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anti squat percentage, IC height & distance-radial FOX Mustang

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652K views 959 replies 193 participants last post by  Mista Bone  
#1 ·
First, get ready for what may be one of the longest single posts in YB history. Sorry about that. :-D

I just learned little bit about anti squat on this thread: http://yellowbullet.com/forum/showthread.php?t=169353

However, I've decided to start a new one rather than hi-jack SLOCOUPE's thread any further. Thanks to SLOCOUPE for starting that thread and thanks for all the info so far from "feetfirst"

The problem: I've made 72 passes in the car over the last year and have not once have I made it down the track cleanly. To say I'm frustrated would be about the biggest understatement ever. Right now I don't think I could get a kid's "Big Wheel" to hook in a puddle of VHT
Image


That said, here's some of the specifics of the car: 25.5 93LX coupe, 94mm Precision turbo, G-trim, with a 1.0 A/R, 8 blade billet compressor wheel, 349 SBF, TFS R heads, super victor, 90mm TB, yada yada, FAST XFI fuel management (and I do have a driveshaft sensor and I do log DS rpm), MSD 7531, AMS-1000 boost controller. ProMod glide with 1.80 1st, Neal Chance bolt together converter (refined a coupe of times so far by Marty), Team Z/Strange 9 inch with a Moser aluminum 3rd member, 3.50 gears.

That's the basics of the power train, if other info is needed, please ask, I'm happy to provide it if it will help. I have been doing most of my testing on 325's (Hoosier's 1st, then M/T), but about a month ago I put a set of 275's on the car (M/T's) due to the recent popularity of 275 racing in my area. I run 10" alumastars with Sheppard bead locks. The car is 3300lbs with me in it (I'm 6'5" 250lbs).

Rear suspension:
Image

I currently have Wolfe lowers and UPR uppers with Afco Big Gun coil overs and Afco 12" 150lb springs in the rear with a Wolfe double anti roll bar (note: I mentioned in the other thread I thought the roll bar might have a binding problem, but I verified last night that it is now moving freely). I did my testing last fall with Afco 12" 125lb rear springs, and I still have them. I have no extra control arm mounting holes other than stock, so the only instant center adjustment I have is changing the ride height.

One of the problems I think I'm having is too much adjustability in the coil overs. I've never had a shock or coil over with more than 10 clicks of adjustment and these have 40 clicks on separation and 20 clicks on compression. I've started at 50/50 began loosening separation and tightening compression, but I honestly didn't know where to start.

Current front suspension: KONI SPA-1 struts with QA1 14" 175lb springs on stock V-8 Fox Mustang spindles. I have about 5" of separation from rest at the current ride height (camshaft centerline is 18.75" from the shop floor). I also have a set of Wolfe travel limiters, so I can tie the front end down if I need to. I have a set of 14" 125lb springs I haven't tried with the SPA-1 strut and OEM spindle set up, but I think with the iron R302 block the 125's are too light. I will buy a set of 14" 150's to try very soon. I have been told by several people including Gordon Benson who is the drag racing guru at KONI that the SPA-1 cannot be adjusted tight enough for my application, but as of yet I can't get it to hook well enough to find out.

I have also tried (and still have sitting on a shelf) this set up:
Image

AJE 2" drop front spindles with KONI yellow double adjustable inserts, and a set of Afco 14" 125lb springs. I didn't have but 1.75" of separation from rest with that set up, but I'm now thinking I gave up on it too soon. I now think that with the correct anti-squat percentage it would have worked.

If you watch the outlaw radial guys, NONE of them seem to have much front suspension separation. I know at one point there was an interview with John Kolivas in the NMRA Race Pages where he was quoted as saying after going to his 114mm turbo 427 cube Outlaw radial combo he had tied the front end down COMPLETELY to get the car to 60ft. Literally NO separation at all.

