1965 Corvette New Bonneville Record will be at 2025 Convention

[Michael J.]

Re: 1965 Corvette New Bonneville Record

Congrats Wayne, well done. Having driven my C6 ZR1 over 200 mph, I know how thrilling that can be, but mine was at the Texas Mile, not a place like Bonneville, now that is an accomplishment!

[Duke W.]

Re: 1965 Corvette New Bonneville Record

If i recall correctly, I thought the front end of a midyear starts to lift around 150mph

An article in Corvette News back in the sixties had a graph of power required vs. speed and lift for a '66 L-72 coupe with the F-41 suspension, and at 200 MPH there was zero weight on the front end. Above about 170 the data was extrapolated as there was no Corvette engine back then that could push a production body Corvette to 200, something on the order of 750 HP.

I had my 340 HP SWC (3.08:1 axle ratio) up to about 150 a couple of times in the sixties, and the front end was definitely lifted up and light, but it was stable. With the light front end it just wanted to go straight. The steering was light and sluggish, but it was stable.

It's important to understand that the power requirement increases with the CUBE of speed, so to go ten percent faster you need one third more power and to double speed you need eight times more power.

Fifteen years ago a friend with a '88 Fiero went to Bonneville, totally stock except for open exhaust, and did about 117 MPH. He said he wanted to do 130, and I said he needed about one-third more power. He had chassis dyno data so we spent an afternoon with Engine Analyser working out mods necessary to achieve the required power. He was an excellent fabricator and did all the mods, which included massaging the heads, cutting down and welding up the OE long runner OE manifold to short runner with a big plenum, retarding the OE cam four degrees and fabricating a tuned header exhaust system.

A chassis dyno test showed that the top end power objective was met, but it was a dog down low. The Bonneville weather gods were good to him on the day of his two-way run, decent density altitude and little wind giving him a two way average a little over 131. The record for his class was a 308 Ferrari at about 150, but he was happy to have what we figured was the world's fastest Fiero.

Back in '65 there was a fella who ran a '65 396 at Bonneville and I think he might have set a record for his class, A/GT at about 170. It was written up in Corvette News, and I recall his name was Barry Bock.

Duke

[Gary B.]

Re: 1965 Corvette New Bonneville Record

I'm surprised he wasn't airborne at that speed...
If i recall correctly, I thought the front end of a midyear starts to lift around 150mph

He was 52% above that ! and 2% faster than the old record...
Salt or not, that probably contributes to wobbly steering...

Looks like he was at 7,500 RPM when he pulled the chute...

What a RUSH !

Mark,

Wayne told me the previous record for his class, which is B/MGT, was 202.xxx mph, so Wayne beat the previous record by >10%. A big jump!

Gary

[Jack M.]

Re: 1965 Corvette New Bonneville Record

AMAZING ride... IMPRESSIVE accomplishment... CONGRATS!

[David R.]

Re: 1965 Corvette New Bonneville Record

Congratulations and Well Done!!

[Ed H.]

Re: 1965 Corvette New Bonneville Record

In the Golden state we call that bitchen OMG RIDE 😲

[Ed H.]

Re: 1965 Corvette New Bonneville Record

Did you have change your DEPENDS?

[Mark F.]

Re: 1965 Corvette New Bonneville Record

That class also allows for a full belly pan (which I have now). We went from 500+ lbs. of lift (at 200 mph), to ~400+ lbs. of downforce at that speed...-Wayne

An article in Corvette News back in the sixties had a graph of power required vs. speed and lift for a '66 L-72 coupe with the F-41 suspension, and at 200 MPH there was zero weight on the front end. Above about 170 the data was extrapolated as there was no Corvette engine back then that could push a production body Corvette to 200, something on the order of 750 HP.

