ozzy

Wasn't there an F1 car back in the 70/80's (??) that added some rubber skirts to the side to keep a tight seal on the track.

David, your car might end up looking like a hovercraft

Stefan

carl

Most of them did eventually, but I think the one you're thinking of is the Brabham with the movable skirts. They also did the 'fan car' which literally sucked the car onto the track. Gordon Murray designed both, IIRC

David_Wallis

Oh and its not a wind up... [img]images/smilies/mad.gif[/img]

all I wanted was the speed rating..

Im not saying it will do 200mph..

the car is geared for 194mph.. I want my tyres to be safe enough for me to try..

If you really think im joking about the engine, then mail me per profile for the spec or look in the projects section.

David

Pavlo

As has been said before, and echoed in the true grip article that Fuzz has posted, wings and diffusers etc CAN REDUCE DRAG AND DECREASE LIFT SIMULTANEOUSLY.

Please give some examples of cd for modern cars to show how 0.35 is so poor. IIRC a mark 2 escort (real shed) is circa 0.45 and a Caterham is awful too (but low area). F1 car is about 0.7 due to the open wheels and aero aids

No this isn't a wind up.

Testing at 125mph is quite good, although Mira has no moving ground plane which will influence things a little. You could scale up lift in line with velocity squared, although this isnt strictly correct it's going to be quite close (cd and cl can change with speed due to changes in flow regime,).

Not suggesting it's easy, but most definitely possible.

Carl, you have seen a R34 skyline haven't you?

Paul

ozzy

David, take a chill-pill m8

Just ignore the doubters and stop taking things so seriously

As I said on you first reply, all the manufacturers reported their highest rating as the ZR. It's fitted to the AMG Merc, which happily did 201mph on a set of 18's.

I think you'll be safe with those, given it won't be a long run at those speeds.

Stefan

carl

Audi 100 was the first car to achieve 0.3 Cd -- and that was 20 years ago...

I don't doubt the engine at all. I doubt the aero. That's it.

BTW I could gear my 218bhp UK00 for 194 mph -- doesn't mean it will do it though
You need to gear for maximum power at maximum road speed.

[Edited by carl - 3/17/2003 11:53:30 AM]

Pavlo

Exhibit A

carl

Nice stats! (Some more cars would be appreciated though...)
Find it hard to believe that a Boxster is 0.31, because it's a convertible

How many of those cars have variants that do >170 mph? Corvette Z06 (0.29), BMW (M3 -- 0.31), Viper (0.35 -- low ride height and little frontal area?), 911 (0.34 -- but the fast ones have completely different aero), XK8 (0.35 -- but again, low frontal area).

[Edited by carl - 3/17/2003 12:05:05 PM]

David_Wallis

600+ bhp should be available by 6500.. I still expect to be holding 500+ at 8000rpm

Apparently inlet tract is too long for real power.. but I expect there to be a few developemnts on that front soon..

David

Pavlo

It already is.

P20SPD

iTrader: (1)

Hmmm - Interesting

Steven (trying to remember what speed his wagon got to with 2 passengers, in approx 1 mile, with only 340bhp)

Hoppy

Pavlo/Paul, do I really deserve to be called an "ignorant gobsh1te" and an "idiot" for suggesting that attention to aeodynamics rather than pure bhp might be the best way forward, here? If I do, I apologise. If I don't, then perhaps would you?

I was merely responding to your assertion that "with enough power, anything is possible" which I thought to be something of an over simplification when trying to get what is afterall an average family car to do 200mph.

Best regards,

Richard.

David_Wallis

I think paul was joking / jesting

David

Pavlo

Yes, sorry richard, I was having a rage moment. My paticular annoyance was that you seem to have identified "the usual theorists" on 22b, well, the post you refer to was written by me. I have the cuts, bruises and breaks to show for being practical too. I also studied fluid mechanics and ground vehicle aerodynamics at university, although a while ago, I don't think the physics has changed in the meantime. The sobjects are not so complicated really either. They hinge around a few basic theories (theory being something as yet not proved wrong) and the GVA side of things is very subjective, concerntrating on the nature of the flow phenomena rather than the exact maths within.

Reducing cdA for top speed is of course an good route, but we're not playing with minis here, so a 4" roof chop is off the cards I think (although David may have other ideas!). Given the constraints of a Standard shell with aero aids for the benefit of reduced drag and/or lift, increases in power are somewhat more readily understood and available.

I think a day at Mira is something like £1300 (maybe that's a half?) so it maybe beneficial for like minded people to do some common testing of stuff. My own personal feeling is that a partial undertray and rear diffuser would help the cd of the car, whilst generated a fair bit of downforce to reduce the lift.

