Stripping a Miata to the Sub Frames?

We built this at a shop i used to work at.

http://www.corvetterepair.com/Driveable/driveable.htm

Wally wrote:

the awesome sauce just dissolved my brain. I am now a bumbling idiot thanks to this forum.

DeadSkunk wrote: Jensenman, How much of the subframes went under the Opel? Or, did you just swap in the the engine and trans? I've been wondering how easy it would be to build a Miata GT by putting as much as possible of the mechanicals into an Opel.

The rear subframe was narrowed to fit under the Opel body, IIRC the rear track width was 51". The rear frame rails in the Opel were kept but the sheet metal between them was cut out and then cross rails were made from 2x2x .120 steel with crush tubes in the bolt holes at the correct positions. I used stock Miata rear shocks mounted to a crossmember made of the same 2x2x .120.

At the front, the Opel lower control arms were modified to accept the Miata lower ball joints. To keep the camber curve reasonably close to the Miata's, the Opel upper control arms were shortened to have the same percentage relationship to the Opel lower arm as the upper/lower Miata (IIRC it was something like 71%).

I used Miata rear shocks on the front also, and modified the Opel double upper shock mount to work (you need to look under one to see what I mean). I used the Opel steering rack with Miata outer tie rod ends. The Opel inner tie rods are hollow, so I cut the ends off of a pair of Miata tie rods, cut the ends off of the Opel inner tie rods, tapped the Miata pieces into the Opel piece till I got the length I needed, then welded them together.

The engine was a 13B NA rotary. I had all the really hard work done and was working on the floor pans etc when a situation arose where I needed quick cash. I had to sell everything off before I was able to complete and drive it.

I take it that the Opel is a narrower car than a Miata? I wonder what it would take to cut the floor out of an Opel and drop the body shell over a Miata undercarriage. I've seen a thread someplace where a guy did the same sort of thing by dropping a Ford Anglia panel over a BMW 2002 flooor. It took an awful lot of welding and fitting, but it was nicely done in the end.

DeadSkunk wrote: I take it that the Opel is a narrower car than a Miata? I wonder what it would take to cut the floor out of an Opel and drop the body shell over a Miata undercarriage. I've seen a thread someplace where a guy did the same sort of thing by dropping a Ford Anglia panel over a BMW 2002 flooor. It took an awful lot of welding and fitting, but it was nicely done in the end.

Would probably be easier and better to just graft the Opel front and rear ends onto a munched Miata. Keep the modern everything inside and get the styling of an Opel GT. Someday I'm going to do one, after I finish up the other 743 or so other projects bouncing around.

alex wrote:

Grtechguy wrote:

Surely somebody's done something to make one of these driveable.

Anyone know of a locost-ish tube frame design for this? $6.5K for a '98 roller on ebay...

I wonder if you can make a Miata frame under one of these (w/ some shortening)

http://www.modernmicrocars.co.uk/prices.html

Edit: ignore that. The Miata is much wider then any of those cars.

I wonder if you could do this with a 924/944. That would be a super awesome start to a tube frame car.

Front clip out of ... anything. Engine out of ... anything. Make a torque tube and walla, you now have an imitation C5 chassis for a fraction of the cost.

Considering what I have in the junkards around here, 4.6L Hyundai V8 from a wrecked Genesis plus front clip out of a Daewoo Prince, minus crappy autobox, plus tube chassis equals destroying everybody at the track ....

I realize this thread has been dead for a long time. But wow this is cool.

How hard would it be to make the Miata engine run if you did just build a tube frame around the subframes? Would you need a stand-alone set up or could you use the stock ecu?

also do the shocks/springs have to retain their original “tilt” to maintain the correct suspension alignment or could they be angled a little one way or the other. 

In reply to Somebeach :

It could run on the stock ECU fine. There’s a little wiggle room on shock position, which varies slightly based on your final ride height vs. stock. What you don’t want to do is position them too vertical and create a falling-rate suspension. 

Somebeach said:

I realize this thread has been dead for a long time. But wow this is cool.

 

How hard would it be to make the Miata engine run if you did just build a tube frame around the subframes? Would you need a stand-alone set up or could you use the stock ecu?

