Thread: 33tdi turbo

A mate of mine has a Disco 300 tdi manual and he asks if fitting a larger turbo and larger intercooler will give better fuel figures. Jim

bigger turbo?

A bigger turbo will not give a diesel 300 Tdi better fuel figuers on average. Bigger turbo to me implies more air at higher rpm. You are not going to spin a diesel much faster than 4500 rpm, don't know what the 300 Tdi is limited to but I expect that it will wind back the fuel if you try and spin it too fast.

A smaller turbo is limited at the top end as the faster the motor spins the more air it needs.

The bigger turbo will take more to get it going so it will not give you boost until you have got a few revs up, the smaller turbo will spin up faster for two reasons: less mass to spin up and smaller orifice for the exhaust gas to flow through therefore flowing at a faster speed and spinning the turbine up faster.

Bigger intercooler will help once you get to steady state but will also introduce a little bit more lag in the transient response.

Do some searches and you will find a lot of information in many threads.

Variable geometry turbos give you some of the best of both worlds little turbo response at lower gas flows/lower rpm and big turbo performance at higher gas flows therefore not overspinning or choking the exhaust.