Z31 Non-Turbo to Turbo Conversion

My research yielded a lot of really BAD and WRONG information (from sites other than Z31.com mostly), I am writing this purely to explain what I did, and namely the issues I ran into. Hopefully I will be helping someone out in one way or another. To begin with you should have already located a parts car or all the parts for a turbo conversion, this alone can be a challenge. Needed for converting an N/A car to turbo are the following parts from an 84-85 turbo Z31: (note: this information also applies to 86-89 Z31's as well, but there are some very small differences)

T3 Turbocharger and exhaust elbow from 84-87 300ZX Turbo
Drivers side exhaust manifold
Downpipe
Front crossmember (both the crossmember and engine mount bracket must be swapped for turbocharger fitment)
Drivers side engine mount bracket (bolts to block)
All intake piping (from Airflow meter to Throttle body)
Alternator mount, tensioner (and longer belt for application because the alternator mounts on pass. side instead of drivers side)
Oil pan
Turbo oil lines (and water lines if applicable)
Fuel injectors (260cc/min instead of 180cc/min)
Correct ECU (Interchange info here)
All applicable gaskets

For me these parts added up to almost $400 including all the random little bits I needed, for which I could have bought an entire running parts car, my mistake, oh well. Chris' suggestion was very good.

Now that this is out of the way.... moving on to my experience with the turbo swap on my Z31..

Lets start with the easy stuff... Swapping the fuel system.

The only major changes between the NA and Turbo engine control ECU's are their calibration for different injector sizes. Other fuel system interchange information is located<a href="../pages/fuel.html"> here</a>.

***DO NOT operate a turbocharged 300ZX with a non-turbo fuel system (only really ECU and injectors are different). The fuel mapping is far too lean and incorrectly calibrated for a turbocharged application, expecially if you plan to swap a turbo onto a 9:1 compression NA engine.***

Remove your old ECU in the passenger side kick panel, it is held in by two bolts. Install the new ECU as shown. At this time you may need to make a few small wiring changes depending on what ECU/injectors/O2 you are using. All 84-85 car owners will not have to worry about this if they are using an 84-85 turbo ECU. Again, that interchange information is <a href="../pages/fuel.html">here.</a>

<img src="../images/turbo/ecu.jpg" width="480" height="360">

Now, you can run the car with a turbo ECU for a test on NA injectors, but it's not a good idea to do it for very long as it will be very lean. Now comes a slightly less simple part, removing the intake plenum to gain access to the fuel rails. All of this information is provided in the Haynes manual (available at any auto parts store), if you do not have one... you should. The fuel rails will come out easily along with the injectors if you just cut the fuel lines, you should replace them anyway. Once you have the plenum ("collector") off stuff something into the manifold runners to keep stuff out of there. It should now look like this:

<img src="../images/turbo/oldgasket.jpg" width="480" height="360">

Now put some tape over the lower intake's injector holes, again to keep junk out of there. You may wish to replace the lower injector seals at this time if yours are at all brittle, they are very inexpensive and should be replaced. Now get something to scrape with and remove the old gasket (mine took about 2 hours of tedious scraping with a razor blade to completely clean off). The new injectors and fuel rail (or you can use your old rails) should have new hoses and clamps. Use only high pressure fuel hose and fuel injection hose clamps (NAPA carries both), you don't want to be cheap when it comes to gas in your engine compartment. After you put the new injectors in and remove all of the old gasket it should look like this:

<img src="../images/turbo/ready.jpg" width="480" height="360">

You can now put your intake "collector" back on using a NEW gasket (available at any Nissan dealer PN 14033-0B000) or by making sure both surfaces are completely clean and using an RTV gasket maker compound. Be sure to plug everything back in. Now cross your fingers and if you did everything right your car will run about the same as it did before, though maybe a little slower beacause of the turbo ECU calibration. Yay. Fuel injector/ECU conversion is done, now get ready for the hard stuff.

So now you have the real decision:

I ran into some troubles here. First off, you will have to remove the drivers side exhaust manifold, and chances are you will break studs in the process. Also, if you get lucky like I did, most of the heat shield bolts will break off as well. Here is your decision for how to do the crossmember, oil pan and exhaust manifold swap:

Option A: Try your best to get the manifold off in the cramped engine bay, if you break any bolts plan on getting an angle drill. Also you should plan on irritating bolts you cannot get to, and a sore back. Keep in mind you still have to swap the alternator (as well as extend the wiring harness) to the other side and swap the cross-member.

Option B: Remove the engine. Best done with the transmission attached.

For all too many reasons I decided on B and will have to recommend it to anyone attempting this conversion. It makes it far easier to change the manifold, crossmember and oil pan with the engine out of the car.

