Recommissioning my 82 RX7

I did another test yesterday where I disconnected the return line at the back of the car.

A couple of things noted:

1. With the car cooled down, upon starting it, the pump is quiet and the fuel pressure sits steadily at 85-90psi. Within about a minute, the pump starts squealing and the pressure drop cycle starts.

2. Absolutely no gas flowed from the return line while it was disconnected and the car was running. There was a little bit of gas in the line when I first removed it. Under normal conditions, there would be some amount of fuel flowing through the return line, right?

In reply to sevenracer :

Yes. Under normal conditions, almost all the fuel the pump puts out comes back the return at idle. At least on normal cars. Cant see why it would be different for rotary 

In reply to sevenracer :

Yes, there should be fuel coming from the return line when running.  At least on my stock-ish S4, that's how it works. I think you're right to suspect the FPR.

sort of a non-update.

I found a used secondary fuel rail (the fpr is welded in place - non replaceable), and I ordered a replacement fuel pump and a mech gauge. Thought I had everything lined up to deliver Thursday, and had Fri off work, so I could be ready to put some break in miles on the car this weekend. But, the USPS didn't hit their Thu 9pm delivery estimate for the fuel rail - no updates til this morning - now it's supposed to be here by 3pm today. Frustrating (but clearly 1st world problems) - I had asked the seller about it, and he said $10 for USPS and should get there by  Thu or Fri or $70 for next day or 2nd day air.

I looked at going to an aftermarket fuel rail - there are several options, but all in it's probably about $1000 to do that once I buy the rails, required new fuel injectors, an external fpr and all the fittings, plus a good bit of work to find a spot for and mount the fpr and get piping to it. If I was chasing big power numbers it would make sense, but I'm not, so seems like mostly a waste of money.

In other news, I picked up a spare hood this past weekend which will get some sort of hood scoop to feed air to the top mount intercooler. I have a stock TII  scoop front inlet trim piece, but don't think I have the fab skills to make a scoop and a recessed area for the inlet, so it may be an ebay or summit scoop as an interim solution. Don't want to cut up the original hood, because I may move to a front mount intercooler some time in the future - I prefer no hood scoop and if I have to have one, ideally its a TII scoop.

Planning to spend some time today scoping out the AC evap and expansion valve and maybe pull the roll hoop out since I'm going back to the stock interior.

New to me fuel rail (with FPR) arrived Sat afternoon and got installed this morning. Fuel problem solved - steady 43psi (with pump running, w/o the engine running). Buttoned back up and did a 10+ mile and a 20+ mile outing today... all under 4500 rpm, partial throttle and staying out of boost. Car runs really well, starts easily, idle is smooth, revs nicely. Only drivability issue is a slight jerkiness going from no throttle to very slight throttle.

I do have an issue with the IAT reading way low. This is a replacement for the first one that didn't seem to function at all. So, I've been running a  different size IAT plugged in but hanging in free air and the bad sensor just plugging the hole in the intake.

I have been using a fixed back racing seat, but I pulled the roll hoop out and got the stock seats down from the storage shelf. Seat belts are currently MIA, but I have them here somewhere. Want to starting refreshing the interior soon.

Oh, and I guess I need a hood at some point 

In reply to sevenracer :

Congrats on the short drive!  Those always feel great.

Congratulations, looks good!

The main issue with the hood situation (I'm about to be in a similar position with my FC, needing a TII hood) is that the TII intercooler is off-center. This isn't a problem with the factory TII hood because the lines for the scoop are indented into it, showing its supposed to be that way.

When cutting a straight hood to install a scoop, it's hard to add those lines. Then to anyone who doesn't know Rx7s it looks like your scoop is off-center because you didn't measure before cutting.

Haven't had too much time to work on the car due to some weekend travel and work stuff, but have done a few things.

I loaded the correct calibration file for the IAT sensor, so that's working correctly. Also, enabled OBD output from the ECU and added an OBD Bluetooth adapter, and now I can run the Torque app on my phone to see speed, track miles driven, and see engine vitals like IAT temps, fuel pressure, manifold pressure. Speedo cable is not yet connected becuse the connector housing on the trans is damaged. Have another one ready to install, but it's lower on the list.

Last Sunday, was able to put about 50 miles on the car, with no real issues. Took it out on the highway for the first time too. I'm really pleased with the power - even only boosting to 2 psi under partial throttle. I think it's going to be a hoot with full boost.

I also fitted the spare hood. Surprisingly, it fully closes and latches with the hood webbing. I used some white grease to try to get an outline of where the intercooler gasket contacts the hood.

I did drive it a few miles with the hood, and as expected the intake heat soaked pretty badly. IAT got up to ~125 deg F with 60 deg ambient. So, I'll be cutting a hole here pretty shortly.

Intercooler gasket marks (underside of hood is blue)

I'm starting to focus on the interior, now. Have a some carpet color samples on the way, and a dash cover, and bought some SEM paint in different shades to test out.

