Front End Aerodynamics - How Different Setups Effect Drag and Lift

[wparsons]

^^ Hahaha!

Awesome thread, keep them coming! I love that the highest downforce setup here is also the lowest drag. Should help with convincing the wife it's a necessary mod

[Vracer111]

I have a question regarding venting the fenders. From another thread:

Originally Posted by eric6

The engine bay should be slightly pressurized from air coming in through the radiator/condenser. Through our CFD research, it appears that the area around the vents are near ambient air pressure. I would think these vents function.



Well executed. I have been wanting to something like this but my balls aren't nearly large enough to cut into my new car.

I like what the OP and others did in that thread to make a more functional OEM part and would love to do this, but I also love the TRD fender fins I already have and paid good money for. I've been wondering this for a while now though... could the TRD fins also be made a real functional vent by cutting the necessary hole in the fender then opening up their triangular cross-sectioned backside? Or would doing so try to reverse flow direction and mess too much with the air flow over the fin and subsequently the mirrors, compromising functionality? Any thoughts?

[VerusEric]

Originally Posted by Vracer111

I have a question regarding venting the fenders. From another thread:


I like what the OP and others did in that thread to make a more functional OEM part and would love to do this, but I also love the TRD fender fins I already have and paid good money for. I've been wondering this for a while now though... could the TRD fins also be made a real functional vent by cutting the necessary hole in the fender then opening up their triangular cross-sectioned backside? Or would doing so try to reverse flow direction and mess too much with the air flow over the fin and subsequently the mirrors, compromising functionality? Any thoughts?

Should work if you're talking about opening up the backside of that fender fin IMO.

[Vracer111]

Originally Posted by NotEric6

Should work if you're talking about opening up the backside of that fender fin IMO.

Yep, the slanted triangular rear surface of the fin. So you can't think of any possible issues from an aero perspective that would be worth fretting over if doing this, like would it change the shape of the air path towards the mirrors in any possible negative manner? Thanks.

I could do it now with the scan guage II oil temp/intake temp display I guess - but there are so many other things I have going on that this is down in the priorities. Probably would be better to get some air temperature probes/thermocouples and put them strategically in the engine bay for more accurate before/after comparison purposes though... I love testing/experimenting (which is why I love my job sometimes and like it most of the rest of the time... )

[lamawithonel]

Originally Posted by Vracer111

Yep, the slanted triangular rear surface of the fin. So you can't think of any possible issues from an aero perspective that would be worth fretting over if doing this, like would it change the shape of the air path towards the mirrors in any possible negative manner? Thanks.

I could do it now with the scan guage II oil temp/intake temp display I guess - but there are so many other things I have going on that this is down in the priorities. Probably would be better to get some air temperature probes/thermocouples and put them strategically in the engine bay for more accurate before/after comparison purposes though... I love testing/experimenting (which is why I love my job sometimes and like it most of the rest of the time... )

Cutting a hole would vent air between the engine bay and the wheel well. It's hard to say which would be higher pressure, but either way it's probably not worth it. If the engine bay is more pressurized it won't do anything for the wheel well, but could help cooling. Likewise, if the wheel well is more pressurized or they're about the same, you're going to spew all sorts of road grime in there and could decrease cooling efficiency. With a custom molded piece to pipe air directly from the wheel well to the vent you could make it work, but it's really a one or the other option-- either vent the engine bay or vent the wheel wells.

The two better options, IMO, would be to cut a new vent just for the wheels, or install a radiused fender.
@boostedfrs's custom wheel well vent:



Victory Function +20mm aero fenders, designed by MotoIQ:

[lamawithonel]

@NotEric6,

On a lot of high-end cars the front splitter slopes upward into the inside edge of the wheel wells. Why do they do that, and would it help on the twins? Here are some pictures for reference:

Porsche 918 (not the blue piece, but the area next to it):


2011 Audi R18:


Varis piece for an R35


Amuse piece for an R35:

[Vracer111]

Originally Posted by lamawithonel

Cutting a hole would vent air between the engine bay and the wheel well. It's hard to say which would be higher pressure, but either way it's probably not worth it. If the engine bay is more pressurized it won't do anything for the wheel well, but could help cooling. Likewise, if the wheel well is more pressurized or they're about the same, you're going to spew all sorts of road grime in there and could decrease cooling efficiency. With a custom molded piece to pipe air directly from the wheel well to the vent you could make it work, but it's really a one or the other option-- either vent the engine bay or vent the wheel wells.

