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rotarypower wrote: ↑Sun Apr 26, 2020 6:35 pm

So going forward I've tentatively settled on 2 possibilities:
- 13b Turbo from an FC
- 13b-msp Renesis from an RX8

The 13b turbo has the advantage of easy power, somewhat easy fitting, especially if I went the FC front subframe route & being able to utilise a few of the bits I have lying around.
The downsides are the fact that I won't be able to turn up the wick too much without serious upgrades to the rear end, the engines cost a fortune now even for none rebuilt ones & a loss of low down torque due to the lower compression.

At the moment I'm erring towards the Renesis but here are some thoughts on fitting either of those two engines.

13b Turbo
- You need the engine & gearbox (as the FB gearbox won't last long with turbo torque)
- Custom driveshaft & gearbox mount
- If going FC subframe then the mounting is sorted
- If not then a GSL-SE front cover, Oil Pan & Racing beat mount brace
- S4 OMP (which I have) to replace the electric OMP with.
- Megasquirt or some other stand along
- EFI fuel pump, upgrade all the fuel system & hoses
- Turbo back exhaust.

I'm no expert but I did put a 13bt into my series 3 so here are a few of my observations...

13b Turbo
- You need the engine & gearbox (as the FB gearbox won't last long with turbo torque)As said, engines are expensive and mostly unknown quality. Gear boxes are also not cheap, TII starter also needed
- Custom driveshaft & gearbox mount £120 ish for a custom prop then you need to fab a mount, a right ball ache to get it lined up
- If going FC subframe then the mounting is sorted Loads of people had done this, not so many have done it successfully. Sounds easy but is anything but
- If not then a GSL-SE front cover, Oil Pan & Racing beat mount brace GSL-SE pan cost me £250 landed, gaskets etc to swap the front cover and refit the LIM UIM, Injectors ect £150, GSL-SE front cover £180 landed, made my own engine mount £20 to bung the welder
- S4 OMP (which I have) to replace the electric OMP with. Cable and fittings to operate OMP from throttle body
- Megasquirt or some other stand along MS2 cost £350 landed More user friendly ECUs out there Mapping / tuning costs..... engine sensors to suit ECU inc, CLT, AIT, lambda, plus a wideband.
- EFI fuel pump, upgrade all the fuel system & hoses All of these plus a swirl pot, you can use the OEM pump as a lift pump
- Turbo back exhaust. Plus turbo manifold and wastegate and maybe a new turbo unless you plan to use the TII turbo with the Mazda specific flange which limits your options to upgrade /replace the turbo at a later date
Front mount intercooler & pipework £200 ish unless you want to use the stock TII I/C but then you'll need to modify your bonnet and it's not as good as a FMIC

There's also all the other stuff that you will need but dont think about but which all add to the cost...
TII clutch.... you might as well fit a new one while you're in there
Clutch slave
Gear oil
Engine oil
Antifreeze
Oil lines and unions to and from the turbo ( return tapped into the front cover)
Water lines to and from the turbo
Parts to mod the throttle body

Some of these are more expensive than others but the costs still add up.

I think the two options are so far apart in terms of end product it depends what you enjoy in a car.

If you are after an adrenaline shot - 13bt
Want to wring it’s neck and not be close to imminent catastrophe - renesis

I don’t like the renesis engine, if it were me I’d substitute that for an s5 on throttle bodies or something similar. At least then if you want to venture into a ported motor then you’ve got a good base to start with.

For what it’s worth regarding rear ends, I only ran an LSD and semi slicks with my 397rwhp and it hooked hard, you could just go 4 link if you want a play. I do recall an FC or FD rear end being grafted in one but obviously it’s a whole lot of work for a weekend fun car.

Your money and car though obviously, just my 2p.

Cheers for the input guys, welcome as always.

I'm erring towards the Renesis, its pretty reliable if actually looked after it & I think a FB with one in will still be a quick car, if in the future I did go down the route of big power, as a lurker on the Rx8 board a few people do seem to have Renesis turbo setups working quite well with decent reliability now. (expensive though)

Although packaging might be harder on the FB.

The IRS is most likely something that won't happen, but it exists on my 'dream' FB.
I've not see many people do this in what I would consider an acceptable fashion on many car projects.

Project Binky obviously, but their level of fabrication far exceeds mine & if you think about the time that's gone into that car, its not affordable unless its a personal project.
I do actually have stash of photos from peoples IRS conversions on the FB. I know of only 3.
- Miata IRS
- S13 / 14 IRS
- RX8 multi-link IRS.

Of all those the only I've seen with acceptable fabrication was the S13 one & they did a full boot floor pan replacement to make it work. It passed engineers inspection in NZ and is legal and road worthy though.

The other two I highly doubt would pass any inspection in the UK.

I'm a way off even an engine swap yet, that comes after I've finished dealing with the rust & corrosion, refreshed all the suspension bushes / shocks & springs / top mounts etc.
Then I might as well get the interior so that its a pleasant place to be / refurbish the heater blower etc.

Who knows, I may even be satisfied with it in standard form like that.

