Mr DM how are you??

I already have the bigger stock replacement IC was OK before only planning to run 18PSI at the turbo. Like i said i am not after huge performance gains just a new turbo.

Bush65 - Thanks for all that info!

The engine has a Brake Specific Fuel Consumption (BSFC) - this is the fuel rate to make power (in imperial units: lbs/hp hour, in metric units: g/kW hour). For most diesel engines it is in the order of:
0.36 for a turbo and intercooled diesel
0.38 for a turbo, non-intercooled diesel
0.42 for a non-turbo diesel

With a diesel the air/fuel ratio at the smoke limit is approx 18:1. So when determining how much air is required when selecting a turbo, it is best to aim for 22:1.

So you can then pick what power you want to make.

Use the BSFC (if you have a known value for the particular engine, that is best, otherwise use figures above). Note: the fuel injection pump needs to be able to deliver this fuel rate, or change your power expectations.

Then you can than calculate the mass flow of air required using the air/fuel rate above. It may be necessary to convert mass flow to volumetric flow, depending what is used on the available compressor maps.

The boost pressure required corresponding with the required mass flow of air is a function of engine displacement, engine rpm, volumetric efficiency, Gas Law Constant and the air temperature at the compressor outlet.

Volumetric efficiency is usually greatest (88% to 95% for modern 2 valve engine) at the rpm where the engine makes maximum torque, and reduces similarly to the torque curve at different rpm's.

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John

Man you guys know way too much about turbos.

I would feel very happy having you work on my turbo, I like to get more power from my 300tdi and this just gave me plenty of info.

Thank you, had to read it twice to get it all.

Cheers

John,
22 psi is 1.5 bar (assuming the online converter is right), whereas the stock turbo has 1.1 bar limit accordingly to the manual.
I haven't bolted my VNT yet (too cold), how did you tune yours at time?
I'm planning of a replacement intercooler (in standard size) to follow when the funds will allow, but reliability is still high on my priority list.

Yes, 22 psi is approx 1.5 bar.

1.1 bar is approx 16 psi. Is it the manual for the HS2.8L which says the limit is 1.1 bar?

I only have a parts manual for the HS2.8L, which doesn't provide technical specs. - over 22 psi is the boost pressure I have seen reported for those engines.

You should easily get 22 psi (1.5 bar) with your VNT turbo and 300Tdi, by adjusting the fuel injection pump. They don't have a waste gate to limit boost, it is governed by the energy in the exhaust gas.

I over-tensioned the head bolts on my 300Tdi to provide increased clamping pressure on the head gasket (for security with the higher boost pressure). Multi Layer Steel (MLS) head gaskets were not available (to my knowledge) for the 300Tdi back then.

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John

Morning!
Technical specs for the Tdi; the workshop manual says 1.1 bar max in the engine specs.
Dunno, 1.5 seems a lot...

With the stock turbo, 1.1 bar is reasonable for max boost pressure, and 1.25 bar is pushing into the poor operating region of the compressor.

But your new VNT is a much different turbo with a larger compressor that will operate with good efficiency at 1.5 bar. The increased air flow will allow the engine to produce more power with acceptable egt - something the stock turbo won't.

Just try increasing the fuel in small stages and test each increment with a good load to confirm maximum egt is within limits.

The pic below shows the difference between the compressors - 300Tdi turbo on left and the VNT turbo on right. Although there is not much difference in the inducer (inlet) diameter, the exducer (outlet) and housing A/R (0.48 vs 0.52) of the VNT compressor is larger and the VNT impeller has more vanes.

Attached Images

Compare Compressors.jpg (36.9 KB, 84 views)

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John

Thanks for the prompt reply!
Will get an EGT soon...VNT is still on the shelf, waiting...

Keep the info coming it's good stuff!!!!

I had a an hour or so on the weekend to have a play so i fitted the air hoses and the hooked up the IC. Picking up the oil lines tomorrow. Also gave the manifold a paint.

I finally took it for a drive today! So far well worth the effort!

It has defiantly has made a difference didn't really notice on the flat road at first but up the long hills and at 100ks it now pulls away. And from a standing start the difference is awesome! Even with the 35" peds on you can really feel the torque!! I can even hear the turbo spooling up over the roar of the tyres. I think i have an exhaust leak some where but no big deal atm. Hoping to take it for a proper long drive on the weekend with the road tyres.

Mick