S197 3V Fabman's build; How did we get here? Build Thread

[Mad Hatter]

Two questions:

Is there room to redirect some air from the 4" duct directly back to the caliper? Might give the fluid a break.

Is there enough height on the rear spring stack for an even longer spring? In terms of motion, I always went for the maximum compression capacity, which translates to the biggest difference between the static loaded length and the block length. Every inch of free length gives you a bit more. It keeps the spring from acting as the bump stop.

I think you can use a 10" spring with upto a 295 tire. Thats for the cortex coilovers. Any bigger and it would rub.

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[Fabman]

I think you can use a 10" spring with upto a 295 tire. Thats for the cortex coilovers. Any bigger and it would rub.

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8” is the tallest spring that will fit with these wheels.


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[Fabman]

Two questions:

Is there room to redirect some air from the 4" duct directly back to the caliper? Might give the fluid a break.

Is there enough height on the rear spring stack for an even longer spring? In terms of motion, I always went for the maximum compression capacity, which translates to the biggest difference between the static loaded length and the block length. Every inch of free length gives you a bit more. It keeps the spring from acting as the bump stop.

The backing plate is vented in such a way that whatever air doesn’t go through the vanes of the rotor exits the eye past the caliper. As a bonus, these calipers have much more clearance. The old ones needed to be sanded in spots to get the wheel over it. These have breathing room.


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[JAJ]

Sound brilliant! Looking forward to hearing how it all works!

 

[Fabman]

Two questions:

Is there room to redirect some air from the 4" duct directly back to the caliper? Might give the fluid a break.

Is there enough height on the rear spring stack for an even longer spring? In terms of motion, I always went for the maximum compression capacity, which translates to the biggest difference between the static loaded length and the block length. Every inch of free length gives you a bit more. It keeps the spring from acting as the bump stop.

Get some coffee, this is going to be a sermon.

Agreed, beyond the coil stacking effect, my concern was the non linear unloading of the spring.
With a long spring the load is removed across a wider band of movement and therefore more linear i.e. predictable giving a more stable transfer of weight.
With a spring of equal rate but shorter length it is possible to unload it to a point that it no longer is contributing to the wheel rate, thereby increasing the effect of the rear anti-roll bar since the spring is no longer acting against it. Net affect: Snap over steer. This is what I was experiencing. Understeer followed by snap oversteer.

Of the multitude of changes I made to this previously neutral handling car the primary ones affecting balance are separated into 2 groups:

Mechanical grip:
1) lengthening the polar moment via shifting weight towards the ends of the car.
2) reducing the overall rear weight percentage via removing the large intercooler tank and relocating a much smaller one forward of the front axle, while moving the fuel load rearward via fuel cell install. (This results in #1)
3) Increasing front spring rate from #500 to #600
4) increasing rear spring rate from #325 to #350
5) reducing the rear spring free length by 1.0"
6) increasing static camber from 2.75* to 3.2*
7) Increasing track width 1" more on the front than on the rear
8) increasing scrub radius. (result of #7)
9) increased anti squat while simultaneously increasing roll steer via trailing arm angles.
10) reduced front ARB rate.
11) Softened front shocks

Aerodynamics:
1) adding a massive rear wing
2) adding front aero via larger splitter, canards, spats/deflectors and hood vents.

All other changes are assumed to affect the car without favoring either end of the handling spectrum. i.e. overall weight reduction, increasing the contact patch equally on all 4 corners, resolving fueling issues, careful placement of an official TMO decal etc.

Assessment:
#1 is undesirable, but made necessary by #2. I'm just going to have to live with it.

#2 was a necessary change resulting in #1 but resolved my prior fueling issues.

#3 the reason I upped the spring rates is that by viewing on track pictures and then removing the springs and photographing the car at full static bump I determined that the car was indeed bottoming out in sections of the track and additionally exhibited excessive body roll in certain corners. Front shocks were also adjusted at -4 clicks meaning almost full stiff. My strategy has always been that if you are to the extreme ends of any range of adjustment, you are likely covering up some other inadequacy. So begin looking at root causes rather than symptomatically. In this case, roll couple, roll couple distribution and roll axis. Since the roll axis was un changed, I deferred to roll couple. Now while stiffening the front springs I also reduced the front sway bar effective rate and also softened the front shock rate from -4 to -14. I had previously stiffened the front roll bar rate and while the affect was a tighter exit, it was too tight, so I went with additional spring rate instead. Maybe at that point I should have also increased the roll axis, but I didn't. With this level of power, I tend to shy away from anything that would reduce traction at the rear. That may have been a mistake, but that's how I handled it that day.

