How do you keep the C3 from getting light above 120mph?
06-02-2012, 11:17 PM
#81
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Made a little progress today with the front undertray. It's 52" wide by 48" long, and the front edge is positioned under the pacecar spoiler. I still need to make a few more clearance cuts, but it looks like there's plenty of locations to make supporting hanger brackets.
I also recently bought a differential pressure gauge, so once I get the tray installed I'm interested in running some hoses from the gauge down to the front there to make some measurements.
I also recently bought a differential pressure gauge, so once I get the tray installed I'm interested in running some hoses from the gauge down to the front there to make some measurements.
06-02-2012, 11:46 PM
#82
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Looks good! I was just under my car today thinking about the same thing! I also have a pace car type spoiler, and I was thinking about making a tray like that except I was only thinking about having it go back to the front crossmember or so. I was also thinking about making it out of fiberglass, do you think metal is needed instead? It will be interesting to see the gauge results.
Post up some pictures if you go ahead on a tray project.
06-03-2012, 12:01 AM
#83
Le Mans Master
FWIW, I'd get some readings before installation so you'll have comparative data that can tell you whether and how much improvement you've made. Also, it will require some effort to do so, but think it's worth it to take readings from as many locations as practical, since deltas will vary along most any surface area. Of course, any underbody smoothing that doesn't create lift is a good thing.
06-03-2012, 12:02 AM
#84
Race Director
Thread Starter
Made a little progress today with the front undertray. It's 52" wide by 48" long, and the front edge is positioned under the pacecar spoiler. I still need to make a few more clearance cuts, but it looks like there's plenty of locations to make supporting hanger brackets.
I also recently bought a differential pressure gauge, so once I get the tray installed I'm interested in running some hoses from the gauge down to the front there to make some measurements.
I also recently bought a differential pressure gauge, so once I get the tray installed I'm interested in running some hoses from the gauge down to the front there to make some measurements.
THAT IS NICEWhere? how much$$$?
Last edited by pauldana; 06-03-2012 at 12:04 AM.
06-03-2012, 10:43 AM
#85
Team Owner
I just made it out of aluminum because it's less uncomfortable for me to cut and weld aluminum than it is to lay-up and sand fiberglass. I've done my share of fiberglassing over the years, and I just don't enjoy the experience anymore.
Post up some pictures if you go ahead on a tray project.
Post up some pictures if you go ahead on a tray project.
06-03-2012, 02:59 PM
#86
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FWIW, I'd get some readings before installation so you'll have comparative data that can tell you whether and how much improvement you've made. Also, it will require some effort to do so, but think it's worth it to take readings from as many locations as practical, since deltas will vary along most any surface area. Of course, any underbody smoothing that doesn't create lift is a good thing.
06-03-2012, 03:42 PM
#87
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As a side note, I've always been curious how much pressure drop (and possible performace loss) my paper airfilter element causes (versus the popular aftermarket piece), so once I get this project finished I'm planning on doing some pressure differential measurements of the filter assembly.
06-11-2012, 11:21 PM
#88
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Got the tray mounted today. Here's an earlier picture taken before I got back to the hardware store to get the specific bolts I wanted.
I'd like to put some endfences on the top of it eventually, but I need to do a bit of pressure mapping of it to see where the fences need to go.
While I was getting it fitted I was thinking about brake cooling ducts in the future, but in the mean time I thought, what the heck, how about just diverting some air from under the tray outward to the wheel area. The front spoiler has always seemed like it diverts a significant amount of air to the sides of the car (creating a slight low pressure area at the outside of the front wheelwell, as evidenced by how dirty the rims get from brake pad dust), so I thought I'd just add to the cooling volume that gets sucked out of the wheelwell. The present combination of airflow and the stainless shims I have between the caliper pistons and brake pads has worked quite well for me, and this should allow a bit more cooling ability to the system.
I'd like to put some endfences on the top of it eventually, but I need to do a bit of pressure mapping of it to see where the fences need to go.
While I was getting it fitted I was thinking about brake cooling ducts in the future, but in the mean time I thought, what the heck, how about just diverting some air from under the tray outward to the wheel area. The front spoiler has always seemed like it diverts a significant amount of air to the sides of the car (creating a slight low pressure area at the outside of the front wheelwell, as evidenced by how dirty the rims get from brake pad dust), so I thought I'd just add to the cooling volume that gets sucked out of the wheelwell. The present combination of airflow and the stainless shims I have between the caliper pistons and brake pads has worked quite well for me, and this should allow a bit more cooling ability to the system.
06-12-2012, 01:11 AM
#89
Drifting
WOW !
Nice work !
I've been following along as I've had the old girl out to the Salt Flats, 137mph ( past 140 you need a roll cage ), my avatar pic.
At that speed I was glad I was only going straight, the nose lift and lack of road feeling was a bit of an attention getter.
As it is, the description of traveling over the salt is like wet asphalt, I have a list of work to do other than venting but this thread has helped a lot. I'm hoping to go again in September.
