Poor Man's Aero Kit -- Initial Testing
 

http://forums.pelicanparts.com/uploa...1113544738.jpg

This Wednesday, I tested my new front and side skirts, as well as my extended underbelly panel and diffuser, at Willow Springs.

I ran a total of 8 sessions in the day. At first, I used the front and side pieces, but not the diffuser. Then I added the diffuser. Finally, I removed all of the pieces for a control session.

The initial results didn't involve any kind of data logging other than lap times. At Willow Springs, lap times typically drop off in the afternoon as the track heats up. Temperatures on the track itself were between 70 and 83 degrees all day.

My first concern was with engine temps. The results surprised me. I could see no difference between 'naked' runs and ones where the under-the-engine pieces were in place. Apparently, the ventilation I added is doing its job. In normal street driving, I've been seeing Cylinder Head temps between 200 and 250 degrees. On the track, I got up to about 280-290, but the needle never made it to 300, even. And it reached the same high point with the engine cover as it did without. (Plus, the sender was calibrated with boiling water, and checked out as accurate.) My car appears to run rich, based on exhaust gas testing on the dyno. Still, I'm surprised that these readings are so low.

Engine oil temps were between 180 and 210 all day, which is normal for my car in these conditions.

With the belly plates in place , I did see elevated transaxle temperatures, even with the transaxle cooler running. At the hottest part of the day, I got a reading close to 250 degrees. If I keep using the belly pieces, I'm going to have to add some ducting to the transaxle cooler.

I also got a lot more heat in the cabin, even with the heater boxes were set in the pass-through (off) position. I assume this is because the route the heat is normally able to escape through was obstructed by the belly pieces. I also have an aluminum panel where the rear seats used to be, which was not screwed down tightly and was probably allowing a lot of the trapped heat into the cabin.

The results? At this point, I'd have to say... completely inconclusive. In the first two sessions, I ran with the front and side skirts in place, and the belly covering going back as far as the transaxle. My best time was a 1:35.59, which is about normal for the old street tires I'm currently running. I wasn't pushing the car very hard, and I'm sure I could have lined up a 1:34 without much problem.

I put the diffuser on (in addition to the front and side pieces) for the next three sessions. Track temps were slightly higher (up to 83 degrees) by this point. But my lap times were comparable. The best I did was a 1:34.95.

http://forums.pelicanparts.com/uploa...1113544718.jpg

Still, this is where things get complicated, possibly. With the diffuser in place, I could swear that I felt quite a bit of push in the car through the high-speed sweepers (one is 90-95 mph, the other 130-135 mph). So even though my times were comparable to the laps with no diffuser, the car felt different. I even spun once in turn 9 after the car pushed more than I expected on the exit and put two wheels off the left side of the track.

My conclusion on the diffuser runs? It might be that eliminating the big rear wing or extending the front lip might meaningfully improve lap times by balancing out the downforce between front and rear. In other words, it could be that the diffuser is effective, even though my lap times didn't change significantly. It could simply be that the car needs to be adjusted to take advantage of the new equipment.

Then again, it might not. I'm cautious about trusting subjective driving impressions. I'd rather see data.

Finally, I took everything off for a 'control' run.

Now, it wasn't until these two final sessions that I found someone who was going surprisingly fast on the track, and the fact that I was chasing him (former POC Chief Driving Instructor Rick White) might mean my data is even less reliable. When you've got a rabbit to chase, things tend to quicken up.

On the other hand, the wind was picking up significantly. Cars were getting blown over as much as 15 feet on the exit from turn 8.

But my times in these final sessions were the best I ran all day. I had several laps under 1:35, with a best of 1:34.48.

So, I had roughly comparable times all day, but the best came at the end, which is when the track is usually about a second slower than the morning.

My conclusions? Nothing, really. I guess I can say that I need a more precise way to test these components. Ideally, I'd come up with a way to measure downforce in both the front and rear of the car on a long straight. Strain gauges might be the best way to do this. It might also be possible to measure ride height in some other ways. I'm looking into it.

