Aerodynamics of our cars

[ribs]

Guys, I notice something strange about my car. on my way to work on this backroad, there is this sudden drop in the road, and in all three of the rental cars I have had since I have been working here (when I was getting one of my two other cars fixed), in my little sister's neon, and in my dad's probe, if I hit this drop at 50 MPH, I will catch a foot or two of air. At 60 MPH, I will sail.

In my 951, I can hit this drop at over 70, and the car never feels like it is even thinking of leaving the ground. No air whatsoever. Are huge amounts of downforce created by this car, or are the anti-lift measures such as the rear valance and the spoiler at work here? If there was a fair amount of downforce created, it would explain why the toyota corolla rental I had a ways back felt like it was going to fly off the road in the middle lane of a 3 lane freeway at 107 MPH (thats as fast as it would go) but my 951 felt ROCK SOLID at speeds approaching 170 MPH (what ever redline is in 5th gear) on the couple of occasions I have taken it to those extremes. Has anyone else noticed the solid feel of these cars at high speeds, and their inability to catch air where most other cars could?

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ribs, 86' 951

[MAS]

Yes I have too. Even though I only have a "lowly" 87 924S, I've noticed that above about 80mph the car's whole feel changes. Whereas most cars I've owned start to get noticably less stable and lighter feeling in the front end as 100mph approaches... the 924S seems to feel even more glued to the road... I'd swear that it even feels like it's crouching down slightly

-MAS

[MOPARfag]

The reason they do that is for mopar, not for handling.
At very high speeds in your 951 it is made to go in a straight line, but incase there are any hills or bumps on the strip you are dragging, the car will not fly and lose speed. Porsche didn't make the 951 a MOPAR for stupid reasons, you know.

[MOPARfag]

Now let me get this straight, all you 924S and 944 guys, are just MOPAR wanna be's? The 951 model is for MOPAR, get that straight.
Only EURO944s can try to be MOPAR.

[mideastmafia]

now tell me.. why were you going over a dip in the road at 170mph? STOOPPEEED.

cool it mang.


SHAUN

[AMCPorsche924Powerhaus!]

Originally posted by mideastmafia:
now tell me.. why were you going over a dip in the road at 170mph? STOOPPEEED.

cool it mang.


SHAUN

Thats what MOPARS do dumbass, if you want a car that handles well go get a Porsche.
Oh, wait, that doesn't make sense does it...hmm..whats going on here?

[ribs]

Originally posted by mideastmafia:
now tell me.. why were you going over a dip in the road at 170mph? STOOPPEEED.

cool it mang.


SHAUN

NO NO NO. I didn't go over over a dip at 170. I went over a bridge at 170. And I probably won't do it again until I get me a 200 mph+ car.

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ribs, 86' 951

[TheStig]

I caught air once in my car by mistake, cause i had to get my cousin to the hospital for slicing his arm open while working underneath his 951.

took an incline at around 60 when i shoulda took it at 40, front wheels lifted up, and rear ones next, didn't land on my front spoiler luckily and no tie rods bent or suspension damage...pure luck i guess...



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Porsche. Es gibt keinen Ersatz.

[1.2gees]

I don't think it's JUST aerodynamics, I think it's also (little) unsprung weight at work. Suspension travel is also quite large, able to follow the dip in the road much better then something with more unsprung weight, and less travel would.
Ahmet

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It's all the driver...
My page over1g@hotmail.com
Porsche owners Gallery.../My 944

[AMCPorsche924Powerhaus!]

In comparison to other cars then, the 944 has softer, longer traveling springs (the longer and softer the more they take out the dips) then Ahmet????

[Blackfoot]

the ride quality is mostly determined by shock stiffness, not spring stiffness. the stock 944/951 shocks are sporty but not particularly stiff. that's why our cars ride so well.

in comparison, my vr4 shocks are a bit stiffer (especially in the "sport" mode), and the 951 actually rides better, even though the vr-4 weighs in at 3800 lbs!.

