How do you keep the C3 from getting light above 120mph?
08-13-2012, 05:12 PM
#122
Race Director
Thread Starter
Waiting for the results of the air pressure differential readings and your personal thoughts on the feel..... this is what i would like to do if it works well.... and its also pretty cool looking!
08-14-2012, 11:29 PM
#123
Race Director
Thread Starter
gkull went to the salt flats, this vett went over 200mph...
other than the led weights on it up front, i did notice how far the front tires are sucked in under the body.
And it looks like to me it has like 2-3" rake
other than the led weights on it up front, i did notice how far the front tires are sucked in under the body.
And it looks like to me it has like 2-3" rake
08-15-2012, 12:27 AM
#124
Tech Contributor
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Did a test and tune evening at Gingerman the other week. Car ran well, and felt great at speed. Haven't had time to mount the pressure gauge and run the lines yet, so no hard data yet.
I was encouraged by how steady the car felt at speed so I decided to carry the floorpan back further. The trans crossmember was the biggest hinderance to a flat pan, so I had to modify it.
Then some more aluminum sheet, and a couple vanes to divert some of the air away from the transmission to the smoother sides. I tried to cover the transmission, but in addition to possible cooling issues, it just wasn't eye-pleasing, so that mod is for another time. Here's a picture during progress. It would have been easier starting with a clean sheet of paper, rather than having to modify and work around all the stuff that was placed under our cars with no initial thoughts about how aero messy it is under there.
Had planned to do a trackday this week, but ran out of time. I had the front suspension apart to change the roll center and reduce the camber-gain curves, and I'm chasing a brake issue at the moment. I've got one or two track days in mind for September to do some testing (and having fun, of course).
08-15-2012, 01:37 PM
#125
Le Mans Master
Some general thoughts on underbody aero...
Assuming relatively clean airflow can be achieved and air bleeding into the area can be sufficiently controlled, the cross-section area beneath the car needs to either remain constant or increase from no further forward than the point at which you'd like to locate the most downforce (or least lift). Any reduction of area or bottlenecks in that cross-section in the direction of airflow will necessarily increase pressures at such points. Yes, airflow needs to be thought out from the nose back, but if there's something significant towards the rear of the desired balance point on which air is going to impinge that you can't effectively do anything about, best take that into account when determining the cross-sections ahead of it.
Also, airflow doesn't like sudden changes of direction, and tends to become detached from the backside of surfaces oriented away, or increasing at greater than ~7* from normal with that flow at a given point, creating turbulence. An adequate transition area ahead of any such divergence will help avoid detachment. This includes surfaces of the pan itself, barge boards and diverters, as well as diffusers.
Assuming relatively clean airflow can be achieved and air bleeding into the area can be sufficiently controlled, the cross-section area beneath the car needs to either remain constant or increase from no further forward than the point at which you'd like to locate the most downforce (or least lift). Any reduction of area or bottlenecks in that cross-section in the direction of airflow will necessarily increase pressures at such points. Yes, airflow needs to be thought out from the nose back, but if there's something significant towards the rear of the desired balance point on which air is going to impinge that you can't effectively do anything about, best take that into account when determining the cross-sections ahead of it.
Also, airflow doesn't like sudden changes of direction, and tends to become detached from the backside of surfaces oriented away, or increasing at greater than ~7* from normal with that flow at a given point, creating turbulence. An adequate transition area ahead of any such divergence will help avoid detachment. This includes surfaces of the pan itself, barge boards and diverters, as well as diffusers.
08-15-2012, 03:30 PM
#126
Melting Slicks
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08-15-2012, 04:43 PM
#127
Race Director
You could put the lead weights on the inside 
At speed I bet that lower spoiler is hitting the salt
At speed I bet that lower spoiler is hitting the salt
08-15-2012, 07:02 PM
#128
Team Owner
http://forums.corvetteforum.com/c3-t...alt-flats.html
10-02-2012, 08:05 PM
#129
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Finished adding the additional bellypan area back to the rear camber links the other week, along with the front suspension geometry change (for reduced camber gain) and higher Cf brake pad compound all around. Took the car to a couple tracks (Mid-America in Iowa and Gingerman in Michigan) the past couple weeks to see how the changes felt. The car was very comfortable and stable on the long straights, with no feeling of lift or light steering at speed. I'm convinced that the bellypan and the blocked off grills (to reduce excess air entering the engine compartment and exiting under the car) was a directionally correct move to help the high speed stability of these antiques.
On a couple side notes, I was also very happy with the new brake pads, as I was habitually braking too early at the end of the long straights due to being used to the lower grip of the previous pads. Just need a little more practice with this new compound.
The geometry change seemed to help also. A little more front grip in the corners (less understeer), and the reduced camber change under hard braking is always a plus.
