11 replies to this topic

[batespeed]

as my cireon ax gt engined mini convertible is off the road just now, [and i cant afford having two boys toys on the road at once], i hit upon the idea of seeing if a twin choke solex off the ax gt could be made to work on a standard mg metro engine. convieniently, i have a 67 mk 2 on the road with just such an engine, and loads of spare ax carb bits. first i cut up a spare ax inlet manifold

till i was left with this

then opened out a spare mg metro inlet to match

then got my mate andy to tig them together and weld on a closing plate on the other side, cheers andy

it fitted and started first time, with an ax throttle cable


it is taller than a SU so there is no clearance between the carb mouth and the bonnet , even without an air filter. so i had to lift the back of the bonnet up for clearance
i did 150 odd miles in it on sunday morning, round the west coast, and it goes like the clappers on full throttle, and cruised smoothly at sixty odd on a very light throttle, so far so good.............but it had a stutter under acceleration that was very frustrating on the slower single track roads

Edited by batespeed, 27 May 2009 - 08:13 AM.

[batespeed]

this is the mini by the way


any way last night i stripped the carb [several times], and eventualy found if i swapped the main jet in the first choke, from a 120 to a 122 and eventualy to a 130 [all i had in my dead carb spares box] it runs far better, and the stutter/flat spot is gone altogether, probably too big now as the fuel gauge seemed to go down faster than normal and the exhaust looks a bit black after a 60 mile run, must see if i can get a 125 or 127 jet...........

it really pulls well now,much more top end than the hif 44 su and k&n filter that was on it before, and its cost me bugger all as i had all the bits in the shed
now to sort out an air filter and make the bonnet fit....................................i'll give it a good run at the weekend to see what the consumption is like

[Deathrow]

Interesting project!

What are the benefits of the AX carb over an SU?

[batespeed]

a carb works by the vacume in the engine sucking air in through a hole [a choke] the air accelerates as its sucked through a slightly smaller hole [a venturi] and petrol is sucked out of
a tiny hole [a jet] the small amount of petrol mixes with the fast flowing air in the correct mixture , is drawn into the combustion chamber and ignited. the air needs to be moving fast at all engine speeds for the petrol to mix properly so idealy you want a small choke for lower revs to keep the speed up, and a bigger choke at high revs to allow in enough air .



a twin choke carb is like two carbs in one,but taking petrol from a common resevoir. the one i'm using is a 32/34 solex which means the first choke is 32mm and the second 34.it is a progressive twin choke carb, meaning that at up to two thirds throttle its running on the first choke only, and over two thirds throttle the second choke opens allowing in more than twice as much air/fuel mixture.



an SU by comparison is a very simple carb, but a very clever design. the choke is restricted by a big piston that slides up and down. the more the throttle is opened the more the vacume from the engine lifts the piston up and the bigger the choke size becomes, untill the piston is fully up revealing the full inch and a half diametre [on a 1 1/2 inch su] there is a tapered needle on the bottom of the piston that rises with it, so the jet that it sits in effectivly gets bigger and lets in more petrol as the revs and piston rise.


bet your sorry you asked now !

[Deathrow]

No, very interested!

I wondered what caused the piston to rise and fall in an SU, I guess it's the two holes in the piston sucking air out of the space above the piston.

(I've got a HIF44 on my desk in bits you see haha).

Looking forward to seeing how this comes along and what gains you get .

[mini_mad69]

Omg where is that road, that looks a brilliant drive


And well done on doing something a bit different.

[RobG295]

Not 100% but it looks very much like the road you come into scotland on where you cross the border (can't remember the name of it!!)...those switchbacks aree awesome!!

[batespeed]

its "bealoch na ba" the pass of the cattle, the highest mountain pass in britain.............. its the road from loch kishorn [sealevel] up throuh bealoch [2054 ft] and down to applecross [sealevel] in 11 miles, google it. its on the west coast of scotlandand about 60 miles from my house i only discovered it about four years ago and have been over it about 20 plus times and it still takes my breath away every time. minis in inverness are planning a run round kishorn, applecross, shieldaig , torridon and back to inverness [about 170 miles of roads that could have been designed for a mini] sometime in july. [ive already done it twice this year myself ]

Edited by batespeed, 28 May 2009 - 07:22 PM.

[batespeed]

ive managed to solve the air filter problem,the bonnet problem and managed to keep it "retro",but im not sure if i like it or not. it was a spare bonnet by the way, so no permanent harm done.

[stardude]

looks cool, but if i remeber correctly, vizard syas, that unprotected filters, above something like 50mph suffer from too much turbulance in the air and stuggle to pull the air through or something like that.

i reckon it would look even more period with a very smooth bonet bulge over it to protect it

[mighty mini jack]

A different filter with an ERA style scoop from ABS would look Retro still, and very nice!

[1987_ParkLane]

Thats a nice little project , wish I had the knowledge to do something like that . Well done, and like the look of the bonnet too .