v8eater

Just got my car out the shop and im about to start my break in stage.All these mods are new. with these mods what kind of spension will I need to keep it locked to the ground? Rebilt and street ported motor, Non sqen turbos, 1200cc rear injectors, lightend flywheel, act clutch, Blitz stock mount intercooler, light main pully, walbro fuel pump, M2 air intake, enfini y pipe, all hard piping, pettit down pipe, bonz hi flow mid pipe, racing beat duel muffler, PFC and comander ECU, Taylor spark plug wires, AVC-R boost controller, new engine wireing harness, new motor mounts, new plugs, I have 17x9 front and 17x10 rear . Whats the best bang for the buck?

Howard Coleman

iTrader: (6)

i like your mods... maybe add a dataloggit and wideband so you can do some tuning. our motors are essentially 2 cycles and as such they are more responsive than 4 cycles to tuning. as to suspension.... i recommend you run the Tein HA coil-overs. the HA model is the least expensive (around $1000) of the Tein line but are beautifully built and more importantly feature the right spring rate. other Tein models list a rate way too high for our car. the shocks are 16 position adj. run them near the middle upfront and softish in the back. set the car at 25 inches ride height at the top of the front and rear wheelwells. front and rear toe-in just a hair less than an 1/8th inch. front camber minus 1.5 rear minus 1.2. you will love the Tein HAs... another suggestion would be to replace your rear stock toe links w rod end links. since they don't carry weight ride quality will be unaffected. i would also recommend replacing the lower link in the rear w a solid bushing. ditto on ride quality. rotary extreme offers both links and they feature a rubber rod-end cover to extend bearing life. the last thing we need is rubber bushings controlling toe. it is a recipe for tire destruction and instability under power, braking and cornering.
howard coleman
p.s. i have a shock dyno, electronic spring rate checker and 22 seasons of SCCA GT3 racing so my opinions, while always open for discussion, come from experience

Howard Coleman

iTrader: (6)

ooops, tire pressure...... run 29 front 27 rear (cold)
howard coleman

ptrhahn

iTrader: (9)

I agrree w/ Howard, and the next biggest thing you can do is have the proper tires. What brand/sizes are you using?

If your car will just see street duty, the Tien HA's or even a decent set of lowering springs and upgraded shocks will probably do the trick for you.

I assume the you "not get killed" statement relates to controlling all the new horsepower you have. Tires, and properly maintained suspension and brakes will help. Be carefull till you learn the limits. Dave @ KDR told me several stories of people totalling cars on the way home from his shop after single-tubo installs and the like.

alberto_mg

if don't want to go w/ the $$ for an all out coil over, just get some konis and replace any worn bushings. the stock suspension is quite good. tires will make a huge difference as well. buy the best you can afford. then the alignment. you should be good to go.

Howard Coleman

iTrader: (6)

alberto's post got me thinking re another way to go for your suspension... if you want to spend less than the Tein coil overs i unreservedly recommend Eibach Pro Trak springs. they lower the car to within a 1/2 inch of my recommended optimum ride height (25 inches at the top of the wheel wells). and raise the spring rate 33% above stock. they drop right in and work very well with the stock shocks. i don't recall the exact price but guess it is around $250. they are a very good value and significantly improve the overall performance. don't forget to reset your camber as it will change with the height change. spring rates, according to my electronic spring checker are:
front rear
oem 263 195
Eibach pro trak 350 255
RS*R 432 378
Tein HA 566 422

howard coleman

in2twins

Howard, I am building a Super unlimited car for NASA events, basicly, It is a ~450rwhp FC widebody(~2500lbs) with lots of Aero(experiments ). I am tending towards 18x10.5fr/18x12rr wheels w/ Goodyear slicks(as opposed to 17s w/ DOT R compounds) right now. My thinking is in those sizes, I should have plenty of tire options by buying ALMS/Grand AM scrubs(shorter tires too, as in the 17s the DOTs are ~26").Thoughts?
My main question is suspension, currently, I am using koni yellows straight out of the box W/ground Control drop over perches. 550fr/275rr, 3 way adj bar rear, set full stiff, and 2 way bar front set full stiff(off the shelf pieces). I am prepared to completely revamp the suspension, but I want to get a little perspective, and I have never run slicks before. How should go about this?
One problem I have is getting the car low enough with these larger tires(I think the Goodyear slicks may solve this part, as it looks like they can be had as short as 24.5" in the proper widths), next, I cannot spend 5k plus right now. I was contemplating JICs for the independent ride height, and preload, as one option, or maybe Advanced Design. I realize I am being pretty vague, but maybe an overview from you, or ideally, a time when I could call you(and a phone number), and pick your brain for a couple of minutes. I have been doing track events for years, so I am pretty savvy, but this is a whole new game, any time, or thoughts would be greatly appreciated. Best regards, Carl Byck
heres a link to some pics https://www.rx7club.com/forum/showth...hreadid=237039

