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MG MGF Technical - Rover 820 airbox - it works a treat! :o)

Hi all,

many will recall that I've been meaning to fit a Rover 820 airbox to enclose my K&N airfilter. Well this afternoon, I have finally gotten around to completing the job!

I only intended to prototype the braket, but got carried away and finished everything (albeit with a temporary wood composite bracket holding the airbox).

On a brief drive across London this evening, I can't believe how much of a difference the thing makes. It's like the difference between the standard airfilter and fitting the 57i in the first place: I'd guess its worth in the region of 3 to 5 bhp.

You don't need much to complete the job - a cone airfilter (your existing K&N or Pipercross will do), an early Rover 820EFi airbox and some 70mm flexible induction hose from Demon Tweeks. Total investment should be less than 30 quid (sans filter).

Will post some preliminary pix and instructions shortly - bit for some pix of the aforementioned airbox, see

Cheers :o)
Rob Bell


I want one
Dieter K.

I shall look one out for you mate! ;o)

Have uploaded some low-res images of the installations to the above mentioned link on airboxes. Higher res images to follow, plus more detail :o)

Tomorrow will be at the Eelmoor sprint - so good opportunity to judge whether the above mod really does improve things as much as first impressions suggest :o)
Rob Bell

Even better then just the filter in the heat of the engine bay and much cheaper then any professional sold.
I wonder how it would fit to the GM TB. From what the pipework looks there is enough space.

Well done mate. Dark side for cash savers :)

Dieter <-- bidding 5 plus p+p for a 820EFI airfilter box
PS. did Andy know abou it ?
Dieter K.

Hi guys! My favourites Dieter and Rob!

I actually asked my mechanic to get one for me, and he tells me he has one in the garage. Was planning to design my own, as Rob hadn't finished his project. But guess what now he has!

i can follow his instructions..


Hope the airbox is same as the one Rob's got.

I haven't checked it yet. I just told him it's from Rover 820.

Hanah Kim

Hi Rob, just looked through the site! Looks wonderful. I also have a K&N and trying to do the exactly same job. (given that my mechanic has the right airbox)

Rob, I bid 10 pounds + P&P if I got the wrong one~ :-D

Anyway, could you please upload higher resolution pictures?

And why did you decide to use the side vents rather than scooping from underneath?

And also, do you have to replace the black rubber tube that came with 57i kit? (to throttle body?) Why did you replace it with the new duct?

And finally! Fast question. Demon tweak, is that like a car shop? or is it just like a hardware shop? I have never seen on before, so would be good to know what kind of shop I should look for this kind of tube!

Thanks Rob as always!

Hanah Kim

Demon Tweeks

Enjoy - but don't have your credit card to hand...

Ian Walker

Thanks Ian.

I know what it is now. :-)
Hanah Kim


Looks impressive. Hanah has already asked but how exactly did you connect it to the cone and TB? Also, is there a drain on the airbox? The reason I ask is that when I first directed the original air intake pipe to the side vent with the resonance box removed it did occasionally suck in water to the filter.

Hope the sprint goes (went) well.

Neil Stothert

Aaaarg...mods never stop! What is the ratio family/*F* for you folks *LOL*. This has become more than a hobby for me.
Nice mod and cheap. Well worth to look into.

cheers Rob,


Hi guys,

Neil, the sprint went very well. Great weather, good company, and better still, shaved a cool 0.5 seconds from my previous best time there. The airbox certainly contributed to that, I am sure. :o)

To Hanah's excellent questions:

>>why did you decide to use the side vents rather than scooping from underneath?<<

Either way would have been fine, but two factors swung this decision for me:
1. One of the problems of the 57i kit is that significant quantities of road debris and dust gets thrown at the filter with the scoops positioned where they are. It would be better for filter and engine if the dust load were less. Add this to the fact that the near side airvent appears to be a high pressure area on the bodywork (from video images captured using streamers at 40 mph) versus the underbody being a relative low pressure area, then the case is well made (the higher the pressure of the intake air, the greater the power).
2. The threat from flood water - an issue that Neil rightly touches upon. Raising the intake up reduces the chance of standing water being sucked up by the air filter.

Neil, I've left the existing openings in the casing patent for drainage. Whether this is sufficient remains to be seen - but interestingly, the ITG does without drainage holes as far as I can see (?)

>>do you have to replace the black rubber tube that came with 57i kit? (to throttle body?) Why did you replace it with the new duct?<<

This was done because I've effectively bolted the new airbox to the OE airfilter-enclosure mounting bracket. As you know, the engine moves quite alot on its mounts when the engine is under load, so there needs to be some flexibility and 'give' between the airbox and the TB. The supplied rubber tube with the K&N is too rigid, hence the need to purchase this flexible tubing (which contains a wire to maintain its shape as it bends).

