My 1990 300zx Twin Turbo build by megaDan

13 minute(s) of a 731 minute read

You might not have that impression from reading all the way back to the start of this thread; but I generally take pride in my intellectual ability and refrain from making really stupid mistakes or oversights. Or I'm just generally good at remembering to tie up loose ends on whatever I'm working on. Unfortunately that is no more. We've got a great baby, and I'm sleeping at least 6 hours a night but I'm still struggling mentally for whatever reason. In the last month I think I've made more mental errors than I have in the past 35. At the risk of being ridiculed, I have: Driven down the road with the hood open on the Volvo (narrowly missed needing a new windshield), shorted a battery with a box wrench across the terminals, started the pool without the automatic chlorinator installed (IE an incomplete plumbing system), along with countless other 'wtf did I just do' moments. I'm not sure if I'm preoccupied or just more tired than I realize. It's really frustrating, but I'm working on finding ways to cope.  

I know that part of it is due to no longer having the time to finish a project in one sitting; so spending 5 separate evenings on a project increases the chances that I'll miss or forget something on reassembly. I've got an Echo input on my garage stereo, so I've been using that to set reminders mid-project. I can create uniquely named lists and I just need to make sure I check all my reminders before wrapping up a project. I've used it for shopping lists in the past: "Alexa, add PB blaster to my shopping list"; this way I don't run out of mission critical supplies.

I've had another somewhat productive month. In addition to getting both of our Volvo wagons roadworthy again and replacing the transmission oil in our lawnmower, I crossed off the remaining items on my to-do list. I'm ignoring wax because it's still got a good bead when wet. I've been getting a little more time on the weekends to work in the garage, but most of this has been squeezed into the 1 hour I get on Wednesday evenings. Tonight is the first night where I don't have a to-do list for my allotted 1 hour of garage time.

Transmission before

Transmission after

DS Tire leak
I found this on accident while removing the exhaust to chase my smoking issue. I've got a screw through a treadblock. I'll need to get a patch kit and find a way to get it out. It's leaking about 1psi every two weeks so I don't consider it a major issue given I'm not going more than 20 miles from home on any trip.

Evaporator drip tube routing
This was 'fun'. All of my dash gages (boost controller, WBO2, fuel pressure, boost, etc) had been run through the evaporator grommet because my AC didn't work and I figured it never would. I guess I figured I'd use what was available at the time. I pulled all the wiring back through the grommet and got working on finding another solution. In the meantime simplified the wiring. For whatever reason I elected to run power/ground/data from the dash to the gages that needed it, rather than grounding the sending units locally. This cut back on the number of cables to run considerably. I also previously had my boost gage sending unit mounted to the intake manifold with 3 wires running back to the dash. I've moved it into the dash and have just teed onto the vacuum line that feeds my boost controller. In all, I reduced the wiring by about 40%.

I remembered from my stereo install about a dozen years ago that there was a fender pass-through below the battery tray and pulled the wheel liner on the passenger side to see what was available. I found another entry point that provided access to the passenger footwell.

Amp power fed into door...grommet? I'm not sure what to call that thing. Protected from the elements, but also entry from below to prevent any possible water ingress.

Helloooooo

I've done a really poor job of documenting every aspect of the job, but what I did was cut a hole on the bottom of the grommet just like I did with the amp cable and ran the vacuum line and a half dozen wires through that. Unfortunately this increased the distance most of the wires ran by about two feet, so some needed to be extended. If I had more experience and time I would have created a weatherpack connector at this location so it would be more modular; but for the number of times I need to mess with this it's not worth the investment and sacrifice at this time. This area is completely covered by the passenger side fender liner; while it's not water-tight, it is very well protected and I'm not concerned about water ingress here either. You can tell from the pictures above it's pretty clean and doesn't really see road grime.

Despite working on this project over the course of 4 days or so; _almost everything worked at startup. I missed one power connector for my WBO2. Considering how many modifications I made; I consider that a huge success.

I guess it's hard to tell, but there is quite a bit of room behind the dash.

Mid-project. Just to give you an idea of what was involved. Getting the dash to this point is only about 5 minutes of disassembly.

I apologize for the poor quality. Lighting was worse than I realized.
Alot of the on-board computers are located in the passenger footwell (hicas, security, ecu, etc) so I had to temporary remove them to give me space to work. I think I could be a professional contortionist at this point.


....continued in next post...

-Burn off 93oct in the tank so I can capitalize on that sweet sweet ~$1/gal E85

It turns out that E85 was $0.91 per gallon when I filled up roughly 10 days ago. Fuel cost per mile was about five cents, which puts it in line with my TDI at 45mpg. Stellar. Unfortunately prices have nearly doubled and as of yesterday it was $1.64 for E85. Oh well.

