ron wrote: ↑Tue Feb 06, 2018 8:01 am
Ian,
If you are thinking of ordering a set of these, please order 2 sets as I could do with a set.
Thanks.
Hi Ron,
After stripping the inlet side of engine bay I have decided against these pipes. When I removed the inlet plenum, I was rather pleased to find that there were long intake stacks, rather like those on the DCOE 45s within the K&N filters on my Seven. IE, inside those corrugated rubber tubes between the plenum and the throttle bodies, there are long tapering, rolled edge alloy tubes that extend from the throttle bodies into the plenum.
So, the stock corrugated tubes do not act as an intakes path as I thought, but are simply required to both seal the intake to plenum interface and cater for flex between the fixed airbox and engine moving under on/off throttle (hence the corrugation). They therefore cannot improve airflow, this is controlled by the throttle stack tubes which extend from the throttle bodies to a point just inside the plenum, not hindered by any turbulence that would result from air passing over the corrugations in the rubber tube between the plenum and throttle bodies. The throttle stacks effectively isolate the intake path from the corrugated rubbers.
However, the manufacturer claims over the significance of
"Pushing the intake manifold away from the engine and increasing the distance between the velocity stacks and the back of the manifold wall, aids better flow characteristics and slightly increases the manifold's volume to increase power." is open to debate and personally I would really like to see the before and after power runs before shelling out $200.. From my previous experience with tuning side and downdraft carbs, there may be a slight increase in torque (rather than power) achieved by effectively extending the length of the intake stack when moving the plenum a little further away from the throttle bodies, but I suspect that to truly gain any small torque increase I would need to increase the length of the stacks to match but there would be a drop off of peak power as a result. As longer intake stacks are not available, to my knowledge, I will stick with the standard setup.
If I really wanted to increase power with mods to the inlet side it might be worth considering increasing the intake plenum volume, but to make any significant difference the volume change would need to be more that these pipes provide, EG by modifying / creating a larger plenum. They do look good though, so I would only fit them from an aesthetic POV, rather than performance, but I am tying to remain as stock as standard.
Having said all that, the corrugated hose between the Airbox/MAF and plenum should perhaps be more of a focus. This is a pipe that does directly affect airflow as it carries air between the MAF and the Plenum and there is no isolating tube inside this one. However, once the air enters the plenum it can be at significant velocity so there will be considerable turbulence as it hits the back wall and swirls around so fitting a smooth-walled intake pipe may have little, if no effect.
If I really wanted to improve performance I might consider cutting/welding to increase the volume of the plenum considerably (to improve power) and lengthen the throttle stack pipes (to increase torque) but I suspect the gains would not justify the effort and expense. Please excuse my rambling. I have been out for a colleagues leaving party and have one or two more IPAs than normal...
Ian