Altenative Carbs

[Guest tankybaby66]

Just wonderin what different carb setups people are running? i.e. non standard

Im running a 1 3/4 inch SU carb off a mini on a custom manifold i made myself,

the car is a 205 xs, i swapped it for the solex coz it was dumping petrol in and running way rich and i couldnt get it set up right, i think it was knackered.

the new carb is nice and smooth and uses a lot less fuel but doesnt seem to have as much torque as the solex,

I dont know whether its just my manifold not flowing as well as the original or if its because of the single choke compared to the old twin choke

I had the car setup on a rolling road fitting different needles etc, achieved 64bhp at the wheels, does that sound about right?

Any opinions?

[AndyJ 1]

A stock XS comes with 85bhp afaik so you're losing out somewhere... whether this is purely the different carb, or the manifold, or a combination of wear and tear on the engine as well is another matter

 

The original XS carb is a 34+32 unit giving you an overall diameter of 66mm (2.6 in) when both the chokes are fully open, so i would expect that you would lose some performance with 1.75 in carb.

[Guest tankybaby66]

Ah ok but isnt it 85 at the crank?

[EdCherry 34 1 Cars]

Flywheel*

 

Id take book figures from a manufacturer from the fly personally, but couldn't confirm this.

[AndyJ 1]

I do suspect it is a flywheel figure, cant find anything that says what the wheel bhp ought to be?

[EdCherry 34 1 Cars]

Always going to vary with a wheel output really due to transmission loss. Estimate a 20% to 25% lose and it could be around that (bear in mind this is just an estimation method).

[Guest rmilbank]

Is it true that XR2 Carbs are a direct replacement for the Solex?

 

Is this worth doing?

[johnnyboy666 195 1 Cars]

weber dgv or dgas i beleive are close to fitting, need small mods to the holes i think, and move the cables. not sure if theres any gain to be had by them though?

[swordfish210 20]

If it's the Weber 32/36 DGV then yes it will fit but not without modifications. You need to make a mount to secure the throttle cable, you also need to elongate the mounting holes a bit. Good carb though, i got some good results with one when it was on mine.

[johnnyboy666 195 1 Cars]

after having a browse, the xr2 carb does look like it might fit with little effort, also looks as if it might have auto choke aswell?

[pugdamo 111 2 Cars]

Iv never seen it done but i was told when i had my XS to use the carb of an early MG Maestro,i know it will be a nghtmre to find one but i was told they pretty much go straight on and there is big power gains. Might be worth a search to see if you can find anyone thats done it

[pugdamo 111 2 Cars]

Just done a search and this was the first thing i found -

 

The standard carburettor setup most 205's prevents the engine from producing as much power as it could. Any TU engine (Not sure about 1.0) can take the Solex 34-34 Z2 carb as used in the XS (TU3S Engine.) You will need the inlet manifold from the XS also. Properly set up, power increases can be as much as 10 Bhp. Taking a step further, a rejetted carb can give power gains, and upto 100Bhp is not unknown just from this mod. Expect your fuel consumption to hit the floor!

 

According to Pug Tuning, the carburettors from an early MG Maestro will fit the TU3S and therefore most TU engines, giving a further improvement of about 15 Bhp. (This would give a TU3S 100 Bhp!!)

 

How about that it was true,wish i did it to my old XS now

[johnnyboy666 195 1 Cars]

is that the weber dcnf? rare as hens teeth, and about £300+ new!!

[pugdamo 111 2 Cars]

is that the weber dcnf? rare as hens teeth, and about £300+ new!!

 

God knows what it is,im guessing its as rare as a good Maestro

[snillet 1]

Just done a search and this was the first thing i found -

 

The standard carburettor setup most 205's prevents the engine from producing as much power as it could. Any TU engine (Not sure about 1.0) can take the Solex 34-34 Z2 carb as used in the XS (TU3S Engine.) You will need the inlet manifold from the XS also. Properly set up, power increases can be as much as 10 Bhp. Taking a step further, a rejetted carb can give power gains, and upto 100Bhp is not unknown just from this mod. Expect your fuel consumption to hit the floor!

 

According to Pug Tuning, the carburettors from an early MG Maestro will fit the TU3S and therefore most TU engines, giving a further improvement of about 15 Bhp. (This would give a TU3S 100 Bhp!!)

 

How about that it was true,wish i did it to my old XS now

 

That sounds like a tad on the high expectation side for that engine with those valvesizes i would say, maybe with some headwork but i doubt you´ll reach 100hp with a standard head and inlet manifold ? Or ?

[batespeed 0]

A stock XS comes with 85bhp afaik so you're losing out somewhere... whether this is purely the different carb, or the manifold, or a combination of wear and tear on the engine as well is another matter

 

The original XS carb is a 34+32 unit giving you an overall diameter of 66mm (2.6 in) when both the chokes are fully open, so i would expect that you would lose some performance with 1.75 in carb.

a stock xs is 85 bhp at the flywheel so your figure seems pretty good to me, i dont think you can measure transmition losses as a percentage, does that mean you would lose twice as much from a 100 bhp engine than you would with a 50 bhp engine using the same box ? seems a bit strange to me.........

 

also your maths are wrong, a 34 mm circle plus a 32 mm circle hasnt got the same area as a 66mmcircle......................................................................

......i did this swap in reverse, i fitted an ax gt solex to a 1275 mini (mg metro engine) strange though it may seem i had to drill out the first and second main jets to 1.3mm to get it to run smooth, but it gave very good economy on part throttle and a good bit more power at the top end than the su. it sticks out through the bonnet though............

[tdr_1976 41 1 Cars]

I'm looking at running split 40's next year, as I cant run twins in road rally spec.

 

I had a look at the Weber 32/36 DGV route too, but don't fancy it much. I also had a look into trying to run split Yamaha R1 Motorbike carbs too, still trying to come up with an answer for that one.......lol!

Edited February 4, 2010 by tdr_1976

[batespeed 0]

I'm looking at running split 40's next year, as I cant run twins in road rally spec.

 

I had a look at the Weber 32/36 DGV route too, but don't fancy it much. I also had a look into trying to run split Yamaha R1 Motorbike carbs too, still trying to come up with an answer for that one.......lol!

are split 40's not classed as twin carbs then ? there is still two of them , but with one barrel of each carb removed. a single 40 or 45 would be better , would it not ?

 

i was thinking about twin kehin's of a 1990 odd civic, they are more comonly used on bikes but were used on the 1.4 civic and some triumph acclaims, they were fitted with two big rubber tube connectors onto the manifold the same as bike carbs too, so it wouldent be to hard to make a manifold for a mini.

 

they NEVER needed adjustment on a civic or acclaim either, fit and forget (unlike SU's)

[RossD 43]

The standard carburettor setup most 205's prevents the engine from producing as much power as it could. Any TU engine (Not sure about 1.0) can take the Solex 34-34 Z2 carb as used in the XS (TU3S Engine.) You will need the inlet manifold from the XS also. Properly set up, power increases can be as much as 10 Bhp. Taking a step further, a rejetted carb can give power gains, and upto 100Bhp is not unknown just from this mod. Expect your fuel consumption to hit the floor!

 

According to Pug Tuning, the carburettors from an early MG Maestro will fit the TU3S and therefore most TU engines, giving a further improvement of about 15 Bhp. (This would give a TU3S 100 Bhp!!)

 

This quote about the maestro carbs is from my old website iirc, which hasn't been updated in years. I agree it's a bit on the high side for an estimate. I wrote that back when I was young and impressionable

 

I would take the site down, but I'm no longer with that ISP and so have been locked out of it.