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MG MGF Technical - Standard Air Box Vs Carbon Fibre

Can someone explain the advantage of a Carbon Air Box over the standard one. I assume its a heat problem/ issue.

Therefore couldnt you line/ insulate the standard airbox with some form of insulation (tinfoil, exhaust wrap???) and hence save a lot of money.

I've currently got the standard filter in the standard box with a pipe going down and under the car to collect fresh air. The pipe is sealed at the airbox so its not drawing in hot air from the engine. I intend to order a K&N today so therefore what improvement could be gained from a carbon fibre setup that I couldnt get from mine other than less heat and therefore couldnt I insulate my set up and get the same results for a massive saving.


>>Can someone explain the advantage of a Carbon Air Box over the standard one. I assume its a heat problem/ issue.<<

No, it is not a heat issue Bob, although this is a reasonable assumption - and certainly an area where airboxes score over exposed cone airfilters on the MGF/TF.

The advantage of the aftermarket airboxes lies in their design, and where they take up air.

The standard airbox is a crude box, with air intakes positioned to reduce drive-by noise. As a result, the air intakes are sitting in a pool of warm air.

The aftermarket airboxes typically are cylindrical, and are designed with half an eye on the fluid dynamics of air flow. Moreover, they also have airintakes that project into the outside world - either below or sucking cold air in from the LHS air vent.

Keeping the airflow smooth, non turbulent and cool is an excellent way of improving engine power.

Whether they are worth the extra cost over re-positioning the air intakes of the standard airbox to the LHS air intake vent, well, that's a difficult call.

Rob Bell

Hmm. I think I'll fit the K&N to my modded air box and stick it on a rolling road to see how its affected things. I know carbon fibre is expensive but 250-300 is a lot of moola! Interested in the things I saw in MG world and particularly those who had used the Rover 820 airbox to house their filter.

Time for a trip to the scrapyards methinks!

>Carbon Air Box over the standard one

But carbon over a-another is just cos people like carbon fibre coz it's light, not sure how much you could tell the diffrence in weight of a few ouncs.
It would be more prudent to make sure you'd had a dump before going for a drive. Much cheaper way to save such a small amount of weight.

For people obsessed with shaving weight off, they could go the whole hog and have...

No, you use your imagination, mine has had enough for today.
Will Munns

Bob, mine was the car with the 820 airbox. Installation is pretty simple :o)

Lots of ways of installing one too - I've seen folks retaining the K&N intake tube, and figuring out an alternative bracket for the airbox itself. And Frabrice has used an ingenious way of getting even more cold air into the 'box (I must upload these pix soon!)
Rob Bell

depends how far you go Will.

now if you could find someone to make, carbon fibre body panels, door panels, bonnet, boot lid, dash, etc.

you could save yourself a considerable amount of weight.

paul weatherill

you could have change to a steptronic and get one of your arms amputated
Will Munns

...and a leg.
paul weatherill

That's handy, as all those carbon panels would cost an arm and a leg...
Rob Bell

rofl, hahahaha
paul weatherill

'A' for acheivement
Will Munns

>>And Fabrice has used an ingenious way of getting even more cold air into the box<<

Ok - I'm intrigued, tell us more!

Jim Hosking

Short skirt no knickers?

Ok I'll get me coat!
Will Munns

I've used 2 sources for air feed : from the side vent and from under the car with both (shortened) K&N hoses (+ T Randell bracket), supposing these would provide some ram-air effect at speed.
IIRC, I used 100mm tubing
It was really a pig to fit all the bits together ! esp through the side air vent. I also had to "remove" (well, rather shred !) the resonator box.
I should have somewhere a picture that explains better what I did.

I also retained the rubber hose from the 57i kit, but shortened by about 1/3rd. BTW, I wonder if this part is important or not, seeing some setups with 90 collars...

I haven't made a support bracket as the airbox seems to hold itself quite well in the engine compartment.

Last weekend when fitting a 52mm TTB, I had a look at the 820 airbox, and inside too, and everyting seems fine after 6 months of use...

I'll put Fabrice's pix on the site this week Jim :o)

Will - I can't believe you said that!!! ROFL
Rob Bell

Fabrice, Rob - thanks for the info - look forward to seeing the pix.

Like the idea of keeping the K&N tubing that connects the cone to the throttle body (and the fact that this negates the need for a bracket to support the airbix).

Not sure I'm as comfortable with the K&N hoses running from underneath the car into an enclosed airbox - but I guess you'd have to hit a pretty deep puddle at speed for water to be forced vertically up the pipes and into the airbox!!!

Just need to find a scrapyard with a Rover 820 now. Great instructions on your site BTW Rob. Think this has to be the best budget mod out there.


P.S. Will, shame on you ;o)
Jim Hosking

Jim, have uploaded Fabrice's pix - see

Fabrice, are there any other images you'd like for me to include?
Rob Bell

Clever design Fabrice! Thanks for posting the pix Rob.

Jim Hosking

Nice page, Rob ! good job ;o)
Esp. considering the dark pictures I've sent to you...

I don't have any other pictures, and with everything fitted, there's too little space in the engine bay to see something... well, apart from the 820 airbox at the top, the K&N hoses under the car and the 100mm grey hose behind the side grill.

Thanks Fabrice :o)

A picture taken through the boot grille would be good though, don't you think?

BTW have now hosted the RR result, comparing mine and Tom's car (R820 airbox versus ITG)...
Rob Bell

No problemo mate, I'll take a picture and will send it to you :o)

Interesting chart Rob - shows the 820 airbox is just as effective as the ITG in the mid-range (where, let's face it it's most useful for everyday use).

I'd be really interested to see the same chart comparing the 820 airbox with a standard K&N.

Jim Hosking

Hi Jim,

unfortunately I haven't got any 'same day' data for the open K&N (except for Tim's, but he had an ICON fitted)

Best bet is to look at Again, not directly comparable to the Emerald tests, because my (and Tom's) car had a performance exhaust fitted, whereas the data on this link, Richard Eaton's car still had it's original OEM exhaust.

However, what you do see is a huge hole in the torque curve @ approx 3000rpm (something we also saw on Tim's car [1.8 MPi] @ Emerald). This 'torque hole' is a very consistent finding on MPis equipped with the 57i kit - I've seen it on a number of occasions now. This 'hole' is completely erradicated when the filter is enclosed inside the airbox. This is the difference in performance you really DO feel with R820 modification.

I'll see what I can do with regards to a comparison curve and host it on the same site. I agree with you, this is where the advantage of the airbox mod truely lies :o)
Rob Bell

Even accounting for the difference made by the performance exhausts, a comparison of the two charts does show how much difference an exclosed system makes to torque (both smoothing out the hole @ 3000rpm, and increasing torque by approx 15 lb.ft across the rev range).

Thanks for satisfying my data geek curiosity Rob!

When I've managed to source a box I'm sure I'll be posting with some questions re: installation.

Jim Hosking

This thread was discussed between 01/07/2003 and 04/07/2003

MG MGF Technical index

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