>>And finally! Fast question. Demon tweak, is that like a car shop? or is it just like a hardware shop? I have never seen on before, so would be good to know what kind of shop I should look for this kind of tube!<<

Demon Tweeks link as Ian mentions - a specialist car supplier. Quite expensive actually, so if you can purchase something similar cheaper, do so and let us know! The tube has a helical wire moulded into the rubberised wall of the duct: this helps maintain the shape of the duct as it bends. Anything similar that is intended for automotive use and of similar dimentions will do the trick nicely.

Neil's question is very good: >>how exactly did you connect it to the cone and TB? <<

This is indeed the tricky bit. The 57i cotton filter is fitted to a metal colar adapter so that it slides onto the rigid rubber duct to the throttle body. This is what I've re-used here. The flexible duct slips over the collar and is kept in place using one of the jubilee clips found with the K&N filter.

The 57i filter is usually fixed to this collar using another jubilee clip to clamp the filter to the collar. This is no longer used; this part of the filter is now inaccessible inside the airbox. The collar is however a good interference fit with the filter, so infact this jubilee clip is not absolutely necessary. However, for extra security and piece of mind at the sprint today, I added an additional jubilee clip to stop the collar from inadvertently falling out. This did not happen, but I figured better safe than sorry. Will take an additional picture of what I mean tomorrow, and post it then.

Overall, it really is pretty straightforward, once the details were thought through.

David, you've got to go for it!!! ;o) I fitted this whilst wife was out with her sister shopping - so no family dispute there ROFLMAO!

Dieter, I see no reason why this shouldn't work perfectly well for a GM TB. Easy in fact :o) Andy knew that I'd been planning this for a while - but the fact that it is now fitted and working stunningly well will be news to him!!! :o)

Next time I'm in a scrappie, I'll look some of these 'boxes out for you :o)
Rob Bell

Higher res images now linked to low-res thumbnails on the above link (
Rob Bell

Oops - that bracket stops the link from working properly click:
Rob Bell

Thanks so much Rob!

I am going to the garage today to check if it's the right box.

Fingers crossed.

(Oh yeah it's already Monday here)
Hanah Kim

One thought.

Would it help, if I add another layer of tin foil inside of the box, to reflect the heat? Or should this layer go outside to reflect the heat?

Or is this just pointless.

Just an idea.

Hanah Kim

> (Oh yeah it's already Monday here)

So the world can't end on Sunday, then :-)

(remembering a snoopy cartoon of years ago on the same theme)


No... unlucky huh. But I am on a holiday for 2 weeks! Yay! :-)

Just got home from the garage after 8 hours. Done painting the new grills / done headlight painting as well. All went alright, except that headlight alignment thing is buggered, and adjusting the lights were a bastard thing to do! Damn..

And the airbox he had was a wrong one.. it's a newer model. So my mechanic rang up the wreck place. They want 30 pounds for it. Bit steep, but I want one, so I placed an order. Hope they can bring it soon.


So tired...
Hanah Kim

Another trip to the scrappy for me then.
I have to agree on the problem of the road debris on the cone which does concern me. Within a month of fitting the K&N the one side of the cone was covered with dust, sand and general debris. I have since moved the two cold air pipes further away from the cone to help reduce the problem. Hopefully if I carry out a similar airbox modification it will reduce the problem further.

Another question (the most important)-
How does it sound?

Only 0.5s off your previous best time - maybe your new seats weigh more than the originals:-)

Neil Stothert

30 quid??? Blimey Hanah!

An alternative solution would be to use the airbox from a Montego 2.0EFi. It's longer though, so this may require some thought on how to locate it - or even shorten it, but at least it means that there are alternatives to consider if the 820 airbox is not available.

The suitable airbox from the Rover is circa mid-eighties: later cars changed to a more squared off design - not so dissimilar to the airbox found OE on the MGF! So not ideal...

Neil - noise. Just as with the Maxogen conversion, induction noise is reduced markedly. With the new combination of MS exhaust + airbox, the car is QUIET! Arrghhh! I can hear rattles now! I think both Yimmy and I are going to miss the charismatic howl and growl of the TT exhaust... Is the loss of that lovely K&N induction growl worth it? For the performance gain, definitely. I reckon the fuel economy will improve too... :o) (Except that I'm enjoying the intoxicating improvement in acceleration at every opportunity at the moment ;o)

BTW 0.5 sec don't sound much - but 200 bhp 750 kg midgets were running only 2 seconds faster than me over the mile course... In context of a 60 something sec lap, 0.5 secs is pretty impressive. Obviously my driving has improved... ;o) ;o) ROFL

Rob Bell


Were you driving along the A40 (eastwards) about 7.10pm on Friday night around the Perivale/Greenford/Tesco Hoover area?

