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How do you keep the C3 from getting light above 120mph?

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How do you keep the C3 from getting light above 120mph?

 
Old 04-24-2012, 03:58 PM
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pauldana
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Default How do you keep the C3 from getting light above 120mph?

Well that's the question... I have the following mods for suspention but above 120 I can still feel her starting to get light, and at arond 160 it's just not good.... So here are the mods:

I am between 3-4" off the ground from frame or exhaust. #550 front springs cut 1/2 coil, bilstine sport shocks, #360 rear carbon fibor spring, spreader bar, tires and wheels rated for such speeds... Large front and rear sway bars, rack and pinion...so for just suspention that is what I have.

I think I'm not letting enough air escape from under the hood,,,, I saw Beejay install hood vents, so I think that that will be my next mod.... Any other ideas? Thx

Last edited by pauldana; 03-12-2013 at 06:05 PM.
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Old 04-24-2012, 04:19 PM
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front chin spoiler rear wing, ricer style, ugly but work
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Old 04-24-2012, 04:27 PM
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Do you have the pace car front spoiler? Look into keeping as much air out from underneath the car as possible. I have a custom splitter that is 3" off the ground which I think helps immensely at high speed.
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Old 04-24-2012, 04:28 PM
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Originally Posted by pauldana View Post
Well that's the question... I have the following mods for suspention but above 120 I can still feel her starting to get light, and at arond 160 it's just not good.... So here are the mods:

I am between 3-4" off the ground from frame or exhaust. #550 front springs cut 1/2 coil, bilstine sport shocks, #360 rear carbon fibor spring, spreader bar, tires and wheels rated for such speeds... Large front and rear sway bars, rack and pinion...so for just suspention that is what I have.

I think I'm not letting enough air escape from under the hood,,,, I saw Beejay install hood vents, so I think that that will be my next mod.... Any other ideas? Thx
Where did you get the carbon fiber spring?
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Old 04-24-2012, 04:43 PM
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Old 04-24-2012, 04:52 PM
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alignment both front and rear set for high speed track?

http://www.vbandp.com/View-document-...ent-Specs.html

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Old 04-24-2012, 04:56 PM
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Originally Posted by oldalaskaman View Post
front chin spoiler rear wing, ricer style, ugly but work
I have he front stock air dam and the stick rear spoiler

Originally Posted by vette427-sbc View Post
Do you have the pace car front spoiler? Look into keeping as much air out from underneath the car as possible. I have a custom splitter that is 3" off the ground which I think helps immensely at high speed.
Yes again... Stock front air dam

Got a pic of your custom splitter? What speed have you had it to? Any difference? I can't go much lower with out hitting small stOnes in the road!!!

Originally Posted by Kid Vette View Post
Where did you get the carbon fiber spring?
Sorry, my bad.... Fiberglass trw 360 spring
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Old 04-24-2012, 06:38 PM
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Originally Posted by pauldana View Post
Yes again... Stock front air dam

Got a pic of your custom splitter? What speed have you had it to? Any difference? I can't go much lower with out hitting small stOnes in the road!!!
Ive hit 130 on the road course (no more gear left) But I can say there is a big difference compared to nothing.
Look at BeeJays custom Pace car spoiler. I would say his looks the best and is probably the most functional.
Here is mine... The aluminum support rods are "consumables" but the fiberglass will flex enough if you scrape a driveway. The only reason I have scraped my splitter/bent a support rod is because I was forced to enter a driveway at a less than optimal approach angle or I wasnt paying attention and hit a HUGE pot hole. Most speedbumps are no taller than 3" and if they are, they are the speed "humps" that span a further distance so I still wont scrape.
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Old 04-24-2012, 07:01 PM
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Might want to post in the racing section as well
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Old 04-24-2012, 07:04 PM
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Your wheel alignment, tires, and all wheel bearings and suspensinon components need to be absolutely spot on perfect.
Then you might begin to look at aero mods.
Remember the C3 was not designed to a low drag coefficient. It was designed to "look cool''. (And, we might all agree, succeeded). I believe the early C3's had a Cd of something like .5. The '80 to '82 cars were slightly better, like .45. Whereas a C5 or C6 has a Cd of perhaps .3 or even slightly less. So the new cars are about 40% better, as far as aero drag is concerned..
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Old 04-24-2012, 07:12 PM
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Old 04-24-2012, 07:34 PM
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When I had a stock 79 nose I added 3-4 inches to the front chin spooler just using 6 inch wide black rubber floor molding from the hardware store like Home Depot I drilled holes and used big rivots, but anyway bolts and large washers would work. I had 550 front springs and used 255/45/17 front tires which are 25.7 or so diameter. The extra chin make more vacuum under the car at speed.

