RB26 Engine Turbo Swap & External Overhaul
This guide picks up where the Pulling the RB26 Engine walk-through left off. Having just separated the transmission from the engine, we now look to remove the old turbos and then set up the new ones. There is a lot of patience needed to do this, as there are a many fragile parts. It does take quite some time to complete this, maybe even a day or two if its your first time.
|Starting Engine Overhaul and Turbo Swap|
First thing to do is remove any intake piping that may still be attached, put it off to the side. There is an array of metal and vacuum hoses just above the heat shields, and it wraps around the back-side of the engine, remember to label each line that you disconnect. There is also the water feed line, which spans the length of both heat shields, these lines have been heat cycled for 20 years - and unless you plan to replace with stainless steel braided lines (as I have done) - then you need to be very careful when removing the lines or they will crack, as in the picture below.
|Fragile and Broken old Water lines|
At this point, you need to disconnect each turbos various connections, thankfully they are duplicate systems of each other front to back, so one explanation suits both turbos, just do each step at the same time on both turbos. There are two banjo bolts on the outer side of the turbo housing, one is the oil feed line and the other is a water line. The banjo bolts are sealed using copper crush washers and after 20 years of heat cycles you can bet they're going to require some elbow grease to free up, as before use caution or you risk damaging the lines and causing a leak later on. After the 2 hard lines on the out side, there is a water feed line just above, removing this takes some patience and steady hands to not destroy the line, so take it slow.
|Twin Turbo Exhaust Manifolds and Turbos WasteGates|
The exhaust manifolds have 6 nuts each, remove the exhaust manifolds to change the gaskets, otherwise they can stay in place if the goal is only a turbo swap. In the picture below, these are the turbos as they came off the manifolds. At this point, unless you've purchased new studs from for new turbos, you'll have to re-use the old ones, which is fine, but it can be difficult to remove old studs without damaging the threads. If you Break or Snap an Exhaust or Intake Manifold Studd, here's a Trick to Repair the Damage. First remove the 5 nuts holding the dump pipes to the turbo exhaust, now you have access to 4 studs on each flange, and 5 studs on each outlet. The best way to remove them is to let them soak in WD40 or liquid wrench, and then use some vice grips very carefully, tightened onto the part at the base of the stud that doesn't have threads on it.
Then, once all 18 studs are free it's just a matter of screwing them, short side first, into the new turbos.
Now to install the new dump pipes, mine are a pair of divided stainless steel ones, made by RS*R. The open nut in the backside of the outlet pipes are for the oxygen sensors, be careful when installing the sensors, and make sure to put the one from the front turbo, in the new front dump, and the one from the old rear turbo, in the new rear turbo's dump pipe, if not the ECU will confuse the first 3 cylinders with the back 3 cylinders and cause really bad mis-fires.
Never re-use old gaskets, and there is a trick to installing the new exhaust gasket that gets sandwhiched in between the dump pipe and the exhaust housing. Use some high temperature gasket maker and spread a thin bead on both mating surfaces and both side of the gasket, a very thin line, this will make 100% sure of an effective gasket seal.
Now onto the exhaust flange..., it's the same procedure as before with the studs, tighten them up as best you can using the vice grips on the non-threaded part. You can also put some tape over the 2 inlets and 2 outlets to make sure nothing falls into the blades of the impeller and exducer.
Then the 2 nuts will line up and everything should bolt on without issue, one nut on either side. Remember when ever installing paper gaskets, to first spray both sides with Permatex copper gasket spray, and allow it to become sticky and tacky, that will ensure the best seal for paper gaskets.
Now comes the part where we transfer the oil and water hard lines onto the new housings. These are needed, as they wrap around from the backside of the turbos and make it much easier to connect the new braided water and oil lines, keep in mind not to tighten up these 2 outer bolts until the lines are hooked up since the copper crush washers are one time use only!
At this point we can now install the oxygen sensors into the bungs, be sure to respect which one is for the front turbo and which one is for the rear.Also, it's a good idea to count the threads on each arm of the actuator waste gates and make sure they are equal as they're quite hard to adjust after the engine is installed.
Here you can see both turbos all done up, ready to be bolted back onto the engine. Sometimes you can have poor power delivery due to "Turbo Shuffle" - take a look at this Explanation Guide on how to handle Twin Turbo Shuffle.
Back to the engine... With the new turbos all finished and ready to go on, now we address the engine bits. Starting on the exhaust side, removal of the exhaust manifolds is straight forward, theres 6 nuts holding each one on, we remove these to replace the gaskets, but if you don't have new gaskets ready, then don't remove the manifolds as you cannot re-use gaskets, they'll never seal a second time.
Once the manifolds are off, you need to clean both surfaces, and be very careful that nothing goes into the valve train while cleaning. It's also a good opportunity to have a look inside at the valves and just see if anything looks out of place, or if there's oil leaking from a stem seal. If all is good, then we prepare the new gasket by spreading a very thin layer of Permatex RVT high temp gasket maker over both sides of the gasket, line it up, and slide it over the studs. Then line up the manifold and tighten the nuts finger tight. Check the Nissan service manual for actual torque values, as over-tightening exhaust manifold nuts and studs will lead to a broken stud, which can be difficult to remove from an aluminum head with out doing serious damage.
Now we're ready to install the new turbo assemblies, but before doing so I had to clean up the outlet piping. It seems 20 years of use had caused a thick greasy layer to form on the inside and outside of the pipes, so using a Dremel wire brush wheel attachment I made around the pipes like a Roto-Rooter plumber.
These pipes are for the compressor inlets, the cleaner we can get these, the less we risk wearing the turbine blades out from inhaling particulate matter. I washed them periodically between brushing in warm water with degreaser until they finally started to show some shine.
