I recently bought a 89 TGP with 88k on it. Very nice...kinda snappy. Want to go faster. I work in the auto induistry and am not afraid of the 60 degree V6. Will a T3 cause too much turbo lag? And are the injectors necessary? I can do custom exhaust at work and can bend/weld just about anything. My lacking knowlege is the turbo itself. How do I know if its too much? I don't want to blow this little guy up. I understand the T25 is small and a T3 is not a factory bolt on. Will a T3, injectors, and an increase in boost with a new header setup drop me into the 14's?
You will need bigger injectors, yes.
There have been many who have gotten well into the 14s with the T25. However if T3 is your route I would suggest a GT series turbo from Garrett. They are far superior to the T series and they will respond quicker due to less friction. They are very durable as well. If you plan on racing the car I would suggest that.
You are also going to need a tune and a fuel pump. Walboro has a 255 liter/hr pump which will be more than you will ever need ;) Kenny has a writeup on here somewhere
the thing about the T3 upgrade is the rest of the bottlenecks you'll have. namely the plenum and LIM with their long skinny intake runners, heads, and the exhaust manifolds. you might just consider dropping a 3400 in there and turbocharging that. a used/low mile 3400 can be had CHEAP and forged pistons are already available if you wanted to build it up. the 3400 can actually breath and won't fall on its face above 4000 RPM. you could run it on you current TGP wiring harness and ECM/chip with some tuning and injectors. obviously it wouldn't be SFI anymore, but it would work really well. lots of people on the J-body forum are doing that with great success. the big problem (for me at least) is fabricating and welding a rear exhaust manifold and making a crossover pipe and downpipe. add a 50-trim T3/T04E with a .63 A/R turbine and that car would scoot with minimal lag. you could just shelve the original engine for later use. the Garrett dual ball bearing GT turbos are NICE but $$$$. a Turbonetics T3/T04E hybrid would be about half the cost of a Garrett DBB GT turbo.
however, the stock turbo can get a TGP into the high 13s. i think some here have done it. just depends on how fast you want to go.
very high 13s and i think it was done with a 5 speed and tune. still pretty fast for stock motor/turbo... its more about the driver and getting the car to hook rather than spin the tires. But yea ... what he said. a 3400 w/TO4E .50/.63 SHOULD be a high 12 second car as far as im concerned!
What about the T25 hybrid T28 that a member here did. Also, what about the top end swap of the 3400 onto the LG5 engine?
Quote from: pontiac6ksteawd on December 25, 2008, 02:30:48 PM
What about the T25 hybrid T28 that a member here did. Also, what about the top end swap of the 3400 onto the LG5 engine?
you can use the stock TGP manifolds on 3400 heads but you have to port match the manifold and trim the 3.1 gaskets. Different pushrods are also needed, some say the gen 2 pushrods work, others say custom length is needed. Your almost better off using a whole 3400 with factory roller cam and installing an oil return flange on the pan.
the 3400 'LA1' also has a better oiling, more displacement of course, and a roller cam as killinprixs mentioned. the downside it there really aren't any aftermarket cams available (as far as i know) but i'm thinking the stock 'LA1' cam would be just fine anyway. i don't think there is any difference between the 3.1 MPFI naturally aspirated 'LH0' cam and the 3.1 MPFI 'LG5' cam. another downside (IMHO) is that the TGP 'LG5' engine just looks way cooler! if you could, try to get a plenum from a Ventura van - i don't think they say "3400 SFI" on the top. but they still don't look as cool and obviously don't look original at all when you pop the hood.
i have seen pics of ground down TGP exhaust manifolds on the 3x00 heads. they seemed to work (with LOTS of grinding to match to port shape) BUT their isn't much "meat" left for sealing so i thought it was a bad idea. those pics scared me away from the idea; especially considering the heat and pressure associated with being turbo'd. i would rather use an early log style 3100 'L82' rear exhaust manifold and block off the downpipe or cut it off and weld it shut. as a side note however, i haven't tried any of this myself so take it for what it is!. lots of good info can be found on the J-body forums though. i just don't want to give you the impression i actually know what i'm talking about with experience to back it up. i've only read ALOT about this stuff from other people who have done it.
the T25/T28 hybrid might not be very efficient. i *think* you would have to machine the stock compressor housing to fit the T28 compressor wheel which can lend itself to excessive heat. but i could be way off :) i would rather go with something like a GT2871R (with a the biggest turbine available) if you are set on keeping it simple with the T25 flange. but if you can weld and fabricate, go 3400! the 3.1 MPFI engines are kind of like the old TPI 'L98'- ALL low end and that was it. whereas the '90s 'LT1' 350ci had great midrange more like the 3400 'LA1'. you could also go really wild and go with a 3500/3900, but then their are more hurdles such as drive-by-wire throttle so something would need to be done about the throttle body and cable. some people have even turbo'd the 3.4L DOHC 'LQ1' engine, like timg (local guy, have seen and ridden in this car in person and it was CRAZY!). i just don't like the 'LQ1' engine. bad design IMO and difficult to work on. GM didn't get the DOHC V6 right until the newer 3.6L IMO.
considering the price of a low-mile used 3400 and that you said you can weld and do custom exhaust work, i would go 3400 and get a Turbonetics T3/T04E. get some larger injectors and learn to tune or buy a chip from someone with a similar setup and tweak it for your car. add a 5-speed Getrag 282 if you want, or build up the 4T60. you could also use a newer 4T65E-HD but i think you would need an expensive piggyback controller to run the 65E.