It's important to understand that the power requirement increases with the CUBE of speed, so to go ten percent faster you need one third more power and to double speed you need eight times more power. Duke

Wayne and Duke,

So, does the belly pan equate to what Jim Hall introduced as "Ground Effects" in the early '60s ?
And if so, does ground effects cause you to need more power to increase speed ? - or does it help to reduce those power requirements ?

As for the math on fluid flow, I seem to remember being taught "double the velocity and you quadruple the force" (think trying to wade across a creek at normal flow vs storm-elevated flow). I think that's the same as what you're saying Duke. 2³ = 2x2x2 = 8.

F=ma, but I'm not remembering my physics enough right now to translate how acceleration (velocity squared V²) equates with mass and force (horsepower of the engine ?)

[Duke W.]

Re: 1965 Corvette New Bonneville Record

Wayne and Duke,

So, does the belly pan equate to what Jim Hall introduced as "Ground Effects" in the early '60s ?
And if so, does ground effects cause you to need more power to increase speed ? - or does it help to reduce those power requirements ?

As for the math on fluid flow, I seem to remember being taught "double the velocity and you quadruple the force" (think trying to wade across a creek at normal flow vs storm-elevated flow). I think that's the same as what you're saying Duke. 2³ = 2x2x2 = 8.

F=ma, but I'm not remembering my physics enough right now to translate how acceleration (velocity squared V²) equates with mass and force (horsepower of the engine ?)

Ground effects cars have what is in effect a venturi under the car, but instead of a round cross section like a carburetor the cross section is an approximate low aspect ratio rectangle. As the air speeds up under the car, pressure is reduced (Bernoulli's equation), creating downforce and then it exits via a diffuser that slows the air down and raises the pressure back to ambient. You can see these diffusers on current Weathertech series sports cars like the C8.R.

A flat belly pan may not add downforce, but it reduces drag due to the smooth surface compared to the "mess" under a typical car, and a front air dam will divert air up and over the car or too the side so less has to traverse the "slot" between the ground and vehicle underside, which reduces both lift and induced drag due to lift.

Power dissipated by a wheel driven land vehicle at constant speed is equal to tractive effort (force at the contact patch, which is equal to total drag) times velocity. Drag forces consist of aerodynamic drag that increases with the square of speed, rolling resistance that increases linearly with speed, plus a small fixed force required to get the vehicle initially rolling, which is negligible for a car, but can be significant for a 15,000 ton coal train.

So with the above knowledge we can say:

Horsepower = Fv = (av**2 + bv+ c)v = aV**3 + bV**2 + c

The dominant term is cubic, which is where doubling top speed requires 8 times the horsepower or increasing top speed 10 percent requires about 1/3 more power comes from.

Power is energy per unit time and if we use pounds force for force and velocity in ft/sec the power is expressed as ft-lbf/sec. Divide this by James Watt's definition of one horsepower, 550 ft-lb/sec, and you have the horsepower power required to overcome the drag force at any speed.

For an average modern car aero drag about equals rolling resistance at 40-45 MPH then rapidly exceeds rolling resistance above this speed. Rolling resistance can be a big issue at Bonneville because if the salt is soft, drag force will be considerably more than a hard surface like concrete or asphalt, and a rough surface increases rolling resistance, too in addition to possibly making the car difficult to control.

Bonneville engines are the easiest to system engineer because you design only for top end power. Other considerations like low end torque/power and idle behavior for a road engine or average power over the top 10 to 30 percent (depends on gear spacing) of the rev range on a road racing engine are not important. Then once you know power and have some idea of the car's drag, you gear so that the engine will just rev to the power peak in top gear.

Duke

[Wayne Y.]

[Wayne Y.]

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[Ed H.]

Re: 1965 Corvette New Bonneville Record

Copy that, your the real deal, a warrior.

[Duke W.]

Re: 1965 Corvette New Bonneville Record

Tell us more about this A2 wind tunnel like where it's located and how long it's been around.

Did you get enough data to compute the drag coefficient (both OE and modified bodywork), and how did you compute frontal area?

