[Stan Weiss]

Originally Posted by Tom Vaught

You could get Jeff and Jack to give you an approximation on the Frontal Area,
Stan using Equation #2:

AF= (H-GC) W*0.93
where: H is the vehicle height
GC is the ground clearance
W is the width.

Better than nothing if they could "rough measure" the car.

Then do a "sweep" on Cd from .46 to .55


Tom V.

Tom,
While a production car is fairly level, a race race has more of a wedge shape to it. With a much greater ground clearance in the back than the front. Where do they measure ground clearance and how well will that work with this formula?

Stan

PS - This thread that I have been spending sometime posting in and maybe of interest to some of you.
dynamic compression for the street.
http://www.yellowbullet.com/forum/sh...1#post16089354

[Tom Vaught]

Originally Posted by Stan Weiss

Tom,
While a production car is fairly level, a race race has more of a wedge shape to it. With a much greater ground clearance in the back than the front. Where do they measure ground clearance and how well will that work with this formula?

Stan

PS - This thread that I have been spending sometime posting in and maybe of interest to some of you.
dynamic compression for the street.
http://www.yellowbullet.com/forum/sh...1#post16089354

Good question.

1) You would like to keep the air out of the underneath of the car. Not having the air bang around on all of the suspension components and drive line stuff. The only way to do that is to minimize the air that gets under the car.

2) Air also can get under the car from the wheel openings. Most good front air dams keep the air from entering the wheel houses from the side.

3) So now if you limit the amount of air coming thru the grill to the minimum required for cooling (more road race vs drag race) you can reduce the air flow under the car quite a bit.

4) Air, by the time it gets to the rear edge of the door is starting to get dirty so having small deflectors at the front of the rear wheel openings might help on a street car or car with a very shallow tire/wheel depth. A Drag car has the tire sunk into the body pretty well so minimal rear tire impact contacting the air from the sides really.

5) Transitions from things like the windshield or doors to the body can make a difference in how smooth the car is going thru the air.

So after saying all of that, if the rear of the car has more of a rake vs the front then, yes, so dirty air can eventually get under the car but the big deal is not allowing the air to get under the front of the car.

Where does the cooling air from the radiator go, typically under the car, unless you have a Trans Am type side extractor set-up (which actually worked pretty well). Less air getting into the engine compartment, less air banging around on the firewall trying to act like a parachute that slows the car down.

So the front of the vehicle is where the measurements need to be taken. Measure at the lowest point of the spoiler to the ground (if it has one). You can document the rake angle, (which we do) but the effect is minimal in normal testing. I built screw jackers to raise and the rear of the vehicle quickly, when it went into the wind tunnel. 4" difference in high rake vs low rake showed an effect but a small one vs the front height change of the vehicle.

So a) measure from the spoiler to the ground and that area you subtract from the area calculated in the measurement from the ground to the top of the windshield. Also add the tire frontal area (footprint of the tire when looking at the tire at the spoiler height). Then do the math in the formula.


Hope that helps with your question.

Tom V.

[Stan Weiss]

Originally Posted by Tom Vaught

Good question.

1) You would like to keep the air out of the underneath of the car. Not having the air bang around on all of the suspension components and drive line stuff. The only way to do that is to minimize the air that gets under the car.

2) Air also can get under the car from the wheel openings. Most good front air dams keep the air from entering the wheel houses from the side.

3) So now if you limit the amount of air coming thru the grill to the minimum required for cooling (more road race vs drag race) you can reduce the air flow under the car quite a bit.

4) Air, by the time it gets to the rear edge of the door is starting to get dirty so having small deflectors at the front of the rear wheel openings might help on a street car or car with a very shallow tire/wheel depth. A Drag car has the tire sunk into the body pretty well so minimal rear tire impact contacting the air from the sides really.

5) Transitions from things like the windshield or doors to the body can make a difference in how smooth the car is going thru the air.

So after saying all of that, if the rear of the car has more of a rake vs the front then, yes, so dirty air can eventually get under the car but the big deal is not allowing the air to get under the front of the car.

