just having a flick through the s2a worksop manual and came across a thing called the "hot spot flap." it's some spring loaded, counter-weighted thingymyjig in the exhaust manifold but the manual doesn't explain what the thing does. could anyone tell me what it does???
thanks.
It allows heat front the exhaust manifold to stop the carb icing up.
HTH
what causes it too ice up?? apart from the cold obviously. when it ices up, does the fuel jet ice over or does it just generally get crappy??
The air entering carb is cooled due expansion as it goes thru the venturi. I don't know where the ice forms but symptoms are usually a very high idle speed which suddenly drops to normal as the carb warms up again.
ahh, lower air temp due to expansion. didn' think of that. thanks adrian.
On or around Sat, 20 Sep 2003 09:02:30 +0100, "Adrian England" enlightened us thusly:
also can cause loss of power.
happens most often on moist days with low ambient temperature, near freezing
- doesn't happen if it *is* freezing, as the air is then dry. Dragging the air around the exhaust manifold warms and dries it on the way to the carb.
Not all carbs ice the same way, some can form ice around the main jet outlet, which has a detrimental effect on the running :-)
ahhh, you learn something new everyday dont ya? just when i thought i had the old internal-combustion engine under wraps, something else pops up that you never thought of. for such a simple idea (air and fuel go in, air and fuel get compressed, air and fuel is ignited, makes a piston go down, burnt air and fuel is ejected) there are so many other factors. cam-timing, ignition timing, yadda yadda, that can have such a huge effect on the operating of the thing. it really is amazing. no wonder so many people get addicted to them.
excuse my ramblings please, just really amzes me. mum and the girlfriend really aren't interested and constantlty telling me to think of something useful to get excited about, but anyway.
sammy.
On or around Sat, 20 Sep 2003 20:58:05 +1000, "samuel mcgregor" enlightened us thusly:
not to mention long term effects like making the valves etc from the wrong material...
then there's stuff like tuned exhausts...
Also due to the crap petrol we use here. Bikes are particularly susceptible to it (had a carbed GT750 that even with carb heaters used to get very lumpy on cold mornings, stalling at anything under 2k revs) which was blamed on "British petrol" .
well, what i listed there is really just the tip of the iceberg isn't it?
All carburetted petrol engines have some method of heating the intake manifold to help vapourisation and to reduce the incidence of ice formation. (Ice forms due to the temperature drop caused by the evaporation of the petrol, if there is enough water vapaour in the air and the temperature is right - depends on the engine, but usually 0-20C or thereabouts) In the four cylinder Landrovers this heating takes the form of joining the intake and exhaust manifolds together. Early engines have a moving flap that directs the exhaust against the junction when cold, but as the manifold heats up a bimetal strip moves it to deflect the exhaust away from the junction. This is the hot spot flap you refer to. It is not fitted to later engines. I'm not sure when it changed, sometime in 2a production I think. JD
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