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      01-27-2020, 09:26 AM   #1
MarcoZandrini
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Recommendations to increase front downforce

Hi to everyone!
I track my car at Virginia International Raceway (VIR)and at Summit Point Raceway. I typically run the front straight at VIR at over 125mph (4th gear). I notice that the steering becomes rather light at that speed even though the car is in the "Sport+" mode. Other than PF-08 pads, the car is stock. Tires are 18" Michelin PSS. Any suggestions or recommendations to increase front down force?

Thanks!
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      01-27-2020, 10:30 AM   #2
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Quote:
Originally Posted by MarcoZandrini View Post
Hi to everyone!
I track my car at Virginia International Raceway (VIR)and at Summit Point Raceway. I typically run the front straight at VIR at over 125mph (4th gear). I notice that the steering becomes rather light at that speed even though the car is in the "Sport+" mode. Other than PF-08 pads, the car is stock. Tires are 18" Michelin PSS. Any suggestions or recommendations to increase front down force?

Thanks!
The traditional route to increasing front downforce is via aerodynamic aids such as vented hoods, dive planes, and splitters. The first item below is an example of a vented hood; below that is a photo showing dive planes and a splitter on an E36 I owned.

If I needed more front downforce, I'd start with dive planes. After that, I'd go to a vented hood; however, if cost was paramount, I might choose a splitter ahead of the vented hood. Living with a splitter on the street may not be much fun, though.

This is a vented hood that may fit our cars: https://www.aeuroplug.com/collection...er-vented-hood.



The photo below shows Bimmerworld's CF dive planes for the E36; more on them here: https://www.bimmerworld.com/Body-Aer...es-E36-M3.html. I doubt there are any dive planes made for our cars, so you'd need to go to a shop that would fabricate them for you out of aluminum. That won't be a big deal for a qualified shop.

The splitter in the photo was made out of MDO by my shop. More on MDO here: https://www.andersonplywood.com/mdo-...nsity-overlay/. That stuff is heavy, but it's virtually waterproof, and it's easy to create a bullnose on it with a router. Besides, our cars are already tanks.

The splitter's turnbuckles ensure that it remains in position no matter how high the speed. You should be able to stand on a splitter without it flexing at all. A flexing splitter results in it not only not doing the job it was designed for, but it creates quite a bit of drag as well.

Note that you'd likely put a much shorter splitter on an F22 and wouldn't need turnbuckles. The splitter in this photo was adjustable in length from 3"-9", and that's why it's got turnbuckles.

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Last edited by dradernh; 01-27-2020 at 10:37 AM..
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      01-27-2020, 10:37 AM   #3
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Sounds like you want to eliminate lift, not generate downforce just yet. The typical ways (in this order):
- drop some ride height
- add more rake
- add an air dam, then splitter, then canards.

That said, once you get rid of lift, it's uncommon to add downforce, when optimizing for the straight. It's just extra drag that doesn't help your top speed.

I think you have two options:
- live with it :-) you're going in a straight line, you don't need responsive steering.
- switch to a height-adjustable suspension (coilovers) and drop a bit of ride height. Bonus points, you have a better suspension now -- that helps with more than just the straight.
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      01-27-2020, 10:42 AM   #4
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Quote:
Originally Posted by msendit View Post
- drop some ride height
- add more rake

- switch to a height-adjustable suspension (coilovers) and drop a bit of ride height
This is the route I chose, and I don't experience any lift at 140 MPH. It's more or less the standard way to get a car ready for track duty, and these mods would normally be done before any aero mods.
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Last edited by dradernh; 01-27-2020 at 11:28 AM..
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      01-27-2020, 12:04 PM   #5
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@ 125mph going straight I don't feel any lightness. ('15 235, mpss, AS+3, 4s)

@ 140mph in turns the front is sketchy, the M4 lca upgrade up front seems like a great idea
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      01-27-2020, 02:40 PM   #6
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What about these: https://www.turnermotorsport.com/p-5...m-upgrade-kit/? Add 0.5 degrees of caster.
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      01-27-2020, 03:51 PM   #7
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Some excellent threads in the suspension section
https://www.2addicts.com/forums/show....php?t=1683504

Search and Read through all the LCA posts cause car handling and feel are subjective
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      01-27-2020, 04:00 PM   #8
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Quote:
Originally Posted by ScottSinger View Post
140mph in turns
I'm impressed!

Where were you able to go this fast in a turn – do you have any video of it?
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      01-27-2020, 04:57 PM   #9
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Quote:
Originally Posted by dradernh View Post
I'm impressed!

Where were you able to go this fast in a turn – do you have any video of it?
I did not have a dash cam at that time

It’s funny the RACE TRACK I was on perfectly matches Interstate 83 in Maryland between Hunt Valley and the Pennsylvania border.

This part of the Track turn matches perfectly the bend before the last exit on the Maryland portion of 83 heading north. I would need to go back up there and find the exact turn.

It was a gradual bend, but as I ever so gently turned the wheel I also was gradually letting up on the gas and the car started to slightly push I think, I wasn’t comfortable cranking in more steering.

Was probably 140+.
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      01-27-2020, 05:53 PM   #10
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Quote:
Originally Posted by ScottSinger View Post
I did not have a dash cam at that time

It’s funny the RACE TRACK I was on perfectly matches Interstate 83 in Maryland between Hunt Valley and the Pennsylvania border.

This part of the Track turn matches perfectly the bend before the last exit on the Maryland portion of 83 heading north. I would need to go back up there and find the exact turn.

It was a gradual bend, but as I ever so gently turned the wheel I also was gradually letting up on the gas and the car started to slightly push I think, I wasn’t comfortable cranking in more steering.

Was probably 140+.
I can relate to all of that.

I ran my V70R up to 152 MPH very early one Sunday morning on the A7 between Hanover and Hamburg in Germany. It was on a stretch with no traffic and a very slight incline – it took miles to gain the last few MPH.

Like you, I did my best to minimize steering input during the sections that weren't perfectly straight.
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      02-24-2020, 05:28 PM   #11
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So i had a APR Chassis mounted front splitter on mine. That paired with NT01's, the front end hooked up pretty well
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      02-27-2020, 02:43 PM   #12
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you need to lower it, springs at least, and get real rubber.

I hit straights at 140 with no issues. I maxed out 7th to 176mph and had a little bit of movement, but i was also in mexico on a bridge...
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      03-01-2020, 08:48 AM   #13
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I have hit higher speeds on track without issue. I have much stiffer suspension, and is sitting about as low as reasonably can for street driving.



For one, it sounds like you need to look into at the very least, lowering the height of the car, and stiffening your suspension. Can be done using Dinan or similar springs if not wanting a full body coilover. I'd then look into better tires, and LCA/TS bushings, weather OE F8x or aftermarket using the original arms.
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      09-05-2020, 11:43 PM   #14
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I picked up a cheap "carbon fiber" air dam on eBay, mostly because its the only one I've ever found for the non-m 2er and wanted it for cosmetic reasons. But upon unpacking it, I noticed that the bottom of the dam is not flat. It's just open on the bottom with a void all the way to the top contour where it mates to the bumper. Would that cause a turbulence/lift issue? If so, what could be done to flatten it out, such as mating a splitter to the bottom? Any good off-the-shelf "universal" options? Or is that normal for an air dam and I'm reading too far into this?

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      09-13-2020, 05:59 PM   #15
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Get some plywood and chassis mount it to the front bumper or crash beam supports.

Paint black when done.
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