O boy Now youz guys.., get to work on.. Options

[J P Stein]

my unstable 914.

A reprint:

I could use some input from those who spend some time at 100+
in their 914s. At my first ever track day I found the car really started moving around (I mean REALLY) at these speeds. The back end would just move over a foot or so in both directions

Toe? Aero? I'm clueless. My AX set-up slew em' in the twistys, but gave it back when I had to stop gassing it on the straights.

-2 camber at both ends, 1/16 toe in both ends, 5 deg caster at front, LE spoiler in front, nuthin' in the rear, big stickeys at both ends.


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OK, git to it. (IMG:style_emoticons/default/laugh.gif)

[ArtechnikA]

I could use some input from those who spend some time at 100+
in their 914s. At my first ever track day I found the car really started moving around (I mean REALLY) at these speeds.

we really need to hear from the racer guys, i've been holding off posting until they checked in - but it's been 12 hours so nevermind ...

i used a snowplow front spoiler, nothing in the back. with and without rear antiroll bar, didn't seem to affect straightline stability.

it would help a bit to know the road surface - it might sound a bit like you're oversprung and underdamped, especially in back. (if this is happening over a smooth surface, nevermind...) maybe a bit more rear toe-in. more caster would help your straightline stability too - try for 6 but my guess is 5 is all you've got available to you or you'd be running more without my telling you this ...

could be a few things, but what it -really- sounds like is something's loose. i ran DE's in both my cars at tracks with l-o-n-g straights - like the old 1+ mile CanAm back straight at Riverside, f'rinstance. solid 130+ there, close to that at Holtville with its 4500' straight, bumpy as the dickens besides. never encountered anything i could call twitchy or darty. takes more HP than i ever had to run 140+ where the rear end -might- get light - but go have a look at the 914.6 GT's on the Mulsanne at Le Mans with their 210-HP 906 engines -- they never ran with a decklid spoiler...

a bigger - more aggressive - deeper front spoiler/air dam might get you more planted...

let me pull out the 'For Sporting Purposes' white paper and see their recommended alignment specs - understanding they'll be written for bias-ply racing slicks...

oh yeah - how's your tire pressure ? not enough in the pack and you'll be wandering ...

best i can do off the top ...