Take your time and go slowly, removing the engine is not very hard, but it can be if you build it up in your mind to be. You will need an engine hoist and recommended load leveler.

Removal of the crossmember is pretty simple. Unbolt the 4 nuts (two on either side) holding the crossmember to the frame rails, then remove the two bolts securing your front control arms to the crossmember. Next remove the A/C and PS line brackets that bolt to the front of the crossmember. The steering rack can be left in place once it is unbolted from the crossmember, but once you begin to lower the crossmember down it will need to be supported somehow. I just placed a length of 2x4 underneath it to hold it in place. The physical difference in the Z31 front crossmember is pictured blow. The top is NA and the bottom is Turbo, down is towards the front of the car:

The oil pan swap is needed only for the oil return fitting that came on turbo oil pans. You could install this type of return fitting on a NA oil pan, but purchasing a used turbo oil pan will usually work out to be cheaper anyway. You can obtain a replacement oil pan gasket (for 84-1/87 cars only, W-series VG30 uses RTV for a oil pan gasket) from the dealer for about $14, or from NAPA for about $8. Use small ratchet and extension to reach and loosen the small 10mm bolts that secure the pan to the engine block while the engine is still hooked on the hoist and off the ground. This will allow you to easily remove the pan from below with no obstruction. If your pan is the gasketed type, use RTV in the spots designated by the FSM to hold it in place during installation of the new oil pan.

BE AWARE of where your dipstick is when you put the pan on. Many people, myself included, have installed the pan with the dipstick in and not realized it until the new oil pan was completely installed. This causes the end of the dipstick to get caught, and the dipstick won't pull out. The only way to fix this is to remove the pan and make sure the dipstick is removed when you install the oil pan.

Locate and remove the small plug in the lower front on the drivers side of the engine block. This is where your turbo oil supply line is attached using two crush washers and a banjo bolt.

Now is also a very good time to swap to the turbo downpipe and remove the driveshaft. If you can't or didn't find a good used turbo downpipe, you can buy a very nice aftermarket replacement from Dave at <a href="http://www.certifiedmuffler.com">Certified Muffler</a>.

I just soaked the exhaust manifold studs in PB blaster for a few days and all the nuts came right off the studs. Unfortunately, two were already broken before I even pulled the engine out (not from me). The strange thing is I had no exhaust leak at all...

My parts were off a car from Michigan. Ok, if you don't live in Michigan I must explain something; any car that has taken 15 Michigan winters is a rust bucket. It must also leak oil like crazy... This would be in reference to the parts car I got my parts from. Oh well, enough complaining; here is a picture of the crossmember it took me two days to de-gunk with engine brite:

<img src="../images/turbo/crosspre.JPG" width="653" height="493">

Take note of the engine mounting bracket (for lack of a better word) on the right hand side in the picture. This is the reason you need to swap the crossmember and mount; it needs to clear the turbo. Somehow, under all that gunk and oil, it still managed to have rusty spots. I wire brushed and then coated the rust spots with POR, then coated the whole crossmember with spray truck bed liner.

Hey, look, transmission leaks are fun! (fun like the flu). Anyway, I decided to fix this while it was out.
<img src="../images/turbo/TRANS.JPG" width="653" height="493">

I also removed all the AC lines, next the nose comes off and I will remove the condensor. I am starting to get a nice pile of old parts going here. I weighed all this stuff and it was close to 90lbs, take into account the weight I put back on (turbo, manifold, etc) and I probably lost 30-40lbs from the front end.

<img src="../images/turbo/junk.JPG" width="572" height="432">
<img src="../images/turbo/turbosmpic.JPG" />

Did a bunch of stuff:

<li>All new engine coolant hoses (new clamps as well)
<li>New inner tie rods
<li>Rebuilt clutch slave cylinder
<li>Re-sealed transmission case
<li>Repainted and installed turbo front crossmember
<li>Installed turbo manifold
<li>Began de-undercoating the engine bay (thank you Ziebart)
<li>Cleaned engine up a little bit

This turned out to be one dirty project, the engine looks much better clean and with some fresh paint. Before and after:

<img src="../images/turbo/enbefore.JPG"> <img src="../images/turbo/enafter.JPG">

The crossmember is a little rusty, but I POR'd it, painted it and then gave it a coating of spray "Truck Bed Liner". Looks better to me, the engine bay is getting a little cleaning as well.

<img src="../images/turbo/bayprog.JPG">

This exhaust manifold was painted silver when I got it. Anyway, this may be handy to know... the turbo manifold does not use the same stud placement as the NA, go figure.

<img src="../images/turbo/manifold.jpg" width="640" height="480">

This is the exhaust elbow from hell. I have been soaking the bolts with PB blaster for about 2 weeks. The O2 sensor is stuck in quite well also.