Where does the cooling air from the radiator go, typically under the car, unless you have a Trans Am type side extractor set-up (which actually worked pretty well). Less air getting into the engine compartment, less air banging around on the firewall trying to act like a parachute that slows the car down.

So the front of the vehicle is where the measurements need to be taken. Measure at the lowest point of the spoiler to the ground (if it has one). You can document the rake angle, (which we do) but the effect is minimal in normal testing. I built screw jackers to raise and the rear of the vehicle quickly, when it went into the wind tunnel. 4" difference in high rake vs low rake showed an effect but a small one vs the front height change of the vehicle.

So a) measure from the spoiler to the ground and that area you subtract from the area calculated in the measurement from the ground to the top of the windshield. Also add the tire frontal area (footprint of the tire when looking at the tire at the spoiler height). Then do the math in the formula.


Hope that helps with your question.

Tom V.

Tom,
Thanks.
As an aside. I see people try to save weight by not running inter front fender wells. How much of a negative effect would this have?

Stan

[mike leech]

Originally Posted by Tom Vaught

Good question.

1) You would like to keep the air out of the underneath of the car. Not having the air bang around on all of the suspension components and drive line stuff. The only way to do that is to minimize the air that gets under the car.

2) Air also can get under the car from the wheel openings. Most good front air dams keep the air from entering the wheel houses from the side.

3) So now if you limit the amount of air coming thru the grill to the minimum required for cooling (more road race vs drag race) you can reduce the air flow under the car quite a bit.

4) Air, by the time it gets to the rear edge of the door is starting to get dirty so having small deflectors at the front of the rear wheel openings might help on a street car or car with a very shallow tire/wheel depth. A Drag car has the tire sunk into the body pretty well so minimal rear tire impact contacting the air from the sides really.

5) Transitions from things like the windshield or doors to the body can make a difference in how smooth the car is going thru the air.

So after saying all of that, if the rear of the car has more of a rake vs the front then, yes, so dirty air can eventually get under the car but the big deal is not allowing the air to get under the front of the car.

Where does the cooling air from the radiator go, typically under the car, unless you have a Trans Am type side extractor set-up (which actually worked pretty well). Less air getting into the engine compartment, less air banging around on the firewall trying to act like a parachute that slows the car down.

So the front of the vehicle is where the measurements need to be taken. Measure at the lowest point of the spoiler to the ground (if it has one). You can document the rake angle, (which we do) but the effect is minimal in normal testing. I built screw jackers to raise and the rear of the vehicle quickly, when it went into the wind tunnel. 4" difference in high rake vs low rake showed an effect but a small one vs the front height change of the vehicle.

So a) measure from the spoiler to the ground and that area you subtract from the area calculated in the measurement from the ground to the top of the windshield. Also add the tire frontal area (footprint of the tire when looking at the tire at the spoiler height). Then do the math in the formula.


Hope that helps with your question.

Tom V.

I know for a fact that removing the factory wheel wells from a early camaro/firebird will cause a low 12 car to lose 2 mph. et was about the same, a touch slower. air hitting the fire wall is a bad deal and care should be taken to limit introduction as well as relieving any built up pressure under the hood. these would have an effect on how the car moves through the air as well

[mike leech]

Originally Posted by Stan Weiss

Tom,
Thanks.
As an aside. I see people try to save weight by not running inter front fender wells. How much of a negative effect would this have?

Stan

I would have addressed you as well in my last post had i noticed this post first.

[Tom Vaught]

Originally Posted by Stan Weiss

Tom, Thanks.
As an aside. I see people try to save weight by not running inter front fender wells. How much of a negative effect would this have?

Stan

[/QUOTE]

Originally Posted by mike leech

I know for a fact that removing the factory wheel wells from a early camaro/firebird will cause a low 12 car to lose 2 mph. et was about the same, a touch slower. air hitting the fire wall is a bad deal and care should be taken to limit introduction as well as relieving any built up pressure under the hood. these would have an effect on how the car moves through the air as well

Real world info (from Mike) that mirrors the testing we did in the wind tunnel. Only issue is that you need SOME leakage airflow to carry away the heat from the engine compartment on a production vehicle or the components will get too hot to survive for 150.000 miles. Removing the inner fender wells completely normally will allow more air to be in the compartment with the air now trying to figure out how to get out vs giving it a controlled escape path.
Belly Pans, sealed fender wells, etc can cause the underhood temps to skyrocket.

