New billet parabolic velocity stacks now available

[LittleRedSpirit]

if they fit, then yes it would be a lot better.

[LittleRedSpirit]

What are the prices for those playing at home?

[Sam-Q]

If you have nothing inside at all then it should make a big difference. Do you have a blacktop? I also have 30mm as shown with this Mekaru airbox:

[McLEVIN]

I have silvertop on a 16v

[Sam-Q]

Right now I don't have anything to suit a silvertop that's short. So unless you can fit a 50mm in there as per your original request then it would be a real long wait to get something custom made.

How is the internal room, have a photo handy?

[Admiral Ackbar]

Not necessarily, you need to check clearance between the ram tubes and the walls of the airbox (both opposite and sides). Try for 1.5 diameters clearance, any less than 1 diameter will really hurt performance.


Sam: Inlet length is far more important than fiddling with the radius of the entry. If you look at superbike and f1 engines, they nearly all have a straight tube with a single radius on the end. Admittedly this about all they can fit, but it shows that a basic design works very well.

From memory a bigport inlet port is about 80mm + TTT quad adapter 60mm + blacktop throttles 75mm + 50mm ram tubes = about 265mm, which is a lot shorter than ideal for an engine revving to 9000rpm.

[Sam-Q]

Joel I completely agree with you that length plays a more critical role. As mentioned previously these where designed to be the best optimisation of a bad compromise where we just can't fit longer. The inlet design does make a real difference so it shouldn't be discounted. Quite a few times now I have been envious of all the intake room available in the left hand drive cars.

[Admiral Ackbar]

What you could do is sell 2 pairs of different lengths, so have cylinders 1 & 4 short and cylinders 2 and 3 long. One of my bikes had this arrangement to broaded the torque curve, and it certainly seemed to work. Definately need to have individual cylinder trim though.

[Sam-Q]

Yes the trim is the problem, for the people that do have an ecu to support significantly fewer again would be prepared to go to the trouble and cost. No argument about the theory though, spreads the tuned point.

Although hard to make out those look like they have a variable radius inlet.

[Frak]

Hi Joel, I tried this on a BEAMS, can't exactly remember what the outcome was, will have to look back at dyno curves. But it didn't work. I own a Honda RC45 which is fitted with a HRC kitted engine, they run 20mm and 40mm ram tubes on the throttle bodies and as you said this is common on motorcycles. Infact a number of years ago, I tuned a WEST race car fitted with a zx10R engine, one of the experiments we did was to run it with the standard 2 long/2 short ram tubes, then fit 4 short, then 4 long.