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MG Midget and Sprite Technical - Upgrade to K&N Filters

Hi. I am going to upgrade my standed filters with K&N filters but I have read that I might need new needles and the on the carbs to make the car run richer. Could I just adjust that on the carbs? How will I now if it needs to run richer apart from looking at the spark plugs. Will the car run badly? Thanks
N Allen

Now you have thrown the dog in the hen house!

There is debate on the actual working of K&N filter.
So it might spark some debate.

As for the adjusting yes you can do it!
Just fit the filters and adjust the carbs a bit richer (how depends on what carb)
And check the plugs.

If you want it optimized go to a roling road and have it set up
Onno K

Sorry it is a 1979 1500 midget with HS4 carbs
N Allen

If you are just upgrading to K&Ns on a 1500, with no other mods, then you will NOT need different needles.

Just richen up the carbs by a flat and a half.
Deborah Evans

If there is no need to change the needles there is no change in flow therefore no increase in bhp therefore no reason to fit them.

If the flow increases if the K&N filters are less restrictive than the standard filter and casing setup then you will need richer needles. Standard filters/casings tend to be a little restrictive which is partly to keep induction noise down. This restriction to flow increases the pressure drop over the jet which makes more fuel lift up. Reduce the pressure drop over the jet and less fuel lifts up so you need a thinner needle to allow more fuel to pasOften people put K&N replacement filters inside originals casings. The casing is usually the restriction not the filters so no change in needle is required.

Peter
P Burgess

dog in the hen house indeed Onno..

Now we have had the opposing expert opinions lets expand and discuss further.

On an otherwise unmodified engine would setting slightly richer on standard needles not supply the extra fuel required?
If the filter (or housing) is the main restriction and fitting a K&N removes this with a resulting increase in air flow, does the flow profile over the rev range remain the same eg x cfm at 1000 rpm and y cfm at 4000 or is there more flow at higher rpm because of the lower restriction?
If the flow profile changes, would a different needle be required to maintain 14.7 at the higher rpms's or will the carb compensate via the piston height?

I guess all this is guess work and a RR session is the only way to be absolutely sure...

MGmike
M McAndrew

In a sense, everyone's right. A small increase in flow / loss in pressure drop may be compensated by lowering the jet slightly, or slightly thinner needle(s).

We're probably looking at *up to* 5 percent change, which isn't really that large and well within the deviation of normal carb operation.

You might argue that an older carb probably has already worn it needle/jet combination esp. for low throttles over the years anyway (and has probably been adjusted slightly to compensate).

A RR set-up would improve most engines whether the engine is standard or not - so is never a bad thing ince in a while.

A
Anthony Cutler

Into the mix we go. :)

I put K&Ns with internal stubs, on my standard 1275, and noticed an immediate improvement.

I put the K&Ns on, before I started modifying the engine, and previously I had the bog standard air filters and casings.

I remember I altered the mixture slightly, and had to set tickover again. I kept the same (worn) standard needles.

2 possiblities.

1) My air filters were so full of crap (very possible) that anything I did would have been an improvement.

2) The KNs are much better than the standard setup.

I have no idea how much improvement there was, as I have never RR'd. But it was more than my imagination that there was an improvement.

But irrespective of the above.

1) They look nicer.
2) Even if you don't clean and oil the KNs as often as you should, they definately perform beter, than if you neglect the standard set up in the same way.


Lawrence Slater

PS to:
2) Even if you don't clean and oil the KNs as often as you should, they definately perform beter, ----

--- than if you neglect the standard set up in the same way. ---

By which I mean, regular dusting/replacement of the standard filter.
Lawrence Slater

2) Even if you don't clean and oil the KNs as often as you should, they definately perform beter, ----

No they don't....
I could repost all the links with tests that show that they don't perform as well as acclaimed, but I'm not.
I'm not against K&N's, but if you have a standard filter housing just don't bother, put in paper.
If you live in a dusty enviroment, like a desert, never ever fit K&N.
Alex G Matla

Alex,
post the links

excluding the original pan and paper, as they never came with the car, what is the best filter?
Nigel Atkins

Oiled foam
If kept up.

But I am sure someone will disagree
Onno K

had those, horribly messy to me, manufacturer about a mile from me (or used to be)
Nigel Atkins

Nigel, got the links favoutitized, but at work. Will post them saturday.

