mclarenno9

A lot of interesting 951 build theads have been popping up on this forum in the past year or two. While certainly not groundbreaking, I figure people will enjoy seeing in detail the work required to fit a more modern turbo to one of our machines. Hopefully I can add some perspective to those who are debating going this route, and will aim to answer any questions pertaining to my build. First, a little background...

After many years of pushing the stock (hurting) 26/6 turbo, I felt it was time for an upgrade. My goal was 350 rwhp on 93 at 17-18 psi with negligible lag (i.e. 1 bar @ ~3100 or less in 4th). Over the years I had gathered and installed all of the supporting mods to allow me to upgrade once and do it right. These included LSD, proper MAF/injectors and software, WBO2, Tial 38mm WG, etc. Since I knew the stock clutch would not last very long at my HP goal (and I had quite a few nagging oil/exhaust leaks), I made the choice to pull the engine to do the work. With 171k miles on the engine, I figured a complete reseal with rings/bearings was in order anyway. Sure enough, somewhere along the line, "project creep" set in and I added a few other things, such as a larger oil cooler, oil pan baffle/crankscraper, hi-torque starter, lightweight flywheel, catch can, engine mounts, headers, an alternator/battery cable upgrade, and even got some head work done. In the process I deleted the A/C and cruise control (both of which were unoperable). "While I was in there," I figured I would replace every sensor and hose as well. Not one for being content with dirty hardware and equipment, I spent countless hours bead-blasting / painting, and cleaning various parts along the way. New fasteners were ordered for anything in the engine bay as well.

I will be updating this thread as time allows. Here are a few before/in progress pics of the engine pull and short block teardown/rebuild:

mclarenno9

Knowing that I have plans to eventually track this car, I figured now was a good time to add a little extra insurance in the way of a crank scraper and the oil pan baffle / pickup ring mods. I sent the oil pan to LR as I wasn't yet confident in my welding skills on aluminum (and I didn't think I'd have enough amps with my setup for the thickness). Moreover, I assumed welding on a cast piece which has had oil sitting/seeping into it for years wouldn't be a great experience either! Turnaround time was very quick and I was pleased with the result.

The crank scraper took a bit of work to file / fit right, but all in all not a bad experience. Grinding was only necessary in the cutouts for the crank and rods, and not along the outer edge of the scraper, where it can potentially hit the pan (YMMV). I test fit the pan with head washers used as standoffs, mimicking the thickness of the metal sleeves in the oil pan gasket (in reality the washers were slightly thinner). I wanted to ensure I would be able to fully compress the
gasket when I went to install the pan. Hopefully the scraper will keep more oil in the sump, where it belongs...

mclarenno9

I fought the urge to go straight bolt-on with regards to turbo choice. I wanted to ensure that I never had any regrets about the setup, what-if's, etc once it was all said and done. Of course I knew it would require some fabrication, but once the parts were in hand I figured it would be sufficient motivation for me to learn and get on with it!

After much deliberation, I went with a GT3076R with the Tial SS V-band turbine housing, 0.63 A/R. I used the standard 4" anti-surge compressor housing, which led me to go with the Nissan Quest alternator for extra clearance (more on this later). In the end, with the deletion of the A/C, alternator selection would not have mattered anyway.

I used the CEP turbo mount, as I didn't want to have to hack up the stock mount and worry about leaks (Ok, so I skipped a fab opportunity here!). The mount is a nice piece, for sure. It has a groove machined into the pedestal to accept an OEM o-ring to create the seal for the oil drain (same one used on the aux. coolant t-stat elbow and oil filter housing console, P/N 999.707.043.40). No modifications to the throttle body or intake were necessary to fit the turbo. I've included pictures below showing the clearances. Yes, there was room for a silicone hose and clamp between the compressor inlet!

mclarenno9

Next I will tackle the plumbing issues for the oil drain. This needs to be routed carefully to ensure it will not interfere with the the steering shaft. What makes doing this oil drain a huge PITA is that you have that giant banjo bolt to deal with. I chose to cut the old hose / barb off of the banjo and weld on a -12 AN (steel) fitting. Make sure that you orient the flats on the bung correctly during welding such that they will not hit the pan when the banjo is tightened down, otherwise you will definitely have leaks (credit to DDP for the heads-up!). Try to keep the hoses as tight to the oil pan as possible when routing them.

