Drive Train


On December 16, 2002, I received my 20B from You can see some pictures of it in the Media section. Dave Gibson told me is was in great shape, but it has to be seen to be believed. It was delivered to my work place, so I was dragging everyone out of their offices to come see it. People kept asking me if it was a rebuild.

I know in a couple of the pictures I comment on broken things. I'm not really upset about that at all. I don't think they were broken when Dave shipped it, and I do believe they were broken in transit. I did sign the bill of landing without looking closely at the engine. I e-mailed Dave asking if anything could be done. He said that once I signed for it, it is mine. Then I thought about it. If I had refused to sign for it, because of the damage, the shipping company would have probably just taken the engine back, and I'd have no 20B. So, as I said, I'm not upset at all, just pointing out things I need to fix. Those two really won't be bad either, just remove the thermo wax, and replumb the blow off valves back into the intake. Looking closer I may not even need that "T" that is cracked. I don't know where the third leg of the "T" went, I'm thinking maybe the vacuum booster for the brakes. That will be on the other side of my engine bay, so there is no point to have that hose there.

I've not had much chance to do anything to the engine yet. I'm going to go over this weekend. Pull out the stock wiring harness, and go over the vacuum lines, to see what I do and don't need. Also review the solenoids, I think I'll be able to pull all of them too. I haven't looked closely yet, but I think that'll involve removing the upper intake manifold, like on the 13B. I may wait for that for a bit, until I get the new injectors, so I can do them while it is apart. Generally I'm just going to go over things to try to simplify the wiring and vacuum layout of the engine.

I'll redo any gaskets with new material, replace the smaller vacuum lines with silicon hose. I want to also replace any lines that carry pressurized fluids (fuel, oil, coolant) with braided stainless lines. So I need to buy some supplies.

Next up, I need to get a Turbo II transmission. Even before I get a clutch or anything. I need this to find where to weld the mounting plates. So first thing in the new year, I'll be trying to track one down. I'll more than likely have it rebuilt so it doesn't matter what condition it starts in, as long as it isn't totally ruined.


I had a good look at the blow off valve plumbing today. The first leg of the "T" comes from one blow off valve, the second the other blow off valve. The "T" combines these together. The last leg goes to the hose that I wasn't sure where it connected. I found a hole suspiciously the same size as the connector in the end of the hose in the AFM funnel. So it was originally plumbed back in there. Which is the typical RX-7 blow off routing. Unfortunately the AFM funnel is mashed beyond all recognition. But I really wasn't planning on using that anyway. I'm going to be using a MAP sensor, instead of an AFM. I'm sure these blow off valves can't be open air vented, as they'll probably leak under vacuum. So it is either find a one way check valve for them, or see if I can find an after market BOV that can mount on the stock flange, or have new flanges attached to the ducting.

Didn't get much time to do anything else with the engine today. Just untangled the wiring that was wrapped about the engine. There are a lot of wires.

An amendment, I just pulled one of the stock BOVs from the engine. I can't make it leak no matter how I suck or blow on it. I know the vacuum of the 20B is way more than I can pull, but this is a good sign. Oh and after I removed the hoses and connectors, I found the "T" was more of a "Y".


I got a lot of stuff accomplished today. Removed the engine wiring harness and the vacuum spider.

The stock wiring harness was cut at the firewall when the engine was removed from the original car. That didn't matter as I was always planning on building a custom wiring harness. But I had to get the stock harness off the engine at some point. I figured sooner was better than later, as it would be a easy job to do.

While no part of removing the harness was hard, there was just a lot of stuff in the way. After I pulled the upper intake manifold, I knew it was good that I was starting early in the day. I wish I had photographed the process, but it wasn't pretty. I basically just pulled anything that was in the way.

