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Actually this build thread is more like a small restauration thread but I didn't know where else I should put this.
I didn't post for a longer time because my old FC became a little bit too hot for my taste.
3 months ago I found a very interesting replacement for my old RX7:
The only ever registered draw through turbo SA in Germany!
It is a 1980 SA22C which was originally owned by a german Mazda dealer. That dealer first installed facelift bumpers and the facelift rear end and exhibited it at the IAA in 1981. After that the car was more or less useless for him but he was a hobby race driver so he decided to take the mazda and make a street rallye car out of it.
He sent it away to a company speciallized in building turbo engines in 1982 which was called "Kahn Turbosysteme" and that company ordered a BAE draw through turbo kit from the USA and installed it together with their own water methanol injection system. The turbo is a Rayjay which is comparable to a T04B and the used carburetor is a Carter AFB.
When they tried to adjust the system the car was pulling that strong that the rear wheels couldn't withstand the high speed and exploded at about 140mph on the dyno and that's the reason why in my registration papers there is a note saying that driving faster than 135mph is prohibited.
That company also rebuilt the drivetrain. They installed a spur-toothed (hope that's the name in english) transmission and a clutch type LSD (round about 50% locked).
Whend the car came back from that company the owner sent it away again to a company called Wiechers and they put in a roll cage.
The Mazda dealer then installed a kill switch, some fancy ATI corsa steering wheel and Interad bucket seats. They also installed Koni shocks and a body kit pieced together of a small rear spoiler lip and a rear bumper made by KüWe and a front bumper and side sills made by Versatec.
Somehow a Blaupunkt radio and a Panasonic equalizer also found their way into the car and there's even a flexible lamp to read the road book or maps for the passenger hidden behind the roof bar of the roll cage.
The car didn't see many races because the owner became ill. So it sat in a garage for about 30 years and was only driven to the inspection every 2 years. There are only about 28000 miles on the clock!
I found the car on Ebay and just had to buy it. I payed about 5500$ for it which was more or less stolen. When I picked it up with my trailer it was running like crap because all the seals of the carburetor and the accelerator pump were broken. because of the pump the car was really hard to start and had bad hesitations when I tried to accelerate. The next problem was that it had detonations at above 5 psi. I nearly peed myself when i heard the first detonation because as you maybe know detonations and apex seals don't match very well.
When I arrived back home I started ordering a carburetor rebuild kit and some other stuff and got to work on the car. I know quite a bit about fuel injection but I never ever touched a carb before but after some rounds of the game known as "learning by doing" the Carter AFB was back together and the car started imediately. I later found out that the linkage for the secondary throttle plates was bent so i never had full power but that's an other story...
In the process of removing and installing the carburetor I also found an other reason for the detonations. The water methanol injection wasn't working at all. Normally it would be absolutely reliable but 30 years old water wasn't that good for the pump (which by the way is a Mercedes window washer pump out of a W114) and the valve which I don't even know where that came from. I got a new washer pump (Mercedes can get you every part they ever built) and removed all the gunk from the electric valve and the car was good to go on a test drive.
By the way there's also a second electric valve of the same type. It is used as an additional injector for gasoline which is injected directly into the pipe between the carburetor and the turbo inlet if the simple electronic detects more than 7psi and 5500rpm. If the engine is running below 5500rpm but with 7psi+ only the water methanol mixture is injected. Crazy stuff...
After my repairs and a much needed oil and plug change I took the car for a test drive and I was amazed how hard that old car was pulling. Later a friend with his Honda S2000 joined and we tried out which car would be faster on the Autobahn. I pulled away with my RX7 easily.
Later this summer I drove to the biggest german car meet only for japanese cars with my RX7 just for fun. I didn't even want to participate in the whole trophy stuff there but the organisators convinced me to do it. End of the story is this:
The left one means oldest car at the event and the right one means my car earned the third place out of about 50 Mazdas. I wasn't even able to fix anything on the outside of the car which means it wasn't exactly in a perfect shape.
I also got the chance to get the car on a dyno there. (I didn't know the secondary throttle plates didn't open at that time) The RX7 had an amazing 206bhp with completely closed secondary plates. One week later I fixed the throttle linkage and now it has 265bhp at 12psi.
There's still much to do on the car. Next month a friend of mine will build a new exhaust for the car because it's heavily rusted and this winter I'm going to fix the outside of the car which means some new paint and some rust repair at the door drains (by the way that's the only place where the car has rust). The engine bay will get some love, too in the next few weeks.
Thanks. There's just one thing which worries me at the moment: I've been driving the car for about 1000km (about 650 miles) now and it's running great buuuut I'm not missing something I should... What I mean is engine oil!
The car got an oil change just before I bought it and since then the oil level is at the same mark. I checked the oil metering pump but it's working. I can see oil dripping into the carb from the two nozles. When I got the car the crank case ventilation system was not working at all because somebody built it wrong but I fixed that problem before I took it for the first drive. I built it so that the ventilation system only sees vacuum and the connector at the oil filler is open to the atmosphere (with a small filter of course).
So what the hell is going on with the oil? I can only imagine it's because the car is a bit difficult to start and blows a huge amount of unburned fuel out of the exhaust (no it's not water! Better don't play with cigarette lighters behind the car when I'm starting the engine). That's because of the draw through setup which means long ways for the air fuel mixture and very much fuel condensation. Could it be that some amount of that fuel is pressed into the crank case?
More than likely the oil level is rising from fuel dilution. Being that the engine was not originally designed for a turbo, the side seals are not effective under boost.
Even the FD has this issue when the boost is higher than stock levels.
