Has your 944 ever "Bitten" you ?

[944Turbo]

ORIGINAL: zcacogp

Patrick,

That eMail reads as if he has full data from the car of suspension position with respect to time, as well as some pretty detailed telemetry regarding speed and GPS. What did you have running in the car at the time?


Oli.

IIRC from the build thread there is full telemetry on the suspension etc.

http://www.porscheclubgbforum.com/tm.asp?m=641531&mpage=5&key=&#683802

 

[zcacogp]

Tony,

Thanks - I hadn't read the build thread. (In fact, I didn't know it existed - it passed me by! I'll read it now.)

The crash will be all the more galling for the fact that it was clearly a big project, and biffed up on it's first outing. Very sorry to hear it Patrick.


Oli.

ETA: Just read the build thread. I'm slightly gobsmacked - that was a very, very dedicated 944.

 

[edh]

ORIGINAL: Neil Haughey

It's great to know these things but obviously would be much nicer for Patrick if it wasn't related to a heavy crash.

Something which stunned me yesterday was that EMC told me that on my car the rear helper springs were not fully bound and compressing the main spring when the car is sat flat. Honestly didn't notice it but of course it meant that as I was going through corners the inside wheel was only running on the torsion bar and a 4/lb inch flat wound helper. It literally only needed mm's of movement to lift off the main spring but of course looked sort OK as sat flat the main spring was under load. Also helps explain why it seemed like I had way too much rebound as of course its the spring+torsion bar that pushes the damper out. Also of course meant every time I braked heavily the same was happening, back end lifts and with only the torsion bars to pull the damper back out its like running with twice as much rebound. No wonder I kept smoking rears.

Patrick make sure the above is not happening on your car as I find it hard to believe that you have so little droop its lifting the rear inside wheel in a corner. On my car with the GAZs the rear droop is enormous, must be several inches.

If anyone suggests you can put coilovers on these cars again without reindexing, walk don't run, it's plain right dangerous thinking.

Next problem after having enough damper travel is having correct bump stops that come in before the springs bind up or the dampers bottom out which is not easy on these cars as unfortunately you don't get a lot of movement upwards on the rear once the car is sat with a nice low track spec ride height.

Neil I have re-posted your comment to this thread - track suspension and reindexing

 

[333pg333]

Thanks for all the kind words of encouragement guys. The whole thing is gutting indeed. I need to get a little distance from this before embarking on the rebuild.

Oli, the car has full Motec system with many different sensors. Each strut has a suspension potentiometer which gives all the movements in real time/distance. Wheel speed on all 4 corners plus all the engine and mechanical monitors.
Running on a Dyno Dynamics which is known to be fairly conservative compared to some others the tuner extracted 359whp at 23psi to the wheels running on Race grade E85. For fun he changed the ramp rates on the dyno and got almost 390whp without doing anything else to the motor. Just to show how these figures can be fudged. No matter, for a stock 2.5L internal motor (well actually an n/a block/head + turbo pistons and rods), bigger cam and GT3076 it's not too bad. Well into the 400's to the crank. Made me wonder just how much more I'm going to need the 3L racemotor??

Neil, you could well be right. Something isn't quite right and we need to establish all this before we turn another wheel in anger. To add to this theory you could say that having a largish front splitter and only hoop rear spoiler might have unbalanced the car also. Not to mention whatever that AlfaSud might have been dropping. I may never know the full answer but it would be nice to find something that stood out clearly rather than make suppositions.

 

[Diver944]

Hi Pat, I'd been following your horrible news on the Rennlist thread but reading and watching it again only backs up my gratitude that they build these cars so strong. Mine didn't have any of the rollcage or strengthening that yours has and it merely needed the left hand panels replacing and a new wishbone. I would hope that yours will be similar though I think my hit was a lot softer because luckily I was on a cool down lap. The amount your head moved to the left on camera was horrific! One thing is for sure - I bet your rebuild will be quicker

Whilst yours is being rebuilt and if you can stand it I would get yourself back out on track as a passenger with a trusted friend as soon as possible. Peter Empson over here took me out first after my smash and I was absolutley petrified (for about 1 lap, then after that I all felt normal again). Thank you Peter, it helped a lot []

I'm still trying to think of another bad motorcyle analogy for Simon but alas I can't [&o]

 

[944 man]

[]

 

[5lab]

heh, my 944 s2 bit me pretty hard last week. Going (evidently too fast) along a dual carrigeway in the wet, completely straight at about 70, hit a large puddle and the thing just went. Back end went towards the barrier, applying a full rack's worth of lock did nothing (pretty sure it was completely aquaplaning) so I just stomped hard on the middle pedal (figuring I didn't want it to grip again suddenly) and held on. did a 360 across both lanes, missed a barrier by about a foot and only started to decellerate when it got onto the wet grass verge. Eventually stopped by hitting one of those little mile marker things at about 10mph (it bent over a little bit), and the boot lid popped open

no damage at all to the car, which was very very lucky. travelling backwards at 70 towards a motorway barrier with no control is not an experiance I wish to repeat. I will say that at that kinda speed, with no grip, a crash lasts a long old time. The tyres seem pretty good - 4-5mm tread all round, but they are quite wide (215 and 235 section on 17s) and I guess the car is kinda light which doesn't help..

 

[Mike_Pollock]

Tread depth is one thing, but the age of the tyres is almost more important.
I'd get that checked.
Good story glad it ended well.

 

[5lab]

the car's new to me so I don't know the tyre age for sure - the last owner did fairly low miles in it (~5,000/year) - but I'd be surprised if they were more than a couple of years old. There's no sign of crazing or anything on them which comes with age.