 

also do the shocks/springs have to retain their original “tilt” to maintain the correct suspension alignment or could they be angled a little one way or the other. 

You're describing an Exocet. It's not that hard to make it run. The older the car, the easier it is.

If you tilt those springs/shocks too far, they start to hit the control arms or bind. It's a double wishbone suspension so the wheel kinematics don't change at all, you just have to make sure you don't put side load into the shocks to create stiction.

Hmmm...  Way to go guys.  You have me looking at rusted out Miatas again.

Keith Tanner said:

Somebeach said:

I realize this thread has been dead for a long time. But wow this is cool.

 

How hard would it be to make the Miata engine run if you did just build a tube frame around the subframes? Would you need a stand-alone set up or could you use the stock ecu?

 

also do the shocks/springs have to retain their original “tilt” to maintain the correct suspension alignment or could they be angled a little one way or the other. 

You're describing an Exocet. It's not that hard to make it run. The older the car, the easier it is.

If you tilt those springs/shocks too far, they start to hit the control arms or bind. It's a double wishbone suspension so the wheel kinematics don't change at all, you just have to make sure you don't put side load into the shocks to create stiction.

Thanks. And stiction is just binding Of the shock travel?  For us beginners. 

In reply to Keith :

So Keith, reviving an ancient thread, but relevant to my current plans. So I want to upgrade our NA 1.6 miata to a 1.8 manual transmission and torsen rear, why not just do as you are doing above and drop the entire drivetrain with subframes from our 1.8 manual car and then do the same on our 1.6 automatic and the just re-install the 1.8 chassis on the 1.6 automatic and then use the FM kit for the 1.8 conversion parts and a 1.6 ECU to complete the swap? Seems faster than pulling all the parts individually to accomlish the same thing? Plus I can put the 1.6 chassis back on the wrecked car so it is a roller as I have a buyer for it when I am done.

Is there a way to make the wheelbase of the "skate" longer or shorter ?

In reply to californiamilleghia :

Custom PPF doesn't seem that hard

SVreX (Forum Supporter) said:

In reply to californiamilleghia :

Custom PPF doesn't seem that hard

its early in the morning here , Whats a PPF ?

thanks

Kind of off topic but at would there be VIN issues with swapping tubs and drive lines?  I assume the VIN travels with the tub?  

In reply to californiamilleghia :

PPF = Power plant frame? Something like that.

On a bunch of sporty Mazdas, there is an connector between the back of the transmission and the differential that ties them together and holds them in a specific relation to each other. Hotlink from the Exomotive site:

dean1484 said:

Kind of off topic but at would there be VIN issues with swapping tubs and drive lines?  I assume the VIN travels with the tub?  

I don't think there are any issues, no different that if you put a different engine, transmission or diff into your existing car. The VIN tag is on the dash and stamped into the body shell, the fact the engine numbers don't match are not an issue

SVreX (Forum Supporter) said:

In reply to californiamilleghia :

Custom PPF doesn't seem that hard

Not compared with a lot of the other insane stuff that goes on here...

dherr (Forum Supporter) said:

In reply to Keith :

So Keith, reviving an ancient thread, but relevant to my current plans. So I want to upgrade our NA 1.6 miata to a 1.8 manual transmission and torsen rear, why not just do as you are doing above and drop the entire drivetrain with subframes from our 1.8 manual car and then do the same on our 1.6 automatic and the just re-install the 1.8 chassis on the 1.6 automatic and then use the FM kit for the 1.8 conversion parts and a 1.6 ECU to complete the swap? Seems faster than pulling all the parts individually to accomlish the same thing? Plus I can put the 1.6 chassis back on the wrecked car so it is a roller as I have a buyer for it when I am done.

I have used that technique myself in the past to convert a 1.6 to a 1.8. Just jack up the Miata and slide the new drivetrain underneath :) You get the larger brakes and stronger diff as a bonus.

On an automatic car, you should be able to retain a 1994-97 throttle body as it has the correct TPS for the automatic ECU.

And as noted, a wheelbase change is fairly trivial. Even more so if you decide not to retain the PPF.

Thanks Keith, that will be my plan later this year!