JakeRobb

Okay, so I'm interested in getting a supercharger (maybe turbo -- undecided here) for my Z28. I posted a topic in the Forced Induction forum asking some questions.

Later, I got a PM from Eric at Victory Racing, who filled me in with lots of info. Here's a snippet of his message:

I've heard of all of those parts he said I should add, but I want to know more about them. Searching the internet and these forums tends to produce results like "I got my new SFCs" and "With that much power, you'll want to upgrade your panhard rod" and never anything that actually talks about the benefits to be had from the parts in question.

So, for each of the parts Eric mentioned, I want to know the following:

1. What is it?
2. Where does it get installed? (location on the car)
3. How does it get installed? Bolt-on? Welding? If there are options for different installation types, what are the pros and cons for the options and what should I take into account when selecting one over the other?
4. What affect does it have?
5. What might happen if I had too much power and had not performed this upgrade?
6. Does the car already have this component, and I'm just putting in a stronger one?
7. Am I sacrificing anything by installing this part? My Z28 is my daily driver, so I don't want to do things that are going to have a large negative affect on drivability, ride quality, or handling.

Eric gave me the impression that these are mods one would do to help a high-horsepower car get that power to the ground, but I'm looking for more specific information.

Oh yeah -- these are down-the-road plans. A couple years at least. I just like to plan ahead!

Thanks!

-Jake

P.S. I know I'm asking for a lot of information... if I get good answers, maybe this thread could be made a Sticky?

Injuneer

That's a lot of info you're asking for.... but I'll give you the short version.

Subframe Connectors

Subframe connectors "connect" the front and rear "subframes". The subframes are the strudy "box" section members that the front and rear suspensions attach to. Since the F-Body is a unit body car, there is no continuous frame extending from the front to the rear of the car. So, the entire body is the structural member, leaving it open to "bending" in torsion.

By adding a square or round tubular member to each side of the chassis, either welded (preferred) or bolted to the front and rear subframes, you increase the torsional rigidity of the body. The energy that used to go into "twisting" the body is now avaialable to be put to the ground by the rear wheels. And, your handling is more consistant.

This mod can not hurt your car. Its good for a "stock" power level car, and essential for very high HP setups.

Lower Control Arms:

Connect the rear subframe on each side to the rear axle assembly. In essence, this is the piece that locates the axle under the car in the front-to-back direction. It is the member that transfers the "thrust" of the rear wheels to the body, and makes the car accelerate. And it transfers the braking force to the body to slow it down.

The LCA is pivoted on each end, to allow the body to rise and fall relative to the axle. It has soft rubber bushings, that have very little vertical resistance. Hence, the LCA will not be well located undet heavy loads. And the stock LCA is made out of a "U" shaped piece of stamped sheet metal, so it could bend under heavy compression loading.

The upgrade LCA is either a rectangular or tubular bar that exhibits additional strength to resist bending, and uses an upgraded bushing or "rod end" to attach to the body and the axle. Its totally a "bolted" piece, never welded. The selection of bushings will depend on how you plan to use the car.... firm polyurethane works fine for drag cars seeking straight line traction, but may provide "suspension bind" when the body rolls during heavy cornering, so you wouldn't use poly on an Auto-X car. The rod ends are spherical metal bearings, and they are good for both applications (drag and cornering), but are generally very harsh and noisey, and have a limited life.

AN LCA is a good upgrade at any power level. There is no down side to putting them on a stock car, as long as you select the correct "ends".

Torque arm:

Now we have the axle pushing the car forward by the two LCA's, which can pivot. As the torque load passed through the differential increases, the front of the differential wants to rise, in reaction to the torque load at the tires. The torque arm is a long "lever" that bolts to the differential housing, and runs forward to the middle of the car. On a 4th Gen, its connected to the tailshaft of the tranny, and mounted in a soft bushing that helps eliminate harshness, and also allows the torque arm to slide forward or backward in response to the arc defined by the pivoting LCA's. That helps prevent another form of suspension bind.

The stock torque arm is made out of stamped sheet metal. It looks sort of fragile, but there are 10-second 4th Gens that use the stock TA. But, a tubular arm, with multiple tubes and bracing will be stronger. And the design can incorporate an "adjuster" that allows you to adjust the "pinion angle".... the angle the pinion shaft of the differentiall makes with the driveshaft. That angle is critical in preserving the u-joints, and minimizing energy loss in the u-joints under heavy load.