The two better options, IMO, would be to cut a new vent just for the wheels, or install a radiused fender.

Um...the fender well is completely sealed off from the engine bay from the factory, just cutting a hole in the fender ANYWHERE will not affect anything in regards to wheel well pressures as it's isolated from both the engine bay and the metal fender. You would have to remove the fender liners to be able to do what you are talking about. The point of making the fender vent functional is to get some heat out of the sealed engine bay... which it has been proven to do with modified stock garnishes.

[avishenoy1]

Originally Posted by Vracer111

I have a question regarding venting the fenders. From another thread:


I like what the OP and others did in that thread to make a more functional OEM part and would love to do this, but I also love the TRD fender fins I already have and paid good money for. I've been wondering this for a while now though... could the TRD fins also be made a real functional vent by cutting the necessary hole in the fender then opening up their triangular cross-sectioned backside? Or would doing so try to reverse flow direction and mess too much with the air flow over the fin and subsequently the mirrors, compromising functionality? Any thoughts?

Originally Posted by VeloxEric

Should work if you're talking about opening up the backside of that fender fin IMO.

Wow, so I actually had this exact same idea before I stumbled upon this thread. Based on my limited knowledge of aerodynamics, I figured that the TRD fin would create a low pressure region in it's wake allowing for efficient venting of high pressure air in the engine bay if the rear facing section were cut open. I am planning to do this on my car in the near future and will attempt to do some testing of functionality with tufts.

My concern about this design however is that the air exiting the fin will hit the side view mirrors and potentially cause a significant increase in drag.

Can anyone else comment on this? I'd love to see some CFD testing on how the fin actually affects airflow on the car.

[VerusEric]

Originally Posted by lamawithonel

@NotEric6,

On a lot of high-end cars the front splitter slopes upward into the inside edge of the wheel wells. Why do they do that, and would it help on the twins?

I apologize for not seeing this earlier.

They do this to increase downforce on the front end, similar to how a diffuser in the rear works. It is possible it could help with the twins but a lot of development would need to take place for a splitter like this to be implemented correctly. Implemented incorrectly and it could add significant drag and reduce downforce.

Hope that helps some.

[makinen]

Originally Posted by avishenoy1

Wow, so I actually had this exact same idea before I stumbled upon this thread. Based on my limited knowledge of aerodynamics, I figured that the TRD fin would create a low pressure region in it's wake allowing for efficient venting of high pressure air in the engine bay if the rear facing section were cut open. I am planning to do this on my car in the near future and will attempt to do some testing of functionality with tufts.

My concern about this design however is that the air exiting the fin will hit the side view mirrors and potentially cause a significant increase in drag.

Can anyone else comment on this? I'd love to see some CFD testing on how the fin actually affects airflow on the car.

Like this? (knock off for peace of mind )



At least no bad effect measured by intake air temparature or coolant temparature.

[gatorac]

Great info. Especially since I have a 96 supercharged Miata that I am adding aero to. Just put on the BlackBird Fabworx rear spoiler and I'm sure something up front is in order. Thanks for sharing.

[Surok]

Did anybody ever end up designing a splitter for the twins that incorporates two venturi tunnels that funnel air into the front wheel wells, as discussed above.

I am planning on developing one for my car but i lack the software to figure out the exact angles that the venturi tunnels need to be at for optimum effect.

[snoxracer183]

Build your own out of alumalite, and use these:

Professional Awesome Splitter Diffusers

[Bergycheese348]

Originally Posted by Vracer111

I have a question regarding venting the fenders. From another thread:


I like what the OP and others did in that thread to make a more functional OEM part and would love to do this, but I also love the TRD fender fins I already have and paid good money for. I've been wondering this for a while now though... could the TRD fins also be made a real functional vent by cutting the necessary hole in the fender then opening up their triangular cross-sectioned backside? Or would doing so try to reverse flow direction and mess too much with the air flow over the fin and subsequently the mirrors, compromising functionality? Any thoughts?

Originally Posted by makinen

Like this? (knock off for peace of mind )

Attachment 129658

At least no bad effect measured by intake air temparature or coolant temparature.

(Hopefully that all pasted right, my first try quoting multiple people)

Does anyone have any input on this? Kinda a old thread, but would like some input as engine bay pressure at high speeds is a known problem, but at the same time I don’t want to increase drag by a lot and for it to not be worth it and screw up a pair of the CF Aero Fins. (I’m planning on getting the APR GT3 mirrors or similar soon)