Howard Coleman

iTrader: (6)

hi carl,
quite a project... the FC is a real flexi-flyer in that there is alot of flex in the body. i would spend alot of time with the roll cage to negate this fundamental problem. if you have lots of flex you can have the most accurate suspension setup static and lose it all in a corner. as to your wheels... there is nothing wrong with lots of rubber and wheel width and you correctly are running a bit more in the rear but you absolutely must be able to run the correct offset so you have virtually no scrub radius. avoid scrub radius like the plague. not only does it wreck tire adhesion but it jacks weight in a corner. i would trade extra tire/wheel width in a minute if it cost me scrub radius. on another matter i am surprised you need a rear sway bar let alone running it full stiff. the ultimate limitation for a well set front engine rear drive racecar is rear adhesion and you run the rear as soft as possible for grip. you are in the ball park spring rate wise w the 550 and 275 but i haven't done a springrate/wheel rate study on the rear geometry of the FC. i like your 2500 lbs... my street FC that i put 185,000 miles on weighed 2700. weight is the enemy, especially front weight... battery in the rear, everything (but the engine, sorry Porsche) in the rear... also low is essential, here again, i would sacrifice tire size for another 1.5 inches of ride height in a minute. solid rear toelinks essential. then go to the track w a pyrometer and do some tuning.
keep in touch,
howard coleman

Howard Coleman

iTrader: (6)

Carl,
another point... aerodynamics.
as to aero drag: wide is bad, narrow is fast. racecar engineering is always filled with tradeoffs. running at a shortish track wide track is probably the setup but at Road America (Elkhart Lake), Road Atlanta, Brainerd narrow is fast. Top speed can be calculated for a race car using frontal area, coefficient of drag and rear wheel hp. i have used the formula for 30 years and it is dead accurate. and since acceleration is merely the change of speed due to hp in excess of the aerodrag the formula works for acceleration below top speed. required rear wheel h.p. to run a specific speed =s frontal area X drag coefficient X mph cubed divided by 146,600. notice how non-linear the need for hp to increase top speed is. the only variable in the topline of the formula is mph and it is cubed!!!!!!! my point is widebodies invariably have more frontal area and a higher coefficient of drag. a big cost at a fast track. i have to tell you that i am either barfing or laughing at these snowplow noses for the fd that people run. mazda knew what it was doing when they kept the air intake to a minimum. the R1, with it's .31 drag coefficient (due to the wing and splitter) requires 34 hp more than the non R1 (.29 drag coefficient) to run the same top speed. as you try to run a higher top speed for each car you have to cube the new mph and the 34 hp difference escalates off the charts.
you are looking in the right area if you are looking at aero.
howard coleman

Carl Byck

Thanks Howard, The sway bars were for the car in stock body form with 235-40-17 tires, on koni yellows with the spring rates I mentioned. Perhaps I could back off on both bars. Please explain how I calculate scrub radius, my offsets are -13mm front, and -8mm rear, very close to zero, but I do not know how that translates to scrub radius.
As for flex, I will be gusseting the cage to the car at every available location. In addition, I will triangulate(brace) the struts, and the firewall. In addition, I am doing some seam welding.
As for ride height, I know Tripoint has calculated the role center for the car, so I will call them, and make sure I am at pavement level(right?). Also the main reason I am going to 18" wheels is to allow the use of Goodyear slicks in a 25x10x18(284-32-18), and a 25.5x12x18(345-28-18). If I go 17" the scrub slicks are very limited, so I would be running DOTs, but at ~26" those are some tall tires, and I would have a hell of a time getting the car low enough.
As for frontal area and drag, I have alot of both. I am thinking I will start with massive downforce front, and rear, then as I learn to drive, I will reduce my aero, looking for more speed. I was reading that the old GT40 positively wanted to fly above 130mph. I think I will forego some speed right now in the interest of staying alive Hopefully the ~450-500rwhp will overcome a reasonable amount of the drag (I can feel the downforce in the nose at 55mph) my set-up has. My splitter, and wing make the R1 look like the king of low CDs. Thanks for your thoughts, and LMK on the scrub radius. Carl

Howard Coleman

iTrader: (6)

offsets should be exactly the same as oem for zero scrub. roll center is always lower in front. you want to raise roll center in front towards front center of gravity for less jacking and lower it in rear. generally you can't do much to change it without causing other problems. since you have a strut front you have no negative camber gain and should therefore run static negative camber. raise front roll stiffness until just before the car understeers as you get positive camber on the all important outside front tire with body roll on corner entry. you will need 13 X 1.25 front brake rotors. you can use your stock 4 piston calipers spaced to fit or a set of 4 piston Wilwoods will do the job.
howard coleman

$150FC

thread hijacking...complete.
however keep it up, very interesting read