Presented by Nine Lives Racing
egoman
egoman Reader
5/27/21 12:23 p.m.

Looking at the inner fenders of the Transcona Cougar I came upon an idea. With the double walled construction of the inner fenders I felt that  we could do something with that space. Many people will vent the front fenders to alleviate air pressure buildup. Kind of aerodynamically dirtys the front fender though? By louvering the inner structure and flowing that air to a venturi area of the exhaust it would reduce the under fender pressure and consequently increase front down force. This wasn't just a thought , I added a detailed sketch to go with it. LOL.

While this would work better with a side pipe system like I am planning it could also be incorporated into an under car system as well?

If you turned the pipe straight up you might even gain rear down-force.

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
5/27/21 2:56 p.m.

what is the difference between 'venturi' and 'exhaust leak'?

I don't even know what the pressure inside an exhaust system normally is, but you need to make the exhaust pipe small enough to lower the pressure below atmospheric. Again, dunno how small that section of exhaust pipe would be. 

egoman
egoman Reader
5/27/21 3:18 p.m.
Robbie (Forum Supporter) said:

what is the difference between 'venturi' and 'exhaust leak'?

I don't even know what the pressure inside an exhaust system normally is, but you need to make the exhaust pipe small enough to lower the pressure below atmospheric. Again, dunno how small that section of exhaust pipe would be. 

We have used exhaust systems in the past for crankcase evacuation. It would have to pull a vacuum for that to take place. It is the placement of the inner nozzle that would dictate the vacuum produced.

JaxRhapsody
JaxRhapsody New Reader
5/30/21 3:08 a.m.
egoman said:

Looking at the inner fenders of the Transcona Cougar I came upon an idea. With the double walled construction of the inner fenders I felt that  we could do something with that space. Many people will vent the front fenders to alleviate air pressure buildup. Kind of aerodynamically dirtys the front fender though? By louvering the inner structure and flowing that air to a venturi area of the exhaust it would reduce the under fender pressure and consequently increase front down force. This wasn't just a thought , I added a detailed sketch to go with it. LOL.

While this would work better with a side pipe system like I am planning it could also be incorporated into an under car system as well?

If you turned the pipe straight up you might even gain rear down-force.

You're not going to gain downforce by aiming the exhaust to the sky. It's not going to create thrust.

egoman
egoman Reader
5/30/21 5:53 p.m.

In reply to JaxRhapsody :

Depends on how much nitro I run doesnt it?

NOT A TA
NOT A TA SuperDork
5/30/21 8:30 p.m.

Doubtful you'd be able to pull a large enough volume of air from the wheel well to have any effect. I too had headers that pulled crankcase air but they have a small diameter hose compared with what you'd need to scavenge a wheel well. A simple louvered vent to the top or side of the fender would probably do more.

egoman
egoman Reader
5/31/21 5:50 p.m.

In reply to NOT A TA :

I agree with you, as this was just a thought exercise. I had intentions of going with a IMSA style fender to release under fender pressure. I just want the car clean aerodynamically if bonneville ever enter my plans. 

BA5
BA5 GRM+ Memberand Reader
6/25/21 1:56 p.m.

It's not a bad idea if you leave the exhaust part out of it.

Rather than vent the high pressure wheel well air straight out the top, you could run it through some ducting to an area that's 'cleaner'.  Maybe out the back?  So long as you have a pressure differential and low restriction ducting the air will flow.  You could even boost the wheel well scavenging by ducting it to a place that is lower pressure than the hood.

Barb_Dwyer
Barb_Dwyer New Reader
7/28/21 4:34 p.m.

In reply to egoman :

It's unlikely that you could pressurize the wheel well with enough air to do any good. Unlike wheel wells that you would need to scavenge, headers pull crankcase air through a small diameter hose. The fender would benefit more from a louvered vent at the top or side.

Our Preferred Partners
T8wSlDv1dnJmugjQ8bClxo9HutUJioC8KzKa3HKDF6U07UbUpJOXqHBolkzanLzt