1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

question about high speed stability

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Old 05-21-16, 09:52 PM
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Damn, it did start!

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question about high speed stability

As I understand it the first gen can create some lift at speed. at what speed does a stock rx7 start to become a little to light?
Old 05-22-16, 03:06 AM
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Not at 116...


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Old 05-22-16, 06:30 AM
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Waffles - hmmm good

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Mini gets light around 110 or so. Stock suspension suspension can make it worse.
Old 05-22-16, 09:51 PM
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Thanks, I used to have a Mazda urethane IMSA air dam on my 81, but for my 80 I want to keep it looking stock as possible. Just looking at limitations and hazards of top end.
Old 05-23-16, 03:54 AM
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.....bilsteins and konis on mine + 205/13s, if we are mentioning suspension bits equipment...

Stu Aull
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Old 05-23-16, 07:09 AM
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Waffles - hmmm good

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I'm with you on keeping the SA stock. I would jave put a duck bill on it ages ago to cure this if I went
that fast on a regular basis like at the track.
Old 05-23-16, 08:27 PM
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84SE-EGI helpy-helperton

 
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On my stock front end SA, lift started at around 100-105mph in clean air and no wind, and got steadily worse with steering lightness and drift at anything above that. I had the speedo regeared to show up to 155mph top end (unrealistic, but better than 85mph stock) and calculating error, the car was much more controlable up to about 115-120 with a Kamei airdam. Anything to keep the air from pushing up on the lower valence helped immensely.

The Mariah Mode4 likely keeps even more air from making lift on my -SE and a rear spoiler seems to help at high speed, too. I never noticed rear end lift, but theres a lot going on with the car at that kind of speed to pay attention to anything in particular.

Only do this speed in a straight line, as the cornering forces are very likely to unsettle the car.

*statute of limitations is LONG past on this one! I have no need to drive that fast anymore...

Last edited by LongDuck; 05-23-16 at 08:29 PM.
Old 05-23-16, 09:16 PM
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Yeah they get light. Going around the back of Phillip island race course where its long blind sweepers over a crest at near 200kmh gave the term "Wonder Steer" new meaning, literally no feel or control other than the forces of inertia already set in motion. Had crappy cut spring and KYB suspension and no air dam last time i was there though. Might be better now.
Old 05-23-16, 10:45 PM
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Originally Posted by WANKfactor
Yeah they get light. Going around the back of Phillip island race course where its long blind sweepers over a crest at near 200kmh gave the term "Wonder Steer" new meaning, literally no feel or control other than the forces of inertia already set in motion. Had crappy cut spring and KYB suspension and no air dam last time i was there though. Might be better now.
What happens out of curiosity, steering gets light and loses feel due to the loss of grip on the front tires?
Old 05-23-16, 11:48 PM
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Yeah,just felt like the steering wheel wasn't connected to anything. It's a light part of the track, but its supposed to be held flat. (scary for novice like myself). Wouldnt call the car unstable though. Was fine on the straight nearly topping out 5th gear when you arent asking the front wheels to do anything in particular.
Old 05-24-16, 01:17 AM
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Originally Posted by WANKfactor
Yeah,just felt like the steering wheel wasn't connected to anything. It's a light part of the track, but its supposed to be held flat. (scary for novice like myself). Wouldnt call the car unstable though. Was fine on the straight nearly topping out 5th gear when you arent asking the front wheels to do anything in particular.
Interesting, thanks for sharing. I suppose that's why all of the 70's/80's endurance racers ran some sort of modified front bumper.
Old 06-02-16, 09:49 PM
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here we go again

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Mine's lowered 2" and don't really feel the front wander. Have had it up to 120mph with no issues. Unless there is wind.
At ACS coming off turn 2. with wind. It's moves up the track if there it wind. But it's not bad.
Old 06-03-16, 02:04 AM
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84SE-EGI helpy-helperton

 
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It's in French, but you can figure it out:
* Red = low pressure air
* Blue = high pressure air, note windshield vent intake in high pressure area
Also note that this shows 2 profiles; one for the stock body, and one with rear lip spoiler.


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