However, as I understand it (from Dave Morgan's "Door Slammers, the chassis book") it's take a TON of power (torque more specifically) to be able to get a car to transfer weight without the benefit of front suspension separation. John has well over 2000HP and I only have about 1300 (on a Mustang brand chassis dyno), so that may not work for me. I sure was hoping it would work because with that little suspension travel the car is a BREEZE to drive if it gets loose on the top end (which it always does if it see's anything over 20lbs of boost).

We have a set of Intercomp scales and I probably shouldn't have started this thread without the scaling info, but I'll get it today while I'm at the shop. I know the front to rear percentage has been roughly 52% front and 48% rear with me in it. I'm going out to move the batteries rearward today, hoping to get closer to 50/50. Here's where they are now:
Image

I'll be moving the kill switch to the right side of the ice chest and the batteries as far rearward as possible, but the new setup will allow me to move them to any of 3 positions quickly if I need to change at the track.

OK, after "War in Peace," back to the title of the thread. The "anti squat percentage" thing is new to me, but after searching this forum extensively I now believe it must be critical to making a higher power radial car work.

Last night I did some "quick and dirty" measuring and came up with some insane numbers. I'm guessing my haste in measuring is at least partially at fault, but got 7" for my upper control arm length, and 17 3/8" for my lower length. (note: I have pinion angle set at one degree down, and I measured the control arm length 90 degrees square to the axle tubes) On the Induction Motorsports calculator they have 7.5" for the upper and 18" for the lower when you open the page. Is that pretty standard for a Mustang?

Anyway, I entered my data and I got this:

IC Length: 36.167
IC Height: 9.5
Anti squat: 140.323

I'm pretty old school (I'm 46 years old) and most of what I've learned over the years is from Dave Morgan's book: "Door Slammer's, the chassis book." The contents of that book are directed toward cars with slicks and either leaf springs, ladder bars, or aftermarket 4 links. Apparently I'm going to have to "unlearn" a lot of what I've learned to get a stock suspension radial car to work.

If that calculator (and my measurements) are correct, thinking old school on slicks, my instant center is WAY too short for a car of this power. But on radials, IS it too short? At my current ride height on the rear suspension, my lowers are dead level, 9.5" off the shop floor front and rear.

OK, if you are all not asleep from all the reading, what do you need to know?? I hope for all your sakes nobody ever gets as lost as I am right now. HELP!!
 
#2 ·
This is great! We may all learn something from this.
I have a 89 coupe, 363ci, TEA 255 Hi Port's and just switched from a F1R to a F2.
All Team Z stuff Upper's, Lower's and anti roll bar. Strange coilover's with 120lb. spring's.
Ive been fighting suspension problem's all year so I may not have much to add to this
thread but Im sure I can learn something.
 
#3 ·
Those IC measurements could very well be correct.........seeing you have a 9", the upper ears are most likely higher than a stock 8.8 housing

What part of the run are you aborting? Or is it right from the launch?

The antisquat value is to high, and if you dont have enough shock travel, or shock control, it will be unloading...

Do you have any video of the launch? The car has to be violently separating the body from the tires with this setup?

It looks to me with your settings on the rear, you said you started 50/50, and started loosening extension...........was the wrong way;)
If you tighten extension, when the suspension tries to push the body upwards (140% AS), it in fact will drive the tires down to the ground.......which is what you need...
 
#6 ·
feetfirst said:
Those IC measurements could very well be correct.........seeing you have a 9", the upper ears are most likely higher than a stock 8.8 housing

What part of the run are you aborting? Or is it right from the launch?

The antisquat value is to high, and if you dont have enough shock travel, or shock control, it will be unloading...

Do you have any video of the launch? The car has to be violently separating the body from the tires with this setup?

It looks to me with your settings on the rear, you said you started 50/50, and started loosening extension...........was the wrong way;)
If you tighten extension, when the suspension tries to push the body upwards (140% AS), it in fact will drive the tires down to the ground.......which is what you need...
Click to expand...
I bought a Team Z/Strange housing because Dave Z says it has EXACTLY the same upper (and lower) control arm mounting points as the stock Fox Mustang 8.8. I'm heading out there in a few minutes to relocate the kill switch and the batteries. I'm going to scale it again when I'm done and sometime late tonight I'll post my accurate measurements and scale info.