Saw a lovely BRG F with fantastic big white number roundals on the doors.

If that was you, I hate to think how loud it was before as it was bloody lound on Friday evening. It's what made me look. Sounded more like a Yamaha R1 with a straight thru can!!!!!
Billy Bob

>All went alright, except that headlight alignment thing is buggered,
>and adjusting the lights were a bastard thing to do! Damn..

Yep I had this, if the 'cogs' slip, a click click noise when turning the adjuster, then push hard on the back
of the adjuster whilst turning it. But I had Kingsleys car alongside to check that the alignment was right.

Just bring your car along to the next Luton meet ;-)

Will Munns

>>Yimmy and I are going to miss the charismatic howl and growl of the TT exhaust... Is the loss of that lovely K&N induction growl worth it?

Hi Rob. Yeah 30 quids, quite a bit actually. About that TT... :-) Will it depart your home soon. Muhahhaha I've done my grills. waiting my next project. I will have to bribe Yimmy though... not you Rob! Am I right?

Hanah (and no I don't want to change this thread into that story again)
Hanah Kim

LOL - yup that'd be me Billy. I'll pulled off at Hanger Lane for the N Circular :o)

The sound quality is really different with that exhaust. I'm getting to like it rather alot. I think that this is one of those systems that may be louder outside than in... but it IS quieter than the TT. Before, the whole house reverberated when I started the car - now I can make a quiet get away... ROFL

Hanah, yeah you are going to have to persuade Yimmy to lug that exhaust to the post office! ;oD
Rob Bell


Rob, great news! Next mod, then...
One question: the lenght of the flexible tube conecting to the TB is the same of the previous black rubber one?

More quiet, though... Ummm. Must look in scrapyards, for those boxes.

Cheers, Valter.

Hi Valter,

Happy hunting in those scrap yards!

Regarding the length of flexible tubing used, no, the TB tubing is about an inch shorter than the semi-rigid item supplied with the K&N (length now: 5" or 125mm).

The airbox inlet pipe (down pipe as I've labelled the pix) is 27" long (approx 675 mm).

Demon Thieves (sorry, Demon Tweeks ;o) sell the stuff by the meter - which will be plenty for the purpose here.
Rob Bell

If the 820 airbox is used, then why go to the expense of a K&N 57i kit, why not buy a K&N replacement element for a 820 - just a thought!
Jason H
Jason H

Definitely the recommended route if you do not already own a 57i kit. Then you'd need the airbox, four jubilee clips, 1m flexible hose and a K&N filter (and the choice of what is used is wide open).

The only difficulty then, Jason, is how to attach the flexible tube from the TB to the filter (the inlet to the aibox is a much larger diameter than the TB's). But this is hardly the world's most difficult problem!
Rob Bell

Hey Rob lurvley sound and the roundals are a real head turner!

Can you clarify was that with the TT or the Daytona exhaust and what induction were you running - standard 57i?

Cheers BB
Billy Bob

Had the MSD fitted (need to sort out the final alignment still) and the airboxed 57i mentioned above.

The roundels are a bit mad, and are likely to be removed at the end of the season. In the mean time, they're a bit of fun aren't they! LOL If any old 'New MINI' can wear 'em, why not a campaigned MGF? ;o)
Rob Bell

Quite right!

I bet it's the roundels that cut the 0.5 sec of your time and not the airbox! They certainly look the part. LOL!
Billy Bob

Update: I have put up the instructions for the installation of the 820 airbox on the site - accessed via the cold airbox link on the technical/DIY menu bar on (or use the link mentioned above, and click for the menu bar on the link at the base of the page).
Rob Bell

Hi Rob,

I have bought the 820 airbox. One problem is I went to different automobile shops + marine shops, and they don't have a duct sized 69mm or 70mm. Only thing they have is 64mm and a 75mm.

What should I do..?
Hanah Kim

Buy the larger tube and some electrical tape, wrap the tape around the thing you are attaching to tube to untill thay fit perfectly.

Will Munns

Hmm, a little too small and too big to be ideal respectively. Probably better to get the larger of the available ducts if nothing else becomes available.
Rob Bell

Will's suggestion sounds very reasonable.

It's really annoying being in a small country for something like this.. :(


How much did you pay for yours Rob?

