Thread: 4BD1T Turbo Sizing and Performance Prediction.

Originally Posted by Dougal

I haven't found a garrett map yet with a shape suitable for the whole operating range of the 4BD1T. The GT2259 starts well on the surge line but doesn't have the pressure capacity or flow capacity to use what the stock fuel pump can deliver.



I have no idea what rovercare is up to. He's been on my ignore list for a long time now.

The GT2260V has a turbine that is both less efficient and has less flow capacity than the wastegated turbos I'm recommending.
The lower efficiency is caused by the VNT mechanism, put simply extra vanes are a flow restriction and trying to turn the flow to create more boost causes more flow restriction. This lower efficiency means higher exhaust pressure to deliver the same boost. The higher drive pressure reduces engine power. Particularly as rpm builds.

The lower flow capacity is a huge problem with VNT turbos. They have no ability to bypass extra exhaust flow around the turbine which means on a larger engine (like 3.9 litres) they reach flow limits quickly and start to spike exhaust pressures. Limiting boost and engine response.

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.

Thanks Dougal for explaining, all makes sense in theory, but in practice I'm still pretty happy with mine for both power and economy. When mine carks it I'll go shopping for a more efficient one, but until then I'll keep enjoying it! Has anyone got some economy or power figures of what is possible with the turbo's you suggest?

Cheers,

Andrew.

Originally Posted by taylorslandy

Thanks Dougal for explaining, all makes sense in theory, but in practice I'm still pretty happy with mine for both power and economy. When mine carks it I'll go shopping for a more efficient one, but until then I'll keep enjoying it! Has anyone got some economy or power figures of what is possible with the turbo's you suggest?

Cheers,

Andrew.

How does 200kw and 800nm grab you? This is the HE221. It is capable of more boost (45psi) and worst case boost is ~40psi.
The TD04HL-19T is more efficient in the middle of the map so whould provide better fuel economy but can only do ~30psi. This limits you to a conservative 650Nm and 190kw (unless you've got an awesome intercooler).
Fuel economy depends upon a thousand factors. But these should all deliver more boost than drive pressure until at around 2500rpm at full load.

My t25 can only deliver more boost than drive pressure until about 2000rpm.

With those sort of figures I will be wanting to build an engine that I know can handle it

Originally Posted by Vern

With those sort of figures I will be wanting to build an engine that I know can handle it

Standard 4BD1T.
Intercooler with a core of ~600x400mm.
HE221 wastegated to 40psi.
Injection pump set to 180cc/1000 shots.
RPM screw backed out to 4000rpm.

Or compound a Td04HL-19T with a GT3582 turbo (1.05 A/R turbine).
Set the GT35 wastegate to ~12psi.
Set the 19T wastegate to start opening at 35psi
Set a limit screw on the 19T wastegate to induce some boost creep as rpm builds.
Should do close to 250kw at 4000rpm.

Can lower these boost numbers a bit if your intercooler is truely awesome. Air cleaner sizes start to get out of hand.

Yes but mines just a standard 4bd1, no T on the end

Originally Posted by Dougal

How does 200kw and 800nm grab you? This is the HE221. It is capable of more boost (45psi) and worst case boost is ~40psi.
The TD04HL-19T is more efficient in the middle of the map so whould provide better fuel economy but can only do ~30psi. This limits you to a conservative 650Nm and 190kw (unless you've got an awesome intercooler).
Fuel economy depends upon a thousand factors. But these should all deliver more boost than drive pressure until at around 2500rpm at full load.

My t25 can only deliver more boost than drive pressure until about 2000rpm.

Sounds awsome! Impressive figures. But like Vern mine hasn't got the 'T' on the end, would it still handle "just" 30psi boost?

Originally Posted by taylorslandy

Sounds awsome! Impressive figures. But like Vern mine hasn't got the 'T' on the end, would it still handle "just" 30psi boost?

You'll need the reinforced pistons (alfin) and you'll want the nitrided crank with oil squirters.
So yeah, factory T will be the easiest way.

My ignore list buddy Dougal forgets he has never done any of the mentioned mods, nor, from my personal experience will the pump deliver the fuel required.....but anyway, practice verse theory is a funny thing.....this thread needs more graphs