#4 was to help limit bottoming and also help balance the front spring increase by shifting the roll couple distribution forward less than otherwise.

#5 the logic behind the shorter free length is that the offset on these wheel would have the coil over adjusters contacting the wheel before full droop. So I shortened the spring with a suspicious eye on it, expecting the possibility of it being a double edged sword.
Yesterday I looked things over very closely and determined that by removing the helper spring arrangement that i could get 1 more inch of spring and not have an issue of the spring falling out of the seat under full droop, so I went for it.

#6 was also done with some trepidation. 2.75 was not enough camber with the 295's so with 335's wider tread width, even at the same camber angle, it would position the outside edge of the tire farther off the tarmac which in effect would be like adding additional camber. So it is possible that these two effects compounding resulted in less overall grip. Front tires still exhibited more roll over than I would like to see so I may have a combination of insufficient pressure and excessive camber. I don't have a crew so its not practical to get tire temps even though I carry all the necessary gear to collect them so I have to look at wear patterns instead. Where's @blacksheep-1 when I need him?

#7 was dictated by the width of the flares. I simply can not poke the rears out any more and can't bring the fronts in any closer to the struts.

#8 Increasing scrub radius was dictated by the wider wheel and offset required for fittment.
A compromise at best.

#9 I had previously put a go pro on my rear suspension to watch for bottoming and noticed that in my effort to lessen roll steer the trailing arms under acceleration and in corners was actually spending more time on the wrong part of the curve than the right part. So, I changed the brackets to ones with more holes with a finer adjustment.
Instead of 1* up I went with 4.5* up. The affect should be a looser apex as the car roll oversteers and then a tightening up as the car flattens out with the additional anti squat provided by the trailing arm inclination.

#10 softened front ARB to compensate for increased spring rate.

#11 Softened front shocks to compensate for increased spring rate.


At the track:
First thing I did was lessen the wings angle of attack from about 3* to 0* with some improvement. Not much I know to do about shifting the center of aerodynamic pressure forward besides the fender venting that I am working on now so that remains unchanged at the moment.
Then we added some toe out for the next run. (1/4 turn on the tie rod) Later at the shop I measured it at 5/8" total toe. Way more than a quarter of a turn should give us.
Then I softened the front shocks from -14 to -21 (car was pushing-logic tells us to reduce wheel/shock rate right?)
Added 4 psi to tires. No improvement so I went back to baseline.

What I believe was happening was that the reduced shock rate and ARB rate was not supporting the additional spring rate and giving me even more bottoming than before. Result: the dreaded Battleship push.
Additionally, as weight transferred diagonally, the inside rear would reach the end of the springs useful extension and unload which would thereby increase the rear ARB's effective rate as mentioned previously resulting in snap over steer. Maybe snap oversteer is a little misleading, More like any amount of power added would suddenly switch from understeer to over steer, so somewhere between snap oversteer and power oversteer.

In conclusion:
I basically took a perfectly balanced race car and induced both over steer and understeer while simultaneously lowering lap times by a full 4 seconds.

The resolution is to correct the toe, rear spring length and rate to previous values and return the shock and ARB rates to baseline while leaving the #600's up front. I also adjusted the wing to zero* angle of attack and put some sweet Brembos on it.

Having the front brakes on all the time couldn't be helping in the turns all that much either.
Did I mention the front brakes were dragging so hard that they wiped out a brand new set of Padgid RST 2's? Yup.

As of this moment the car is ready to go save the fact that I will be on the same tires that I tortured last time out pushing and sliding this 4000 pound pig around.

All I'm looking for at this point is a better balanced race car. The speed is in there.
Once I am satisfied with that I will put some stickers back on it and see what she'll do.

