Kenku

I thought I was. I don't claim to have a *very* in-depth understanding of handling dynamics, but I have studied them a bit. Now to figure out how much rubber I can fit in the back of my 1st gen street car project.

I too would want to see a 3-rotor car; aside from MRR and an FD that I spot sometimes, I almost never see RX-7s in this state at all. Stupid rust.

Why yes, that is almost completely off-topic.

OzFeTt

Howard,

thanks for the informative posts! you wouldn't have happened to model the FD suspension in susprog3d by any chance?? If so could you pretty please send me the .s3d file?! I'd be very interested in having a look at the camber curves etc.

Thanks

Rob
r_mcmahon@bigpond.com

Howard Coleman

iTrader: (6)

hi rob,
i just removed the front spring/shock after noting ride height ( 25 inches at the top of the wheelwell) and moved the wheel into compression measuring the camber at each half inch. i don't have the figures near me at the moment but can probably find them. there isn't alot of data as there were only about 8 data points. the data, however, is pure racecar as to camber gain. that's why the fd is such a magnificent animal. it is a racecar suspensionwise.

i am getting closer to my bumpsteer measurements. the delay has been my engine builder.

howard coleman

cabaynes

iTrader: (4)

i am now subscribed to this thread, i look forward to hearing the results of your findings


ps, howard... youre the man

Herblenny

iTrader: (13)

Howard, Any updates on the bumpsteer measurements??
I'm about to start my 20b project and collecting information at this time.. Any info would be greatly appreciated..

What's your thought about keeping stock sub and working everything around it??
or do you think going with custom subframe is ok??

Howard Coleman

iTrader: (6)

well, it's only been a year or so since i started this thread...

as you may recall i was going to measure the bumpsteer on my friends 20b fd.

his car runs either a pettit subframe (or something similar) w extended steering arms off the upright. it was built, i understand, by a mazda engineer in florida. dick has owned it for a year and a quarter. i did drive it to the

rotary revolution

(you are all going this april 21st, right? dick's 3 rotor will be there as well as my twin To4 2 rotor)

so i have about 700 miles with it. it has a T66/ fresh Pettit motor/haltec e11.

as is, the car drives poorly. as soon as you turn the wheel. it has toe in bumpsteer. i did a bumpsteer on it and it specs out like it drives... at one inch of bump the toe in is .249! at 2 inches .288 and 3 inches .531!!!!!!!!!!!!!!!!!!!!!

here's what happening:

with toe in on bump, the outside wheel turns in response to the steering wheel. then the car rolls and the front outside wheels goes into bump starts turning more, which creates more roll and more turn in. yikes!

in order to keep the car from continuing this spiral a counter turn with the steering wheel is needed to correct every turn.

having raced and designed and built SCCA tube frame (mazda) racecars for 22 years i can not tell you how bad this dynamic is for the car and driver. if it was my car i would not have driven it around the block before fixing it.

bumpsteer should be toe out and be at most .01 to .02 per inch of suspension travel. this car has half an inch toe in!!!!!

i do not know if it is Pettit engineered or a knock off, or just someone's project so i am not laying blame anywhere. i actually have the Highest Regard for Cam Worth.

i will be fixing Dick's car when i get the time... it will envolve relocating the outer steering pivot point downward.

having lived with the car for a year i do think the 20b converted fd, if properly executed, is an excellent car. the t66 makes 68 lbs/min so if properly tuned approx 530 rwhp should be on tap with a broad torque curve. yes, you could run a bigger turbo and make a bunch more power.... i am just not sure what you could do with it as it is pretty wild as is.

i will report back as to my efforts to dial out the toe in bumpsteer.

howard coleman

Kenku

Mein gott... that's not good at all.

Rotary Revolution is... pretty much not going to happen for me. As a broke-*** college student, both aspects cause problems... I haven't got money to get to / stay at Indiana, and I think that's pretty close to finals.

rotaryfreak3

Great thread!

Personally, I have never liked the Teins. From all of the shock dynos I have seen, they(along with most of the JDM brands) seem to have little to no adjustment range. I vastly prefer to use a shock from Koni with Ground Control coil overs.

However, most of my knowledge comes from Hondas.

paximus

iTrader: (1)

let us hope that its not the pettit subframe and spindles....or i'm screwed with a handful of other guys...

rx7tt95

The Tein's have plenty of adjustment range. I came from a GC/Koni combo to the HA's and the Tein's have a wider range of adjustment, offer less noise (stock top mount) and have been more reliable. The piston diameter and shock body diameter is also much larger on the Tein.

yodaddy

haha you're screwed anyway when are we gonna get that thing done?

rotaryfreak3

Is the adjustment range just your opinion, or have you verified it with a shock dyno? I have seen the adjustment range on shock dynos for both, and the range on the Teins is very little.

What problems did you have with your GC/Koni setup that make you say they are unreliable? What model of Koni's did you have?

What makes you say that a shock with a larger piston diameter and shock body will always perform better? Have you verified this with a shock dyno?

BTW, don't take this the wrong way. I make these comments with no malicious intent. Just trying to have a healthy debate.

rx7tt95

Don't have the energy to debate. Sorry. I can say that I've used both on autocross and road race courses and the Koni's were dead in a bit over a year while the Tein's are still going strong. The top mount on the GC's is solid and transmits lots more NVH into the chassis which is quite unpleasant on say a 5+ hour trip. Just little niggle stuff with the the collars, nuts, bolts which seem to be a PITA. Finer adjustments on the Tien's in positive stop increments. The shock dyno I saw of the HA's seemed to have a better match between compression and rebound whereas the Koni's have way too much compression right off the bat in the 3rd gen app. The Teins are downright compliant on their softest setting where the Konis get hard at 2+. Larger pistons flow more fluid. Most of your high end shocks are monotube/large piston because of the inherent advantage to a larger piston. And above all else, the Teins were less expensive. The difference between an FD-specific Tein and a Honda-specific shock is probably quite dramatic if as Tein says, each shock is designed for a specific vehicle.