The brings up the second point. The 20B has nine solenoids each with at least two vacuum hoses, half with three. That makes for a lot of hoses. They are all connected together with a metal line spider that routes most of them down off the port side of the engine (note that the port side if the engine is actually starboard). I just pulled them all off. I hope I'm not in for too big of a surprise when I pull the heat shields off the turbos and have a look at the control system. I think a lot of them are for emissions like on the 13B. But I know a few are for the twin turbo, waste gate, butterfly between the compressor outputs, and who knows what else.

One thing that is nice on the 20B is that the vacuum spider is separate from the fuel spider. On the 13B they are all welded together. So I was able to remove the metal vacuum lines, and leave the fuel stuff alone.

I've started to modify the throttle body. I have it at my apartment now. I'm going to need some PB Blaster to get the screws loose on the secondary throttle plates. The screws are very soft and very stuck. If they won't budge, I'll just drill them out. The thermo wax was easy to removed, just three screws. I can reroute the line that was going into the cracked nipple to where the line out of the throttle body was going, which then runs along the fuel spider to enter the rear end housing. Opposite the thermo wax was a vacuum pod that could close the secondary plates slightly. I image it was close the throttle slightly between shifts of the automatic transmission, like on my 13B. That's gone too. I think I'll keep the dash pot, it keeps the throttle plates from snapping shut, isn't really in the way of anything, and seems to work properly. The dash pot is also easy to get to even when the engine is assembled, so it if does give me trouble in the future I can still remove it.

All in all, a very productive day. I banged up my hands a lot, they just aren't used to this kind of work, I should look into some of those mechanic gloves. Tomorrow I'll have a look behind the heat shields.


Didn't do as much today as yesterday. I pulled the outer heat shields off the turbo assembly to aid in the chasing of lines. No vacuum lines under the heat shields, that is probably a good idea. The only lines running back there are oil and coolant. There are two vacuum/pressure actuators located towards the front of the block with rods that run back to the turbos. I imagine the open and close butter flies to control which turbo is seeing the exhaust. I was right about the butterfly on the output side of the compressors. Again the system doesn't look that hard to control. But I'm not liking it. When Mazda designed the twin turbo setup, it was probably the best way to get boost all the way through the RPM range. The small turbo to spool up quickly to avoid lag, and the bigger turbo to take over when the little guy runs out of steam. I don't think that is needed these days with the ceramic ball bearing turbos, and the other various advancements. One can get a turbo that can spool quickly and boost high. So Mazda's system is a complicated overkill.

If I'm going to get rid of the twins, what should I replace them with. Ted mentions on his 20B FC conversion page, the T72. I've looked at the compressor map, the area of max efficiency is a little small, but from my rough calculations the 20B seems to fall right in it. But the T76 also looks good. The surge limit is pushed a bit farther right, but I'm pretty sure even a stock ported 20B can swallow enough air to stay on the right side of the line. I'll have to ask Ted why he mentioned the T72 instead of the T76. I have a feeling it is due to price, the T76 is quite a bit more. I'll also call Turbonetics and see what they recommend, if they have dealt with 20Bs before.

Basically I'm looking for a turbo that spools quickly, but won't be over spun by the time I reach the red line. Also it must not surge with the stock ports, but still be suited to a large street port that I'll have done if I ever get the engine rebuilt. Should be simple, huh?

I really should put this in the Car Log section, but it isn't working yet, so I'll just mention it here. I went to my mom's today, mostly to get my PB Blaster, but also ate dinner and put together a bicycle for my niece. I couldn't find my can of PB Blaster. It turns out my youngest brother cleaned up the basement, and threw out my Blaster along with my Zymol cleaning products. That kind of pissed me off, that was about $50 worth of stuff. I complained to my mom about it, she said she'd get me a new can of PB, since I needed it right now. She also saw the cuts and scrapes all over my hands. Actually I was trying to get out of having to put powered sugar on some cookies and asked if I should be doing it with open wounds. But anyway, my boo-boos got me a pair of Mechanix Gloves. They fit pretty well, and I think after just a little breaking in, I should be able to work in them without hindrance. I guess I can go work on NASCAR now.