I would however add some 2 cycle to the fuel as premix for some safety margin.
My RX7 is getting better and better... and worse and hopefully better again in the next few days... I've got a small problem on which I need some advice. A friend of mine welded a new stainless exhaust for me because the old one was out of steel and rusting a bit too much for my taste. While putting the new exhaust together we found out that the old one wasn't really thought through. It started being 3" at the turbo, then was reduced to 2.25" and the silencer only was 2". So it went from bigger than the turbo outlet to extremely small. We used 2.5" stainless steel piping and a new 2.5" silencer at the end. Sounds good and I'm sure it would drive even better buuuuut because of the huge amount of back pressure of the old exhaust system the jets in my carb are a bit too small with the new system. The exhaust gas temperature is about 50-100°F hotter in all situations than it was before and I get detonations if i accelerate hard under full boost (only tried it once because of the extreme risk of shooting engine parts through the turbo).
I guess the engine isn't missing that much fuel because the egt isn't that much higher but it seems like that small amount makes the difference. The problem now is that I never had to adjust a carburetor before. I'm used to work with megasquirt and other ecu based injection systems but not to carburetors. I allready ordered new jets for all 4 jets and decided to take the 2 next bigger sizes but I'm wondering what the best method would be to test what i really need? should I start with changing just the 2 main jets first or should i change all 4 jets to the next bigger size and see what happens?
I'll post some pictures of the exhaust as soon as I get them. Smart phone died.
By the way there's something which worries me a bit. My differential is a bit special. I've got a bill here saying it's a limited slip differential. My problem is I don't know which type it could be.because it behaves very strange. On the car lift i can spin both rear wheels as if it was an open one but as soon as i drive the car and accelerate in corners it locks up with a loud "clank". Judging by the price of it it must have been some fancy racing stuff because it was worth abou 1/4 of the price of the new RX7 but I'm a bit worried it might have a problem because of the hard locking it does. I never have seen or driven such a differential before. On the other side I don't want to open the case without any information just to see that everything is working and it has to lock like this.
I finally got some photos of my new exhaust system. I also changed the secondary jets inside the carburetor to the nex bigger size. Now it's running much better. The newly installed AFR gauge says so, too. It's really not easy to find a gauge with a pointer instead of the digital ones. The VDO tank level gauge shows how much water-ethanol mixture I have left by the way. I thought it could be useful.
Two doritos on a stick, an added hairdryer and a water pistol filled with some additional booze for the party can make it happen.
There's only one problem which I need to fix now: I need more pressure at the rear brakes. The car got a rear axle from who knows where in 1981. RX7s with limited slip differential and disk brakes with a 4x110mm bolt pattern didn't even exist back in 81, did they?
It seems like nobody thought about brake balance when the car was built because when I step on the brake pedal hard the rear is becoming dangerously light. That can be fun if you know what you're doing but it's still dangerous and I don't want to let my car end up on a scrap yard in the near future or myself to end up in the hospital because I didn't manage to control an unwanted drift.
I know I can change the brake balance in one of my other cars which is a Miata by shimming the proportioning valve but would that work in my RX, too? I really don't want to break the valve because in Germany I guess parts are much harder to find than in the USA mainly because only about 70 1st gen RX7s exist in Germany and none of them will end at a scrap yard in the near future and the last three Mazda dealers here weren't even able to look up parts for the car because of a missing online parts catalog.
Two doritos on a stick, an added hairdryer and a water pistol filled with some additional booze for the party can make it happen.
There's only one problem which I need to fix now: I need more pressure at the rear brakes. The car got a rear axle from who knows where in 1981. RX7s with limited slip differential and disk brakes with a 4x110mm bolt pattern didn't even exist back in 81, did they?
It seems like nobody thought about brake balance when the car was built because when I step on the brake pedal hard the rear is becoming dangerously light. That can be fun if you know what you're doing but it's still dangerous and I don't want to let my car end up on a scrap yard in the near future or myself to end up in the hospital because I didn't manage to control an unwanted drift.
I know I can change the brake balance in one of my other cars which is a Miata by shimming the proportioning valve but would that work in my RX, too? I really don't want to break the valve because in Germany I guess parts are much harder to find than in the USA mainly because only about 70 1st gen RX7s exist in Germany and none of them will end at a scrap yard in the near future and the last three Mazda dealers here weren't even able to look up parts for the car because of a missing online parts catalog.
You forgot your neighbors (Belgium and The Netherlands). The face lift with disk brakes is from "82. They say that the master brake cil. is bigger when the rear is disk brakes.
The book of '79 till '85 says that the rear has a proportion bypass valve.
Has any one done this I'm new here I need to now jet etude sizes ect I'm a engineer so I will make manifold ect myself I'm just after info from people that have done this did you still run a dizzy what timing were you running ect
This thread has a ridiculous amount of views, do you have this posted somewhere else as a link? Just curious, the exposure of this tiny thread is ridiculously huge in comparison.
Looks awesome though man, keep the updates coming!
Hey there my name is Tony. I own a 1997 FD and I'm looking for where all the rx7's hangout here in Greater Van. Id like to make more friends with rotaries so I can learn more about them and maintaining them. You can text or call me at my number 204-430-7010
Don't forget Gordon, shortening your intake runners a couple inches will move the torque peak higher in the rpm band. Seems you have some lea way with your upper runners for even more experimentation since they're straight. Calling this project DONE is unacceptable. 😂😂😂
08-20-15, 12:33 PM
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I wasn't even able to fix anything on the outside of the car which means it wasn't exactly in a perfect shape.
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It's really not easy to find a gauge with a pointer instead of the digital ones.
The Turbo