Before I can finish the interior, I want to get the AC expansion valve replaced. I got the evap box pulled, so I could verify which valve type I need. Looks like this was a port installed AC system. the two halves of the box were sealed together with some type of glue. Luckily the glue was more brittle than the box, so I was able to get them separated.

Need to come up with a way to pressure test the evaporator. Not sure I can get fittings to do a vacuum test.

The car has been off the road for a few days as I've been tackling a few things.

I did have an issue that could have been really bad, but luckily was no big deal. I took that car out one night last week, and on the way home at a stop sign about 200 ft from my driveway, the low oil chime came on. There was a nice trail of oil on the road and my driveway. The upper oil cooler hose was leaking significantly on the cooler end. I made up a new hose and all seems good. The oil lines are made with push-lock fittings and hose, I used the summit brand hose originally, but made the new line with Aeroquip hose - so I'll be watching these for future issues. Really didn't expect problems with these as I've been running the same setup on my race car for several years with no issues.

I also spent a bunch of time trying to figure out where to cut the hole in the hood for the intercooler.

I tried to use the rubber gasket that sits between the IC and hood, but it only contacted a couple of spots on the webbing and the gasket is quite floppy, so hard to know if it compressed nicely or splayed out under the hood. I got a rough idea and cut out some webbing, then discovered that the gasket wasn't contacting the hood skin all the way around. So, I put in some bolts standing proud of the gasket in the mounting holes with grease on them. I installed the metal mounting ring too over the bolts and stuffed cotton balls under the bolts to try to keep them from deflecting. I eventually got a decent pattern transferred to the hood.

Then, with much trepidation, I cut a hole a good bit smaller that the gasket to check how aligned it was, with some ability to correct if necessary. It actually lines up pretty well with the finned portion of the IC.

I am now trying to decide if I temporarily use a hood scoop I bought from Summit. It's just barely able to cover the existing hole. I don't hate the aesthetics of the scoop, but it is pretty flimsy and just sticks on with VHB tape. Plus, it actually doesn't have an opening for air to enter (i.e. not intended to be functional). I could cut out the front to remedy that. Not sure if I want to do that, or just return it and drive it as is for now.

Ultimately, I'd like to build in a TII size scoop to fit the TII inlet trim piece I have, but that's a fairly big project, and I'd like to focus on other things like the interior first.

Other than that, I've been working on sealing up the cabin a bit ahead of installing the interior. Til now I've been driving with no seal over the gear lever, and with holes in the rear wheel wells where the roll hoop was mounted. I bought the parts to seal up the gear lever to the trans and the seal that goes over the lever and seals the cabin, just need to get those put in.

I tacked in some patches over the holes in the wheel wells, and will paint and seam seal them. There are mounting holes in the floor behind the seats too, but with a bunch of asphalt sound deadening around them, a good bit more work to get them ready to weld, so those just got duck tape for now.

In the FD section of the RX7club, there are some threads on a fast reacting ait sensor. Assuming the thread pitch is the same, might want to look into it 

I already have a Haltech fast sensor for IAT. I drilled and re-tapped the stock location for it. I think it's working fine.

In other news, I took the car out yesterday evening for some more break in miles - and made it about 2 miles before the problem oil line blew out again. The first time it went, it was peeing a steady stream between the hose and fitting at the oil ooler side. This time, to better make it's point, it completely blew the hose off the fitting at the engine side.

So, for date night, my wife brought my truck and a tow strap and dragged me the ~1 mile home. I don't think any damage was done to the motor, it was barely above idle and I turned it off just a few seconds after the warning chime started.

Obviously, I need a more robust hose solution, so it will be a few days before it's back on the road.

Makes a big mess:

Got my parts from Summit yesterday and fabbed up new oil cooler lines. I went with Vibrant hoses and fittings based on price and availability. I also wanted black hose ends vs the red/blue style.

I guess I didn't take a picture of the completed upper line, but I used 2 45 degree fittings which worked pretty well. It's a very short hose, so very little flex available for engine movement. Think it's ok but will be keeping an eye on it.

Here's the new lower line next to the push lock version. The picture makes it look like the new hose is longer, but they are nearly identical in length with the hoses straightened out.

Anyway, after idling it for a bit and not seeing any issues, I took it out and put about 30 miles on it, and my total is up to almost 100 miles. Hopefully will be able to add a good bit more miles this weekend.

Current update. I had fabbed up new oil lines on Wed, took the car out Thu and did about 30 miles, another 50 on Fri, and about 90 miles today. I'm about halfway through my 500 break in miles. No major issues - car is actually running really well in light throttle, low boost, break in mode. Can't wait to get past break in and start to get it tuned.

Since I got the car back on the road, I've been running just with the driver's seat with a bunch of tools/spares on the passenger side. My wife had asked when she might be able to go for a ride. In deference to her patience with me and the project, I figured I better move installing the passenger seat up on the priority list!

