My 1990 300zx Twin Turbo build by megaDan

13 minute(s) of a 414 minute read

Kindly demand she learn how to drive stick? At least we're on the same page I'll make sure the couch has fresh blankets.If push comes to shove, the TDI is out. But with cost of ownership being so low, and quality of winter beater so high; it would probably cost me more to get rid of it. I plan on doing some preventative work on the silver mini this fall to prep it as much as possible for winter.

Anyway, now the fun update. This thread is about the Z, but given that this is TCL; some OT updates should be tolerated.

I've finished the 'necessary' work on the 2006 JCW I picked up 2 months ago.

What it looked like when I brought it home.

How it looked after a month in the garage.

The original owner said he only had it serviced at the dealer, and I have no reason whatsoever to not believe him. The quality of the work was pretty shocking (ly poor). Self tapping sheet metal screws going into machine screw nuts to hold the bumper in place; intercooler clamp bolts snapped off and left in place; broken wiring; oil filter cap tightened by king kong; etc. Thankfully none of this led to any serious damage and all was relatively easily repairable.

I got it done in time for the British Car Field Day in Sussex and the previous owner showed up with his 2022 JCW Clubman. He was thrilled to see what I had done to his treasured mini.

Didn't take home any prizes; but got lots of complements on how clean it was.

I'm still waiting on plates to show up so I can't take it anywhere frivolous; and I'm waiting to find the wife a minivan before I spend any money on this. It needs shocks/struts/pads; but each of those will be getting an upgrade.

5-18-2022

Holy **** it's been a busy 8+ months. It's a challenge (and sometimes disheartening) to keep this thread up to date.

TLDW (too long, didn't write) summary:

• AC got a bit weak days before before Radwood Chicago. Found a leaking high side port. Broke schraeder valve trying to remove it. Managed to drill it mostly out, use a bit extractor for the rest, and evacuate debris using a little pneumatics know-how.

• Trip to Radwood with a buddy was excellent; although I wasn't a huge fan of the show. The 100F weather and the fact that it was hosted on top of a parking garage probably didn't help.
• Found oil on my hatch towards the end of the fall. Literally moments after I was thinking to myself how awesome it is to finally put the Z away needing no work and having no planned improvements. "It's done"....or so I thought. More on this later.
• Finally found a Sienna for the wife. Brought it home in November. She's happy so I can resume normal automotive shennanigans.
• Decided to capitalize on the used car market and sold both the Volvo and my $800 Mini for almost unfathomable amounts within weeks of each other. Stable is back down to 4 vehicles.
• Brought home an 06 MCS to scavenge for parts.
• Turned my 06 JCW into my dream build mini....mostly. Elevated to DD duties for the summer. More on this also.
• Got a bid to World Masters Ultimate Club Championships in Ireland. Leave in just over a month. All of this while training my ass off.

Well. Where to start. As expected, seat time in the Z has been greatly reduced as we are now a family of 3, and the youngest member is not allowed to ride in it yet. With the highlight of my summer and our major cars & coffee event cancelled (RIP 😭), I really only got to commute in it. Once my cooling and AC issues were sorted out that I covered last year; it was pretty uneventful.

On my last planned drive/commute of the year I opened it up on the last big straightaway before work and saw some smoke and thought the turbos whine sounded a bit funny. I parked the car without thinking much of it and noticed oil on the hatch.

It's kind of hard to see; there are droplets on the spoiler and a larger spot just above dead center in the photo.

I've been encountering occasional smoking on decel, with the guess that the seals are starting to go on the turbo. I got them used 10 years ago; running them usually at about 18psi, and ~23psi since early 2019. They've served me well but have had a hard life. When I saw the oil I just figured it was REALLY time. I parked it and didn't touch it again until February. I had to prep my mini for a NC road trip, prep the wife's van for daily duties, take a few trips, chop up another mini, and be generally busy. Plus, it doesn't help that my worst personality trait is I try to avoid confrontation; especially when that confrontation involves me uncovering bad news. So I let it sit.

In February I finally got it up on the lift to start poking around and test my hypothesis. I found cooked oil on the bottom of the drivers side turbo housing:

None on the passenger side:

This was no smoking gun, but it was an interesting discovery. At this point I dropped the exhaust and downpipes and found that the drivers side turbo had some axial shaft play (not good on a journal bearing turbo) and the passenger side did not. This didn't definitively confirm that the oil on my hatch was from my turbos, but it indicated that now was probably time to address their 'age'.

What I SHOULD have done at this point was a compression test to verify there was no other major engine issues (further pointing to turbo problems) but I was afraid of bad news and I hate doing compression tests...so I focused my efforts on coming up with a solution for my turbos. Oops.

Yeah...its not that bad. It's less reaching the plugs and more needing to let the car idle in the garage (its winter remember), pull the fuel pump relay, pull the plugs, do the test, be afraid of the results, etc.

