Howard Coleman

iTrader: (6)

a friend, Dick Lambert, recently acquired a nicely built 1995 fd 3 rotor and i am in the initial stages of taking a good look at it from an engineering perspective.

my background is 22 seasons of SCCA Nat roadracing, the last 6 in a tube frame mazda rx3. i am a suspension guy, i own a shock dyno and a high tech spring rater as well as a bunch of cool laser based alignment tools... (after having plotted the entire fd geometry i can tell you why the fd drives like a racecar... it is because it has a true racecar suspension complete w negative camber gain etc.)

i was concerned, firstly, w how much front weight the 20b added... so onto my scales it went. i was positively impressed.

dick's '95 3 rotor weighed 2694 with no gasoline on board. dick has another 95 fd w an rx6 single turbo w very light wheels, exhaust etc. i weighed it at the same time and it weighed in at 2517 with no gasoline.

the 3 rotor frontweight was 1395 versus the 2 rotor at 1285. both cars unfortunately still retain the xxxxx power steering and a/c so you could remove at least another 60 pounds of nose weight. (the 3 rotor did benefit from the battery relocated to the right place whereas the 2 rotor had a smaller battery in the stock location.)

considering the major improvement in torque and hp w the 3 rotor i was very impressed w the modest increase in front weight. if it was my car the power steering and a/c would be gone leaving just 1335 (51%) on the front tires.

i drove the car briefly and being in Door County (just north of Green Bay Wis) and dealing w 35 degrees ambient w a poorly tuned temperature-corrected Haltech E11 and not having time to do some tuning... boost cut etc... i was initially impressed w my reading of the handling and front end geometry. the car has either a Pettit subframe or something similar w a relocated steering rack and lengthened steering arms. in the next few weeks i am going to do a bump steer evaluation to see what the real story is re the steering relocation and will report back.

one item that blew me away was the SOUND of the motor while driving. it immediately made me think of a Ferrari 12 cylinder which i consider to be one of the greatest sounds made by man. (along w an unmuffled rotary of course). what a sound.

Dick's car has a T66 on it and we will be shipping it off to my favorite turbo guy, Kevin Draper, at Majestic Turbo to be checked over. everything on the car is new but Kevin is the Dr. either we take his advice and go to something bigger as the T66 makes 68 lbs/min (around 512 rwhp) or he will machine his customary 4 ounces off the turbine wheel and replace the compressor nut w a bullet which will increase the compressor flow by 14-18%.

we will do some tuning and eventually get steve kan to do some real tuning after the snow melts.

i look forward to sharing whatever we learn.

howard coleman

RETed

I always describe the sound as a cross between a Ferrari V12 and a Buick Grand National.


-Ted

t-von

iTrader: (8)

Was this 20b the black Fd that was sold on ebay by Tito Ramos "Alamorotary"?

Howard Coleman

iTrader: (6)

the car was built in florida by someone, i am told, who worked for mazda. it, no doubt, shares various components, either from pettit direct on non-direct. the subframe and steering arms look pettit. the engine is a fresh pettit built/street port.

felix_is_alive

keep us posted ,nice write-up

rx7tt95

Let me guess...it's yellow. I have pictures of that car at Sebring International Raceway. It was built by someone (can't remember his name off hand but I believe it was Tim) and he was very informed/knoweldgeable and a nice guy to boot. Someone else bought it, tracked it at least once, and didn't seem to have a friggin clue about the car. He said he was going to sell it.

The car USED to be red, right? Turbine manifold is made from welder's pipe. Should last forever. I'll try and find a pic from Sebring and post it on this thread.

rx7tt95

Here are a few links to images at www.performance-drivers-club.com

FYI, I took these images. I'll find a few more from my hard drive.

http://www.performance-drivers-club....223%20copy.jpg

http://www.performance-drivers-club....238%20copy.jpg

rx7tt95

Found some images, I'll try and have them up shortly.

I remember seeing this car go by, just above idle, thinking, man that car sounds good...so I check out the exhaust canister. It's a Racing Beat. I think to myself, I'll have to get one of those, sounds better than my GReddy PE! Later I find out it's a three rotor, LOL. I can still hear it going down the front straight. Sounded absolutely wicked.

