bmw Z4 2.5si

[Spadey1]

I have a 2.5si Z4 which is claimed to put out 218ps (215 bhp or thereabouts). It goes pretty well although there is a turbo like whoosh sound as you accelerate which I have assumed comes from the airbox. It has set me wondering whether I would see any benefit (aural and performance) if I fitted a different air filter. Has anyone out there tried it with this engine and if so did you get an improvement in power?

[p4cks]

Fitting a new airbox on any naturally aspirated engine will have minimal performance improvements, if any.

[mx5tom]

Unlikely you'll see any performance benefits, but nothing beats the sound of induction roar

[bulldog5046]

if you just want it to make some noise you can remove the foam from the resonator pipe.

I assume its on the 2.5, i had it on my 3.0 when i had it.

looking into the engine bay, on the right hand side at the back there is a pipe that goes into the bulkhead, just pull it out and remove the foam.

[Codswallop]

^^ It's called a 'sound generator', and iirc, only the 3.0 had it fitted. You can retrofit the sound generator to lower power models though.

Edit to add link;

http://www.z4-forum.com/forum/viewtopic.php?f=2&am...

[Spadey1]

p4cks said:

Fitting a new airbox on any naturally aspirated engine will have minimal performance improvements, if any.

I suspected as much but thanks for the repies. I might look at chipping at some point but I have neer been convinced that this does much for a non-turbo either.

[Wizardskills]

Spadey1 said:

I suspected as much but thanks for the repies. I might look at chipping at some point but I have neer been convinced that this does much for a non-turbo either.

Chipping will do very little as well.

[sjj84]

I had a 330 a few years back that I fitted a cold air induction kit to. Improved the noise drastically, but ran like a bag of st.

[shalmaneser]

Spadey1 said:

I suspected as much but thanks for the repies. I might look at chipping at some point but I have neer been convinced that this does much for a non-turbo either.

It will make it sound better, though. Worth it for a few quid and ten minutes with a spanner IMO.

Having said that the Dave F induction kit developed originally for the e36 M3 did have a proven (if small) horsepower gain. don't know if a similar setup is available for the Z4.