Catch Can With Twin Carbs?

[jluc_93]

Hey guys, I just bought a set of twin carbs and manifold for my ke70, should I be running a catch can? If so, how would I go about setting it up?

 

Cheers!

Edited August 21, 2012 by jluc_93

[altezzaclub]

Which carbs? Which manifold? ..and does it have provision for a PCV inlet?

 

I'm running twin SUs on the Lynx manifold & I run the PCV system. It can go into the brake booster line via a T-junct or into the inlet manifold. The other half goes tappet cover-air cleaner.

 

A catch-can just takes one of the tappet cover vents into a coke bottle or whatever, (nicely transparent so you can see what comes out!) and block the other one off. When the motor is running hot vapour comes out, so you can stuff it with wire mesh or pot-cleaners to condense the oil, but when it cools down after you turn it off it will suck air back into the motor. That's why they sell litle air filters to go on the tappet cover vent.

 

You can just run one vent straight to the air cleaner and burn all the fumes, environmentally better than a catch can!

 

In the photo the yellow dots show the PCV line to the inlet manifold, and the green dots show the fresh air line from the air filter.

[ke70dave]

I always enjoy photos of your engineering masterpeice altezza club. that is your SU carbs airbox thing.

 

but yeah, unless the carbs have provision for the pcv, i belive its catch can time.

 

i did the cokebottle trick back when i ran a nikki carby. I think if i did it again i would at least use something that looked mildly original. i can't imagine police would be too kind to a coke bottle with a pipe in it in the engine bay!

 

i think to be strictly legal you need to put the vent from the catch can back into the engine, easier said than done with fancy carbys with no air box though.

[jluc_93]

It's a redline manifold and the carbs are 40mm DCOE webers. http://www.rollaclub.com/faq/images/9/9c/Post-6-1153469779.jpg is the manifold, I'm not too good with stuff like this so I think it has a pcv inlet. I like your setup but unfortunately I don't have an air box. What would be the next best thing? Run a line from the valve into the mainfold then put a filter on the other?

 

Cheers!

[corollaart]

The inlet on that manifold is for your brakes.

[jluc_93]

Ok, cheers guys. Looks like I need a catch can then? How would I go about plumbing it in as I've never done it before.

Edited August 21, 2012 by jluc_93

[styler]

Can do a simple breather as altezzaclub described but pcv is the evolved version of it

 

The wiki saves me explaining it all...

 

http://en.wikipedia.org/wiki/Crankcase_ventilation_system

 

Most catch cans are a failure of something that should work but doesn't.... buyer beware.

[altezzaclub]

Just plumb both those tappet cover vents into a suitable-looking can with a little filter on top.

 

Basically it will leak oil & water vapour out of that filter all the time unless you hook it up to the inlet manifold so the motor can suck some of the fumes in and burn them.

 

So best would be to keep the PCV valve & run that line into the brake booster line in a T-piece and have the other line going to the filtered catch-can.

 

Under cruise and idle the strong vacuum sucks the PCV valve shut so it doesn't suck out of the engine, so the small amount of blowby goes out of the catchcan filter into the atmosphere.

 

Under acceleration the inlet manifold vacuum goes to nothing with the throttle open so the spring in the PCV valve can push the piston back and allow the inlet manifold to suck the greater blowby into the motor. Fresh air then goes IN through your filter and catchcan.

 

I ran mine on the brake booster line for ages until Rob said I shouldn't, but t made no difference when I moved it. Then again, we have different ideas on how a PCV is meant to work too!

Edited August 21, 2012 by altezzaclub