RotorMotor

iTrader: (5)

beautiful writeup, great info! im dying to hear more, and to have you take a look at my car when its done (if it ever gets done ) im going to be using the pettit subframe/spindles so im very interested in what turns up regarding the bumpsteer.... they claim to have fixed it entirely. -heath

rx7tt95

Here's a pic without watermarks. Send me your e-mail and I'll send you a high res image free of charge

Other items I remember are that yes, it's a Pettit subframe. Stock engine internally, never been rebuilt. GM coils (LT1 or LS1). BBS LM wheels. Homemade front mount. Overall, nice work done by the original owner. Not sure he worked for Mazda. I probably shouldnt' mention what it's selling price was from the original builder of the car, but it was UNDER $30K by a wide margin. Why he sold it, I'll never know.

rx7tt95

Just noticed that you said it was a Pettit rebuild streetport...are you positive on this? When I photographed the car in October, it had the original, unopened engine.

Howard Coleman

iTrader: (6)

Michel,
thanks for your interesting and accurate comments re Dick's 3 rotor. you sure take nice pictures. it is neat to see the car out on the track, where it should be. you were correct as to the motor you saw in the car. it was internally stock w the T66. we stipulated that the car come with a fresh Pettit streetport and that is what currently resides in the engine bay. BTW, i congratulate you on many of your mods. i enthusiastically recommend the Tein HA's as the best coil-over setup for the fd, especially when considering the price. the other more expensive Tein options have too much spring rate. as mentioned previously, i have a shock dyno and spring rator and run the Tein setup on my car. i also run the AP brakes which are awesome.
dick lambert's email address is: dlambert@DCwis.com and i am sure he would love to receive any of your pictures and thanks again for your observations.
howard coleman

RotorMotor

iTrader: (5)

have you tested many other coilovers for the fd, and or other spring/shock combos? also a 3rotor FD should have slightly different suspension needs than a normal FD wouldnt it?

do you still recomend the tein HA's as the BEST coilover for the FD period?

Howard Coleman

iTrader: (6)

spring rates as per my very accurate electronic spring checker are as follows:

Oem 263 fr 195 r
Eibach protrack 350 fr 255 r
Rs*r 432 fr 378 r
Tein ha 566 fr 422 r
higher priced iterations of Tein coil-overs have published rates considerably higher than the HAs. that's just too much spring IMO. because the rx7 has pretty good roll center to center of gravity and good weight distribution and negative camber gain due to a well designed unequal length A-arm suspension body roll isn't too much nor is it bad for camber. you don't need to run 800 lb springs like you do for a BMW w it's strut front suspension. stiffer springs do not effect lateral weight transfer... only the speed with which it transfers. as you go up in spring rate you make the car harder, and eventually impossible , to drive fast. so i like the HA rate and they are as stiff as i would go. i also like the build quality of the piece. and the 16 shock adj settings work well. i run 5 clicks from full soft in front and full soft in the rear. tire press cold 30 front 28 rear maximum. yes i have tested other coil overs. generally they cost 2x the Tein Ha. as long as you have the right spring rate and can adjust the dampening around the center of the rate you have it all IMO. as to different coil-overs for a 3 rotor... since the frront weight is close to the 2 rotor i don''t see a need. i do see a need for bigger rubber and it would be supremely important to end up w the exact same offset. any scrub due to say,a 1/4 offset, is an absolute killer.
howard coleman

Wheel/spring
Fr 1 inch at wheel = .605 at shock
R = .68

rx7tt95

I agree, for the money, it's a great shock. I'd like to see the Flex units put through a shock dyno as I believe they're slightly uprated versions of the HA's. The valving on the HA's is "ok" but they tend to get a bit bouncy on bumpy tracks at higher stiffness settings. 5 up from full soft is nice, even on the street. I tend to run 12/10. Need to move to a smaller, less agressive rear swaybar with these shocks too.

Glad the car is in the hands of a real enthusiasts.