 

[Mad Hatter]

8” is the tallest spring that will fit with these wheels.


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True. I was going to 10's but stayed with the 8's for the 18x11's.....some day....

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[Fabman]

True. I was going to 10's but stayed with the 8's for the 18x11's.....some day....

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I believe the Vorshlag and Apex 11's and my 12's have about the same back spacing at around 8.1" We are in the same boat.

 

[Fabman]

Compare the static full bump (springs removed) and the on Track shot below.

 

[Fabman]

Suspension cam:

There are two different camera angles in this video.
Second angle is at about the minute mark.
You can see how much of the time the trailing arms are beyond the optimum angle, especially the right rear as most of the turns are to the left.

https://www.facebook.com/video.php?v=10155155104213535

 

[JAJ]

So I'm enjoying my second glass of wine on a balcony overlooking the Med in a little town called Monterosso in the Cinque Terre area of Italy. The weather is a pleasant 75 degrees and the evening sky is blue from horizon to horizon.

THAT was the best explanation I've ever read of how a suspension actually works. Sal, it was brilliant! So - how did the car run on the weekend? I'm dying to know!

 

[Fabman]

So I'm enjoying my second glass of wine on a balcony overlooking the Med in a little town called Monterosso in the Cinque Terre area of Italy. The weather is a pleasant 75 degrees and the evening sky is blue from horizon to horizon.

THAT was the best explanation I've ever read of how a suspension actually works. Sal, it was brilliant! So - how did the car run on the weekend? I'm dying to know!

Italy, the motherland! I'm so jelly.
Thank you for the compliment. I tend to ramble when I get on a roll and I'm not sure how people take it, or who follows my train of thought or think I'm a nut or whatever.
Probably some of each I suppose.
My next run isn't 'till the 28th with TMO/HOD. I have to run some pretty tore up tires, but that's okay. I need to know that we are making the right moves towards stability, then I will mount the stickers and give it a go. Stay tuned.

 

[Mad Hatter]

Suspension cam:

There are two different camera angles in this video.
Second angle is at about the minute mark.
You can see how much of the time the trailing arms are beyond the optimum angle, especially the right rear as most of the turns are to the left.

https://www.facebook.com/video.php?v=10155155104213535

Thats really cool to see. Is the huge wing you have forcing your butt down and altering your lca angle too much???

 

[Fabman]

Thats really cool to see. Is the huge wing you have forcing your butt down and altering your lca angle too much???

It's possible, that video was taken at a prior event so there was no wing involved.
I'll be watching everything very closely so lets see what happens next.

 

[Fabman]

Apparently tapatalk has truncated my explanation of changes and results. If anyone is interested in the whole post #685 you may have to use a desktop/laptop to view the entire schpeal. Tapatalk at least in my case starts at bullet point #8.


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[Fabman]

Like Father, Like Son and Like Daughter too.

 

[Fabman]

And... the hauler; My twin turbo F 150 Tremor.
It's All Ford/All The Time at the Molinare household.

I always taught my kids to "Put your money where your mouth is."
Nice to see some things managed to sink in.

 

[ArizonaBOSS]

I am going to have to come back and read that sermon later.

 

[ChrisM]

We have a 2013 F150 with the V8 and a 2016 Escape as well as my Mustang and many, many Ford Hot Wheels and models around the house, as well as a Ford Only parking sign, posters, a coffee mug, and I have a Ford Racing jacket that I wear religiously. These things just kind of appear.

I know how you feel.

 

[Fabman]

We have a 2013 F150 with the V8 and a 2016 Escape as well as my Mustang and many, many Ford Hot Wheels and models around the house, as well as a Ford Only parking sign, posters, a coffee mug, and I have a Ford Racing jacket that I wear religiously. These things just kind of appear.

I know how you feel.

Birds of a feather.

 

[Fabman]

I am going to have to come back and read that sermon later.

Here are the cliff notes:
"Blah blah blah-me me me....reiterate, speculate, postulate, aggravate and con-flate....got a few excuses, wild theories and projected gains."
You didn't miss much unless you'd care to delve into the minutia of my personal opinions and prospective goals. But what the hell, it might be entertaining over a few beers.