Ok lads ive been looking at threads on here, came to conclusion from info , bigger the filter the better , so ordered the filter rc-8260 . points in question the car is mafless on simtec using vf34 and all the other bits mapped by BR Swindon. reason im changing is the filter I have k-n but 175 mm in height has a 8 mm hole in its side wall. so while im spending on a replacement I thought bigger would provide better breathing. have i made correct choice?


To fit shouldn't be a problem with maff tube removed and sfs reducer joiner 76mm going to 100 mm for filter flange. 90 deg bend looks way to steep ?so 45 deg i think would be better, with cutting a bit off i suspect.


Thanks to anybody with response.

 

Mine is the 100mm and I got the reducer 45 degree off eBay for about £20

 

hi gaz thanks for the pic, this is the very set up im looking at , my car is a gc8 99uk the perrin heat shroud looks real nice.

 

I also have MY99 (STi 5), MAFless with Simtek.

I did the same: replaced the small cone (of unknown brand) with this one:

http://www.knfilters.co.uk/mobile/mP...x?prod=RC-5106



It was the largest I could get into my particular bay's available space.

 

lol well your is bigger than mine ! what a squeeze that must of been . did u notice anything different on torque bands? was it pulling better in low speeds or higher rpms? or just better all round? after all that's why im doing this.

 

Not really. No difference.

As it was obviously mapped pulling through a certain CFM of air on the small cone. Being MAP-based/boost reference, doesn't alter that - unlike for a MAF setup. (I think). So it shouldn't lean out the AFRs. I certainly haven't noticed the Simtek knock light come on at all - it all seems to behave the same as before I changed the filter.

I replaced it because the small one looked, well...cack lol

Plus it was a 'future proof' thing: just in case I, say, fit a bigger turbo and get another remap later on. (I didn't want the small filter to be the weakest link restriction).

 

Re. fitting...

I spent time researching the appropriate sizes using the K&N website's helpful ready-reckoner. I'm confident I've chosen the biggest (in terms of dimensions/surface area/CFM), for the physical space available.

It was indeed a tight fit... But just manageable. Nothing too arduous, in the end.

 

ready reckoner ... welli must have a look at that. great

 

lol

https://en.m.wiktionary.org/wiki/ready_reckoner

 

Here it is:

http://www.knfilters.co.uk/mobile/mU....aspx?id=S0013

The 3 you need to use are:

(F) Flange inside diameter (to be approx the same as the outer diameter of your intake pipe's filter mounting end...within +/- 2mm)

(L) Height (as long as poss. for your bay's space)

Base diameter (as wide as poss. for your bay's space)

 

excellent help there , could of done with his last Monday ! been searching on net for correct pipe sizes ect. my inlet pipe is the 76mm version the k n filter i believe is 87 mm roughly at fitting point inside flange to pipe. i asked k & n chat what the wall thickness of flange area is ? Richard informed me approx. 6 mm . so 6 mm a side approx. 100 mm the sfs pipe do a 76-102 which i may go for. thanks again chaps for advice.

 

Hold on.

The filter will clamp to the OUTSIDE of the hard intake pipe, so the filter's flange wall thickness will have no effect on the filter's I.D. (because the walls are on the outside, IYSWIM).

So if the filter flange's I.D. is 87mm, then so must the hard pipe's O.D.

So the hard pipe O.D. needs to be c.85-89mm (c.3.4") at the filter end.


Or have I misunderstood?

 

This is the one I got that fitted just right. https://www.ebay.co.uk/itm/252239976518

 

the hard pipe ( reducer elbow 45 deg ) which im to buy will be to fit onto the filters flange, filter flange sitting inside hard pipe, the filter im getting in the specs page shows internal flange ID 187 mm ( wall thickeness of flange not inc ) im surprised k & n don't give the OD dimension of the flange for correct ID of hard pipe to be fitted. however as at present , i have a rubber pipe that comes of the turbo inlet pipe, this then goes on maff tube ( TO BE REMOVED ) excuse my caps lock , but im unsure ?? is it poss the rubber pipe is infact 100 mm anyway at open end.... the filter ...http://www.knfilters.co.uk/search/pr...x?prod=RC-8260

 

Ah, sorry. So your hard pipe will be a silicone one then, rather than ally.

Makes sense now.

 

cfm s , the filter i have i think mab limited to what cfm s the vf34 can deliver hence why at thwaites mark couldn't get me over 320 mark , i have a feeling the filter i have on is limiting at 6000 rpms , not getting enough air. but again k &n don't seem to have a page for cfm flow charts for specific filter applications, the one i have was great for the tdo4 etc. but things are different now. or that's my theory at least.

 

The reason they don't give wall thickness is, presumably, because they assume it will be mounted onto a hard pipe (which would go inside the filter).

As per my scenario in post #12, above.

 

yes , will a silicone pipe be ok to use as fitting filter to this? silicone isn't hard so will i get a good enough seal between the two? or will i need a ally spacer in situ between said filter and silicone pipe? the idea of the pipe going inside the filter flange itself does sound better fit. as i can choose the od perfect for 87 mm. pipe inside , jubilee clip together. mmmmm ???? going to have a quick look again now make sure filter is inside the pipe as it stands.

 

IIRC, the MY99 MAF tube's O.D. is 90mm?

 

If going for a silicone 'hard' pipe intake, then I would defo use an ally internal joiner (87mm O.D.), with 2 jubilees, yes.

 

ok the pipe as it is goes over the filters flange, also there is a soft pipe at 87 mm before the maf tube so looks like i wait for filter to arrive , then test fit to said 87 mm ID pipe. i cant see any need to buy another pipe now, yipeeee!

 

Yeah, just wait until the filter arrives.

Then, just re-measure what you need to.

That way, as you say, you might find you don't need anything else.

 

yes no point in spending any money till im certain of what is needed. was quite shocked to see that i could prob fit even bigger filter in there ! nearly 250 mm . but the one i opted for is absolutely fine. thanks again for your pointers

 

There is a formula you can use to work out filter size and/or CFM. That way, if you know your turbo's own CFM, you can determine the smallest filter required.

If your filter happens to be at least that CFM figure, then you're laughing.

(And that's for the turbo's max flow rate/bhp potential, anyway!)

 

have a feeling the new filter will be more than big enough. but i will see if i can find out more info, i think the vf34 is approx. 440 cfm s. at most , but as with all things depends on its surrounding counterparts to work to full capacity .

 

I'm sure it'll be more than adequate.

My original small cone (4.5" long & 4.5" dia. base), flowed enough to make 384bhp on a 20g. Which is bang on the money for that turbo (360-400).

In contrast, that replacement larger cone I bought, has x2.25 (or 125% more) area of the small cone!

 

looks like i may of overcooked this size according to your info there, the filter that's in is 165 mm long x 120 mm dia , but anyway its got a hole in the side , that's my excuse lol. they look great in red with the new oil on ! will look a little better to.

 

When you say overcooked, do you mean "too big".

Fear not, as you can never have 'too big'. As the airflow will always be there.

That's why people fit as big a cone as poss. (as you have nothing to lose and everything to gain).

 

Yeah, I love the cleaning process of air filters.

It's so satisfying spraying that pump-action bottle for the suspension fluid, and seeing the filter's colour change and all that jazz lol

 

lol yes the stimulation level is amazing lol!! u bad dirty filter im gona make u new and shiny again. yeh I guess I have loads of head room with the bigger filter in the event I fancy a bigger set up. have thought about engine refresh to 2.1 rcm kit, then poss get 2 ppg cogs fitted then a gt30 turbo . don't know , finances im sure will let me know in the future.