RotorMotor

iTrader: (5)

so howard, your saying compensate for the extra 100lbs up front w/ raining the height or the stiffness? im definatly NOT well educated when it comes to suspension (i need to get a nice beginers guide to suspension set-up book). oh, also i had another question for you.. its about staggered tires.

most 20b's need at least 285's in the rear to put down all that power, thats about the very largest tire you can squeeze in the rear wells without rolling the fenders. the problem is that it would not be feesable (due to destroying your fender when turning) to put 285's in the front... it may be possible but im not sure how well that would work out. largest ive heard people using are 255's...(someone jump in if they know otherwise).

anyway, huge tires in the rear and not so huge tires in the front seem like they'd be a disadvantage with a car thats "supposed" to be balanced 50/50. now the 20b adds 100lbs up front and then with the staggered tires how would handling charachteristics be affected? sorry for all the suspension/handling q's ... i guess im kind of a suspension newb. thanks a ton! -heath

t-von

iTrader: (8)

RotorMotor, search the suspension section for Maxcooper. He has 18x10 wheels w/285 series tires on the front of his Fd.

RotorMotor

iTrader: (5)

really? with no problem turning??? i wonder how low his car is? i will definatly look it up! thanks for the info t-von.

so are there any disadvantages to running such a large tire up front?

Howard Coleman

iTrader: (6)

here's how i see the fd 2&3 rotor suspension:

the geometry in the fd is pure racecar.

first take a step back and realize that what we are dealing with is a front engine rear drive car. as such, the ultimate performance limiter on a road course is making the rear end stick. (primarily because the rear tires have greater loads on them as they power the car as well as support more than half the vehicle weight while accelerating from the apex of the corner.) and that is where most road course races are won... by the guy who can put his foot down first in the corner.hook up the rear, win the race. and softer is stickier. lower rear air pressure... front should be 30 and rear around 27 measured cold. shocks should be softer in the rear. i run 6 clicks from full soft in the front and full soft in the rear w my RS*R coil-overs which are rebadged Tein HAs. lower spring rate in the rear and a much smaller rear swaybar in back.

suspension settings: less than an 1/8th toe in front and rear, and about 1.2 degrees negative camber front and rear. i do run more at the track and find my measurement w a pyrometer.

ride height 25 inches measured at the top of the wheelwells.

there is a common misperception that stiff is fast. watch the nascar cars weaveback and forth warming their tires on a restart and you will see that the cars are softly sprung and very compliant. soft is fast as long as you can control the car. if you stiffen the springs on a racecar you do NOT change the amount of lateral weight transfer. it just transfers faster. when you are driving on the absolute edge of control you need some time to feel the weight transfer so you can feel control. also, over sprung, overshocked cars tires chatter and bounce across the track losing grip.

as to tire size: the 3 rotor needs all the rear tires it can get. on a high powered front engine rear drive car, IMO, it is just fine to run larger tires in the rear (look at the transam cars) as they perform extra duty. what is crucially important as to tires is that you maintain the exact (that means exact) offset as the stock oem wheel in front. if that means settling for less tire size in front so be it. i run 18X8.5 245 in front and 18X10 285 in rear. to do this you'll need to roll your fenderlips assuming you are running 25 inch ride height. you want to run low as the only two things that effect lateral weight transfer (which you don't want) are center of gravity and track width. so low is very important.

one final item re the 3 rotor relates to the relocated steering rack. bump steer is just about as important as maintaining the front lateral wheel offset. i will be doing an evaluation of Dick's bumpsteer and will report on it.

howard coleman

rx7tt95

Info on the 285's, the rims Max uses if I remember are CCW's. You WILL need to roll the front fender lip for 285's AND run a coil-over 2.5"OD spring or less. But it does work. I've seen up to 10.5" in the back with rolled fenders. FYI, I run 9.5's all the way around w/265's.