And K&N is fine, I was merely stating that they aren't all as advertised. I have a cotton filter, but a cheaper knock-of. If you have non standard carbs with large stacks on them, they are a good solution.
Alex G Matla

K & N's sound faster. ;-)
Guy

N Allen,
with K&N pancake filters the MGOC (at least) recommend the use of (short) stub stacks for improvements - http://www.mgocspares.co.uk/acatalog/MGOC_SPARES_K_N_773.html

the K&N provide for a nice sound and even better with the stub stacks

Thanks Alex, I'm open to persuasion on most things

I’ve got standard (new now) carbs with the very short stubs stacks and chrome pancake K&N filters

I suggest side by side tests, I’ve offered before to lend my K&Ns and stub stacks, they only unbolt
Nigel Atkins

Alex, you selectively misquoted me, by leaving out my qualifying remark. :)

"2) Even if you don't clean and oil the KNs as often as you should, they definately perform beter, ----
No they don't...."

I actually said, --- Even if you don't clean and oil the KNs as often as you should, they definately perform beter, ---- --- than if you neglect the standard set up in the same way. --- . By which I mean, regular dusting/replacement of the standard filter.

I often find that ACTUAL experience, gained by long time drivers/owners, is ignored and unfairly refuted, buy "facts". For example, lab tests of components, such as airflow tests on filters.

I have experience of the fact, that when I installed my KN's, even if I didn't clean and oil them as often as the good book says I should, they still perfom better than a neglected clogged original paper filter.

As evidenced by, the amount of visible soot that used to appear on my spark plugs when I had clogged paper filters, as opposed to the more or less constant colour of my plugs, irrespective of my cleaning and oiling my KNs or not.

You may quote all the facts and figures you like, but that is my experience.

My comparison is between, an uncleaned and not re-olied K&N, and a dirty original paper filter. And in that repsect, I reckon KN are better. :)


Lawrence Slater

You need about 2.5 times the area of foam filter to flow the same as paper or K&N. Foam seems to degrade and go shabby quickly, foam seems to hold lots of petrol vapour and go FABOOM!!!! now and then :)

Peter
P Burgess

I wonder if all this discussion has put the OP off(?)

more (hopefully) information now

K&N put subject to conditions you may not need to clean and 'recharge' them for 50,000 miles (IIRC they used to say 100,000 miles)

some Viper owners with uprated engines insists on once a year cleaning and ‘recharge’ to keep maximum performance, now I'm guessing there would more noticeable difference in doing this with a V10, 8 litre and uprated engine than with the Spridget engines

IIRC K&N is a bit like Dysons the drop in performance from new is less than (most? some?) of their competitors, the other filters clog up more with the K&N keeping a more level performance er, level - well that's the way I remember it from years ago anyway

when you want or need to then K&Ns are very easy to clean and 'recharge' at about £2-3 a time in K&N materials and nothing like the dripping syrup I've experienced with the one foam type

regular changing of paper filters I’ve always found helps, they use to be so cheap to buy one for one of my (regularly used) classics that I changed them every 6 months with the oil change, placebo or not the engine felt it went better for it

ETA: Peter posted whilst I was typing - my use of foam filter was with a different car with the filter remote from engine bay as such

and I swapped it to a K&N when I found they were available for that model - no more syrup on the hard standing and fly bodies
Nigel Atkins

had k n filters on my mgb when i bought it 5yrs ago and never ran right.would not tick over very well and at 3000 revs would hold back. whatever i done to adjust carbs made no difference. then someone on this board told me that when fitting these filters carb needles should be changed as well.changed from standard for mgb AAU needles to AAA and car now runs like it should. ticks over all right and good through all revs.

1970 mgbgt
1975 midget
bob.
trebor

>>would not tick over very well and at 3000 revs would hold back

This sounds like they were on upside down, and the carb vents were blocked. BTDT!

A
Anthony Cutler

WOW what a lot of mixed response thankyou. I have them and are fitting them tomorrow. If by the of chance I did need different needles how would I know. How would the car be running?
N Allen

Nigel
Do you realy think you would notice 50 horses went missing when you have a couple of hundred left...
Or when you have 50 left from the original 65
Onno K

Onno, you'd better ask Ally and Rach. They often talk about horse flesh. :)
Lawrence Slater

N Allen you'll know by driving it if at any point after the car is fully warmed up that at some points over throtle and rev range things can be improved with the choke

Onno,
depends on the driver

20% loss yes you would notice think the Viper as standard are a bit more than 250 let alone the tricked up ones

don't think you'd notice an extra 1 or 2 or 3 when your on 50

it's power to total weight of occupied car too of course

I always think it's about how the car feels rather than any figures on paper or speedos

if you can go in a car's that's exciting at 50mph then why bother going out in ne that's boring at 150mph
Nigel Atkins

How can they be fixed upside down?