On a couple side notes, I was also very happy with the new brake pads, as I was habitually braking too early at the end of the long straights due to being used to the lower grip of the previous pads. Just need a little more practice with this new compound.
The geometry change seemed to help also. A little more front grip in the corners (less understeer), and the reduced camber change under hard braking is always a plus.
10-02-2012, 09:54 PM
#131
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I blocked off all of the two outer grills with some light plastic sheets (painted black and installed behind the grillwork), and as much of the center grill as I could with aluminum sheet. The radiator still gets its air through the two factory holes just above the front spoiler. So far the engine has cooled just fine with these changes, even on some 95-98* track days. I credit most of the thermal performance to the DeWitt aluminum radiator I put in it a couple years ago. I did it mainly for front weight reduction, but the cooling capability was a very welcome plus.
book mark for tomorrow to comment...
10-03-2012, 01:10 PM
#133
Race Director
Thread Starter
Finished adding the additional bellypan area back to the rear camber links the other week, along with the front suspension geometry change (for reduced camber gain) and higher Cf brake pad compound all around. Took the car to a couple tracks (Mid-America in Iowa and Gingerman in Michigan) the past couple weeks to see how the changes felt. The car was very comfortable and stable on the long straights, with no feeling of lift or light steering at speed. I'm convinced that the bellypan and the blocked off grills (to reduce excess air entering the engine compartment and exiting under the car) was a directionally correct move to help the high speed stability of these antiques.
On a couple side notes, I was also very happy with the new brake pads, as I was habitually braking too early at the end of the long straights due to being used to the lower grip of the previous pads. Just need a little more practice with this new compound.
The geometry change seemed to help also. A little more front grip in the corners (less understeer), and the reduced camber change under hard braking is always a plus.
On a couple side notes, I was also very happy with the new brake pads, as I was habitually braking too early at the end of the long straights due to being used to the lower grip of the previous pads. Just need a little more practice with this new compound.
The geometry change seemed to help also. A little more front grip in the corners (less understeer), and the reduced camber change under hard braking is always a plus.
Thank you.
I blocked off all of the two outer grills with some light plastic sheets (painted black and installed behind the grillwork), and as much of the center grill as I could with aluminum sheet. The radiator still gets its air through the two factory holes just above the front spoiler. So far the engine has cooled just fine with these changes, even on some 95-98* track days. I credit most of the thermal performance to the DeWitt aluminum radiator I put in it a couple years ago. I did it mainly for front weight reduction, but the cooling capability was a very welcome plus.
I blocked off all of the two outer grills with some light plastic sheets (painted black and installed behind the grillwork), and as much of the center grill as I could with aluminum sheet. The radiator still gets its air through the two factory holes just above the front spoiler. So far the engine has cooled just fine with these changes, even on some 95-98* track days. I credit most of the thermal performance to the DeWitt aluminum radiator I put in it a couple years ago. I did it mainly for front weight reduction, but the cooling capability was a very welcome plus.
pictures please!!1
i fracken love your work..
10-03-2012, 09:51 PM
#134
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Thanks man.
Here's a picture while I was blocking off the grills.
I cut out a couple pieces of plastic that matched the outline of the grill opening, painted them black, and then mounted them behind the grills. Unless you get real close you can't tell they're blocked off. I like the stock look of a C3, I just don't like a lot of the inefficiencies of its design. As I mentioned earlier, I retained the factory openings under the grills to feed the radiator.
I did a somewhat similar blockoff of the center grill, but used aluminum because I had to bend the sheet in several places to fit around the obstacles behind the grille.
Regarding the bellypan, it looks a lot like the picture a couple posts back. In that previous picture the rightside pan stopped at the underfloor muffler (the glossy black item under the passenger seat). I fabricated a muffler quite a while ago and located it under there to lower the cg of the exhaust weight, place that muffler weight on the lighter rightside of the car, and also bring that weight inside the wheelbase. I recently changed back to the original location for the mufflers to allow the rightside bellypan to mirror the left side (back to the strut rods). It's my thought that I'm gaining more from the cleanup of the undercar aero than I'm losing by moving the muffler weight farther up and outside the wheelbase.
Here's a picture while I was blocking off the grills.
I cut out a couple pieces of plastic that matched the outline of the grill opening, painted them black, and then mounted them behind the grills. Unless you get real close you can't tell they're blocked off. I like the stock look of a C3, I just don't like a lot of the inefficiencies of its design. As I mentioned earlier, I retained the factory openings under the grills to feed the radiator.
I did a somewhat similar blockoff of the center grill, but used aluminum because I had to bend the sheet in several places to fit around the obstacles behind the grille.