Thanks - keep up the good work,
Frank
Nice work !
I've been following along as I've had the old girl out to the Salt Flats, 137mph ( past 140 you need a roll cage ), my avatar pic.
At that speed I was glad I was only going straight, the nose lift and lack of road feeling was a bit of an attention getter.
As it is, the description of traveling over the salt is like wet asphalt, I have a list of work to do other than venting but this thread has helped a lot. I'm hoping to go again in September.
Thanks - keep up the good work,
Frank
06-12-2012, 11:32 AM
#90
Team Owner
I've been following along as I've had the old girl out to the Salt Flats, 137mph ( past 140 you need a roll cage ), my avatar pic.
At that speed I was glad I was only going straight, the nose lift and lack of road feeling was a bit of an attention getter.
As it is, the description of traveling over the salt is like wet asphalt, I have a list of work to do other than venting but this thread has helped a lot. I'm hoping to go again in September.
Thanks - keep up the good work,
Frank
At that speed I was glad I was only going straight, the nose lift and lack of road feeling was a bit of an attention getter.
As it is, the description of traveling over the salt is like wet asphalt, I have a list of work to do other than venting but this thread has helped a lot. I'm hoping to go again in September.
Thanks - keep up the good work,
Frank
Years ago I ran aluminum under the nose more as a cooling idea. Design level one was a disaster
I had my friends that make aluminum Sprint car wings help after I made a cardboard pattern. The first design level was probably like .040 or so thick.I thought that i had it all supported nice. But for you thinking people: Lets say that at 150 mph You are creating 2 PSI. (actually that is very close to measurements I have seen on race car hood scoops). Well one square foot of aluminum panel is 144 sq. inches times 2 psi = 288 pounds. Well my aluminum panel was 4 or more square feet and when I got moving down the freeway the .040 aluminum couldn't hold 1000 + pounds and blew down against the pavement with a horride scraping noise. Enough to pucker you up at 150 or so!
My advice if you seal the bottom like 69427 be very aware of how it is suported and the thickness of the aluminum. This design was fully tested to the rating of my tires.
This design was fully tested to the rating of my tires.
All frontal air went into the rad.
Last edited by gkull; 06-13-2012 at 12:02 AM.
06-12-2012, 12:05 PM
#91
Team Owner
69427 - made a wonderful flat pan. My only question is how a radiator
works. higher pressure on the front, lower pressure on the rear. The vette chin spoiler is directly below the radiator like in the 79 year model.
The GM idea was to use the spoiler to create a lower pressure behind the rad. to create flow
I made my own spoiler under the radiator
works. higher pressure on the front, lower pressure on the rear. The vette chin spoiler is directly below the radiator like in the 79 year model.
The GM idea was to use the spoiler to create a lower pressure behind the rad. to create flow
I made my own spoiler under the radiator
Last edited by gkull; 06-12-2012 at 12:54 PM.
06-12-2012, 12:47 PM
#92
Le Mans Master
George brings up some valid concerns there. Without additional out-flow area to offset panning things up, 1) will there be enough of a pressure drop behind the rad to efficiently extract hot air and 2) might a possible pressure increase in the engine compartment negate any improvement to the lift/downforce picture under the nose?
Also, as we've both mentioned, it doesn't take all that much of a PSI differential to create significant forces over an area. A mere 0.5# average differential over 10 sq.ft. is a staggering 720#'s. So, attachment points for such things need to be frequent and sturdy, and as I've pointed out before even the factory PC front dam needs added bracing for running at speed. IMOE when aero bits fail things can get very exciting in a hurry...
Also, as we've both mentioned, it doesn't take all that much of a PSI differential to create significant forces over an area. A mere 0.5# average differential over 10 sq.ft. is a staggering 720#'s. So, attachment points for such things need to be frequent and sturdy, and as I've pointed out before even the factory PC front dam needs added bracing for running at speed. IMOE when aero bits fail things can get very exciting in a hurry...
06-12-2012, 01:27 PM
#93
Team Owner
Actually the faster the car goes the less frontal opening to the radiator you need. With my bottom pan I had great cooling up to a point then at high speed when it would create an air wall behind the radiator and cooling ceased.
The fix was less frontal opening. Look at any late model car. Very few frontal opening square inches
1950, 1960, early 1970 race cars were all flat bottomed, but they all have extensive venting all over the body panels.
The fix was less frontal opening. Look at any late model car. Very few frontal opening square inches
1950, 1960, early 1970 race cars were all flat bottomed, but they all have extensive venting all over the body panels.
06-12-2012, 09:43 PM
#94
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69427 - made a wonderful flat pan. My only question is how a radiator
works. higher pressure on the front, lower pressure on the rear. The vette chin spoiler is directly below the radiator like in the 79 year model.
This undertray doesn't change anything. The air still enters the two openings under the outer grills, same as before, and enters the radiator diffuser (unchanged in shape and volume), through the radiator, and out the fan shroud. The exit area is the same, with a couple of panels to persuade more of the air to go out the louvers instead of under the car (causing lift and drag).
