Felix Wankel

The whole idea. No offense, but honestly, you couldn't even fix your carb, yet you want to re-engineer the whole rear geometry of your car? Come on now.

V8kilr

check out this thread i just posted in for all the gear ratios i just posted for rear ends,

gear ratios


the best tranny imo is a
1987-92 NA


that rear end is gonna be a bitch to mount,
i heard a couple did the swap though,
would love to see some pics.

the suspension is also way better,
its independant rear,like the vette

plus you will have 5 lug

79+80_rx-7

I am better at fabricating then fixing a carb. I dont know **** about carbs. But if it wasnt me doing it, you would say it ok??? The hardest part, is FINDING THE DAMN CAR, IN A JUNK YARD. Why do people, underestimate me??? I know I can do it, I just gotta find the CAR, DAMNIT. I have a set goal, and I will follow through with it. I think it will be the easiest way to go. I am probably gonna stick with the T2 engine, and when it blows, I will unbolt it(gonna make bracket to except both 12a, and 13b) and I will slap a 12a, then do TWM EFI Should be fun, but I am gonna wait, until I have the 12a, before I "accidentally" blow the turbo engine up So, I will take pics, of the car , I will be tearing down before, and after And the parts that will be left over, I will part out, and get some of my money back Thank you V8kilr, and whoever else, that doesnt underestimate me
THANK LATERZ, Andrew

Felix Wankel

I don't care who is going to do it. Its not my car. Just don't expect me not to laugh when you cut the whole floor pan out of the rear of your car and never get it finished... Or do get it finished and wonder why the tires wear funny. Or why it pulls to one side. Or why you have a vibration. Or why you cant get the gas tank out now. Or where to get custom axles.

peejay

There is no benefit to the IRS (especially the crappy IRS used in the FC) compared to a well-sorted solid axle.

79+80_rx-7

Well, what car has good IRS???? I am just curious. I want to know, what are the benifits, of a good setup IRS, against, a GSL/ GSL-SE, rear???
THANX LATERZ, Andrew

Max7

First, Max out your rear end, then if you still need better handling, buy another car, hehe
Unless you have $ to burn, give up the idea
best way if you want is backhalf the car, tube frame it, that way you can make your suspension mounts were you want, use a viper rear end, they hold up good.
$30,000 later, it will handle like a dream, oh wait, you still have that 70's design front end, DOH!
time from a complete tube frame frontend to hold the Viper front steering components.
$20,000 later, wow! this thing scream! why do I only have 100HP to make use of this awsome handling, hehe

crafoo

I had always heard that a IRS was better for keeping traction on bumpy roads.

I've owned a TII and can say, be prepared for wheel hop even with new shocks.

Seriously tho, the 1st gen 7's have a pretty nice live axle setup. Why would you want to change it?

MIKE-P-28

iTrader: (1)

Can I go cry now No one likes my poor vert

jeremy

iTrader: (1)

ok, i'm going to call bs on that. maybe the fc's irs, but in general irs is far better for road handling. i think max7 had the best reasoning to why it wouldn't work in this case. you are the only person that i have ever heard to say that. basically you have defied every auto manufacturer, magazine, and track racer. solid axle will be fine as long as your on a smooth track. look at all major sports cars, or hell anything but trucks and suv's. all irs. now if you're drag racing, solid axle is better at this point do to it still being a stronger and more trouble free setup. it is also cheaper, so when you tear **** up you don't go broke throwing money at halfshafts.

peejay

That is exactly why a sorted solid axle is better than an IRS!

With a sorted solid axle you will have anti-squat. The torque reaction of the rear axle will work on the suspension and force the rear tires into the ground. Result - more traction! You can easily get over 100% anti-squat, which means when you accelerate the rear end actually rises up. Watch a drag racer launch - watch the rear tires get forced down OUT of the wheelwells. This isn't just a drag racing advantage, either - what happens when you're exiting a corner and apply throttle? Rear axle forced into the ground, you get more rear traction, and away you go shooting down the straight!

Now let's look at an IRS. There is no torque reaction against the suspension. The only reaction is the force of the hubs trying to move forwards. You can only generate about 25% anti-squat this way. Not as good, eh? Now let's look at the FC rear suspension. The trailing links angle upwards from pivots to the hub center, ESPECIALLY if the car is lowered. This means when the hub tries to move forward, the suspension will compress! This is PRO-squat and is exactly what you do NOT want in a rear suspension. When you accelerate it tries to pick the rear tires up off of the ground! No wonder you had wheelhop problems so bad even super-stiff shocks weren't a big enough Band-Aid fix.

