Quote:
Originally Posted by Mgaz
If your KV6 has a rattle in the inlet manifold, how much is it to be fixed?
A guy on youtube has said
Is this an okay solution? Has anybody tried this? 
Just trying to get an idea of how much trouble a VIS problem is going to be to put right.
I like the idea of removing the offending parts from inside the manifold. If that can be done? |
If only the masters had allowed an aluminium inlet manifold. The 800 had one.
From what I have read, Rover designed the KV6 on the then present F1 engine technology.
The variable intake system is about getting the maximum volume of air into the cylinders at the critical time – when the inlet valves open to get the maximum power.
The engineers have to seek the best torque performance over a wide rev band – especially important for road cars that operate over a wide rpm range and this is why we have a variable intake system.
Cars without a variable intake manifold only have one power peak in its torque curve.
Through its variable intake manifold, the KV6 has expanded its torque peaks to four – thus increasing its power torque over a good part of its rev range. A second plenum is imbedded within the inlet manifold to assist in this objective. Granted not quite a flat “power curve” but on the graph that I have seen, all four peaks are above the “single torque curve” of a non- VIS engine – naturally aspirated engines. I read that power and torque gains of up to 30% have been achieved in some engines (as much as low-boost turbocharging achieves).
I guess that without a VIS system, engine designers have to make concessions that, to a point affect performance across the rev range.
The engines cycle is constantly affecting the engines airflow intake as the inlet valves shut off. This pressure wave (in the intake port) then rebounds back towards the plenum, lowering the pressure in the intake port. As the piston descends, and low pressure develops in the combustion chamber, a negative wave (being below atmospheric pressure) rushes towards the inlet valves. This wave when tuned properly has the potential to ram more air into the engine and improve the power. That is if this rushing pressure wave (of air) reaches the engine at the critical time - when the inlet valves open. That is the theory of varying the intake length to match the engines requirements and pressure waves.
If the incoming pressure wave “arrives” whilst the inlet valves are closed, this powerful pressure wave rebounds back up the inlet manifold towards the plenum, and the engine will only receive a portion of its potential intake. This will have a detrimental effect on the engines next cycle and those following.
Development work on VIS systems showed that engines could gain more than 100% volumetric efficiencies.