Urban Legend

iTrader: (5)

I did not know ls1tech had some many engineers on call.

Foxxtron

iTrader: (1)

face it,

nobody is going to "shut the **** up" so post your opinion and deal with it.

And FWIW, a third gen is a rattle trap compared to a 4th gen. As mentioned before, I have my 4th gen track vehicle beat like crazy for over 10 years, and nothing like other have mentioned has happened. And also there are roads in many places in SoCal that are like hell holes. My street vehicle has traveled over it for about 20 thousand miles of it's life (150,000).

kc10a

I won't get into the logic or science of this topic, but I can tell you this. When I put the Hotchkis STB on, my wife immediately noticed the difference as soon as she drove it. When I put the SFC's on, she noticed the difference the first time she rode in the car. It also dropped my ET about .2 the next time I took it to the strip. My car is a stock convertible. It's your money so make your own decision. I know I'm glad I bought them. Also, I have the wrinkles on the left rear quarter, but they haven't gotten any worse.

Urban Legend

iTrader: (5)

Get off the Red Bull mate.

Foxxtron

iTrader: (1)

that actually wasn't directed towards you it was directed towards the previous poster. It's just that you posted shortly before.

Urban Legend

iTrader: (5)

I am just playing. You know I do not get into fights online. As a matter of fact, all I know this thread is about sfc. I have not read much.

Jon A

Journal? What parts contained in the paper have you performed for these cars?
I'm not trying to be critical but I really am genuinly interested. Where exactly are you placing them? What exactly are they reading? How exactly are you translating that into meaning anything with regard to the overall stiffness of the entire structure? I'd be happy to look things over and offer some pointers--it's just really not easy at all.
You're right, I should have made it clear that wasn't aimed specifically at you but at much of the mantra in these threads from numerous others.
What people actually "notice" is going to be primarily NVH driven vs. actual deflection of anything, and thats a whole different subject/science (although chassis stiffness does play a large role in it). The human body can notice some amazing things. Type NVH into SAE's search function and more than 3,500 papers/books/studies will come up. OEM's wouldn't spend millions upon millions studying it, designing for it, adding heavy, expensive parts to cars that perform no other function other than reducing it if it was all in peoples' imagination. The placebo effect only works when one knows he is getting a pill, most of the additions to vehicles OEMs make aren't going to be seen by the customer at all--he likely won't even know they're there. But he will be able to feel "something" about the one vehicle that makes it more pleasant to drive than a vehicle not so equiped.

Anyway, like I said, that's a whole different subject. Just don't underestimate what people really can "feel." OEMs wouldn't spend so much money, add cost, complexity and weight to the vehicles trying to minimize it if it wasn't very real. Where the overlap to this discussion comes from is the main reason so many cars are designed with chassis many times stronger than they need to be in order to drive up stiffness, resonance frequencies, etc in order to reduce NVH as that's one of the biggest driving factors. Just because a particular person's laptimes didn't go down after adding SFCs doesn't mean he can't feel a real reduction in NVH.
At most peoples' level (yes, including myself) there are much bigger factors. And chassis stiffening isn't something that directly relates to reducing laptimes anymore than, say, buying LS1 Edit. You might have a stock engine and not even notice the difference. You might modify the engine but be a lousy tuner and not help yourself at all. But if you do modify the engine extensively, and you know what you're doing, it does give you a tool to help all those parts work better together for a better final result.

Take the above paper example of the baseline chassis 9900 ft-lb/deg (roughly the same as a BMW E46 Sedan). They're losing 10% of the front roll stiffness through torsional twist of the chassis. Now imagine trying to build a fast car from a Fox body Mustang (~3100 ft-lb/deg). Imagine trying to fine tune the thing with subtle spring/bar/shock changes--a very large portion of the changes you make will never make it to the pavement but be absorbed by the chassis instead. Hell of a way to try and build a racecar. Let the tail chasing begin....
My WAAG would put it somewhere between the two above examples, hopefully closer to the BMW than the Fox but we won't know until somebody measures. It certainly isn't "bad" but that doesn't mean there's absolutely no room for improvement, either.

Carroll Smith opined that in order to be able to effectively tune the car, the chassis torsional stiffness should be roughly three times the suspension roll stiffness of the stiffest end.

I guarantee you, an F-Body with a 35mm or bigger front bar isn't even close to this without extensive chassis modifications. Does that mean they can't be fast? Of course not. It does suggest there is room for improvment. And as you go up the ladder...a Trans Am car is going to be around 25K, an LMP900 Carbon tub car 37K.... A good question would be do you think cars like that could be competetive with an F-Body stiff unibody?

Foxxtron

iTrader: (1)

In short Jon, you must bear in mind that I am not conferring any type of silver bullet, however for me to volunteer more information of what I'm doing is what I'm not at liberty with. And FWIW, I don't just read solely one journal from the SAE, I acutually read several, and several outside sources as well (one example of this is more watered down, but nevertheless exciting, racecar engineering). Take it as cop out, whatever, but what I am doing (rather I and my other collagues are doing) isn't really for the purpose of this website, or the F-body in general, but something much more encompassing with regard to chassis's in general. You should bear in mind that even though I am not in your occupation as directly and as long as you have, I do deal with materials on an everyday basis.

Now AFA what you mention as far as feel, that's been already confered through what another member here (I believe it's todddchi of something like that?) has mentioned. I do work with those who are involved with human factor sciences as well. I agreed a long time ago that there is not always an absolute direct connection between feel and what's thought to be felt, while some are. With regards to the SFC's they're widely varied from "quieter", "increased" NVH, firmer feel, not so firmer feel, understeer, oversteer, then nothing at all. They're quite varied. Can you directly explain those inconsistencies? Until you can don't assume I'm underestimating anything or anybody. I just want to know more what or less which design is really doing what.

Also, be aware that I'm not just with the F-body for what cars I have in my personal or immediate possesion. I do have three other cars in addition to the current F-bodies that I have. One of them currently in the middle of construction is this car which I am eager to figure out. Also, be aware that I have an 8-point roll cage in my track vehicle and yes, it's similar to those that are touted over at the venerable FRRAX and, and yes there is an incerased stiffness overall, but I am not going to get directly into that.

One more thing, your last statement assumes that I don't think there is a way to improve the stiffness of the F-body, which there certainly is. If that's the case, why again would I be doing what I'm doing?

Down to the point, does the SFC's like you have or what I used to have doing what it's really doing? Where is the stiffness truly added? These are objective questions.

vtirocz

Foxxtron,
Could you please post the part of your report pertaining to 4th gen F-body's chassis rigidity or explain more on how you set up your test? This is interesting and I'd like to see some of your data.

For a stock 4th gen F-body with T-tops, the bending and torsional mode frequencies are 23hz and 20hz, respectively. I'm wondering how those #s would be affected by different types of SFCs welded to the chassis.

I agree with Jon A that chassis rigidity most definitely plays a large role in NVH.

Thanks,
Jim