The problem with running a staggered setup is that you are then forced to dial out the inherent understeer created by a staggered setup. Mid-engine cars get away with this due to polar differences and most of the weight being in the rear (lighter front, less traction needed). But the whole 3 rotor, massive torque/hp thing sort of throws a wrench into the mix. In reality, you do need the biggest tires available and one should go larger than 285 which is about adequate for a high hp 2 rotor. Somewhere around 315 or 335 with an increase in tire OD would be beneficial. So you might as well get a widebody kit while you're at it. That will allow larger tires up front as well. It's a vicious cycle :-)

rx7tt95

Info on the 285's, the rims Max uses if I remember are CCW's. You WILL need to roll the front fender lip for 285's AND run a coil-over 2.5"OD spring or less. But it does work. I've seen up to 10.5" in the back with rolled fenders. FYI, I run 9.5's all the way around w/265's. My front fenders are not rolled, my rears are although they don't have to be as I have plenty of clearance as is. My offset is 45 at all four corners, five less than stock. Most of the Japanese road race cars such as the RE Amemiya car used in the Tsubuka challenge run 255's all the way around.

The problem with running a staggered setup is that you are then forced to dial out the inherent understeer created by a staggered setup. Mid-engine cars get away with this due to polar differences and most of the weight being in the rear (lighter front, less traction needed). But the whole 3 rotor, massive torque/hp thing sort of throws a wrench into the mix. In reality, you do need the biggest tires available and one should go larger than 285 which is about adequate for a high hp 2 rotor. Somewhere around 315 or 335 with an increase in tire OD would be beneficial. So you might as well get a widebody kit while you're at it. That will allow larger tires up front as well. It's a vicious cycle :-)

RETed

I think this should be moved to the Suspension section...

I saw quite a few curious comments made in this thread...

The Tein FLEX system is a "comfort" system according to Tein themselves.  I would be very surprised if the damping rates are higher than HA/HE.

I'm a bit perplexed about the comment on higher damping caused a more bouncy suspension.  This doesn't seem to be consistent with what I know (maybe that's wrong?), but if the damping is jacked higher, this should minimize shock/spring travel which should cause the suspension to run as hard as a rock.  Unless something is weird going on with tire deflection or a failing component?



-Ted

RotorMotor

iTrader: (5)

well if the suspension is rock solid and you hit a bump you loose contact with the road... (i was/am having problems with this in my daily driver miata w/ really stiff springs, koni yellows, and short sidewalls ) id hit a bump and the car would literally bounce off of the pavement!... its always about finding a balance, just that im not too good at finding it -heath

Howard Coleman

iTrader: (6)

i apologise for partially hijacking my own thread but there are legitimate suspension considerations re analizing a 3 rotor.

as to Tein coil-overs:
published spring rates:
HA 559 f 448 r
RA 895 f 895 r
RE 895 f 895 r
Flex 559 f 448 r
someone must be on drugs re those 895 lb springs. if anything the HAs are a bit high. the Eibach ProTrack springs, for example, at a 33% increase to stock (350 f and 255 r) work wonderfully w the stock shocks and IMO are a best buy valuewise for the fd. they also set the ride height close to ideal.

i don't have a problem w running the same size tire on the front of a road course fd as long as you keep the exact lateral centerline. if you alter the centerline to fit the tire when you turn the steering wheel the tire will not roll into the new direction. it will scrape across the pavement. successful engineering often envolves picking the correct tradeoffs.
understeer on corner entry is not the problem w the fd. it has the proper amount of negative camber gain, combined w a 50-50 (properly engineered w/o power steering and lots of other front removables) front/rear weight distribution. my fd has 52% rear weight. the key is getting on the gas early in the corner and that is where you need lots of rear tire.. at that point the front is unweighted, becomes a non-issue, and the whole deal is in the rear. bushings are an issue in the rear. there are 3 bushings on each side of the rear that should be traded for a solid material... rod end or nylon. they are the 2 bushings on the toe link which in the oem configuration are rubber. these steer the toe of the rear. would you rubber bush the front steering links? of course not. the other bushing is the front of the longitudinal link which when worn allows longitudinal wheel movement. since neither the toe link nor the longitudinal link carry vertical vehicle weight ride harshness will not be effected.
as to "wide body" kits i don't have a problem w what pettit runs to cover their larger rear wheels but frontal area expansion and drag coefficient reducing plastic in the front will slow the car. mazda spent lots of money to reduce frontal area to 19.26 sq ft and get a .29 drag coefficient. aerodrag greatly effects both top speed and acceleration.

howard coleman

RETed

That makes a lot of sense.
I took the word "bouncy" as being a chassis with overly stiff springs with not enough damping.


-Ted