Big pipe vs weenie pipe

[br2715]

Am planning to race this weekend and the money race is the predator pro class. Which is box stock predator, gov removed, stock air box, top plate and fuel pump, any clutch and any pipe. Then There is an EL class they are also running and it’s same rules except have to run weenie pipe. Was thinking about runnng both classes. If I do I will have to put the weenie pipe back on to do so. Would rather have a better advantage in the money race but if the pipe is not going to make that much difference I will swap it back to the weenie pipe. Does the bigger pipe make that much of a deference on this class?

 

[racing promotor]

I'm no engine guy, BUT big pipe makes a big difference in any class.

 

[Dover Power]

As Ken said.. HUGE difference.. Kill you the second the green flags waves... Swap the pipe back and forth.. BUT you might need a slight gear change as well.

 

[br2715]

Thanks ken and Jerry!

 

[racing promotor]

Thanks ken and Jerry!

Good Luck !!

 

[RCJ]

With a wienie I'm on a .031 jet. I worked on a big pipe Motor in the summer. I'm thinking a .037 jet and a little less than 1hp better.

 

[alvin l nunley]

With a wienie I'm on a .031 jet. I worked on a big pipe Motor in the summer. I'm thinking a .037 jet and a little less than 1hp better.

.031" to .037" is almost a 50% increase in flow, can that be right?

 

[racinnut15xm]

He may of went from a stock air box to a aftermarket

 

[RCJ]

Yes .037 was a open filter also and this was the middle of the summer. A .037 jet just started loosening power. I've been paying attention to the dyno weather station this year. In the summer it shows around 4000ft density alt. and I will be on a .0294 or a .030 jet. This month I am getting -130 to 400ft and .032 to .031 jets .this a wienie pipe and stock box 212

 

[alvin l nunley]

.030" to .032" is a 13.7% change in area. Longacre cells an air density gauge and they say 1% change in air density calls for a 1% change in jet area. Here in liberty Hill Texas, I've never seen a 13.7% change in air density and I've tracked it for 3 years. I don't know how to convert your numbers to air density. Maybe you can help me on that?

 

[95 shaw]

Changing the airbox to a freer flowing filter changes the fuel signal to the jet.
Like turning the choke off. Put your air density gauge inside the air filter.
Air bleeds and emulsion tube also factor in.
Changing the pipe also changes the fuel signal effects on a 4 cycle engine.

Air density is only part of the equation.

 

[racinnut15xm]

.030" to .032" is a 13.7% change in area. Longacre cells an air density gauge and they say 1% change in air density calls for a 1% change in jet area. Here in liberty Hill Texas, I've never seen a 13.7% change in air density and I've tracked it for 3 years. I don't know how to convert your numbers to air density. Maybe you can help me on that?

https://en.wikipedia.org/wiki/Density_altitude

You have more free time than I do. Take a look and tell us what the data supports