The V8 Owners Forum -

I've heard of these 2 types of rover V8 injection that was used on Range Rovers.
I believe flapper was used on 3.5's and 3.9's, but the later 3.9's were hotwire?
What are the differences and why is the hotwire regarded as so much better than flapper?

there are many differences but the main ones are:

Hotwire has a fully digital ECU flapper doesn't and hotwire's air flow sensor is just that a hot wire where the flapper has a big flap sitting in the airflow.

The flapper system is really old now and as such can have a lot of problems purely down to its age. It also cant control the fuel as accurately purely by its very nature. It was a marvel in its day but it is well behind these days. Its also very difficult to alter the fuel curves, where the hotwire can be chipped.

Like I said there are many more detailed differences which all add up to the hotwire being a better system although these aren't the greatest systems these days either in the modern scheme of things.

Should also add I cant think of any 3.9 engines with flapper injection, they are all hotwire unless there are some very rare examples kicking around. Equally there are a small number of factory hotwire 3.5 engines around.

The hotwire also has idle speed control.

Chris.