In three or four weeks, I should have my DL-1 data logger. By that time, I hope to have some sort of method in place to measure downforce with these different configurations. That will be part 2 of this testing.

(Edited at 2:18 pm on April 15th, for clarity.)

Is that oil or head temps?

Re: Poor Man's Aero Kit -- Initial Testing
 

We need more guys like you that can be objective about upgrades.

Those are cylinder head temps at the #5 plug (with the plug that's accessed from below). I'll make that clearer in the original post.

Oil temps were between 180 and 210 all day. No change in oil temps with or without the engine cover, which -- like the CHT -- surprised me.

Good to know:)

Did you try running with some tufts taped to the body or oil drops? Photographing the car on the straightaway with tufts attached or taking pictures of the oil drops after a session can be very helpful in visualizing how the air is moving around the car (or rather how the car is moving through the air).

What do you use to measure head temps with?

Yes probably you need to use some tufts taped to your car and take a video from a car behind.
9ff underbally:
http://forums.pelicanparts.com/uploa...1113600966.jpg

Jack, it's not surprising about the tranny temps and the heat in the cabin.

In the 964, they dump the heat from the exchangers out into the rear wheel wells when the heat is turned off and not entering the cabin.

In the 993, they dump it under the engine.

I think we could try to adapt the 964 heater valve to work with your car, and it should solve both the problems: heat coming in the cabin through the rear seat area, and higher trans temps with the undertray below the trans.

Question?
 

I know very little about aero for racing but I am curious. The intent of your aero package is to block air going under the car and "extract" air from under the car to create downforce!

Is the increased frontal area slowing the car down? Did it feel like the car had more grip with the package in place? Do you think the big wing more than you need? Does it slow you down.

OK, I know nothing but really like the thread.

Well jack, I am glad to see the strain gauge idea is growing on you.

Seems like a lot of hassle for the minimal, or unmeasurable, gains. All of the mods essentially are to create a low pressure area under the car (or prevent a high pressure area) and it looks like the baseline aero config you run might be good enough, particularly with the long hood and the bigass rear wing. Given that the stuff can get bent, torn and otherwise cause a black flag, I'd consider the KISS rule.

It would appear that on feel alone, the difuser works, but unless you can somehow add front downforce, it's not a good thing.

Seems to me that it will not make the car faster if it increases rear downforce on a previously balanced car.

Like Jack said, it'll probably be faster if the front downforce was increased a like amount, or the rear wing could be trimmed. Or the rear upright could be swapped for the normal 3.8 wing, reducing frontal area and drag, while the underbody and diffuser result in the same downforce that the upright had.

The rocket surgeon is on the right path, I think. If I could step down to a ducktail, but maintain as much downforce as the 3.8RS wing is giving me, it would be a net gian.

But I'd like to have better data.

Hmmm, I wonder if the real advantage of Aero pieces is to be gained when they are designed along with the body. That is to say, a "package deal"?

Hmmmmm. I would agree that if you feel your getting push, then perhaps you could reduce the rear wing and thus the drag but net out the same downforce.

Perhaps you could also use some suspension tweeks to take advantage of the changed aero stuff as well. For example, loosen the front anti-roll bar to increase front grip?

One thing I do know for sure.... you having fun!

Hmm...

more rear downforce with diffuser -> front push -> take off rear wing -> same rear downforce but less drag -> better lap times

My thoughts exactly.


BTW Jack, the ducktail may be too much of a step backwards. Unless that diffuser is damn effective. Still it would be cool to try it out.


Tspringer is also right-on about tuning the suspension. You could either stiffen the rear bar, or loosen the front to make it more neutral at high speed, which will also help reduce low-speed understeer.


I really wish I was there to help you play around with things Jack. We should do an event where I don't run my car, and we just test and tune your car.

What's this "poor man" nonsense?

For more front downforce, you should consider a splitter. There's a reason all the best dressed racecars have them.

