Aftermarket vs OEM has come up many times in the past. Here's one. But the GDC search doesn't do very well. Try a Google search for "K&N air filter site:gixxer.com/forums/".
Less restriction will allow more air flow! But the engine will need to be tuned for it. In the sake of street riding, not really worth it. And if you do choose to go after market filter, try BMC.. BMC seems to flow better for the Gixxers. Again, no matter, if you're u replace, aftermarket will allow it to be resused. That's the main point advantage. Unless you race, and the 1/10 of a HP matters.
d207gp, go right ahead. I don't have any practical real world experience to prove this. However in general automotive FI design and specifically to the GSXR the intake air pressure (IAP) sensor is designed into the FI system to account for differences in intake air pressure. In most cars this is done with a MAF sensor, (manifold air flow sensor).
The most common compensation would be for altitude change, i.e. being at seal level and then riding up a mountain.
Anything that would affect (averaged) air pressure in the throttle bodies should be compensated for by the IAP sensor. That's its intended purpose and function.
"you want to answer this?" kwaka10r makes sense to me. The OEM filters have a bit more restriction than some aftermarket filters but the aftermarket pass more grit and load up much quicker. If you're fighting for the front of the grid, it might give you another HP or so. But the downsides are significant.
On a related aside, I'd wondered about the perforated metal screen on the OEM filters. The hole size and spacing gives a 51% open area. The associated pressure drop for the screen's total area on a literbike at 13,000 RPM is around .1 inch of water (.0036 psi). That's going to equate to about 1/20 HP. So it's not worth worrying about.
I like when someone puts calculations into the equation (pun intended) to give a better feel for what affects what. Is that on steady state flow? I wonder if the pulsing would change things. Not worth worrying about though, the difference between 1/20 or 1/15 maybe.
I wasn't totally correct, the AP sensor is intended to do altitude mainly (and barometric changes). The IAP is intended to do anything that affects airflow, e.g. ram air (pressure), air filter restriction (vacuum). I never understood why the IAP couldn't be used to do both.
SPL, the IAP sensor will sense more manifold vacuum (i.e a blocked air filter). Its connections come from the intake valve side of the throttle body primary throttle blades.
If the Suzuki OEM mapping compensations are correct the AFR should remain as mapped. However as air flow will be reduced, so will performance.
The AP sensor is for atmospheric correction (altitude and barometric changes).
I agree with your analogy of garden and fire hoses though.
Finally got round to fitting an OEM air filter I bought last year whilst the weather has been rubbish, so I'm looking forward to seeing how she runs with it. It had a BMC one in it.
Love all the technical advise here. Sometimes wish I could meet some of you guys for coffee but being on the other side of the world makes that a bit unrealistic. :lol
I fitted it more for peace of mind, as my K5 is stock on the engine and exhaust side of things. After reading various things, I figured OEM air flow is the way to go with it being stock.
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