Dave
D MATTHEWS

what?

if you're rushing with the rain running down your bac to c.... then an idiot might fit one stub stack upside down closing off one carb air hole
Nigel Atkins

Oh, A's answer

well the filters are circular and the fixing is either side of the centre line so yes the filter (back) fixing plate could be put on upside down covering the vent hole leaving the back plate vent holes above the horizontal centre when they’re below the horizontal centre line on the carb(s)

or you put a stub stack on upside down
Nigel Atkins

I have a HIF44 with a K&N lookalike cone type filter, and at Peter Burgess' RR session in June he said the fuel/air mix and delivery was good right across the range. The filtr has no name on it, but looks exactly the same as a K&N and was half the price, so what are we to make from that? I just ordered a stub stack from a company on eBay because when I looked at the K&N ones, they were as rough a casting as I've ever seen, so again what does this tell us about K&N? Over rated and over priced? A question, not a statement.

Bernie.
b higginson

3 questions.

1) what's the part number for an HIF44 K&N Stubstack?
2) What do peeps think of the stubstack in the picture?
3) What can be used as a cheap substitute for K&N cleaner and oil?






Lawrence Slater

ref Q1

I bought my sub stack from:

http://www.ebay.co.uk/itm/CARB-AIR-FILTER-STUB-STACKS-TRIUMPH-MINI-MG-HIF6-HIF44-/350511323143?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item519c1a5807

HTH
Doug Plumb

Lawrence
The one in the pick looks nice.
Good radius going in the mouth and nicely smoothed out to the outside.
And since at this point in the inlet there is no fuel in the mix to condensate it can be as smooth as can be
Onno K

>>How can they be fixed upside down?

Dave - to clarify earlier answer to this:

The face of the carb has the obvious intake 'hole' - 1 & 1/4 inches on standrd carb. Then there's an additional smaller hole above the centre-line, which is the breather for the non-vac side of the piston. If the filter housing is put on upside down, the breather is blocked, and the piston moves very slowly.

The car appears very lethargic, won't rev easily, and so on.

Sounds like the bob/trebor problem.

A
Anthony Cutler

Doug, Onno,

The picture I posted is the same profile that Vizard promotes as being the most efficient. +5.8% better flow, over that of a bare carb.

Coincidently, it's also the same one as in the link you posted Doug. It's where I took the picture from.

I have a pair of exactly these stacks, in 1&1/4 inch size, that I removed from my old twin carbs, when I changed to the single HIF44. It's been so long since I bought them that I thought they were K&N, but now I'm not so sure.

Anyway, they are redundant to me now, as I won't go back to twins.

I should sell them really. Anybody interested?

I've been meaning to get one in HIF44 size. I've been lookig to find the KN part number for the same thing, and wondered if these were cheaper or better than the equivalent KN version. From what Bernie says the KN version isn't so good.

Which company did you use for the stubstack Bernie?
Lawrence Slater

There is an interesting thread on the MGA forum : cockpit braces / stub stacks- dated 20th Nov 2011.
A Anstead

Bernie,
the rough stub stacks are not made by K&N (as far as I know and there's no logo on them)

some have put that the surface wants to be rough to disturb the air

the K&n ones on Sprigets are pancake or deep with plate but a K&N cone type may be made to fit

your cones may be better than pancake K&Ns

only one way to find out . . . test
Nigel Atkins

Alan,

Thanks for that heads up on the MGA post.
http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=thread&access=&subject=6&source=T&thread=201111081635094231

Here is a pic posted by one of the contributors. I believe they are made by a chap called Steve Gyles.

They look similar, but perhaps nicer, maybe more efficient as appear to be lower profile, than those in the pic I posted below by the Ebay supplier.




Lawrence Slater

I have fitted them today all is fine I had to richen the carbs up abit. Very happy with them look better and sound better. Now thinking of getting these sub stack. Lawrence I could be interested in yours if you want to sell if they fit mine.
N Allen

Doug's is the same one as I am waiting to be delivered from the same eBay company. They are approx 13mm deep according to the eBay description and they look nicely machined. How are yours Doug?
Nigel. As Onno points out, the smoother the better at that point before the air mixes with the fuel in the venturi of the carb. The ones that I saw and thought were K&N were not like any of the ones in any of the pictures, but looked like extremely short ram pipes. They were being advertised by a K&N franchise to be used with K&N filters, so I assumed they were K&N, and they were very rough looking.

Bernie.
b higginson

HI, N Allen,
HS4 carbs are 1.5", whereas, my pair of spare stubstacks are for HS2 1.25" carbs.

So I don't think they will fit. Sorry.

Lawrence Slater

Bernie,

I have all the bits [modded HIF, maniflow inlet, K&N and sub stack] but have yet to fit it. Yesterday I managed to fit the Revotec fan I bought back in the summer at MG Live!

Have got a little bit nervous of fitting it after talk of incompatability of the forthcoming E10 petrol and a seal [or somesuch] in the HIF choke system. The plan was to trial fit the HIF to debug the fitting. Then refit the twin HS2 and check the power output on a rolling road immediately prior to fitting the HIF to do a direct comparison.