Tom V.

[60man]

Ok....since air in engine compartment is brought up I'll ask the Engineers..

My 69 GP sits low to ground and has no inner wheel wells in it. My old 60 would trap air and create some problems...hood pulling/popping up and car moving around from 1,000' on(light in front)...at times.That was at 135-138 MPH...
It had full sheet metal inner panels...I closed of grille off with Plexiglas and it relieved the situation. I haven't had any issues with the GP but have not made any full passes yet. Thinking of adding some small plastic sheets at lower rear of front fender opening...ala funny car style to keep air off firewall...possibly add a air damn if needed..
I think(?) this car will be capable of 150-155+ passes..don't want funny things to happen..
Any thoughts..
Sorry if this is off topic..

[Tom Vaught]

The picture of your 69 GP shows a very small grill opening on the same plane as the headlights. That is good.

Can you post a better picture of the area below the bumpers as the picture is really dark in that area.

First guess would be to put a spoiler on the front of the car that would divert air around the front of the car when the car is at normal track acceleration attitude.

It might be real close to the ground when sitting but a bit higher when going down the track. Deal is to not make it so low you damage it after a wheels up launch if it comes down hard due to an aborted run.

More pics please.

Tom V.

[60man]

Originally Posted by Tom Vaught

The picture of your 69 GP shows a very small grill opening on the same plane as the headlights. That is good.

Can you post a better picture of the area below the bumpers as the picture is really dark in that area.

First guess would be to put a spoiler on the front of the car that would divert air around the front of the car when the car is at normal track acceleration attitude.

It might be real close to the ground when sitting but a bit higher when going down the track. Deal is to not make it so low you damage it after a wheels up launch if it comes down hard due to an aborted run.

More pics please.

Tom V.

I'll have to take a picture Tom....I don't seem to have one of front at ride height...or with more light.
Get some tomorrow....Plus I'm not sure of front attitude going down track....just yet..
Want to check and see if Monte spoilers will work...and available??
Thanks

[60man]

Originally Posted by mike leech

To my knowledge the first set run fell short of at least 4 na engines with other heads. I think 840hp. But there may have been another engine ran sooner than franks that I don't know of. But yes in capable hands they pretty much shot out of the gate. And you may have meant your first attempt with them....

I assume this about Tigers Mike..and HP..
Jack Gaydosh dynoed his Tiger headed IAII (535 I think) before he tore it down to freshen up at seasons end...on 12-30-2006...with many passes on it..I couldn't figure out how to post the D sheet ..it can be searched on here.
It made1107 HP @ 7,200
854 ft lb @ 6,600

Seems he was deep in 7's too IIR..
Scott Rex doesn't say much but bet he's got a big number too....
Just saying....

FWIW: that cam is going in my new combo...

[mike leech]

Originally Posted by 60man

I assume this about Tigers Mike..and HP..
Jack Gaydosh dynoed his Tiger headed IAII (535 I think) before he tore it down to freshen up at seasons end...on 12-30-2006...with many passes on it..I couldn't figure out how to post the D sheet ..it can be searched on here.
It made1107 HP @ 7,200
854 ft lb @ 6,600

Seems he was deep in 7's too IIR..
Scott Rex doesn't say much but bet he's got a big number too....
Just saying....

FWIW: that cam is going in my new combo...

oh yea! I know that. Was pointing out that the first build was 845 on a 535. it took guys like rex, Gaydosh etc willing to invest in the heads to attain those levels was all i meant. They are the best performing platform but even it has had improvements and revisions was all i meant.

[60man]

Originally Posted by mike leech

oh yea! I know that. Was pointing out that the first build was 845 on a 535. it took guys like rex, Gaydosh etc willing to invest in the heads to attain those levels was all i meant. They are the best performing platform but even it has had improvements and revisions was all i meant.

Gotcha.....!!