Internal Body Aerodynamics

[rtj]

 

[rtj]

 

[rtj]

 

[rtj]

 

[rtj]

 

[rtj]

 

[SuperBuickGuy]

plenums work really well at slowing air down (and quieting the sound of the air) - I've been considering how to do this... too be continued

 

[rtj]

Missed a couple

 

[phantomjock]

SBG - I know you love to weld and fab aluminum - but that plenum is available ready to assemble here:
https://www.fivestarbodies.com/ConfigurableProduct/VPlasticRadiatorDucts.htm

You could probably do it for less than the 180+ shipping though. It doesn't provide a laydown advantage, but does make a sealed "envelope."
After taxes are done - I hope to run some CFD of a couple of ideas - I'll post here. I know, I know, I should be working on the car!

Cheers - Jim

 

[jack]

I've been interested in doing a couple subtle aero experiments on my antique. Most of the tracks I have the opportunity to run on are short/tight enough that my peak speeds are probably only about 130 mph, so aero drag issues aren't all that important to me. I'm generally happy to put up with a bit of extra aero drag if I can get some reduced lift (or added downforce if I get lucky). I've mentioned before (somewhere) that I'd like to install some minor hardware on the cowl area to cause air to stagnate (My understanding is that this is the more correct word) right in front of the windshield. While this will certainly increase drag (but come in handy in the braking zones), the added pressure in that area should add downforce in the center of the car (on both axles hopefully), and the extra air pressure should help feed the L88 airbox and engine, slightly helping to offset the extra drag. But so far, I haven't had time to come up with a design of this "piece" that would be reasonably inconspicuous on the car.

The second item, which may not work in conjunction with the above piece (due to the effective increase in frontal area from the stagnant air mass at the front of the windshield), is a vertical strip of aluminum or Lexan at the rear of the t-tops, forming a wickerbill. While this worsens the already poor airflow over the rear of an early C3, this increased pressure/force at the wickerbill would be between the axles, and hopefully reasonably negligible in the moment arm trying to lift the front axle.

I always like data, and I've got a low pressure gauge that should be able to read these small pressure changes in the event I get a chance to try these experiments.

Mike:
if you are same gent who's seeking (on another forum) OE valve spring info for your 12363392 bowtie heads, I actually have the real specs but cannot post on that forum.

To begin with, the specs below are found within the 2006 GM Perfomance Parts catalog:
12363392 head's spring seat diameter is 1.550" (Not the spring OD)
dual valve spring is GM pn 12462970
spring OD = 1.514"
installed height 1.940"
pressure (aka seat) at 1.940" = 140 psi
solid height = 1.200"
average spring rate = 325 psi

head x390 (cousin to your x392) is virtually same head but has larger (heavier) 2.25" OD intake valve (your x392 are 2.19" OD).
Those x970 springs are OE in both 390 & 392 heads. And, those x970 springs are OE in Both ZZ454 and ZZ502 heads and both of those motors have OE Roller Cams & OE Roller Lifters. However, as you know, GM OE roller lifters have No link bars; thus are lighter than retrofit rollers with link bars.

lastly some of those leading "experts" on that other forum are FOS and are faking lots of it and have successfully snowed an army of sycophants. Not a thing wrong with contacting PAC, but I'd first ask your cam manufacturer what its spring recommendation is. No surprise the know it alls couldn't come up with any real, correct data. BTW, I note B2B hasn't posted on that other forum in about a year; is he OK? pray he is.

 

[69427]

Mike:
if you are same gent who's seeking (on another forum) OE valve spring info for your 12363392 bowtie heads, I actually have the real specs but cannot post on that forum.

To begin with, the specs below are found within the 2006 GM Perfomance Parts catalog:
12363392 head's spring seat diameter is 1.550" (Not the spring OD)
dual valve spring is GM pn 12462970
spring OD = 1.514"
installed height 1.940"
pressure (aka seat) at 1.940" = 140 psi
solid height = 1.200"
average spring rate = 325 psi

head x390 (cousin to your x392) is virtually same head but has larger (heavier) 2.25" OD intake valve (your x392 are 2.19" OD).
Those x970 springs are OE in both 390 & 392 heads. And, those x970 springs are OE in Both ZZ454 and ZZ502 heads and both of those motors have OE Roller Cams & OE Roller Lifters. However, as you know, GM OE roller lifters have No link bars; thus are lighter than retrofit rollers with link bars.

lastly some of those leading "experts" on that other forum are FOS and are faking lots of it and have successfully snowed an army of sycophants. Not a thing wrong with contacting PAC, but I'd first ask your cam manufacturer what its spring recommendation is. No surprise the know it alls couldn't come up with any real, correct data. BTW, I note B2B hasn't posted on that other forum in about a year; is he OK? pray he is.

Jack, yes, I'm that guy (gent might be a bit of a stretch ).

That is exactly the info I am looking for! If I understand things correctly, Chevrolet appears to have kept the same springs/specs from the initial introduction of those heads up through the introduction of the ZZ series of big block crate motors, which use the same cam and lifters I'm currently installing in my engine.

I haven't heard from B2B in quite some time, but I semi-regularly correspond with a mutual friend out in California. I'll inquire about B2B's welfare.

Thank you (profusely!) for this information. This issue has been stalling my effort to get the engine put together and thrown back in the car. Please do me a favor, and keep in touch. I'd like to buy you a beer or lunch sometime if the opportunity arises.

