Coweling and engine bay aero

[Dmak]

Here is my 2cent. Go google and take a look at some high performance front engine sports cars, viper, corvette, amg gtr, etc. They all have a seal between the base windshield cowl to the engine bay. Theres a reason for it. Anyone who wants to argue how its poor aero, hurting cooling(or feeling) should go do some basic google research to get some ideas on the engineering of it.

I have to say, i did try remove the base windshield cowl and seal on my bmw as well as my other vehicle before. And yes. It helps let heat out of engine bay when car is moving at low speed or stop. but i still end up keeping the cowl and seal in place. Because i believe there good reasons behind the engineering of it.

Ps. Just google some wrc engine bay pictures. Looks like all of those cars have the "performance robbing" cowl installed...i wonder why. They must not know how to build a race car?

 

[rac]

imo the video is pretty solid and as good as free information gets on the web.
some minor frontal lift is pretty much the norm for road cars. you can go away and find the text book values if you dont believe it. i've dabbled in vehicle dynamics modelling software and its normal to use a coefficient for front end lift for road cars (as opposed to downforce). i dont think there is much to debate at all with the video, it articulates vehicle aero fundamentals well for the laymen.

the whole cowl / cowless thing + raised hood if you go that extreme is really a question of when cooling is most effective for your application - driven at speed versus stationary. i've done both with my car i feel like i ran cooler while cowless in stop go traffic in hot weather, or if not enough cooling is done on a cool down lap and you have to go sit and idle in a pit lane queue. but if your going flat out around the track yeah your going to get better cooling through the actually cooling system with a cowl - forcing the air through the designed flow path while heading down the straights and in the brake zones. as for lift, i had on action shot somewhere of my hood actually being tilted on a slight angle exiting a corner!

 

[martymil]

The cowl has nothing to do with aero, it serves a few purposes but none of them are performance orientated.

To allow fresh air to cabin filters and to keep oil and coolant off your windscreen in case of engine or component failure.

Also in case of fire during an engine failure to subdue the flames, choke or minimise them

To direct air around the gearbox.

That is why I cut mine down but not totally remove to still be able to channel some air around/past the gearbox.

I'm not worried about fire as the engine is running cool and all my hot parts are ceramic coated to reduce fire risk.

 

[The Convert]

The cowl has nothing to do with aero, it serves a few purposes but none of them are performance orientated.

To allow fresh air to cabin filters and to keep oil and coolant off your windscreen in case of engine or component failure.

Also in case of fire during an engine failure to subdue the flames, choke or minimise them

To direct air around the gearbox.

That is why I cut mine down but not totally remove to still be able to channel some air around/past the gearbox.

I'm not worried about fire as the engine is running cool and all my hot parts are ceramic coated to reduce fire risk.

I’m glad for you that you feel your car is perfectly setup. With that said, stop adding your data less claims. If you want to add value, go do some testing and give us your data and testing method. If I were making a claim that what I did was so perfect, that’s what I would do.

 

[martymil]

You have no data that there is aero, your just making assumptions.

I was speaking with a general motors engineer some 20 years ago as I wanted to remove the engine/bonnet seal on a commodore and thats how i know the purpose of these, unless they changed something in the last few years but looks like they still use the same technology on todays cars to seal the hood just look at the m2c.

 

[KClemente]

Here's a photo and a video of BMW AG's WTCC race car. You'll instantly notice that even they have a cowl installed. In a world where aerodynamics plays one of the biggest roles in lap times, the bright engineers decided it'd be best to keep a form of cowling on.

Air is messy. It'll go anywhere it wants to and is invisible to us. If anyone here has ever worked on an F10, they'll notice that everything and I mean everything is covered underneath. It virtually has a slick bottom and that's because of stricter emissions regulations forcing manufacturers to be more aerodynamic every way they can.

You'll notice on a lot of BMW's race cars that they block-off a lot of the designed intakes and that's obviously for aerodynamic purposes. They build their race cars around their motor and since the E90 WTCC only uses a 4 cylinder, it really doesn't need all that much cooling. If the CAD they used showed that no cowl would be beneficial, i'm sure that they would've deleted it.

All in all, if you guys really want to achieve some real world aero, balance the front with the rear by adding a front lip or air dam, and a trunk spoiler like an MPerformance one or even a CSL duckbill trunk. Don't forget about the underbody as there is so much turbulence going on under there ESPECIALLY for you muffler delete guys (easily the best way to induce drag and lift).

If you made it to this paragraph of my rant here's a cool link I highly suggest reading up on as it was developed with help from a couple of aerodynamicist's from U of M. E90 Real Aero

BMW WTCC Race Car

 

[martymil]

The reason they leave the cowl in is to stop oil and coolant from going all over the windscreen especially in a race car as engine failures happen a lot,

Now imagine going 130mph plus and your enter a long sweeping bend and your engine blows.

 

[The Convert]

You have no data that there is aero, your just making assumptions.

I was speaking with a general motors engineer some 20 years ago as I wanted to remove the engine/bonnet seal on a commodore and thats how i know the purpose of these, unless they changed something in the last few years but looks like they still use the same technology on todays cars to seal the hood just look at the m2c.

Anywhere there is air flow there is aero. It’s as if you don’t even understand what the words mean. 20 years ago?!?!? Did auto manufacturers even use wind tunnels or have computational air flow models 20 years ago?

