10 replies to this topic

[Big_Adam]

yo all.

fianly thought i'd ask all the stupid stuff and find out what the random things in my engine do.....beacuse i don't know. so on with the questions!

1, on my carb there are 3 pipes. 1 for fuel the other is a fuel overflow i belive and then theres thing big black pipe the connect to the carb then buggers off down the right of the engine. what the hell is this pipe.

3, big round metal thingy. theres a big round metal thing connected to a big black pipe. i haven't got a clue what this dose either......or what the pipes for right now. i'll have to have another look to make sure i haven't some how imagend a new mini part but its a big round thing round the back-ish of the engine.

4, the fuel overflow pipe. were dose that exsactly go??

ok thats all the stupid quetions i can think of. on to carbs!!

ok been looking at some twin carbs set ups. it would be the 1st mod to my mini if i decode to get them but i want to know is this. How much extra power would i get. the rest of the engine is pretty much stock even got the original exsaught, and secondly how much would my fual consuption go up. being a student i have to go fast cheaply

cheers folks. sorry about the stupid questions.

[The Matt]

1. Could be a breather pipe I guess, depends on what it looks like? Got any piccies?

2. What happened to question 2? lol

3. Need piccies? Is it an SPi? Could be a charcoal cannister or something.

4. Not much gain from adding twin carbs without other modifications to be honest. Also depends on model of car etc. I would say there are better things to do before adding twin carbs, like a decent exhaust manifold, decent cylinder head etc.

[pikey7]

1, on my carb there are 3 pipes. 1 for fuel the other is a fuel overflow i belive and then theres thing big black pipe the connect to the carb then buggers off down the right of the engine. what the hell is this pipe.

It's the breather pipe. Connecting it to the carb in theory gives it "feedback" about how the engine is running and can "tune" slightly accordingly.

3, big round metal thingy. theres a big round metal thing connected to a big black pipe. i haven't got a clue what this dose either......or what the pipes for right now. i'll have to have another look to make sure i haven't some how imagend a new mini part but its a big round thing round the back-ish of the engine.

Sounds like the flame trap. Does the hose off it go to the carb? It prevents fumes from the carb from igniting in the sump which could then blow a big hole in your engine! by the way, what happenned to 2?

4, the fuel overflow pipe. were dose that exsactly go??

depends on the model. Some go under the engine and just stop (it stops any possibility of a drip onto the exhaust manifod. not a good thing to happen.....). Some go to a charcoal cannister, some go back to the tank.

ok thats all the stupid quetions i can think of. on to carbs!!

ok been looking at some twin carbs set ups. it would be the 1st mod to my mini if i decode to get them but i want to know is this. How much extra power would i get. the rest of the engine is pretty much stock even got the original exsaught, and secondly how much would my fual consuption go up. being a student i have to go fast cheaply

Not a hell of a lot. Your fuelling will be set to give the engine optimum performance and economy. To just change carbs changes the way that the fuel is delivered, but not what the engine needs. You may get an extra 1 or 2hp just having the ability to fine tune a little more, but IMHO, they aren't worth it until you've looked at the head and the exhaust to be able to get the gasses flowing better.

EDIT: Trust me to go and make it nice and neat! Now MMM beats me to it! (just for the record though MMM, SPis dont have carbs...... )

[The Matt]

EDIT: Trust me to go and make it nice and neat! Now MMM beats me to it! (just for the record thoguh MMM, SPis dont have carbs...... )

but you did it sooo much better than me! *

[Big_Adam]

ah right. so twin carbs not a really useful thing to have on my stock little car. oh its a 1982 austin HL mini. also known as El Gordo.

as for 2 it offended me so it had to leave. also my car isn't and spi or whatever that means. its just a simple 998cc beast. grrr.

also that breather pipe thingy is that were those tiny little air filters go. when i flick thro mini mags theres always one with a tiny little air filter on it.

fianly i think the big round thing is connected to the carb breather thing (look at my level of tech language) but i'd have to check to be sure. but i think you are right.

anayway cheers mini mad and pikey, also sorry about no pics haven't got a digi cam.

[pikey7]

yeah, the breather filters go on the end of the flame trap and then the carb end must be blocked off. I've never liked that solution though as the carb wouldn't have a breather connector if it didn't need to have that feed!, but it can be done.....

