16 replies to this topic

[bsirrell]

I am thinking of either putting a k & N air filter in the standard air box (and making some holes!) or putting a Pancake filter on.

But i am concerned about having to adjust the fuel ratios. How do i adjust this to get it running correctly?

[lrostoke]

You may need to change the needle in the carb.

The mixture screw or nut depending on carb will alter the mixture but thats set at tickover, the profile of the needle is what controls the mixture at different loads.

[Dave33]

I am thinking of either putting a k & N air filter in the standard air box (and making some holes!) or putting a Pancake filter on.

But i am concerned about having to adjust the fuel ratios. How do i adjust this to get it running correctly?

might be a bit of help with more info?
Engine size,any other mods?
What carb are you using?
As said,you will be drawing in more air,so you need more fuel aswell,a change in needle profile will do this.
If its not too radically modified,or you want to keep the induction noise down then i would use the replacement k and n filter for the airbox.
If you have a look at keith calvers website theres an interesting article with regards to this,i will try and put a link up.
Basically,junking the box and running a decent pancake type filter will cause a huge increase in airflow,so setting up so it runs right throughout the rev range is a bit more involved,you may gain a couple of hp right at the top of revs if its setup well.But using a decent airfilter with a modified airbox will be easier on the setup,and will be nicer to drive if used daily/long distance,there are instances where this setup gives more power than a seperate filter.Also if you do want to junk the airbox,make sure you use a k and n stubstack,and the filter allows room for this.
Also having a backplate quite close to the carb intake can upset the fuelling at certain revs,so maybe invest in an iTG foam filter and a decent bellmouth/stubstack if you go this route.
There are some pretty poorly designed airfilters available,so stick to pipercross,k and n,itg and such,they are worth paying more for than some cheap ebay imitation.
hth a bit
dave

[bsirrell]

Its 1998 H 998cc.

No other mods, I thought about maybe a pancake filter as it looks tider.
Or a k&n insert because it will last better and help it run better. I am not iterested too much in high performance, but rather want a nice freindly runner!

I am thinking of either putting a k & N air filter in the standard air box (and making some holes!) or putting a Pancake filter on.

But i am concerned about having to adjust the fuel ratios. How do i adjust this to get it running correctly?

might be a bit of help with more info?
Engine size,any other mods?
What carb are you using?
As said,you will be drawing in more air,so you need more fuel aswell,a change in needle profile will do this.
If its not too radically modified,or you want to keep the induction noise down then i would use the replacement k and n filter for the airbox.
If you have a look at keith calvers website theres an interesting article with regards to this,i will try and put a link up.
Basically,junking the box and running a decent pancake type filter will cause a huge increase in airflow,so setting up so it runs right throughout the rev range is a bit more involved,you may gain a couple of hp right at the top of revs if its setup well.But using a decent airfilter with a modified airbox will be easier on the setup,and will be nicer to drive if used daily/long distance,there are instances where this setup gives more power than a seperate filter.Also if you do want to junk the airbox,make sure you use a k and n stubstack,and the filter allows room for this.
Also having a backplate quite close to the carb intake can upset the fuelling at certain revs,so maybe invest in an iTG foam filter and a decent bellmouth/stubstack if you go this route.
There are some pretty poorly designed airfilters available,so stick to pipercross,k and n,itg and such,they are worth paying more for than some cheap ebay imitation.
hth a bit
dave

[blacktulip]

H 1998? you sure this is right? i thought H was 1991?

[the.stroker]

1998 would make it an MPI for the most part,maybe 1988??
Would be worth booking it in for a rolling road and/or tweaking session at a mini friendly garage if you decide to change anything and your not sure what you are doing!

[E-Tizzle]

mines H at the front and thats a 1990

[bsirrell]

Duh yeah, its H 1990 and 998 cc getting me 98's and 90s confused

[huw_jenks]

I don't think it's worth a Rolling Road setup for a simple mod like this, but can't do any harm either I suppose. It's your money! A pancake or cone filter will give very slightly better performance (provided you use a rampipe/stubstack) than a K&N element in the standard airbox, on a standard engine at least. For that reason I'd say you're better off with using the standard airbox with some holes in the front as the induction noise can get a bit much with the cone type.

To find out which needle you need there's a program you can download called WinSU. Select the info about your engine and it calculates the correct needle. Then to set the mixture and idle you will need either an exhaust gas analyser (most people don't have them, but most garages do) or a little gadget called a ColourTune. It's a glass spark plug costing about £15 that lets you see the colour of the flame in the engine so you can adjust the mixture until you get a nice bunsen blue colour.

[seanmaskill]

hi i also have a 1990 998cc and was considering changing the air filter but all this sounds a little too complicated for me.

the reason i want to change the air filter is to tidy my engine bay up a bit, and a bit of induction noise would by nice, is there a simple way to achieve this with out changing fuel mixtures?

[Neil7744]

this may sound stupid, but you mention setting up the mixture correctly, would this affect performance if margainly out?

Where do you get needles from once calculated?

[Dave33]

hi i also have a 1990 998cc and was considering changing the air filter but all this sounds a little too complicated for me.

the reason i want to change the air filter is to tidy my engine bay up a bit, and a bit of induction noise would by nice, is there a simple way to achieve this with out changing fuel mixtures?

Not really unless you want to damge your engine or at best have poor performance.
There are recommended starting point needles for various specs,which will get pretty close on a stage 1 type engine,its not hard to change the needle.Just fine tuning requires a bit of experience,time to get it spot on.
You wont damage the engine if its slightly rich,but you could if its too lean.
Ideally if you must have a k and n filter,find out what needle will be a good starting point,you wont get the best out of it though,just more noise,and if too lean will probably damage your engine.....
Not really reccomended imho.
Dace

[Ethel]

The standard paper element isn't at all bad - when it's new. I don't think you'd have too many fuelling worries with just a filter swap. If you want whooshy noises then a K&N cone will do the job. We've had standard filter cases (with the extra holes drilled) top the tables on dyno shoot outs.

[seanmaskill]

Not really unless you want to damge your engine or at best have poor performance.
There are recommended starting point needles for various specs,which will get pretty close on a stage 1 type engine,its not hard to change the needle.Just fine tuning requires a bit of experience,time to get it spot on.
You wont damage the engine if its slightly rich,but you could if its too lean.
Ideally if you must have a k and n filter,find out what needle will be a good starting point,you wont get the best out of it though,just more noise,and if too lean will probably damage your engine.....
Not really reccomended imho.
Dace

thanks for the advice im just going to leave it then, its not worth risking my engine just for aesthetic reasons.

[huw_jenks]

this may sound stupid, but you mention setting up the mixture correctly, would this affect performance if margainly out?

Where do you get needles from once calculated?

Well, it depends how 'marginally' out the mixture is. There is definately an optimum setting for the air/fuel ratio, which isn't too difficult to find with a ColourTune. If the mix is too lean then the engine will run too hot, and if the mixture is too rich then you will waste fuel. I think you'd have to be a very lean mixture for a very long time before you did any real damage though. But still, a ColourTune costs about £15 and is so simple to use it's not worth guessing the mixture setting and losing your performance/economy.

I think most Mini shops keep different needles in, but the SU website would probably be your best bet.