olddragger

iTrader: (3)

I recently put a s.c. on my 8 and the power gain has made a totally different car out of her. In trying to figure out what to do about the cars handling on the track(a na car is VERY easy to drive) because of turn exit concerns I was told i may want to unbolt the rear sway?
My suspension is koni's with ten H springs, rb bars with endlinks.
thoughts anyone?
oldscdragger

DarkBrew

Disconnecting the rear bar will generate a lot of under steer entering the corners and slow you down a lot. I take it you're concerned with over steer on the corner exit. I think that you just have to respect the extra power and not apply so much throttle with steering angle; Wait for the straight.
What's the power delivery like on the SC RE

olddragger

iTrader: (3)

from 2.5-3K up --linear and strong. by 4k-5k it is VERY strong. the tires break loose with throttle application only in 1st gear and sometimes (during cold weather) in 2nd gear). approx 300 to the wheels.
I have approx 1500 miles on the track with this car in the na form but this has changed everything. Will have to learn this car all over again.
I think you are right about the throttle. I just have to get the idiot that is using it to listen.
oscd

mwood

300hp, in a 2900lbs car with the Mazda's attributes, shouldn't pose any problems, particularly because of the linear nature of the power delivery, i.e. no big "hit" to unsettle things. Unbolting the rear bar would just make you go off the track nose first, if you got carried away, I would think

DarkBrew

You're making me want a SC!! Argh!
I'm going to be hitting the track some this summer to try out my new suspension.

The throttle analogy I heard is to imagine a string wrapped around the steering column and tied to your foot. As you unwind the steering you get to apply more throttle...

SouthFL

Use the adjustability of the Koni dampers to dial in the proper handling trait you're looking for. To reduce oversteer, stiffen the fronts and/or loosen the rear. Adjustability of sway bar also comes into play (again, stiffening the front and softening the rear will help reduce oversteer). But, I definately would not run without a bar back there. This will drastically change things.

Note; this will affect your turn in understeer as well, and you may find yourself plowing much more than you'd like given the above changes, so it's going to be a dialing in of suspension in small increments until you find what you like, plus, throttle modulation, throttle modulation, throttle modulation. I think that throttle modulation in relation to steering wheel angle will be more important than suspension tuning in this case.

SouthFL

This is gold. It was an epiphany when I first heard of the analogy.

staticlag

soften the rear koni's and better tires?

mac11

iTrader: (1)

Trial and error.

Lots of ways to skin this cat.

As mentioned above, softening the rear, stiffening the front through the spring rates, sway bar rates, damper rates could work.

Also try different alignment settings. Some more static camber in the rear or conversly less in the front may be the way that makes the driver happy. More static caster will add more dynamic camber through the turn so a bit less caster might help a bit as well. This stuff will be best sorted with some tools.


Get a pyrometer, camber/caster gauge, cloth tape, toe plates a notebook and hit the track. Log everything.

ULLLOSE

iTrader: (1)

Why not try the stock rear bar???

mwood

What I'm failing to understand is how the sc "changed" any aspect of the car's handling...and why a car that was (evidently) comfortable and dialed in needs to be set up to push, all of a sudden...makes no sense. Maybe the additional weight of the sc, up front and high, has changed the balance? That's the only way that I can really see the "handling" being any different, post sc install, but I would think that weight would add to understeer, if anything

It does make sense that adding, basically, 35-40% more power might require a little time to become comfortable with...but, I'd personally prefer to learn the new powerband with a car set up to my driving style, not one with built in push as a "band aid".

ULLLOSE

iTrader: (1)

I could see how the car now having TQ could change things. Even most of the fast CSP Miata's have gone to no rear bar now.

mwood

Having some torque would allow more ability to steer with the throttle, so to speak, but how would it change the turn in, mid turn and (with throttle modulation) off turn...i.e. how would it change the actuall balance between front and rear grip? I can't imagine it...if the suspension is working, within it's geometry and design parameters' capabilities, it is working...throwing more power at it isn't going to make it "work" differently. I guess if you had a ton of torque, with a big hit, you might want to change some things (like rear toe) to make it easier to keep the back end under you, when the tires were spinning and grip was being lost...

I'm not sure what CSP Miotters have to do with it, though...

ULLLOSE

iTrader: (1)

The SC itself will do nothing to the cars handling, what the driver does with that extra power is the problem. You could get over or under-steer with more TQ. In a high speed turn with extra TQ if the car is hooked up it will under-steer because you could overpower the front tires. In a low speed turn a little throttle on over-steer could poke its head in. A softer a rear bar will keep the inside rear tire down on entry, and help to put power down on exit.

mwood

^you were posting while I was editing. I think we are saying kind of the same thing...the other side of the equation is if you had less power, you might be willing to live with more oversteer, to get the car to rotate easier on throttle. So, I guess having a little more push with more power (which I'd probably do with the rear toe, initially, because of the biggest area of concern being off corner/on throttle) does make some kind of sense.