I also ran into a frustrating issue here. I copied the maps from my ECU to my laptop last fall when I switched back to the 93oct tune; and when I went to upload the E85 maps I got a missing data error. I've backed up maps plenty of times before with no issue; so I'm not sure if I did something wrong or if there was a new release of Nistune that somehow invalidated my previous ECU image.

Thankfully I was able to get the maps saved in April immediately following my dyno session to work; but I made a lot of driveability and cold start improvements that were lost and will need to be done again. Ugh.

-Charge AC system at the first sign of a 60F and sunny day
It took much longer than expected to finish up the wiring project, so my test drive was only about 15 minutes at the end of Sunday; I missed out on the beautiful weather all weekend. I did get to test the AC system again in the 75F sunny evening, and the AC was cold within about 4 seconds. I've heard that R134a in a R12 condenser can result in cool (rather than COLD) AC temps; but so far so good. I'm curious to see how it does on an 85F summer day with a hot radiator.

-Investigate smoking on decel
This wasn't on my to-do list; but I mentioned in a previous post that I was getting puffs of smoke on decel and since it was still April (and quarantine) at the time this was as good a time as any to do some investigation.

Based on observations, intuition, and lots of reading; the smoke was likely oil, and likely due to one of 3 causes:
-Valve seals. Gosh I hope not. This would be evidenced by smoke on startup (due to oil seeping from head into combustion chamber while the car sits) and oil on decel due to oil being sucked into the combustion chamber. I do not have oil on startup. Good sign
-Turbo seals. This is more to be expected given the level of boost I run these at and their age. This would be evidenced by smoke under load(no) or vacuum(yes), oil in the intake pipes due to a blown seal on the compressor side (no), or oil out the exhuast due to a blown/worn seal or shot bearings. A plugged drain line could also lead to this.
-Pluged/seized PCV valves. Evidenced by leaking seals all over due to a stuck valve not venting (maybe).

Given the likeliest candidates, I elected to investigate the latter two options as taking a look at the valve seals would be what I would consider medium level surgery. And I really didn't think they were the cause.

I dropped the exhuast to give me access to the downpipes. I really hoped to do this entirely from below the car; I didn't want to remove the intake manifold since the intake system was nice and tight. I've also never done this entirely from below before. With only a small amount of cursing, a U joint, 2 feet of extensions, a box wrench, and a ratcheting flex head box wrench, I was able to drop both downpipes and confirm that both turbos had zero shaft play. This doesn't mean the seals aren't bad, but it doesn't point to the turbos needing immediate replacement. Yay?

I did see some oil collected on the bottom of the passenger side compressor which is new. I couldn't for the life of me figure out where it came from. The exhuast manifold is directly above it, the outlet pipes are dry inside, and the valve cover gasket isn't leaking (also above). I'll have to keep an eye on this. I did drop the oil drain line from this turbo to confirm it wasn't plugged for some reason. No issues there.

Oil oil everywhere

You can also see a hint of oil at the turbine side of the CHRA, but I can't tell if that is from the turbo, or from somewhere else. Not terrible, not great. It's not resulting in oil on the ground and its not resulting in measurable oil loss. I'll continue to monitor.

I pulled off both throttle body intake pipes to confirm there was no oil coating the insides and they were bone dry. More good signs.

Just for the heck of it I pulled both PCV valves to check their health; and while one felt a little sticky and the other moved freely, they both spit out some dirty oil residue when I hit them with carb cleaner. At the time I thought this was of no consequence. More on this later.

As I did not find a smoking gun, my plan was to reassemble and continue to drive it. As soon as time would allow I plan(ned) on mounting a go-pro to the hood of a friends car so I could have more data on how, where, and when it was smoking.

During the first and only test drive after reassembly I still saw a little smoke, but only on decel, and only after boosting. Another interesting data point, but only anecdotal at this point. And that brings us to this morning.

I drove it to work today because why not, and because the weather is sunny, calm, and in the 60's. I took it easy the first half of the ride in, and was unable to get it to smoke. I eased on the boost a few times, and still no smoke. I hit ~16psi and it still wouldn't smoke afterwards. Awesome. Not concrete yet, but very encouraging.

What does this mean? Not sure, but the best I can come up with is that my PCV possibly failed in both directions.

PCV system traced in red. The circled blue valves attach to the underside of the intake manifold. The hoses attach to the driver's side valve cover.

One had stuck mostly shut, resulting in some oil being pushed by a seal here or there. Also both not actually fully closing either due to gunk/carbon/whatever on the sealing surface. This would have sucked oil from the valve covers straight into the intake manifold under vacuum when they should be shut. I'll need to get a few more drives in to confirm, but I'm very cautiously optimistic that this issue is resolved.

Other than that...it's driving great and still feels like a rocketship. Thanks to world and personal events I'm not driving it nearly as much; but it still puts a smile on my face every time I get in it. I'm hoping to schedule a drive into the countryside on an upcoming weekend with friends to get us out of the house and onto the road. I'll report back; hopefully with pictures. Stay safe.