Cerox

[razordave]

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How about a bug deflector? Would a piece of plexi mounted to my hood on the headlight plane direct the air to the roof instead of the windshield?

judging by the aero template, my plan should work, maybe a 2-3 degree angle?

[freebeard]

The Anal Probe is legendary.
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Not quite. It has a flat spoiler, Bonneville style, and a difusser. Race cars are built to the rule book, which is why (I suspect) the endplates are rectangular and that size.

I question the validity of the difusser. It had a slot opening to the front that was maybe 1/6th or 1/8th the opening at the rear. In theory, that would expand and slow the air reducing the base pressure. (aerohead?) I think it just increases the area the base pressure is sucking on.

If the rear edges of the spoiler and difusser were aligned vertically, and a small fillet was added to connect the two, that would constitute a box cavity. But that might not fit the rule book. And it would be a fairly inefficient one, as a box cavity is supposed to step or curve inward to fit The Template's line.

Here's another picture from Bonneville. (Note the similar sized endplates) The sides of the difusser are curved and it's open on the bottom.



I think that would be better. Here's another example with fences:


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As for the 'bug deflector', the onrushing air pretty much flattens against the frontal area. At the point of the headlights about all you can do it try to divert it sideways. See the Nissan Leaf's headlight and rear-view mirror.

[razordave]

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So I need to look at the template like so? In which case I need more boat tail?!

I'm wondering if I could raise the rear to make the slope of the hatch a little less? That would also make my muffler a little less of an issue..

[razordave]

imagen

Here are the skirts on my other car "89" I haven't really investigated how they are mounted, I think I remember drywall screws?! but to keep from butchering the decent set on the 88, I'll just take the whole rocker cover and swap over.

I also saw a celica with a wing that looks interesting.

The photo sucks, I know, but while driving I couldn't do any better.

To me, it kinda looks like a superbird wing, just not as big.

[some_other_dave]

Random thoughts, not well organized:

Bug deflectors are generally good for creating little vortexes all along them, and not generally good for MPG. Remember, the front of the car doesn't contribute that much to the drag; the rear is where the real improvements come. (Not 100% true, but for most cars made in the 80s and later it's true enough.)

Anything you can do that will create downforce will also create drag. The real trick for race car developers is to create "enough" downforce without creating "too much" drag, and the real art is in determining where those tradeoffs are and how much is enough and too much.

Anything you do that opens up the back of the passenger compartment of the CRX is going to suck the exhaust into the cabin. Don't do that.

You might be able to get some drag reduction out of something that looks like a diffuser but is too shallow to really act as one.

You might try some cardboard or coroplast to get the hatch up to the line of the template. Do coast-down testing (ABA testing) to see if it helps.

A race car is not a street car. Most things that work on race cars are useless on street cars. That "superbird" wing on the Celica is most likely just for show.

-soD

[freebeard]

A forward rake can be helpful (see my avatar) but it would have to be pretty radical to rotate the roofline up to The Template. You will probably be constrained by that side skirt kit.

Keep in mind that The Template is half-circular in cross section. It's more like a guideline. Some car get away with a seemingly too-fast roofline, The GM electric EV-1 for example.

You want the air that flows along the edge of the roof to stay there. If the roof falls off too fast, like a VW Beetle, the air on the side spills up and over onto the top creating vortexes. If a roof was flat on top, but tapers too fast on the sides (I can't think of an example), the air would roll off the top onto the sides and create vortexes there. So the taper of the sides and the top need to be copacetic.

By being half-circular The Template minimizes the problem, then managing the curve's fall-off keeps the thickness of the attached, turbulent layer as thin as possible.

A row of tufts along the edge of the roof would be instructive. They shouldn't pull up onto the roof or be plastered onto the sides, but point along the edge.

[aerohead]

Originally Posted by razordave

Seems to me as if the first gen's roof is higher in the front, more dramatically than the second gens.. maybe it's just me.

The idea in my head is to raise the muffler up as I've seen done on honda tech in a thread started by vectorsolid.

I will at that point build a diffuser to Finish the belly pan at this point, the ideal boat tail length should be a lot shorter, right?


Aerohead, I saw a photo of your toyota with what seems to be a cowl induction hood. Can you explain or link me to some details on that? NVM http://ecomodder.com/forum/showthrea...-28791-20.html

That could in my mind help with drag created by wipers, which I'm not at all ready to lose for the rain gets pretty bad here in the sunshine state.

Also, at the autocross, they told me to look ahead.. included some verbiage about taping the windshield and or helmet visor?..

*On the 2nd-gen CRX they raised the back of the roof to 'slow' the curvature down.
*If raising the muffler allows you to do a 2.5-degree diffuser,that would be a good thing.
*With boat tails,the 'ideal' is always the full tail.Here is the evolution of the 'Kamm' tail.They start with the whole thing,then slice it off to an 'optimized',practical-length tail

*The blister on the T-100 reduces the angle between the 'hood' and windshield,since it's more difficult to lay the windshield back at a steeper angle.It reduces the pressure peak at the windshield header a bit.It might help with the transverse flow to the A-pillars.Don't know.Ventilation suffers a bit do to lower cowl pressure.
*I tested the cowl area at Bonneville (cardboard and duct-taped over completely)for both the CRX and the T-100.If it made any difference,it could not be measured to a 1/1,000-second or 1/1,000th-mph.My opinion is that you could spend your efforts better elsewhere on the body.

[razordave]

So, took an off ramp too briskly for the damp, dewy conditions Friday around 4am. Spoun around 360 @ 50mph and ripped my partial boat tail off :/

Did a partial grill block and have been working in my head on v1.6 for a very similar boat tail mostly just mounted better possibly in an adjustable capacity.

I also ditched the seventeens from the front in favor of the 185-65-14 I had on the other car. Left the rears alone to try for that positive rake.

Let me just say, I need my boat tail back! Lol

[aerohead]

Originally Posted by razordave

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How about a bug deflector? Would a piece of plexi mounted to my hood on the headlight plane direct the air to the roof instead of the windshield?

judging by the aero template, my plan should work, maybe a 2-3 degree angle?

You have nice attached flow in the forebody.A deflector would ruin that.And it would reduce the ability for the boundary layer to remain attached in the aft-body.
You could correct the roof,or just go straight back to the 'Template' line and then follow it as far as you dare.