Experimenting with the Dark Side

[shomesomesho]

Took the Mustang out Memorial day weekend for 2 days of autocross hog heaven.

This was my first time out with the Pony car, so I didn’t expect to do that well. I just wanted to see what it was capable of and what to expect.

I thought this beast wouldn't be course-ready for at least 6 more months. But these things are so easy to work on (compared to the SHO), and the weather is getting so good around here, I just couldn't wait.

They say the Fox body Mustang is a poor platform for autocross. Something about the solid axle rear end / lack of IRS, primitive suspension geometry, blah, blah blah. Of course, they said the SHO isn’t an autocross car either. What do “they” know?

Right now the Mustang has the stock 5.0 (with exhaust/headers & cold-air intake, estimate 240 HP/300 TQ flywheel, even less at the wheels), but suspension has been reworked.

It has coilovers (450/350), adjustable Koni’s, full-length SFC’s, strut tower brace, K-member brace, CC-plates, tubular front/rear control arms, Panhard bar & torque arm, running on 275-40 Hoosier A6’s with 17x9's. The rear has steeper 3.73 gears and a Detroit True-Trac torque-biasing differential (similar to the Quaife). Add in some racing seats and harness for better body control – for the driver, that is.

The car was actually pretty sweet and surprised me. The 6” shorter wheelbase is nice. The better weight distribution is nice. RWD is nice. (The torque arm and panhard bar really plant the live axle rear end and help prevent the tail-happy behavior under throttle these Mustangs are notorious for.) Real V8 torque is nice. Real traction off the line is nice, too. And the Mustang aftermarket is very nice.

The practice session I got the 3rd fastest time, just 1 second behind a highly modified/prepared Porsche 914 trailer queen.

The next day during competition runs I was ~ 1.5 seconds slower than the Z06’s (driven by National Championship-caliber drivers on R compounds).

Right now, in my estimation (with me driving) the Mustang is about as fast as my autocross SHO, +/- 0.5 second or so. Considering I can’t drive RWD worth d!ck (yet) and that the car is still under construction awaiting more upgrades, I’d say that’s not too shabby. It definitely has more in it.

More seat time is on they way, too. Man, I can't wait.

Immediate plans are for a 6 pt. roll bar and heads/cam/intake to bring it to 300 wheel HP/350 wheel TQ. Weight goal is 2,700 lbs. which is the minimum for under 5.1L V8’s in C Prepared. (I had been considering a balls-out 5.8, but the minimum weight for that would be 3,000 lbs. Hmmm.)

Eventual plans are for a paint job – Brittany Blue.

BTW, did you know the C Prepared SCCA National Champion over the last 2 years did it in a Fox body Mustang (under 5.1L)?

 

[93rev2sev]

You got MAF or Speed Density?

 

[shomesomesho]

MAF. It's an '87 that was converted.

I took the twEECer off the SHO to use it on the Stang.

 

[AutoSHO]

RWD is definitely more fun.

I wish we had some CP cars here locally. They look like a blast. We get 150-200 drivers per event but they're concentrated in ST* and SM, mainly.

 

[Shoaz]

RWD is definitely more fun.

Not in the rain.

 

[greenbeanmtx]

Saweeeeet! That car will look great with the brittany blue! I am a sales rep for 50resto.com so feel free to bug me for parts on that sucker anytime -Karson

 

[shomesomesho]

Saweeeeet! That car will look great with the brittany blue! I am a sales rep for 50resto.com so feel free to bug me for parts on that sucker anytime -Karson

Thanks.. got any discount codes?

 

[JoesSHO]

Great- I ditch the Fox, and now I know someone at 5.0 Resto. Great.

 

[greenbeanmtx]

Thanks.. got any discount codes?

Haha, I knew that was coming.

In all seriousness though, I have seen many notchbacks that are out of this world road race cars. You can make a notchback do some amazing things with the parts available. If I could find a clean one for an affordable price, it would be sitting in my garage. That is one car I have still yet to own and really really want to at some point. The sad thing though is that a clean notchback goes for the same price that a vette of similar age goes for. Heck, even 4 banger v8 conversion cars are going for strong money now if the conversion is done right.

 

[GeneSHO]

Nice new ride Fred. Keep the updates on the Stango flowing

 

[n8rsk8r]

Saweeeeet! That car will look great with the brittany blue! I am a sales rep for 50resto.com so feel free to bug me for parts on that sucker anytime -Karson

They have been given ALOT of my money through the years! I used to deal with Mike Briscoe... what is it with you guys and your corvettes? LOL

Notches are the best though! You guys see any quarter panels being reproduced anytime soon? I need one BAD for my 91 notch.

