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sevenracer Reader
2/14/21 12:00 p.m.

I've been meaning to start this thread for a while. Started working on this back in the summer - or at least cleaning and organizing the garage to get ready for this. Have been working on it in earnest since December, and I'm hoping to have it driving by end of March (ha - we'll see).

I got this car used way back in high school put over 100,000 miles on it through college and first real job, loved it and just kept it around. Started doing track days with it in the early 2000's, then stepped up to W2W racing in a different first gen RX7 shortly after that. In 2006, I stole the engine out of this car to replace the one I blew up in the racecar. I intended to do an engine swap, and bought a bunch of parts for that, but then we wound up moving right after, so everything got packed up and moved, and never really touched again, other than a couple of false starts over the years. So, now that I find myself at home way more than usual due to covid, seems like now's the time to get this done!


Here's the car -it had definitely become a shelf over the years:


Awesome, the wheels still turn!

First sunlight in about 15 years!

After a bath:

Cleaned out and inventoried all the crap I had stored inside:

Found this long forgotten gem in the center console!


I guess that's a good intro for now... more to come.

jr02518 HalfDork
2/14/21 1:29 p.m.

I am looking forward to how this comes together.  Have you picked what kind of events you will be driving the car in?

sevenracer Reader
2/14/21 8:55 p.m.

In reply to jr02518 :

Um... Radwood? laugh

No plans for track duty in this car's next chapter. Planning to take the rollbar out and put the original seats back in and focus on making it a fun street car with a power upgrade.

sevenracer Reader
2/23/21 10:26 p.m.

So, a little more of the my attempt to get some momentum on this project.

I am not one to naturally keep my shop clean and organized, so I needed to do a significant clean up and make some room to work.

made a couple of carts using furniture dollies:

And a transmission tree...

Certainly still too much junk around, but way better and most everything is on wheels, so easy to reconfigure the space...

dannyp84 New Reader
2/24/21 11:21 a.m.

panasports! :)

obsolete Reader
2/24/21 1:50 p.m.

I love it, especially the transmission tree. Every GRMer needs a transmission tree.

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
2/24/21 1:53 p.m.

Ive been in your shop!


Glad to see you back. Or at least see you posting. Thanks again for convincing me to get the ace for my miata.


If you decide to purge rollbar or highway gears for the rx7, or just need a hand, let me know and ill do what i can to help!

sevenracer Reader
2/24/21 11:11 p.m.

In reply to Dusterbd13-michael (Forum Supporter) :

Yeah, I mostly just lurk on here, but figured I should document this build. Glad the ACE bar worked out for you. I'll let you know if and when I'm looking to do something with the rollbar out of the RX7, but it's probably a while before I'll be messing with that - too many other things to work on just getting it running.

sevenracer Reader
2/25/21 12:13 a.m.

So, it's late and I'll do more of a writeup soon, but I mentioned above that I was looking to do a power upgrade. The 12A is a fun motor and perks up a little with an intake and exhaust, but a stock RX7 was actually kinda slow even back in it's day. I definitely wanted this version to have more modern levels of acceleration.

I had three different options in mind that I spent WAY too much time trying to decide between, mainly because I really wanted one of them in particular to work out.

I started to write that the three options were kind of a goldilocks choice (you know, this porridge is too cold, this is too hot, this one's just right), but that didn't really fit. I'm not sure if this analogy holds up much better, but it's more like choosing between:

1. That actress that you've already informed your significant other  is "on your list". I mean, it ain't never gonna happen, and you'd probably make a fool of yourself trying to make it happen, but IF it did happen it would be epic!

2. That girl next door who is beautiful and nice, and someone you would be smart to settle down with.

3. That redhead that's borderline crazy and guaranteed trouble, but you just can't walk away.

sevenracer Reader
3/7/21 11:07 a.m.

Ok, this is going to be a wall of text with a few pics, but here's some background on engine selection. 


Option 1: GM LFX V6.  Just to not get anybody’s hopes up, this isn’t the option I chose. I got this idea from the v8 Roadsters Miata swap kit.  And honestly, I got really stuck on this option because it would offer the most power and torque by far and easy to find parts for years to come. But, clearly this is a much bigger project – I thought I could leverage some of V8 roadsters’ products, but there was still a long list of solutions that would have to be developed to get this done.  I went down the rabbit hole of what it would take to make this work, and although I didn’t find any actual 100% show stoppers, I could see that this would be a much bigger project. 