As for the shock settings, I may not have used the correct terminology, but I started at 50/50 and what I loosened made the rear end seperate from the car more easily (i.e. allowing the rearend to move away from the body more easily, crushing the tires more easily). What I tightened keeps the rearend from returning upward toward the car as easily (i.e. transbrake release, or "hit" tries to push the rearend away from the body, I tightened the valving that prevents the coilover from colapsing together, there by keeping the load on the tire, or raising the body if the tire pushes back up on the car). I hope I explained that in a way that makes sense.

I have some video from last year and this year, but I'm not sure if I can post the stuff from this year because it is DVD format. I'll try.
 
#4 ·
i agree with that much antisquat,its going to need a really slow extension to control the rear axle.Im betting if you have video and could watch frame by frame you will see the tire distort violently just before the tire smoke starts.
 
#10 ·
No Racepak. Poor man's race pack LOL I used the analog sensor inputs on the FAST XFI. I look at DS rpm, fuel pressure, wastegate pressure, manifold pressure, (I even have redundant manifold pressure logging on the AUX channel in my AMS-1000 so I can compare wastegate pressure to actual manifold pressure, both from within the AMS), exhaust back pressure, crankcase vacuum, oil pressure, even coolant pressure (if you lift the head you'll see a spike). However, no shock sensors. I have inputs left, how I can I rig it up? lol
 
#11 ·
videos:

This was last December with Hoosier 325's on the car. I was playing with tire pressure and had as much as 17psi in them that day. I'd have to get out the log book to know how much on this pass, but I'd bet it was around 16.5 to 17psi. I think the launch rpm was around 4200rpm.

http://www.youtube.com/watch?v=wAMNHQzqu-E

different pass, but about the same set up, just a tad less tire pressure.

http://www.youtube.com/watch?v=DToibeJ4QlM&feature=related

This was one of the first times out with the car at Memphis, last November. All of the passes in 2008 were with 3.89 gears, which were too much. I put a 3.50 gear in the car this year.

http://www.youtube.com/watch?v=szXzG7LkngE&feature=related

This was the last time out in Memphis last December, still 3.89's and it would actually blow the tires off at 1200ft, and I can assure you it wasn't because of horsepower.

http://www.youtube.com/watch?v=uCTpWqVKUqU&feature=related

Here's one from first time out this year in June at Holly Springs. It had rained for 2 days, and rained till 9 that morning. It took till 12 to get the track ready to run. This outing was a waste, as the track was no good. I had it KILLED off the line just to try and get it moving and still spun and spun and spun.

http://www.youtube.com/watch?v=QP06XL-1xBQ&feature=channel

I'm working on getting some of the ones from this year posted, but as I said, they are DVD format, so I don't know if I'll be able to pull that off.
 
#12 ·
I have the same setup from Team Z minus the shocks type. I am having problems on the starting the most. Down track is fine. Your making more power but I think I am trying to leave harder. NA setup. High winding Small block. Going to due some measuring tonight to get this thing straightened out.

After you get all the measurements and calculate them what are you supposed to compare them too.

What kind of IC should we be looking for.
And should the AS be as close to 100% as possible.

Hope you get this figured out. I need some info too. Glad you started the thread. Maybe we will both be running good after this.

Dan Smith
 
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#13 ·
The DVD vids:

Here's just a couple. First, this one was earlier in the summer. I had changed from Afco 12" 125lb springs in the rear to Afco 12" 150lb springs and this was with the new 3.50 gears. I still had the AJE 2 inch drop spindles in the front at this time so I didn't have but 1.75" of upward suspension travel from rest, which you can pretty clearly see in the video. Testing that night was probably a waste due to all the humidity (not to mention street cars), which I will use as my excuse for the John Force burnout LOL.

http://www.youtube.com/watch?v=pISJ6oPycqY

This one was from August and I had swapped over to the KONI SPA-1 struts and stock V-8 Fox Mustang spindles. I had about 5" of upward suspension travel this time out. Didn't seem to me to help much at all. The track wasn't very good either, but I don't think the track was totally to blame for junky pass.

http://www.youtube.com/watch?v=UdyKSGgOpHU

Ok, that's it for me for the day guys. I'm headed to the shop to get some work done on this thing. I'll post up later tonight.
 