Two of my recent track days were 98*F (Topeka) and 95*F (MAM-Iowa), and the engine never overheated (I run a 195* thermostat). I don't expect any significant cooling issues with this setup.
The GM idea was to use the spoiler to create a lower pressure behind the rad. to create flow
I made my own spoiler under the radiator
works. higher pressure on the front, lower pressure on the rear. The vette chin spoiler is directly below the radiator like in the 79 year model.
This undertray doesn't change anything. The air still enters the two openings under the outer grills, same as before, and enters the radiator diffuser (unchanged in shape and volume), through the radiator, and out the fan shroud. The exit area is the same, with a couple of panels to persuade more of the air to go out the louvers instead of under the car (causing lift and drag).
Two of my recent track days were 98*F (Topeka) and 95*F (MAM-Iowa), and the engine never overheated (I run a 195* thermostat). I don't expect any significant cooling issues with this setup.
The GM idea was to use the spoiler to create a lower pressure behind the rad. to create flow
I made my own spoiler under the radiator
I'm using .063" (1/16") sheet. I would've liked to use thinner stuff (as it pains me to add weight to a car) but I thought I'd go with the thicker stuff until I get some pressure differential measurements. I understand the pressure x area math, but I'll be very surprised (and very happy!) if the delta pressure is more than half a psi.
06-13-2012, 12:17 AM
#95
Team Owner
The Vette front end, how much air flow????????????????? How much of a pressure differential do the radiator fins cause as speed climbs?
What kind of A-Arms are those?
06-13-2012, 12:32 AM
#97
Race Director
Thread Starter
i can not wait for the results...if there good i already ask my sons to fab me up the same aluminum type of sheet...
this is very interesting... and some amazing work and thought.....
the differential pressure gauge data is going to be interesting...i want to buy one of those!
this is very interesting... and some amazing work and thought.....
the differential pressure gauge data is going to be interesting...i want to buy one of those!
06-13-2012, 05:12 PM
#98
Team Owner
Last edited by gkull; 06-13-2012 at 05:14 PM.
06-13-2012, 11:17 PM
#100
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I saw the data read outs when they were testing some differrent style hood scopes for a Pro stock car testing. I know that they are very well designed. But it was like 1.5 psi at 120 amd 2 by 150mph and just kind of stayed there right to 200. The reasoning was that they were in 5th gear and the motor was keeping the psi from rising. The data stopped when the driver lifts at the end of the run
The Vette front end, how much air flow????????????????? Hard to say. The math is easy if you know the path of the air (but we don't). We know the speed of the car at any moment (giving us an indication of the CFM that the car is displacing), and we know the size of the front silhouette, and the undercar ground clearance. However, we can't easily quantify the percentage of air that passes through "unobstructed", and how much just ***** up under the front end like a big marshmallow, causing lift, drag, and a redirection of some of the incoming flow. So, I guess IDK. I'm just a hotrodder who's trying some things that look visually correct. Hopefully some pressure measurements will tell me if I'm on the right track (or full of crap). How much of a pressure differential do the radiator fins cause as speed climbs? My opinion, and I invite Tom DeWitt to correct me if needed, is that the fins aren't the source of the pressure differential. The volume of air contained in the space prior to the radiator develops one pressure, and the area behind the radiator has another distinct pressure. The flow resistance of the radiator (the size and spacings of the coolant tubes) determines how much air will flow through it at the pressure differential it was encountering. Kinda like Ohm's Law. The resistor doesn't determine the voltage (pressure), it just "controls" the current (flow) through it dependent upon the delta voltage (pressure) across it. That's just kinda the way I look at it.
What kind of A-Arms are those?
The Vette front end, how much air flow????????????????? Hard to say. The math is easy if you know the path of the air (but we don't). We know the speed of the car at any moment (giving us an indication of the CFM that the car is displacing), and we know the size of the front silhouette, and the undercar ground clearance. However, we can't easily quantify the percentage of air that passes through "unobstructed", and how much just ***** up under the front end like a big marshmallow, causing lift, drag, and a redirection of some of the incoming flow. So, I guess IDK. I'm just a hotrodder who's trying some things that look visually correct. Hopefully some pressure measurements will tell me if I'm on the right track (or full of crap). How much of a pressure differential do the radiator fins cause as speed climbs? My opinion, and I invite Tom DeWitt to correct me if needed, is that the fins aren't the source of the pressure differential. The volume of air contained in the space prior to the radiator develops one pressure, and the area behind the radiator has another distinct pressure. The flow resistance of the radiator (the size and spacings of the coolant tubes) determines how much air will flow through it at the pressure differential it was encountering. Kinda like Ohm's Law. The resistor doesn't determine the voltage (pressure), it just "controls" the current (flow) through it dependent upon the delta voltage (pressure) across it. That's just kinda the way I look at it.
What kind of A-Arms are those?
