[tylerhart_21]

I was looking online and found this diagram, which lead me to look for aerodynamic parts for the e92 besides going full race car mode. Does anyone know of aero parts you could put on the e92 non-m to improve the aerodynamics? Also, how much will they improve the cars aerodynamics?

[tcphoto]

It looks like the difference starts around the windshield and gets worse at the shark fin. It doesn't state if the M3 is a slick top but I would guess so and the 335 most likely has a sunroof and no trunk lip. The PO added an Aero lip, rear window and trunk lip on mine. I almost immediately pulled the rear items off and replaced them with a carbon fiber lip on the trunk.

[streetpro]

You have to define what to improve...
if Cd (coefficient of drag, basically how smoothly the car goes through the air) then take a closer look as basic shape has better Cd then M3 (and it makes perfect sense as M is optimized for performance, not consumption).
If more downforce is asked, it comes with a price tag of higher drag and additional spoilers/wings...
and yes, the basic shape has light front at high speeds (over 180 kmh let say), anyone on autobahn has experienced this phenomena when chasing a P911T I guess :-)
Vented hood improves the matters a bit, at least for me it has worked fine (the vents/louvers must be in the front section of the hood, where the low pressure area is, not at the rear where is the M3 intake opening and people have feelings that it ventilates the engine - in reality it does the opposite).

[Thumbie]

That is a cool comparison.

So from what I am gathering, and assuming you are talking about downforce per streetpro's comment, adding a little downforce to the front would be my first step.

I personally am considering swapping to M3 front bumper or adding a like a lip/dam. Next would be rear spoiler or, and I haven't done research yet, cutting up the rear bumper to relieve pressure buildup (this is common on miatas).

From there you could get into more advanced things like vents in the fender and brake ducting, etc.

[tylerhart_21]

Originally Posted by streetpro

You have to define what to improve...
if Cd (coefficient of drag, basically how smoothly the car goes through the air) then take a closer look as basic shape has better Cd then M3 (and it makes perfect sense as M is optimized for performance, not consumption).
If more downforce is asked, it comes with a price tag of higher drag and additional spoilers/wings...
and yes, the basic shape has light front at high speeds (over 180 kmh let say), anyone on autobahn has experienced this phenomena when chasing a P911T I guess :-)
Vented hood improves the matters a bit, at least for me it has worked fine (the vents/louvers must be in the front section of the hood, where the low pressure area is, not at the rear where is the M3 intake opening and people have feelings that it ventilates the engine - in reality it does the opposite).

I know with the m3 they have a front vent on the belly pan. Could something like that help or not really?

[tylerhart_21]

Originally Posted by Thumbie

That is a cool comparison.

So from what I am gathering, and assuming you are talking about downforce per streetpro's comment, adding a little downforce to the front would be my first step.

I personally am considering swapping to M3 front bumper or adding a like a lip/dam. Next would be rear spoiler or, and I haven't done research yet, cutting up the rear bumper to relieve pressure buildup (this is common on miatas).

From there you could get into more advanced things like vents in the fender and brake ducting, etc.

With aero on the car would the aerodynamic kit work from bmw? I can see the front lip doing something but the rear diffuser and the spoiler I am not sure about.

[Thumbie]

Originally Posted by tylerhart_21

With aero on the car would the aerodynamic kit work from bmw? I can see the front lip doing something but the rear diffuser and the spoiler I am not sure about.

Depends on if they were designed for "style" or function. I am not familiar with bmw's aero kit. If it is BMW brand I assume there is some function there. For example the M3 rear bumper has built in diffuser. that vent above the exhaust tips does serve some function.

Overall the key is a balanced setup, obviously. Adding a massive spoiler to a non-M will give you too much rear downforce, you would also need front air dam or something to balance it out.

Depends on what the goals are for the car.

[streetpro]

Again, it depends on the definition of a massive spoiler. Because the rear wing on the trunk lid may reduce lift, it is rarely able to generate significant downforce because it is in the area of the swirled air. That's why DTM/GT cars have wings on high struts to get them into a "clean" airflow.
A splitter on the front will definitely help, both to increase downforce and to reduce drag (under certain conditions).
The lower openings in the front part of the engine cover allows a much higher flow through the radiator (the pressure difference between the part in front of the car, where the air is in positive pressure, while behind the radiator, through which it is slowed down and is further sucked under the car by faster moving air/low pressure zone - Venturi effect).
That's why M cars put transmission coolers etc in there, which would otherwise have to be in front of the water/air cooler.

[tylerhart_21]

Originally Posted by streetpro

Again, it depends on the definition of a massive spoiler. Because the rear wing on the trunk lid may reduce lift, it is rarely able to generate significant downforce because it is in the area of the swirled air. That's why DTM/GT cars have wings on high struts to get them into a "clean" airflow.
A splitter on the front will definitely help, both to increase downforce and to reduce drag (under certain conditions).
The lower openings in the front part of the engine cover allows a much higher flow through the radiator (the pressure difference between the part in front of the car, where the air is in positive pressure, while behind the radiator, through which it is slowed down and is further sucked under the car by faster moving air/low pressure zone - Venturi effect).
That's why M cars put transmission coolers etc in there, which would otherwise have to be in front of the water/air cooler.

So in short if you get a gt style wing it will be able to generate downforce, while a spoiler may reduce lift. The front splitter would help, when it comes to certain situations. Now with the vent on the engine cover, it helps with air flow thought the radiator etc. Correct me if I am wrong but would that help the radiator become more efficient or make it able to take in more air? So lowering oil temps?