(VM guys: Please excuse the momentary topic drift here. I have been looking for the information that Jack provided and have been failing in the process. Jack's help is enabling me to get the car back together in time for this spring's events.

I now return you to your regularly scheduled topic.)

 

[phantomjock]

The "German 'Vette" a couple of posts back :


Is using flush mounted headlamps. Also note the splitter is something like SuperBuickGuy is fabricating on his fantastic2.
The radiator ducting on the splitter has some nice features including built-in brake ducts. Nice.

But, the image brings up the topic of Headlamps!

Here is an interesting video well worthy of you viewing time:

Has good coverage of the first 6 generations of the corvette and the C2 - C5 with headlamps up and down.

Cheers - Jim

 

[69427]

The "German 'Vette" a couple of posts back :
View attachment 53569

Is using flush mounted headlamps. .........................................

Cheers - Jim

I've been kicking around doing a similar thing on my car, but with removable body colored covers. I've got a set of late 80's Oldsmobile (Cutlass?) small headlights and brackets, and it's easy enough to fabricate some aluminum covers, but I haven't come up with a design yet that will look 100% stock, while also allowing the covers to be removed quickly without any tools (and won't accidentally release due to bumps or chatter on the track).

 

[BBShark]

What is a "water channel"?

 

[phantomjock]

A Water Channel/Tunnel is like a Wind Tunnel, but using water. Then, it uses an electric current to generate a bubble stream in lieu of smoke. Advantages; smaller, less power required, can reduce the size and speed of the run and still hit the same Reynolds Number (Re). This means a smaller model can represent a full size vehicle at "affordable" speeds. Here is a quick example of how speed and size in water vs air can help reduce costs:

Example(1) Air 100 mph 10' length > Re = 8672882
Example(2) Water 20 mph 1.8' length > Re = 8858375

Not an exact comparison, but should help -- I hope!

Cheers - Jim

 

[rtj]

All the splitter talk/discussion made me do a quick search. Thought this was good.

 

[rtj]

Interesting how he did this.

 

[rtj]

Lots of effort

 

[phantomjock]

86 inches wide- WOW! I'm a piker - been working at 78 inches! (But then again - it was a '78!) And I'm looking for a trailer that won't brealk the bank.

Didn't see/hear mentioned the added efficiency you can gain from adding the diffuser/tunnel on the splitters. [Maybe missed it]
These additions can add significant downforce and can help reduce overhang to limits (when needed).
If you check out their performance curves - they show the results. In fact, their splitters have very low overhang - good to have the tunnels.

Good find on the videos rtj!

SBG - Those links could be useful for your splitter if you want to forgo building those - but pricey I'd say.

Cheers - Jim

 

[rtj]

The young guy with the beard in the first splitter vid goes into the splitter diffuser. He describes it as a Venturi effect.

He keeps most of the wind tunnel data to himself.

 

[rtj]

YouTube keeps suggesting these:

 

[phantomjock]

Staying with the discussion of Tunnel/Diffusers on splitters. I've mentioned previously, that the added efficiency can result in using less surface area.
Even though RHR keeps their wind tunnel data "close," they have let out some very useful information.

Here I have used that (intel) to drive home the point:



Adding rake to the body also increases downforce for the same reasons a diffuser creates downforce. And, rake rotates the lift vector contribution from the hood slightly forward. Suggesting an ever so slight propulsive force, but there is no free lunch!

Cheers - Jim

 

[SuperBuickGuy]

86 inches wide- WOW! I'm a piker - been working at 78 inches! (But then again - it was a '78!) And I'm looking for a trailer that won't brealk the bank.

Didn't see/hear mentioned the added efficiency you can gain from adding the diffuser/tunnel on the splitters. [Maybe missed it]
These additions can add significant downforce and can help reduce overhang to limits (when needed).
If you check out their performance curves - they show the results. In fact, their splitters have very low overhang - good to have the tunnels.

Good find on the videos rtj!

SBG - Those links could be useful for your splitter if you want to forgo building those - but pricey I'd say.

Cheers - Jim

when I finalize the design of my front spoiler - I'm seriously considering sending it to be made in carbon fiber....

the other thing I'm considering is putting another air dam between the front wheels ala IROC Camaros. make it of mud-flap material so it can freely give if hit but it would comply with the rules and even help more with controlling lift.... OR
putting something similar between the rear wheels to channel air to the brakes (rather then running ducts)

 

[phantomjock]

Kinda' like this:


Here is a "prettier version:"


Add a curve - or angular section to the wheel wells? Sounds like a plan. Makes a Mix-and-Match with the splitter.

Cheers - Jim

 

[rtj]

His cad drawings:

He has the wide tires installed at 27 min.

 

[BBShark]

Did the guy explain what his objective is? Seems like if you were going to drive the car with it that low you would want to move the suspension points and also (moving the suspension) would allow you to lose those wheel spacers.

 

[rtj]

BBShark, I skipped through it pretty fast, but I kind of thought he was winging it.

His cad looked interesting, so figured l’d share the link.

C4 corvettes are the last budget corvette.

Edit:
Watching it again made me think he didn’t do the cad.

 

[rtj]

Mfain has apr on his car. I was looking at their products and saw something new, which we have discussed.

https://aprperformance.com/racing-product/gt-250-adjustable-wing-swan-neck/

 

[rtj]

 

[rtj]

The Block tribute car has much more radical aero, rules are probably minimal on PP.