Technical Flappy thing in airbox.

[petel]

The hot air regulator ( Flappy Thing ) is not there specifically to prevent icing of the carb, though as Jim states, this is a factor.

As we all know, the object of the exercise after starting from cold, is to get the engine up to its normal working temperature as quickly as is possible. This is where the regulator comes in.

When cold, the actuator is at rest and the flap is in the open position, this allowing heated air from the exhaust manifold to pass into the airbox.

The actuator, which is a sealed unit and works on the same principle as the engines thermostat, then reacts as the engine gains temperature, pushing its shaft out to progressively close the flap as the engine reaches its normal working temperature.

As the engine cools down, the actuator slowly returns to its rest position, opening the flap ready for the next cold start.

This is the same function for both carb and SPI engines.

The usual failure of these units, is the shaft linking the actuator to the flap breaking,

Rgds.

 

[CLXCraig]

Thread closed! but I think ti should work the otherway.. when it's hot flap open for cold air.. when cold shut and air is from manifold

 

[petel]

Yes, Sorry Craig, you are quite right.

Should be normally closed, not open.

However, the basic operating principles are as described.

Rgds.

 

[CLXCraig]

Cool, now we all know!

 

[purple haze]

Petel is the man!!!....As ever..Perfectly explained...:worship:

 

[firstcar-Y10]

Can I throw my flaps away then!?

I'm gonna have a look at this tomorrow if the weather is ok...

Luke.

just reinstated that flap after running for a long while without and I have to say it has made the engine a lot happier in the colder weather. Probably worth trying to get a second airbox to rip the mechanism out of and open up the cold air intake a bit and block off the hot, that's what I've got to put back in for the summer. Probably leave alone until the weather stays warm.
if you want to know it it's working right (which they frequently don't) the flap should be set to block the cold intake if you take the airbox off a cold engine. Dump it in a bowl of hot water for a few minutes and check again - the flap should now have opened up.
Andrew.