Owner of two FB projects

[Cadfael]

Hello,

Just to introduce myself, I currently have two FBs on the go:

• B939AHB, a converted Elford Turbo car. Originally painted W1 Opal Green, partially resprayed by the previous owner. I have had the whole driveline off this car and have been slowly working my way through it. Car has been resprayed all over in Sunrise Red. I have purchased and fit new BC coilovers, and am currently looking at front ARB options - will likely use a splined bar. Big brake conversion in the works. Rear end is now fully rebuilt complete with an MX5 1.8 Torsen, Watts link brace, and T3 heim-jointed upper links. engine has been fully rebuilt with a mild streetport, ceramic coated rotors, and a shimmed oil pressure regulator. Assembled with a lightweight flywheel. Distributor has been removed and an RX8 style trigger wheel added to allow for electronic ignition using FC coils. The turbo manifold, wastegate and turbine housing have all been ceramic coated, and the housing has been reprofiled to fit the slightly larger trim T3 turbine wheel (original one had melted!). The wastegate has been reamed out and the actuator replaced with one opening at 0.6bar. The manifold has been drilled and tapped for a pyrometer. The intention is to build a hybrid turbo with a larger compressor, and use a water/methanol blend (ratio TBC) for charge cooling at boosts higher than 0.6bar (triggered by pressure switches on the Elford manifold that was once used to switch dizzy advance), maybe in a two-stage configuration. Will try and use the standard HIF44 carb for fuelling at first but if this proves fruitless then I shall switch to a 2" SU and have a larger 'intermediate block' (between carb and turbo, bolted to Elford intake manifold) cast to match the carb's bore. Still need to have an exhaust (including downpipe as Elford standard is too small) fabricated.

• C999EWN, purchased as a rolling shell with an interesting red & white (rattle can) livery and all manner of boy racer 'JDM' stickers in the rear window. This project is a bit behind but the engine is sorted at least. Doing much the same to this car, driveline off and the rear end is awaiting blasting & painting with epoxy mastic, all new bearings and a Torsen. Currently sits on the 'T3 DIY' coilovers it came with but will likely fit BCs. Engine is a 13B 6 port, with a Weber-style intake manifold and Jenvey 50IDA throttle body. Engine was built with Turbo 2 exhaust inserts and a shimmed oil pressure regulator. Again an RX8 style trigger wheel has been added, and a 12a front cover used to allow mounting with the FB subframe. The FB OMP has been modified to take 2-stroke oil from a tank in the engine bay and I am currently working on a linkage to allow it to operate via a cable from the throttle body. This car is due to be sprayed in V4 Canal Blue Metallic (a 626 colour used on the Japan-only IMSA Special). Admittedly the livery did grow on me (the stickers didn't and have all been removed) but I am very much convinced by the respray.

Unfortunately I've not looked at both projects in about a year as I have moved from Wiltshire to Northern Ireland, and I am due to move again within Northern Ireland in about 3 months' time. Currently gathering parts and scheming to allow me to get both over the line once I am settled again (with a nice big barn to work in )

I will get a project thread on the go eventually with lots of pretty pictures.

Cheers all

[Hobbawobba]

They sound like a couple of interesting projects there aye! Have you got any pics? Keen to see

[Cadfael]

Sure. Since neither car is complete yet I will save the most recent photos for when they are both back from being painted and have been shipped across the sea to me. In the meantime, I have a couple of "before" pictures.

B939AHB - This is before the most recent respray, see how the paint has flaked off on the driver's door. Was originally opal green but sprayed red by a previous owner. Maroon interior. I bought it pretty much bone stock, as far as I can tell, save for the Elford Turbo bits, and some 16" white Crimson Racing Sparco wheels. I put these 15" SSRs on it when it arrived but I won't keep them on the car.



C999EWN - This is exactly the condition I received the car in. Definitely unique . Before the rattle can livery it was originally opal green, same as the Elford, engine bay has been pained black with gold flake which I thought was interesting. It has the brown interior. Wheels are 14x8J Impul Hoshino Racing G5s which, given their condition and the presence of the centre caps, and based on this (https://www.jdmdistro.com/shop/wheels/j ... cing-g5-5/) being the only listing I can find for these wheels, are worth about as much as I gave for the whole car. Probably won't keep them in the long run. Car has T3-style 'DIY' coilovers in the front and cut springs in the rear.



