E30 Zone

I've had my 325i E30 over a year now and it's fitted with a K&N 57i induction kit. I fitted it instead of a new air filter thinking I would get more power and to be honest, I haven't noticed the difference because it was fitted along with other mods...

(FYI, I also fitted H&R suspension kit, H&R ARB's, New Radiator, hoses, belts, thermostat, coolant temp sensor, timing belt and tensioners, Dizzy cap and rotor arm, plugs, filters, fluids, fuel tank, centre prop mount, air boot, fuel hoses, stereo, Evolve Performance chip, Subframe bushes, M3 Control Arm Bushes, and fitted recon 15" BBS alloys with Pirelli's...)

Anyway, I was just wondering why a lot of people on here claim a power loss from these induction kit's? Is there any proof or is it just one of those duty rumours that goes around that everyone quotes because they heard it from someone else?

I mean, why the hell would K&N develop a go faster product that makes your car slower?

Thanks

Why would BMW spend so much money on developing their airbox if it didn't work properly? I have a K&N drop in panel in my car purely because I had it lying about and the one I had in the car when I got it was filthy. So to be honest I don't know how much of a difference it makes.

Never had a cone filter though, didn't seem viable when the setup I have works fine.

The standard airbox has a ram cone.
To answer the last question there, it's to do with making money.

I had a k&n cone on mine and they are crap , I rran a green stuff cone filter and it ran a lot better
Think the k&n cones are to small tbh as i have hd this problem with other cars not only the bmw
Id never have another k&n unless i had to have a panel filter , If its a cone go for a green stuff one and make sure its getting lots of cool air

If the engine is not in a high state of tune, then it will lose torque with any induction kit. Yes you will have a slightly higher top end speed but that's it. Getting there will be slower.

Why would BMW spend so much money on developing their airbox if it didn't work properly?

BMW developed that airbox in the 80's, technology has moved on a lot since then.

I know everyone says they're crap but what I want to know is why?

What about some evidence?

Dunno about the power output gains, but this makes interesting reading:

http://www.duramax-diesel.com/spicer/index.htm

yeah but back then the airbox developed was designed for that engine! each k&n is developed the same with a bigger or small hole at one end, to caitor for each modle of car.

bazeebond wrote:

Why would BMW spend so much money on developing their airbox if it didn't work properly?

BMW developed that airbox in the 80's, technology has moved on a lot since then.

I know everyone says their crap but what I want to know is why?

What about some evidence?

The understanding of fluid dynamics hasn't changed though, and the technology used to create these boxes is exactly the same now as it was then. The BMW air box takes in air from the front of the car, and prevents hot air being sucked in from elsewhere under the bonnet. The induction tract isn't long and complicated so there isn't much if any unnecessary turbulence caused that can be rectified by fitting a cone filter. If however a cone filter is shielded properly and has plenty of cold air fed to it, then you probably could match or beat (if not by a lot) the original airbox design, but what's the point?

bazeebond wrote:What about some evidence?

OK then, here's some evidence.
When I bought my Touring, it had a 57i fitted. It idled rough, had a horrendous flatspot (somewhere around 2k rpm IIRC) and wouldn't rev beyond 5.5k. The previous owner thoughtfully left the original airbox in the boot. I took the K&N off, refitted the original stuff and hey presto - idled as sweet as a BMW 6 should, no more flatspot and revved right to the limiter. Fuel consumption was better too.

bazeebond wrote:BMW developed that airbox in the 80's, technology has moved on a lot since then.

But the engine the airbox is matched to hasn't developed either, has it?

OK, thanks for some really good answers there especially Stubeedoo.

You know it's hard to come to terms with the fact that you've wasted 60 odd quid on something that actually makes your car run worse but I'm afraid, it sounds like I wasted my cash! Luckily I kept the old airbox so when I next get the chance, off with the new and on with the old!

The wasted cash for a K&N cone filter seems nothing compared to what I've put in the car that will never come out again. I've spent £2500 to date and had to stop and draw the line before I threw even more at the brakes, the rear arches and an LSD because she's probably only worth about £1000 at the moment. That line was drawn when the coolant level sank and the oil on the dipstick went milky...

Infact, I've been close to cutting my losses and selling her but have today decided that I will keep her. It's going to mean a recon head which may turn into a full engine rebuild. But why rebuild the whole engine and not get a turbo conversion at the same time....

i have a k+n panel filter on my car... it will help when it comes to chipping the car... at the moment i doubt it makes any difference.

Have you considered an M50 swap? Will probably cost you less than an engine rebuild and will definitely be cheaper than a turbo conversion.

bazeebond wrote:I've spent £2500 to date and had to stop and draw the line before I threw even more at the brakes, the rear arches and an LSD because she's probably only worth about £1000 at the moment.

Most of us have "been there, done that". In the last 4 years I've thrown in excess of £3k at mine (probably over £4k actually, but I've stopped counting). Next year, the bodywork will need sorting - irrespective of cost - and realistically the car isn't worth a grand.

Ive got a KN cone on my car and it DOES make a difference.
Shielding it from hot air is a must though.
Incidently mine is only fitted untill I get round to modifying an airbox.

bazeebond wrote: I mean, why the hell would K&N develop a go faster product that makes your car slower?

Because they want your money?

Cotty wrote:

bazeebond wrote: I mean, why the hell would K&N develop a go faster product that makes your car slower?

Because they want your money?

I want your money paypal me it and keep your OE airbox!

Have you considered an M50 swap? Will probably cost you less than an engine rebuild and will definitely be cheaper than a turbo conversion.