(and what does Yimmy like? Tell her I will get some chocolate for her.. honestly..)
Hanah Kim

I can't remember exactly what I paid for it (I'll check my records) - but I think about 30 quid for the metre length (which I was a little irritated at the time about, but glad as I've used most of the tubing now!!! LOL)

What does Yimmy like? Oh, nothing cheap ;oD ROFL - Godiva chocolate is good ... but I'll let you negotiate that with her ;o))
Rob Bell


You sound so nice and thoughtful!!
Flattery and Godiva Choccies win everytime! ;0)

I am on my way to the post office to find a box and padding big and strong enough to take a >10kg exhaust to the other side of the world.


Yimmy Bell


Geez that's quite expensive. As expensive as the airbox itself! :-) The 75mm duct I was looking at was 10 pounds. What I might do is, modify the box so that I can use the original K&N tubing going into the box itself somehow. Or just use Will's method. I will design the VVC bracket and give you the sizes if I can.


Hopefully it wasn't Rob disguised as you, but is Rob helping you to carry that >10kg exhaust to the post shop? If I was there, I would help you along (but then I would just bring it home, if I were there.. wouldn't I? :)) I hope you don't get hurt by lifting heavy stuff around.

Uh, me being a student, can't afford very expensive chocolates at the moment (but hopefully when I become a doc like Rob I should be able to!). I will see if I can get something cute or nice for you tho! :-)

Thanks so much! Dream come true, it's going to be here during the holiday! Yeay!
Hanah Kim

Rob one more question. I am planning to visit another place to get some tubes. It's about an hour drive, but might be worth it.

On your instructions you suggested 69mm, but trying to fit it on 70mm was to cut the wire and stretching the top. Would you advise me to get 70mm then? or 69mm?

Hanah Kim

Cheers Hanah, any dimentions would be great. 75 mm might be enough to get it around the existing outlet flange (I don't have the measurements here). Might require some experimentation, but I'll look forward to hearing how you solve this problem. Hmm, might be good to have an 'alternative' solution on the web page?

BTW Yimmy's familiar with the woes of being a med student as well (she's a doctor too!)
Rob Bell

>>On your instructions you suggested 69mm, but trying to fit it on 70mm was to cut the wire and stretching the top. Would you advise me to get 70mm then? or 69mm?<<

70 mm would be the best, least hasstle option Hanah :o)
Rob Bell

Definately thinking about doing this one, thanks for precise intructions Rob, well done.

I've been informed the Airbox on the 416GT and 400 coupe are the same as the 820efi.

Can anyone confirm this?

paul weatherill

mis-quote: not necessarily the same, but similar shaped and will house a K&N cone filter.

paul weatherill

Not sure Paul. TBQH I thought that the R200/400 series used a rectangular airbox rather than the cylindrical one used in the R820EFi. An alternative source of cylindrical airboxes is the 2 litre Montego and Maestro. These look to be dimentionally larger than the Rover item, but could be used...

Rob Bell

It looks very similar to the airbox on my wife's GTV. Now where's the hacksaw - it's too quiet anyway (more refined apparently).

Neil Sothert

Thanks Rob. I have emailed both you and Yimmy.

Both doctors.. wow... :-D

Please check your mail box.

I am about to get dressed and go out to check out the ducts. :-)
Hanah Kim

I have tried 15 different shops and firms. Officially no they don't have 70mm duct in NZ.

Damn it!

Only size I can get is 75mm. And that's it.

Looks like I will have to cut the airbox so that I can fit the original tube from K&N to go into the airbox. Then can just use the 75mm ducts towards the vents. I don't like the idea of having a big gap in the throttle body itself. Hope this works. If not I will have to use 75mm with lots of tapes around the throttle body to make it fit 75mm. Or maybe by removing the steel ring and just tighten the jubulee clip might prevent other unwanted flow... hmmm... thoughts!


Hanah Kim

Use the 75mm stuff Hanah, and either pack them out, or remove the support wire and clamp them down to fit.
Rob Bell

Will do Rob. I emailed you.
Hanah Kim

Ok Mr scrappie here I come! Where is the best place to get a K&N from??
Mark Catterall

I have found another company that sell flexible alloy tubing - 70mm (1m about 6)

Check out

Click on Car Part and then on Air Filters/Induction Kits.

Can get ducting, collars and clips very reasonably.

Only problem is the charge for delivery - over 13!!!!!

Maybe they would use the Royal Mail if you asked nicely - lol.
Billy Bob

BB - not sure if flexible alloy tubing is man-enough for the job? I presume this is similar stuff used in domestic heating systems???

Mark - K&N 57i is available from a variety of sources, including B&G and Kinnor.

However, you don't need the whole kit - just the filter, a 70 mm OD collar adapter and 4 jubilee clips: you may find something suitable and cheap in your local Halfords.
Rob Bell

Your exhaust is on it's way!!
Yimmy Bell

Rob has done an excellent job turning an idea I had for some time into an excellent working system. It's also nice to know the original flow measurements and dimensional checks are apparently working very positively.

