TrackSpec Hood vents for E9x M3

[inTgr8r]

Originally Posted by cenix

I'm curious as to how these produce downforce? Anyone have any info to share on this?

As per Redd, it really doesn't add downforce; it reduces lift.

The air entering the engine compartment via the front grill & rad causes a high pressure area under the hood (lift).
The vents provide relief for this high pressure so the net result is more downforce.

...as well as heat reduction.

[roastbeef]

i would be interested in getting rid of the front oem kidney scoops that lead to the intake and making a scoop from behind the heat exchanger leading to the vents. not sure if there is room for it or not, but its a thought.

[cenix]

Originally Posted by inTgr8r

As per Redd, it really doesn't add downforce; it reduces lift.

The air entering the engine compartment via the front grill & rad causes a high pressure area under the hood (lift).
The vents provide relief for this high pressure so the net result is more downforce.

...as well as heat reduction.

I'm familiar with why there is hood venting and what it does, thanks to everyone who responded. Your post #13 stated that the vents added downforce, so that's why I asked, but I see what you were talking about (net result).

[Richbot]

iirc these cars only lift about a dozen lb at the front and have a little bit of rear downforce stock, so you might actually be into negative lift with the hood vented

[tlrid3r]

Originally Posted by Richbot

iirc these cars only lift about a dozen lb at the front and have a little bit of rear downforce stock, so you might actually be into negative lift with the hood vented

According to this data. The m3 shows 22lbs of lift in the front and 51lbs of lift in the rear.

http://www.m3post.com/forums/showthread.php?t=402401

http://www.m3post.com/forums/showthread.php?t=476271

[Datka]

http://seiboncarbon.com/products/dv-...mw-e92-m3.html
I know stock hood is not heavy, but this relatively inexpensive CF vented hood looks interesting I think

[inTgr8r]

Originally Posted by Datka

http://seiboncarbon.com/products/dv-...mw-e92-m3.html
I know stock hood is not heavy, but this relatively inexpensive CF vented hood looks interesting I think

That's definitely something to consider.
I know I would have a real hard time cutting up my hood.

I think the trackspec are a more efficient design, as they did some leg work to find the right locations.
For a pure track car its a pretty easy decision.

[Richbot]

Originally Posted by tlrid3r

According to this data. The m3 shows 22lbs of lift in the front and 51lbs of lift in the rear.

http://www.m3post.com/forums/showthread.php?t=402401

http://www.m3post.com/forums/showthread.php?t=476271

Derp yeah that's what I was thinking of but I must have been thinking of the delta compared to 335 (M3 has more lift in the rear compared to the 335 lifting more at the front)

[macdude357]

Originally Posted by tlrid3r

According to this data. The m3 shows 22lbs of lift in the front and 51lbs of lift in the rear.

http://www.m3post.com/forums/showthread.php?t=402401

http://www.m3post.com/forums/showthread.php?t=476271

Another interesting "Super Test" they did was with the Alpina B3 Twin Turbo (E92-based one). That car has a larger spoiler (similar to the aftermarket high kick ones for the E9x) and they found that it greatly reduced lift at the rear.

Something else to consider. I have the smaller N15Design vents on my hood. My last time out at Buttonwillow, the car wanted to oversteer in Riverside under neutral throttle. With bigger vents and a front lip, you may need to balance that out with some rear aero.

[M3 Number 86]

Originally Posted by macdude357

Another interesting "Super Test" they did was with the Alpina B3 Twin Turbo (E92-based one). That car has a larger spoiler (similar to the aftermarket high kick ones for the E9x) and they found that it greatly reduced lift at the rear.

Something else to consider. I have the smaller N15Design vents on my hood. My last time out at Buttonwillow, the car wanted to oversteer in Riverside under neutral throttle. With bigger vents and a front lip, you may need to balance that out with some rear aero.

when did you get those?!

[macdude357]

Originally Posted by M3 Number 86

when did you get those?!

I got them right before the Bimmer Challenge Buttonwillow event last month.

[scotty_miller]

Just ordered hood vents from these guys. Anxious to get them on over the winter. Their stuff looks like good quality compared to other companies making them

[dogbone]

Originally Posted by Richbot

iirc these cars only lift about a dozen lb at the front and have a little bit of rear downforce stock, so you might actually be into negative lift with the hood vented

The topic of air pressure in engine bays and wheel wells, and hoods generating lift is a new area of curiosity for me.

You have a solid technical grasp of these cars, so I'll ask you:

If you were to make a general guess-----how much change in lift/downforce do you think you might see from a vented hood? I saw in that linked article that the M3 is making 22lbs of front-end lift at 124mph. If you say that a "negative lift" situation might be the result of hood vents, I'm assuming you're thinking the change in force is more than 22 lbs. How much change in force do you think it could be?

And do you think the effects of the vented hood are overshadowed by having a lip and 5" splitter and canards in place already? (The addition of the lip and splitter changed the car DRAMATICALLY for the better.) Or would they all work together to create even more downforce?