You also have to realise, that the quoted cd figures for production cars are not always what they seem. For instance tt has been said to me that the Calibra cd figure (0.27?)was gained with no wing mirrors!

Something like a 200sx or turbo Calibra may well be what is required for the best top speed run campaign, but we are dealing with Imprezas here (well, I've got a legacy but that's by the by). The maths says that over 190mph is definitely possible from a power perspective, getting good stability is important also, I agree. Given that I've been at around an indicate 170mph in a Uk Scoob wagon, I didn't feel stability was a problem at that speed. Perhaps the uprated suspension and lower sidewalls helped (they should) but my gut feel is this is certainly possible. Real, incremental testing may be required, but it can be done.

For all the talk of 'slippery' cars, I have seen very little made of the fact that Ronnies skyline did 207mph on a seperate occasion at Elvington. Ronnies car had a measured 680bhp at the hubs at Abbey, somewhat less on the road (tyre losses). If you have seen a skyline you will appreciate that while the basic form is low and long, it's also VERY big, has some hideousness at the front, has wide tyres and overall will need a lot of power for very high speed.

I don't really like to spurt maths and figures, but if we to form educated views on what can be done, and how to go about it, we really need to have hard facts at our disposal.

Paul

carl

Indicated 170mph. Take of 10% speedometer error and you have 153mph. No way can you scale up that experience to going at >190mph.
But it does have a completely flat underside, and Nissan obviously intended it to have >280bhp and do >112mph. I don't think it's particularly wide, is it? Long is good

BTW a Cerbera will do >190 with ~350 bhp, but if you look at one you'll see it's not very tall at all.

Useful way to work out frontal area is (overall_height)*(overall_width)-(overall_width*ground_clearance)+2*(ground_clearan ce*tyre_width). If you do a search for a program called 'cartest.zip' (I think this is it here) you can put in all your Scoob's parameters and it will tell you the Vmax (amongst other things). I've been fiddling around with it for some time, and it gives pretty accurate figures for most things. It doesn't have a Scoob's parameters, but I have the figures for a UK MY00.



[Edited by carl - 3/17/2003 9:46:33 PM]

Hoppy

Paul Appreciate your comments. Thanks.

Richard.

carl

In answer to the original question, Y-rated tyres are good up to 186mph. I think past that you have to take your chances -- most 200mph cars have specially-made tyres (e.g. the PZero N series for Ferraris).

Bob Rawle

Practically speaking the Impreza is actually pretty stable at just over 170 mph ... least the STi5 is however attention to alignement and geometry is essential.

I think the P1 bumper/splitter is actually worse for drag than the std STi5/6 bumper and STi6 splitter. Thats just my perception though based on the increased surface area thats presented..

Pavlo

Carl,

I would expect less than slightly less than 10% speedo error, the tacho told a similar story based on gearing. But then it's hard to know as the speedo needle was on the stop I think.

I know some of at least one wagon that has done very close to 180mph, still accelerating IIRC.

Paul

Tim W

iTrader: (1)

FWIW my car felt very stable at Elvington when I hit 166.6

Stock MY98 UK shell with Leda, 215x40x17 S02's on 7.5x17 rims.

Bonnet lift was alarming though, may have a cure for that this year, without loosing too much cooling effect

P20SPD

iTrader: (1)

This is really interesting guys, keep it up.

Steven

carl

When the P1 was released, I remember Prodrive announcing that the front splitter/rear spoiler combination meant that it required 3 bhp less at 100 mph than a standard UK model. Would be interesting to see how it compared to an STi5/6. I wonder if someone from Prodrive would be able to comment?

Pavlo

I don't think it matters anyway.

David's car will pull so hard it will dissapear in a trail of flames when it hits 88mph...

In fact david tells me he already reached 192mph next August..

paul

David_Wallis

ROTFLMFAO..

David

Oo.. nearly in tears laughing so much.!

P20SPD

iTrader: (1)

ROTFLMFAO

Paul you obviously have the "Wit" chip in today Brilliant, absolutely brilliant.

Steven

David_Wallis

top

Pavlo

http://www.google.co.uk/search?q=tyr...-8&hl=en&meta=

First hit

David_Wallis

seen that but doesnt really cover 190???

Pavlo

indeed, not sure about 'ZR' on it's own, as that's just 'over 149mph' but mentions no top limit. Worth noting that the ratings refer to sustained top speed. I also doubt that as you cross the threshold from 190 to 191mph the tyres will suddenly explode.

Paul

David_Wallis

no... true... but of course that wont happen as I cant do that speed..