What rpms do the 215s make boost?

[Jknauer00]

05 rxp ain't seeing positive boost til about 6000 rpms. That about right?

[troyheb]

yes

[skidoochris]

got to have some lag.....they all do
that is why I went with 9:1 pistons and it makes a big differance

[Jknauer00]

Ok then thought I had an issue. Now I will be able to sleep.

[speeder]

interesting. i would have thought it would be on the boost earlier with a supercharger.

[Mighty Mouse]

Thats does indeed seem odd. I would have thought it would have psi way before 6k too. Really only way to know for sure, it to put gauge on output of SC or Intake and see when it come in.

[JFizzleJR]

I don't think it's any coincidence that the engine can't get past 6300 RPM when the supercharger gives out. That's around where boost comes on.

[whittlebeast]

http://www.nbs-stl.com/motec/Motec%20Throttling.png

The red dots on the left plot are WOT. This happens to be a stock 260 motor but the trend will be real similar on a 215 setup.

Per that link, I get 108 KPA at WOT at 3100 (or a little boost)

at 5000 RPM I get about 120 KPA

at 6800 PPM I get about 150 KPA

at 8500 RPM I get about 175 KPA

The point is this stuff is very RPM dependent at WOT. Your numbers will just be a little lower at each RPM.

Andy

[Vern]

Also, if you put a boost nipple on the SC outlet or IC inlet, you will likely measure some boost earlier. The throttle blade restricts how much air/boost gets to the intake, until it is wide open, then boost measured at both points would be similar.

Even at idle, the SC is producing a good amount of airflow, but the TB restricts how much the motor sees. If you could map an idle to WOT snap open, you will see boost registering earlier in the rpms range than if you slowly crawl up the rpm range using the throttle.

Oops, just realized that is basically what Andy is showing ...

[Branden]

yea what whittle and vern are saying is right on. when cruising at 6k rpm the throttle blade is barely cracked open so thats why you dont start seeing boost until then, but blow the pipe off the blower when out riding and at 6k rpm cruising that blower is moving a shitload of air.