My initial plan was just to swap CHRAs. Last time I looked they were $500/ea. But they're NLA. Awesome. The Z32 community immediately chastises anyone who suggests rebuilding a turbo; which I don't necessarily agree with but I am by no means a turbo expert. I was quoted ~350 to have it rebuilt by a reputable local shop. Now the mental gymanstics start.....do I rebuild just one? Both? Do I spend $700 on a potentially iffy fix? The only other potential option is a ball bearing turbo; but by the time I get BB turbos, downpipes (there are no 4 bolt BB turbo options), and a tune I'm well past whatever tiny budget I have.

While I mulled this over, I pulled the engine and let it sit for quite some time until I found a surprise buyer for my $800 mini project. I dialed back the scale of the build on my JCW and redirected some of those funds to the Z. I reached out to my tuner and he advised that if I went for the smaller of the BB turbo options, my current tune would be sufficient.

Once I obtained the wife's blessing my plan was set in motion. GT2554R's. They have a few different brand names in the Z community; JWT 530BB, Z1 GT535R, etc. They're comparable to what I was running previously which just a little bit more top end. I don't need more power; I just need something a little more capable of running the boost levels under E85. Between setting the wastegate preload to 15psi (vs 12 prior) and the slightly larger/faster spooling assemblies; I think this will give a nice bump in power and land me in the low 500's with my current tune, assuming my clutch holds up. I definitely don't need any more power, and can't really put any more down with my current tire/wheel setup. I guess it will make 3rd gear pulls more fun.

Side note:
I really have learned a lot during this process. Up until this point I thought my boost controller was keeping the wastegates shut until my desired boost levels. I never really took the time to understood exactly how they worked. I think part of the reason I was mildly disappointed with my power levels is that I was making power at 24psi...but my wastegate preload was only 12psi. Even with my boost controller set to 24, they were opening well before that; reducing mid-range torque and power. With proper pre-load I probably could have seen 500whp with my previous setup...which makes me very excited to see what these new turbos are capable of when properly preset.

With new turbos purchased I realized that I could now sell my downpipes and turbos (for rebuild) to recoup come cost. The drivers turbo was already removed, and when I pulled the passenger turbo I found the exhaust turbine to be wet with oil....and then the exhaust manifold....and then the exhaust ports. OOf. Why oh why didn't I do a compression test?

View inside exhaust manifold and exhaust port. Awfully oily and milkshakey looking.

I found this the day before we left for a family trip to Puerto Rico. I thought it would be difficult to enjoy the vacation with the level of despair I was feeling; but it was quite the opposite. We had a blast and I forgot all about the Z and came back fresh.

I wasn't able to do a compression test with the engine on the stand, but a leakdown test was mostly easy. I had to build a bracket to lock the crank in place, but otherwise it was pretty straightforward. It took 2 days to get it done; but the results came back at ~5% loss at 100 psi consistently across all cylinders. At this point I agree with @Air and water do mix's prediction that it's the turbo.

I've burning the candle at both ends between trying to get the Z sorted and maintain training levels for the World Championships. There are enough small projects in the works with the Z that when I hit a roadblock I can switch gears and come back to it. One evening in the garage I had an epiphany and started to trace the oil back through the engine in the opposite direction. Oil in the intake ports....and in the intake manifold....and in the PCV system. Doh. The Z32 is known for pulling oil into the PCV intake from the drivers side valve cover as it sits pretty low. Many people relocate this to prevent smoking and oil ingestion. While the oil is a nuisance; at this point its no longer a serious concern. I'll begin sourcing a spare valve cover to perform a relocation at the next major service.

Two boxes filled with new turbo goodies....a wonderful sight.

Practically the same size, but much newer technology.

It took a little bit of finaggling. I had never installed brand new turbos before; and these required some clocking, wastegate preloading, and adjustment. As you can imagine, install was a pain. Even with the engine out of the car there is no spare room. There was a lot of cursing and stops and restarts while trying to massage heat shields and hoses and orient gaskets. While the engine was out I gave everything a good once-over and replaced some heat-aged hoses and clamps; but overall I was pretty pleased with how clean it remained. I do have a bit of oil weeping at the front, but removing the timing covers doesn't interest me at this point; and I think resealing the valve covers will help.

I got the engine back in Monday night; and tonight my downpipes will be delivered. Now it's a mad rush to finish it as my birthday is Sunday and I'm due to take a road trip Saturday. It would be one hell of a birthday present to be able to enjoy this thing. It's going to be REALLY tight. But if things go well I have about 6 hours of dedicated free time, 10 if i push it. Wish me luck.

Install downpipes, flywheel, clutch, transmission, driveshaft, exhaust, oil change, coolant fill and wiring harness install. Totally doable right?

Oh yeah and then pray everything goes right and I didn't miss a much more glaring problem.