BTW GREAT LOOKING CAR MAN, Just need that paintjob and it will be secks all night long!! :drool:

 

[zak]

How does CP PAX against the Z06's (SS ?)

The problem with the Fox is you need to do so much to it to get it to drive right, Panhard or Watts link, torque arm, mess with the front geometry or tubular X-member, etc. etc. Trust me, I've had a fox for the last couple of decades . . . greenbeanmtx, I need one of those timing covers you sell that's a hybrid between the standard 86-93 car yet has the mounts for the electronic crank sensor on the later cars . . . zak

 

[shomesomesho]

How does CP PAX against the Z06's (SS ?)

It's fairly close:

SS 0.852
CP 0.864

The problem with the Fox is you need to do so much to it to get it to drive right, Panhard or Watts link, torque arm, mess with the front geometry or tubular X-member, etc. etc. Trust me, I've had a fox for the last couple of decades . . . zak

Strongly agreed. But doing the work to get it up to par is half the fun for me.

When I first got it, this Fox was virtually undrivable from a performance perspective except in a straight line. "Numb" falls short of adequately describing it.

Even with all the mods so far, it's still a fairly difficult car to drive. The unibody flex, even with SFC's, is still pretty significant, making the car slow to respond. Slaloms are especially painful. While the car is no longer "numb", it's still quite sluggish compared to my SHO.

The mostly stock 5.0 motor has great low end, but midrange and top end seem impotent compared to the venerable 3.2L Yamaha.

The Fox definitely needs more work (H/C/I, roll cage or bar, tubular K-member).

FWIW, I took the SHO out autocrossing yesterday just for comparison. It was so incredibly refreshing to drive and was actually within 1 sec of the fastest Z06. I think I may have caught one of the slower ones.

As it stands right now, the SHO is definitely faster than the Fox, but the Fox ain't done yet.

(The SHO has SFC's, but lacks a cage. It still suffers from significant chassis flex, but not nearly as bad as the Fox. I'd bet that if I put a cage in the SHO, it would net 1 sec faster times.)

 

[SeanMc]

Watts>Panhard. It's the best thing you can do for the wagon wheel rear end in the Fox.

 

[shomesomesho]

A fellow autoxer took pics of the last event.

Look at how much roll there is w/ the Mustang. Damn. . . no wonder it's such a slug.



This is with 450 front and 350 rear coilovers, Hypercoil brand (and no sway bars). I think it's time for stiffer springs.

I think I'll go with Eibach brand coilovers. That's what I'm using on the SHO.

 

[Shoaz]

This is with 450 front and 350 rear coilovers, Hypercoil brand (and no sway bars). I think it's time for stiffer springs.

Or some bars if you want to drive it on the street. Controlling roll strictly with the springs usually means that the springs will be so stiff that driving it on the street will be very risky. Any little pothole may essentially remove a corner from the car.

Anti-roll bars aren't a bad thing to use to get the best compromises, and it looks like some reasonable bars might help that car a lot without having to get too crazy with the springs.

 

[AutoSHO]

I agree - A front swaybar is almost always good for a RWD autocross setup.

The Mustang isn't McPherson up front, is it? Been a while since I poked my head under the front of one.

450/350 is pretty soft overall, especially once you calculate the wheel rate. I'm running 625F/500R on my car, and the street ride is acceptable. I also run a 28mm swaybar up front, and the stock rear bar... But IRS is a little different to tune (obviously). I would imagine you want to stay away from a rear swaybar with your car, as all it will do is unload the inside rear tire. A front bar will make the car much more responsive through transitions, and in all likelihood improve front grip in all conditions by keeping the suspension in a better part of its camber curve.

If you're not planning on doing much street driving, and plan to continue to run R-comps (or stickier) for track/autocross, I would bump the spring rates up by a good bit. Softer in the back is great for a RWD car as long as you can get the front to bite (should be easy with no rear camber). You might get a set of 550-600 for the front, and move the 450's to the rear as a starting point.

 

[shomesomesho]

Appreciate the comments.

The Stang is not street driven so I am not worried too much about ride quality. I just want it to handle.

The front isn't McPherson. It's Primitive. In the stock configuration there is a big fat coil spring that sits inboard of the shock absorber. When you switch to coilovers, that fat coil spring is removed.

I would prefer to tune with springs. I'm hesitant to use swaybars - the front SB is a big chunk of metal that weighs about 40-45 lbs. and the rear is not light either. If I could find a smaller front SB I might do it. Some aftermarket vendor out there probably makes one.