They're generally pretty good and grippy even in the wet (the rear end won't break away at anything under 4,000rpm) but this was something different - everything went very light and quiet - like hitting sheet ice. From reading up on true aquaplaning (which is, thankfully, relatively rare), I think this is what happened to me..

 

[Neil Haughey]

Sounds like it. Most terrifying experience for me was on the M62 going over the Pennines when a sudden sleet storm came in, within seconds it coated the road in a rutted mess of a ice. This was late at night so very little traffic around but I slid over 2 lanes back and forth until the car slowed enough to keep it straight. Utterly terrifying.

 

[944 man]

Pat, if youd been driving the BMW I think that youd have got away with it, doing what you did. I suspect that the extra speed that you were carrying through the corner was your undoing and you cant do anything about that after the fact.


Simon

 

[Copperman05]

Sorry to hear of your crash Patrick, hope your not feeling too sore, looking at the video its certainly given me a lesson on how easy it could be to find myself in a similar situation. Fingers crossed car can be repaired without too much time and expense.


Edd

 

[333pg333]

Thanks to all you guys for such nice words and wishes. Very much appreciated.

Not wanting to hog this thread with my singular tale of woe, but I will add to it with more input from the Engineer as I suppose it's interesting to some.
I am getting very different reactions between 'camps'. By this I mean that the Engineer is basing his thoughts on the data provided and years of working in the field.
Other people have offered their theories and being highly inexperienced in these matters, I'm open to conjecture and opinion.

I bought the Moton suspension from a friend who is a reseller out of Sweden. They provided the 'kit' for a race 944/951 and he surmises that it would seem very odd to get inside wheel lift on a rear wheel drive car in such a long constant radius corner. Having driven this corner many times I'm inclined to agree with him. So he's thinking either brake malfunction, incorrect suspension installation, coil bind etc...
I mentioned this to the engineer who is only going off the numbers and this was his response. He also backed it up with Data from the lap before and the incident lap (on that particular corner).


Hi Patrick
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.
Attached Images

I can't seem to load the pdfs so if you want to see these screen captures you'll have to go to this Rennlist thread and see post # 578

http://forums.rennlist.com/rennforums/944-turbo-and-turbo-s-forum/656544-patricks-build-thread-it-runs-39.html

 

[944Turbo]

opposite front corner compressing could lift the rear?

 

[avenger]

not so much bitten as nibbled my nerve ends, yesterday on a nice sweeping stretch of road my tail wagged after hitting some standing water on a bend, on full boost in 4th. totally my fault as it was persisting it down but keeping my foot in kept it to a minmum, had i been in my old E30 Bmw i think i would have been bitten, chewed and spat out!

 

[DivineE]

I'm not counting Patrick's car because it's so far from standard it's barely still a 944 but I think tales of snappy handling in these cars can only come from age related wear on components and or bad set-up.

The 944 has been so forgiving to me I can't compare it to another RWD. I can think of numerous times I lost the back end of my non LSD car mid corner and carried on accelerating out of the bend regardless knowing the tail would wag around onto the next straight but always fall back inline with the front in the end. The 944 has in my experience an unrivelled ability to lose the rear end without upsetting the direction of travel. With the LSD equipped cars you have to treat the throttle with a bit more respect and ease off like a normal car but the 944 just doesn't seem to push the front end around like other rwd cars I've driven.

The only time I ever got caught bitten in a 944 was my very first lux when a local tyre garage said they had 'fixed the geometry that was out before'. I've no idea what they did but I always used to be able to lean on the rear end before they 'fixed' it and after that it was VERY tail happy!

I then made two big mistakes, first I drove the car in anger assuming the grip levels would be the same as I remembered them (I had let the tyres bed in, this was later), secondly I thought I could make back the ground I'd lost on the straight to the Caterham R500 I was racing by out breaking him into the fast, sweeping left hand bend. I felt the back end break away before I even got to the corner, looked down to see I was still at three figure speeds and understood the horror that I now had to turn in for the bend whilst already sliding. I backed off uncontrollably through fear but fortunetely held it so sideways for so long that I scrubbed off a lot of speed and by the time it wanted to snap back in line I was able to get back on the throttle to stop it allowing me to drive out of the bend without it biting back.

I was 18 at the time so not very experienced (although I drove constantly like an idiot so had some practice). I was very lucky and will never forget that moment but the car was very forgiving even then.

If you want to drive a scary car, try driving a Z4mc in anger!!!

 

[JamesBall]

Sounds like a lot of you guys need to check the age of your tyres:

"To check the age of the tyre look for the DOT number stamped on the sidewall of the tyre, it will look something like "DOT XXXX 3207" and in this example the tyre was manufactured during the 32nd week of 2007."

 

[SUSIT]

jeeze, some of you guys must drive to extremes! The grip available on my S2 makes me think need to hit standing water, oil or loose gravel before it would let go.

In the dry the speeds would be that high I would be scared sh1tless of getting seriously hurt.

Do have the tail out at the roundabout 200m from my house but its always slippy as the local buses seem to spill fuel there most days.

I find my S2 the most forgiving of cars,

now ask me how many times I spun this at the sprint

 

[nicksonmsport]

patrick, that impact was quite severe! hope you have a speedy recovery. with regards to repairing the car, i would not be reusing that bodyshell especially the roll cage. when a rollcage receives an impact like that, although you wouldnt think it, the tubes will flex and absorb the impact of the crash. roll cage tubes can return to the same position they were in before the crash with a sort of elastic motion. and although the cage may seen undamaged, the material can be work softened. this means if you ever crashed in the car again, the rollcage will not hold up so well and can collapse. if i can find the video i can show this flexing in an accident happening in slow motion. (my buisness is rollcage fabrication btw)

 

[nicksonmsport]

same goes for replacing the seat and harness as well.