Howard Coleman

iTrader: (6)

re tein HA range of adj...

i own a shock dyno and they have a huge range... from much softer than OEM to the point where they will break your front windshield.

i recommend the HAs based on their build quality, spring rate and shock valving.

for further info check a recent thread started by Jason on a group buy on the new Apexi Exv coil overs... there's alot of tech in the thread. it is in the third gen section.

howard coleman

speedx7

car looks great and also good luck on your future races

RotorMotor

iTrader: (5)

so howard..... there are or are not bumpsteer concerns with the pettit subframe/spindles??? i have the subframe, and am about to go ahead and order the spindles... (my motor is still not yet mounted though)

Howard Coleman

iTrader: (6)

rotor motor,

since the only fd 20b car that i have bumpsteered was Dick Lamberts i am unable to answer your question. you probably have read a parallel thread entitled "bump steer" there may be additl info there.
i will say this. i have known Cam Worth since we raced together at the Runoffs in the 80's. i have had many discussions w Cam as to suspension tech and he knows it all. Cam has had, perhaps, more experience w 20bfd's than anyone and it is my opinion that he does things right. for example i put over 40,000 miles on one of his motors and it still had 17 inches of vacuum. i have referred many people to him for engines and i have never been disappointed. i believe that someone copied Cam's subframe and steering arms and missed the steering arm dimension by, say, 1/2 inch or so... that's all it takes.
i would be very comfortable w Cam's setup.

howard coleman

RotorMotor

iTrader: (5)

ok thats the info that i needed to hear.... ok now if i could FINNNNNNALLY get my act together and mount the freakin motor in the car id be on my way!! thanks again howard, you are always a big help. -heath

The Blur

Heres a somewhat on topic question. How many of you still watching this thread run poly suspension bushings? From FD drivers I always hear nothing but bad things about the polys made for our cars. But even just recently we put polys on my friends E30 BMW in his rear subframe which made a large difference in keeping the entire rear suspension from twisting in hard corners. And yes I know about the extra vibration from more solid mounts, but I wanted to know from a road racing standpoint, etc.

TIA
Rob

Alpine

Hi Howard,

Have you had any issues with the HA damping adjuster? On my Flex the damping adjuster have a vague feel, you are not sure if it's clicked into place. Also one of my Flex had the damping adjuster frozen solid right after installation, Tein has repaired the problem, but it certainly doesn't inspire quality confidence in Tein's product. The Flex is a twintube shock, the damping seems different from HA.

Can you take a look at look in this file, on page 11 it has the dyno graph for Tein HA, is it the similar to your RSR coilovers?
http://www.tein.co.jp/ti/hr/hm32.pdf

Here is the Flex dyno graph for FD, too bad it doesn't show the adjustment range, however on the Flex dynograph for Subaru WRX, it's rebound adjusted only. In a twintube shock, I wonder if you could adjust compression via top adjustment ****? Isn't the compression damping in a twintube controlled by the foot valve located at the bottom of the shock, which is not accessible by the top adjustment ****.
http://www.tein.co.jp/ti/flex/6m32.pdf

Randy

Howard Coleman

iTrader: (6)

replacing oem bushings w poly/nylon bushings offer significant seat of the pants performance gains..

the key w the FD and nylon bushings is to only use them where they are truly needed.

uprated bushings are needed at the differential and the front of the lower longitudinal link at the rear suspension. both are large rubber bushings and serve a critical purpose (power and braking).

you can swap out the entire lower link and trade it for a chrome moly tube w a rod end. that is just fine and a touch less maintainence.

all the power and braking feeds thru this huge rubber bushing and when it degrades you get slop which toes in and out the rear tire.

an absolute no no.

the diff bushings are similar in that they are large and rubber. they promote chassis bounce. note as you jack the car up using the diff that it moves up almost an inch before the chassis moves up.

the rest of the car, with the poss exception of the swaybars, doesn't need anything but oem bushings.

since neither the diff nor the lower link bushing carries vertical load, NVH is hardly effected by the swap.

maintainence is some grease twice a year and cranking on the thru-bolts to make sure they are tight.

there is minimal loading on the rubber A arm bushings and little deflection so i don't see a need for change. the rear toe links have a miniscule amount of rubber surrounding a rod end (spherical- pillowball) bushing and do need to be checked for the rod end developing slop. disconnect one end and pull on it to test. if you feel any "click" either replace the oem bushing or buy the nice Rotary Extreme product. both perform exactly similar.

the diff and lower link bushings, when replaced, will result in a significant performance both for road racing, drag racing and aggressive street driving.

howard coleman

Carl Byck

The HAs, are they newer, or well used, same question on flex, they all start very stiff, and loosen up over time. Count on rebuilding these as often as any race shock, Carl

alberto_mg

i wonder if howard will ever get tired of posting the above info. i've read it on just about every suspension post he has made and i enjoy reading it each and every time

i think some day when i'm bored, i'm going to search through all of howard's posts and compile a "Everthing you ever wanted to know about the FD suspension" document.

thanks for the great info howard! this place wouldn't be the same without you.

Alpine

One of my Flex shock got its damping adjuster froze right after installation into the car, before I even let it down the jackstand, let alone using it.

The Blur

thank you very much for the detailed explanation, that helped greatly