Yeah, a mate of mine is always saying I should do an engine swap and the M50 would be the obvious choice even though the power is only about 20 BHP more. Although, I'm not sure how much messing around I would need to get the M50 in with the wiring etc... I'll have a read through the forums. Trouble with engine swaps is that you start off thinking about an M50 then someone changes the M for and S! And you have to find an engine that's not a pile of crap... At least with a rebuild I'd know it was good...

For the real world, in my opinion the ideal engine swap would be the 330d engine. 204BHP, 302 Ib-ft of torque, and 45+ MPG! I don't think anyone's ever done one though which means to me that it must be either impossible or a real pain in the arse! Anyone heard of such a conversion?

I assumend it was because the injection system used in the older BMW's was too primative to take advantage of the increased airflow (ie chucking more fuel in) so it would just run lean.

If you get the figures for K&N airflow they are rediculously high compared to a paper filter. And a very small K&N will often flow enough air for a much bigger engine than you would expect.

So the best thing to do is probably concentrate on keeping the air cool, the colder air is the more dense it is = More oxygen per cubic unit = more oxygen in your cylinder. (iirc lol) Maybe this will still leave it running lean as the injection system isnt upto making the apropriate changes?

I quite like induction kits but hate K&N

Theirs is a cheap universal fit piece of crap. The mountings are all plastic which get brittle with the engine temps. When they break, K&N are not interested unless you can produce a receipt. W@nkers

I had a Pipercross kit on my cabby. Loved it. Machined aluminium, proper fit.

I read an extensive research into various types of induction. One of the conclusions was that the engine bay achieves ambient outside temperature very shortly after pulling away.

BMW and other manufacturers design their airboxes taking into consideration many factors such as:

- Pass by noise
- Pass by noise
- and some more pass by noise
- Cabin noise
- some more Cabin noise
- Consistent intake temperatures
- and some more pass by noise....

The systems are not as efficient as you might believe.

On Z3M's, E36 M3's and some non M Power cars there are significant gains from intake systems. The down side? Much more intake noise resulting in more pass by noise and in cabin noise.

There are LOADS of independantly tested dyno tests accross many forums for lots of different cars. They do work and easily beat the BMW setup if designed properly.

The problem with the K&N system is that it increases inlet air temperatures drastically. It has no venturi lip. These two factors combined lose smoothness and power.

Open filters which are placed just behind the headlight don't really create high intake temperatures. The K&N one sits far too back in the engine bay.

Either way then, my K&N induction choice was a bad one!

So today's lessons are either:

If it ain't broke, don't fix it.

or

You get what you pay for.

I had a K n N that was given to me, i fitted it and it kept popping of the plastic bracket that was with it, bad design and small, next day i took it of and fitted a new ITG filter, never looked back!!!

And regards to spending money on cars ... ive spent probably £3000, pistons, camshaft, chips, M5 diff conversion, dogleg gearbox, throttlebodies e.t.c.... list goes on and i know if i was to sell it i would get probably £1000 for it, no one appreciates the time and power of the work youve donr to your car!!, id rather takes the engine out and store it in the garage on a pallet if the chassis ever rots good and proper OR if i cant sell it with the money i want....


j

I think the after market filts can actually spoil the engine note quit badly. I think only thing you will get is a louder noise and possibly be more thirsy as an result of it.

The ITG kits we used to offer made hardly any extra noise and we consistently got 4-5bhp on before and after dyno sessions.

Some things do work.

The only Cone filter I have experience of actually working. By 'working' I mean liberating horses by increasing the air flow into the engine and also by increasing throttle responce. It was on a friends 306GTi(sorry for swearing at you all)
He had it live-mapped when the filter was added and he saw 16bhp and something like 15Nm increase in torque .... but he had to have the map to achieve it, otherwise the tuners reckoned he'd have seen 2-4bhp MAX. The interesting thing to note though, is that they also said that if he'd had it mapped and NOT installed the filter, he would have seen 5bhp gain, as his car was running so well.

So map = 5bhp
air filter = 2-4bhp
Map AND Filter = 16bhp/15Nm

Just goes to highlight what people have believed for years - Most mods are best made in conjunction with something else, just to get the best out of them!

In reality the airfilter is to filter air into the engine wether being it in a box or not, but the style being cone or sponge i.e. (itg e.t.c.) is cosmetic looks.. if losses are 1bhp, are you really gonna notice that? cosmetics in the engine dressing looks nice and lighter then retaining the original factory airbox, and noises can be hear more in the exhaust department if you have an aftermarket exhaust system, fortunatly for me i hear it in the engine having TB and also at the rear boxs cos i have two on my car, one at each end (E21)



j

Does Dave F not make a kit for the E30 then? My mates got one on his E36, and that sounds

Simple reasons to add too whats already listed why factory air boxes often perform better

Noise inside and outside
emmissions
fuel economny
to ease or to make it complex servicing so you have to goto a dealer
less variation in temperatures
slow down the air entering the engine
reduce risk filter element from being damaged
keep the water out
to correct the length of the intake system
to either maximise performance all round or to restrict it on purpose (tends to be smaller cars after mid 90's)

When manufacturers say such kits with trumpet shaped cones and vortexs is absolutely 110% rubbish what about the mas/maf air sensors, idle controls, the corragrated intake hoses and so on they are all restriction which un-does whatever the intital cone shape induction kit does straight away

The major criteria everyone should look for when buying a new filter or kit is what micron it is able to filter out dirt and how capable the filtering element is but everyone goes for noise and looks

There is ofcourse execptions to the rule ITG, Jetex and Apexi have better than most filtering characteristics and when induction kit is use on a car which is intentionally restrained for the above reasons to make them greener, nicer, it all helps to fall into lower insurance and tax groups which sells cars these days an induction kit is a good simple power gaining mod in such cases.