 I actually put in the passenger seat just before I blew the oil line, but there were a couple of issues. One, the right side seat rail wouldn't  fit down over the mounts - no idea why. I tried bending the tabs with some success, but still not right - I wound up slotting the front of the rail to get it in. But unfortunately, the threads in the body that the seats bolt into were knackered and the bolt wouldn't torque down in the right front - so the seat was only secured at 3 points which created a nice hobby horse effect.

 No problem, right? Just drill out the M8 threads and re-thread for an M10 bolt. Yeah, so this happened:

So, after my drive today, I set about repairing that:

That should do it. Will paint tomorrow, and I'm also going to re-weld the seat rail so it's not open ended.

So, I was kind of curious what it would be like driving it after all this time - whether the magic would still be there, or as they say, you can never go back. Yeah, I'm digging it quite a bit. Of course the car has a decidedly vintage feel at this point (especially the steering), but the new motor feels much more modern in a good way, smoother and better throttle response than the original 12A, and even with barely dipping into the power, it's pretty lively. Feels way more torquey than my 99 Miata. Sounds good too.

Random photo from out in the wild (S. Charlotte exurbs):

Very cool. Glad to see another cool car back on the road. 

Minor update.

My efforts to put the interior back together have been stymied by the AC evaporator. I had pulled it and cleaned it up, but when I went to re-assemble, one of the pipes didn't thread on properly. On closer inspection, the fitting is cracked. Since, the evap needs to go in before I re-assemble the dash, I have been stopped on the interior. I can get a used evaporator off ebay, but a bit difficult to know if it's a direct replacement since my AC was port installed vs factory. I tried a little bit Friday to find a shop that could solder in a new threaded fitting to the one I have, but didn't find anyone yet.

On another front, as I've been driving the car some on interstates now, it had a pretty significant vibration at highway speeds. So, I decided to sort that out before doing a lot more miles. I figured it was either tires or driveshaft. I had modified the stock trans mount to use with the T2 transmission, and had measured it as best I could to get the output shaft at the same height as the original relative to the mount. I just tacked it together thinking it may need revisions once it was road tested. I thought maybe the tack welds or the rubber bushing had failed, but I pulled it apart and it was all still intact. I welded some areas to strengthen it a bit and re-installed for now.

The tires were "nearly new" when the car was parked 15 years ago. I had bought a bubble balancer years ago and never used it, so I dragged that out and set it up to check the balance on my tires. Basically, I didn't really find it to be repeatable. I even modified it by replacing the pin fulcrum with a large ball bearing, but it still didn't really seem to be repeatable. So, it was already my eventual plan to replace the tires - I just went ahead and ordered up a set of Conti ECS. Got those mounted yesterday. Result - much improved! I did a quick stint on the expressway, and it was much smoother, essentially no issues.

If you can get the fitting, ive got a guy out in albemarle that can do it  

Another item checked off the list - I got the speedo working. 

This had been a lower priority to fix since I have GPS speed from my phone. At some point in time the cable had slithered out of it's sheath, and I had set it aside. When I did recently try to finish the speedo cable install, I realized the threads on the transmission for the cable attachment "plug" had been sheared off. Unfortunately, didn't notice this before the trans went in. Luckily, I have a spare "plug" from a 1st gen trans. All the critical dimensions look the same. The gear is different, but tap out a tiny roll pin and swap it out  - no big deal.

Cleaned and lubed the cable and re-installed in the sheath connect it up to the trans. Go for a test drive and... nothing, not even a blip of the needle on the speedo.

Come back a few nights later to troubleshoot. I remove the cable and spin the rear wheels, while watching the cable receptor in the trans - no movement. I'm not sure why I thought to do this, but I removed the bolt that secures the plug and clocked it about 90 degrees. Spin the tire again - cable receptor spins! So, it took a while for me to figure it out, but the two plugs are subtlety different. The gear and shaft and cable attachment are not concentric to the plug. Offset be 1-2 mm. And the two plugs are offset differently relative to the mounting tab. Not sure the pic really shows it:

To solve this, I made a new "keeper" bracket that holds the plug in while it's clocked in the working position. I'll make a final version when I finish the trans mount. I realized after making it, that I needed to clock it further to match the offset to the original plug. Anyway, it's secured ( added a zip tie through the keeper hole that prevents the plug from rotating back, and a rib on the trans case keeps it from rotating further). Test drive and the speedo is back in action! All my stock gauges are now functional.

Good detective work!

That RX is really coming together.

Thank you for sharing the story!

The retainer may be dependent on which gear is used.  I have swapped gears in the same retainer without issue, but maybe things stacked up against your favor this time?

The housing for the speedometer driven gear is different for different final drive ratios. I learned this the hard way when I swapped a 4.30 final drive in my FC that originally had the 4.10. I ordered the correct driven gear and installed it in my 4.10 housing like you did thinking all would be fine. The result was me shattering the drive gear on the transmission output shaft when I forced the driven gear/housing assembly in. I had to drop the transmission and remove the tail housing to fix that. The different housings account for different diameter/tooth count driven gears since the drive gear on the output shaft is the same.