The CEP turbo mount came with an -8 AN fitting on it already, so I chose to keep that size for the drain line (up until the Y-fitting). I used nylon braided hose as it is easier to bend and work with (fairly tight bends are required here). I also utilized the silicone replacement hose from LR meant to replace the rubber elbow that connects the vent line to the AOS. From that I used a barbed -> AN fitting. The rest should be self-explanatory from the pictures. Finally, to combat the radiant heat from the turbo and exhaust, I used some protective sleeving on the nylon hoses for good measure.

The parts list was as follows (some Earl's PN's included):

1 - AOS to Turbo Drain 90 Deg Silicone Hose (LR)
3' - Thermo-Tec Thermo Sleeve (5/8"-1" OD range)
1 - Y-Fitting -12AN by -8AN by -8AN (Magnaflow MP-6228-B)
1 - 1/2" Barb to -8AN Fitting (Fragola)
3' - Earls Pro-Lite 350 Nylon Braided -8AN Hose (350308ERL)
4 - Straight -8AN Swivel Fitting (AT800108ERL)
1 - 45 Degree -12AN F-F Swivel Coupling
1 - Weld-In -12AN Fitting (Steel) (967112ERL)

A note about AN fittings... Yes, it's generally desirable to use the same brand of fittings on either side of the joint whenever possible to ensure proper sealing at the flare face. In this application there is virtually no pressure so it is not as vital.

BTW, Pace Performance seemed to have the best prices on Earl's fittings and hoses. (No affiliation!)

mclarenno9

The oil supply line is fairly straightforward. The threads in the balance shaft cover are M14x1.5. Get from point A to B basically. If nothing else please make sure you use the proper restrictor with a turbo such as this! I used a -4 AN sized 0.035" orifice fitting (can be found at ATP turbo). Since the turbo oil feed location on the 951 is not directly off of the filter, I chose to add an inline filter for the supply to the turbo. The ball bearing turbos hold very tight tolerances so I felt it was justified. Dave at CEP hooked me up with a filter and -4 AN line setup which had enough length to mount it virtually anywhere. A nice space for the filter presented itself once I deleted the cruise control. I welded up a small bracket to mount the filter, as shown in the pics below.

The coolant supply line seems easy, but can be a bit tricky to source proper parts for. It took me two tries to get this one right. I started by using AN adapters and a 45 deg. fitting, but it ended up hitting the compressor housing because it did not protrude far enough (it's hard to find dimensional dwgs of AN fittings). In the end I chose to do something similar to the factory setup; Adapter -> barbed fitting -> 90 deg rubber hose (w/ shielding) -> aux. coolant pump. Since the center section of the Garrett DBB turbos is so short it makes tool access difficult. Some careful thought must be given during selection of parts to account for this fact. I used the following:

1 - M14x1.5 to 1/4" NPT Steel Adapter (McMaster - 4936K155)
1 - 1/4 NPT to 1/2" Hose Barb Steel Fitting (McMaster - 5350K79)
1 - Alum. Crush Ring for adapter (900.123.007.30 - Replace the buna o-ring on the adapter with this)
1 - Gates 28460 1/2" x 90 Deg. Heater Hose (eBay - Note: This is a very tight fit over the coolant pump. It is better to slide it over the pump nipple first, then install onto the car)

Last but not least, the coolant outlet debacle. Paully detailed a great method for dealing with this line, and I basically did the same thing, however instead of cutting and threading the stock tree piece, I welded an AN bung onto it. I also needed to use the lower profile coolant temp switch due to interference with the intake. Parts list:

