Weight Transfer

[sfm92Vert]

What is the significance of "weight transfer" while leaving the line in a race? Is it better traction which results in better ET's? In other words, if a mustang already has adequate traction, will the use of drag springs, control arms, drag struts, etc equate to faster and more consistent ET's?

[I have a 92 LX Convertible which is primarily stock. With 373 gears, 15x10 M/T ET Drags(21lbs of air) and an automatic transmission. 60ft times range between 2.064 - 2.088. ET's vary from 15.37 - 15.44 The car is not launched very hard: 1000 -2000rpm. (still experimenting while trying to concentrate on the tree)]

I am starting my 1st racing season in a sportsman bracket racing class(11.99 and slower) this weekend and are looking to be as consistent as possible.

Thank you in advance for you help!!!

Weight transfer basically means shifting the weight balance of the car upon launch to the rear wheels. When the car's setting on the ground on all four wheels, you may have something like a 55/45 split of that weight front to rear. If you launch and pull the front wheels up, that split has now gone to 0/100. Planting that weight on the rear wheels means added normal force in the contact patch which equates to a higher frictional force in the contact patch => more bite to prevent spinning of the wheels. Well matched suspension components enhance and control this weight transfer. A good combination of springs, struts, control arms, pinion angle, etc. will maximize not only the weight transfer, but the control of the car when it happens.

With your combination, I don't think there's much chance of you overpowering those 10" slicks. Take your launch RPM up to about 5000 and dump the clutch. But be forewarned, if you're still on stock axles you're just asking for trouble. They may go 200 passes or 20 passes. Do yourself a favor and invest in some Moser axles.

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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm

[sfm92Vert]

Thanks Jeff for the advice. Congratulations on a great season by the way. I see your name all over the place.

My car is an automatic so dumping the clutch is not an option. What would be the best launching technique for consistent ET's and good reaction times w/an automatic?

Do you know of any racers who drop their convertibles for a more balanced weight transfer? (I haven't tried it... Not sure what the NHRA rules are having the top up or down.)

LOL, no I do not have any problems with spinning the tires. The M/Ts are a little overkill right now, but they have been a great investment. Not only have 60' times improved, but also I can keep up with cars which a full second quicker to almost half track until my car fades away. More mods are on the way. I guess for now my focus should be on making the car faster and not worry about chassis and suspension for the time being.

I'm not sure what the stock stall is, but I'd imagine that its probably around 2000rpm. Have you considered or already installed a higher stall converter? Some of the AODE guys may be able to help here, but I think something in the range of 2800rpm would really help get you out of the hole. Foot brake it until your right on the stall then let loose on that last amber. Your convertible is probably in the 3500# range (?) so your roll out it a little longer than with a lighter car. Try to be consistent with how far you stage into the box. Put yourself there time after time so that you can work on timing the rollout.

I'm not sure, but I don't think the track will let you go with the top down. I could be wrong about this though. But to enhance that weight transfer, get everything you can off the front end. Undo or remove the front sway bar. Go with skinnies up front if you have the money. Loose the hood blanket plus any accessories you're not too fond of.

Work both! If you concentrate solely on the HP, then you won't be able to get it too the ground. Work both at the same time and bring the combination to form together. You'll be much more satisfied with the car and investments.


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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm

[sfm92Vert]

Yes, the 1st area I upgraded was the transmission. Part of that upgrade was a 3000 stall converter. It seems to stall less than 3000 though while foot-braking although I'm still experimenting. I will try your advise on staging & launching tomorrow during test & tune as my reaction times have been all over the place.

By the way, the car weighs 3620lbs with driver.

Holy cow! Time for that baby to start the slimfast diet. Seriously though, look for little bits of weight anywhere you can find them. Loose the spare & jack, run with minimum fuel, leave the CDs at home. You could also try to find a lighter battery. I've seen guys loose as much as 20# going to a smaller battery.

