4BD1T Turbo Sizing and Performance Prediction.

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Originally Posted by Vern

Screw is out 4.5 turns now, getting a little smoke but not to bad, egt's about the same, seems to lack top end in the first three gears, won't pull away from down low in 4th and 5th either. I need to take it for a better run, bit hard with no rego to go to far. May be I'm expecting to much, its been a while since I've driven one.:)

Now I'm thinking of ordering the 22psi spring, and if I want more boost just wind the actuator in. Am I in the right ballpark? (Current spring is 7.3psi)

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I'm still not sure who will finish first between us. Currently I think we're on track for a dead heat, last place. :wasntme: :D

Vern at what rpm does it hit 22psi in top gear

Top gear, no idea, my runway is not long enough, 3rd gear, I'd guess 2500-2800.

Justin, I was hoping for rego this month, now scheduled for next month:D

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Originally Posted by Vern

Justin, I was hoping for rego this month, now scheduled for next month:D

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Mine is always scheduled next month!

So I have now fitted the 22psi spring, Turbo hits 28psi rather quickly. Haven't been for a decent drive though yet. Fuel screw is out 4.5 turns, a little black smoke, not much. Smells very fuelly though:(

That is some pretty epic boost.

I'd wind it back to the low 20's, tune it in and then increment it slowly from there.

Yeah will do dougal, that was just a quick squirt up the road. Going to wind it all back

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Originally Posted by Dougal

If you have an engine around the 2.5-3 litre mark there are plenty of VNT turbos that will work nicely. But our 3.9 litre engines have nothing suitable. The VNT turbos are also an intermediate step in turbocharging which doesn't offer the performance or fuel economy possible.

I have a 300tdi now. I won't be putting a VNT turbo on it. I'll be doing something else which is far better.

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A little late to this thread, and a little off topic, but I'm interested to know what direction you're heading for the 300tdi turbo? A guess would be some kind of hybrid gt22 running billet wheels....


Pondering my choices on my Td5, currently running a GT2052V off a patrol, which builds boost from about 1300rpm pretty quickly (currently have about 14psi by 1500rpm, and 21psi at around 1800rpm). I'm pretty sure 21psi is way off its map though, and certainly feels a bit choked after 3000 rpm, and also feels like the airflow through the engine stalls a little after being spooled up fast at low rpm, until the turbine gets more speed up. I was thinking about going to the turbo technics VNT (GT2256V, IIRC?) but your post suggests there is another option which should boost from as low as the VNT, but flow much better up to 4500rpm?