Regarding the bellypan, it looks a lot like the picture a couple posts back. In that previous picture the rightside pan stopped at the underfloor muffler (the glossy black item under the passenger seat). I fabricated a muffler quite a while ago and located it under there to lower the cg of the exhaust weight, place that muffler weight on the lighter rightside of the car, and also bring that weight inside the wheelbase. I recently changed back to the original location for the mufflers to allow the rightside bellypan to mirror the left side (back to the strut rods). It's my thought that I'm gaining more from the cleanup of the undercar aero than I'm losing by moving the muffler weight farther up and outside the wheelbase.
10-04-2012, 02:47 PM
#135
Team Owner
R U using stock rotors and calipers with just hi-temp fluid?
10-04-2012, 02:57 PM
#136
Race Director
Thread Starter
Thanks man.
Here's a picture while I was blocking off the grills.
I cut out a couple pieces of plastic that matched the outline of the grill opening, painted them black, and then mounted them behind the grills. Unless you get real close you can't tell they're blocked off. I like the stock look of a C3, I just don't like a lot of the inefficiencies of its design. As I mentioned earlier, I retained the factory openings under the grills to feed the radiator.
I did a somewhat similar blockoff of the center grill, but used aluminum because I had to bend the sheet in several places to fit around the obstacles behind the grille.
Regarding the bellypan, it looks a lot like the picture a couple posts back. In that previous picture the rightside pan stopped at the underfloor muffler (the glossy black item under the passenger seat). I fabricated a muffler quite a while ago and located it under there to lower the cg of the exhaust weight, place that muffler weight on the lighter rightside of the car, and also bring that weight inside the wheelbase. I recently changed back to the original location for the mufflers to allow the rightside bellypan to mirror the left side (back to the strut rods). It's my thought that I'm gaining more from the cleanup of the undercar aero than I'm losing by moving the muffler weight farther up and outside the wheelbase.
Here's a picture while I was blocking off the grills.
I cut out a couple pieces of plastic that matched the outline of the grill opening, painted them black, and then mounted them behind the grills. Unless you get real close you can't tell they're blocked off. I like the stock look of a C3, I just don't like a lot of the inefficiencies of its design. As I mentioned earlier, I retained the factory openings under the grills to feed the radiator.
I did a somewhat similar blockoff of the center grill, but used aluminum because I had to bend the sheet in several places to fit around the obstacles behind the grille.
Regarding the bellypan, it looks a lot like the picture a couple posts back. In that previous picture the rightside pan stopped at the underfloor muffler (the glossy black item under the passenger seat). I fabricated a muffler quite a while ago and located it under there to lower the cg of the exhaust weight, place that muffler weight on the lighter rightside of the car, and also bring that weight inside the wheelbase. I recently changed back to the original location for the mufflers to allow the rightside bellypan to mirror the left side (back to the strut rods). It's my thought that I'm gaining more from the cleanup of the undercar aero than I'm losing by moving the muffler weight farther up and outside the wheelbase.
i would keep the front vents open. i would not think you would get much lift there, but the flow of air to the radiator on theses C3's sucks...
your belly pan... AMAZING..
i want one....did you ever to the pressure testing?
10-04-2012, 05:26 PM
#137
Burning Brakes
Front grilles all blocked off here as well... My car will NEVER overheat. Traffic, racing, or highway driving. Stock BB radiator with some ebay electric fans. There is more than enough airflow being scooped up through the bottom openings.
10-04-2012, 05:53 PM
#138
10-04-2012, 06:24 PM
#139
Race Director
Thread Starter
Not to get too off topic but...
Front grilles all blocked off here as well... My car will NEVER overheat. Traffic, racing, or highway driving. Stock BB radiator with some ebay electric fans. There is more than enough airflow being scooped up through the bottom openings.
Front grilles all blocked off here as well... My car will NEVER overheat. Traffic, racing, or highway driving. Stock BB radiator with some ebay electric fans. There is more than enough airflow being scooped up through the bottom openings.
When you can hold the loud pedal down through turn 8 at Willow Springs big track you know you have it dialed in. I have been through that turn a bazillion times with the SCCA and that was always the corner I could gain ground in a race. You need some big ones to find out though...
10-04-2012, 06:42 PM
#140
I'm still having hand sweets..... The streets of willow are fast enough.... But I really want to do more big track... But I just don't like the way she feels above 120... What I like the least is the steering wheel feel up there... I have rack and pinion, but I was wandering if anyone ever put a shock like system on ther r&p like I see on some other stock autos? It would help keep the steering more solid at high speeds????
. I am happy to report I stayed on his "ash" the whole race ...till I went off in turn 9...but "that's racing"...
p.s. I forgot to tell you I would be happy to take your car on the big track to help sort it out...
