Choosing the turbo and surrounding components
This decision will come down to a lot of personal factors. You have to balance price, availability, long term availability, compatible components and your goals.
You might be stoked you found a great deal on some oddball turbo locally but if you design your system around that will you be able to find a manifold and downpipe to go with it or a replacement if it fails? Will you be able to upgrade to a bigger turbo if that one no longer suits your goals or move down to a smaller turbo if you decide it's too big and laggy?
One concern is product compatibility.
It is wise to see what manifolds are available before looking at turbos too much as that will likely influence your options.
Before I made the made to order mani I am selling right now there were very few options especially for the transverse layout. Unless someone could do something custom themselves they would be limited to run a turbo that fit one of the very few manifolds available.
As of the writing of this I do make a manifold and will attach any flange for any turbo. I will also make a downpipe for any turbo. Some are still easier than others. If I can find a flange it's relatively cheap and easy. If I need to make a flange then it will take considerably more time and money. I do have a source for most big name flanges though.
This opens up options a lot and allows you to find the turbo that will work best for you.
The final question is how much money do you want to spend and how leading edge do you want to be?
Used turbos can save you a lot of money and for most of us will suit our goals just fine. From now on I will refer to these as JYD or junk yard dogs.
Buying a used turbo always has it's risks. You could put it in and get 100k miles out of it or you could blow the bearings out the first time you step on it. Careful buying and preferably careful first hand inspection can greatly increase your odds. There are many sites, pages and threads on inspecting a turbo so I won't get into that here. Another option is to rebuild the turbo or get it rebuilt.
The other option is to buy something nice and new off the shelf. This is very nice because the turbo is brand new and you can feel confidant it will last you a long time without trouble. Unfortunately many new turbos cost more than the cars we plan to stick them into. That can be a big pill to swallow.
There are also journal bearing turbos and ball bearing turbos. BB turbos are generally more expensive. They spin more freely and last a long time if treated right but if there is any issue you generally need to change out the whole bearing cartridge which is not cheap. For most of us these turbos don't benefit us enough to be worth the extra expense. This is especially true for people looking to run moderate levels of boost on a budget. The BB turbo can shave milliseconds off spool time and the bigger turbo and longer it takes to spool the more effect it will have. For anyone looking for less than 180 HP/liter and a turbo capable of producing that I don't feel that a BB turbo will be worth the extra cost unless you are seriously racing the car or in other situations where milliseconds do actually matter.
Picking a JYD
If you decide to go the route of a used turbo what one do you pick?
Of course you want one that will fit your current needs and goals. If you know exactly how you want your car to end up that may be enough. If you think you might want to grow at some point then you will want to find a line of turbos that use the same flanges so you don't have to change much if you get a bigger or smaller turbo. The most important part is the turbine side flanges for your manifold and downpipe. You spent good money for those parts and the last thing you want is to need to redesign your system and buy other parts or modify the ones you have.
Since the following talks a lot about MHI turbos I will go into brief detail on how they are sized and rated. There is a designation that starts with TD ie TD04, TD05, TD06. This tells you the size of the turbine wheel. Bigger number relates to a bigger wheel.
Next you will see something like 13T, 14B etc. This tells you the size of the compressor wheel.
The last thing you will hear people talking about is x cm turbine housing. This is the same thing as the A/R on other turbos. Instead of a ratio of the area to radius the mitsu turbos just refer to the area where the scroll begins. Bigger number means bigger surface area equaling a larger A/R.
There is much more info easily available on these turbos. One of the best places to start is here.
http://www.vfaq.com/index-main.htmlMitsubishi turbos have always been my go to. First off because I first got into boosted cars in the DSM scene and secondly because the turbos are very good units that fit the above requirements. There are quite a few turbos that all share the same flanges.
These range from some smaller TD04s like found on the 3000GT up through some TD06s capable of rather large numbers. There are also quite a lot of mix and match options easily available meaning you could play with your own combinations relatively easily. One downside of the DSMMHI flanged turbos is that most or the smaller options are getting older and harder to find. Turbos from the first and second gen eclipse, 3000GT and early Evos are all great turbos but also come off cars 18+ years old. This means they are going to get harder to find and generally with more time comes more wear. They are definitely not as plentiful as they were 10 years ago.
Unfortunately the Evo 4 reversed the direction of the turbo and went twin scroll. This means they are not compatible with any of the older turbos. They are also not compatible with much else smaller or bigger. The Evo 10 went back to the standard direction of rotation but still has the EVO twin scroll flange.
The DSM T25 is actually a Garrett turbo but has a DSM/MHI exhaust housing so it bolts up to the same mani and downpipe. It is a great turbo for those looking for quick spool and less than 250 hp. You do sacrifice a good bit of top end restricion for the quick spool but it Is often worth the trade. It is also the most common turbo I have seen run on 4As.
Subaru turbos have caught my eye recently because subies are so plentiful and I expect the turbos to be for some time. Many of them are also MHI turbos which I am fond of. Unfortunately they use a different turbine side. I am much less fond of the flange design on the subie turbos, especially the fact that they are only a three bolt flange to the mani. That said the subie TD04s are pretty common, pretty cheap and a pretty decent option for anyone looking for less than 250 HP. They are still a TD04 meaning if you found a healthy TD04 DSM turbine housing you could put it on a subie TD04 and run it on a DSM flanged mani. There are nowhere near the OEM variations that the MHI flanged turbos have but there should be a decent flow of used after market turbos coming out of the Subaru community meaning you could probably find some interesting options available. If you can find a Subie flanged TD05 or TD06 housing it also means you could run many of the other MHI turbos.