Finally got the secondary throttle plates removed from the throttle body. I didn't resort to drilling them out, just took the TB to work, and had one of the guys there give it a shot. He's been gloating that he got them loose and I couldn't, but I think it was just that the PB Blaster had an extra few hours to soak in over the night. The screws aren't pretty now, but they are out, and I don't need them anymore anyway. Also had a bit of trouble getting the TPS removed, to take the thermo wax cam off. One of the screws is a little buggered, but not horribly, and everything is back together that is needed. Just need to plug the two holes in where the rod that the plates were in were. The throttle body looks good now. I'll probably get some degreaser and clean the back side of it up a little bit for what ever reason.

Got a little more info from Ted about the turbos. He said that the T72 is good, and the T76 will also work. The T72 is smaller so obviously will spool quicker. The T76 is better suited to a ported 20B. Since I will be getting it ported if I ever have it rebuilt, and I don't want to have to swap turbos at that point, I'm really considering the T76 at this point.

Just noticed this minute, the buggered screw from the TPS is the same as ones I have removed from the thermo wax, so I can replace it is a good looking one.

Just need to get the turbos off now.


Took the OMP off today. Geez those bolts were hard to get to with the turbos in place. I took off the waste gate actuators, that gave me enough room to stick a long extension down behind the OMP to get the two hidden bolts. Ironically enough, after getting those pods and hoses out of the way, the hardest bolt to remove was the visible one in the front. Not that hard, just positioned a little awkwardly. Anyway, it is off.

Found the OMP is the same as the one from the 13Bs. I theorize that it may pump a little more oil than the 13B one. One the 13B there are four lines, they run to two oil injectors on each rotor. The OMP on the 20B has one of the holes that the lines connect to blocked off. So there are only three lines, one on each rotor. In order to provide the same amount of lubrication as the two per rotor, one would think that this pump has to meter out twice as much oil. The world may never know.

I asked about block off plates for the OMP on the mailing lists. People told me to just make my own. I'd only need a piece of aluminium, a jigsaw, and a drill press. Well I don't have a jigsaw or a drill press, I could get the aluminium. I was told I could make it as nice looking as I wanted. Well K2RD has all sorts of block off plates pre made for $10 (plus $5 shipping). I think it is worth it. They are very nice looking, way better than I could do. Laser cut 304 stainless. I'll make the gasket.


Yesterday I sent my throttle body out to BDC for him to remove some metal from it. After the secondary throttle plates are removed, the metal that makes up the bore between the two sets of plates is not needed, and is probably more of a restriction than anything. I had recalled that someone had done the work to carve out the inside of a TB before, I was thinking that it was BDC. So I asked on the list, and sure enough it was him, and he would do the work for others. So I shipped out my TB and a check yesterday. I figure just having BDC touch the TB should be worth a couple horse power.


Not much has changed with the engine in the last few days. K2RD shipped my block off plate, and BDC has shipped my TB back, but neither has arrived yet.

I think I have made some decisions on the turbo and transmission. I think I will go with the smaller of the two turbos I was considering, the Turbonetics T72. This is because I found the manufacture number of my engine, A182, so it is an earlier build. The later engines added some extra dowels to hold things together better and could handle much more power. But I figure 550 or so horse power will be more than enough to get me in trouble. This also leads to the transmission. Since I won't be making 700 ft./lbs. of torque I should be able to get away with the stock T2 transmission. I've been e-mailing Rob of Pineapple Racing. He tells me there is a cryo process that adds a bit of extra strength to the gear teeth, and keeps them from being torn off.

Next on my list was the transmission, so I think I'll try to source a rebuildable core now, and have it shipped off to Rob to work his magic. Dave Gibson, who I got the 20B from has some J-spec transmissions in stock. I'll just have to find out if they are from a Series 5 car.


