2 Questions - Exhaust System and Spark plugs

[IJ.]

Sorry Dave on this one I have to disagree.

"IF" the strut bar had 2 bolts on each end it might transfer some of the loading but they don't so "IF" there's deflection in the Tower the Strut bar is acting as a hinge and not transferring anything anywhere.

Grab a cardboard box unfold it's ends so it's an open tube, think of the lower horizontal as the front subframe the verticals as the towers and the top horizontal and the Strut Bar.

Deflect the lower corner and watch what happens....

Fold and tape one end closed and repeat, this is where the extra bolts would come in.

As designed they're nothing more than a fancy hinge that needs to be removed if you're working on the car.

 

[Poodles]

Depends on design.

The MKIV bar is one solid piece without hinges...

 

[supradjza80]

Sorry Dave on this one I have to disagree.

"IF" the strut bar had 2 bolts on each end it might transfer some of the loading but they don't so "IF" there's deflection in the Tower the Strut bar is acting as a hinge and not transferring anything anywhere.

Grab a cardboard box unfold it's ends so it's an open tube, think of the lower horizontal as the front subframe the verticals as the towers and the top horizontal and the Strut Bar.

Deflect the lower corner and watch what happens....

Fold and tape one end closed and repeat, this is where the extra bolts would come in.

As designed they're nothing more than a fancy hinge that needs to be removed if you're working on the car.

I am not sure if that analogy works perfectly in this respect but I do understand what you are saying.

I know a way to find out, but I don't think Goodyear will put a Supra on their Kinematics and Compliance machine because I want to find out the measured deflections with and without a strut bar . I was thinking of bars like the TRD one for the mk4, not the cusco or whatever 1 that mvp carries for the mk3.

One reason I think it may be more complicated than that is looking at some OEM vehicle designs, for instance the rear of the 350z has a strut/shock tower bar. By our logic that bar makes no sense, but there is someone at Nissan that knows why that bar was put there, whether for the chassis or for aesthetics is unknown but I believe that bar is only there for a engineering purpose as most customers would probably have liked to have the extra storage area.

Actually the more that I think about it I think even the strut bar acting like a hinge does help our cause. Deflections are inevitable, when a load is applied things need to move/deflect to support the load (even if the deflection cannot be seen), without the strut bar all the load is applied to the one side of the car and none of it is transferred through the top half of the engine bay - maybe in some form through the upper radiator support and the firewall but even then you still have no lateral support near the top of the tower near the same location where the load is entering the chassis.

With the Bar on the car acting as a hinge, it allows some of the load(maybe very little, maybe a decent amount (1/8-1/4) is transferred to the other side of the car. If the one tower would normally be deflected by load 1/8" without the bar, if the load is able to be slightly transferred to the other side maybe it now deflects only 3/32". In effect the bar is transferring some of the load to the other side and effectively lowering the stress in the laden side of the vehicle and therefore reducing the displacements seen by the laden tire. While cornering the Laden tire is the one you are most worried about as far as holding the correct camber etc. so that is the side you would like to reduce deflection from. The unladen side has much less force going through it as well.

Again this is only hypothetical and mostly myself thinking out loud. Depending on the quality of the strut bar, material choice (the bars spring rate ( should be very, very high, determined by young's modulus and strain data), etc. it may or may not make a difference.

To bad they don't just let anyone test things like this in a scientific manner to prove if some parts work or not. Maybe if I get a job with Goodyear next year I can somehow get my car on there to see how it performs

We are lucky enough the use the K&C machine to test our formula car and it is a very helpful tool to determine where compliance is in a suspension system.

Here is some info on the machine for anyone that is interested. It is pretty awesome to use. http://www.abd.uk.com/categories.php?Cat=79&PageTitle=Kinematics%20& Compliance

 

[gaboonviper85]

Depends on design.

The MKIV bar is one solid piece without hinges...

with or without hinges it's still not strong enough with up/down flexing...it's design is great for side to side but that piss-ant bar will flex right along with the chassis!

Bolt only one side of the bar down and I bet you can flex it like it's nothing...the car will do the same even with both ends tied down....placebo is all they are!

 

[supradjza80]

just found something Wiisass posted in the suspension section of the forum on shock bars...


As for shock tower bars, they won't do as much on Supras because Supras don't have struts. A strut is a damper that is also a suspension member and is active in locating the suspension. The shocks on the supra are not needed to locate the suspension, so they see different loads than a strut would see. Due to its design a strut sees a load perpendicular to the upper mount, this is why a strut tower bar could be needed. A similar bar on a non-strut car does not see the same loads and is meant more to just brace the engine bay. Which on some cars isn't really needed. It will add some amount of stiffness depending on the design of the bar, but how big or small is hard to say. But I would think it's safe to assume that the more expensive bars don't do much more than the cheaper bars besides look a little prettier.

Tim

 

[IJ.]

