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The "BIG" turbochargers
This is the crown jewel of HKS single turbos (although the GT3245 in the HKS drag celica is probably bigger, i've NEVER seen it in the US) This turbo in size, is slightly bigger than a T66, but has an exhaust housing that is quite a bit bigger, it ships with 0.96 stock, and makes TONS of power. Bryce Danna made his ~830 rwhp with 75 shot of nitrous with this turbo, that looks like ~760+ rwhp without bottle most likely, which is plenty. Its probably possible to make 800 rwhp on turbo alone with this turbo, which is very impressive. You will want upgraded internals most likely, along with cams, Gforce computer to raise rev limiter, a BIG fuel system, and either a high-stall torque converter, or a stick, with a very nice clutch. This turbo is BIG and has significant lag. You are waiting for it quite a bit, probably 800 rpm if not more of noticable lag. I would say its POSSIBLE to have this turbo on a "street" car, but I wouldn't do so personally because i'd want nitrous to spool this big boy up, its pretty laggy makes full boost around 5k. No one has really made any passes with this turbo yet that have been very fast, but maybe this year someone will.
This is probably the most common twin turbo setup, these are pretty big twin turbos, about the size of a TS04 0.58 for each turbo, but most often they come with 0.70 exhaust housings... I would switch these with 0.63s personally, unless you are a glutton for lag, with the stock housings they make full boost in the early 5k range with cams. You do have quite a bit of potential here, I believe you can make 800 rwhp on the HKS GT2835s with the proper setup, which is PLENTY of power. With the smaller housings, you can probably have 700 rwhp with lag in the mid 4k range, which is quite a bit too. Very nice setup, but insanely expensive for what you get, almost twice as expensive as the RPS kits.
These turbos are similar to the T66, but bigger. Most of the T70s are pretty similar to the T66, although they have a slightly bigger turbine wheel. This allows them to make somewhat more power, but at the cost of somewhat more lag. A T70 is good for probably 30-50 rwhp more than a comparable T66, but has about 2-300 rpm more lag. T72 is correspondingly bigger, it uses a different compressor and turbine wheel setup, and allows for significantly more power, but quite a bit more lag. Supposedly capable of 800-900 rwhp, the T72 makes full boost in the low/mid 5k range. I haven't heard of anyone using the T76 as this is simply too big a turbocharger, it would make TONS of power, but probably not make full boost till ~6k rpm. RPS sells kits with all of these turbos, although I believe that the T72 and T76 have to be special ordered.
These turbos are made by mitsubishi and modified by Greddy, the T78 uses a TD07 exhaust housing with a TD08 compressor, T88 has TD08 on both sides. T78 is capable of an insane amount of power, at the cost of monumental lag, although with a stock motor, the T78 may make full boost in the mid 4k range with proper tuning. T78 can make ~750 rwhp on the turbo alone if tuned right, you do need electronics, a higher rev limiter, cams, probably headwork... T88 is good for maybe 20% more power... this is one of the few turbos that is theoretically capable of flowing enough air to approach 900 rwhp, although you would need a SERIOUS engine build up to do this. Ara from NJ has run 141 mph traps with a T78 w/o bottle, Humberto has run 9.8@14x with T78 with nitrous, and a number of other people use the T78 as well, mainly because its quite inexepensive today, selling for under $4k. The downside to the T78 and T88 is that they need ALOT of work to get them working to their potential, and they lag into the low/mid 5k range for the T78 and even more with the T88, a car with this turbo is almost non-streetable in my opinion.
These are the biggest twin turbos available from HKS as far as I know. Craig Paisley uses this setup, as does the UPRD car. This is one of those turbos that should have a tag on it that says "DO NOT USE WITHOUT NITROUS" in my opinion. You will probably see lag in the ~6500 rpm range, which is fine for the strip, with nitrous, but for a streetable car? remember the supra's stock rev limiter is 6800 rpm, although obviously you would raise it if you had these turbos... These turbos are probably capable of 1000-1100 rwhp w/o nitrous, but you need headwork, internals, fuel system, and probably lots of other custom stuff to use these turbos, don't do it unless you have nearly infinite money.
The T51 is similar to the HKS T-51R, but makes boost somewhat faster. As far as I can tell, this turbo spools like a T66, but makes quite a bit more power. You will obviously need a fuel system to go with this, along with cams. This turbo is borderline streetable, it spools quick enough to drive around, but makes alot of power, even at low boost levels, so you have to be careful there, I can live with the small amount of lag it has, some people might not be able to.
The T55 is quite a bit bigger turbo than the T51, probably good for around 900 rwhp on the turbo alone, but quite a bit laggier too, I wouldn't really consider this a streetable turbo, it should probably be for the track only, like some of the other big turbos, although its not QUITE as laggy as the biggest T88. You will need built internals, cams, fuel, etc... to do this correctly.
A couple people have done this, the most famous of which is Vinny Ten of Performance Factory in his 8 second supra, with twin TS04 (0.50 A/R>. Supposedly good for 930 rwhp on turbo alone, it most likely has insane lag, but noone really knows, obviously this isn't a totally streetable setup, Vinny's car is race stripped and back-halved. He also uses a distributor based ignition system. This setup takes alot of custom work, I would consider it only if you are willing to withstand a signficiant amount of lag, quite a bit of downtime for your car, and have alot of funds to work with.
Jarrett Humphries informs that the Powerhouse Single turbo kit makes around 630 rwhp and 645 tq with full boost by 4200 rpm. This turbo is based on the T61BB, and people have gotten great results out of them, he says one of his customers ran 10.3@139 w/o bottle on stock motor/heads with the kit. Never ridden in a PHR powered car, but they have had a great track record. Jarrett also sells a twin turbo setup based on the HKS GT2835s, not sure of their performance, although we should see shortly, as someone locally is installing them, they are supposed to make boost in the low 4k range and make 700+ rwhp, we shall see. Both of these kits use HKS manifolds with high quality aftermarket fittings and lines.
This year, a number of drag only turbos have come out... the SP90 is a turbo used on 7 second doorslammer grand nationals and mustangs, although it is supposed to spool up pretty fast, I kinda doubt that. I would imagine this turbo makes boost in the 6-7k range, but its capable of 1400 rwhp... the Y2K is a huge turbo as well, MVP/PHR made ~1200 rwhp with this turbo w/ alcohol. The T100 has never been used on a import to my knowledge, but it would be capable of well over 1500 rwhp.
Information Source: sr20det.nismo.org/bigturbos.htm
