Someone did a test years back where they ran standard, cones, papers, everything under the sun, and then no filter at all.
I think paper standard was 1bhp off no filter at all at 150bhp tune.
Standard air-box is an essential, it features ram air intake effect so at higher road speeds you get positive boost pre-filter, so it's as if there isn't a filter there.
It also feeds super cool air from the front air-dam, so again that is very beneficial.
I've seen cones in summer, even after driving for 5 mins, sucking in at 20deg above ambient. Even with that little duct pointing at the cone, it makes no real difference as hot air flows back from the radiator when moving and saturates the engine bay with 'warm' air totally offsetting the blow in from the OEM duct. When not moving there is no flow so it's still hot.
Ergo, 20deg ambient + 20deg = 40deg IAT.
So vs a standard airbox which is 20deg ambient + 2deg = 22deg IAT.
273 + 22 / 273 + 40 = 0.94 = 94%
So in theory with a stage 2 at 150bhp with standard air-box to a cone sucking in hot air, you get 94% of 150bhp, or 141bhp.
My pipercross panel even oiled/cleaned often used to have big particles evident post air filter, so I went back to paper. You have a MAF sensor and an expensive turbo down-stream!
K&N panel seem a bit better but not sure on filtration. Unless you clean/oil often (most don't), then it'll be letting particles through. If you do oil/clean often then oily MAF is probably gonna be an issue for longevity.
My 2p, save your money and stick to paper. Then spend the saved money on something that WILL benefit your performance. Like better oil, more frequency servicing etc...
If someone can show some numbers to prove a panel is better, despite it's obvious drawbacks, then I'll change my mind
Dave
The MAF sensor range is irrelevant really. The big issue is when it starts restricting flow too much. I expect it's an exponential efficiency falloff.
The function of that is more to do with physical dimensions more than anything (ie, fluid dynamics)
The standard airbox acts as a ram air intake at speed so you alleviate the issue of the MAF drag to some extent.
You also probably see the intake pipe down to the turbo itself acting as a restriction to intake flow before the MAF sensor I'd say. So changing the MAF might do nothing if that part is also starting to restrict you.
I think the late C5 HDi110's had a bigger MAF sensor (both physical and reading range calibrated)... I think.
I'd go look at something like a 123d BMW and see what power they run remapped, and how big their MAF sensor is, and if it runs based on the same signal return.
The best test really would be to test pressure in the pipe just before the turbo compressor intake (tap just before the bend where it's been straight for a bit)...
If it's positive, then don't worry about anything up to that point.
If it's negative, then work back to the airbox and see where it starts being negative!
Chase away the negative pressures pre-turbo and you'll get efficiency.
Dave
I think paper standard was 1bhp off no filter at all at 150bhp tune.
Standard air-box is an essential, it features ram air intake effect so at higher road speeds you get positive boost pre-filter, so it's as if there isn't a filter there.
It also feeds super cool air from the front air-dam, so again that is very beneficial.
I've seen cones in summer, even after driving for 5 mins, sucking in at 20deg above ambient. Even with that little duct pointing at the cone, it makes no real difference as hot air flows back from the radiator when moving and saturates the engine bay with 'warm' air totally offsetting the blow in from the OEM duct. When not moving there is no flow so it's still hot.
Ergo, 20deg ambient + 20deg = 40deg IAT.
So vs a standard airbox which is 20deg ambient + 2deg = 22deg IAT.
273 + 22 / 273 + 40 = 0.94 = 94%
So in theory with a stage 2 at 150bhp with standard air-box to a cone sucking in hot air, you get 94% of 150bhp, or 141bhp.
My pipercross panel even oiled/cleaned often used to have big particles evident post air filter, so I went back to paper. You have a MAF sensor and an expensive turbo down-stream!
K&N panel seem a bit better but not sure on filtration. Unless you clean/oil often (most don't), then it'll be letting particles through. If you do oil/clean often then oily MAF is probably gonna be an issue for longevity.
My 2p, save your money and stick to paper. Then spend the saved money on something that WILL benefit your performance. Like better oil, more frequency servicing etc...
If someone can show some numbers to prove a panel is better, despite it's obvious drawbacks, then I'll change my mind
Dave
(05-01-2013, 05:22 PM)SRowell Wrote: I swear I heard somewhere that the 1.6 HDI MAF sensor had a greater range?
The MAF sensor range is irrelevant really. The big issue is when it starts restricting flow too much. I expect it's an exponential efficiency falloff.
The function of that is more to do with physical dimensions more than anything (ie, fluid dynamics)
The standard airbox acts as a ram air intake at speed so you alleviate the issue of the MAF drag to some extent.
You also probably see the intake pipe down to the turbo itself acting as a restriction to intake flow before the MAF sensor I'd say. So changing the MAF might do nothing if that part is also starting to restrict you.
I think the late C5 HDi110's had a bigger MAF sensor (both physical and reading range calibrated)... I think.
I'd go look at something like a 123d BMW and see what power they run remapped, and how big their MAF sensor is, and if it runs based on the same signal return.
The best test really would be to test pressure in the pipe just before the turbo compressor intake (tap just before the bend where it's been straight for a bit)...
If it's positive, then don't worry about anything up to that point.
If it's negative, then work back to the airbox and see where it starts being negative!
Chase away the negative pressures pre-turbo and you'll get efficiency.
Dave