C
#15 ·
From looking at the videos and seeing other similar cars go fast

Ride hieght is to high especially in the rear. Good thing it doesn't hook becuase if it did It would go right on the bumper.

You don't have enough anti squat or the upper arm is setting the IC is in the wrong place in the car. The shocks are getting you off the line but down track the suspension really needs to put the tire into the ground and if it doesn't you not going anywhere.

You might wanna try more tire pressure. The issue is being compounded by not enough and having other adjustments being out of whack.

Shocks are primarly active for a brief time around luanch and after that only to control axle movement. If it was hooking down track but not at the launch I would go for shocks.

However being that its not hooking anywhere but the initial hit its steering the direction of diagnosys to suspension setup.

Pinion angle means dick in this chassis. As long as the housing can't push it through a zero condition during travel its not a issue. Having enough is important but its not a active portion of suspension dynamics unless the ujoint is in a bind condition. I'd check it across typical suspension travel.

Having had similar issue with a 9 second FOX I must ask

Have you checked the condition of the Upper and Lower Torque Box's ?
 
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#16 ·
The reason I ask about ride height is the front looks way up at rest. I'll tell you now I know jack about suspension. I too am having issues. You use the best stuff you can and your junk wont work. Then another guy throws some stuff on his car and hooks like mad. Very frustrating to say the least. Whats so frustrating is the numbers of these cars at the track and they all work different. I will post in my thread and yours my results after switching some things that were recommended to me by Team Z. My rear is sitting at 27inches now at race weight. S/S with a 28in tire. I am going to set the front level or as close as I can but no more than 1degree of rake. Dealing with a car that goes 5.56 to the 1/8@130mph with a dismal 60' of 1.36. I think it should 60' mid to high 20's and run 40's on the same setup when its sorted out. Good luck and I hope I am not Jacking your thread now.LOL
 
C
#19 ·
find out why you are loosing chassis seperation that you aboslutely must have in these radial tire cars for them to work. You don;t want them to "glue down" but you also don't want them shaking the tires.

A typical big tire car does not want or need alot of chassis reaction. He has a tire to do the work for him. A small tire guy Needs and must have a abundance of chassis reaction and then enough power to keep the tire from hooking to well. When it starts trying to stand up at 300 ft you know your close. Then you'll have to figure out how mch chassis reaction you need for the amount of tire and power you have to work with.
 
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#20 ·
Ok, I am on 28x10.5's with stk susp.. It is mini tubbed, with qa1 coilovers, 12" x 130lb springs in rear, baseline adj lowers and dbl adj uppers. Car works fairly well with 1.28 60's, on a sub par track. I have qa1 coilover struts, qa1 12" 150lb springs,and limited to about 1 1/2" of travel. Here are some videos from past races.

http://www.youtube.com/watch?v=aA--q88PrBg
 
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#25 ·
It would be way to hard to tell just by trying to compress the rear by pushing down on it.

You are losing bite after the hit.......car is not staying loaded on the rear.
Have you tried fully tightening the rear shocks?

Anyone that runs with shocks fully adjusted one way or another needs an IC adjustment...
 
#26 ·
Hey guys there is no such thing as hi jacking THIS thread. I want anybody and everbody who wants to learn or has somthing to offer to post up FREELY.

I would like nothing better than to see this thread be the how to bible for frustrated stock suspension radial Mustang guys. If you have info or want to ask questions about stock suspension radial Mustangs bring it here.
 