I actually was surprised that I could not find good exterior dimensions for this motor online. I found where someone had posted dimensions from their Colorado, but they were pretty vague and not complete. I tried to use pictures of swapped Miata’s and measurements from my own Miata.  I asked v8 Roadsters if they could provide a couple of simple measurements, and they kind of blew me off. I found pics of a bare block, and using the cylinder bore dimension, tried to extrapolate how long and tall the motor was. I even went to Carmax with a tape measure one night and attempted my own measurements on a Camaro (the salesguy was definitely like wtf, but I’m not on commission so whatever). I never really got a clear answer on how tall the motor was above the center of the crank. There may been a major hood scoop required, which doesn’t really work for me.  Ultimately, I wasn’t willing to buy a motor for a test fit because I think the overall project is too big, so I moved on to the other 2 options (with only occasional longing for what might have been, lol).


Option 2: Renesis motor. This was actually the most likely candidate when I started thinking about getting this car back on the road. I like this idea because it would match the character of the original motor except would have about double the power to the wheels (with none of that pesky torque to break transmissions and differentials). Plus 9000 rpm! And significantly, I have friends who have swapped Renesis motors into 1st gens for road racing.  I could leverage a lot of their efforts and have the car on the road in relatively short order.  There are a few downsides though. Namely cost because you cannot use the factory ECU, and I would budget for an engine rebuild because these motors have a terrible reputation (fairly well deserved on the early ones) for reliability/longevity and low mileage used motors are pretty thin on the ground. A quote from one rotary shop owner I talked to “I’ve had four of them and you couldn’t pay me to own another”. But, I honestly think the reliability issue could be mitigated, and realistically, the car is only going to see maybe 1-2k miles per year, so if the motor lasts 50k miles, that’s ok. So I’m not totally scared off by the reliability concern.

I borrowed a core engine from a buddy:

And I have a set of motor mounts they made up, so let's drop it in:

Looks like it was meant to be there:


Option 3: 13B Turbo. This was the original plan back in 2006 when I yanked the original motor from the car.  I actually bought a jspec motor/trans plus a bunch of other swap parts years ago – it’s been sitting right beside the car for more than a decade.  So, this would be the obvious choice, but I am concerned about the supportability of an 80’s turbo rotary from a reliability and parts availability perspective. And I mean reliability as in keeping all the vacuum lines and solenoids and archaic ECU/ignition/sensors happy and finding replacements when needed.

I've been tripping over this for like 15 years, maybe I should put it to use:


TII motor next to the Xmas tree my wife surpised me with for the garage:

This could work:


So, deciding which route to go is what I spent waayyy too much time waffling over during the late Summer and Fall.

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
3/7/21 11:19 a.m.

Im guessing turbo2 with megasquirt 

mr2s2000elise UltraDork
3/7/21 11:20 a.m.

Pretty car, even sexier wheels 

WonkoTheSane (FS)
WonkoTheSane (FS) SuperDork
3/7/21 12:17 p.m.

A Tii in the hand is worth a Renesis in the bush...  Or something like that.

Seriously, most of the hard to find stuff on a Tii is unnecessary if you're going standalone anyway.

sevenracer Reader
6/7/21 11:18 p.m.

Dredging this back up. I've done a fair amount on the car, but plenty still left to do.

So, I am going with the TII motor, not the Renesis. Slightly less cost and effort to do the Renesis, but after going through all the effort and expense, I want this car to feel quick, and I'm not sure how well the Renesis would deliver on that, and there's no easy way to add power later. I am not going crazy with the TII build - hoping for 200-220whp, but there's a clear path to way more power if I ever feel the need.


Here's a very pseudo scientific analysis I did to try to get a sense of how quick the car would feel. The intent was to baseline against my BMW Z3M. It's definitely a car that feels quick (not crazy fast) and has a satisfying amount of torque, so I used that as a baseline, used dyno plots and gearing to quantify how much "thrust" (engine torque*torque multiplication in each gear*a coefficient for delta in weight) would be delivered vs the Z3M. Basically, my mild tune TII should be about on par with the BMW after weight and gearing is factored in:

I'm thinking the RX7 will feel faster due to being less refined and more traction limited!

sevenracer Reader
12/12/21 10:32 p.m.

A good amount has happened on this project, just haven't been posting up. Unfortunately, a good amount left  due to some scope creep and sporadic time spend over the past few months, but trying to make a strong push over the next few weeks to get this running.

Figured I'd do some photo dumps to catch things up here over the next few days.

My plan was to just focus on the engine install and supporting components like fuel system, but the underside of the car was a bit crustier than I realized, and dealing with that would only be more difficult later, so I did a lot of wire brushing and rust treatment starting with the back of the car and working forward. This type of work gives me no joy, and so this dragged out a bit as my enthusiasm waned a bit.