My line of thinking on the bumpy roads aspect is, yes, a solid axle isn't so good on bumpy roads. But then, our front suspension sucks on bumpy roads too, since it doesn't have enough compression travel. Dragstrips and road courses and autocrosses are held on smooth roads anyway. If I wanted to fly across bumpy roads at insane speeds I'd get another Subaru with its nice long-travel suspension at all four corners.

jeremy

iTrader: (1)

ok, your only argument is anti-squat. true and more advantages in a straight line. i'm not going to pretend i know everything about suspension geometry but i'm looking at the people that do, the automotive engineers. if the put the pricier irs in all these cars, then they did it for a reason. bumpy also doesn't mean rally, but yes a wrx is fun pinned in a bumpy gravel strewn corner. since i don't have any other hard facts other the cornering traction, i let you explain to me why all major road race teams use irs. if they could get solid axle to accelerate out of a corner better, then hell, best of both worlds. why wouldn't they use the solid axle?

Felix Wankel

Hey, when its 80 degrees outside, the sunroof in my TII just isn't enough I'd love to have a vert, but the $600 shell of one I wanted got sold already.

Felix Wankel

MY TII handles fine. Also, it was SET UP for an IRS from the fatory. I think it'd be kind of funny watching an IRS transplanted SA getting its *** smoked on the road course by some good IT7 cars


I think you see so many IRS setups because people are moronic. About 2% could react to a solid axle car stepping the *** end out on them.

peejay

IRS has many advantages... It requires a lot less suspension room - more room for passengers, more room for fuel tank, more room for the exhaust (no need to snake up and over anymore) etc. The driveshaft doesn't move through much angle at all so there's less vibration. Also it requires less room because it doesn't move around. An IRS can be isolated better than a solid axle - mount the suspension to a subframe and attach the subframe to the body with bushings. And of course with the lower unsprung weight it will ride better. All of these are very good reasons for manufacturers and are why you're seeing IRS's even on trucks now, mainly for the better interior space so the floor can be lower but the other advantages are there too.

A solid axle does have significant benefits due to the anti-squat. And if you believe that corner exit is not important on a racecourse then you need to rethink that. If you can get the power down sooner, you will be faster around the course. Anti-squat allows this. Unfortunately, a solid axle takes up a lot of room, isn't so good on bumpy roads, transmits more noise to the cabin, etc so the manufacturers don't use it anymore. Plus there is the technogeek side - everyone "KNOWS" that solid axles are inferior, just like everyone "KNOWS" that pushrods are inferior, so people step up to spend more money for something just because it has a cool name, even though it may or may not work better than the "inferior" design.

The rear end skipping-out problem is not directly related to the fact that it is a solid axle. The IRS cars have a low roll center which makes the rear end's handling a lot more predictable. Mazda designed the RX-7 with a rather high roll-center in the rear so the car leans less, unfortunately it also makes handling less secure. Swap in a Panhard rod so you can get a nice low roll center. The car will lean a lot more though, and will plow like a pig even moreso than stock, so you'll have to put some very stiff springs in the rear (there goes ride quality) and you wouldn't believe the handling.

jeremy

iTrader: (1)

good answer, i wouldn't have thought of half that ****. but why racing teams? all the lemans cars, grand am, sports cars (which obviously are going to get whatever's best since rear seating, etc is not an issue) are irs. you can control the geometry of how the tire interfaces with the road far better with irs. you can control camber, etc, with irs far better then with a solid axle. it also seems that a solid axle car will try to lift its inside wheel and spin it more as the car leans and tries to lift the inner wheel via the axle acting as a massive anti-sway bar.

peejay

The axle doesn't act as an anti-sway bar. The anti-sway bar acts an an anti-sway bar. The axle, if the geometry is decent, will move freely throughout all of its travel and will not cause any binding.

Now, here's another place where Mazda screwed up. When they designed the rear suspension, they made the upper links rather short and canted at an odd angle. (I assume it's for clearance and fitment reasons) When the car leans over to a certain point, the suspension binds up because the geometry just doesn't add up - the upper links prevent the suspension from moving any more. This is the other half of the car's "twitchiness". (I had this happen just once, no it was not fun) You solve it by welding in a single upper link in the center of the diff, and throwing away the two stock upper links, or at least replacing the bushing material with rollbar padding so they don't do anything but satisfy the rulebook. Now the suspension can move freely to its heart's content.

Or you go with a torque-arm setup, which I plan on doing sometime down the road...

jeremy

iTrader: (1)

ok, but that still doesn't allow control over tire/road interface like an irs, especially multi-link. and i'm sure if it was that beneficial the audi and cadillac lmp cars wouldn't have irs. i'm not sying you haven't taught me a shitload about solid axle setups, but there is obviously something more to this.

by the way, i think my 79 just has one link on the diff. it attaches to the top center of the diff and then the left side of the unibody