Jack,
I don't think, in anyone's wildest dreams, you will get enough downforce from a 'duck', even with the diffuser, to balance out the push (Understeer) you reported in the high speed sections.
As was pointed out above, you either need more downforce on the front, or less on the rear at that speed. Without doing a re-design, you know how to decrease downforce at the rear, and you might decrease drag at the same time. Your rear wing adjustable, isn't it? Try reducing its angle of attack by 5 - 10 degrees. I don't think you are looking for big changes at this point. Good luck.
Les

I'd be careful trying to balance out an aero issue (high speed push) with the suspension. Since suspension changes generally affect all speed ranges, you might wind up with a car that is low speed loose and high speed neutral. You need to trim aero grip with aero changes and mechanical grip with mechanical changes -- otherwise the balance of the car will be screwed up.

If your aero package has caused you to pick up a push, add front downforce. Front downforce is generally pretty easy to find since you're dealing with clean air as it comes in contact with the car. It generally seems that improving rear end downforce (without adding a lot of drag) while working in the wake of the cabin is the more common challenge.

Why not try extending (or adding) a front splitter? Maybe something in the vein of this for example...
http://tanetane92.web.infoseek.co.jp/052951.jpg

I am getting a kick out of this, I do hope it all does work, but Jack is the guy that didn't want a front cooler because the cooler snout would ruin the early cars pure looks:confused:

Jack a wind tunnel would be nice to have when your at speed. could there be a wind measure device like used in weather station mounted on the underside of the car to measure wind speed with various combinations of diffuser and wing?.This sounds crazy but you could get real time data.

I think Jack already alluded to a possible testing solution. With a data logger, you can add some linear sensors to measure the downforce effects. I assume you would add shock sensors and try to factor the data some how to see how much load they are carrying at speed. Perhaps there's a better method, dunno.

That's exactly it, though. Driving around town, I want a nice, vintage-looking car. On the track, looks don't matter as much. BB2 was conceived of as a split-personality car.

I could spend a lot of time testing these pieces on the track, but there are so many variables. I think the better next step is to put together a way to monitor the ride height changes in front and back, and then use wool tufts and video to see where adjustments should be made.

The ride height measurement is really the key, IMO. Whether its strain gauges, slide potentiometers, sonar or laser distance measurement, I need a long stretch of flat pavement and a way to produce data my DL-1 logger will be able to process.

http://www.silverstateclassic.com/

I definitely think that is the way to go -- it'll be a lot easier to do this today with digital cameras than when the factory had guys stand out on autobahn overpasses to look at the wool tufts as the car went by.

I found this aerodynamic wind tunnel simulator if anyone is interested.
I havent tried it and have no affiliations.

http://www.kineticart.co.uk/WindStudioSimulator.asp

That is not a flow simulation program, its software for controlling and recording data from a real wind tunnel.

You can duct tape a ruler to a strut and mount a lipstick camera in your wheelwell to record how much the spring compresses. The OTC Supra boys did something like this when they were suspension tuning.

Or maybe stick a carpenters laser tape measure on the side of the fender pointing at the ground and run a camera to record it. I don't know if those things will take a reading while you're moving though.

Your work is excellent. By seeing what is on the track and what you have, it looks good. Look at Yellowbird's post-hmmm :). Question: it seems that tire selection was not optimized?

Regards,

Jack here are some pics. for the F430 underbodie and some wind tunnel pics. for the 360 CGT

http://forums.pelicanparts.com/uploa...1113764144.jpg

http://forums.pelicanparts.com/uploa...1113767748.jpg

http://forums.pelicanparts.com/uploa...1113767762.jpg

http://forums.pelicanparts.com/uploa...1113764292.jpg

http://forums.pelicanparts.com/uploa...1113764317.jpg

http://forums.pelicanparts.com/uploa...1113764350.jpg

the F430 have more downforce w/o spioler wing than the F360 GTC

Yellowbird, thanks! Some of the file names you gave the images were too long, causing the images not to display. I think I fixed them.