Now there are a number of Rover 820 air filter assemblies and similar assemblies used on other Austin Rover/Rover models, all of which are good scrapyard fodder. There is a list below, but note the years I mention as essentially between 1989 and 1992 this filter assembly style was largely dropped in favour of space efficient panel filters.

The ideal base filter to use is the one from the Rover 820 in e, Se, i, Si and SLi form from 1986 to 1991. In addition there is the Rover 820 Turbo which is a very limited run car that uses a different filter.

The reason I selected this specific filter is that the actual internal volume of the airbox has sufficient space for either an original paper air filter element of a performance type and the flow capacity would be way in excess of any naturally aspirated K series engine. This way it matters not how efficient the filter medium is in flow terms as the overall surface area means that there is always enough air for the engines demands. Big is beautiful in these terms.

Another reason for it's selection is that I knew from much work with Turbo 2 litre Rover engines producing between 225 and 250 real bhp, (and some that were producing more, but on a ragged edge of reliability!)with massive torque outputs, that this filter assembly could handle the airflow needs.

There is another benefit from the use of this 820 item in that the actual cold air pipe connection is significantly bigger than on the other similar applications, probably in the order of 10mm. (I no longer have any 'other' filter bodies to cross reference, just a single new and unused 820 e body - anyone want it?)

Whilst the 820 offers the biggest cold air pipe diameter the filter assemblies used on the following have the same base airboxes. Later (post 1982) Rover SD1 in 2000, 2300 2600 and 2400 Diesel form. 2 litre Maestro, petrol and diesels, turbo and non turbo, Montego 2 litre petrol to 1989 and turbo Diesels. Metro Turbo, Rover 216 to 1989 also.

There are also many differences with the method of anchoring the filter and for example the 820 with 'i' model designations (multi point injection) have threaded attachments as the filter housing is bolted to a mounting bracket that also carries the airflow meter.

The 'e' models use single point injection and the three fixings are simple interference slots in the moulding to take steel pegs of the mounting bracket. Only the 'i' models have the vent hole in the cap as it is for the idle bypass air supply on these models. These minor differences in the anchorages may help or hinder specific additional securing methods and I mention it because all 820 filter bodies are not the same in detail.

The K&N filter element listed for the MG Maestro, Montego models, EFi and Turbo, and the Metro Turbo is the correct element to use if you are following that route, K&N part number E2360. However you then have an issue on how to provide a secure air tight connection between the air box and throttle. The base of most of these airboxes has a very flexible connection that isn't normally carrying any load so you will need to use some rigid sleeving.

This could be perhaps plastic water pipe, gutter down pipe for example which I have seen used to good effect on Championship wining V8 cars, or some steel exhaust pipe which is available certainly well over 3" diameter in small incremenets from about 1". This is of course the same pattern that Rob has followed.

I have high hopes that if this system were compared to a variety of specific induction kits it would aquit itself very favourably on just performance terms. Clearly it already wins the economic battle.

Roger Parker

That info should help Dieter considerably Rog :o)

The airbox I obtained used the simple 'three spur' attachment, although it did also have the air pipe union in the 'cap' - so an 'e' or an 'i'??? I suspect an 'e' on the mounting description.

I completely agree with Rog - some RR testing would be most informative. :o))
Rob Bell


Interesting point Roger made. I hadn't considered doing this mod using the original paper filter rather than a K&N! Now that would be a really cheap closed induction system! I think I'll be paying the scrappies a visit on Saturday.


> BTW 0.5 sec don't sound much - but 200 bhp 750 kg Midgets
>were running only 2 seconds faster than me over the mile course

Russell Morgan

At last we have a good use for old 800 series Rovers.
Tony Escort Driver

Leigh, great idea, but area of difficulty will be connecting the 820 airbox to the MGF TB - different size bores. Not insurmountable though :o)

Hi Russ,

>>Hmmmm.... <<

Oops - that should read 4 secs... LOL

;o) ;o)

... and those 2-4 seconds might just as well have been minutes! ;o) ROFL
Rob Bell


I didn't look at the times. Makes me feel a bit better it was 4 seconds not 2 :-)

See you at Wiscombe if you are there.

Russell Morgan

Can't make Wiscombe sadly :o( CU at Dunkeswell?

Oddly, I've seem not to have managed to get to many hills this year :o( Been to loads of sprints though...
Rob Bell

I'll probably call in at Dunks to watch for a bit on my way to the B&B at Oddicombe. After that's it Combe then work begins on the winter mods..
Russell Morgan

First modification to the published instructions: use Nylock nuts to retain the filter in position. At North Wealds today, the airbox managed to vibrate away from the bracket... :oO

Otherwise, worked brilliantly :o)
Rob Bell

Rob, I might try to modify the box, to retain the original K&N tubing to make it a tight fit over the box, and so that it doesn't need any brackets in place. Well, let's see how that works out as I can't get any decent ducts here.