The second thing is rake. Measure each rear center of the fender well hieght. then crank on the rear spring end bolts lifting the rear in 1/2 inch increments and test how stable it is. The higher rear points the nose down and makes for more front downforce

One problem about our c-3's is that the steering is tooooooo fast. you need higher ratios for higher speed.

Last edited by gkull; 04-24-2012 at 07:37 PM.
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Old 04-24-2012, 08:18 PM
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You lose 10 lbs. and then figure out where to mount 24 lbs. of sand in the front.

Just kidding. 120mph? Fast enough.
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Old 04-24-2012, 10:11 PM
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There has been lots of discussion on this. Do a search on this forum using "aero".

This will get you started. Look at post #5 in particular.
http://forums.corvetteforum.com/c3-t...ics-et-al.html

Last edited by 3JsVette; 04-24-2012 at 11:40 PM.
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Old 04-24-2012, 10:20 PM
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Paul. You driving that thing up to 160mph? Please be careful. PS, How is the A/C? mike...
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Old 04-24-2012, 11:22 PM
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Having downforce rather than lift is all about having more air pressure above than below the body, and there are some fairly straight forward steps that can get you closer to being on the right side of that equation. FWIW, it doesn't take much to make a significant difference, as only 0.1 PSI Δ (differential) on 20 sq.ft. yields 288# of lift or downforce.

1) For pre-'80 bodywork, adding a functional front dam and rear spoiler helps a lot, and the Pace Car kit actually works, but IMOE the dam needs bracing and/or a splitter for very much high speed running.

2) Lower ride heights (assuming you're not already at or near Power Book recommendations). Agree with George about ~1/2" rake, but keep in mind it's not something you want to take too far.

3) Properly sealed hood, CAI or not. At speed there is a high pressure area at the base of the windshield which you don't want bleeding under the rear of the hood into the engine compartment.

There is, of course, more that can be done, but I wouldn't worry about things such as fenderwell vents, diffusers, belly pans, wings, dive plates or undercarriage streamlining until and unless the above doesn't suffice. These guys apparently weren't satisfied with only doing the basics...



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Old 04-25-2012, 12:26 AM
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Originally Posted by MelWff View Post
alignment both front and rear set for high speed track?

http://www.vbandp.com/View-document-...ent-Specs.html
i am aligned per VB&P...been doing that for several years... thx!!

Originally Posted by billla View Post
Might want to post in the racing section as well
Most all those guys are now C5&6's..... they never see me coming!!

Originally Posted by vette427-sbc View Post
Ive hit 130 on the road course (no more gear left) But I can say there is a big difference compared to nothing.
Look at BeeJays custom Pace car spoiler. I would say his looks the best and is probably the most functional.
Here is mine... The aluminum support rods are "consumables" but the fiberglass will flex enough if you scrape a driveway. The only reason I have scraped my splitter/bent a support rod is because I was forced to enter a driveway at a less than optimal approach angle or I wasnt paying attention and hit a HUGE pot hole. Most speedbumps are no taller than 3" and if they are, they are the speed "humps" that span a further distance so I still wont scrape.
Yea....im thinking a lot better spoiler now than the 78 pace car one..... thats a spoiler.... but mine will have to be pretty also

Originally Posted by gcusmano74 View Post
1. Your wheel alignment, tires, and all wheel bearings and suspensinon components need to be absolutely spot on perfect.
Then you might begin to look at aero mods.
2. Remember the C3 was not designed to a low drag coefficient. It was designed to "look cool''. (And, we might all agree, succeeded). I believe the early C3's had a Cd of something like .5. The '80 to '82 cars were slightly better, like .45. Whereas a C5 or C6 has a Cd of perhaps .3 or even slightly less. So the new cars are about 40% better, as far as aero drag is concerned..