1 - M14x1.5 to -8AN Straight Adapter (Fragola)
1 - Weld-In -8AN Fitting (Steel) (Fragola)
1 - 90 Degree -8AN F-F Swivel Coupling (AT935108ERL)
1 - Alum. Crush Ring for adapter (900.123.007.30)
1 - NISSAN 280ZX 300ZX Radiator Fan Switch 81-84 TS193 (eBay)

mclarenno9

A big (mental) hurdle was modifying the crossover pipe to fit the new turbo. It goes without saying that this is much easier done on a stand rather than with the engine in the car, but as shown by others (Paully), it can be done. The header/crossover system is a pretty stout assembly, so alignment is critical (esp. with v-bands) in preventing leaks. Things tend to shift and warp a lot during welding if you are not careful, especially stainless since it holds heat in the material a long time. Be careful, use many tacks, measure twice, cut once, etc. I cannot stress this enough. Good fit up is very important when welding pipes and the little extra time you take to reshape or trim a piece when it isn't fitting quite right will pay off in the end. I ended up mocking up the pieces to weld to the crossover only to switch to LR headers later on because I didn't trust my repaired stockers. The slight differences in the header geometry meant that I had to redo one of the pieces. I am glad I took the time to do so. The end goal is to minimize the built-in stress of the assembled header/xover assembly.

I water tested my original crossover only to find it was cracked pretty badly at the merge collector. After trying to repair the crack, somewhat unsuccessfully, I sourced a good condition replacement crossover from Lart to butcher instead! First, I bolted up the crossover with the turbo mounted to get an idea of how far off it would be. As you can see from the pics below it was pretty close.

Start by making a cut to get rid of the old flange and first elbow, then work your way back from there. I tacked the v-band flange to a 2.5" CLR 90 degree bend, OD of 2.125" 16 GA 304 SS from Woolf Fabrication (it's an odd size). I then clamped that to the turbo and spun it to align it roughly. There is quite a bit of trial and error here, as you would assume. I believe the bend probably ended up being about 85 degrees. Always try to align bends so that they end up tangent to the straight sections and avoid mitre joints if possible (square cuts go a long way here). After you have the first elbow where you like it, you can make another cut in the crossover and take a bit more off. I saw no reason go any further than where I did. This way I kept the O2 bung and insulation as well. I also knew that it would clear the steering shaft since I had not changed the geometry all that much. After cutting the xover the second time, I used a straight piece which was actually one of the legs off of the elbow. This piece is the "keystone" and can be a PITA to fit. This is the one that takes the most time (and is the one I had to remake when I switched headers).

For materials, all you need is that one mandrel bend I spoke of earlier, and a suitable flange. The higher the grade of stainless, the better. I'm not sure what grade the factory crossover is but it welded fine with 308 rods (I use TIG). I mentioned the piece I used was 304SS; if you could find a similar bend in 316 or 321 or even 347, that would be preferrable (just make sure you are changing your filler to suit). As always with stainless tubing, make sure you back purge when finish welding to prevent heavy oxidation on the inside of the pipe (see pic for my crazy arrangement).

Once you have the pieces cut and fitted, tack them together and trial fit the xover (using more tacks here will help prevent warping issues later). Make damn sure the fitment and alignment is good before you go finish-welding things! Always stop and check fitment where possible to mitigate rework. I welded my pipes on the bench, because I didn't feel like moving my rig over to where my engine stand was. It would have made things a lot easier to tack and weld it up as it was bolted in place. If you do go that route, please make sure you leave everything clamped / bolted until it has time to cool. Also, be sure you place your ground close to where you are welding, and not on the center section of the turbo, for instance!

If you are new to welding, just practice a bunch first. This whole project was my first real foray into welding. I practiced by making a bunch of heat shields and brackets out of stainless scrap.