Also with the current configuration, this car understeers worse than the SHO, believe it or not (it's also nose-heavy) . . . another reason to avoid a front SB.

I may go with 600/500 . . . they say for the Stang the rear should be about 100 lb/in less than the front. Koni's for the stang have much stronger dampening than those for the SHO, so they should be able to handle the stiffer rates.

Now that I look closer at the picture, it seems like the front is rolling more than the rear. (Cover the front half of the car with your hand, then cover the rear half and compare.) D@mn, that's some serious unibody flex, LOL! It definitely needs a cage.

 

[AutoSHO]

In some cases, the front swaybar will actually add front grip by keeping the suspension in a better part of its camber curve - That's how most McPherson strut cars end up. They also end up with 3 wheels on the ground some of the time, but it seems to work.

40-45 lbs of swaybar is a lot. I thought my 28mm bar was bad, and it's maybe 20 lbs. I agree, most of the tuning should be done with springs, but in order to get the car working really well you'll have to go way stiff (and probably have the konis revalved) if you want to get the roll under control. That - and eliminate some of the chassis flex, as you've noted!

 

[shomesomesho]

An update. . .

Since my last post the Mustang has undergone some changes:

- addition of 6 point roll bar (more to stiffen the unibody than anything)
- 650/550 f/r coilovers (from 450/350)
- H/C/I swaps to bring it to approx. 310 rwhp / 350 rwtq
- Tubular K-member to improve front end geometry (allowing more caster and a better camber curve)
- The rear remains straight axle with Torque Arm and Panhard bar.
- Weight right now is ~2,750 lbs. without driver
- aftermarket front roll bar that is lighter, less stiff than stock unit
- retained stock rear sway bar

The car now cornered much more flat and had tons more power, at least with casual driving at legal speeds. The unibody felt pretty solid and responsive, unlike before.

I was feeling pretty good about it.

Took it out for autocross July 7 and lo and behold, finished 69th out of a field of 107. At race-level driving, the Mustang was uncontrollable. No rear traction at all. Snap oversteer at anything past 1/2 throttle. It was embarassing. It looked like a drift car on an autocross course. And this was on Hoosier R compounds. Couldn't even keep up with the Hondas on street tires.

I was ready to throw this hunk of metal off a cliff.

Well, back to the drawing board. . .

The big problem is this - you can't get any action without traction.

So how could I maximize rear tire traction on this beast?

Go back to the basics-

- wider rear tires
- soften the rear end
- widen the rear track

So, I went to 295's on 10" wide rims (previously 275's on 9").
Kept the 275's in front.
Removed the rear swaybar.
Installed rear axles that are 3/4" wider per side.

Now with the staggered setup it looks like a freakin' drag car.

Took it to autocross July 20th.

The Mustang was freakin' SOLID. The rear actually STUCK to the ground. It handled the course like a freakin' hummingbird on crack cocaine. I was going through slaloms and sweepers at FULL THROTTLE.

I couldn't believe it! I was completely shocked!

I was so dumbfounded by this I kept missing the same gate my first 3 runs (of 4). Kept going outside the cone instead of inside.

My 4th and final run was actually clean, but I blew the 2nd-->3rd gear shift - fumbled the shifter for about 2-3 seconds until it finally clicked into 3rd, but still managed to get a 51.6 which was 9th fastest (of 152) overall raw time of the day.

Results posted here.

That blown shift probably cost me over 1 sec. The stock shifter on the T-5 is a WORTHLESS PIECE OF **** - it is going to get upgraded right away.

We had fun runs afterward, and I consistently ran in the 49's (49.2 to 49.8). If I had done that during my official runs it would have put me at 2nd to 3rd fastest overall raw time of the day, right there with the ASP Viper!

Next meet coming this weekend and I absolutely cannot wait. The 295's are going in front, and the rear will get 315's.. . . the paint job can wait a little longer. . .

Footnotes:

- tried it without the front sway bar connected and the car acted ******** in the slaloms. The Mustang definitely needs that front sway bar in place.

- I can say with complete confidence now the Mustang is definitely faster than the SHO in autocross, but the margin isn't by that much. Probably ~1 sec on a 50 sec course. Regardless, the SHO is still pretty fast.

- RWD is definitely more fun than FWD. Sorry. It's nice to actually be able to launch HARD off the line and steer by pushing on the throttle.

- I'm gonna hold off on that IRS swap for now.

- Couldn't make the Convention - couldn't get time off work. Now if it was on a weekend, it would have been a different story. . .