Hopefully at least one of these will be back on the road by the end of 2024, I have both engines already built with all fresh bearings, seals and lapped housings, so shouldn't be too much stopping me from getting them done. I have just bought an old house though, so will be diverting all funds and attention to that for the foreseeable future, but God willing should be turning spanners again by the end of summer!

[gt_james]

welcome! some cool projects there

Keen to see how you do an uprated front anti roll bar. I currently have a stock one on my race car and am planning to upgrade it. The RB front anti roll bar is quite heavy and expensive for what it is.

Watch the rear upper links with rod ends, that is not a good idea, the short upper links bind in roll, and without rubber bushes, this is normally a much worse problem. Most people do their best to soften the bushes on the upper arms, drilling holes in the rubber bushes and using nyloc nuts to allow the bush to pivot on the bolt rather than clamp the inner bush which the rubber is bonded to. The proper fix is to change the mounting locations.

For your oil pressure mods, what exactly have you done?

there are two oil pressure relief valves. The main oil pressure regulator is on the rear iron and sits in the sump, factory they're set to 70psi. The early RX8 is 80psi (good street upgrade is to switch to this reg) and the FD is 110psi. You can crush or disassemble and shim the rear regulator to increase the pressure setting, but don't go too much with it. Or change to the RX8 one (easier).

There's one in the front cover, which is an emergency pressure relief valve, essentially there in case there is a blockage in the oil cooler or lines, before the rear iron pressure regulator, and its there to stop an external leak or the front cover O ring getting pushed out. In S4 and earlier cars, they're set at 115psi, and the later cars had the front O ring area on the front cover re designed, and this emergency relief valve was set to 155psi.

The front cover O rings do fail, (as do the front and rear main seals) at high pressure, so you do not want to shim the front emergency relief valve. if the front o ring fails, you will have low or no oil pressure and will damage the bearings in your engine.

The only reason you should shim the front relief valve is if you fit a 12a front cover to a later series engine with the revised front cover O ring, or if you have modified it to work at higher pressure (like a machined spacer and using an RX8 metal front cover gasket.

despite this, I have seen quite a few people on forums and facebook etc recommending shimming the front relief valve.

I think any more than 80psi oil pressure is excessive, and will just increase the likelihood of front cover O ring or main seal issues, and more wear on the oil pump.

Final thing, the 12a came with 15mm and 17mm oil pumps, if you're rebuilding, use the 17mm pump.

[Cadfael]

Cheers, really appreciate the comments - responses below. Will post ideas and findings w.r.t. anti-roll bar options, will be a while before I get round to looking at it though.

Watch the rear upper links with rod ends, that is not a good idea, the short upper links bind in roll, and without rubber bushes, this is normally a much worse problem. Most people do their best to soften the bushes on the upper arms, drilling holes in the rubber bushes and using nyloc nuts to allow the bush to pivot on the bolt rather than clamp the inner bush which the rubber is bonded to. The proper fix is to change the mounting locations.

Aye I had heard, I've got all new rubber bushings in the watts linkage and lower forward links, well greased and fitted with nyloc nuts nipped up just enough to allow the arms to pivot. Tempted to drill the nuts through for a split pin, too. As I understood it, the main cause for the binding is the fact that the upper links are not parallel with the lowers, exacerbated by the different lengths. The heim joint uppers use tabs welded on to the outside of the stock attachment point on the car's body to make the upper links parallel whilst keeping them in double shear. When I was looking at the forums a couple of years back, seeing the complaints about the FB's rear suspension geometry immediately made me run to parallel links as the answer. Once I've got the cars back, I might jack them both up and test the rear axle's limits of articulation without forcing them, to see if the heim joints have made it better or worse.