Got my TB and OMP plate. The TB is sitting in my living room, just cause it looks so nice. Need to polish the outside of it also. I installed the OMP plate, it looks like it belongs there save for the black alan bolts. Sure K2RD's stuff is a little expencive sometimes (not in this case can't beat $10), but it sure looks nice.

I've not been doing much car stuff the last week. I'm out of money for two months. I've got to pay off a loan, but that'll free up $500 a month after that, so it is for the best.


Not having money doesn't really mean not working on the car. During breaks through out the day, I've managed to remove the turbos from the exhaust manifold. Now all that is left to do is to remove the rest of the heat shield from the manifold and unbolt the manifold from the engine. I might do that tomorrow during breaks.


I'm going to have to spend some money now. I started to unbolt the turbo manifold from the engine today. I soaked down each nut with BP Blaster yesterday. During a short "smoke break" at work, I went down and cracked each of the six nuts loose. Then during my lunch break I went to actually remove them. As I start working the first one out, I noticed that the nut wasn't moving, but the stud was coming out instead. I figured that wouldn't be such a big deal. I worked the first one, but it became hard to turn at one point, so I moved on to the second. This one the same thing, the nut was frozen solid to the stud, which started backing itself out of the block. So I just let to come, that one came out all the way. One other came out easily, the other four started to stick about half way out, no nuts came loose. I eventually worked the fourth one out. The last two just jammed real solid. One felt like it started to turn again, but before I could do anything about it, I felt the dreaded release as the stud twisted off behind the nut. The last one just broke off with a sharp snap about 5 mm from the block.

I was pointed to Time-Sert. They seem to have some high quality thread repair inserts. The only problem is you have to buy a whole kit. While I need everything to do the job, the kits only come with five inserts. While two of the studs seemed to have come out cleanly, they did gall on the outer most threads. They should probably be redone too. But that totals six, so I'd have to buy two kits.


As I was saying, I'm not doing much work on the engine right now, as I'm very short on cash. I did manage to get some stud removers and a tap wrench though.

The stud removers are pretty neat. They have these spiral teeth that cut into and grab a rounded nut, bolt, or stud. I placed one on the longer of the two studs left in my block and started to turn it. I saw it was going to be very hard to get back off once the stud came out, so I took it off and had a look at the shorter one. Unfortunitly it was broken off too close for the tool to grab. So it was back to the longer one. After about one full turn of the tool the stud was held tight. I put the breaker bar on the stud remover and started to pull. I got about 90 degrees of rotation from the handle of the bar, but the stud didn't seem to turn at the block. I set the bar back up to the veritcal position and turned another 90 degrees. At the bottom of this turn the stud snapped. This one sheared off even closer to the block than the former short one. I guess it is time to start drilling. I think I'll see about getting this block to a machine shop because I don't trust myself to drill straight enough into the block. The aluminum housing is going to be much softer than the stud, and thus easier for things to go wrong.


Yes, it has been a while since I did any updating. Been paying bills and saving what I can for the car. The stud removing/new hole tapping exercises didn't go all that well. I've been thinking all along I should get the engine rebuilt, and go with the newest rotor housing from Mazda, with the larger exhaust ports. So I'm about to order three of them.

I also talked to BDC, he said he enjoys traveling to an engine to rebuild it, rather then sending the engine to him. There are really only a handfull of people who I would have rebuild an engine for me. BDC would have been on that short list, so this will work out well. My main problem was, if I were to ship the engine to Texas and back it would cost me over $1000. I can ship a person from Texas and back for under $200.


Wow, this has been a very long time now. Still not much done with the engine. But I will be getting an S5 Turbo II parts car. It is lacking a hood and engine, but has the transmission and differiential with half-shafts that I need to get the power from the 20B to the rear of the car and finally out to the tires.

Last modified on Sunday, 24-Jul-2005 03:14:30 EDT.