not very stiff. i am not thrilled with them.
On the way home tonight I was thinking about a way to attach them to a bracket on the splitter without requing more than a pin to remove the splitter. View attachment 57500 View attachment 57501
Preliminary scale numbers. I am fairly happy with it. May lower the rear a little or not. Final tweaking and then some some driving tomorrow.
View attachment 57502

 

[Fusion Works]

Stop giving away my secrets. HAHAHA

 

[Fusion Works]

Got with the track photographer and have one pic. She is working on the rest of them for me.

Looks like a need a bit more rigidity on the nose of the splitter.

Think this is going into turn 1 climbing up to turn 2.

 

[Fusion Works]

Not bad for 30+ laps at Barber.

 

[Fusion Works]

Finally got some pics from the track photographer.
Going into turn one. Splitter is just closing off the airflow under the nose perfectly under braking.

Never give up:

HAHA, pit lane exit for me.

You can see me waving my hands because this squirrel in the EVO just goes darting off line towards the pit wall as we came onto the front straight. Thanks for the point by but don't do squirrel shit. Hold your line and I will pass you when I have a clean opportunity.

Can see the front end isn't really rising up much under full acceleration. That is good. Those 550lb rear springs doing their thing.