Anyway, I'm curious to hear your thoughts.

[inTgr8r]

Another consideration is drag.

Adding lips , wings, canards etc.... almost always adds drag to go along with the benefits.
It may possibly be, that adding hood vents is a free lunch with respect to drag.

[roastbeef]

i'm liking this discussion about "reducing lift vs. adding downforce." i had never though about the two before as not being the same thing. there was some talk in another thread about reducing lift in the rear through a pretty hefty diffuser that extended way under the car. i simply hadn't thought of reducing lift in the front until the discussion in this thread.

one experience i can possibly relate, is losing my front center belly pan at the track last weekend. it was in rough shape, as well as the corners. the air pressure entering between the lip and the bumper was enough to blow the worn bottoms off my side felt pieces. shortly after that, the center belly pan got completely ripped out from under my car. i didn't go off, and i didn't hit anything- this was 100% the belly pan being tired, and air pressure.
that being said, i came around turn 8 at big willow with guns blazing and immediately knew something was different with the car. it sort of felt like fluttering. i pulled into the hot pit and hopped out to check my tires for something obvious... nothing. eyeballed my brakes real quick... nothing obvious. shrugged my shoulders and went back out for a few more laps. i sort of attributed it to an unbalanced wheel/tire, or maybe a big wad of rubber inside one of the barrels of the wheels. it wasn't until a few sessions later when my brake pads were finished and i swapped them out that i discovered the entire front belly pan was gone. there was some crap on the track at the bottom of the hill of turn 6, but i didn't quite recognize it as mine. lol thinking back, it was probably my belly pan. i've always thought of it to be an aero piece (it is shaped like an air foil and plays a role in cooling), however, i just didn't realize how it would feel without it.
if something like the undertray could cause a noticeable effect, i'm optimistic that these vents can help as well.

[cenix]

^ I think you bring up a good point about the importance of the underside aero.

I think there should be more potential to reduce lift by focusing on the underside of the car. A faster moving/less turbulent airflow underneath the car helps to reduce lift even further than say, hood vents (although hood vents are less costly and easier to implement). Ferrari, Nissan GTR, Porsche, and other high performance cars from the factory come with full underside panels for this purpose.

I read that for F1 cars, around 60% of total downforce is from front splitters and rear wings. The remaining amount is mostly from underside aero. Food for thought.

[M3 Number 86]

Originally Posted by roastbeef

i'm liking this discussion about "reducing lift vs. adding downforce." i had never though about the two before as not being the same thing. there was some talk in another thread about reducing lift in the rear through a pretty hefty diffuser that extended way under the car. i simply hadn't thought of reducing lift in the front until the discussion in this thread.

one experience i can possibly relate, is losing my front center belly pan at the track last weekend. it was in rough shape, as well as the corners. the air pressure entering between the lip and the bumper was enough to blow the worn bottoms off my side felt pieces. shortly after that, the center belly pan got completely ripped out from under my car. i didn't go off, and i didn't hit anything- this was 100% the belly pan being tired, and air pressure.
that being said, i came around turn 8 at big willow with guns blazing and immediately knew something was different with the car. it sort of felt like fluttering. i pulled into the hot pit and hopped out to check my tires for something obvious... nothing. eyeballed my brakes real quick... nothing obvious. shrugged my shoulders and went back out for a few more laps. i sort of attributed it to an unbalanced wheel/tire, or maybe a big wad of rubber inside one of the barrels of the wheels. it wasn't until a few sessions later when my brake pads were finished and i swapped them out that i discovered the entire front belly pan was gone. there was some crap on the track at the bottom of the hill of turn 6, but i didn't quite recognize it as mine. lol thinking back, it was probably my belly pan. i've always thought of it to be an aero piece (it is shaped like an air foil and plays a role in cooling), however, i just didn't realize how it would feel without it.
if something like the undertray could cause a noticeable effect, i'm optimistic that these vents can help as well.

Most of the downforce in F1 is from the underbody and diffuser.

Think of a silhouette of a car. It's basically an airfoil. Shaped like the ones on planes. That's why cars have lift because it's natural shape is a damn wing trying to fly off the ground. Lol

Smoothen out the air underneath let it exit wide with a real diffuser should suck the car downwards enough to generate real downforce as opposed to reducing lift.

