Date: Thu, 20 Nov 2003 00:39:32 -0400
From: Dexter J <>
Subject: Re: Failiure On Track

Salutations: On Wed, 19 Nov 2003 18:00:11 -0000, **-** <> wrote: >> That round front windscreen should go a long way to keeping drag under >> control as you get beyond 160. But I would be concerned about the rear >> end lifting as you get into that range as I've always felt it makes for >> a >> vortex over the rear quarters and my overall take is that you may have >> to eventually lower the roof to make 170+ - but at that point you are >> back to square one on the belly math.. > > I'm hoping some refinements to the rear diffuser will kill the lift, > whilst the shape of the C900 is gorgeous that large rear end with its > steeply sloping hatch isn't much in aerodynamics terms. That's kinda what I was thinking about when I mentioned lowering the roof. If you get that last flat foot of hatch off but still retain the basic roofline angles - you end up with a very, very clean trailing edge to work on. I should more correctly have said 'chopped the rear quarters and front pillars to lower the roof'. But again - it will completely change how the underside is working - which supports your focus on max engine output. It's an interesting problem really - at the output ratings noted in your last post you want to keep as much leverage on the front wheels as possible to limit wheel spin. In the C900 this is naturally helped by the engine layout. On the other hand - as you don't have a lot a weight in the back to hold it all down - less as pressure builds up - you chance a nasty snap to the left or right if it gets turbulence under the machine and lifts the back up at the end of a straightaway or running high speed corners. Here's an interesting history that touches on the subject: It may be worth trying to google Chaparral Le Mans. Wading past the diecast silliness - there is some very interesting information on active wings and advanced down force designs they tried. I think they once even put in a snow mobile motor powering fans to try to control variations in down force. My take is that active suspension kinda solved half of the problem in that springs/shocks then work with ever changing effective total weight in real time so it 'handles' well enough to ignore most variations in pressure - but - unless you know an F1 guy from the early 90's with a wreck and an interest - you are unlikely to find anything applicable to the SAAB. It kinda all went into making Mercedes more comfortable over potholes. Crap and half - eh? >> Here's a link to a very interesting PDF on my server regarding a >> Mondello 403 Olds block build out that might be useful. It's not a >> great scan, nor a SAAB engine of course - but if covers some >> interesting oiling problems >> regarding high RPM builds. >> >> > > Many thanks thats interesting reading!!. A pleasure. That's what powers my other love - a fire breathing front wheel drive GMC 26 foot motorhome. I'll make a land speed run with her one day (har-har).. :) .. -- J Dexter - webmaster - all tunes - no cookies no subscription no weather no ads no news no phone in - RealAudio 8+ Required - all the Time Radio Free Dexterdyne Top Tune o'be-do-da-day En Vogue Salt n Pepa - What a Mighty Good Man

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