For your oil pressure mods, what exactly have you done?

there are two oil pressure relief valves. The main oil pressure regulator is on the rear iron and sits in the sump, factory they're set to 70psi. The early RX8 is 80psi (good street upgrade is to switch to this reg) and the FD is 110psi. You can crush or disassemble and shim the rear regulator to increase the pressure setting, but don't go too much with it. Or change to the RX8 one (easier).

There's one in the front cover, which is an emergency pressure relief valve, essentially there in case there is a blockage in the oil cooler or lines, before the rear iron pressure regulator, and its there to stop an external leak or the front cover O ring getting pushed out. In S4 and earlier cars, they're set at 115psi, and the later cars had the front O ring area on the front cover re designed, and this emergency relief valve was set to 155psi.

The front cover O rings do fail, (as do the front and rear main seals) at high pressure, so you do not want to shim the front emergency relief valve. if the front o ring fails, you will have low or no oil pressure and will damage the bearings in your engine.

The only reason you should shim the front relief valve is if you fit a 12a front cover to a later series engine with the revised front cover O ring, or if you have modified it to work at higher pressure (like a machined spacer and using an RX8 metal front cover gasket.

despite this, I have seen quite a few people on forums and facebook etc recommending shimming the front relief valve.

I think any more than 80psi oil pressure is excessive, and will just increase the likelihood of front cover O ring or main seal issues, and more wear on the oil pump.

Final thing, the 12a came with 15mm and 17mm oil pumps, if you're rebuilding, use the 17mm pump.

Thanks - good info here, I believe I have the 17mm pump as I have a faint memory of putting the verniers to it in order to see if I have the "larger" one, and I faintly recall that I did. I disassembled and shimmed the rear regulators with washers as below, trying to target 80-90psi:



I have not touched the bypass valve. I wasn't aware of any further modifications needed to keep the front cover O ring sealing at higher pressures - I believe I used the normal O ring and sealed the mating faces with sealant as opposed to a paper gasket. Reckon I'll run into trouble?

[gt_james]

As I understood it, the main cause for the binding is the fact that the upper links are not parallel with the lowers, exacerbated by the different lengths. The heim joint uppers use tabs welded on to the outside of the stock attachment point on the car's body to make the upper links parallel whilst keeping them in double shear. When I was looking at the forums a couple of years back, seeing the complaints about the FB's rear suspension geometry immediately made me run to parallel links as the answer. Once I've got the cars back, I might jack them both up and test the rear axle's limits of articulation without forcing them, to see if the heim joints have made it better or worse.

The binding is mainly caused from the difference in length and how wide set the upper arms are. The fact that they point inwards somewhat helps reduce the bind, but by moving the upper arms outwards at the body end and fitting heim joints will make the binding problem worse. Ron sutton has published some good guides about how to set up a solid/live axle with 3 and 4 trailing links. Also read Jim Susko's book on getting the RX-7 FB to handle.

For a 4 link car, you want the lower links wide set in the car, the wider the more control there is over the axle. The top links can be on top of the lower links, or wider or narrower, but the wider the top links are set, the more issues with bind you have. The narrower the top links, the more articulation / less bind you have in roll. The best set up is a 3 link, much more articulation before things bind. That's why you see 3 links so much in handling cars, and 4 links in drag cars. 4 links are stronger for hard launches, 3 links bind less. The trouble with a 3 link is packaging.

I don't mean to come across as harsh, hopefully you like how your car drives, but unfortunately you have set up your rear end to bind not move, you need to narrow the top links not widen them, and give them very soft bushings, not heim joints. If I've understood you also have stuck with rubber bushes in the lower links also. This all seems like the opposite of what needs to be done, and the opposite of how people have been setting these cars up for the street, AutoX, racing in SCCA and elsewhere for decades, but seems to be how T3 sells their parts. Also mounting the upper link in the wheel arch reduces clearance to run a wide tyre on the rear.

I don't recommend Heim joints/rod ends on a street car, but if you have a track car and want rod ends, you should fit rod ends everywhere except the upper links, which should be soft rubber bushes. It's a good idea to do split pins but nylocs or two nuts locked together should be fine to run the upper link inner bush loose, or use a poly bush like energy suspension, which isn't a bonded bush and works better from this point of view, but I would prefer softer for the upper arms.

