posted on December 13, 2010 17:26
Project S2000, Stiffening the Chassis
By Khiem Dinh
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
As with anything, a strong foundation is the key to success. For a good handling car, that means a super rigid chassis. The S2000 is blessed with a very stiff chassis from the factory, but when you chop the top off of any car it will be less stiff compared to a car with a roof. The S2000 doesn’t have the bad cowl shake that is the tell-tale sign of a not-so-stiff convertible chassis, but there are a few creaks from the soft top roof as the chassis flexes.
A flexing chassis is a detriment to handling because it does not allow the suspension to work properly. Firstly, chassis flex alters the suspension geometry. Secondly, the chassis acts like a big spring without a damper, meaning we have no control over it. On a stock suspension setup with relatively soft springs, the chassis flex is not as noticeable as the stock springs are soft enough to absorb most of the road input energy. Since we’ve just basically doubled the stock spring rates, more force will be transmitted to the chassis increasing the displacement that it twists and flexes. This means greater alteration of the suspension geometry and more uncontrolled chassis flex action.
|The Whiteline front subframe brace mounts where the stock engine mount stiffener and gussets attach.
To combat those forces, we’re going to fortify our chassis with some additional bracing. Honda did a pretty good job from the factory with some chassis bracing, but there’s always room for improvement on a street car. One of the most common braces is the 2-point shock tower brace. With no brace, the tops of the shock towers are free to flex inwards and outwards relative to each other. We’re using a Whiteline brace between the shock towers which ties them together. By doing so, we’ve just eliminated that degree of freedom helping to keep our suspension geometry optimum.
|Whiteline front strut tower brace.
|Whiteline front strut tower brace in place.
Tuesday, December 14, 2010 4:19 AM
"Without a full-chassis twisting machine, it’s hard to quantify the added stiffness, but it can certainly be felt through the seat of the pants."
I present you a <$70 chassis twisting machine & measurement device:
Tuesday, December 14, 2010 5:15 AM
That washer bag is an old Nissan item used on cars like my 240Z. Nice to see it used on a very quick sports car that is the S2000, makes me feel better about my Datsun LOL!
Tuesday, December 14, 2010 5:28 AM
The more I read suspension articles featuring Whiteline products, the more impressed I am with their quality and workmanship. Whatever car I end up getting is going to be equipped with Whiteline components.
Tuesday, December 14, 2010 7:54 AM
On a convertible, the floor structure is basically the only thing keeping the front of the car from twisting relative to the rear. All these braces stiffen the front and stiffen the rear but do nothing for the floor area. So now you have a stiff front, stiff rear, and floppy middle. Seems like a bad thing.
Tuesday, December 14, 2010 7:56 AM
I look forward to the track results should be night and day when compared to the stock S2K. Just the front end improvements alone should be enough to elminate almost all of the understeer right?
Tuesday, December 14, 2010 8:20 AM
Miro, you are correct that the floor is the only thing preventing flex in a convertible. However, the whiteline brace reinforces the front subframe and the beatrush the rear. So not the chassis directly. As you can see in he diagrams from the Honda fsm, you can see the suspension arm mounting points. The nagisa brace does reinforce the chassis surprisingly well; they were suggested to me by robispec. back to the subframes, the stability of the car and suspension action have both improved, especially the rear. Typing from phone, sorry for errors.
Tuesday, December 14, 2010 10:48 AM
spdracerut, you forgot something in your $70 twist machine:
Tuesday, December 14, 2010 11:05 AM
@spdu4ea, $70!? reading between your links for ramps and a laser level, I think I know what you're suggesting and I did that with SCC's project SE-R a million years ago with a $3.00 laser, some epoxy, and $0.50 of Radio Shack magnets. Forget ramps, just remove one of the wheels...
This is a reasonably effective way to check if your changes have any impact on full-body torsional rigidity (I learned that my diagonal strut-to-firewall brace was about 10x more effective than just the straight across strut tower brace), but there are benefits to improving localized stiffness even when it doesn't show up as a torsional change. Anything that supports suspension mounting points is good, as they see loads in all kinds of crazy directions that you won't see with some simple ramps.
Tuesday, December 14, 2010 11:46 AM
Haha, I'm not surprised Dave Coleman aka MacGyver already devised a similar testing apparatus. Most engineers are always crying out for crazy expensive equipment when dealing with simple problems -- the best improvise when needed...
Anyway you can attach the laser to different points of the car to measure deflection angles between various points (or just use multiple lasers) and if you orient the graphing/computational paper carefully you can easily break those deflection vectors into horizontal & vertical components to really nail down where the improvement lies.
Combine a Go-pro camera with more secure mounting and the adventurous can measure deflection in the real-world...
Tuesday, December 14, 2010 1:31 PM
The deflection is typically so small that the laser and target have to be really far apart to see the movement. The farther apart you get, though, the more the laser scatters. Bigger dot = harder to interpret results. With my triangulated strut tower brace, the deflection from the front of the car to the rear was less than the width of the laser dot.
My advice is to use this kind of measurement to teach yourself how these reinforcements work, try to understand the structure you're reinforcing and the load path of your brace, and then just use your newfound common sense when designing/choosing/installing braces rather than trying to back everything up with dubious data.
Tuesday, December 14, 2010 7:28 PM
Isn't the fender area integral to the crash safety of the car or is the brace not strong enough to have an effect in this area? That was my only reservation about having them on a street car.
Tuesday, December 14, 2010 10:25 PM
Jeff, I dug up some vids of the S2k in a frontal crash test and a few other random cars. The majority of the crumple zone is in front of front axle line. There appears to be some crumpling where the front of the brace attaches, I imagine it'd just bend the brace at the mounting points a bit, maybe tear the sheet metal some.
Wednesday, December 15, 2010 5:04 PM
Love the individual testing after each brace was installed. Will definitely be looking at TRD fender braces and underbody braces for my JZX100. Skipping the tower brace, but looking at more solid engine mounts.
Sunday, December 19, 2010 9:45 PM
Hey, its great you're doing this, what are the chances of doing a rolled up budget of the changes you've done so far, either MSRP or 'street price'. i'm a cheapo!
Tuesday, December 21, 2010 12:03 PM
@slowpoke..... a word to the wise, NEVER add up how much you've spent! You'll want to shoot yourself! Out of the chassis bracing... I think the Beatrush rear brace would be the #1, followed by the Nagisa fender braces. The J's Racing fender braces are significantly cheaper, but based purely on the pictures available, I thought the Nagisas would be better. They put a BIG dent in my pocketbook. As for all the mods on the car, there are some places you can go cheaper like on the wheels/tires. For suspension, as badass as the Clubsports are, the V3s may be perfectly adaquate or even S2k CR suspension. I'm very particular about how I build my cars, and pretty much go for the best that's reasonable (clubsports as opposed to Moton motorsports); because of this, it takes me a while to save up the money to do each step. But to me, it's worth it to wait longer to save up the money for the better parts. And I don't waste money on 'bling' or cosmetic parts.
Tuesday, March 15, 2011 11:52 PM
If you're into chassis stiffening, the floor bars (asm, cusco, carbing) does wonders for the fore and aft rigidity, especially on uprated suspension
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