I smoothed out the finish with finer grit sand paper, until I achieved a dull shine finish, topping it off with a series of high-temp clear coat gloss passes, so the air would flow as smooth as possible and the finish would keep clean.
I did the same thing for the little outlet adapters as well, I figured if its going to have air flowing through it, I should try to make it as smooth and clean as possible, you can see the type of finish I was able to get.
Now its time to install the turbos, there is a specific order in which to do this, because as you can probably guess, if you installed the rear turbo first, you will have a hard time installing the forward turbo second. So we start first with the exhaust manifold to turbo flange studs and nuts, there are 4 on each turbo, remember to prepare the gasket again with Permatex, and tighten the nuts down according to the proper torque spec listed in the Nissan Service Manual, doing the forward turbo first.
Before bolting up the second turbo, its a good idea to install the rear turbos' compressor inlet pipe and gasket, since it is secured with 2 Allen bolts, these are near impossible to get tight afterwards if you don't do it now. for paper gasket you can prepare the gasket with Permatex copper spray. Now with both turbos securely held by the exhaust manifolds, you'll want to install the lower support brackets so they don't strain the studs too much longer. Then you can bolt on the heat shields, simple 3 nuts on each. Then we hook up the oil and water feed lines to the turbos. Be sure to get a perfect seal on the crush washers, and don't forget about the oil restrictors which are necessary when you move from a journal or thrust bearing turbo to a ball bearing one, they only need to be placed in-line on each oil feed line. The oil feed lines can then tee into the block adapter which is situated directly in the lower middle portion of the block with a banjo bolt.
The water feed lines can be bolted into the turbos now and just left to hang freely for now. The water return lines should also be connected at this point as well, they go from the turbos to the rear banjo bolt on the block. The turbo oil drains are easy enough to connect now as well, they use a simple small section of rubber hose and hose clamps, there won't be very much oil flowing through these at all, since we use restrictors we can expect maybe a trickle of oil in these return pipes, and they connect to the adapters a few inches below each turbo respectively.
Now it's starting to really look like a twin turbo engine, all the lines should be connected at both ends, except for the water feed lines. The compressor inlets and outlets can now be installed.
Since I destroyed my original water feed hard lines I had to have new braided lines custom made from Tuboquip here in Montreal, the end result worked out in my favor anyways, the custom design made it very easy to finish up the water lines. I connected the front feed from the upper rad hose neck on the block, wrapped around the front and then into a double tee section, basically a one to three split. 2 feeds would go to each turbo, and the third connects to the rear water line adapter, which actually wraps around the backside of the engine. The braided lines make working on the engine a lot easier and looks a lot better too.
At this point we can now begin to snap on all the other various tubes and pipework. It's really straight forward at this point, since each pipe can physically only fit in on place, looking at this picture below is all thats needed to see how it all hooks up. It's important to keep track of the vacuum lines here though, I was using red silicone lines with metal hose clamps, but as I later learned during the year, these are very prone to cracking and splitting, resulting in a boost leak, and in my case, uncontrolled boost pressure!
The very best vacuum lines are actually just standard rubber OEM lines, you can prepare them by spraying each connection with WD40 or hairspray, which when dry creates a bit of a seal and to really secure them over the nipples you should use a zip tie on each end. It's not necessary, but that extra added redundant security is worth the minimal extra work and cost.
Moving away from the exhaust side, to address the intake side its a good idea to remove the fuel rail and inspect all the injectors for signs of leaking, I took some of mine to a professional fuel injector cleaning specialist and he explained everything, even proving that having injectors cleaned results in major performance increases - Check out the complete write up here: Fuel Injector cleaning really worth it?
Having a look at the under-side of the intake manifold, it looks like a real mess of water and vacuum lines. These lines under the manifold are renowned for bursting at the worst possible times, and to make a bad situation worse, if it happens while the engine is in the car, it is near impossible to replace them without removing the intake manifold, so as long as the engine is out, we address these aging lines.
I'd ordered a complete silicone water hose kit, to replace each hose. The process does take some time, My method was simple though. I took a new silicone line from the package, and lined it up against its aging partner to make sure I had the correct one, same shape and same size. One by one I used a knife to cut the old hose off, clean up the nipple/adapter with some sand paper and solvent, a shot of WD40 and forcing the new hose onto the adapter - some of them require some serious elbow grease. Make certain you don't forget the install hose clamps at either end of each hose, with out these clamps you risk springing a leak. When all the hoses are finished it really starts to look like a fresh motor now.
Here we can now move onto the vacuum lines, again I did mine using red silicone, but I suggest using standard OEM rubber lines, they're far better. (currently I've already replaced mine back to the rubber ones). For demonstration purposes, the red and blue makes it very easy to see which lines are air, and which are water, so at least it serves as a good informative picture.
If your going to be installing an oil block adapter for an external oil cooler and/or filter relocation, now is the best time to do so. Don't use steel wrenches on any Earl's anodized fittings as you will damage the fittings, it's best to do them finger tight, and then use a rag to and an adjustable wrench to tighten them down. Don't forget to spread a little bit of engine oil on the rubber O-ring seal for the block adapter or it will leak on first start up.
Everything is now essentially complete, I didn't change the gasket on the intake manifold because I will be replacing it at a later point in time when I bring the manifold in for powder coating. I also left AACV valve alone because I noticed on mine the idle set screw was held in place with an epoxy, this is something Nissan service technicians were doing in Japan, they set the idle screw and glued it in place so that no one would mess with it, I've never had an idle problem before, and still to this day have not.
To continue to the next step, head over to: How-To Reinstall the RB26 Engine.
Have you ever wondered how the Skyline motor stacks up against the Supra motor? Drifted.com has a great comparison article here: RB26 Vs 2JZ.