Work in progress on this post need to work it out but don't want to type this up again
There are several options here as well going for a fully custom fabricated tubular twin scroll manifold to a fairly simple cast open port log manifold. Of course there are ebay options or other knock off/chinese options available. It is actually frightening how much power some of these kits are making fairly reliably. The line between you get what you pay for is starting to blur for me, but the downfall is that you never know when the line will blur one way or the other for a knockoff manifold and if and when it does your aftermarket support will be non existent. I went through three ebay headers on another car and finally went back to factory. I can't imagine they would last all that much longer when they have to support a heavy turbo and the pressures associated with them.
They key here is that you have to order for your head. The 2jz-gte and the 2jz-ge unfortunately do no share the same exhaust pattern thus you will be limited to the NA selection.
It will be up to you to decide how crazy you want to go here. Keep in mind that the turbo will sit awfully close to the passenger strut tower. That means you either want a manifold that will put the turbo rearward, upward, way forward etc. Having it smack in the middle and far out is going to be problematic. Also note that if you have a manifold that puts it too far rearward you are going to run into problems with routing the exhaust towards the trans tunnel.
If you were really on a budget and didn't need the hood I think I noticed you could flip the stock manifolds and do a front mount turbo.
Personally, ebay/knockoff was off the list for me, while tempting I just felt like it wasn't going to last. I don't think I need the boost response nor the precision from a twin scroll equal length manifold, so I could easily decide to use the cast stainless steel manifold with a lifetime warranty against cracking from treadstone. Even better I found one used from a forum member so it was a no brainer.
This isn't really a required part and you can clear the hood even with the cross over manifold, but I don't like picking up the intercooler piping on the same side and aesthetically it bothers me. The benefit of a front facing manifold are easier piping for intercooler, a chance to clean up all the boost/reference lines, and easier access to spark plugs.
You have a couple options here:
D tube with a flange: simplest option you can actually buy the D-tube and a cap and make it yourself or you can find one pre-made. Downfall here is that these usually bolt to the lower intake runner on the stock manifold that means there is always a possibility that you can loose hardware into your engine.
Stand alone aluminum manifold: these while being similar in design can vary in price from $500-$2500. These are straight replacements and will bolt onto the head. I have the cheaper one of these on my 7m. When I first started the car up it idled at 3000 rpm with the throttle body closed. I took it to a machine shop and it was found that the manifold flange was extremely warped, I believe he said he had to do 2 or 3 runs on the belt sander to even it out.
2jz-gte JDM intake: apparently it is possible to bolt with some minor modification a specific JDM 2jz-gte intake to the lower runners. This locates the intake much higher then the engine which might be problematic with how the hood is shaped, thus I am not sure this is a good fit.
Custom: Usually requires some use of the lower intake manifold but other then that it is pretty much fair game as to the shape. A competent welder with aluminum should be able to make one for you for a relatively good price.
Personally I went with the XS manifold to bolt to the lower intake runners. Dexter has them on his car and looks like it works without problems. He blazed the trail here on this application and I am just following. While I was tempted to do a stand alone aluminum manifold at $500 or more on top of the price of the D tube, I couldn't justify it. I may end up turning this into somewhat of a custom affair though and weld the D tube onto the lower intake runner to do away with the bolts and such. Time will tell.
This one is really going to be a doozy, I'll try and summarize it or provide more real world examples at a later date. Really it is up to the end user to decide, I will try and give a couple of general bits of information and more specific to the 2jz NA-T side of things. First off is some terminology. You have your compressor side which compresses the intake air. This side is connected via a shaft to a turbine or hot side which is bolted to the turbo manifold. Passing exhaust gasses spin the turbine/hot side and the shaft transfers this motion to the cold/compressor side.
The amount of air that a turbo will ultimately flow is determined by the speed that the center assembly moves and the size of the compressor side turbine. The thing is that while a small turbo might flow a lot of air if you spin it faster and faster once it dips out of its efficiency range the turbo will start heating up the air that it is compressing as well as start wearing out prematurely. These stats can be found via compressor maps as to the flow characterisitics at what pressure ratio how much flow is generated. Ideally you would want to be close to the max efficiency of the turbo at several rpm ranges. Being off the center island means a compromise of sorts it may mean that while you are in low boost the turbo is efficient, but at high boost you start moving off the center island. Ideally you want a proper sized turbo that will get you to your power levels with a little room above if needed.
This is the driven side the exhaust gasses are routed through this side and spin the turbine. As you can imagine this means quite a few things. A common number you see associated with hot sides is A/R without going into too much specifics this basically is the area ratio or the size of the housing in relation to the cross sectional area. A smaller A/R means that the turbo will spool up faster the housing is physically smaller and thus the gas being directed to it have more velocity, but on the flip side that small opening at the top end becomes a restriction you risk choking the turbo with the size restriction limiting the speed it can spin at. Ideally you want to spool up quickly while being able to hit your max targeted boost number. 0.63+ is recommended on an S256sx that spools around 3k RPM. Going up above 1.00 is not recommended as that will most likely make a very peaky turbo that will take a long time to spool and have very limited use.
So the main point is to be wary of recommendations people offer when browsing supra forums. You have to understand that their cars are much heavier, built with much higher rated components (diff/axle/transmission) and that they can cope with some of the downfalls of a large turbo. You also have to note that strangely enough a lot of people run bandaids on their setups, tricking stock ECU's with larger injectors and throttle bodies and such. A lot of people will also size turbos for future goals which given the stout bottom end can mean some really ludicrous numbers so beware.