Originally Posted by U17 View Post
1. They are
2. part of my problem now

Originally Posted by gkull View Post
1. When I had a stock 79 nose I added 3-4 inches to the front chin spooler just using 6 inch wide black rubber floor molding from the hardware store like Home Depot I drilled holes and used big rivots, but anyway bolts and large washers would work. I had 550 front springs and used 255/45/17 front tires which are 25.7 or so diameter. The extra chin make more vacuum under the car at speed.

2. The second thing is rake. Measure each rear center of the fender well hieght. then crank on the rear spring end bolts lifting the rear in 1/2 inch increments and test how stable it is. The higher rear points the nose down and makes for more front downforce

3. One problem about our c-3's is that the steering is tooooooo fast. you need higher ratios for higher speed.
1. back to that front spoiler....need to figure out how to make a good, and cosmetically appealing spoiler.
2. 550 here also cut 1/2 coil. front 245/45zr18 rear 275/40zr18 my front wheel well hight is 26 1/2" front, 27 1/4" back
3. i have rack and pinion, but yes, much to twitchy still

Originally Posted by Larry82 View Post
You lose 10 lbs. and then figure out where to mount 24 lbs. of sand in the front.

Just kidding. 120mph? Fast enough.
wife want me to loose 10# anyway!

Been racing Willow springs small track, and on the straight away im hitting a brief speed of 110+ before into hard breaking. I going to be more on the big track now, and the speeds are much greater.

Originally Posted by 3JsVette View Post
There has been lots of discussion on this. Do a search on this forum using "aero".

This will get you started. Look at post #5 in particular.
http://forums.corvetteforum.com/c3-t...ics-et-al.html
thx

Originally Posted by mds3013 View Post
Paul. You driving that thing up to 160mph? Please be careful. PS, How is the A/C? mike...
Originally Posted by TheSkunkWorks View Post
Having downforce rather than lift is all about having more air pressure above than below the body, and there are some fairly straight forward steps that can get you closer to being on the right side of that equation. FWIW, it doesn't take much to make a significant difference, as only 0.1 PSI Δ (differential) on 20 sq.ft. yields 288# of lift or downforce.

1) For pre-'80 bodywork, adding a functional front dam and rear spoiler helps a lot, and the Pace Car kit actually works, but IMOE the dam needs bracing and/or a splitter for very much high speed running.

2) Lower ride heights (assuming you're not already at or near Power Book recommendations). Agree with George about ~1/2" rake, but keep in mind it's not something you want to take too far.

3) Properly sealed hood, CAI or not. At speed there is a high pressure area at the base of the windshield which you don't want bleeding under the rear of the hood into the engine compartment.

There is, of course, more that can be done, but I wouldn't worry about things such as fenderwell vents, diffusers, belly pans, wings, dive plates or undercarriage streamlining until and unless the above doesn't suffice. These guys apparently weren't satisfied with only doing the basics...



first of all..... WOW... cool vette!!

AC needs 1 more can of freon, but it is working now, thank you again!!!!

my frame crossmember is at ~3".... cant go much lower.

Sealed hood??????? really?????? i was thinking of venting it!! ...... im confused... i want to release the pressure build up dont i??
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Old 04-25-2012, 12:36 AM
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Venting my hood made a huge difference in front end feel and steering responsiveness at ultra high speeds. Venting the hood also helped drop the radiator temps too. I have a 170 degree thermostat and I rarely get up to that temp. Also, I made a splitter that seems pretty effective. I made it out of plywood, but I need to find another material.
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Last edited by Bee Jay; 04-25-2012 at 01:10 AM.
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Old 04-25-2012, 12:36 AM
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amen on the 'WOW' cool vette
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Old 04-25-2012, 12:56 AM
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Pressures differentials from above to beneath the hood vary, and you want to make sure you don't open anything up where pressure above is greater than that directly beneath any specific location. So it depends on where you intend to vent as to whether or not it would prove beneficial. Other than for isolated CAI, I'd look elsewhere than at the cowl just ahead of the windshield. Besides, in city traffic the lack of a rear hood seal invites hot engine compartment air into the cabin.

FWIW, tho I've studied up on this stuff a bit, I don't have a sheepskin in the subject, but if I can ever afford to get my shark back in service I do have instrumentation on hand with which to gather supportive data. (Donations to the cause graciously accepted. )

Last edited by TheSkunkWorks; 04-25-2012 at 12:58 AM.
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