Hanah Kim


I'd be worried about the extra stresses on the TB because of the weight of the air box if you don't use a bracket.

Neil Stothert

Neil, is the box that heavy? Personally haven't seen one yet, or don't even know if I can get it yet.

Also my TB is an Trophy version, not a plastic crap! :-)

Even If I end up using a bracket, I will have to fit with a K&N tube. And that's my goal!
Hanah Kim

I agree with Neil - I'd be a tad concerned about the weight that you are trying to suspend from the TB - remember it is not just the weight, but the leverage of that weight (bending moment) on the TB by being suspended 6 or so inches away from it...

This is the reason I made up the bracket, and searched so hard for some 70mm flexible tubing (found 69mm stuff at Demon Tweeks, which is close enough).

Hanah, what I'd suggest is that you cut the original K&N rubber tube down to about 4 - 4 1/2 inches, and then use your slightly larger, 74mm flexible tube to 'interface' that tube to the airbox outlet flange. It should work nicely :o)
Rob Bell

Unfortunately I have to put up with the plastic crap, as you put it Hanah:-)

However my K&N has developed a whistling noise above 6000rpm. I don't mind the noise I just can't remember it previously. I've tried explaining to Jennie that the noise is a result of the restricted flow through the smaller ID plastic TB and that the larger alloy TB would solve the problem and help the longevity of the engine. - She doesn't seem convinced.

Neil Stothert


Thanks, yeah that's what I was thinking as well. To shorten it. One because of the lever effect, and two because it bends down a little. :-D
I just haven't described it properly did I? But thanks for all the great ideas.


Sorry! I didn't mean to offend you or anything... I just can't believe how Rover put that sort of throttle body on a 16k car! That's just ridiculous. My friend's Toyota Levin came with 4 throttle body thingy stock standard...
Hope you can get the alloy one soon! :-) It will be beneficial...

I think Rob has a black thing as well.. doesn't he? ;-)
Hanah Kim

Yup, still got the black plastic nasty. But have nice new alloy replacement just sitting there, ready to go on :o)
Rob Bell

Neil, I would check the connection on the throttle body as this could be caused by an air leak round the join. This is possible if the K&N has been tightened up too much on the throttle body. The p[lastic can be bent out of shape causing a leak and so causing a noise.
Tony Escort Driver

Thanks Tony

I'm about to leave for the office so I'll have a look first.

Another reason though to convince Jennie that I need to spend some money on an alloy TB.

Neil Stothert


Finally (after how many years) am getting around to get a filter. Jenny had a trip in David's car in Germany and said that the filter noise was very loud. I'm therefore interested in making the mod you suggest. Any ideas on where I could source all of the bits that I'd need in the UK ... I'm out here in CH so a trip down the local breakers isn't going to be easy. I'm going to have to do mail order and then fit them one weekend when I'm home, so I want to make sure I get exactly the right bits before I start.


Stefan Gibney

Hi Stefan,

I'm kinda surprised that Jenny thought that David's car was a little noisey - I think it's a pretty standard car, except for the filter (a K&N I presume David?) Usually there's only noise when you are accelerating.

Anyway, the 820 airbox does a good job of dampening the induction noise - so no problem there.

The base for the filter set up I used is a 57i kit for the MGF. I suspect, although I have not confirmed, that the cheaper 57i equivalent for the Metro GTi will also work ;o)

The Rover 820 air box I used was the one from the 820i (the one with the air bypass into the cap that I've used to fix the airbox into position). This should be available from any autobreaker for about five quid. The flexible ducting (Samflex High temp silicone ducting, 69mm diameter - SAMSFD-069 - sold in 1 metre lengths) was purchased from Demon Tweeks. Has anyone else found cheaper alternatives?

The 8mm bolts and nylocs were purchased from Halfords.

The bracket was made from material I had lying around anyway - but sheet ali can be purchased from RS or even a DIY store like B&Q.

That lot should keep you going. :o)

Any queries, just let me know :o)
Rob Bell


Thanks for the shopping and supply list. You're right about noisy when accellerating and yes, David's car is standard apart from the K&N!! SF was saying that is filter is a lot quieter, hence the idea of using the 820i box.

Only issue I might find is sourcing the 820i filter box from over here. Right, here we come.