Dave: The Mk4 style bar is what I mean by a double bolted non hinge design instead of the stupid Placebo Bars everyone else sells

I'll drop it all now as this discussion has been had here quite a few times and usually ends up with ill feelings.
(my analogy is near enough for this topic and is only to make the subject easier for people to understand, you just need to look at the direction of force in the shock tower to realise the single bolt design does nothing)

 

[Poodles]

You could easily stand on the MKIV bar :rofl:

 

[Grandavi]

You could easily stand on the MKIV bar :rofl:

Nah.. its an excellent chin-up bar for the den. Just bolt it to the studs and ... voila! Chin-up bar! Or.. for the kinky out there....

I can see the 2 sides to it, but really I dont believe that the way these bars are situated will do enough good to warrant usage. The bad part is.. if you do have them on and you get hit.. it will transfer the load to the other side of the car better.. meaning.. more damage. (these dont crumple...)

Mine is 3 bolts for the top of the tower (strut tower? shock tower? TEMS cover.. lol) and then has 2 huge nuts (the metal kind) that you use to take up slack. They cannot pivot side to side, but will pivot up and down. I think the up and down part is good, because if not, it could affect the steering (minimal.. ). But no matter how you cut it, I just can't "mechanically" visualize how they would do any good whatsoever. Other than lowering HP.. they are heavy

 

[figgie]

while the Strut bar/shock bar does not help with the loading the shock towers see due to suspension compression, or bump situations, A shock tower cross bar does help with chassis ridgidity. It allows the loads going through the chassis monocoque to be distributed to the other side of the vehicle.

Even on a strut vehicle which inherently has more loading through the strut towers, the vast majority of the load still acts in the direction the damper travels in and the strut bar is there to help distribute the load across the chassis and to stiffen the chassis up.

Most of the load going through the suspensions a-arms goes through the lower control arm (the laden wheel has compression going thorough the lower arm and tension in its upper arm).

Do I think it is worth it for a tower bar? That really depends on the car and your plans for it. If I was road racing I would have one. If I was just worried about the targa off "shake" I would not do the mod.

We are lucky Toyota did it right though, we have proper A-arm suspension unlike many other cars in the supras class(mk3 & mk4). M3's, 911's, Evos, Sti's, all have struts, and in terms of tire control, how the tires contact patch is controlled to the road surface, A-arms are superior in everyway.

Nope

that is not the case as you would need a THIRD point. This is basic force vectors.

My rought diagram shows the force vectors. Assume the left side of that is on an immovable part of the car.

So if the entire system moves up and down. How exactly is the strut bar doing anything except allowing it to go up and down on the predetermined circumferance as dictated by the length of the strut bar?

Answer is it does not. Now if you are implying that Toyota made it flex to a certain degree. Of course, otherwise we would be running around with a 10 point roll cage that attaches and transfers every single load point to the cage and not the frame of the body. Check the Cadillac CTS-VR and most of the touring class cars. They weld addition material on the portion where the A-Arms connecto to the frame to make it as ridig as possible within the race cars class's limits (no full blown cage where the cage is the mount points for everything) and then weld that to thier cages.

 

[supradjza80]

Nope

that is not the case as you would need a THIRD point. This is basic force vectors.

My rought diagram shows the force vectors. Assume the left side of that is on an immovable part of the car.

So if the entire system moves up and down. How exactly is the strut bar doing anything except allowing it to go up and down on the predetermined circumference as dictated by the length of the strut bar?

Answer is it does not. Now if you are implying that Toyota made it flex to a certain degree. Of course, otherwise we would be running around with a 10 point roll cage that attaches and transfers every single load point to the cage and not the frame of the body. Check the Cadillac CTS-VR and most of the touring class cars. They weld addition material on the portion where the A-Arms connecto to the frame to make it as ridig as possible within the race cars class's limits (no full blown cage where the cage is the mount points for everything) and then weld that to thier cages.

The point of the bars is to reduce chassis flex, not to absorb vertical loading from the shock. I thought my post stated that fact a few times in a clear and concise way.

Your diagram has the chassis force for the upper control arm pointed in the incorrect direction. The lower control arm is under compression, and the upper control arm is under tension as your diagram shows. The chassis sees the force you drew for the lower control arm but sees a force in the opposite direction for the upper control arm.

I think Strut/shock tower bars are there to help tie the two sides of the chassis (which will flex under corner loading) together just like a ten point roll cage ties into the shock towers.

anyway, it is normal even for engineers to have difference of opinion when analyzing a system there is only one way to know who is right and that is to test it. None of us have access to a testing machine so it will be unlikely anyone can "win" this battle.

 

[IJ.]

Arrows on the arms are backwards

 

[supradjza80]

Arrows on the arms are backwards

thats hard to say without it broken into a FBD, basically both ends of the lower arm should have forces pointing away from the center of the arm and both ends of the upper arm have forces pointed to the center of the arm.

