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Author Topic: Sways vs. spring rate (long and a little technical)  (Read 15093 times)
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'95MSM
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« on: March 13, 2011, 10:15:52 AM »

I’ve posted about this within other threads, but thought it was time to write a more comprehensive post on why I  advise people to go with stiffer springs first, and then add stiffer anti-roll (sway) bars.  When I started this, I didn’t realize it would quickly turn into a treatise.  Oh well. 

First off, we need to accept that as the load on a tire increases, the tire’s ability to convert that load into grip diminishes slightly.  This was drummed into my skull by a Dunlop tire engineer at a race car handling seminar.  It is also explained by Keith Tanner in the Handling Theory section of his latest book.  This is an important fact to accept.  There is no such thing as “road hugging weight”.  If there was, an LMP2 car would never have been able to challenge the LMP1 cars in ALMS and Lotus Elises & Exiges would be nothing more than stylish grocery-getters instead of lap-day giant killers.

Why do we even want to change how much a car rolls in a corner?  If a car’s suspension system kept the tires at their optimum angle to the road at all times there wouldn’t be a need to restrict roll at all.  In that theoretical instance, restricting roll is more of a “feel” thing.  The more resistance, the quicker the load transfers.  To a point, it makes the car feel more precise.  Beyond that point, the car feels like it is balanced on a knife edge and you have to be very, very precise with your inputs.   On the flip side, less roll resistance makes the car feel slow to respond to the helm.  An important thing to remember is that if the suspension is already optimized as far as keeping the tires planted, cornering power is the same with high or low roll resistance.  Just the speed of transition is changed.

In reality, suspensions (especially on street cars) are rarely that closely matched to roll rate.  Restricting body roll often keeps the tires at a better angle to the road.  A great many of us first tried to drive quickly in cars with MacPherson strut suspensions, which are terrible at matching camber gain to body roll.  Putting enormous sway bars on a MacPherson strut car was an effective way to make more cornering power by keeping the tires planted.  It also conditioned a generation or three of drivers to think that flatter is better, but I digress.  Even our cherished Miatas benefit and generate more grip with reduced roll.

So how do we restrict roll?  We could re-design our suspension, but that is beyond our abilities.  What we can do easily is install stiffer springs and/or stiffer sway bars. 

Stiffer springs work fairly obviously.  The same cornering force compresses the springs less, so the body rolls less.

Sway bars are less obvious.  A sway bar connects the outside and inside suspension together via a torsion spring.  As a car rolls in a corner, the outside suspension compresses.  The lever arm of the sway bar is forced upward on that side of the car.  (In reality the arm remains the same distance from the pavement and the body is forced down, but it is easier to describe and understand if you look at the body as static and the suspension as the part that is moving around).  On the inside, the upward motion of the sway bar tries to lift the inside wheel.  Easy-peasy.

So how does that alter under or oversteer?  The amount of weight that the sway bar is trying to lift on the inside tire is transferred to the outside tire.  Because the tire isn’t as efficient at turning load into grip as load increases, you lose more grip on the inside tire than you gain at the outside.  As a result, that end of the car has less grip.

When you change load transfer at one end of the car, you are also affecting the other end, but the effect is reversed.  If you put more load on the left front corner of your car, for example, the car rocks like a teeter-totter, pivoting on a line drawn between the right front and left rear.  Load up the left front and the right rear also gets heavier while the other diagonal goes light.  This time the net change is beneficial: the heavily loaded outside tire has load subtracted while the lightly loaded inside tire gets more.  Total grip goes up.

So if a stiffer sway bar simultaneously reduces grip at one end and adds it at the other, why do it differently (i.e. with springs)?  It all comes back to the load to grip efficiency curve.  If we use stiffer sway bars for 100% of the desired roll reduction, we are going to transfer more weight when we go around corners (remember the sway bar is trying to lift the inside tires off the ground).  We gain cornering force by keeping the tire at the proper angle to the road, but we lose some of our grip because we are adding load to the relatively inefficient outside tires while taking load off the more efficient inside tires.  If we do it with balanced increases in spring rate, the load transfer doesn’t change, so we get to keep all of the increase in grip due to keeping the tires squared up.

As with most anything, there are limits to either approach.  On sway bars, once the inside tire comes off the ground, increasing the bar size will not redistribute more load, but it will continue to make the change happen more rapidly.