Some of the aftermarket TA's move the front mount to the chassis, to eliminate the lifting effect on the tailshaft of the tranny. This help increase front end lift and wieght transfer on a hard launch, since the arm is pushing up on the body. And holding the u-joint at the correct minimum angle keeps the axle from moving in such a way as to try and lift one of the tires, or bind the rest of the suspension. The wrong pinion angle will also produce driveshaft vibration.

An OK part for a stock HP level, probably the least necessary of all the parts listed. But as HP goes up, its a good idea, and the pinion angle may need to be increased as the power goes up, to get the correct (minimum) angle under heavy loads.

Again, you need to select either a poly bushing, or a rod end mount. And the TA bolts to the rear axle housing with two long bolts, and bolts to the mount in the front, so no welding involved.

Panhard Rod:

Now we have the LCA's locating the axle under the body "Front-to-rear", and the TA keeping the pinion level. But there is nothing to hold the body in position "side-to-side" over the rear axle. That's the purpose of the panhard rod. Its a long u-shaped stamped steel bar that fastens to the axle assembly on the drivers side, and the body on the passenger side. Its bolted, no welding required.

The panhard rod needs to pivot as the body moves up and down over the axle, so it had bushings or rod ends to allow it to pivot. It can also be made "adjustable", allowing the body to be recentered over the axle, for example if you lowered the car. A good idea for most setups. The firmer bushings or rod ends will minimize the offset of the body relative to the axle under heavy cornering loads. Rods ends provide the best freedom of movement, but again, they can be harsh and noisy on a daily driver.

LCA Relocation Brackets:

You didn't mention these, but they bolt or weld to the axle housing, and allow the axle end of the LCA to be lowered to provide more uplift on the body and more down force on the tires during hard straight line acceleration. From my experience, this was the key to good traction and eliminating wheel hop on launch.

Hope that gets you started. You really need to look at a shop manual, or crawl under your car to see what's there, and how it all fits together. I'll try and add some links to photos that show the various parts.

Pardon any spelling errors.... this is just too long to go back and "proof".

Tubular LCA (the lower, red straight bar) and relocation bracket (rectangular black bracket on the axle end):





Panhard rod (long, almost horizontal black bar):



Torque arm (long red bars running parallel to the driveshaft):





I don't really have a good shot of the SFC, because its hidden between the exhaust pipe and the body sill..... this one shows part of it, with the exhaust pipe removed. Not a good example, because its a bit unusual in that it also integrates with the 6-point roll bar.

http://cjcfo.fbody.com/members/injun.../DCP02969a.jpg

Overall view:

Z95m6

Wow! I'm shocked Fred i was expecting to see a post telling him to do a search. Thats what i would of done.

revtime

Fred is very thorough.

and that was the short version?

JakeRobb

Fred, thanks a ton! That was everything I hoped it would be. Would it be immodest of you to sticky your own post?

In the last pic, I'm not sure where the SFC is. Can you specify?

Thanks!

-Jake

Z95m6

http://www.bmrfabrication.com/instructions/sfc001.htm

JakeRobb

Excellent. Thanks again! I'm really curious to hear what's in the long version.

So, some SFCs are square, and some are round. Are there reasons to go with one vs. the other?

Is there a middleground choice between poly bushings and rod ends for LCAs? Something harder than the stock bushings, but not as hard as poly?

You said that rod ends are noisy and have a limited life. How noisy / what kind of noise? How limited is the life? Does a particular driving style contribute more to rod end wear?

You guys are awesome. Keep it coming!

-Jake

respectirocz

if only all our questions were answered so thoroughly

good job injuneer

Injuneer

The SFC in my picture is the gray round tube the runs vertically in the right side of the picture.

The "compromise" on the LCA ends would be a combination of:

-poly on one end, rubber on the other, or

-poly on one end, rod-end on the axle end

"Noisey" is hard to quantify. I have the rod ends on the TA, the sway bar end links, and the LCA's (a late addition, some of the pictures show poly). With all the noise from an exhuast that dumps under the car, the solid roller camshaft and most of the sound insulation removed, its just part of the background noise. But for someone with a boulevard cruiser, and a daily driver, the noise might be annoying.

Spohn uses premium QA1 Kevlar-lined rod ends, and they are supposed to last a while. Again, my car only gets driven a few miles a year on the street, so I doubt I'll ever have a problem with them. I've heard of people putting "boots" on the rod ends, and that would extend the life. Its just a matter of all that road grit getting into the bearing surfaces.

mattybz28

If strength is your number one priority, choose the boxed design. Boxed tubing is torsionally stronger than round tubing however you will lose approximately 3/4" of ground clearance when using this style. If your car is lowered and ground clearance is the prime concern, go with the tubular model.

From BMR