For our chassis a large turbo is likely to hit harder and have a much higher chance of breaking some of our weaker components such as the stub axles or the axles so we want to size appropriately for our uses. A pretty good option is to actually look for recommendations on the L28ET for 350-400hp or so. The 2jz is slightly higher displacement which will mean it spools a little faster with the same A/R, or that it might choke a little bit more up top if the A/R is too small, so stepping up slightly will be fine. A 60 trim turbo will output way more then a stock chassis will need anyone recommendations of a turbo larger then that should be taken with caution.
Some turbos that seem like a good fit for 300-400hp with room to grow
Garrett T04E 57trim
Garrett GT3071R GT3076R (55mm inducer wheel)
Borg Warner S257SX-E
Borg Warner S256SX
As can be seen a 55-57mm inducer wheel will be fairly adequate for my personal goals, my friend has an S256sx on his 2.8L BMW motor and can't bleed enough exhaust through his 40mm waste gate to keep boost levels below 300hp.
I'll go into sizing later as this already seems verbose.
A note as to why turbo's cost as much as they do:
Building a turbo is a fairly involved process to get the housings for both the cold and hot side, requiring casting and cores for most turbos. Then precision balancing comes into play on the rotating assembly which spin at very high speed. The downfall with the knockoff offerings are the lack of quality control and frankly plain old oversight. Problems range from thin shaft material causing the rotating assembly to snap. Poorly machined surfaces which can cause premature bearing wear, and even drastic issues like glueing the compressor housing to the center assembly or flat out housings separating due to poor material composition. A turbo builder remarked that the demo pieces presented to him were great, but when they made a surprise visit to the factory in china they found much lower quality material was being used. They had them destroy these low quality housings on the spot, but a factory could easily divert these to another seller to be resold on knock off turbos.
This is bound to come up, and having looked into what is available here are my thoughts on the matter.
For some sellers it does not matter for them what they sell. There have been reports of people who have taken apart large T4 size turbos and find small T25 size shafts connecting the impeller these would essentially work until they saw load and the shaft would shear almost instantly. Other reports of weak cast material for the compressor and turbine housing means fractures are only a matter of time. Other reports find that the balance is off or the seals are leaking. Those are reports from no name ebay turbos.
However, it seems like if you do your searching you can find some of these turbo's and expect some life expectancy out of them. VS racing and CX racing are two companies that have embraced the Ebay Turbo and in some cases making decent power out of them fairly reliably. What you should expect is that life expectancy will be really low, factor in about 10,000 miles before they need inspection or replacement. Given the price of some of these turbo's that may be an easy choice for someone to make. Keep in mind the downfalls: a really blown seal can ignite and cause a run away situation, a sudden loss of boost pressure can cause a massive rich condition, and a blown housing can cause incorrect signals to the o2 sensor which can lean out the injectors. If those situations are acceptable trade offs for saving 1/2 the price of the turbo it will be up to the purchaser to decide.
Turbo add ons:
To combat the problem of boost thresholds being high with a big turbo, but a lack of bottom end with a small turbo, Toyota opted to go with a sequential turbo setup from the factory. This system closes off one turbo while under a certain boost threshold funneling all the gas to one turbine (acting as a small A/R) and when it gets to a certain pressure it opens the second turbo essentially doubling the capacity allowing the now more abundant gasses to spin both turbos. While this works it does mean a more complicated system with two turbos two sets of oil lines, two water lines and so on. Given modern non water cooled turbos and things such as twin scroll and ball bearings as well as quick spool valves you can get very responsive single turbos that still deliver on the top end.
Quick spool valve:
A common item in the supra community is the quick spool valve with an open setup. It basically behaves like the old sequential setup, but instead of shutting down a second turbo it shuts off half of the exhaust flow to the turbo. Thus the same theory applies, more speed through the smaller opening equals quicker spool, at a certain point the valve is then opened and the top end can be maintained. Thus with items like these people who run 2jz's tend to run fairly large sized turbos, much more then any sane person really needs in our cars.
On the flip side is that these large turbos can build a large amount of boost. The key here is that as your engine speeds up it consumes more air so to maintain this boost pressure the turbo must move more CFM, this is easy as the more air consumed the more exhaust gets put out to spin the turbine, but this relation is not linear! That means if all the exhaust is put through the hot side you will see boost levels climb until the turbine is maxed out or things start to wear and break. The waste gate serves to bleed off exhaust thus diverting some of the gas that has to flow through the turbine thus controlling boost. Turbo sizing is important here. If you pick a large turbo, but decide to run low amounts of boost a lot of exhaust gas has to be diverted through the waste gate. Even large waste gates cannot deal with excess exhaust, which means a second one may have to be added. At $300ish a pop it is not worth it. Size your turbo correctly for your application to avoid this. An incorrectly sized waste gate (as in too small) will cause boost creep as even with the waste gate fully open it cannot divert enough exhaust to slow down the turbine speed.
Your main options are going to be Tial and Turbosmart. Other brands exist, but as far as I am concerned these are going to be safe reliable bets with good customer service.
Be wary of knock off waste gates, these control aspects of your turbo. Best case scenario they break open and the turbo never gets up to desired pressure. Worse case scenario they break closed and all the exhaust diverts to your turbo which if you oversized it or your map can't compensate for a boost spike means at best a blown off coupler at worse destroying your turbo and engine.
Edited by seattlejester, 14 November 2016 - 02:10 PM.