With spring rate, you can go so stiff as to make the suspension too rigid to follow imperfections in the road.  If you start with stock street car spring rates, the ceiling is probably in the 300 to 400% range, i.e. well beyond what most people will tolerate as far as a comfortable ride.

There are other benefits to using stiffer springs as opposed to stiffer sway bars.  Stiffer springs will reduce nose-dive under heavy braking.  Remember the camber gain curve that keeps the tires planted correctly when cornering?  When the nose drops, you are now trying to brake with tires that aren’t in correct alignment to the road.  You got the camber change, but the car is still level.  Oops.  Same is true on acceleration: stiffer springs will reduce rear squat, keeping the tires squared-up.  Sway bars can’t do that.  They are just along for the ride during acceleration and braking.

Stiff bars also start eliminating so-called “one wheel bumps”.  With a fully independent suspension, if you hit a pothole or bump with just one tire, the off-side tire is hardly affected.  Hit the same imperfection with stiff sway bars and the off-side tire gets jerked around.

So that is my theory in a nutshell:  if your car will generate more grip by restricting body roll, start by adding spring rate first.  If you get to a point where you don’t want to make the ride any stiffer, start adding stiffer sway bars.  You’ll end up with more total grip (and therefore more cornering speed) than if you try to control body roll exclusively with sway bars.  You always want some sway bar on the car.  Adjusting the sway bar is by far the easiest way to change the overall balance.  With a little ingenuity, it can even be done from the cockpit, on the fly.
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« Reply #1 on: March 14, 2011, 04:28:06 AM »

Great info, nice read.  thumup
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« Reply #2 on: March 14, 2011, 08:44:01 AM »

Great info and very well presented!  afro

When you change load transfer at one end of the car, you are also affecting the other end, but the effect is reversed.  If you put more load on the left front corner of your car, for example, the car rocks like a teeter-totter, pivoting on a line drawn between the right front and left rear.  Load up the left front and the right rear also gets heavier while the other diagonal goes light.  This time the net change is beneficial: the heavily loaded outside tire has load subtracted while the lightly loaded inside tire gets more.  Total grip goes up.
This concept is a bit counter-intuitive to me.  Can you try again for us slow folks?  laugh  Perhaps describe it in terms of a hypothetical 2,000 pound car balanced perfectly with 500 on each tire.  If we take variable like lift at speed and elevation deltas that change the force of mass (i.e. there is a lot more than 500 pounds on the driver's front at the bottom of the corkscrew) and just think about it in terms of a basic 300' skidpad, I might be less confused - I'm probably overthinking this.   thumup

On a side note, we'll stick this in the FAQ section once we get some Q&A worked in.  I trust dissenting opinions will be kept civil and in the context of discussion and clarifying.  police angel1
-h
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« Reply #3 on: March 14, 2011, 03:22:07 PM »

An old article strictly about sways:
Quote
Normally, without a sway bar when the car corners the weight of the chassis
shifts toward the outside of the turn compressing the springs on that side. The
springs on the inside generally extend a little, or do nothing. Relatively to the
chassis itself, it appears that the outside suspension compresses and the inside doesn't.

A sway bar couples the suspensions on each side to each other, *AND* relative
to the chassis. If you could put the car up on a lift and actually compress
the suspension on one side by hand, then a sway bar makes the compression of one
side also try to compress the suspension on the other. Ok.. it's still not
really obvious why that's useful so I'll say the same thing a different way.

A sway bar effectively increases the spring rate on whichever side
is compressed the MOST. If the sway bar were absolutely solid with no
twist so there's a 100% coupling between each side then
an attempt to compress one spring actually becomes an attempt to
compress both springs. It doubles the spring rate. If the bar has some
twist, then it may only increase the spring rate by say 50% on whichever side
is compressed the most.

So you're driving down the road and you go over
a bump that goes across the entire lane. The sway bar
does nothing. Both sides compress normally. You go around a
corner and the chassis starts to lean and compress the outside
suspension and now it's as though you have a bigger spring
out there, so the car remains more level. That's the good part.
Here's the bad part. You hit a bump with only one side, and it
behaves the same way, as though you have a stiffer spring,
so you feel uneven bumps more. You feel it crossing anything
diagonally as well, such as coming into or out of a parking lot
or driveway curb.

