Volhv_944

I have one of Joe Toth's splitter on my 86 NA.
Beefed up its mounting significantly.
- Two adjustable rods holding it up inside the valance at both front corners (attached to the aluminum bumper)
- Bolt on the middle of the valance's lower leading edge
- Ditched the self tapping screws, and stamped steel anchornuts in favour of proper threaded hardware in the aft corners

One thing I did not do, is bond it to the valance using body molding tape.

At about 100 MPH, or 160 KPH, the front end starts to shudder very violently. I immediately decrease speed, and all returns to normal.

Anyone else experience this?
Would a perfect seal between the splitter and valance eliminate this?

konakat

I would imagine it would. Air is probably squeezing through the gap once the pressure is high enough and causing everything to vibrate like the reed on a clarinet.

HICKS

I imagine that the splitter is more decoration then function. Toss it, or quit going 100+.

Arominus

Does it do it without the splitter on the car? and yes a better seal would be a good idea, that splitter is working hard at that speed.

Jrboulder

+1

TonyG

The problem with his design is not the shape, its that it's doesn't have enough material to make it stiff enough so that it doesn't flex.

I tried to explain this to him and he told me to go F off. So I took a mold of his design and changed it as well as to reinforce it with wood in the front.

Reinforced, it works excellent.

So much so, that at high speed you must have a couple of vertical support rods to keep the AOA from changing due to the rubber front nose flexing, or the nose from being ripped in half which is the case of when using an aftermarket fiberglass nose.

TonyG

Volhv_944

Good one Hicks.
It's more than just for looks, but I must admit It does look awesome. It extends underneath the car all the way to the front tires, smoothing out all the holes under the valance. It's like an NA batwing.
And the shuddering (witch started once I installed the splitter) is proof that it does have aerodynamic properties. Its design should generate some pretty good down force.

Thanks for the input Tony. I'll have to mess around with it if it still causes issues after I seal it to the valance. Maybe some strengthening with a bit of sheetmetal, and metal rods around the perimeter.
Since it does attach to hardpoints on the body, as opposed to just the valance, I doubt I'll rip it off. But you never know.

TonyG

The deal is that aero devices need to be very stiff without flex. If the device flexes, the aero changes.

And the Joe Toth splitter can only be fixed by doing exactly what I did, which was go fit a stiffener to the underside along the entire width.

You can't have a rear wing that flexes. The front is no different. It's got to be rigid and fully supported. Otherwise you'll have problems.

TonyG

azbanks

+951


Have you ever had the factory nose crack using your splitter(I haven't, I'm just curious)? At what speed would you recommend going with the support rods?

TonyG

Have you ever had the factory nose crack using your splitter(I haven't, I'm just curious)? At what speed would you recommend going with the support rods?[/QUOTE]

The factory nose won't break because it's flexible. However, that flex will allow the splitter to change angle at high speeds.

The fiberglass nose will break apart along the lower center openings from the force exerted downward by the splitter. The more it splits apart, the greater the angle of the splitter, the more it pulls the nose apart.

In both cases, at high speeds (racing) the splitter needs to be supported because of this.

TonyG

T&T Racing

I have the same splitter installed on an '83 race car. The splitter did vibrate at 90-115 mph and the vibration/deflection caused the front valance to crack where it was previously repaired.

Gen I was to attached the splitter to the front valance with brackets and dzus fasteners to make it removable. The rear of the splitter was attached to the aluminum engine undertray (home fabricated) with self-tapping metal screws.

Gen II is to attach the splitter on the left and right side with the same brackets but install four 1/4 in. rods attached to the bumper, spaced across the front valance at the bottom of the radiator opening. The rods will be screwed into the bumper and locked in place with a nut. The bottom of the splitter will have aluminum flat stock attached to the bottom of the splitter to distribute the vibration and flex load to avoid cracking the splitter. The length of the flat stock with be 3 in more on each side of the spacing of the rods. The rods with be locked in place with washer and nut on the top and bottom of the splitter. This will also allow for fine-tuning the contact with the front valance.

Gen II is work in progress. Complete date late April

Tom

murrayg

I also have one of Joe's splitters on my 84. It also shuttered at high speed. I discovered it wasn't a issue with being not rigid enough, but the problem was it was installed at a slight "nose up" attitude. This is bad. I adjusted the rear attachment point (also home made because of the early car) up to lower the leading edge. I used a level to ensure it was just slightly "nose down" and problem solved. Does it perform any aero function.....maybe, but I don't care, I love the look of it!

TonyG

That just made it load up and flex downward and yes..... eliminated the flutter.

It did not fix the problem.

The problem is that it's a very flimsy splitter with zero reinforcement.

TonyG

TonyG

Here's how you fix it.

You need to bond in a piece to make it a) rigid, b) has something to fasten supports to, and c) won't shatter if you bump it against anything.

This is tried and true on the race track for many years now.


The last picture shows the correct way to support the splitter for track use, and requires a turn-buckle style support connected through the bumper skin to the actual bumper.


TonyG


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Volhv_944

That's a pretty good solution to the flexing issue.
Only thing, those fasteners around the perimeter, there's no easy way to do it on the NA, since the valance drops straight down. That's what causes my shuddering.

I recall Joe being annoyed that someone copied his design, now I know who he meant.