yoshimitsuspeed

The 20V is far superior to the 16v heads. You would have to spend a ton of time and money to get the 16v close to a 20v. You might be able at some point get a 16v to outperform a stock 20v head but the time and money just wouldn't be worth it. Technology is constantly moving forward and the 20v was short lived. I would take a 16v 2ZZ over a 20v 4A because it has better technology and will outperform the 20V 4A but the 16V 4A will not, not with any reasonable amount of time and money.
I chose to stay 4A because I was able to plug it into my stock supercharged ECU and harness with minimal changes. If it hadn't have been for the ease of instalation I probably would have gone with a 2ZZ, 3SGTE or other engine.

There are very few people who have actually made more power with a 7A block. If they are lucky they might gain a little under the curve but as you said they are limited on how fast they can spin it. The general concensus is most of these builds haven't taken all the steps nescecary to get the gains that are possible but again the time and money is not really worth the gains. You need adjustable cam gears just to compensate for the increased block height, cams and preferably oversized valves to properly take advantage of the increased stroke and displacement. In the end you pretty much built a custom engine just to have 1.8 liters and marginally more power than a 4A at best. Again I would go with a different power plant long before building a 7AGTE.

Sure Ball bearings would be good but it's hard to warrant thousands of dollars for a turbo to put on a car worth a couple times that. Besides this isn't a project trying to squeeze every little bit of hp out of bolt ons. It's an experiment in engineering design and principle. If I can design and build something that improves it I gain something. If I just drop money on something that someone else has already designed and built I gain nothing.
I am thinking about making my own turbine housing for my 14B just for that reason. It would push my design and fab skills further than anything I have ever attempted. It would probably be single scroll just due to the added complexity of twin scroll but who knows. Maybe I'll get adventerous. If I did that I could build a flapper straight into the housing. Hmmm.

yoshimitsuspeed

Not really sure what you mean. I mean if I could have a turbo that spooled like a 14b or maybe even better but breathed like a 16G I can't see a downside.
It seems like flowing through half a 9.8 cm twin scroll should spool crazy fast.
I know for the power it makes the evo 16G spools fast. Moreso on the 2.0 4G63. It's still a long ways away from the spool on the DSM T25 I am running right now. On the other hand at 6 PSI boost I hit 13 PSI pre turbine back pressure by redline. If I could keep similar spool and cut that in half it would be a pretty sweet situation.

94AWDcoupe

iTrader: (125)

you cant use those on twin scroll turbos. you would be blocking the exhaust of two cylinders when the valve is closed. unless you made the exhuast manifold undivided. but that would defeat purpose of using twin scroll in the first place.


keep it simple. use the 14b like I suggested. if that does make enough power have the compressor cover machined to fit evo X turbo centre section.

GRNMCH

iTrader: (3)

This post really cracked me up . 14b is a solid, 250-260whp turbo on pump gas, with more mods and better fuel it can make 310-330 whp. It was placed in cars rated 190-195hp (165-170whp). If anything, it was TOO LARGE for the application! Seeing this, Mitsu engineers downsized their turbo on next model, by going to a T25.

14b is a fine turbo, with quick spool time, but… watch out for your intake manifold choice. When comparing 14b-16g turbos, with various exhaust housings, intake manifold can have a greater effect on the spool time than a turbo/exhaust housing size!

yoshimitsuspeed

Intake manifold is already covered.




It's the second mani I have made. First with a integrated Water to air intercooler. I went a little on the long side to give it some resonant induction in the middle to upper RPM. I also made my own bellmouth forming tool so I could make my own.
The IC acts as a massive plenum and with the ITBs and VVT it spools this T25 pretty dang quick. Getting excited to try the 14b on it though. At 6 PSI boost I am hitting 12 PSI pre turbine back pressure by redline. That can't be helping the top end.
I do want to dyno it on this turbo though so I can compare before and after.