bbeachy

...but has anyone here ever managed to build an independent rear suspension for the 1st gen. I have owned 6 rx-7s, including 5 SAs and an FB. One thing I have always hated about SAs is the truckish/mustang-like/camaro-like rear suspension, and so with my current car, I plan to re-engineer the suspension, but if anyone has successfully done so before, I would greatly appreciate some insight. I know that Mazda tried unsuccessfully to do this before deciding to build the FB from the ground up, but I think it's possible anyway. I have been considering Z06, miata and FD suspension parts for this, to keep costs down somewhat, but I don't really care if it's expensive, since I plan to make it about as fast as my 300zxTT.

Hades12

One of the guys here is putting a miata IRS into his FB. The thread gets bumped every few weeks.

RotaryAXer

iTrader: (4)

You can go through all the work but if you are just looking for handling there is absolutely nothing wrong with a well sorted live axle. It bothers me every time someone assumes that it is entirely archaic and obsolete.

If you what some tips to make a 1st gen handle well check out www.gforceengineering.net. With the panhard and tri-link and the correct spring rates you will have a very predictable, well handling car. Far easier and way less expensive than IRS.

IRS is cool but in all reality if you don't have a true, thorough/complete understanding of suspension design and vehicle dynamics it will more than likely end up less predictable and worse off in most respects than the stock setup.

You would need to have a full working suspension program and a huge amount of time to figure out all of the nuances that make a car handle well. It goes well beyond just throwing a miata subframe under the car.

It is a good idea at its root but in all reality there are better things to spend time and money on in my opinion.

Also, what are you talking about when you mention Mazda considering it before building the FB from the ground up? I don't know what you are refering to but if you can show me something I would be very interested to see it. The FB was by no means a ground up redesign. I don't know the history thoroughly though. For all I know they did consider a ground up redesign. Also, the FB rear is essentially the exact same as the SA.

bbeachy

I meant the FC, not the FB when I was referring to the redesign. Mazda considered doing an "evolutionary" redesign of the FB at the end of its product cycle, before going ahead with the ground-up redesign, which became the FC. Sorry for that, and I also forgot to mention that I am a Mechanical Engineering major at Texas Tech, have an associate's degree in automotive technology, and have been racing cars for 12 years and fixing them for 15. I DO understand the skill level involved here, and of course, as I mentioned that Mazda had no luck trying to do the mod, I am well aware of how difficult it will be to do it successfully (lots and lots and lots of R&D). However, I am stubbornly adamant about doing this, since the current rear end will not hold up to the planned 500bhp I plan to do during my build-up. I plan to keep a relatively stock appearance on the outside (except wheel, and mazdatrix front and rear fascias), but I want to bring the interior and drivetrain up to more modern specifications, including a new engine, and maybe even a 6-speed tranny, with LSD and IRS. I know many people think it's not worth it, but I'm all up for the challenge, even if the result doesn't seem "worth the time and money." It will still be worth it to me. Did I forget to mention that I am currently on the Formula SAE team at TTU- we have to design, build and then race a formula car that is sorta like a formula ford or formula mazda. I guess my point is, I am well aware of the fact that a lot of people who don't know much think they can simply "bolt-on" an IRS, and have a better suspension, but I think I can make it right. so, back to my question- WHERE CAN I SEE WHAT OTHERS HAVE TRIED?

bbeachy

I checked out the site w/ the Miata subframe retrofit. I don't like it. I already figured that i would have to design my own subframe, but I'm interested in using the aluminum control arms from the cars I mentioned above. Maybe I'll use aluminum or titanium for the subframe. I have a friend who has lots of professional experience welding Ti, but I don't particularly like the way the it tends to gall in contact with steel. So, even though it may be slightly heavier, a tubular aluminum subframe should work. Gonna have to measure the suspension bits for some of those cars, and then check all the measurements for the SA's rear end, before modeling the suspension with a computer, then "testing" the camber and toe control, before committing to this. There- does it sound like I know what I have to do, and that I might be able to do better than other people have? geez!

cincoletra

Sounds like an awesome project!! Hey, you live in Lubbock, TX! I lived there for two years. The wind and dust storms sucked, so we moved back to Florida. Good luck with the project, and post updates!

RotaryAXer

iTrader: (4)

Is this the thread you saw?

https://www.rx7club.com/showthread.p...8&page=1&pp=15

All is forgiven on the FC/FB mix up.

Also, I never really assumed you didn't know what you were doing. But, how else would I have approached the issue? A word of caution may have gone a long way in helping you if you didn't have a good understanding already. At 4 posts I had no idea who you were or what your experience level was.

With that all out of the way...

I haven't given much thought to anti squat/dive, ackermann, and the million other things that need to agree front to rear. What do you plan to do up front?

I think the beauty of the Miata subframe is that it is only attached by six bolts and the entire rear suspension and diff are a self contained unit.

I haven't been under a vette in a while but I don't know how you would be able to adapt any of its bits and pieces to any other car.

I think the FD and FC for that matter would be even harder to adapt than the Miata.