[tylerhart_21]

After looking at the 918 Cayman gt4 MR, I have seen the underbody aero. Manthey racing and Porsche will sell you the aero parts but it’s 250 dollars. What does the underbody aero do?

According to Manthey:

1. Guide air out from underneath the car
2. Avoid to get air in from the side of the car

The first point is probably clear, the second one means that by creating a “air curtain” underneath the side skirt will avoid “dirty” air to get under the car from outside.

The aero could be more complex with getting the angles and the placement as well. However I have made a prototype with paper and duct tape and have someone that is measuring the MR fins to get the length close. I will keep y’all posted, but if y’all have any comments to add or suggestions let me know.

The aero on a gt4 soon below:

[tylerhart_21]

After some testing, the rs aero is not the most practical thing right now. I have made a some prototype based of the gt4 aero. The goals is block off the diviet behind the wheel and push the air to the side skirt. If anyone knows more about this topic let me know. I have attached the prototype and the small divet.

[tylerhart_21]

Does anyone know how much the front air dam from BMW (aerodynamikpaket) reduces the lift in the front? The Alpina b3 front air dam dropped the lift by 30kg. But I'm not sure about the Aerodynamikpaket air dam since it is a different design.

[streetpro]

The airdam and splitter will reduce the pressure under the front of the car the most (the airdam blocks the excess airflow under the car, and the splitter adds a force vector that acts from above - for simplicity we can call it front bumper overpressure). I dont have any exact numbers for BMW e9x aerodynamikpaket but it is not as deep as Alpina and mimics more the splitter, so similar or lower number would be my guess.
Everything I'm describing only results in a reduction of lift in the vast majority of cases, and at speeds above 150 km/h. If we're talking 70-120, where cars normally move around technical parts of the circuit, the gain is virtually minimal.
That GT4 kit was developed on a specific model according to the tunnel flow, moreover lower compared to the production e90, so the idea to implement on our platform is good, but the benefit will not be great.
For it to work, the e9x would have to be lowered, with a smooth floor, some form of side screens/stoppers and a functional rear diffuser (this needs to have a large area, small angle and smooth transition, which is hard to achieve on a production model).

[rismo]

Felix did some great research:

https://www.1addicts.com/forums/show....php?t=2062194

[tylerhart_21]

After reading the thread, from my understanding it’s not necessary to do all the aero bits on a normal street car. But at higher speeds having more rear downforce will help with stability but too much creates drag. I haven’t looked into the videos or got one of the books, but Newman prefers having a balance (between front and back) and having the lift close to 0 or 0. With all that said having the underbody aero seems to be more helpful with the hope of keeping the look while having less lift and hopefully reducing the possibility of drag. Looking at Porsche it seems that they use some hidden aero bits on the gt cars. I have been looking to see if I could recreate the same diffuser below (from 991.1 gt3). The problem I see is the muffler and placement as noted above, to makes a smooth transition. I thought about using a Tesla model X undertray for the rear diffuser since it’s cheaper than the gt3 one. I added some photos I took of the Garage 42 racecar and it’s aero if anyone is curious.

[rismo]

Honest response:

I live near Germany and pushed the car many times beyond 300km/h.
On M-sport suspension with factory alignment and default e92 parts this was pretty stable.
When I made the car stiffer the car started to bounce above 240-250, however adding the JRZ suspension the car is now a stable.

Long story short, for stability etc the suspension on our cars is much more relevant / will have more impact.
On the other hand, I always support science and engineering projects ;-)

[tylerhart_21]

I have looked a little into the diffuser, however I think I will have to put it in the rear. This is due to being challenging to have a middle rear diffuser and make it flow well. I have made a mock up of what it could look like. The blue box is the area I am iffy about since it will trap air in that pocket. If anyone have any suggestions to make it flow better let me know.
(Ps. The same diffuser from a model s)

[335i54n]

Yeah, I have been thinking for a while about using a large PtFE or aluminum sheet to surround the muffler and rear section, as the rear bumper area is open and can easily add drag. I also think you should extend it to the subframe so air doesnt fill it from behind.

[tylerhart_21]

I have made a concept of what the diffuser would look like. This design I have made would work the best since it leaves room for the muffler so air can pass above or under the diffuser. I based the concept from the Porsche 718 diffusers (Shown below). The problems I am experiencing is getting the height I would need for the fins and getting everything working correctly. The fins are not terrible but I will need to get a standard size for them and the shape. Getting this into a proper item to mount up will be hard since I would want it to look oem plus and fit well. If anyone have suggestions, let me know since I am going into this without any experience! (Also I am a college student so the budget is limited)
P.S. Going to work on the air fins in the wheel well using garden siding.

[335i54n]

I don't think you need to worry to much about fins; the diffuser is going to do more for drag reduction. Porsche has a whole chassis air flow design into it, with the flat floor, etc. With all the openings (subframe, diff, suspension), fins won't probably do much.

[tylerhart_21]

I looked into the fins just to understand what they do. From what I was reading they help to manage the air flow and direction. Taking this into account having the fins beside the wheels would help with the aerodynamics. By taking the air from the wheels and forcing it to the sides of the car and not through the middle. Just doing this will be the better first step and from there have a flat diffuser. Once I have the base for the diffuser I can just change it and see what works and doesn’t work.

[tylerhart_21]

Not sure if anyone wants to attempt the side strakes as well but here are the measures I have down below. Two thoughts is having the strake go to the end of the bumper and round it similar to a 2005 vanquish or end them somewhere in the middle of the rear bumper. Let me know what yall think about those two different options. Also small side note, would material could I make it out of? The strakes will attach to the rear bumper holes and I don’t want the strakes to melt or melt the bumper.