Stefan Gibney

Good luck! :o)
Rob Bell

just caught up with this thread...yes it's standard apart from the driver's lead foot and the 57i (which was on it when we bought it incidentally). I suspect Jenny found my car a bit noisy because we went out with the roof up as I was just closing it up for the night. I note Rog mentioning the use of Montego airboxes - back in the spring I fitted a K&N to my Monty turbo and re-used the airbox in pretty much the same way as Rob has on the F, only I cut an extra hole and have TWO inlet cold air tubes, one from the normal position and the other from under the front valance. It works well. I think I'm about to buy a 52mm TB for the F so will look at fitting a Monty airbox at the same time as I have several kicking around :-)

David, if you do that, can I have some pix of your installation process? Would be good to put a couple of alternative solutions together. :o)

Rob Bell

Yes will do, if I managed to be 1st in the queue for Jonners' TB.....

My only question with these closed filter systems, what happens if you go through water with the air intake. With an open filter the water just falls on the floor, with the standard filter the water just drops into the resonance chamber. With a closed filter it gets sucked up into the engine. I know we have some cooling problems but I think this would be going a little far...:-)
Tony Escort Driver

correct Tony,that's why the latest thinking by Rob et al is to site the air intake next to the left hand side vent, NOT under the car as previously. by the by, many standard production cars suffer the same problem - witness the number of claims from disgruntled customers of certain Renault models a few years ago when they experienced wrecked engines after driving through what seemed to them to be shallow floods, because the air intake pipe was very low behind the bumper..

I'll keep my fingers crossed for you then David - that TB sounds a bargin! :o)

Tony - the worry of water take up by the enclosed system was one of the reasons for mounting the intake where I did- behind the nearside vent grille. It is about the same height as the standard intake - and remember that the standard air intake system is also enclosed.

I think that the probability of water ingestion is low. Firstly because I am not likely to go off-roading through fords terribly often ;o) and secondly the K&N filter is well recognised for its water resistance (and use on water scooters). However, I have left the mounting holes in the 'box patent, which will aid drainage (albeit at a rather slow rate).

I don't think it'll be a problem - so long as you don't try to use your MGF as a speed boat ;o)
Rob Bell

You beat me to the post there David! LOL
Rob Bell

Another reason for adding a mounting for the filter box is vibration. This will sooner rather than later klead to a number of problems with diconnecting pipes and other extraneous noises being generated.

Water ingress would have been a problem for the original 800 set up in the wet as well, but it wasn't. The point of cold air pick up was mounted away from any risk of doing an imitation of airborne fire engine skimming a lake.

Any small amounts of water that are drawn in will drop out of the airflow inside the airbox as it will not be fast enough to carry any weight of water. Minor droplets that are carried will be dealt with by the airfilter medium and any that pass through will have a positive effect on providing a coolign effect to the intake charge as it evaporates the closer it gets to the combustion chamber.

BTW Tony the old 800 range had a number of uses. One was that it donated it's rear calipers to the F and another is that the late 825 gave us a lovely V6 which does so much for ZS and ZT models today!!

Roger Parker

After purchasing an 820 airbox (cheers Rog) I decided to drive over to Demon Thieves today to purchase some of the precious 69mm pipe that Rob had purchased. Unfortunately today was the day someone decided to transport on road half a nuclear power station through Shropshire and North Wales. After waiting in the queue at Demon Thieves for twenty minutes for delinquents to persuade their pregnant girlfriends that eyebrows would look 'kewl' on their cars I was told that you cannot buy such pipe with a 69mm ID. Although I explained that I know someone has previously purchased such a pipe I was told that even a turbo car wouldn't require a pipe of such a diameter. At this point I put my other potential purchases on the counter and walked out.

Anyway this afternoon I managed to fit the 820 airbox using the original K&N rubber pipe. Although you can't use the original clip at the base of the cone to hold the steel collar in place I used a long cable tie which did fit through the airbox. Using the K&N rubber pipe worked quite well and although the box is at an angle it appears to rest on the original box mounting and the fuel filter mounting. For the time being I have used cable ties to ensure it doesn't move. I did manage to find some 70mm foil piping at Halfords in Wrexham that I have currently used from the airbox to the side vent although I can't see this lasting very long.


Getting to the point, is your resonator box still in place? I ask because getting a 70mm pipe to the side vent was difficult without losing some of the cross-sectional area.

Difficult to know on a quick blast if there is much improvement in performance but the car is very quiet:-( However, hopefully the cone wont become so covered in road grime. When I removed the original cold air ducts a load of road stone and general grim fell out of them. I'll give it a good try out on the way to Leicester tomorrow for the F day.

Neil Stothert

Neil congratulations. I haven't got the part yet as it is very hard to find one here. :( I thought I had one, but someone has taken the airbox already. SUCKS!

