Hello Simon,
From information that Harvey provided, inside the 't' piece which fitted over the inlet of the air canister, there was a flap which directed air depending upon temperature either from the exhaust manifold on the driver's side or from an air duct aimed towards the front of the engine bay. So yes indeed, all of this would certainly have compromised air flow into the engine.
As Chris rightly pointed out, everything that you do to an engine which has an effect on either air coming into or exhaust coming out of will affect a change in the air / fuel ratio. For the Rover V8 of any capacity, the maximum power and torque at any given rpm requires the air / fuel ratio to be the ideal 12.5 : 1. When I had my Rover with its original 3.5 run on the dyno, the air / fuel ratio ranged from 13.8 : 1 down to 12.5 : 1 right at the end of the run at around 5500 rpm for one tiny moment. For most of the run it was above 13.0 : 1. The air filters were foam of essentially the same surface area as the OEM papers, and the exhaust down pipes were single skin as opposed to double skin where they joined beneath the engine, so flow was a little better. The needles were the original BBG, and as could be seen the engine was running less than ideal in terms of the air / fuel ratio for delivering maximum power.
My 4.6 had its new exhaust system, air system, ignition system all suited to the specifics of the engine which runs a high torque custom ground camshaft designed to improve the performance of a Range Rover, and being an automatic the right outcome for my P6B. Once the needles were polished and the testing completed on the rolling road, the air / fuel ratio ranged from a high of 12.8 : 1 quickly improving to 12.5 : 1 + or - 0.1 for most of the test.
These figures are of course for acceleration, maximum power and torque delivery. When cruising at light throttle settings on the open road or down an express way, the air / fuel ratio is much leaner which is as expected. It just goes to show what a truly wonderful piece of engineering the SU carburettors really are.
I hope that this has been some help to you Simon.
All the best,
Ron.
From information that Harvey provided, inside the 't' piece which fitted over the inlet of the air canister, there was a flap which directed air depending upon temperature either from the exhaust manifold on the driver's side or from an air duct aimed towards the front of the engine bay. So yes indeed, all of this would certainly have compromised air flow into the engine.
As Chris rightly pointed out, everything that you do to an engine which has an effect on either air coming into or exhaust coming out of will affect a change in the air / fuel ratio. For the Rover V8 of any capacity, the maximum power and torque at any given rpm requires the air / fuel ratio to be the ideal 12.5 : 1. When I had my Rover with its original 3.5 run on the dyno, the air / fuel ratio ranged from 13.8 : 1 down to 12.5 : 1 right at the end of the run at around 5500 rpm for one tiny moment. For most of the run it was above 13.0 : 1. The air filters were foam of essentially the same surface area as the OEM papers, and the exhaust down pipes were single skin as opposed to double skin where they joined beneath the engine, so flow was a little better. The needles were the original BBG, and as could be seen the engine was running less than ideal in terms of the air / fuel ratio for delivering maximum power.
My 4.6 had its new exhaust system, air system, ignition system all suited to the specifics of the engine which runs a high torque custom ground camshaft designed to improve the performance of a Range Rover, and being an automatic the right outcome for my P6B. Once the needles were polished and the testing completed on the rolling road, the air / fuel ratio ranged from a high of 12.8 : 1 quickly improving to 12.5 : 1 + or - 0.1 for most of the test.
These figures are of course for acceleration, maximum power and torque delivery. When cruising at light throttle settings on the open road or down an express way, the air / fuel ratio is much leaner which is as expected. It just goes to show what a truly wonderful piece of engineering the SU carburettors really are.
I hope that this has been some help to you Simon.
All the best,
Ron.