comments.... this is on an 84 Trans Am Chump car. The front splitter will be done soon as well. We are looking for some down force going into turns after a straight. If it matters I will be making "sail panels" to help direct the air into the spoiler. Feel free to critique, keep in mind this was hand made from a single sheet of lexan.

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That's a LOT of rear downforce.

I didn't want to go that high, however the guy that made it is a 3x track champ so I gave him the benefit of the doubt. I guess his logic is that the butt end of the car is so much lighter than the front we need some downforce. He did say if it is too much we can always cut it down. The car will be run at New Jersey Motor Sports Park, Summit Point and VIR. I think they are all around 2 mile tracks. Summit and VIR have lots-o-turns.

Very true. You can always cut down. A bunch of rear force can tilt the front up, but if you have a good front spoiler like a splitter, probably not issue.

Our circle track cars only run half that height. It does make a difference. Just wonder if you are limited HP, the extra drag might hurt you? Real way to find out is good testing.

Splitter is in the works. He asked some F body guy about the speed thing, this guy runs the same car we have w/ a 10" spoiler, he said while it does slow him a little he dropped 6 seconds a lap. Now when we do Daytona (next year I hope) we'll run a completely different spoiler and probably do some engine work. Right now we figure our mad ass 305 is pushing 230hp.

The '67 Chargers only required a tiny spoiler strip on the decklid to put the rear down again on the Nascar tracks.

How about putting a streamlining diffuser under the rear of the car trying to 'pull up' the air behind the car.

that's what my friend said, he said a diffuser would work better but we'd have to cut the well out of the car. This was quicker. As I recall the 67 Chargers were a handful and Dodge begged NASCAR for a spoiler. That little lip was all NASCAR allowed. At a track like Daytona you don't need a ton of rear down force. I think what we want is to be able to get into the turns w/o a lot of brake. We can pull 75% of the cars in the straight....it's the corners that give us fits. We have done a few other things like rebuild the 30 year old suspension and drop the car 1.5"'s so that should help some too.

You can cut it down and save the pieces to be bolted back on for different needs too.

yes I'm thinking about making different sizes for different tracks. This Chump racing is fun.

Does this have a yet to be installed back window? I would think the airflow would rather turbulent without a window, and decrease efficiency of the spoiler requiring it to be much higher to be useful and therefore greater drag. What speeds are talking?

Didn't notice the lack of rear window. Nice spot.

Local circle track legend around here might give you some idea's?
http://autoracingmemories.com/forums/picture.php?albumid=503&pictureid=7247

Google "Junior Hanley spoiler"

holy spoiler alert batman!

no back window. We cannot run the glass hatch. We will be making a Lexan piece in the future. I was going to fab up some clear sail panels to direct the air better. I'm guessing on the long stretch at NJMSP and Summit point we're at 115-120. If anybody is good w/ math we run a auto w/ 3.75 (non-posi) rear. At the end of the straight before braking we are at about 5800-6k. (in 3rd not OD)

That will definitely be a point of turbulent air. I would have sealed that up well before worrying about a spoiler. But that's just my 2cents...the spoiler looks like good handy-work though!

we get dinged for Lexan/plastic $X per cubic inches/feet. We are close to the $500 limit now. Once we see how much room we have after our mods are added up. We should have room for the rear hatch.

Why not get some new glass installed?

we have the glass hatch.. 1, its HEAVY and 2, not allowed to run it. Only glass allowed is the windshield.