Torque Arm and TA related Qs -- Stone, Eric, etc

[DevilSun]

Alright, have a few q's on one. Mostly, how important is the MM Torque Table do you think? My eventual goal for the car is the Total Performance Turbo kit for it if it doesn't get too hot running it at the track, which I'm sure it doesn't if built correctly. With that said, I think nathan was pulling somewhere around 450 #/lb torque maybe more.

- Do ya think the "HEAVY DUTY" kit is too heavy duty for an occasional street car, occasional track car?

- What spring rate would be good for use with the current Roush suspension...I don't even think we can get spring rates from Roush, so no idea where to start.

- Would it be better to install coilovers at the same time as getting a TA put on, and would there be any downfalls to putting on rear coilovers and the TA and not putting coilovers on the front?

- What is a good spring rate for my occasional street / occasional track car. I don't think it can ever be TOO rough for me.

Thanks, hope I made a decent point and didn't sound like a moron Lookin at jumping in the MM GP for install later, so would like to kinda see what you guys say / think.

[BULLITT208]

Originally posted by DevilSun
Alright, have a few q's on one. Mostly, how important is the MM Torque Table do you think? My eventual goal for the car is the Total Performance Turbo kit for it if it doesn't get too hot running it at the track, which I'm sure it doesn't if built correctly. With that said, I think nathan was pulling somewhere around 450 #/lb torque maybe more.

I'm not sure I would put a turbo on a mod motor track car. Turbo's generate a lot of heat and the mod motors already seemed to be stressed in this area. If you want that kind of power a centrifugal supercharger may be the choice. They don't generate as much underhood heat.

- Do ya think the "HEAVY DUTY" kit is too heavy duty for an occasional street car, occasional track car?

If by "HEAVY DUTY" kit you mean the HD T/A, the answer is no. The Heavy duty T/A is not to much for a street car. The difference is weight/strength. Peformance will be equivalant to the standard T/A, but the HD T/A adds additional structure to withstand more power.

- What spring rate would be good for use with the current Roush suspension...I don't even think we can get spring rates from Roush, so no idea where to start.

What do you mean by current Roush suspension? You are already running a P-hard bar aren't you, so your suspension in't really stock Roush anymore. How controlled is body roll at the moment?

- Would it be better to install coilovers at the same time as getting a TA put on, and would there be any downfalls to putting on rear coilovers and the TA and not putting coilovers on the front?

You don't have to install coil-overs. I would, but you don't have to. There are advantages and disadvatages to coil-overs.

Coil-overs typically offer more tuning flexibilty.
Using coil-overs you can maintain the same wheel rate, with a softer spring, so there might be a slight improvement in comfort.
Coil-overs also offer easier ride height adjustability.
Coil-overs put the springs in-line with the load paths so there is less bind.
If you go with a new k-member and lower control arms you will have to use coil-overs in the front/

One disadvantage is that there is more setup/maintenance with coil-overs.
It is possible, using the correct spring rate, to achieve similar performance to coil-overs with standard coil springs . A problem is finding quality springs that have the correct rate/heght combination.

- What is a good spring rate for my occasional street / occasional track car. I don't think it can ever be TOO rough for me.

The rear spring rate is dependent on whether you are running the T/A or not. The answer will be vastly different for Coil-overs or stock type springs. Once you decide the route you want to take the spring rate can be determined. The front springrate for coil-overs is typically between 350-425 lbs. With the 425 lb rate being more for a dedicated track car.

Thanks, hope I made a decent point and didn't sound like a moron Lookin at jumping in the MM GP for install later, so would like to kinda see what you guys say / think.

I would definately add the T/A to the P-hard bar you already have. It will remove the bind in the rear suspension and will give you a significant improvement in handling. Right now with the P-hard bar and stock Upper/Roush lower rear control arms you have competing roll centers. The P-hard bar's roll center is at the point where the bar crosses the centerline of the rear axle. The stock roll center is up near the trunklid. Right now they are competing with each and will cause bind beyond a certain roll angle. The T/A will eliminate this because it eliminates the upper control arms.

My suggestion would be to do coil-overs at all four-corners at the same time you do the T/A. That way when you decide to add a K-member you will already have the coil-overs.

Expect coil-overs to cost about $2K.


Eric

edited for clarity

[DevilSun]

Thank ya sir, lots for me to chew on

You say turbo creates more heat than centrifugal, understandable because it runs off exhaust. Is a power adder even really that good of an idea for a partial track car? Usually they just really trick them out N/A right because N/A is more reliable in the long run, plus probably some other reasons. If you were to recommend a route to go, would it be roots, centrifugal, or N/A?