[Dan]

The breather connection-

It does nothing to tune the engine, it provides no feedback to the carb about the state of the engine and the brather canister isn't really a flame trap. There's quite a lot of air inside a canister and flames would spread through it in no time being as it's got a lump of oil soaked steel wool inside it. All it is is a source of vacuum for the engine. It draws fresh air through the crankcase and other cavities in the engine continuously to extract oil vapour, blowby gas and other nasties out of the casing and keep the internal pressure down and regulated. The air enters the engine through the filter inside the oil filler cap which is why the filler cap should be replaced anually. The canister uses a lump of steel wool to seperate as much oil out of the outgoing air as is reasonable and returns it to the sump. If the crankcase were to pressurize there would be more oil leaks & the oil would get contaminated and thinned faster by the fuel and water in the blowby gas. Positive crankcase ventilation is a good thing.

That's what your pipe is doing Adam, it sucks the crud out of the engine through the canister which seperates most of the oil out of the gasses and delivers it into the carb so that the crud is burned off inside the engine.

And yes, twin carbs don't provide more power by themselves. All any carb will do is give the engine the oppertunity to use the amount of fuel/air mixture it requires to develop power. To make the engine develop more power you need to improve the engine itself, once the engine is improved it will be capable of burning more fuel more quickly so the carb will need to supply more. At that point twin carbs can come into play or improvements to your existing carb, the benefit twin carbs give normally is that you can use two of a smaller size than you would using just one. Smaller carbs are more sensitive to smaller changes in the throttle position so if you use a pair of smaller carbs rather than a pair of large ones you get better respose to light throttle changes and faster response times. Also there is a more direct route for fuel to take into the engine with twins. It's the same as the reasons that people put several throttle bodies onto injected engines and an injector for each cylinder rather than a single large throttle body and central injector.

[Big_Adam]

SO the black house thats connected to the big round metal thing is a breather pipe and a kinda C**p and oild filter.

so is a little breather filter better then beacuse all the gassy C**p from the sup wouldn't go into the engine then insted it would just be realese.

[Dan]

No, it isn't. It's Max Power stylee pseudo tuning junk IMHO. The gasses won't exit the engine under their own volition, they have to be drawn out by a vacuum source. The easiest way to do this and deal with the waste is to use the engine to pump it out and burn it. Top line recers use a tank to catch the C**p the crud that gets blown out by the crankcase pressure but this is by no means as much as gets removed by a positive fresh air system. Race cars need every single BHP all the time so they don't like the unpredictable slight changes in mixture strength the system causes. They can get away with it because they only use their oil for one race and because race engines are so much better looked after than road engines in general. On a road car, positive crankcase ventilation is a much superior solution. It is also required by the construction and use regulations which is why manufacturers fit them, whether or not it is permitted to remove the system is open to debate.

[Sprocket]

The breather connection-

It does nothing to tune the engine, it provides no feedback to the carb about the state of the engine and the brather canister isn't really a flame trap. There's quite a lot of air inside a canister and flames would spread through it in no time being as it's got a lump of oil soaked steel wool inside it. All it is is a source of vacuum for the engine. It draws fresh air through the crankcase and other cavities in the engine continuously to extract oil vapour, blowby gas and other nasties out of the casing and keep the internal pressure down and regulated. The air enters the engine through the filter inside the oil filler cap which is why the filler cap should be replaced anually. The canister uses a lump of steel wool to seperate as much oil out of the outgoing air as is reasonable and returns it to the sump. If the crankcase were to pressurize there would be more oil leaks & the oil would get contaminated and thinned faster by the fuel and water in the blowby gas. Positive crankcase ventilation is a good thing.

Dan, I beg to differ about the 'canister'. Its technical name is a 'Flame trap' it works much the same as the mantle on a gas light. The metal gauze prevents the flame from a backfire reaching the sump irrespective of how much oil it is saturated with, oil burns much much slower than petrol fumes in the crankcase. The gauze does very little to prevent oil or oil vapour from leaving the engine. These canisters are positioned in such places to minimise the escape of oil by baffling by what ever means the location provides.

Under no circumstance connect the breathers to the intake side of the engine without a flame trap or you may, in the most extreme case, experience a sump explosion.

[Big_Adam]

so black breather pipe. leave alone. gotcha. cheers.

hmmmm......do i need to ask any other questions........nope....i'm good.

cheers sprocket, Dan,pikey and mini mad me