Secondary Butterfly Questions

[Evil Mitch]

Exactly! simply removing the secondaries does not change the fuelling. If the ECU thinks that the throttles are opened 60% then it will supply the appropriate mixture for that. Using TuneBoy or Tune ECU then the proper mixture can be supplied . Having said that I know there were quite a few that removed them and reported power gains with no ill effects.

or get the bike dyno tuned by a pro and u know u are getting the fuel u need

 

[CanberraR3]

I recall comments by HellFire (RIP) and others that with 'standard' (incl TORs) tunes, the secondaries change a/f mix by adjusting air flow ie that there was no extra fuel but rather a choking effect to make the mix richer. Removing secondaries therefore should make the bike run leaner at certain points in the range (when secondaries would normally not be 100% open), which you overcome with PC/Dobec/tune. The extra oomph comes because of the less restricted flow and more fuel when you need it, and the extra responsiveness comes because there's no set of butterflies to have to open when you turn the throttle.

 

[Evil Mitch]

I recall comments by HellFire (RIP) and others that with 'standard' (incl TORs) tunes, the secondaries change a/f mix by adjusting air flow ie that there was no extra fuel but rather a choking effect to make the mix richer. Removing secondaries therefore should make the bike run leaner at certain points in the range (when secondaries would normally not be 100% open), which you overcome with PC/Dobec/tune. The extra oomph comes because of the less restricted flow and more fuel when you need it, and the extra responsiveness comes because there's no set of butterflies to have to open when you turn the throttle.

exactly +1 on Richards comment

 

[CanberraR3]

OK Mitch, that's 1, but you're still significantly in deficit.

 

[Hardy]

Exactly! simply removing the secondaries does not change the fuelling. If the ECU thinks that the throttles are opened 60% then it will supply the appropriate mixture for that.

Good point!

 

[Rayvin]

Since I switched back to stock pipes with cat bypass I've been running tune 20220. The only changes I made to it in TuneECU were:
1. speedo adjusted to -6%
2. rev limit to 6300
3. top speed to 299 (like I needed to do that)
4. opened secondaries to 100% all gears, all rpm
Having the secondaries at 100% and then going back to the original settings in tune 20220 is what I've been playing with. From the info I've been getting here, it sounds like the reason I feel less power when I set the secs to 100% is because I'm running too lean at points in gears 1-3. And, since I'm keeping this exhaust/intake setup for now, I'm either better off going back to stock secondary settings or adjusting the a/f ratios to match the always opened secondaries. Does that sound right?
If this is right, is there any chance anyone has a map for stock silencers/cat bypass and secondaries disabled (map 20220 with a/f ratios adjusted for disabled secs)? Figured I'd ask before I reenabled the secondaries.

 

[Triple Trouble]

I would think that if you tell the ECU to open the secondaries 100% then it should know to supply the correct fuel mixture assuming the map installed is the right one. The mixture going lean would be from the ECU thinking there are secondary butterflies installed and that they are only partially opened when in fact if they are removed and it is flowing too much air for the amount of gas being injected.

 

[Rayvin]

OT to TORocket-is your '73 Norton Commando the 850, 750 or the John Player model? I used to drool over pics of them in bike rags as a teenager and when the 850 first showed up in '73 I knew that was the ride for me. Owned and ridden lots of bikes since, but never did get one of those beauties...

 

[Triple Trouble]

It's an 850 sometimes as a red Roadster and sometimes a black Interstate. I've owned it since '78 and I still drool over it....

 

[Rayvin]

It's an 850 sometimes as a red Roadster and sometimes a black Interstate. I've owned it since '78 and I still drool over it....

Got any pics?