Before examples:


A couple of after examples:

GasTungstenArc New Reader
12/13/21 8:48 a.m.

The TII engine is not known for having a long life, but as you said, you're driving it 2000 miles per year.  At that pace, the TII engine should give you 30 years of service, at least from an apex and side seal standpoint.  

I wanted so much to swap a TII engine into one of the four first gens I have owned, but it never materialized.  At this point, I no longer have any prospect for owning another first gen, and I also would not want to start buying TII parts at 2021 prices and availability, so I will have to watch from the sidelines.  

The first gen has a Miata-like ability to make 100HP feel fun, so doubling that and better-than-doubling torque will be a blast.  

Dusterbd13-michael MegaDork
12/13/21 10:23 a.m.

That underside looks great!

sevenracer Reader
12/13/21 11:59 a.m.

In reply to GasTungstenArc :

Sounds like we are on the same page. I've been wanting to do this swap for along time and actually bought the TII motor over 15 years ago. Looking forward to seeing how the boosted motor feels in this chassis.

GasTungstenArc New Reader
12/13/21 3:17 p.m.
sevenracer said:

In reply to GasTungstenArc :

Sounds like we are on the same page. I've been wanting to do this swap for along time and actually bought the TII motor over 15 years ago. Looking forward to seeing how the boosted motor feels in this chassis.

Much like investing in Bitcoin, as early as possible was the correct time to buy rotary parts.  I remember seeing running 20B engines for $1500.   Now a core condition 13BT is going to cost you that much or more, and the supply of whatever parts it needs is drying up so fast.  

For the record, I failed to invsest in both.

sevenracer Reader
12/13/21 4:02 p.m.

Some more clean up pics. Again, I really didn't have any of this in my original plan, but I couldn't really see going back and dis-assembling to do this after the car was running.

Pulled rear axle, cleaned up the suspension links:




And cleaned up the exhaust heat shields and racing beat muffler/associated hardware:

pimpm3 (Forum Supporter)
pimpm3 (Forum Supporter) UltraDork
12/13/21 5:44 p.m.

Nice, this thing is going to be fun.

GasTungstenArc New Reader
12/14/21 8:29 a.m.

Are you going to use the RB muffler on the turbo engine?  Do you think it's going to give you the flow you want, given the turbocharger?  

Either way, treasure that muffler.  RB changed sources for the muffler, and now it's garbage.  I couldn't believe it until I saw it for myself.  I hope that the change is pandemic-related and that they will return to the original muffler when they are able to.  

sevenracer Reader
12/19/21 12:53 p.m.

In reply to GasTungstenArc :

I am going to use the RB muffler with the TII motor. I am only looking for 220-ish whp, so I'll think it'll be ok.

sevenracer Reader
12/19/21 1:33 p.m.

A few pics of the fuel system upgrade. Original system fed a carb at ~2 psi. Not really gonna work for this application!

I had bought what I thought was a GSLSE fuel tank years ago which has a cup mounted inside to prevent fuel starvation, but once I started cleaning it up, I realized it was a non GSLSE tank with no cup. After looking at different options, I found a guy who had been into FB rx7's with TII motors back in the day and had made an in tank surge tank/lift pump kit and offered it for sale. He's been out of that game for a long time, but he was kind enough to dust off some parts from his stash and sell me a kit. It's a nice solution with a lift pump integrated into the surge tank, and a low limit switch that can signal the ECU to shut down the party if there is a threat of fuel starvation. I am mounting the high pressure pump in the original fuel pump bracket. I mocked the lines and filters up about 80% before pulling everything off to clean up the underside of the car. Will need to finish the details during final assembly.






Also fabbed up an ugly bracket to hold the port for the Fuel Pressure sensor. It will live up in the engine bay after a stock TII fuel filter:

sevenracer Reader
12/27/21 10:16 a.m.

Some cooling system and oil system pics

I'm using a radiator that's an aluminum copy of a stock unit. I had it in my racecar for a while and it was adequate in that application. Hopefully, it's enough for this street application.


Radiator bolts up to stock shroud pieces. Planning to go with an electric fan, stock fan is quite close with the 13B.

I bought an aluminum replacement thermostat neck that didn't really work - wrong angle

stock neck works much better (no pic, but I found an aluminum copy to replace the aged out plastic oem part)

lower rad hose angles also not great, but I found a hose that will work, and put a coil inside for good measure

I'm using a 2nd gen oil cooler, after fiddling around with it under the car, I'm offsetting it to the driver's side for best fit. Made up some brackets that work with the stock rubber isolators on the cooler, still need to add some gussets to stiffen them up before paint.


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