Oh, and as a finishing touch, I sent the crossover and LR headers to Swain Tech for application of their White Lightning ceramic coating...

mclarenno9

The downpipe is a bit easier to execute, however the engine really needs to be in the car to fabricate it. I made the decision to try and make the majority of it with the engine on the stand. To do this, I bolted the downpipe up to the block and made a crappy jig of sorts to act as the "finish line", if you will (it was also good welding practice). With this I was able to cut and fit some of the more tricky bends with clear sightlines. As many of you probably know, the exhaust in this area of the car is packaged very tightly. Shooting the gap between the oil pan, crossover, body, and caster block mount can be tricky. I felt that the jig would help me get close enough, and it did. If you plan to build the whole thing in the car, just build from the test pipe flange upwards.

For any exhaust work post-turbo 304 grade SS will suffice. I wouldn't waste my money on anything more. I ended up using 3" 16 GA tube, a variety of 3" and 4.5" CLR bends. You need the tight 3" CLR bend right at the exit of the turbine to clear the intake mount/brace. Finding a tight radius bend can be hard; I got that from Woolf Fabrication as well. You can use the legs off of the bends for straight pieces if you need them. For flanges, it is up to you. As you will read below, I needed to change the flange on my test pipe anyway, so I could use anything I wanted.

My original plan was to just make a full 3" downpipe that would mate up to my LR 3" exhaust. This would would require me cutting off the end of the LR piece and welding on a 3" dia. section and flange, since it necks down to 2.5" to accept the factory downpipe. Once the engine was in the car and I started looking around I remembered how much I hated the location of the factory flange. You'll see the downpipe is much longer than stock and positions the joint in a more accessible location now. Due to its length however it must be snaked out of the car from the bottom (if the turbo is to remain on).

I wanted v-band flanges at the connection from the downpipe to the test pipe as well, but my first attempt at welding them did not go so well (i.e. they warped badly because I was impatient). I went back to using traditional 3-bolt flanges and went as far as bolting them down to a 1/2" thick piece of aluminum while welding to eliminate the distortion (which was a godsend btw). To finish it off, I wrapped the pipe with DEI Titanium Exhaust Wrap (1" x ~35') to keep the heat out of the engine bay. I also fabricated a heat shield to protect the oil lines and intake (a practice piece as well ).

The last two pics show the hacked up LR pipe which I modified to bolt up to the downpipe. I was not quite happy with the result once it was on the car (and didn't really like the idea of the bimetallic weld; SS -> CS). I decided to go a different route, to say the least. More info in the next post...

mclarenno9

I'm a bit of a perfectionist and the hack job shown in the previous two pictures was not going to cut it for this project. It didn't fit quite right and wasn't packaged tight enough to the bottom of the car for my liking. It is hard to try and work between two fixed points, which is what I was trying to do. I knew it would be much easier to start at the downpipe and work all the way back with something new. Other aspects of my current exhaust system that I did not like were the heavy and cumbersome wastegate arrangement, various slip fit joints and clamps, and the fact that it wasn't stainless steel.

So, I decided to build an entire 304SS exhaust system for the car, with wastegate tie-in (not a fan of the dump). I also wanted the correct Tial 38mm flanges on the exhaust to get rid of the current clunky setup. I made some measurements of the current setup and put together the following shopping list (with exact eBay search terms, if applicable):

1 - Tial 35mm / 38mm External Wastegate Flange & Gasket Set (eBay)
2 - 3" Exhaust 3 Holes Stainless Steel Flanges w/ GSK (eBay)
1 - 2" Torctite Stainless Exhaust Band Clamp Step Clamp (eBay)
1 - O2 Oxygen Sensor Weld Bung SUS 304 Stainless Steel Exhaust (eBay)
8' - 3" 16 GA Straight Tubing (Ace Stainless Supply)
2' - 2" 16 GA Straight Tubing (Ace Stainless Supply)
1 - 2" to 1.5" SS Concentric Reducer (Ace Stainless Supply)
4 - 3" 45 Deg. 16 GA SS Elbow (Ace Stainless Supply)
1 - 2" 45 Deg. 16 GA SS Elbow (Ace Stainless Supply)
1 - 2" 90 Deg. 16 GA SS Elbow (Ace Stainless Supply)

The 3.5" tip and Borla 40944 muffler were stolen off of my original LR exhaust system. To do this you will also need some stainless plate/sheet to make the brackets (probably 12 GA or thicker, ~0.125" would be perfect). For the wastegate tie-in, I actually used 2.125" OD tubing on the test pipe side. This was a leg and some of the bend I had from one of the pieces for the crossover work I did. It was almost a perfect slip fit with the 2" tubing; very little expanding was needed (which was good because it is pretty hard to expand SS tubing with the conventional Autozone rental tool!).

