Well, back to turbo. Nearly all factory turbocharged engines blessed by high potential in the horsepower increase area. It is not unusual to see turbo motors running double or triple factory horsepower output on stock internals. It is not recommended of course, but possible (for some period of time). Recipe for big horsepower is to supply certain amount of air to the cylinders and provide proportional amount of fuel for combustion process. Fuel supply is relatively simple, when it comes to air supply things become more complicated and more costly.
First mod for the stock CT26 turbo popular among the beginners is to shim turbo wastegate (WG) with few washers. Result of this surgery is higher boost pressure, with too many washers under the WG bracket you can easily hit fuel cut at 12-14psi. Next natural step is installing boost controller. I don't know much about manual boost controllers, in my opinion they belong to the past. Though I have read some positive comments from MBC (Manual Bost Controller) users. Another question asked often is why should I spend $500 on EBC (Electronic Boost Controller) if I can get the same boost with few washers under the wastegate bracket. They are
talking
about peak numbers and forget (or are not aware of) linear WG response to the
rise of boost pressure. In plain English it means your wastegate will not snap
open at boost pressure, say 12psi, but starts crack opening from 2-4psi. This
kind of WG behavior has name of boost creep and makes your car feel much slower
than with properly tuned EBC. With EBC you can gain a lot of torque at lower rpm
because it can be tuned to snap open wastegate at predetermined boost level,
even allowing some boost spike. To increase boost safely and to achieve better HP results it is recommended to
get rid of stock downpipe with incorporated first cat in favor of aftermarket 3"
downpipe. This is the best first thing beginner can do to his 7MGTE. Best
downpipe is divorced type, it eliminates restrictive turbo elbow and bolts
directly to the turbo. Good downpipe alone can give you 12-15whp gain easily.
Just remember - restrictive exhaust system is not healthy for your turbo and
cost you horsepower. It absolutely makes no sense on turbo motor trying
different horsepower enhancing mods without having proper exhaust system. Second
stock cat has to be replaced by aftermarket high flow 3" or 4" cat, or test pipe if you
are not law abiding person. Then buy decent 3" catback, anyone of them worth
another 10-12whp increase. If your HP goals big - better buy 4" Goliath catback
from Horsepowerfreaks. Though such large size becomes a necessity after 600whp
it never hurts to have it as big as possible. When I was shopping for catback
there was no 4" on the market and I settled on 80mm Blitz Nur-spec and Random
Technology test pipe. I also used Random Technology downpipe and Suprasport
turbo elbow. There was no such thing as divorced downpipe back in 2000 when I
purchased my exhaust system components. As I said above divorced downpipe gets
you better bang for your buck, it costs less then elbow + stock replacement
downpipe and performs better because wastegated exhaust gas won't collide with
exhaust gas exiting turbo inside the elbow. It flows through the dedicated pipe
which smoothly merges with downpipe about 8-10 inches downstream the turbo.With stock CT26 and supporting mods you can run 15-17psi of boost and achieve around 300+whp. Some people are satisfied with this result and keep driving there BPU Supras for years, but if you are real boost freak and think big power-wise your decision will be to ditch CT26 and jump on bigger turbo. Another alternative is to upgrade CT26, it can give you power similar to T3/T4, hybrid turbo in the range of 450whp. Experienced in car modifications area folks may go straight from stock to big turbo and supporting mods. You have to ask yourself are you going to be satisfied with 400whp or maybe you need more? If budget permits go straight for big numbers, even if your project takes a year or more to be completed. In the end you save $$$ because you did not spend your time and funds on half-ass mods (like I did)
When it became clear my stock CT26 was going down I ordered in summer 2001 T3/T4 hybrid turbo from Suprasport. Kit included oil and coolant supply braided hoses, as well as new oil drain line. Suprasport was offering stage 3 and stage 5 options for their turbos, stage 3 was good for 400+whp, stage 5 - for 500+whp. Stage 5 was offered also with ball bearing CHRA as a $500 option. Both turbos had 360 degree thrust bearing which made them more reliable then obsolete 270 degree bearing. Back in 2001 I thought I would be completely satisfied with 400whp and ordered stage 3 kit and Spearco stock replacement intercooler to complement expected horsepower gain. Stage 3 turbo was just a little more laggy than CT26 and offered of course much better top end power. My best run was 12.92@115.45 on 1.4 bar boost on that turbo. I used APEXi AVCR and SAFC, Lexus/Riemer upgrade and Spearco IC.
After driving 3 years on T3/T4 I decided I've had enough and time has come to move to something bigger power-wise. My biggest concern with bigger turbo was turbo lag, so definitely I needed ball bearing turbo. I also wanted kind of plug'n'play solution, in other words turbo kit. I did not want Greddy kit because I thought T78 was laggy. The only other kit I was aware of was made by Sound Performance. In 2004 they introduced new line of dual ball bearing turbochargers and I ordered through Suprasport turbo kit with SPSSGT650WBB turbocharger, rated 650 hp. As a standard exhaust manifold, turbo and downpipe come ceramic coated, compressor housing polished, kit included HKS 60mm GT wastegate. Later I realized 60 mm WG was too big for my horsepower, if I started it all over again I would better used much lighter (and cheaper) Tial 46 mm WG. I ordered my kit with open to atmosphere WG because I did not like how SP connect WG dump pipe at 90 degree angle to the downpipe. Besides, I saved a pound or two of weight.
Sound Performance don't provide compressor maps for their turbochargers, I would be very much interested to see map of my compressor. If you are shopping for the new turbo and manufacturer is able to provide compressor map it is always good idea to take a pen and calculator and find out how well the turbo you intend to buy matches your motor flow rate. Very good article scanned from SCC can be found here. It is written by Mike Kojima, I like his Suck, Squish, Bang, Blow series of tech stuff in the above magazine.. Besides turbo matching calculation method you will be able to find many other useful tips on choosing turbo.
Below are few pictures of my turbo kit installed. I am supporter of using heat insulation on turbo, used it on my old T3/T4 and continue using it on my new turbo. Ceramic coating supposed to help in heat insulation area, but I decided additionally to add Thermo Tec heat wrap on exhaust manifold and downpipe. I put turbo
