11 replies to this topic

[Jackman]

Yes before you say there is a search button i have had a look and everything seems around 50/50 with the carbs.

Im thinking about buying a twin 1.25 carb setup for my 998 stage one.
At the moment its doing 25 to 27 miles to the gallon, (100 - 110 miles to 17Litres) with my single rebuild hs4 carb. There are no fuel leaks its just very thirsty and i cannot find any problems and neither can my dad. No fuel leaks its just thirsty.

I was wondering if i put the twin carb seutp on what problems could i have with it (some say they go out of tune quick, others dont) will it still be just as thirsty?

Also what improvements will i get? Will it be alot smoother at lower revs and pull easier (Struggles to set off from start at the moment).

Also anyone who has one on there 998 can you tell me what its like and any problems you had?

Also any recomendations for filters? Ive seen the pancake ones from minisport which are thin and chrome, does anyone use them?

Thanks

Jackman

[pdaykin]

Twin carbs dont go out of tune any faster than a single - they are just more difficult to set up in the first place and re-tune when they need to.

If you are only getting 27 mpg you wont notice any real difference

But cant say there will be any real benefits to you either. Twin carbs look nice and have a louder induction noise (if you like that - I do !!!!) but wont offer any real performance advantage over an HS4.

Changing to twins can be expensive - cost of carbs, linkages, manifold, filters, set up, etc.

As the original 997, 998, 1071, 970, 1275 Coopers used the twin set up you shouldny get any real problems. BUT you need to make sure they are set up correctly - correct needle, etc. This will probably mean a trip to an expert (rolling road).

If you are buying second hand, make sure they are from a mini (lots of ebayers describe them incorrecty) as the maniflod, angle of the float chamber, needles, springs etc varied between vehicle. Although they look similar, you may find if you get a set up from a midget that it fouls the bodywork and floods on a mini.

In a purely practicable sense, you would probably be better off just rebuilding your existing carb and getting it properly set up

[Jackman]

My carb has just been re-built, i think there is somthing else wrong with it which i cant find.

[minidaves]

sounds like it needs setting up and if your driving it hard 27 sounds about right, get a hif38 and save your money for a nice phat unleaded head

dave

[Jackman]

im not driving it hard at all and it went on RR last month. Already got unleaded head on it. Ill keep with this carb for the moment then, see if it improves in summer.

Also just checked last years figures, last year i was getting 35mpg and was driving the same. Damn ive lost 10mpg... i guess it may need RR again!

[minidaves]

or the valves need reseating

dave

[Jackman]

or the valves need reseating

dave

... Which valves???

If you mean the head its got a really good compression and its unleadded.

[Dan]

You should be getting a lot more mileage than that. A 998 in standard tune should be doing between 40 and 50 MPG on average, and 55 MPG if driving at a constant 55 MPH. It's either got a real problem or it's down to your driving style. The stage 1 kit won't make that much of a difference to the fuel consumption (other than affecting how you drive the car).

What's said above is true, twin's won't in theory give you any more power but they will do the other things you described (cleaner faster pickup, smoother power delivery) as they help to negate some of the problems of a 5 port manifold and have smaller chokes individually than the 1.5.

The people who quote chapter and verse that twin carbs go out of tune faster generally don't have them and have never even seen a pair. As Pdaykin says, they don't. They are just as reliable if not more so than a single in my experience. Also as he says really make sure that you have a properly built set for a Mini. Use the Burlen reference guide to check that all the small parts that are used to setup a carb for different cars (float bowl grommets and lids, jets, springs etc.) are actually the right part number or colour code for a Mini build before you get to the point of putting them on a trying to tune them.

[Jackman]

Its got a real problem Dan, it just drinks and drinks and drinks, i understand i expect alot lower than 40-50 as i get stuck in alot of traffic but its really has dropped, there is no petrol leaks anywhere, its just thirsty. Im out of ideas now.

Thanks alot for that Dan.

[miniboo]

i would go for twin carbs if you can get some cheap.

they offer smoother driving and sometimes even better fuel consumption. I think this is mainly because of the striaghter shot for the fuel to travel into the inlet ports.

[Jammy]

They don't offer better fuel consumption! It doesn't matter how far the fuel has to travel.

[miniboo]

from what i have they can offer better fuel economy...dont shoot me but it is what i have read