With a 3000 stall, you should be able to foot brake it pretty well. Like I said, pay attention to how far your staging up. Try to get there every time. I also learned a whole lot by standing right at the starting line and watching car after car leave the line. Pay attention to that last bulb and when you see them start to move. If you're racing at night, you may have to adjust your rhythm a little since the bulb brightness will appear earlier. Just stand at the fence and visualize when you'd leave and compare that to the cars leaving. Sounds a little silly, but it really helped me get a grasp on the tree.



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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm

[88workcar]

You can also try flashing the converter. Let the car idle till your ready to leave and just floor it, this causes a sling-shot affect on the converter. Try it, it works for some people.

[sfm92Vert]

Thanks Jeff! Your advise for the tree is starting to pay off. At test & tune last night we were able to make 3 runs. My reaction times are as follows:
.505 = )
.393
.489
(My previous 3 runs a week earlier were .905, .567, .623.)

The .393 time I felt myself anticipating the light and was able to make the adjustment on the last run. Although the 3rd reaction felt exactly like the 1st it resulted in a red light(?) The car was shallow staged each time and was launched at the 1st flash of the last yellow.

Friday I will try to pre-stage while just barely lighting the tree and see what kind of difference this will make.

Originally posted by sfm92Vert:

I guess for now my focus should be on making the car faster and not worry about chassis and suspension for the time being.

Actually you should try on doing just the opposite. Get that suspension stiffened up with stiffer control arms and get subframe connectors and mabye even a roll bar. This is how trophy stock guys go so fast with a minimum of HP. The first 60' is the most crucial part of the run and optimizing for the fastest 60' will result in the best run. Of course, doing this may sacrifice streetability(4.30s may give the hardest launch but most people would'nt run them on the street).

You might want to try airing your slicks down to 10-12 psi; this is the pressure range I use except I have 26x10 M/T ET Streets. But I don't have any problem with spinning; I usually launch around 5000 rpm. It's too bad you have the AOD but at least you got a good stall converter.

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88 GT, full exhaust, edelbrock intake, accel, pullies, k&n, drag springs, subfranes
13.12/102/1.80 at Byron Raceway

[This message has been edited by fiveoboy01 (edited 01-20-2000).]

[93yelLE]

Is your car your daily driver? If so, I've found it difficult to cut weight w/ conv's and maintain the comfort level. I agree w/ fiveoboy that chassis tuning is worth it, but disagree on the tire pressure. My recommendation would be to run the highest pressure you can w/o spinning. This allows the smallest surface area of tire to be touching (dragging, slowing you down) the ground. Also, a set of skinnies w/ 50 psi was worth as much as 3 tenths over my ponies and 245/50's for my car (on radials).
As far as I know, most tracks will not let you race w/ the top down (it really doesn't make much difference in traction anyway), but I asked just for kicks and they said they'd let me run if I had a 10-pt. Guess that won't be happening!!

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93 yellow limited edition convertible
Black top/interior, 5-spd
3.73's, H-pipe, pullies
Best - 14.13 @ 96.5 on street tires
3650 lbs w/ me.
My desperate attempt to get some pics up - http://cperryman.tripod.com/grid1.html

[T/S # 25]

I would be using at leats 4.10's but more likely 4.30's. I would change out the stall converter for something that stalls a little higher. As you start to make more horsepower and torque, the stall converter you have will stall up a little higher. A trans-brake will help out in that department also. I would still bring the stall up at leats another 500 rpm's though. Just my 2 cents.


JOE
T/S # 7
12.80 @ 107.89

I agree with 93yelLE, on the tire pressure issue; I should've clarified that you should drop the tire pressure IF you're spinning out of the hole. But if you're not spinning leave it up; less rolling resistance is better. With a 5-spd you HAVE to drop the pressure so the sidewalls will wrinkle, otherwise you'll shock the tires too hard and they might spin. Too low of pressure, and the rim might hit the pavement and the tire would unload as the rim springs up. But your combination is mild so it's not really a concern especially with 10-inch wide slicks plus the fact that an AOD is'nt going to shock the tires as much during the launch.