I bought an exhaust manifold gasket set at napa and with my parts discount it was only about $14, not too bad. I coated the gasket with copper coat gasket compound and then installed it. While tightening down the last nut (and I did not overtighten it) the stud snapped off. So I had to take the manifold back off again, replace the stud, use my other gaskets (meant for the other side, good thing they are the same exact shape) to put the manifold back on. What a pain.

2 and a half weeks of PB blaster....

and the exhaust elbow's bolts were mostly still very very very stuck. I managed to get all but one out by using a 2 foot pry-bar. Then I had to get the cartridge out of the exhaust housing... read on.. Anyway this oxygen sensor was really stuck too. You can see what became of it, I had to hammer a 1MM undersize socket on it and then jump on the 2 foot pipe extension on my ratchet.

<img src="../images/turbo/sensor.JPG" width="503" height="370">

This turbo did not come from the 300ZX the parts car, nor out of thin air. The one I got from the parts car needed a rebuild, and on top of that three of the bolts broke off when removing the exhaust housing. This turbo came off my 1971 240Z (with a turbocharged L28 from a 280ZX). It has seen quite a few years of service but should serve me well. I swapped on the compressor housing and exhaust elbow from the 300ZX turbo's turbo.

<img src="../images/turbo/turbo.JPG" width="480" height="360">

I wish it had been that simple, this turbo was oriented for the 280ZXT, so I had to remove the cartridge from the compressor housing, which is about the biggest pain in the butt ever, luckily weeks of PB blaster helped all the bolts but one come out (that one broke, but I just left it). That was the easy part, after thousands of heat cycles the cartridges get stuck in the exhaust housing pretty darn well. I tried everything, even soaked it with PB blaster for a few weeks. Then my brother decided he would try and got it apart with just a few swings (I credit the PB blaster). Just in time for my new OEM oil line to arrive (complements of www.thespecshop.com), I mounted the turbo. Moral of the story: Use a trubo from a 300ZX!

<img src="../images/turbo/turboexhousing.JPG">

The oil pan swap was almost effortless and simple. I used some RTV to hold the gasket in place while I put the pan up into position. I cleaned the engine parts a little better, put everything together and she is ready save for two small issues. I'd like to wire in a factory detonation sensor for extra safety and I still have no downpipe. I extended the alternator wiring harness by splicing two harnesses together, then simply ran it in front of the crossmember (by the power steering lines) to the other side of the engine bay. I also replaced the spark plug wires because I found some Accel 8mm wires on ebay for $20 and my car had the factory wires on it, from 1984 (wow, Nissan plug wires last forever).

<img src="../images/turbo/altharness.JPG"> <img src="../images/turbo/enginedone.JPG">

So everything is assembled, I now have a turbocharged 9:1 compression engine, I just have to put it in the car and hook everything back up. I also replaced all vaccum hoses with new silicone hose, most of the old hoses are very brittle.

I had to remove the NA downpipe (hacksaw) and put the engine back in the car. Getting the engine back in was much easier with the front bumper cover and bumper removed. I have accumulated quite a pile of junk since the start of this project. I pulled out all the A/C lines and the condenser, the whole A/C system in the engine bay weighs about 50lbs.

Put the engine back in and hooked everything back up, Now in addition to having a turbocharged engine I also have an engine bay that I am not flat out embarassed to show to people. Putting the engine back in was easiest without the alternator, power steering pump, and A/C attached. The transmission mount is a pain to put back on, as are the hoses that run to and from the heater core. I also found it useful to remove the bumper as it lets you move the hoist more twards the rear of the car.

That's it, the conversion is done save for the exhaust (who needs a downpipe, cat, muffler and all that crap?) which I will get around to this spring. Thanks for reading this far. I hope this helped at least someone with questions and concerns, thats most of the reason why I spent the time to write it. As for the question of how much boost you can run, stock boost (6.8PSI) on a completely stock N/A engine was my limit. I was getting very slight detonation on 93 octane gas, with 10% octane booster additive (Toluene, from Sherwin Williams) it went away. You can install the turbo car's detonation sensor (and wire it in if you have a NA wiring harness), or retard the timing at the distributor. I backed out about a degree and had no issues on 93 octane with no additives. Every engine is different.

Race gas is awesome stuff. 110 octane leaded race gas is available at many places for under $4/gal. With a 50/50 mix with 93 octane I was able safely to boost 15PSI with no intercooler. I backed this off to 13PSI just to be safe on the fuel side of things. Then I ran it on a mustang chassies dyno (which are very accurate compared to most dynos, yet tend to read slightly low). I put down 240RWHP and 320RWTQ at 13PSI. Not bad, but it did not end there... it just keeps going. Check out the rest of this site for the other modifications.

<img src="../images/turbo/falltime.JPG" width="633" height="400">