Still, if the OP's car was good before the sc, I wouldn't change a thing...just go out and drive it. It's not like it will be a bear to catch a 2900lbs car with 300hp and I'd rather have it near optimal than purposely compromised.

ULLLOSE

iTrader: (1)

On the big track with no cage in the car a safe setup, push, is always better than loose. imho

mwood

Can't disagree with that idea...

ZoomZoomH

iTrader: (1)

put on wider tires?

SouthFL

Agreeed. The car should be dialed in. Something as simple as tire pressure and/or alignment could be the fix the OP's looking for. But, further adjustments may be necessary (as mentioned above).

Here's your typical list of adjustments:


TO REDUCE UNDERSTEER or INCREASE OVERSTEER:

Front tires:
- Increase tire pressure in 2.5psi increments
- Increase Section Width
- Lower the Aspect Ratio
- Reduce front tread depth

Rear Tires:
- Reduce tire pressure in 2.5psi increments
- Reduce section width
- Install higher aspect ratio tires
- Increase rear tread depth

Front Wheels:
- Install wider wheels
- Install lighter wheels

Rear Wheels:
- Install narrower wheels
- Install heavier wheels

Front Alignment settings:
- Dial in more negative camber
- Dial in More toe-out
- Dial in more positive caster

Rear Alignment settings:
- Dial in more positive camber
- Dial in more toe-out (Same as front)

Anti-Sway bars:
- Soften the Front
- Stiffen the Rear

Spring rates:
- Soften the Front
- Stiffen the Rear

Shock absorbers:
- Soften the Front
- Stiffen the Rear

Suspension Bushings:
- Soften the Front
- Stiffen the Rear

Brake Proportioning
- Reduce Front brake pressure
- Increase rear pressure

Weight Distribution
- Reduce front weight
- Increase rear weight

Aerodynamics:
- Increase Front Downforce
- Reduce rear downforce

---------------------------------------------------------------------------------

TO REDUCE OVERSTEER or INCREASE UNDERSTEER:

Front tires:
- Decrease tire pressure in 2.5psi increments
- Decrease Section Width
- Install higher Aspect Ratio tires
- Increase front tread depth

Rear Tires:
- Increase tire pressure in 2.5psi increments
- Increase section width
- Reduce aspect ratio
- Decrease rear tread depth

Front Wheels:
- Install narrower wheels
- Install heavier wheels

Rear Wheels:
- Install wider wheels
- Install lighter wheels

Front Alignment settings:
- Dial in less negative camber
- Dial in less toe-out (to toe-in if needed)
- Dial in less positive caster

Rear Alignment settings:
- Dial in less positive camber
- Dial in less toe-out (Same as front)

Anti-Sway bars:
- Stiffen the Front
- Soften the Rear

Spring rates:
- Stiffen the Front
- Soften the Rear

Shock absorbers:
- Stiffen the Front
- Soften the Rear

Suspension Bushings:
- Stiffen the Front
- Soften the Rear

Brake Proportioning
- Increase Front brake pressure
- Reduce rear brake pressure

Weight Distribution
- Increase front weight
- Decrease rear weight

Aerodynamics:
- Reduce Front Downforce
- Increase rear downforce

NaarLeven

edit

NaarLeven

TO REDUCE OVERSTEER or INCREASE UNDERSTEER:

Front tires:
- Decrease tire pressure in 2.5psi increments

correct me if im wrong but wouldnt a decrease in front tire pressure increase oversteer because lower tire pressure = more grip so on turn more grip on the front and less on the back? sort of why dragsters have tiny high pressure front tires and huge low pressure tires in the rear?

ThecdnRX8

As you and others have said the first thing you need to do is relearn your car and adapt your driving style. If grip is what is lacking wouldn't wider tires and rims solve the issue. From what you have posted in the past 235 or 225 (even if they run wide) imo are to narrow at this point. IMHO I think 255 should be the starting point for a car with 300 whp. If your car was well balanced pre SC. The best way to get more traction is with tires.

Then you can sell me your 225's and wheels

BTW I can't wait to hear how she does on the track!

mwood

Theoretically, for every tire/wheel combination, there is a pressure which will result in optimal lateral grip. So, in theory, either increasing or decreasing pressure from that point will lessen grip. Most tires seem to respond more to dropping pressure, but in some cases, raising pressures will prove to be a more effective way to sacrifice grip. In either case, changing pressure is usually the easiest way to change front/rear balance, but not the best...

SouthFL

For the most part, an increase in front psi reduces understeer. We're talking lateral grip and sidewall structure.

Autox guys tinker/oppose with this theory by overinflating tires to get the car to rotate easily (i.e. ballooning the rear tires on a FWD car). Overinflation is ok for short runs, but do this on a roadcourse and your tire won't last long as temps build.

As for your analogy, you're referencing longitudinal grip (helped by the flex/twist of drag tires with soft sidewalls and low psi which you've mentioned) which propels a car forward.

TeamRX8

iTrader: (25)

treat the problem, not the symptom

the rear swaybar isn't the issue

fwiw, you can get the opposite effect from many of those generalities posted above, very few vehicles will be optimized using that approach