Back in the day Road & Track listed frontal area in their road test data, but the value was just computed as 80 percent of the overall width times height.

Also, do you have a photo for the car up on a lift so we can see the belly pan?

Duke

[Wayne Y.]

Re: 1965 Corvette New Bonneville Record

The A2 Wind Tunnel is in the heart of NASCAR-land (Mooresville, NC). I WISH we had done a wind tunnel baseline with the '65 Corvette in its bone-stock configuration, but we didn't. And, from the beginning, I knew the front-end of a C2 Corvette wasn't very aero and was going to cause me some lift. So, right from the start (early 2023), we fabricated a smaller front air dam for the car (even though we were running it in the GT class, which didn't allow it). All that meant was: if I had set a record in 2023, it wouldn't have held up or passed inspection. But, my goal in 2023 was to get familiar with the car and I didn't want it to take off like an airplane. In 2023, I got the car just over 170 mph (at the 1 1/3 mile El Mirage dry lakebed course in S. California), but it was a real handful and was clearly getting lift on both the front and rear. So, during the off-season (early 2024), we decided to move to the modified GT (MGT) class. That way we could legally add a full-blown front air dam, rear spoiler & belly pan.


From what I understand, GM didn't have a wind tunnel in 1965. I believe their Aerodynamics Laboratory in Warren, MI was built in 1980. Prior to that, they leased time from Lockheed's wind tunnel in Georgia. Not to say aero was an afterthought, but I'm guessing the 'body design look' was probably more of a priority (and I LOVE the C2 body design - so I think they nailed it). They also probably weren't thinking some bozo, like me, would attempt to go 220+ in a C2. ; )


My aero engineer works for T.G.S. (The Garage Shop) in North Carolina and he has a lot of NASCAR experience. Regarding some of the more technical aspects of the wind tunnel testing we did, I asked him to provide some details surrounding drag coefficients and frontal area. Here's his response...


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Our goals for the wind tunnel were:

1. Quantify the aero properties of the GT configuration Vette in a repeatable way.
2. Make changes within the rules for the MGT class to reduce aero drag and reduce aero lift

In the tunnel one measures the forces on the vehicle (airplane, motorcycle, bobsled, bicycle, etc.) to calculate the aero coefficients Cn. Also measured in the tunnel is the airspeed V, and the air density Rho.

The basic equation is:



Fn=Force of the n dimension (where n can be drag, lift, front lift, rear lift, side force, etc.)
Rho=air density
A=frontal area
V=freestream air velocity

As mentioned earlier, the tunnel measures Fn, Rho, and V, so by rearranging the equation with measured properties on one side we get:

A*Cn = 2*Fn/(Rho*V^2)



When I built our simulation, I just use the same A term I chose for the tunnel results along with the Cn for the body configuration, the Rho measured on the day at the track, and the speed V we ran, from those factors I can calculate Fn which relates back to the forces that were measured at the tunnel in the first place.


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As a former tech. ceo, I learned a long time ago to surround myself with smart people. He's just one of the guys who played a huge role in getting my 1965 Corvette to run at these speeds. It's been a huge team effort. And, as you can imagine, we have a lot of "dials" that we can turn/adjust (suspension/coil overs, carb. jetting & timing tweaks for various density altitudes, rear spoiler angle, wicker height, etc. etc.). And those things all change based on whether we're running a 5 mile course at Bonneville vs. a 1 1/3 mile course at El Mirage. My next events are all at the El Mirage dry lakebed (9/15/24, 10/20/24 & 11/9/24).


I don't actually have any belly pan pics. BTW, my plan is to bring the car to the Las Vegas National next year. I'd love to go after an NCRS Concours (Modified Division) 427 ribbon! Plus, it'll be a kick to fire it up for Ops judging!


-Wayne

[Jack M.]

Re: 1965 Corvette New Bonneville Record

These photos may illustrate the 'extensive' wind tunnel facility GM had for the development of the C2:

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