DriveFast7

iTrader: (1)

What type of suspension changes should be made on different surfaces ,type of course, and weather Damon? Looking for input. I auto-x my REPU for kicks

DamonB

Changes I will make at the course are shocks (Koni yellows), tire pressures and front swaybar adjustments. Shocks and tire pressures change most often for me and I've driven this car long enough in enough different places that I frequently change both at the same time. Locally we run on several different surfaces so that's probably why I change the car for different events. Lots of my thinking is in the Geez! thread as many of those posts are merely commentary from the event.

In general the more grip the surface has the stiffer everything can be. Stiffer shocks, higher tire pressure, more bar etc. As grip declines you soften the car up and let the chassis move around more. Did it just start raining? First thing I'll do is drop tire pressure and soften all the shocks up. I'll also get under the front end and soften the front sway bar too. How much on all that? That you have to develop with your own car. If it goes from dry to all out rain I'll drop 5psi of tire pressure without blinking.

Grip changes as outside temp changes. Asphalt tend to get greasy as it gets hot in the sun. If I run in the morning and then in the hot afternoon I'll typically use lower pressure in the afternoon since grip is less. If it was cool in the morning and now warm in the afternoon sun I'll do just the opposite.

I find that as the course gets tighter and smaller I like the car stiffer to keep the transitions quick and allow me to rotate the car easier. As the course gets larger and faster I'll tune the car merely for ultimate tire grip at steady state. Sometimes you have to compromise.

Grip determines how fast the car can transition. The lower the grip the "slower" you need to drive the car with your inputs. Cars do nothing instantly and the lower the grip the longer it takes them to obey your inputs. Let the car finish doing what you just told it before you ask it do something else.

KNONFS

iTrader: (14)

DamonB,

you are the man, I just rated this thread; lots of info that makes sense (after doing a couple of auto X )

DaveTurnerMotorsports

Decided to go ahead and use the 400# front and 300# when its try and 300#/175# this weekend for the rainy and damp conditions expected. With my custom housings its only a few bolts to swap out springs, could be worse. Nationals this year is going to be a brand-new glassy smooth surface that is grippy, so the eventual tuning and setup will be geared towards that.

Motor gets broken in on the dyno Friday, wish me luck...I'll post sheets. Stock exhaust will be used, as we ran out of time for the custom single-exit system until next week.

RETed

8<

You're right.
I'm not saying you're wrong, but...

The term "weight transfer" is used loosely here.
If we're going to go into a technical debate on what the esoteric definition of "weight transfer" is...you win.

Drag racers call "weight transfer" when launching from a start, how well the "weight transfers from the front to the back aiding traction to the rear wheels."
Does springs have anything to do with this? Yes.
Does shocks have anything to do with this? Yes.
Does sway bars have anything to do with this? Yes.
Please, don't argue with me on this point - you can argue with them about this at the drag strip.

"Weight transfer", with your given definition, is the dynamic allocation of mass given Cg, distribution of mass, and "lever moment".
Yes, technically, springs / shocks / sway bars don't have anything to do with this.

My point is about the dynamics of the weight transfer itself.
How fast does it happen given your suspension and chassis set-up.
You can't plug all these variables in and spit out some discrete number.
Stiffer springs, "stiffer" dampers, etc. all affects this dynamic weight transfer.
If all we are worried about is weight transfer under your given definition, we all would just run the stickiest tires we can afford and fit under the cars and call it a day...so why do we mess with bushings / springs / dampers / etc.?
You call is "response".
"Response" is still dependent on "weight transfer", and I define it as the "rate" of the "weight transfer"?
Or is that a bad thing to say?

There are general guidelines when doing modifications to get the car to "go fast".
At a certain point, I like to try and tailor the vehicle to how the driver likes it to "feel", so I throw all the esoteric formulas out the window...
To me, if the driver is comfortable with how the car is handling, that's a good thing.
It might not be the fastest "setting", but getting the driver comfortable with the vehicle is pretty important to me.
No, I'm not trying to tune top-tier, professional drivers - this is basically club-level racing.
I think I've worked with the FC3S chassis enough to make baseline recommendations.
If we're talking about top-tier racing, you should be paying a professional to be doing all the tweaking - not asking us for advice.

This brings up an anecdote I remember a long time ago from a fellow FC owner...
This guy was helping to set up a Formula Mazda chassis that was recently bought used, but it was a brand new type of racing for this team.
With the car set-up comfortably for the driver, the car was decently fast.
Tweaking the suspension settings knocked off precious seconds per lap - important for any spec racing! - but the driver complained the car was downright scary to drive.
Difference between "comfortable" and 9/10th's or 10/10th's...

I dunno why I'm telling you this, cause you already know all of this...


-Ted

DamonB

Then what is all of the rest of the post above that runs around in circles?

This statement is not true. #1 Nobody would ever want more weight transfer on any road course or autox as more is always bad. #2 The softer spring rates have nothing to do with weight transfer anyway!

If you want to adjust the rate at which weight transfers you'd monkey with the shocks, not the springs.

Richter12x2

iTrader: (1)

No no, that can't be right. I heard it from a reputable source that shocks and springs don't have anything to do with weight transfer or its effects.

DamonB

I never said shocks have nothing to do with weight transfer or its effects, I said springs have nothing to do with weight transfer or its effects.

