Gearbox mounted turbo

[Ruan]

So is lag just due to the inefficiency of the turbine/inertial/friction losses? Obviously boost threshold is a design feature, as a turbo has a set operating range.

Yeah, lag is as you said above...

Boost threshold is set generally by the turbo manufacturer to correspond to the engine... Some engines need high turbine airflow, but not much boost, other engines need lots of boost... They'd be set up vastly differently for each engine type...

Hence why the Saab LPT turbos aren't the best match, since they need lots of airflow to keep restriction down, but naff all pressure..

[Poodle]

I stand by my statement tbh, although i could do with adding some qualification in there i guess. What i'm saying is that i'd expect the 1752 to be laggy for it's capabilities compared to other turbos likely to be fitted as an upgrade to a HDi. I may be mistaken, but i thought the 1752 was a considerably older design and hence less efficient. Comparing it to an ancient T25 isn't really representative imo, a 2056 would be a much more appropriate comparison.

[toseland]

Turbolag is CONTRIBUTED to by internal design/frictional losses/inertial losses, but its main cause is turbine overall mass..

contrary to popular beleif, the hotter the hotside the better (more heat on the hotside = more energy in the exhaust gases to turn the turbine etc)