[aus]

Originally Posted by roastbeef

i'm liking this discussion about "reducing lift vs. adding downforce." i had never though about the two before as not being the same thing. there was some talk in another thread about reducing lift in the rear through a pretty hefty diffuser that extended way under the car. i simply hadn't thought of reducing lift in the front until the discussion in this thread.

one experience i can possibly relate, is losing my front center belly pan at the track last weekend. it was in rough shape, as well as the corners. the air pressure entering between the lip and the bumper was enough to blow the worn bottoms off my side felt pieces. shortly after that, the center belly pan got completely ripped out from under my car. i didn't go off, and i didn't hit anything- this was 100% the belly pan being tired, and air pressure.
that being said, i came around turn 8 at big willow with guns blazing and immediately knew something was different with the car. it sort of felt like fluttering. i pulled into the hot pit and hopped out to check my tires for something obvious... nothing. eyeballed my brakes real quick... nothing obvious. shrugged my shoulders and went back out for a few more laps. i sort of attributed it to an unbalanced wheel/tire, or maybe a big wad of rubber inside one of the barrels of the wheels. it wasn't until a few sessions later when my brake pads were finished and i swapped them out that i discovered the entire front belly pan was gone. there was some crap on the track at the bottom of the hill of turn 6, but i didn't quite recognize it as mine. lol thinking back, it was probably my belly pan. i've always thought of it to be an aero piece (it is shaped like an air foil and plays a role in cooling), however, i just didn't realize how it would feel without it.
if something like the undertray could cause a noticeable effect, i'm optimistic that these vents can help as well.

Good post.
What did you replace the under panels with? OEM or one of the metal units out now?
.

[roastbeef]

Originally Posted by aus

Good post.
What did you replace the under panels with? OEM or one of the metal units out now?
.

Oem panels are in the mail from FCP euro. I'm planning on sending my thrashed panels back to them for replacements in a few years.

[Richbot]

Originally Posted by dogbone

The topic of air pressure in engine bays and wheel wells, and hoods generating lift is a new area of curiosity for me.

You have a solid technical grasp of these cars, so I'll ask you:

If you were to make a general guess-----how much change in lift/downforce do you think you might see from a vented hood? I saw in that linked article that the M3 is making 22lbs of front-end lift at 124mph. If you say that a "negative lift" situation might be the result of hood vents, I'm assuming you're thinking the change in force is more than 22 lbs. How much change in force do you think it could be?

And do you think the effects of the vented hood are overshadowed by having a lip and 5" splitter and canards in place already? (The addition of the lip and splitter changed the car DRAMATICALLY for the better.) Or would they all work together to create even more downforce?

Anyway, I'm curious to hear your thoughts.

I’d think keeping air out from under the car must be an order of magnitude larger than any help you get from venting the hood but just a guess? Certainly once you’ve closed that off with the front aero as well as possible, the cooling air suddenly becomes a bigger contributor to the remaining crappy aero problems we have to deal with when the engine is in the wrong place? My envelope math is way too full of assumptions for me to guess at a number but realistically I think dozens of lb would be the most to hope for. Lift mostly just comes from the plain sad truth that cars do not fly so clean flow in the 3-4”’of space underneath is near impossible to achieve and even worse with a front engine.

The F1 comparisons are uh...not useful for hopefully obvious reasons But one useful takeaway... they don’t dump their radiators under the car

[tlrid3r]

Originally Posted by Richbot

I’d think keeping air out from under the car must be an order of magnitude larger than any help you get from venting the hood but just a guess? Certainly once you’ve closed that off with the front aero as well as possible, the cooling air suddenly becomes a bigger contributor to the remaining crappy aero problems we have to deal with when the engine is in the wrong place? My envelope math is way too full of assumptions for me to guess at a number but realistically I think dozens of lb would be the most to hope for. Lift mostly just comes from the plain sad truth that cars do not fly so clean flow in the 3-4”’of space underneath is near impossible to achieve and even worse with a front engine.

The F1 comparisons are uh...not useful for hopefully obvious reasons But one useful takeaway... they don’t dump their radiators under the car

That's why I coupled the hood vent with a gt4 lip install and made sure as much as possible the under belly is covered. I'll be at track 12/15 and 12/16. I'll report back on the butt feeling

[dogbone]

Originally Posted by Richbot

I’d think keeping air out from under the car must be an order of magnitude larger than any help you get from venting the hood but just a guess? Certainly once you’ve closed that off with the front aero as well as possible, the cooling air suddenly becomes a bigger contributor to the remaining crappy aero problems we have to deal with when the engine is in the wrong place? My envelope math is way too full of assumptions for me to guess at a number but realistically I think dozens of lb would be the most to hope for. Lift mostly just comes from the plain sad truth that cars do not fly so clean flow in the 3-4”’of space underneath is near impossible to achieve and even worse with a front engine.

The F1 comparisons are uh...not useful for hopefully obvious reasons But one useful takeaway... they don’t dump their radiators under the car

If it was dozens of pounds, that would be great. More than I thought it would be.

As a novice to this topic, I'm working under the assumption that the 5" splitter is doing all the heavy work, and that everything else is extra bits of flavor by comparison.

My splitter may not sit super low when the car is at rest, but when I'm pressed into a turn, it's quite close to the ground. In a bowl type of turn, it's almost rubbing the ground. (I don't run super stiff springs.)

Anyway, the main goal of this hood vent project was to flow more air through the engine bay and perhaps cool it down a bit in there. If there's any negative lift/downforce to be had, I will consider it a gift from the gods of grip.