That was exactly what I was going to do, and you seem to have done it with success already! Now I can just follow your steps! :-)

Did you see a noticeable benefit after the installation?

Hanah Kim


Difficult to say. I'm going on a longer run today so I'll post later. If pressured I would say it was better in the mid-range, although because of the reduced noise it felt it was less hassle for the car to reach higher speeds but I think that was totally psychological.

Allowing the K&N pipe to pass through the box was fine because, as explained by Rob, you have to pack the lid to keep the cone in place. The bottom of the cone is rubber and sits on a raised ring in the base of the box producing a good seal. A jumble of words but you'll understand when you see it. If I decide to keep the setup I'll probably remove 10-20mm of the length of the rubber pipe to give the box a little bit more space.

Neil Stothert

Great Neil,

Any photos in the future that I can expect? [maybe post it to Rob if you don't have your own website?]

Hope your ride proves that it's worth the effort that you put into! :-)

Have a safe one.

Hanah Kim

Just caught up with this one - very interesting, very interesting indeed! :-)

I remember Rob and i discussing this mod and comparing like-for-like measurements with the ITG Maxogen around the spring bank holiday weekend earlier this year and the similarities are incredible. In fact, the only thing the ITG has going for it is the conical intake and given the relative prices of the 2 modifications (even if you have to buy a new filter) i can't see why anyone would go down the ITG route now.

So, i am not in the least bit surprised that it works and works well, it ought to, ITG have done all the R+D on it! ;-)

Interesting point about routing the intake pipe to the side vent. ITG state in thier Maxogen instructions that the pipe should be routed to the underside of the car and unlike the K+N 57i, should not be pointed towards the front, rather it just sits perpendicular to the road surface - assume because any ram air effect would counteract the air flow characteristics of the conical intake. This i presume gives more power lower down the rev range, but a ram-air type system would gain benefits as the car's speed increases.

Given that Scarlet is lowered and also the rural locale of where i live and drive regularly, i am seriously considering routing my ITG intake pipe to the side vent as when the weather breaks i feel that i am running a bit of a risk drawing air from underneathe the car.

Well done Rob.


P.S. Stefan, i replaced my flexi-pipe and Scarlet is now sounding like her old self again.
Scarlet Fever


I'm amazed to hear that the fitting instructions from ITG say to fit the pipe inder the car. Every Maxogen I've seen fitted has had the pipe routed to the side intake. This is certainly how TechSpeed fitted mine.


Yep, this is how mine is fitted (not by me) and has been a potential source of concern ever since. I assumed (incorrectly as it turns out) that due to the location of the petrol tank it was not possible to install the induction hose with the intake in the side air vent, but after seeing Rob's pictures and knowing how similar the two air boxes are i will probably re-route it next weekend.

Any idea how the end of the intake pipe was secured inthe side air vent?

Scarlet Fever


The main problem with positioning the hose near the vent is the restricted access by the resonator box. Otherwise if you remove the vent grill and the two internal housings you can fit your arm inside and pull the hose through.

Neil Stothert

Neil, no idea why you couldn't get the 69 mm silicone induction tubing (Samflex High temp silicone ducting, 69mm diameter - SAMSFD-069 - sold in 1 metre lengths). Presumably lack of knowledge, as I've seen similar LARGER diameter stuff used as brake ducting on an evo VII... I ordered mine by mail order - maybe try again by phone Neil?

The duct in the nearside vent is just resting inside the duct. There is just enough interference to stop it falling out, so no further fixing is required. Access need not necessarily be by removing the grille, as you can get to the area under the resonance box via the wheel arch area.

Improvements are there - but you need to be on a familiar road to notice it. Plus the improvement in low-end torque was noticible on my car :o)

Keep us posted :o)
Rob Bell


I have my 820 box. Some one is making me a alloy sheet. Do i just need the 69 mm tubing (31 quid with delivery very expensive) and that is it.

Also from your pictures it looks like you have used the 69mm tubing for both the throttle body side as well as the intake side. Is this correct
Steve Kemp

I've done 200 miles since fitting the airbox on Saturday afternoon and there is a significant improvement in low-end torque.

As for Demented Theives, well they make MS look positively good value (sorry Mike) but I've been put in touch with another supplier.

Neil Stothert

>>Also from your pictures it looks like you have used the 69mm tubing for both the throttle body side as well as the intake side. Is this correct<<

Yes, I have. That wasn't the initial intention, but actually was the easiest solution Steve.

>>As for Demented Theives, well they make MS look positively good value (sorry Mike) but I've been put in touch with another supplier.<<

Keep us all posted Neil - I have to say I wasn't too happy spending over 30 quid for the silicone tubing I used... :o(
Rob Bell

This thread was discussed between 31/08/2002 and 23/09/2002

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