That's all the simple "How does a sway bar work?" part.
The real tricky one is.. "What does a sway bar do?"
1. We know it keeps the car more level. So what? Limiting the lean of
the body is good because it means that when you take a quick set into
a turn, that the body isn't still moving sideways after the tires at their
limits. Otherwise you turn in quickly, the tires grip, then the body finally finishes
leaning, when it stops, the tires loose grip. This is especially noticable in most
cars in the slalom where you lean one way then the other and so forth.

2. It limits camber changes. The camber is the angle that the tire leans in or out at the top
relative to the chassis of the car. The camber directly impacts the angle at which the tire
cross section meets the road and thus controls lateral grip. As the suspension compresses
the camber angle generally changes relative to the chassis. With a normal Macpherson
strut that hasn't been lowered, the camber goes from positive to more negative as the
lower A arm swings out straight, and then back to positive as it swings up. That swing
up into positive camber is BAD. At that point the chassis is already leaned over so the
tire may be starting to roll onto its sidewall. Changing the camber even more positive
just just nasty. A big sway bar will prevent the body roll in the first place, and
prevent the suspension compression on the outside which causes the positive camber
change relative to the chassis.

3. Transfer lateral grip from one end of the car to the other.
This one is a real trick to understand, but racers exploit this EVERY time they go
on the track. Their spring rates are often so high, the cars so low, and their
suspension travel so little, that the whole camber and body lean problem is already
a non-issue. The car doesn't lean much with 500 lb springs. They use their bars
to change the balance of the car. Here's the simple rules first.
A big bar on the front, increases rear lateral and motive traction.
A big bar on the rear, increases front lateral and motive traction.
The applications. If the car is understeering, decrease front bar size, or increase
rear bar size. This increases front lateral grip and decreases rear lateral grip
giving the car a more neutral to oversteer feel. Reverse the process for
too much oversteer.
I mentioned motive grip. That's the neat one. Let's say your RWD car is handling ok, but
everytime you get into a corner hard and get on the gas the rear inside tire breaks loose
and spins. You can't accelerate out of the turn. You can go around the turn quite
quickly, but you can't accelerate out, and the guy with traction hooks up and
passes you halfway down the next straight because he came out of the turn going 3-4mph faster.
The reason you're losing the traction at the inside rear, is usually because the rear bar is too big.
As the rear outside suspension compresses, it's actually causing the rear inside suspension to
compress as well (because the bar couples the sides.. remember where we started), and that
decreases the weight on the rear inside tire.
First thing. Decrease size of rear bar. That decouples the sides a bit, let's the inside tire press
down on the road more and thus not spin when you're on the gas.

Here's where it gets really tricky.
If decreasing the size of the rear bar doesn't help enough the next thing you do is
increase the size of the front bar. When the outside front compresses in a corner, it
causes the inside front to compress and may actually lift that tire completely off the
ground. The car is now sitting on 3 tires and guess where the weight that was on
the inside front goes? Outside front? Some of it. The rest goes to the inside rear
where we need more grip. The total weight of the car hasn't changed. It's just been
redistributed, and a sway bar at one end, actually transfered weight to the other
end of the car. Here it is in action on a RWD car.


See the inside front tire off the ground. That translates into more motive grip
at the rear, and thus more acceleration, and believe me, that car rockets
out of corners.

All of this trickery applies to a FWD car too, and since the front tires share all of the
motive AND most of lateral traction (because most of the weight is in front), all the things
that happen with big bars at either end are even more extreme. A big front bar stabilizes the body
lean more but also creates a lot more understeer, and may make the inside front tire spin madly under
power in a corner. A big rear bar can't give you back much lateral grip up front, but it can
give you back some motive traction. Basically lettting you
accelerate out of the turn, even when the front end is sliding pretty badly.

Here's a big rear bar in action on a FWD car.

(pictures didn't come over with the article)
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« Reply #4 on: March 14, 2011, 04:55:38 PM »

Wow that answered a few of my questions!
I had a few instances of my rear inside tire lifting in corners... not allowing me to accelerate out!
I had originally thought it might be my ride height.. so i adjusted that... all seemed fine but the now LOW! ride height made the car prone to slide everywhere...the tire stayed on the ground and if I was easy on the throttle I was able to keep it from oversteering too bad!
I like these discussions! with this in mind we could come up with a mod path for suspension!
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« Reply #5 on: March 14, 2011, 09:45:23 PM »

Hyde - Think of the car as if it was a 4 legged table with one long leg - the table will rock back and forth across the axis made by the long leg and the one diagonally across from it.  The other two legs don’t carry much of the weight.  You only lengthened one leg, but the weight carried by all four legs is affected.  When a front sway bar, for example, transfers weight to the outside tire, that tire is just like the long leg on that crippled table: the outside front tire gains load and diagonally across the chassis the inside rear also gains.  The other tires go light.  It really jumps out at you when you are corner-weighting a car.  Touch one spring perch and all the scales change.  


