E46 M3 Track car mega build & development

[alexk]

Very nice and very nice car !

The aero / cardboard looks/feels a bit ridiculous, but that's just my opinion.
I don't see how these bits of cardboard (which flexes) gave you an 8 second advantage.
Could it be a psychological boost ?

[alclark]

I was also skeptical, I won't lie. But as I mentioned, there may be a placebo element to it making me drive faster - however the lap times obviously are a scientific comparison.



That said - Dave is a lead chassis dynamic engineer for a major sports car manufacturer and this is not an uncommon thing apparently when prototyping new cars because it's strong, very cheap and very adjustable, and very effective. A small 2" flat splitter can offer nearly 80kg of downforce. A gurney flap could add 140kg's. It's amazingly effective. Think how difficult it is to wave your hand when you put it out of the window, even at 50mph.



This picture is one of the few shots I have of it travelling at any significant speed with the aero and you can see even at 80-85mph the front splitters are barely bending. Downforce seems to be a very simple thing to do, but very difficult to master. The tiny little lip spoiler on the M3 flat bootlids contribute an amazing amount of downforce.

He's better explaining than I am to be honest, I just drives' it.

[chrisburns]

Originally Posted by alexk

The aero / cardboard looks/feels a bit ridiculous, but that's just my opinion.
I don't see how these bits of cardboard (which flexes) gave you an 8 second advantage.
Could it be a psychological boost ?

Alex aero is nearly always overlooked when it comes to car and likely because proper testing is so expensive but it without doubt makes a huge difference. I know what you mean about the cardboard but that would work fine as a rough experiment. You can see in one of the pics whilst the car is moving it is still in place.

Al, just a question. You mentioned there about how much work you had to do to remove weight and still you struggled to achieve the weight of a CSL. With hindsight do you think you might have been better off starting your project with a CSL ?

[alclark]

Originally Posted by chrisburns

Al, just a question. You mentioned there about how much work you had to do to remove weight and still you struggled to achieve the weight of a CSL. With hindsight do you think you might have been better off starting your project with a CSL ?

Yes and no.

On one hand, a CSL is a fully trimmed road car, four seats, a stereo, glass windows, air-con, xenons, etc. It has a much lighter exhaust system than me, lighter glass, lighter fuel tank and a few other trick parts which I think people genuinely underestimate how light BMW got the CSL, whilst keeping it a road car. Plus the SMG is a little heavier.

Mine is stripped out from the front seats back, and I still retain glass, air con and Xenons, but the significant difference is that I put probably 80kg of rollcage back in it, even though it was T45. So had I not caged the car, I might be around 1360kg, but my weight distribution would be all to cock. It's currently still 50:50 and perfect cross weight.

With a CSL, I would have a better and lighter base to start from, but I would not only destroy the value of the car but I would possibly still look at changing all the clever CSL stuff eventually anyway. Financially, I think it makes sense to start with the regular M3 base. So on the other hand - a CSL would have a lighter car to start with, but then add 80kg of cage, take out 50kg of seats, add 20kg of Recaros and runners back in, and then you're at square one again. Sort of.

A CSL shell at the end of the day is the same as an M3 shell, it's all the clever stuff BMW fitted to it that made it special.

[chrisburns]

Yes I know what you mean, I just wondered if doing it all again would you go down the same route.
As you say sooner or later you might end up replacing most of the CSL goodies anyway.

[Neil M]

Are you going for the elusive 400bhp?

A variation on the E46 chin spoiler as per:
http://www.ebay.co.uk/itm/BMW-E46-M-...81111080817%26
would/should provide you with some additional down force (back to the original M3 bumper)

[alexk]

My point has to do with the use of cardboard.

When I see/hear a downfore of 80, 100, 120 kg, I expect that if you put 80kg of weight on this cardboard flap it's going to hold it.
Because if it cannot hold this weight when it's static, it will not have 80kg of downforce.
I don't underestimate what a flap, extension etc can do, but it's critical for it to be properly attached to the car and do not flex whatsoever.

Try out the front flaps of a CSL to see how much weight they can hold.
They are strong and properly attached.

I am sure if you make carbon or polyester spoilers, the result will be realistic.
With cardboard, I seriously doubt it.

PS : the CSL has the same tank with the M3 E46.

[alclark]

I'm not informed enough to give a proper answer, but it's not just about absolute weight pushing, it's reducing lift and re-directing airflow.

The spats blocking the front wheels for example stop air running into the wheel arches, dramatically reducing lift. I also run without grills on the wings and vented arch liners to let more air out of the arches, pulling the front of the car down.

And, as we've proved from the picture, even at 80mph the splitters are not bending. It's mega cardboard, not your normal 2 ply. Remember it's only very basic, experimental guesswork, it's just a bit of 'lets try it and see what happens', but by someone who does this for a living and know's what he's talking about. Combined with just general racing tricks, we should get some good results with a bit more testing, then we can build it properly.

I was always under the impression the CSL tank was a thinner lighter item, every days a school day!

[alclark]

Originally Posted by Neil M

Are you going for the elusive 400bhp?

I'm not entirely sure what's involved or what on the engine loses relability (if any!)... I think once the chassis is developed fully then I'll start looking at increasing the power.

One thing's for sure though, I won't be going to Thorney for his "400bhp" after what I've seen.

[shimmy]

also to bare in mind is for the Ring the cars have to remain TUF ( i thinki thats what its called) and with big wings you get puuled and thrown off. Happened to SamT last year.

I persoanlly would love to take the CSL aero a step further. I bought my spare front and rear bumper for just that purpose. Im sure a good aero package would add to grip levels.