Realistically, if you buy just the right amount, you could do this for about $250 in materials, plus a muffler and tip. This was a ton of work however, and I wouldn't expect many would feel the need to do this. In all honesty I guess I was having too much fun at this point!

Some invaluable tools for work like this include a 4.5" angle grinder, a nice chop saw, and large belt/disc sander. If you have a quality chop saw (or even better, a band saw) that can make square cuts you are good to go without the sander. I used a 12" disc sander to square up cuts and finish the ends of any small pieces I had to cut with the angle grinder. It all goes back to eliminating the gaps in the fit-up.

As for how I did it, the pictures should tell pretty much the whole story... I cut the stock WG flange off of the little 90 elbow coming from the crossover and welded on a new Tial flange to start. I tried to position the wastegate in a way that would allow for easy servicing of the lines. The outlet flange is also easily accessible. The flange can be unbolted and the tie-in pipe can be rotated down out of the way so the whole exhaust can come out with no fuss.

By far the hardest part of this was doing the tie-in for the wastegate. I knew coping the 2" pipe to fit the main exhaust would be very difficult so I used a cardboard tube of equal diameter that I shaped to fit correctly. I then copied the shape onto the pipe which got me very close. A few adjustments later and it was done. Running an open dump will save you many hours here, if you choose to go that route!

mclarenno9

For my clutch needs I went straight to Southbend. Based on the positive experiences of others, I chose to go with their Feramic disc option for driveability and torque-holding capacity. One thing I did not want with the new clutch disc was to have the six small springs on back of the hub, which are notorious for breaking (two of mine were missing). They were able to build a new "cup" style disc for me with only the 4 major springs. I also had my pressure plate rebuilt by them. Once rebuilt, it was tested and found to have 2100 lbs of clamping force, which I was told was slightly better than an OEM Sachs PP. With the Feramic disc, they stated this combo should hold 480 ftlbs or more. I paired these up with a Fidanza Aluminum flywheel which I had balanced first (as most suggest doing). And what clutch job would be complete without new speed and reference sensors! Like most people I used the BMW part number (0261210002) as they were much cheaper. I also modified the bell housing at this point so that I could easily gap the sensors.

At the time of this post I have only driven the car once, for about 60 miles. Initial impressions were that the pedal effort is the same as stock, and the modulation is pretty decent as well. Obviously with the new lightweight flywheel I am needing to give it more revs to get going from a dead stop. The clutch itself is definitely a bit more grabby. I don't want to say it is purely on or off, but just that there is a tighter range in which you are able to modulate it. Once rolling you won't notice this effect, like when changing gears for instance. Oh, and there is a slight amount of chatter in reverse, but nothing embarassing. Southbend recommends a break-in period of 750 miles, over which the characteristics may change slightly (?), but this is the only data point I have at the moment.

refresh951

Steve,

Thanks so much for sharing your approach here! Very impressive attention to detail. I am looking forward to seeing more details as I am in the midst of installing GT35R now.

mudbuddha

Nice work. Like them Carrera classics...

V2Rocket

Howabout putting a high-temperature clear-coat on the block? Would make cleaning a breeze.

86 951 Driver

I would love to do something like this, but I assume it takes a decent amount of cash and some more knowledge than I would have.

kghaas

Those pics are so shiny its hard to look at!
Good job!

looking forvward to seeing the crossover cuts and welds.

333pg333

Nice write up Steve. Great to start with all clean parts. You're going to love that turbo for sure. You'll need to modify parts of the exhaust system but you know this. Keep the updates coming.