The History of My Car & Engine

from Rally Bashing Hack to Weekend Racer

STAGE 5 - G200 Draw Through Turbo

I finally got the turbo set-up fitted.  Before bolting it to the engine, I set it all up on a spare head that I had in the workshop, to make sure everything would fit.  I got hold of a piazza exhaust manifold and a stock VL Commodore T3 Turbo .  I got a flange laser cut to suit the turbo exhaust housing and had it welded to the piazza manifold.  I then ported the manifold and head to get a smooth transition from the square Gemini head exhaust ports to the round manifold ports.  I made a 3" dump pipe that had a conical section which blended back into my 2.25" exhaust.  I also put a stock cam back in.

The turbo needed an oil supply, so used one of the spare oil gallery ports for this, and had to fit a large barbed fitting to the sump for the oil return.  I also teed into both heater hoses for the turbo water cooling bearing housing.

I had bought a 45mm side draught Weber, and planned a draw through set-up.  I got a few aluminium plates laser cut so I could use an aluminium cross over pipe and bolt it to the stock inlet manifold using the Nikki mounting studs.  I also got a plate laser cut to suit the Weber mounting flange and fabricated a 'y' piece to mount the Weber on the front of the turbo.  I put the battery in the boot, because the Weber now used that space.  I bought a HZ accelerator cable which was plenty long enough.

The cross over pipe was longer to go from the turbo to the inlet manifold, but I cut it short one day to use the pipe for my blow through set-up.  I thought I could always rejoin it later if I had to.

I remember the very first time I drove it out of the yard and felt it boost for the first time, only a few psi then I backed off, the sound was awesome, and compared to what I was used to, so was the push in the back.  I couldn't go back now.

I also couldn't go past about half throttle, as the engine would die, just like it had no fuel.  I was sure the fuel bowl in the Weber was getting fuel, had to be a jetting issue I think.  It was jetted to be half of a twin Weber set-up of a Datsun L20 engine from memory, so it was jetted to only deliver fuel for 1 litre of engine displacement (twin Webers fed a 2 litre engine).  

I also had another problem, every time I let the engine idle, or whilst cruising along and then boosting it, it would blow plumes of white smoke out the exhaust pipe.  The VL turbo is designed for blowing into an EFI throttle body, so it is never supposed to see any vacuum before the compressor.  With my draw through setup, the Weber was obviously before the turbo compressor, and the vacuum at idle and part load was sucking oil past the compressor oil seals and it was being fed into the engine under heavy load.

Because of the carby issue, I couldn't really get it to boost at full throttle, so couldn't have that much fun with it.  Was great at half throttle though.  One thing I didn't really know at that stage was how much timing I was actually running total, let alone how much I should be running.  I was also only guessing at my air/fuel ratios.  That motor didn't last long.

And because of the smoke issue, I knew I had to move the throttle body to after the turbo.  This meant either a Gas Research throttle body, an EFI set-up, or a blow through carby set-up.  I didn't like gas that much, and figured the carby was the cheapest, and I thought I could do it myself, so I read some more books....

Check out STAGE 6 - G200 Blow Through Turbo.