#27 ·
I have the shocks on 5, and they have 12 adjustments. Where do most usually run the struts? Also I have never scaled my car, or even done the measurments most are talking about. So maybe I should start there?

Thanks alot Scott!
 
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#29 ·
Best thing I ever did was lower the mounting point on the lower rear control arms. I had to weld brackets on but it was worth it. I think I dropped it 2" from original mounting hole on rear. 3280lb car 275s, strange shocks with 95lb springs. Before lowering it would usually spin off the hit and if it would hook then it would spin them at the top of 1st. I never have plotted mine out. I will get the numbers this weekend.
 
#31 ·
My day's work on the car today:
Image


and just for comparison, here's where they used to be.
Image


I'm hoping for a 1% or better change in weight distribution. It was too late to get into scaling the car tonight, but I'll be doing it tomorrow after work. I will also get the accurate measurements for the IC calculator.
 
#35 ·
Did you race this car before you put the turbo on it? If so what was the 60' before the power adder? Maybe you should turn the boost down until you can get it to hook then slowly turn the boost back up and watch how it reacts so you can make changes to it at a slower pace?

Tim
 
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#45 ·
Ever hear the old saying "I asked the guy what time it was and he explained to me how to build a watch"? Here goes. LOL

I bought the car as a roller with an 8.8 rear in it. The 25.5 was already done and the car had been run with a ProCharger (F1R I think). You can check out the Procharger install on the Bridge racing website: http://www.bridgeracing.com/don.htm

Then a year or maybe two later, the blown 331 was pulled in favor of a 398 cube Brodix Neal headed 106mm turbo'd MONSTER. The conversion was also done by Bridge Racing: http://www.bridgeracing.com/mustang_turbo_system.htm

That engine literally BROKE Wayne Young's dyno and the last thing it registered before the water brake broke on the dyno was 1998hp. The first time out with that combo, the manifold signal line to the wastegate found a header tube and the turbo over spun and the exhaust wheel came apart, destroying the turbo. Don Sphar quickly decided the cost of racing a car like that was more than he wanted to spend, and he sold the car to Dennis and Derrick Bailey of BB&T Racing. The engine in the car was from their Maroon 10.5W car (it had twins on it in the maroon car). The Bailey brothers put another turbo on it and made a total of about 7 or 8 passes with car. However they lost interest in the car when they ended up having Keith "skinny kid" Engling rebuild the maroon 10.5W chassis, and they built a 777 cube BBF with twin 106mm turbos on methanol in it. The original build of the maroon car and the rebuild of that car into the blue car is on Skinny's website.

That's when I bought the roller minus the all aluminum 398 and hot parts. I already had a complete 9 inch rear and front and rear suspension from another car I was building from scratch. The 33 spline axles in the 8.8 where twisted from the handful of passes behind the 2000+hp brute. Moser replaced them with 35 spline axles and I had to buy a new 35 spline spool in exchange for replacing the axles under warranty. I still have that complete rearend complete with the new axles and spool, T/A cover and dual caliper Aero Space brakes sitting in the shop floor waiting for me to sell it.

Anyway, no I haven't run the car with anything but a turbo LOL. There, I finally got around saying it LOL. With the 398 and 106mm it went 151mph with 325's on it, but I don't remember the ET. Dennis made a pass that is somewhat legend at Holy Springs where the car literally wheelie'd all the way down the track, almost on the bumper. As I found out when I bought it, it had a Davis Technologies wheelie box on it, and the Davis traction control box. I've never even powered up either of them. The wheelie box I've obviously had no use for (yet). As for the traction control box, I don't want to use it till I have the car at least working somewhat well.

The car used to work pretty well, but they really never got it sorted out. I changed all the suspension in the front and changed the rear ends, and added a Wolfe double anti roll bar. The car hasn't worked since. :-damnit
 
#36 ·
Whose 4-link calculator are you using? I was told by Performance Trends that Dave Morgan changed his IC suggested positions from his "Door Slammers, The Chassis Book".

Tim
 
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