TB v STT turbo on 300GD 460
I have a TB turbo fitted to my 89 300GD.
I have just inherited an STT turbo from an 88 300GD.
The STT was running 14 psi but TB is only set for 7 psi (going by waste gate opening pressures). The STT was fitted with a big exhaust and tuned up on the injection pump so did just about a 100 mph in it's day; I want to get back to this level as the TB is struggling with the oversized tyres (33"?) which hit the 5 speed gearing just wrong so that 5th really is hard to hold 70mph.
The STT.. does it require a car alternator?
... the waste gate can is right into the alternator. (STT manifold puts turbo between 1 and 2 cylinders instead of level with cylinder 3 on the TB). The TB has a Garret turbo fitted which I know is not original and they have used KKK turbos for the last 15 years according to TB; the Garret's waste gate can hits the engine mount and is at a horrible angle too.. maybe the KKK is better. Also will need to extend exhaust by 3-4"..
I have a STT turbo, and am very happy with it. I have driven a TB turbo, and there is a big difference, but I'm not sure about a 100 from my LWB. I have taken it up to 90 when I just got the car, but after that the revs worries me. My car has a intercooler as well, so that could give me the extra power. I also run my car on big wheels, 245/75/16, and up to 90 wasn't a problem.
As far as reliability goes I think they are the same.
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LEEU,
Do you have the snorkel on the back of your alternator? The alternator back should be flat and there should be a rubber tube sticking up 5" from the driver's side. I think you have to take this off or fit a normal car alternator.
It was on a LWB and 90 was normal max but on a long hill you could get 100 and then maintain it on the flat .. had no rev counter but it must of been close to red line! Mine has no intercooler but it does have a "cooler" box on the top of the inlet manifold. The turbo's look identical except for the size/setting of the waste gate can .. turbos can be deceptive and these are old T2 turbos with no A/R ratios on the casting unlike modern ones.. but I bet it is all in turning up the boost and fueling that makes the difference... need to get a EGT (exhaust gas temp) gauge and then go tuning up a big hill or with big trailer while watching the exhaust for soot; but I have not worked out how to turn the fueling up or if timing needs altered. Oh and that 100mph engine did kill the quill shaft that drives the vacuum pump and the timing pulley on the injection pump split in two .. all at around 100k miles.. so maybe too much rpm was the issue.. it sure used to work hard!