 

[JBacon335]

Anywhere there is air flow there is aero. It’s as if you don’t even understand what the words mean. 20 years ago?!?!? Did auto manufacturers even use wind tunnels or have computational air flow models 20 years ago?

Pretty sure they had all that in 2000 and a lot earlier

 

[ajm8127]

Pretty sure they had all that in 2000 and a lot earlier

Perhaps, but computer modeling is generations ahead in that time. Intel and AMD were both releasing single core processors at around 1.0 GHz in the year 2000 to give you perspective. The enormous increases in processing power (multiple cores and IPC) in that time allowed the modeling software to become much more powerful and accessible. Computer modeling is a completely different world than it was 20 years ago.

by cutting your cowl you actually increase flow through the engine bay and directing the air over the wind shield causing extra down force on the car, but it does increase drag.

As I understand it there is a HIGH pressure area at the top of the hood and the base of the windshield because the shape of the car is forcing the air up and out. So removing the cowl would cause air to enter the engine bay here. That air needs to go somewhere so it either comes out of the wheel wells or goes under the car. Neither are beneficial at speed. I am pretty sure you want laminar flow under the car and a boundary layer on the sides.

To increase flow through the bay for cooling, you need to place vents in low pressure areas about 1/3 to 1/2 of the way back on hood like this:

The vents are located where the pressure is low to cause air to flow in through the front of the bumper where the pressure is high then through the radiator and out of the hood vents.

[Edit]

I just saw this gem from the thread in post #3:

 

[Dmak]

The reason they leave the cowl in is to stop oil and coolant from going all over the windscreen especially in a race car as engine failures happen a lot,

Now imagine going 130mph plus and your enter a long sweeping bend and your engine blows.

Whatever makes u feel better at night.

See the seal just below the wipers?? I guess tesla also need to stop fuel/coolant/fire from coming up from the storage area. Tesla must not know shit about aero....damn it. I m sure tesla put the seal there to hurt their performance and mileage.

Yes yes. I know you will then say theres no cooling needed to worry about on the tesla. Again, believe what u believe and what makes u feel better at night.

 

[iminhell1]

If you made it to this paragraph of my rant here's a cool link I highly suggest reading up on as it was developed with help from a couple of aerodynamicist's from U of M. E90 Real Aero

B.May left the BMW forums and virtually all the internet. He's the sole reason I got into this platform. I've talked with him a few times.
Really wish he wasn't so busy and had more time to give out free advice.

He still has the car and it's under the knife currently. Prepping for 1/2 mile and longer stuff.

 

[martymil]

Whatever makes u feel better at night.


View attachment 41625

See the seal just below the wipers?? I guess tesla also need to stop fuel/coolant/fire from coming up from the storage area. Tesla must not know shit about aero....damn it. I m sure tesla put the seal there to hurt their performance and mileage.

Yes yes. I know you will then say theres no cooling needed to worry about on the tesla. Again, believe what u believe and what makes u feel better at night.

If you read what I wrote earlier than that they also use it for fresh air entry for the aircon and cabin, your argument is mute as there is no engine.

 

[martymil]

Some day you are going to wake up and realize the amount of bullshit that you have spewed.

The only shit spewed here is your stupid statement, just like under bonnet aero because of the cowl.

Under bonnet aero my ass, some just like to talk such rubbish.

Here you go nismo race car vs factory gtr, where is your under bonnet aero

\

 

[iminhell1]

I think most of you guys are in an E90, but for us poor folk in the baby this is our issue at speed --> https://www.1addicts.com/forums/showthread.php?t=938791

So the underhood aero is of interest for me. And I feel it's not a single thing that can improve things. The underhood is such a high pressure area that we need to be able to mitigate the entry air and increase the exit air.
Seen one guy recently who's adding the euro diesel radiator shutters to calm all the air entering. I think that's a pretty novel idea.
I also look at how the E90 M3 have the cooling for the radiator setup. I really like that idea also.

 

[KClemente]

B.May left the BMW forums and virtually all the internet. He's the sole reason I got into this platform. I've talked with him a few times.
Really wish he wasn't so busy and had more time to give out free advice.

He still has the car and it's under the knife currently. Prepping for 1/2 mile and longer stuff.

If you ever get in contact with him again, ask him how the aero is doing!

 

[The Convert]

The only shit spewed here is your stupid statement, just like under bonnet aero because of the cowl.

Under bonnet aero my ass, some just like to talk such rubbish.

Here you go nismo race car vs factory gtr, where is your under bonnet aero

View attachment 41645\View attachment 41646

they still have the sealing structure between the fire wall and the hood. No one is arguing over your little air filter covers. Those are only there to keep rain out of the cabin. The only thing Nissan essentially did between those two images is remove the air filter covers. You also failed to add an image of the hood with its MASSIVE vents and the sideskirts with the massive outlets...

 

[martymil]

@The Convert Cherry picking huh, must be cherry picking this too.

He is the latest race car from BMW Racing, where is the holes in the bonnet and guess what no cowls.

Its a purpose built speedway car that races in your country

LOL

 

[martymil]

Its got nothing to do with casting and I wont reveal my involvement as its none of your business.

Here is another endurance built f20 engine bay, I'm posting cars that totally contradict your theory about engine bay aero that use stock hoods and delete
the factory cowl plastics, even purpose built race cars get rid of it but they also include extra heat venting so its not a direct comparison.

 

[martymil]

Berk technologies time attack car