Porsche 944 turbo road to racecar.

[Cal]

I can get all the replacement parts in f/g but this would apparently disqualify me from Prod Sports.

What does that mean? I would have thought the car was way to modified for Prod Sports long ago. A class perhaps.

[Dave75]

That car was /is nowhere near 2F Compliant.

8"or 9" max rim width ,depending on weight...tyres...holes in the body...pedal location etc.

2F Regs are basically a direct copy of the 3J Improved Production Regs in Touring Cars.

Would have been wiser to read the relevant Regs prior to starting the build & build it to comply.

Very sad to see the "incident" though.

[JESUS CHRIST]

Damn! Bloody T1 at EC is evil and cursed!
All the best in getting it back on track

[333pg333]

2B or now perhaps Sports Sedans in which case the rules are way different. Nevertheless, I'm not so concerned about wheel to wheel racing at the moment.
Some feedback from the Engineer. Knew something was up.....


Hi Patrick
I’ve been analysing some of the data in more detail and what I have discovered is the following.
We have been using 45mm of rear damper travel at the track. This probably equates to around 70mm of wheel travel.
Unfortunately the car needs to have more droop travel through some of the higher G force turns. The inside rear wheel is lifting off the ground, this is the jacking effect that Paul was talking about, at the time we thought it was being caused by too much rebound damping and we removed some.
Factory setup have the droop controlled by the bolts retaining the outer torsion bar bush, your application probably has the rear droop controlled by a spacer above the piston within the damper so some damper or rear suspension setup mods will be required before the next outing.
If you look at the data particularly suspension position [position each corner in a new graph on the page] you will see that the lr suspension pots flat lines during some corners at around -22.
At this time the rear wheel is starting to lift of the ground and the rear will start to become unstable.
Your video also confirms this as you have to correct your line on entry , you were travelling 16 klms quicker than the previous lap and the gpsmap shows you wider on entry before the apex which all added to the event.
The rear end appears to be rolling more that the front but a more accurate measurement of motion ratios would be required before you could call this a fact.
Everywhere that the lr suspension starts to bounce off the full droop point is where you were complaining about a lack of rear grip so we need to rectify this before next outing.
If there are no spacers within the damper then we may need to get extended rose joints, Im a bit surprised that this has occured given that you bought the dampers to suit this application.
Mark
Rsport Race Engineering

[BigMuz]

That's shitty news mate.

Lifting a rear wheel off the ground is plausible and would make the thing awfully unstable but turn one wouldn't be the highest lateral g corner would it unless you had massive balls?

[ahabthearab]

Damn

I just came across this and bad luck mate, you seemed to be driving sensibly.
It seemed to happen very early in the corner, almost at the transition so I'd suggest low pressure on the outside wheel. Its almost to early in the corner for the inside wheel to be lifting

You already know you over corrected and on that note, one of the best things I bought for my car was a low ratio steering box. I know this is to late.

Hope it works out for you.

[Billzilla]

The limited travel thing on the rear wheels certainly could be the main factor.
I drove Nero's car at the Cootha Classic a few years ago and he warned me in advance about the same problem with that car. I could feel it happening as I drove it so I allowed for it but I could still feel it trying to move around.

[333pg333]

There is definitely a bit of head scratching going on from me and a few others who are familiar with this build. Seems very odd that there can be a wheel pick up on such a long constant radius corner and the suspension 'kit' was made for this model car. A few more bits from the engineer:

Please see attached screen capture. Unless the rear wheel managed to hold at exactly the same height for over a second on each of the three ocassions as you turned in I would beleive my comments to be correct. I think the wheel lifted on entry and you were a victim of the grip slide shimmey senario on entry to the corner which caused your mid corner correction and subsequent running wide on exit. I'm not saying that the rear shock has definitely bottomed out but something has definitely stopped suspension droop at that point, the most likely senario is that the shock has runout of travel but regardless the situation needs to be reveiwed to see what has caused the suspension to stop its travel and cause wheel lifting at that point.
Please note if you look at the capture you can see a similiar trait in the right rear shock as you leave the track at about the same level of droop.
The 'grip-slide shimmy' is when the rear end grips and then slides and requires steering correction to maintain line through the corner.

[gxxr]

A certain Italian make has torsion bars and is famous for lofting the front inside like an old Lotus Cortina when you uprate them. I think the fix, where there's no rules to follow, is to enlarge the upper wishbone aperture and fit coils around the shock, as no amount of pre-loading the bar, making adjusters and so forth will fix the compromises....and they're a darn sight easier to swap. As said though, little idea what's in a 944 rear. After 30 years you'd think the set up hot ticket would be well known.

Edit: Never can see attachments on this forum!

[Gammaboy]

A certain Italian make has torsion bars and is famous for lofting the front inside like an old Lotus Cortina when you uprate them. I think the fix, where there's no rules to follow, is to enlarge the upper wishbone aperture and fit coils around the shock, as no amount of pre-loading the bar, making adjusters and so forth will fix the compromises....and they're a darn sight easier to swap. As said though, little idea what's in a 944 rear. After 30 years you'd think the set up hot ticket would be well known.

Edit: Never can see attachments on this forum!

They still loft a front wheel with coils.

[BigMuz]

There is definitely a bit of head scratching going on from me and a few others who are familiar with this build. Seems very odd that there can be a wheel pick up on such a long constant radius corner and the suspension 'kit' was made for this model car. A few more bits from the engineer:

Please see attached screen capture. Unless the rear wheel managed to hold at exactly the same height for over a second on each of the three ocassions as you turned in I would beleive my comments to be correct. I think the wheel lifted on entry and you were a victim of the grip slide shimmey senario on entry to the corner which caused your mid corner correction and subsequent running wide on exit. I'm not saying that the rear shock has definitely bottomed out but something has definitely stopped suspension droop at that point, the most likely senario is that the shock has runout of travel but regardless the situation needs to be reveiwed to see what has caused the suspension to stop its travel and cause wheel lifting at that point.
Please note if you look at the capture you can see a similiar trait in the right rear shock as you leave the track at about the same level of droop.
The 'grip-slide shimmy' is when the rear end grips and then slides and requires steering correction to maintain line through the corner.

What is the highest G left hand corner on the track?

Does the RL damper flatline there as well? Do you have the full trace?

[youngy125]

If it's not running out of travel could the big bump at T1 plus excessive amounts of rebound dampening plus that side being unloaded explain it? Or perhaps something binding in the rear suspension?

[da9jeff]

pull the springs out and run it through the full travel, will tell you if its binding

[333pg333]

Yes, need to pull everything off the car and measure. Does seem odd if they have provided the wrong kit somehow. Wonder how I'll go getting compensation out of a Dutch suspension company that's been bought by some other outfit in the interim....yeah, that's what I thought too......

[gxxr]

They still loft a front wheel with coils.

One I'm thinking of just didn't swap from torsion to coil. Was noticeable better around Bitupave at Amaroo with the roll centre off the ground....moved through non complying means for the competition it was involved in, although OK to the casual scrutineer if I remember correctly!

Speaking to Rex Broadbent at the v8 round the other week where he was crewing for his old nav in prodsports, although better known as a rally guy now, quite an accomplished circuit driver. He mentioned he does a variety of Porsche set-ups, probably quickly tell you which way to go....but I guess there's still a way to go before it's working again.