Tuning Cam Cover Breather Help SPI 40mm TB

[Jd801]

Hi all.
Fitted my new 40mm throttle body last weekend courtesy of sparky5 and absolutely love it.
Highly recommended to all. Made a huge difference and the workmanship is top notch.
Just a quick question about it.
When I was running the standard TB I had blocked off the pipe that went off to the old airbox junk and blocked off the pipe that goes from the cam cover to the TB.
I left it like this when I fitted the 40mm but noticed that when coming to a stop the sei was trying to stall. After having a catch up with Cento186 today we decided to unblock it and my sei appears to run even better and slightly faster.
Have I been suffocating it for all this time?
If I've not been suffocating it can someone explain the purpose of that breather to the TB.
899 Bob fitted and k&n filter pointing down near nearside headlight by the way.
Sorry it's long winded.

 

[fingers99]

I suspect that the connection to the cam box breather (the smaller of the two pipes) is important.

 

[Jd801]

Can any one elaborate on that a bit more?

 

[fingers99]

Cam cover breather pipe bifurcates into two. Large tube goes to inlet manifold, small to the TB. See here.

Having said that, I'm unsure of exactly why that connection is needed.

 

[Jd801]

That's what I'm getting at as the large tube now runs off to the wheel arch and the small one that connects to the TB I had blocked up as I to do not understand why you would want dirty engine air sucked into the TB

 

[fingers99]

I'm unsure as to why, too! Still, if the engine likes it, go with it.

For the other, larger, exit pipe, the only sensible solution is to return it to the air intake (via a catch tank if you like) -- neatest way is an air line fitting on top of the bob. Anything else is a violation of construction and use regs (and will also get you flung off any race track in the country.

 

[David C]

It pulls air through that small pipe when the throttle is closed.
If you've blocked it, that is why it is stalling.