Shocks do not effect the amount of weight transfer, they merely adjust the period of time over which the transfer occurs. This changes the response of the car. However, the amount of weight transfer is exactly the same regardless of shock setting just as it's the same regardless of spring rate.

RETed

I guess you never read the rest of the post...


Bullshit.
Springs -> compression
Dampers -> rebound
Think about it.
I'll just leave it at that.


-Ted

Richter12x2

iTrader: (1)

Although to some degree all shocks have bound and rebound properties, so I'm not sure how that comes into play but that's probably what Damon's talking about. Generally, I've always understood it like Ted described it - Springs are for compression, and shocks/struts dampen the rebound effects.

DamonB

If all dampers did was control rebound of the spring nobody would ever bother building multi-way adjustable dampers...

Information about what springs and dampers do and exactly how they function and effect the chassis is readily available. There's a lot of info in the Suspension and Handling Links sticky at the top of the suspension forum.

Richter12x2

iTrader: (1)

All I know is between Damon's attached image and Ted's avatar, I'm losing my capacity for intelligent discussion

Cwaters

Wow. I have a question but I think I'll just start my own thread....

DaveTurnerMotorsports

Okay, here is the final setup that we'll be testing on Sunday--

Bilstein P30-0032 struts in AWR housings, Cusco camber plates. Energy Suspension urethane bushings throughout except for the Mazdaspeed delrin toe-steering-eliminators. Bilstein B46-0179 rear shocks from a Porsche 914-6. Spring rates at 400# front and 250# rear, fully height adjustable. "TuningPros", an eBay seller, failed to deliver a pair of strut tower bars within two friggin weeks (they are about 100 miles away from me), so the chassis is riding naked.

Also upgraded to Hawk HP+ all the way around and ss lines with Motul RBF600 fluid, fresh set of just-scrubbed Hankook RS-2 225/45-16 on the stock GTUs wheels.

I will weigh and corner-balance if I can on Saturday to see what we ended up with the cat change and A/C system delete, I'm shooting for 2645lbs (2721 was the baseline, all stock and full) with a full tank of fuel, as we didn't get a chance to re-do the exhaust or anything else while the engine was being finished up.

HUGE thanks to PureSports in Ramona, CA (formerly SPD Racing) for doing the engine rebuild and most of the suspension and brake work in a pinch, those guys are pros and truly appreciate us "race guys" (no neon lights and big stereos there). Even if the motor is not done in time, those guys deserve a lot of thanks for the work they've put in over the last 8 weeks.

RETed

Watch out with the HP+ - when they are cold, they don't stop worth a dime.
I would've stuck with the HPS, since they work alright dead cold.
The HP+ takes some heat to get them to working temp - these are really high-speed track pads, and some autocross courses need the brakes right out of the gate.

Good luck!


-Ted

DamonB

I ran two sets of HP+ in my FD on the street and autox. Never had trouble with them at all when cold and didn't notice any difference between cold and warmed up. I had excellent cold stopping power when cold, even on race rubber.

finky

iTrader: (2)

Hp+ on my FD. In MI it is always cold and they work great but they dust like crazy.

DaveTurnerMotorsports

Heh, we used to run Hawk Blues all the time on my buddy's street/track E36 BMW and Sentra SE-R. Only takes a stop to get them workable on the street.

Leaving now to go pick up the car, wish me luck!

jacobcartmill

iTrader: (6)

i have HP+'s and they work great. but yeah, they dust like the dickens.

Black91n/a

I've got HP+'s that I use for track days and they stop just fine from cold, but they are harder on the rotors than full street pads and they dust like crazy.

TwoFun

any feed back on the #400/300 spring combo worked for you?

DaveTurnerMotorsports

We didn't get the engine back together and running until late Saturday night, and even then it was running not-so-fantastically. We decided to run the stock old 180K mile suspension but with new bushings.

I ended up in 2nd place of 6 drivers (including 2 '99 Miata Sports that were misclassed, specifically disallowed in STS2 and has a clutch-type lsd), not a great start to the season, but not terrible for an engine with a part-throttle miss and no 6-port actuation, and stock suspension.

Next event is the 28th practice and 29th championship, I will be running the 400/250 setup Lord willing.

Motor may have a small coolant leak externally as well, and we need to get it back on the dyno at some point and see if we can do some ECU tuning. This is getting expensive.....welcome back to racing!! :-)

motoman93117

hey you in socal heard of ridgecrest? well i live there and just got an fc and am interested in some rally stuff i wanna know what you guys are doing for setups and any "open tracks" that are just out there if there is any i havent really seen any around here except for the one near the fairgrounds here...ive seen alot of wrx's and evos occasionally someone will bring a truck or their POS civic out but i want to try my rx out there since they closed the quarter mile i dont wanna get the car taken away for street racing so whats your input on suspension and practice areas

motoman93117

also what would some good tires to run for a little gravely type surface/desert sand and how can i raise my car using anything it already has on it like i know on a truck you can use torsion bars to help but how about this 2nd gen rx?

DaveTurnerMotorsports

Good all-season or snow-type tires would be okay on a gravely surface/sand, just keep the car at stock height and with good struts it should be okay to do rallycross-type events. You don't really need to "jack up" the car, many many cars run with stock/production type suspensions or just use coilovers to have the adjustability to run higher or lower as the course or track dictates.