Aestheticly, You may not like the BSM's which is OK, Your intitled.
However, bear-in-mind that they do serve a function and most smart racers keep them on.
1. They straighten out the side air flow and aid laminar flow
2. They have a small downforce componant
3. They act as a fence in the aerodynamics in that they prevent the hood cowl downwash from wrapping underneath the rear wheels and adding rear lift.
This only takes place above 100MPH and is really only effective above 150MPH.
So laugh all you want but a BSM car will beat a non BSM car on the back straight and will be more stable in high speed turns.
Note that the C6 doesn't have them because those bad aerodynamics have been engineered out.
In addition I have checked the bottom of my BSM's and they are all chipped. It seems they have stopped debri and small stones and have saved my upper door panels and rear deck lid from scratches and paint chips. I also have noticed that after a hard weekend at the track that the area under the BSM is covered with track debri (rubber and brake dust, dirt etc.) and racing fluids ( oil, brake fluid, antifreeze, tranny & diff fluid slurry) but the top side is clean.
I have also noticed that while driving both types of equipped cars in rain the rearview mirrors of a BSM equipped car stays clean and more is visable, longer. They may just save you a shunt in the "S'es".
Hey Hey Hey!!!!!!!!!! Don't be dissn my car. Niether me, my car or my bsm's are gay. The only time I don't like them is when I'm cleaning the car.
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Originally posted by DJWorm 1. They straighten out the side air flow and aid laminar flow
2. They have a small downforce componant
3. They act as a fence in the aerodynamics in that they prevent the hood cowl downwash from wrapping underneath the rear wheels and adding rear lift.
Not trying to doubt you DJ as I trust your opinion but are those things really applied with such precision? They appear to be just stuck on using the "calibrated eyeball" method. I would think that to perform all of those functions (and I do believe your theories are sound) that they would need to be in a precise location on the doors based on wind tunnel testing which I don't believe was done (at least on the moldings). Or are you just saying that the above were unintended benefits of the BSM's?
Although the effect may be slight and is non exsistant below 100MPH there is a definite aerodynamic effect especially above 150MPH.
This was first noticed by a number of racers at Daytona some years back. What they noticed was that BSM equipped cars were more stable going into the high banked turns off the straight . Not only were they more stable but they had a 0.5 to 1 MPH faster straight trap speed. That may not seem like much until you add it up over 24 hours.
Further wind tunnel testing was done.
The conclusions were that the major benefit was the better laminar flow along the sides of the car caused by the BSM's acting as a lateral fence. This prevented the hood cowl downwash from reaching and wrapping under the rear wheels and lifting the rear. The result was that the rear did not lift as much and the car was more stable. It was felt that the BSM actually didn't inhibit the downwash but in fact strengthened the laminar flow boundry layer and thus allowed the laminar flow to sweep the downwash rearward rather than allowing the downwash to destroy the laminar flow boundry layer and continue downward.
Further testing revealed a small downforce componant. This was discovered when comparing an increased rake in a BSM and a non BSM car. The % of downforce increase caused by increasing the rake of the cars was greater with the BSM's.
This has also been confirmed to me by other racers one of whom does development work for Chevy.
I have also spoken with the folks at Pratt & Miller about this. The C5R's do not require the BSM's as they derive their downforce in other ways ie... front splitter, larger gill vents, rear wing and rear diffuser.
I consider the data very reliable but not necessarily relevant on street cars
don't they also help if someone opens their door and it protects your Z from the other door (or even a shopping cart if you use it as your grocery getter)
Originally posted by DJWorm No, I'm not BSing anyone.
Although the effect may be slight and is non exsistant below 100MPH there is a definite aerodynamic effect especially above 150MPH.
This was first noticed by a number of racers at Daytona some years back. What they noticed was that BSM equipped cars were more stable going into the high banked turns off the straight . Not only were they more stable but they had a 0.5 to 1 MPH faster straight trap speed. That may not seem like much until you add it up over 24 hours.
Further wind tunnel testing was done.
The conclusions were that the major benefit was the better laminar flow along the sides of the car caused by the BSM's acting as a lateral fence. This prevented the hood cowl downwash from reaching and wrapping under the rear wheels and lifting the rear. The result was that the rear did not lift as much and the car was more stable. It was felt that the BSM actually didn't inhibit the downwash but in fact strengthened the laminar flow boundry layer and thus allowed the laminar flow to sweep the downwash rearward rather than allowing the downwash to destroy the laminar flow boundry layer and continue downward.
Further testing revealed a small downforce componant. This was discovered when comparing an increased rake in a BSM and a non BSM car. The % of downforce increase caused by increasing the rake of the cars was greater with the BSM's.
This has also been confirmed to me by other racers one of whom does development work for Chevy.
I have also spoken with the folks at Pratt & Miller about this. The C5R's do not require the BSM's as they derive their downforce in other ways ie... front splitter, larger gill vents, rear wing and rear diffuser.
I consider the data very reliable but not necessarily relevant on street cars
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