Brandini - The article you posted does a better job by explaining that the sway bar tries to compress the spring.  I was wrong about the bar ceasing to do much when the inside wheel comes off the ground.  It is still trying to compress that inside spring further.  

I think it suffers a bit by not discussing how tires are less efficient at turning load into grip as load increases.  That loss of efficiency is important for understanding why some changes work better than others.  I knew how to tune my suspension with sway bars, but when I finally understood what load/grip efficiency was all about, everything came into focus better.  You can talk about springs vs. sways until you are blue in the face and not get the point across, but if they accept the load/grip efficiency thing and you do the math and show how total grip can go up or down based on suspension tuning decisions, it is hard to deny.  The trick is keeping the discussion simple enough for everyone to follow, but giving them enough of the picture.


dvdreith -  With a torsen (ours is a Bosch brand, but still a torsen type), you shouldn't ever smoke just the inside rear tire and not accelerate.  There is something wrong in the picture you've painted.  

As far as dropping the car and a loss of grip, the explanation gets more technical. The way centrifugal force makes the car roll in a corner is strongly affected by the height of the center of gravity over the rollcenters.  That distance is like using a lever to move something – the greater the cg height over rc height, the more roll you get.  When you drop most any car down, center of gravity obviously drops, but the front and rear rollcenters typically drop a lot more, sometimes dramatically, because the control arms are now sloping down from the tires to the subframe connecting points.  It isn’t unusual to have the rollcenter drop 4 or 5 times as much as the cg, so now the lever that centrifugal force uses to make the car roll is longer than it was before and the car rolls more.  When you dropped the car, you also gained some static negative camber.  So more body roll into the camber curve of the suspension coupled with a starting point of more negative camber than you formerly had, and it is no surprise the car felt like a pig.  Been there, done that on my S2.  Didn’t understand it at the time, just knew I had messed it up by lowering it, so I raised it back up.  More recently, I got some help from a former SCCA Runoffs champ that happens to be a mechanical engineer.  He analyzed the suspension geometry of my S2 and suggested comprehensive changes.  The rollcenters were raised quite a lot front and rear.  The car now has more grip and corners flatter using the same springs and sway bars.  Why? The height of the cg over the rc is smaller, so centrifugal force acting on my car has a shorter lever and can't make the car roll as much.
« Last Edit: March 14, 2011, 09:51:04 PM by '95MSM » Logged

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« Reply #6 on: March 14, 2011, 10:14:28 PM »

Mark

I think what he was saying is the same problem I had on the track when I had the GC coilvers on the car.  In a hard high speed right hand turn I was lifting the right rear almost completely off the track.   This made the car twitchy and didn't allow me to get back into the power as much as I would have liked.  Yes, I was accelerating out of the turn but I just couldn't do it the way the car should have been able to do it.
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« Reply #7 on: March 14, 2011, 10:24:56 PM »

As far as dropping the car and a loss of grip, the explanation gets more technical. The way centrifugal force makes the car roll in a corner is strongly affected by the height of the center of gravity over the rollcenters.  That distance is like using a lever to move something – the greater the cg height over rc height, the more roll you get.  When you drop most any car down, center of gravity obviously drops, but the front and rear rollcenters typically drop a lot more, sometimes dramatically, because the control arms are now sloping down from the tires to the subframe connecting points.  It isn’t unusual to have the rollcenter drop 4 or 5 times as much as the cg, so now the lever that centrifugal force uses to make the car roll is longer than it was before and the car rolls more.  When you dropped the car, you also gained some static negative camber.  So more body roll into the camber curve of the suspension coupled with a starting point of more negative camber than you formerly had, and it is no surprise the car felt like a pig.  Been there, done that on my S2.  Didn’t understand it at the time, just knew I had messed it up by lowering it, so I raised it back up.  More recently, I got some help from a former SCCA Runoffs champ that happens to be a mechanical engineer.  He analyzed the suspension geometry of my S2 and suggested comprehensive changes.  The rollcenters were raised quite a lot front and rear.  The car now has more grip and corners flatter using the same springs and sway bars.  Why? The height of the cg over the rc is smaller, so centrifugal force acting on my car has a shorter lever and can't make the car roll as much.
This point goes against the common (incorrect) concept that a car lower to the ground will handle better but it makes perfect sense.  Do you have a number of where the ride height of a miata is best suited for this balance between height and roll center?  There are other things to consider like high speed handling that gets better when the car is lower and thus allows less chaotic air under the chassis.  I guess balance and compromise is the name of the game here as it is in many parts of life and the physical universe!  afro  Better engineering minimizes the need for compromise though!   hack
-h
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'95MSM
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« Reply #8 on: March 15, 2011, 03:54:15 AM »