The watts linkage could use rod ends over rubber bushes even on a street car as the watts (or panhard) doesn't transmit load through the suspension in steady state road driving like the trailing links, so wouldn't be making noise and harshness as much as rod ends in the trailing links. I had rubber bushes in the lower arms and rod ends on my panhard bar at first, and it was reasonably quiet for the road, and it was a much more noticeable increase in noise and harshness when I fitted rod ends to the lower arms compared to having rod ends on just the panhard. There is a watts linkage brace available from mazdatrix to put the studs in double shear too.

The stock watts linkage is fine on a road car, but I personally don't like it that much, and by the time you've made arms adjustable and rod ends, and fitted a brace, you may as well put the effort into ditching it for a panhard. The stock watts link is a lesson in how to screw up a watts link as much as possible. The advantage of a watts linkage is better lateral location of the axle, compared with a panhard rod, but in a factory set up with rubber bushes, the better location is not worth it as you don't have accurate lateral location with the flex in the rubber bushes, so all mazda did was add weight, complexity and cost over a panhard. Then to make it worse, they put the pivot point on the axle not the body, making the roll centre migration and sprung weight worse, they mounted it high on the axle, giving a high rear roll centre, which gives oversteer, and for those of us that lower these cars, the rear roll centre doesn't get lower as you lower the car, but the front end gets drastically lower, so a lowered car has a steeply inclined roll axis, giving much worse oversteer (panhard and roll centre correctors are needed). Then they offset the pivot point to the right (they had to as the watts is ahead of the axle not behind) which means the rear roll centre is not in the centre of the car, giving asymetric handling as the car rolls, which is the only advantage a watts linkage has over a panhard, so the mazda watts link has no advantage over a panhard, but a lot of drawbacks. Panhard rod is light, simple to fabricate, easy to adjust and easy to get a low roll centre. The neighsayers that think a watts is better, its been proven in tests with professional drivers in well set up cars that most drivers cannot tell which way round the panhard is laid out, so the small asymetric difference in roll on left and right corners is not as big of a deal as people like to think, and is a much better compromise than most watts linkages.

When you've realised the t3 set up doesn't articulate, the best way to fix this is to do a 3 link. The 3 link is fairly straight forward to install, not much fabrication at all. Unfortunately G force engineering who used to sell kits is long gone, but I believe KC raceware still makes similar kits. They wouldn't be that hard to replicate if you could do some fabrication. They also sell a proper Panhard bar (not like T3 which is awful), the panhard is a bit more effort to install but still not much at all.

If you don't want to go to a 3 link and panhard bar, and want to try and fix the 4 link, then you wont be able to run the car as low, and you'll need to cut off the upper arm mounts from the axle, and re make the brackets, moving them inboard, and mounting the arm as far back behind the axle as you can to make the upper links as close in length as you can to the lower links. It'll still bind but a bit less than the wide set upper links you have now.

Take a look at my build thread I have a 3 link and panhard on my race car.

[gt_james]

Thanks - good info here, I believe I have the 17mm pump as I have a faint memory of putting the verniers to it in order to see if I have the "larger" one, and I faintly recall that I did. I disassembled and shimmed the rear regulators with washers as below, trying to target 80-90psi:



I have not touched the bypass valve. I wasn't aware of any further modifications needed to keep the front cover O ring sealing at higher pressures - I believe I used the normal O ring and sealed the mating faces with sealant as opposed to a paper gasket. Reckon I'll run into trouble?

Thats good you have the 17mm pump, a lot do, I think '83 might have been the changover year but not sure, and a lot of earlier small pump cars have had them changed by now.

80-90psi is fine, I would prefer 80 myself to 90! not touching the front cover bypass valve is a good thing. It's only when people try to go to 100psi or more that things cause trouble. You shouldn't need any further modifications, leaving the paper gasket out is good, as it means the O ring has a bit more squish to keep it in place, with the paper gasket, the O ring is compressed less, so that was a good thing to do.

I was concerned that you might have shimmed the front emergency valve and shimmed up to 100psi or more at the rear reg, and at that point your front cover O ring would be a risk. As you have it, I think it should be fine.