This will be a very interesting project to follow.

bbeachy

I'm thinking about getting upper and lower A-arms all around, so that coilovers will make sense. I expect that this will take at least a few years, so don't hold your breath. Keep in mind that I am in ME school right now!
If you have ever tried to do an alignment on an SA ( I did in auto tech school, on my '79), you would know how tough it is (impossible?) to get everything just right, which is one of the top reasons why I want to do this.
I haven't begun yet either, which is why I wanted to see what others have tried. Just trying to do a little homework on the subject.
The Miata seems like a good choice for parts so far, since the suspension travel should be about the same. As far as I know, there aren't many performance cars out there that have decent wishbone suspensions that I can find in boneyards, besides what I have mentioned.
The front subframe may have to be re-engineered for a wishbone suspension as well, since there are no supports in the wheel wells.
I know what I want (my performance target is the C6 ZO6), it's just getting there that will be so much fun! Besides, I KNOW I build it up for much less than the price of a new Corvette, and since I'll be able to buy a Corvette, it shouldn't be so hard as far as money. Sound better yet? I'm expecting to spend up to about $10,000 on the suspension, with my own work on the engineering end, but including the prices for all the fabrication and hard parts I will have to acquire. Then the drivetrain should get up to something like another $10k+, and will be nearly as tough to build. In the end, I expect to have a better handling, faster car than a Corvette for about $25-30k.

jgrewe

iTrader: (1)

Sounds like a fun project even if it makes the car any better or not. I was sitting here imagineering the set-up and while the miata rear would be easy I would go grab some front spindles off of a big FWD car and start from there. That would give you big brakes, toe adjustment, lower ball joint point and you could fab a way to attach an upper ball joint and still give you camber adjustment. Is the millenia FWD?, that would keep things Maz. You might even be able to use a stock lower arm off it then figure your upper arm to give the geometry you want. Don't reinvent the wheel if you don't have to, there are a bunch of cars that have subframes in the front that you could modify or copy geometry off of. $100 bucks at your local U-Pull-It could get you 3/4 of what you need. Then go buy a sawzall...
Oh yea, find yourself an engineering test shell to cut up first, then do your good car.
Have Fun

13btnos

iTrader: (1)

It's an FD but it might give you an idea https://www.rx7club.com/showthread.p...ghlight=1000hp

bbeachy

I might have to make a whole new tubular front end (think nascar, but with dimensions suited for the stock bodywork), in order to get a decent front suspension setup. That would help to make the chassis stiffer, and allow for greater drivetrain torque without concern for twisting too much.

bbeachy

BTW- I'm thinking about using an sr-20det 4 cylinder turbo Nissan motor to replace the 12a. I know you guys probably hate the idea, but at least it's not another V-8 conversion. This way, I'll be able to make about 500hp at the crank, with less reliability problems than a 13b-rew would have with similar power. I have known several guys with modded FDs and with modded silvias, and the silvias are more reliable. VG-30DETTs from 300ZXs are too, but I want to keep the weight down. I almost bought an FD before I got my Z, but was turned off by the number of cars that had had their engines replaced with so little mileage. I hope the next RX-7 (if they build one?) won't be the same way...

tasty danish

iTrader: (5)

500hp on the sr20det?
i suppose it's possible but... yeah right.
250-300 is typical, these are with pretty serious setups, sure there are 2 or 3 people around with >400hp, but it's $$.
and i bet you could out do it with a rotary for cheaper, and it'd be simpler, and did i mention it's a rotary? what other car...
ok, now honestly, i'm not a raving rotor ****, but if you expect 500hp... i'd look to something more promising, if you want to stay nissan, a slant 6 in a 7 would be kind of cool (skyline engine), or... OH dude: a twin turbo SHO engine would totally rock *****, best swap ever. you could do 500hp at 8000rpm easy (ok... so that's never easy, but you get my drift) with that, and the internals would take it.
if i could give you any advice, i'd say ditch the irs setup and focus on making it a really really bad *** ride in other ways.
you arent ever going to see the returns of irs, unless you like snapped halfshafts, increased wheel hop, and more particular part selection.
aren't there guys around here with first gens pulling something knuts like 1.5g's?
your creative talents could be put to better use, remember cars don't build themselves overnight, anything you do will take forever.
good luck however you do it.

Paradox

iTrader: (1)

ive seen a SR20 do 500HP, ofcourse it lasted all of maybe 3 dyno runs

tasty danish

iTrader: (5)

exactly

13btnos

iTrader: (1)

Sorry Bbeachy but you can build a reliable 500rwhp 13B. Just like any other motor you have to properly build the motor to make it reliable. Most people who just slap bolt ons on their motor and don't actually build up the internals end up blowing up their motors. And those are the same people that complain of the rotarys reliability. Yes a rotary is more finicky than a piston but if you know what your doing and build it properly you won't have any issues. My friends car put down 580rwhp and he made over 90passes in the 1/4 mile before freshening up the motor. 90 passes is a lot of abuse on a motor especially at 28psi of boost. Abel Ibarra claims the same with his old 13B setup but making in the neighborhood of 800+rwhp 90+passes on that setup. Reliability issuses I don't think soo building issues are what cause failures. It's all in how you build and tune your engine that's what it boils down to. I'm on a budget building my car and don't have money to blow but I did not cut corners in building my engine. I have to make it reliable because I can't afford to have the motor blow up everytime I go to the track. And make it reliable making 600rwhp @ 30psi of boost pressure.

toxic_d

bump update