I'm not sure there is any underbody affect on a stock Miata.  My opinion, and it is only that, but I've researched a fair amount about flat bottomed race cars & diffusers, is that underbody aero benefits start with flat bottoms run at the right rake.  Anything that isn't flat has enough turbulence that there is negligible benefit, no matter what height.  The progression goes something like this:
stock street car chassis: extra drag from all the stuff hanging down, no aero downforce impact
windage trays but not totally flat: less drag, but still neutral aero downforce
flat bottom, run at about 1/2" of rake: beginning to see useful downforce
flat bottom with rear diffuser: making noticeable downforce
tunnel cars: holy grail

Precisely where to put the rollcenter height, if you could change it, is still a mystery to me.  If I had to find the right zone on my own, I would have to build iterations and test.  Not really very practical, so I paid Steven Johnson to analyze my car.  He claims that his dominance came from having superior mechanical grip that allowed him to trim downforce and drag out of the car, so I figured he has a pretty clear idea of what is optimum for an S2.  

I don't even know if there is a magic zone for all cars, or if the "package" of power, aero, tire on the ground, etc dictates what it should be.  I just know that I have experienced too low in street cars and race cars.  They look cool, but drive like sloppy pigs.  My sense is that the rollcenters should be somewhere around axle height, and front to rear should match closely.  If they don't you get bizarre things happening mid-corner.

Does Shaikh have rollcenters plotted for the NA and NB on the FatCat site?

« Last Edit: March 15, 2011, 03:57:30 AM by '95MSM » Logged

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« Reply #9 on: March 15, 2011, 04:00:29 AM »

Better engineering minimizes the need for compromise though!

I'd phrase it a little differently: better engineering leads to a better compromise.
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« Reply #10 on: March 15, 2011, 04:39:38 AM »

True.  Regarding downforce - we aren't going to make any on a street car without a ridiculous wing and that comes at the notable cost of drag (more compromise).  I do believe there is some gain to be had with undertrays that smooth out the bottom and make the air flow better.  There has been a fair amount of amateur engineering done on this by some of the California guys (dams and canards in the mix).  'Reduction of lift' is better than 'downforce' as a description.  I haven't looked up roll center Shaikh's data but if anyone has it for a Miata, it would be him.
-h
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2005 Black Mica #290 8/27/04 w/Factory Hard Top
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1990 Red - MSM Drivetrain, Adaptronic EMS, Xida 700/400, 15x9 6uls, Full Cage, SGDP w/80mm Corksport exhaust, ~260whp @ 15psi on Forged Rods.  bow2
Build Thread: http://www.mazda-speed.com/forum2/index.php/topic,24668.0.html

2000 BMW M5 - The Falcon - Daily Driver  reddevil

2003 E350 7.3 Powerstroke Ambulance for towing '90MSM to play dates.

1991 BRG - Daughter's daily driver.
'95MSM
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Turbo clocked downward, new i/c plumbing


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« Reply #11 on: March 15, 2011, 06:12:27 AM »

The NA and NB don't have any strong impediments to cleaning up the bottom and making some downforce under the car.  Just about everything is tucked up above a line drawn between the false frame rails.  If you move the muffler, as I have but for a very different reason, there is plenty of room for a good diffuser.  Miatas like some rake in the chassis, so the downforce seen on flat bottomed race cars could probably be done on an NA or NB.