The sub stack is a Vizard type design and well finished. However, it does need to be relieved to clear the two rods.

HTH
Doug Plumb

Bermie,
I put a link earlier to the stub stacks I meant, nothing to say they're K&N and they're sold loose without packaging or logo so with that and the finish I'm prety sure thet're not K&N (and too cheap) - (see very bottom of page) http://www.mgocspares.co.uk/acatalog/MGOC_SPARES_K_N_773.html
Nigel Atkins

Doug. David Cameron has today more or less told the EU to get stuffed, so maybe we won't get the E10 stuff. LOL. In yer dreams! I'm worried about it too, but I don't think it will make much difference what carb you have if it's made of ally, or you've got copper fuel lines. We're doomed I tell ye, doomed! I'll be just putting mine on and seeing if it feels like it's giving me more power. (When it gets here).
BTW. How is your HIF "modded"?
Nigel. Yes. They're the ones, but when I saw them, they were side by side with a K&N filter, so I assumed they were K&N, but anyway I think the other ones pictured by Doug are probably better. Hope so, cos that's the one I've bought.

Bernie.
b higginson

According to Vizard, those short rams are likely to induce reduced flow, because although they have a rounded internal edge, the radius doesn't roll back around the outside of the ram pipe.

So anyway, as I asked, does anyone know of a substitute to the cleaner sold by KN?

It just seems to be a soapy solution to me.

Anybody?


Lawrence Slater

Try pulling the choke out a little (varying amounts by experimentation) and see if it is sharper at various throttle openings.

Peter
P Burgess

Bernie,

I bought the rebuilt HIF from AC Dodds, who is 'linked' to ML motorsport:

http://www.mlmotorsport.com/index.php?option=com_frontpage&Itemid=26

Some of their forum is quiet interesting.


The advert included the following mods:

Full spindle seals that prevent air leaks even when worn (unlike stock units)

Fast drop damper conversion

Ported Vacuum take-off

Throttle disc with no overrun spring


None of the common Vizard mods [reduced spindle or throttle disc screws] have been done but I will probably chamfer the front and rear edges of the piston damper.

HTH
Doug Plumb

Hi Guys

I have just been alerted to this thread by one of your guys interested in the stub stacks that I turned on my lathe. Have a look at the article about it on my website: http://www.mgaroadster.co.uk/ (just scroll down the page a bit to the 2 stub stack photos and click on the link).

One of our MGA chaps (Steve Ash) has found a local workshop that will turn them out at a modest price. If the MGA size stack fits your Midget, why not express your interest in a set on the MGA thread: 'cockpit braces/stub stacks'. Even better, if you have a lathe in your workshop, why not make your own!

You will see on my stub stack link that we had a set tested on a rolling road and witnessed a 4.8% increase in HP and a 2.8% increase in torque.

I also noted the bit in this thread about the K&N filter canister being fitted upside down and blocking the carb piston damper air balancing holes. It's a very common occurrence and causes the symptoms mentioned. My MGA supplier, Bob West up in Pontefract, says that he has no end of customers coming to him with poorly running cars, only for him to find the K&N (rear one on the MGA) fitted upside down. I did it once myself!

Cheers

Steve
Steve Gyles

Doug. My stub stack arrived today and looks very well engineered and it has already been relieved at the sides to avoid the filter screws. I'll fit it tomorrow and report back.
My HIF44 has got the plain throttle disc without the over run spring which impedes air flow, but apart from that I believe it to be standard. That link to ml motorsport looks great. I've not got into it in depth yet, but the number of carb topics is fantastic. I will certainly be taking a closer look at it. Thanks for putting it up.

Bernie.
b higginson

At a loss of what to ask my mother in law to get me for Christmas, I too have ordered one of these (on her behalf). She is going to be bemused when she sees what she's got me this year.
http://www.ebay.co.uk/itm/CARB-AIR-FILTER-STUB-STACKS-TRIUMPH-MINI-MG-HIF6-HIF44-/350511323143?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item519c1a5807
Gary & Gaps

Lawrence
The first stub stack picture looks identical to the one fitted to my HIF44. I bought it from MED Engineering. A bit pricey (not so much the stack but the postage!) but nicely made. I did have to releive the outer edge in two places to avoid the filter cover retainng rods. See:

http://www.med-engineering.co.uk/catalogue/search?q=stub+stack

Chris
Chris H (1970 Midget 1275)

Ouch, 90 quid, but at least it comes complete with filter.
Lawrence Slater

Lawrence
Only £25 plus P&P if buying the stub stack on its own.
Chris H (1970 Midget 1275)

Ah, I didn't read that bit, thanks.:)
Lawrence Slater

This thread was discussed between 07/12/2011 and 16/12/2011

MG Midget and Sprite Technical index

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