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88 GT, full exhaust, edelbrock intake, accel, pullies, k&n, drag springs, subfranes
13.12/102/1.80 at Byron Raceway

[sfm92Vert]

Yes, for now this car is a daily driver, so I cannot see running a higher than a 3.73 gear at this point. When I first bought the slicks I started at the (M/T)recommended 16lbs and increased the pressure 1lb on each run. The tires held to about 22lbs so I backed off a pound and have been running @ 21lbs since. This weekend we had a cold front come through and was loosing traction, so Saturday I ran at 20lbs. A friend of mine was behind me while I was doing a burnout a said my driver side tire did not spin during the burnout! This may have contributed to the lose in traction as well. Should one tire not spinning be a concern?????

93yelLE, I haven't checked with our track about running with the top down, but it is definitely not worth it if you need a 10pt. cage! It just sounds like a good idea being able to put the weight of the entire roof over the rear axle. Our heavier cars should get some advantage out of it ; )

As far as future mods, I am going to take Jeff's advise and work on both speed and suspension. My next mods are going to be sub frame connectors, a strut tower brace and exhaust. Everyone says Kenny Brown's subs are the best, but I am also looking at Maximum Motor Sports(?) unit. They advertise that it is longer and extends from the firewall and the way to the torque boxes and is a good foundation for roll bars. They have a 6pt roll bar with swing out (and removable) door pieces. Has anyone had an experience with this company? They advertise all the time in MMFF.

[T/S # 25]

The Kenny Brown sub-frames look like pieces of lawn furniture. You wouldn't dare find those on my car. If you want a set of sub-frames that work give me a call at IDLE Wild Racing, (727)507-9453, and we'll sell you a set better and cheaper than the Kenny Browns. I don't see too much benifit from the strut tower brace accept adding more weight that you are trying to get rid of in the first place. One tire spinning means that it's time to rebuil the Trak-lock in the rear end. You could also add some 90-10's up front and remove your front sway bar to help weight transfer. I woul also try lowering your tire pressure a little more. I usually don't run mine any more than 14lbs. Just some info that might help you out.


JOE
T/S # 7
12.80 @ 107.89

[T/S # 25]

Also with the exhaust, don't go to big. If you do you will loose some of your low-end torque and that is exactly what you don't want to do taking into consideration the few mods that you have done and the weight of your car.


JOE
T/S # 7
12.80 @ 107.89

[sfm92Vert]

Joe, thank you for the advise! I will save the hundred bucks on the strut tower brace. Do you have a web site where I can check out the sub frames?

I would love to put drag springs on all four corners. My concern is what will removing the front sway bar and 90/10 springs do to street drivability. Will the car be safe and how will the car handle?

As far as exhaust, I am currently looking at a set of BBK ceramic coated long tube headers and matching H-pipe w/converters. I have chosen these tubes with the expectation of increased torque. The only thing holding me up is the installation. I want to do the install myself but have heard different stories of having to jack up the engine etc. to get them in.

I have very little knowledge of suspension and chassis work, but even less when it comes to the rear axle assembly. What trak-lock (parts) should I get? What else should I upgrade (axles,etc.) in the rear end as long as the car will be in the shop?

I owe you guy's big time! This by far is the best Mustang site! Thank you all again for your help! (I can't wait to start helping others with the knowledge that I am learning!!!)

[T/S # 25]

Hey sfn92Vert, E-Mail me at JOE50RACIN and I'll answer as many questions as I can. We do have a Web Site " www.IdleWildRacing.com ". Check it out. I don't think there is a picture of the sub-frames on it, but just give us a call and I'll help you out with them.


JOE
T/S # 7
12.80 @ 107.89