What I don't have a feel for is whether you could button up the bottom of the car and expect the transmission and rear end to live, especially on a turbo car.
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'05 running gear + '95 body
3.63 ring & pinion FM content: Blouch compressor mod, FM-Link, i/c & no-MAF intake.   BEGi: Stainless SGDP w/ metal core performance cat.   Custom stuff: Compressor clocked downward w/ new i/c pipe, big radius throttle elbow, 2.5" mid-pipe w/ Hushpower II, dual 2" axle-back w/ open Supertrapps, Toyota 4 pc cop ignition

245.2 whp on default FM-Link maps (with OEM midpipe)
mr_hyde
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« Reply #12 on: March 15, 2011, 07:25:41 AM »

I guess we need to put some sensors in    for the tranny/diff fluids as well as the tunnel ambient so we have a baseline to compare!  laugh  This thread is drifting away from sway v. spring but aero discussions are related to a degree.   angel1  I have been considering the effects of an undertray that covers from the splitter to around the cat as it pertains to pressure and flow through the engine compartment.  My fear would be that blocking the path of least resistance would increase pressure in the engine compartment thereby decreasing flow through the heat exchangers.  An extraction hood would be ideal for this but then you loose flow through the tunnel that may be needed to keep things cool.  Do you add axillary cooling to the transmission and diff?  That costs pounds and failure points.  Didn't we discuss compromises earlier in the thread?  laugh
-h
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2005 Black Mica #290 8/27/04 w/Factory Hard Top
BEGi Intake, FM Downpipe.  Nice and calm with an edge...

1990 Red - MSM Drivetrain, Adaptronic EMS, Xida 700/400, 15x9 6uls, Full Cage, SGDP w/80mm Corksport exhaust, ~260whp @ 15psi on Forged Rods.  bow2
Build Thread: http://www.mazda-speed.com/forum2/index.php/topic,24668.0.html

2000 BMW M5 - The Falcon - Daily Driver  reddevil

2003 E350 7.3 Powerstroke Ambulance for towing '90MSM to play dates.

1991 BRG - Daughter's daily driver.
VagaXt
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Posts: 1285


I drive fast when I can, but I always drive well.


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« Reply #13 on: March 15, 2011, 08:26:02 AM »

In regards to the aero that us CA guys are experimenting with, there's no hard (quantitative) numbers other than a good reduction in Miata lap times at our local tracks within the past couple of years.  Qualitatively, the aero of wings, canards, splitters, etc. are felt for high speed stability, but like as mr_hyde says, some of it come with the price of drag, especially at [power] tracks that reward low drag and overall mechanical grip, e.g. AAA Auto Speedway in Fontana, Willow Spring International Raceway and Laguna Seca.  In places that those, low-drag aero like a fastback hardtop and flat bottoms have more weight towards faster lap times.

In regards to the OP by 95MSM, I completely agree for the process of reducing roll by first springs, then anti-roll (sway) bars.  My MSM and NA's suspensions are tuned to this very concept (both have MSM stock size anti-roll bars).
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#992/4000, The Ultimate Daily Driver



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dvdreith
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« Reply #14 on: March 15, 2011, 10:00:24 AM »

I guess we need to put some sensors in    for the tranny/diff fluids as well as the tunnel ambient so we have a baseline to compare!  laugh  This thread is drifting away from sway v. spring but aero discussions are related to a degree.   angel1  I have been considering the effects of an undertray that covers from the splitter to around the cat as it pertains to pressure and flow through the engine compartment.  My fear would be that blocking the path of least resistance would increase pressure in the engine compartment thereby decreasing flow through the heat exchangers.  An extraction hood would be ideal for this but then you loose flow through the tunnel that may be needed to keep things cool.  Do you add axillary cooling to the transmission and diff?  That costs pounds and failure points.  Didn't we discuss compromises earlier in the thread?  laugh
-h

In a sense if you had a flat bottom from front to back with 1/2" clearance, and rake the air that normally escaped under the car would be increased greatly... but instead of having it exit under the car it would be exiting from the back of it.. so I would imagine it would increase flow through the heat exchangers.. just not as much as an areo hood would...


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Full Built motor: take 2!
Hydra 2.6, 550cc injectors, FM intake, liquid to air intercooler
Block:
.040" over
Acl race bearings.....maybe this time, oem thrusts will be used!
84mm Fm weisco pistons
Carrillo super A beam rods
ARP fasteners
Ati damper
Arp studs
Head:
Cometic .040" head gasket
S.S. 1mm oversized valves
Titanium springs & retainers
Port, polish, unshroud valves
Custom powdercoated valve cover

Shoes:
2nd gen 949racing 6ul's in nickel
wrapped in Nitto NT01's
that sit under BC coilovers
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