 

[Grandavi]

anyway, it is normal even for engineers to have difference of opinion when analyzing a system there is only one way to know who is right and that is to test it. None of us have access to a testing machine so it will be unlikely anyone can "win" this battle.

Agreed!

Now.. on a totally different tangent... I gotta replace my gas tank. Is it me.. or does every MKIII owner run across these little nightmares springing forth when you least expect? And... how the heck did I get a leaking gas tank???

sigh.. dont think you can patch em.. so time to look for new...

lol.. 900 bucks new... I have found a couple links on repair and actually found a shop that does it.. so I will post elsewhere regarding this when I do it... (never hurts to have input!)
(oh yeah.. I searched the forums and didn't find much information on repairing these.. but apparently there are sealers that do the trick when applied properly... is there any better way to get intimate with a Supra then tearing it apart piece by piece?)

 

[starscream5000]

IJ. may know, he's done a lot of work with his gas tanks.

 

[IJ.]

Dave: We're talking Compression as I can't see even the best Tower bar doing diddly for rebound

Yep you can weld some new steel in to patch the holes then coat ot with a tank sealer, I'm using KREEM it's a sealer a lot of Harley guys use.

 

[supradjza80]

Dave: We're talking Compression as I can't see even the best Tower bar doing diddly for rebound

Yep you can weld some new steel in to patch the holes then coat ot with a tank sealer, I'm using KREEM it's a sealer a lot of Harley guys use.

Ok I now know for sure you guys are not understanding me. Strut tower bars dont do anything for the compression or rebound of the damper. They don't add any appreciable amount of stiffness in the vertical direction.

I am talking about tension and compression in the individual suspension arms (upper and lower A-arms, control arms whatever you want to call them). These put loads into the chassis that the tower bar helps distribute. Others may disagree but this is my opinion from my education and what i have learned.

I believe how the towers are constructed (stamped steel with a circular edges very near where the strut mounts) makes them extremely stiff from damper and spring loading. I do not believe that strut tower bars help with damper and spring loading in any appreciable amount.

 

[IJ.]

I was talking about the force vectors on the arms Dave...

Myself I don't believe tower bars do much of anything other than get in the way.

Simple test that I've asked someone/anyone to perform before is to install a bar on the flat adjust the rod end so it has 0 preload, Unhook the bar find a steep driveway turn in so one front is loaded then see if the bar will bolt back in place.

IF there's chassis deflection the Bar won't bolt back in.

I could set this test up using strain gauges and log the results but I'm not going to blow $ to prove something doesn't work.

 

[supradjza80]

I was talking about the force vectors on the arms Dave...

Myself I don't believe tower bars do much of anything other than get in the way.

Simple test that I've asked someone/anyone to perform before is to install a bar on the flat adjust the rod end so it has 0 preload, Unhook the bar find a steep driveway turn in so one front is loaded then see if the bar will bolt back in place.

IF there's chassis deflection the Bar won't bolt back in.

I could set this test up using strain gauges and log the results but I'm not going to blow $ to prove something doesn't work.

So you are talking about compression and rebound in the compression arms? Or did you mean compression and tension. Compression/bump and rebound means damper motion. Compression and tension is the forces measured in links that carry load and is a way of saying the direction of the force.

Putting the car on driveway with the wheels un-evenly loaded does not come close to simulating the forces that the chassis sees from wheel loading while taking a corner at 1 g.

Its fine though, I don't really want to talk about this anymore. The fact still stands that it may or may not work for the purpose I brought up earlier. If it works great, if it doesn't thats great too.

Again, why would an OEM performance car have tower bars (even on A-arm vehicles)? Only because they do something.

 

[Grandavi]

There is no true answer for the strut bars actually... they sell them for 10 bucks or 34 bucks.. depending on which ones .. (the one's I have seen anyway). I dont imaging a huge amount of engineering going into them. I bought the bar, but as I said before, I wont be putting it on. Its "iffy" as to what it will do, but what I want it to do, it definitely wont. The TSRM Maintenance point about tightening the frame should do the trick mostly.

Now... after finding my gas tank leaking, my 77 Ford Motorhome overcharged the battery... lol. Man.. good luck so far... smelling sulfur all day long, no idea what it was and then notice the battery cap on the ground. Someone just doesnt want me to have money...

As for the gas tank (I didnt intend to discuss so many things in this thread), I saw the following which is supposed to seal pinhole leaks etc.. but i will have to pull the tank to use it correctly (which isn't a bad thing because I have a rust hole in the driver side rear wheel well that I am wanting to fix. Luckily my wife's dad can weld ) Not sure if any of you are familiar with this stuff for gas tanks.. but the manufacturer has good claims and even vids to show you "how to"
http://gas-tank-repair.net/

 

[Poodles]

Well, you could have the tank welded. You MUST purge the tank to do that though...