Okay, so I've managed to have a days leisurely work on the RX7.
First order of business I decided was to get the the rear end stripped away so I could see what I was dealing with rust wise.

First get her jacked up to a decent height & onto some axles stands. The axle is a handy jacking point.



So I started unbolting bits.


Then I stopped taking photos and just carried on, getting to this stage was a real effort, every single bolt was (naturally) completed rusted & seized, some of the suspension arms are still on the car pending me getting some new tools to help get them off. (We had a break in last year & all the large size 21mm etc spanners were pinched.)


With as much unbolted as I could at this stage I took a load of photos to chronicle the current condition of the underside & suspension mount points. I think 'needs work' probably summarises it. Or 'Rusted to sh*t!'.









Basically the suspension mounts both need repairing, the sill on the passenger side while appearing sound to start with made some ominous creaking and rust crushing noises when I lifted the car on it to level it off better (using a proper sill protecting rubber puck), I really need to bare metal it all as I suspect the arches may (will) need attention.

I also need to sort out this under the back bumper.



I then decided to strip out the rear interior to see what I was working with, I was quite surprised to find the nearside side rear seat bolts not only completely seized, (the heads sheered off when undoing) but there was a hole rusted through the back of the rear seats!!




I'm unsure if the rear seats will be going back in, but considering that's a foam filled seatback, welding it up could be interesting.

Next up with the rear interior out I could access the inner wheel arches, predictably (and the photos aren't great because I forgot to take them until after dark) holes in the inner arches, I was able to make these considerably larger just with a screw driver, so more rust that needs to be cut out.
C'est la vie.





Also under there the rear fuel pipe spider thing looks in need of immediate replacement, along with the brake pipes, very glad I'm doing this now, safety wise it will definitely be worth it.

*Mini rant* Why did Mazda make lower arm link mounting points in such a way that you can't get a socket onto the nut end!? Having to go out and buy a large spanner to do the job.

Also in a side not the IRS idea I had 99% sure won't work without cutting, the actual amount of space under the rear of the FB is very little. And while I suspect it could be made to fit without cutting the rear seat back, the frame rails would have to be sectioned almost back the floor itself which would be a big loss of strength without engineering suitable additional reinforcement to transfer the loads.

Yeah I don't think it will fit. Not even with my biggest hammer.

Looks like you've got quite a bit of work on your hands there!

Definitely!

Been meaning to learn to weld for a while so now's a good a time as ever.
I only put the MX5 subframe under their for fun, its been kicking about the garage since I sold my last MX5.

Obviously I'll practice my welding on none important bits off the car, I have some old body work panels so I may have a go at chopping them up and welding them back together again to work on my technique.

POA for the rex is now to get the remaining suspension bits off, drop the fuel tank, rear exhaust, pull the prop shaft (to get it out the way) and drop the fuel rail assemblies.
Bare metal everything under there and a coat of Electrox so I'm starting from a clean slate.
Then start cutting out rot.

For the upper link mount I think the best approach is going to be to drill the spot welds holding the plate on out, same for the other bits so I can replicate them off the car, one side at a time so I've got something to go off.

In between other jobs found more time for the car today, loving these light evenings.

So still waiting on some new tools to arrive so I decided to break out the spot weld cutter & have a look at the right hand suspension mount.


Yeah its not looking great & there's some kind of hacked on repair there.



At this stage with just a few spot welds drilled out it was already feeling pretty damn flimsy.



A little bit of working back & forth and out it comes. Carrying a chunk of the inner wheel arch as well!


Yeah I think that is FUBAR.

Popped across the river to pick up some gas, welder should arrive in the next few days.


Removed another suspension bit as I was fed up waiting for tools. Because I'd weakened the area by removing the mount, I had to get a bit creative.
Got it out though.


Dropped the fuel tank, I forgot to disconnect the fuel sender (oops), the fuel lines I deliberately cut.
In part to make it quicker, but mainly because I didn't want to be tempted to reuse them when I reassembled it.


Dressed back to good metal in the arch and cut it out using the angle grinder, there's a little more to cut out yet, and some of the back seat to be done. Fortunately I didn't need to cut into the swaged area.


Exhaust came out relatively easily (apart from having to remove it all in one go from the manifold as it wouldn't split) but I had to get some shears in to cut the last rubber off as access was basically impossible. Combined with rusty fasteners & I ran out of patience.
Its surprisingly small diameter tubing.
Obviously I had to start the car with it removed, seriously loud! I hope my neighbors appreciated it as much me.



Finally some pics of the current state of play underneath.



Touch wood I can get everything else from the rear end removed tomorrow & get to work on grinding back to bare steel & cutting rust.

(I've a strong suspicion that the fuel tank is completely gone, not only are bits flaking off it everywhere, when I poured the remainder into jerry cans, there was fuel also pouring through the seam in the tank somewhere. )

All too familiar! good work so far and good luck getting on with the repair, fair play for having a go yourself, I had the rear upper arm repair done by a garage near me.

Yeah unfortunately that is all pretty standard for these cars. It's a horrible sight to see and an even more horrible job to sort out . I done mine a few years back. Nice progress overall though aye!