Thread: Compound Turbos

Hi Dougal.

As I know bugger all about the tachnical side of a compound set up, this may seem like a dopey question......

In this example the lower turbo output is plumbed to the inlet of the upper turbo, which is then further pressurized and sent to the inlet manifold - a bit like a 'series' electrical circuit. I suppose this arrangement lends itself to the 'compound' title.

Is there any advantage of this over a 'parallel' system that directs the independent 'outlets' of each turbo to the inlet manifold - say via a 'Y' junction?

I would have thought the upper turbo (turbine) would have shown some inefficiencies by having to cope with air pressure from the lower turbine as well as doing its own thing?

??

Matt

Yes it's essentially series turbocharging.

The problem with parrallel turbocharging is with high boost. A turbo that works over most of the engines rpm range with 10psi will cover a much smaller part of the rev range at 20psi.
Compound or series turbocharging lets the small turbo cover the wide range that it can as a low boost single, but still gives high boost due to the larger turbo pushing it along.

The larger turbo also benefits will the small turbo increasing the airflow through it and bringing it on boost much sooner than it can alone.

Originally Posted by Dougal

Bush65 has a compound set from an international which he plans to fit. I also plan to do a compound set but keep running out of time or money or both. Anyone else keen?

I'm just wondering why you need so much power? With a turbo 4BD1 the last thing I need is straight line acceleration, I'm already overtaking Patrols and Landcruisers while accelerating up hills. The torque, power and strength of these engines really are impressive and with a 350 EGT post turbo I'm sure I could easily get more but in the real world there's corners, stopping distances and noise.

If the answer to the above is simply "Because you can", then great, I look forward to the video