[AMCPorsche924Powerhaus!]

ya but don't the springs take out the big dipps, the shocks are for the little vibrations?

[Blackfoot]

springs control ride height & body lean, and do play a part in dampening. shocks dampen road irregularities and try to keep the tires contacting the road at all times.




[This message has been edited by Blackfoot (edited 07-14-2001).]

[fty]

Since I put the eibachs on,250lbs,the car rides smoother but the front does seem to loft abit goin over hills...but its allways the rear that steps up....but I have noticed that the car sits lower 90+ and feels extremely stable...even when riping across lanes...car acts like a touring car and feels like a true rally car in the country...its a nice mix....

[1.2gees]

AMC, one of the characteristics of the torsion bars is that it'll take more and more force to twist them, as they're loaded (until a certain point ofcourse). That is why I say particularly in the rear the travel is quite large.

Blackfoot's post explains the relationship between shock/springs. Harder springs will help the car's lateral acceleration in a paved, smooth circle (AKA skid pad), where theoretically shocks (that don't bind) will not. Ironically slalom speed is effected primarily by the shock stiffness (if we assume everything else is the same on a given car).

The shocks and springs work together on every road imperfection, both small and large. Shocks don't really 'absorb' the shock, quite the opposite actually... They transmit more of the shock to the car body, then a given spring would by itself over one bump. However it's important that the suspension resets itself for the next turn (or bump, or dip) and also the tire/wheel is kept from bouncing by the damper. The shock converts the energy stored in the spring (when it's not at it's neutral position) to heat in the shock. It's important to have good shocks, because they can help keep the tires planted to the road at a higher % of the time, which improves handling/acceleration/braking (and feel).
Ahmet

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It's all the driver...
My page over1g@hotmail.com
Porsche owners Gallery.../My 944

[AMCPorsche924Powerhaus!]

were talkin about flying over bumps though right....cornering and lateral accel is a whole different scenario here than flying over bumps. so my guess would be that a stiffer suspension on the car would actaully fly off the bump more than a softer suspension.

Take for another one of my "stupid" examples.

Going down a ski run, keeping your legs straight, you hit a jump. You fly right off it and hurt your lil a$s.
Do it again bending your knees this time (shocks), and when you hit the bump your knees jumble a bit and you go up and down but this time you don't fly off the jump, you stick to the ground more and don't get nearly as much air.
SO, I would think a good stiff macpherson/torsion suspension on a car would allow you to get mroe air than say a monte carlo family car with soft springs and soft shocks, the monete carlo would flop and woddle around putting all the absorbed force into movement of the shocks and not get air i would think.

Here's another bash about porsche for you to with the suspension,a good wishbone set up handle bumps much better for better ride.
But then again porshe doesn't really care if the ride is stiff.



[This message has been edited by AMCPorsche924Powerhaus! (edited 07-15-2001).]

[bill*924s]

Whem I took my '86 944 from L.A. to 'Frisco, I went up the 101 because it was a lot more senic than the 5. Around Ojai, the gentle, rolling curving road got the best of me and I started goosing the cruise control up until I was at 115. I could actually feel the car settle down and the steering tighten up. It was kind of a rush to go that fast and actually be in a car that wasn't raising up and feeling squirlly. My old lady was asleep and she finally woke up and looked around and asked how fast was I going. I told her 70 and she told me to slow down before I got a ticket and quit driving like an idiot. The fact that she believed I was going 70 should tell you how smooth the ride was at 115. I'm glad I finally got rid of her and was able to enjoy the 944 without her. But alas, the poor car was murdered one rainy night on the 405 freeway by a "undocumentated" worker from the south.

[fty]

those bastard southerners jokin...

[Brandon85-944]

this may seem dumb...but what is MOPAR?

[bill*924s]

It's now known as DaimlerChrysler.