Gotcha about HD reinforcement. As far as body roll on my car, it was helped tremendously with the PHB, but yeah, like you say, it feels very high on the car, and with a visualization of the axes you pointed out, it does feel about trunk height. The PHB did help out in removing a lot of the stock body roll, but the nose still dives pretty hard under slightly to heavy braking.

As far as more maintenance on the coil-overs, how so? Just more of a watchful eye on them or what?

Thanks for the input, enjoy having a knowledgeable place to come to and ask questions and not get flamed for it, or what not

[fishman]

Hey y'all...thanks for the stimulation. The analytical/technical side of my brain is being stirred...kinda refreshing for a change. Just wish I had some $ to participate. For now I'll just have to live vicariously, but it's nice to see some true tech discussion for a change.

~fish~

[BULLITT208]

Thank ya sir, lots for me to chew on

You say turbo creates more heat than centrifugal, understandable because it runs off exhaust. Is a power adder even really that good of an idea for a partial track car? Usually they just really trick them out N/A right because N/A is more reliable in the long run, plus probably some other reasons. If you were to recommend a route to go, would it be roots, centrifugal, or N/A?

Obviously, all other things being equal like maintenance, driving style, etc. an N/A motor will last longer than a motor with a power-adder under extended stress. I would shy away from turbo's for open-track use. I just think there is no way to avoid the heat and the other problems it will cause. With that said there are several people who run their track cars with power-adders. Stan runs a blower in his car. I know a guy Mark Who runs a Vortech in his '99 Cobra track car. Neither of them has had motor failures that I'm aware of. Then there is Kev, who blew his first supercharged motor at the track and has had no problems with the S3. So it can be done, but it can also go bad real quick. A well tuned and well maintained supercharged track motor should last for several years, but that involves a lot more time and money than just slapping on a supercharger and driving away.

My suggestion would be if you are serious about the open track stuff spend your money on you first. Go to a driving school and learn how to drive a car to it's limits, at the limits. The money you invest in yourself will be transferrable to any vehicle, not just your current one. If you are just starting out open-tracking there is no way you will be able to maximize the potential of your car as it sits. Your car has enough power rght now to get you into trouble real quick. (You will see this Thursday at Thunderhill.)

Also you've started down the path of improving the suspension. I would finish doing that first. Then decide if you need to add power. (I think you're covered for brakes. ) Driving the car on the track will really point out it's weaknesses and give you an area to focus on improving.

Gotcha about HD reinforcement. As far as body roll on my car, it was helped tremendously with the PHB, but yeah, like you say, it feels very high on the car, and with a visualization of the axes you pointed out, it does feel about trunk height. The PHB did help out in removing a lot of the stock body roll, but the nose still dives pretty hard under slightly to heavy braking.

The P-hard bar lowered your roll center so the axis around which the car rolls is much lower. The problem now is the bind point caused by the two different roll axes. Once the rear binds up you will experience snap oversteer. The spring rate essentially infinite at the point of bind and the car becomes unbalanced. The T/A will remove this and the T/A wil help with the rear end jacking under braking. Our cars nose dive some, but the bigger problem is that the rear jacks up under braking. The T/A will reduce this significantly.

As far as more maintenance on the coil-overs, how so? Just more of a watchful eye on them or what?

After the intial setup it's basically more of a watchful eye. The initial setup if done correctly is labor/time/money intensive. (I'm referring to corner weighting mostly and bumpsteer if you get a bumpsteer kit.) When you use coil-overs all of the weight of the front of the vehicle will be supported on the strut towers and C/C plates. Tis will require inspection of the strut tower and C/C plates from time to time to make sure there is no bending/cracking. (M/M four bolt plates go a long way towards eliminating this.) You also need to periodically inspect the lower springs seats to see if they've moved. If they move your ride height/corner weighting will be thrown off. It's not that big of a deal just not as much of an install and forget proposition.

Thanks for the input, enjoy having a knowledgeable place to come to and ask questions and not get flamed for it, or what not

No problem. I think you know where to go and lurk if you need more in depth technical information.

Eric

[Stone]

I shall jump in here and pretty much concur with Eric. When you decide you need to upgrade the parts, I would suggest getting quality/heavy duty parts. Not having to worry about parts breaking will help you explore the new limits of each step you take in improving your car. I find a lot of satisfaction in making improvements in driving, more from handling and skill improvement than just adding power to go faster in the straights. The key to getting around a road course in less time is more about maintaining the speed through the corners.

I will not plug any one brand because there are a lot of good quality parts out there. I myself have chosen mostly Griggs with a few Max Motorsports parts sprinkled in. I am now at the point where the car is potentialy faster than I am. I feel i can use this car in its current state for quite some time before I reach its limits.

I like to think of it like golf...You can give Tiger Woods and I the same set of clubs to play with, send us out to play 18 and I will guarantee that the results will not be the same.





Stan