Project: The Anal Probe

[Sven7]

Thanks Smurf! I'm staying away from DSM's like they're meth, but I think a TDI will be in my future. Hopefully with a 3-Wheeler style fiberglass boat tail. Take my advice- when you start out, don't start with a 24mpg car like this. Buy something efficient like a Metro or Civic. Your gains will be that much more significant! I bought the Probe because it basically fell into my lap and it's a cool looking car. Nothing wrong with that, but not a great strategy for saving fuel.

Doing things "quickly" helps if you work outside for 6 hours a day messing around and have a large stack of free campaign signs like I did last summer.

------

I'll buy a Mk3 TDI before I build a Kammback over the rear window of this Probe. The visibility is too good now to spoil it and I don't have that kind of energy.

Priority aero wise, roughly, is:

-boat tail
-front skirts
-basjoos front
-wheel strakes

-buy something better

[Sven7]

I've been mulling over the boat tail for awhile, unsure of how to proceed. Well, after talking with my dad we came up with a solution. Trusses! Thanks Dad :wub:


Boat Tail Progress by Tyler Linner, on Flickr


Boat Tail Progress by Tyler Linner, on Flickr

I ran out of material today but it will be getting some cross bracing on the top and some hoops on the front end to guide the coroplast. I decided putting radii on the rear end would be too much trouble for how short/flat it is- any vortexes coming off the end shouldn't be too big.

The wake of the stock car is about 64"x32", or 2048 sq in. The new wake will be 36"x7", or 252 sq in.

That makes the new wake only 12.3% the area compared to stock. Should be good on gas!

Also done this week are some side mirrors. I haven't had side mirrors since last August but never had a problem with visibility. But for $2 a pop how could I resist? It'll be pretty hard to sneak up on this car.


Interior Rear View by Tyler Linner, on Flickr

And the grease in the wheels, Cab Calloway and Artie Shaw!


Good Music by Tyler Linner, on Flickr

Have to do some more wiring to get the side markers put in where the stock turn signals were, then extend the ground wires on the tail lights and mount those bad boys. Then to hook up my novel hatch latch solution.

One area of thought is a back-up aid since the boat tail will be completely and utterly out of sight from inside the car. There's an electronic distance sensor parking deal at Menards for $40 but I'm cheaper than that. I was thinking a simple orange fiberglass temp. fence post on a pivot. I could pull a cord inside the car, the small, 1/2" dia post would swing up and I could judge distance with that.

I've also been drooling over pitot tubes like those on airplanes to aid in effective slipstreaming, but have more research to do before I think too hard about it.

[Varn]

How are you going to keep it from shaking side to side. Might be good to consider welding up a frame from steel. or at least bolting in some diagonals. I bet steel could be built as light.

BTW nice shape.

[2000neon]

That's looking great so far, keep it up, I love this car.

[Sven7]

Originally Posted by Varn

How are you going to keep it from shaking side to side. Might be good to consider welding up a frame from steel. or at least bolting in some diagonals. I bet steel could be built as light.

BTW nice shape.

Originally Posted by Sven7

I ran out of material today but it will be getting some cross bracing on the top and some hoops on the front end to guide the coroplast.

It'll be attached underneath the ridge on each side of the hatch (where the tail light used to be) and across to the opposite side of the rear plate. There will be two, perhaps both angle bar, in a cross pattern. I held a piece in there today and it feels like it'll be super solid.

Originally Posted by 2000neon

That's looking great so far, keep it up, I love this car.

Thanks! It should be a fun week.

[Cd]

Dig it !

[Smurf]

Looking good! Couple questions:

By "wake" area, do you mean just the back surface of the car, or the rear glass as well? How is that calculated?

And with 12.3% of the original wake, any guesstimate on FE impact?

[Sven7]

Wake area (to me) is the area that has detached flow. Since the rear glass is peachy in my book, I took a tape measure to the rear end. Not very scientific but it's a good estimate.

I'm expecting 10% improvement, or about 4mpg. Combine that with 1mpg for the belly pan and 4mpg for E0 gas... calculations suggest 45+mpg without P&EOC? Perhaps 50 if I do a front end extension and full (to the rockers) front and rear skirts, and try really hard?

[MetroMPG]

10% improvement at what speed? Don't forget the % savings from aero mods increase as speed (aero load) increases.

[Sven7]

55mph. Mostly a guess, but 85% wake reduction's gotta count for something.

Is there a formula for drag reduction as a function of wake reduction? From that I could roughly estimate aero improvement and MPG improvement at 55.

It also matters how I drive. Steady at 60-65mph gets 35-38mpg. P&G, EOC and slipstreaming gets 41-45mpg.

I do value your opinion though, Darin. You've done this and so many other mods before, with testing. Seeing the structure, what do you think it'll get?