How easy / hard is it to get E30 325i Sport to sound like ..

[161BMW]

How easy / hard is it to get E30 325i Sport to sound like .... TVR I6 :-) ?

E30 has normally aspirated I6 2.5 litre M20B25 engine

Thanks very much :-)

[stevesingo]

Individual throttle bodies and a cam with fast open/close rates would be a start. Add in a exhaust with only one straiht through silencer and you will be as close as you could probably get. Still not very close though.

[J4CKO]

Lighter flywheel ?

[161BMW]

Would it not be possible with straight through exhaust with x pipes :-) ?

[Lowtimer]

If you propose to run it on the road, not unless you want to get nicked. If you propose to run it on almost any track in the UK, also no, unless you want to be banned. Also, your exhaust will do nothing for the induction noise, which is a large part of the effect you are looking for.

Edited by Lowtimer on Monday 3rd November 15:22

[161BMW]

Lowtimer said:

If you propose to run it on the road, not unless you want to get nicked. If you propose to run it on almost any track in the UK, also no, unless you want to be banned. Also, your exhaust will do nothing for the induction noise, which is a large part of the effect you are looking for.

Edited by Lowtimer on Monday 3rd November 15:22

You can't get nicked for having a straight through exhaust!!!!

[Lowtimer]

Yes you can, if your car was not put through type approval with one (and is of an age where type approval is relevant, i.e. not a vintage Bentley or something)

http://www.legislation.gov.uk/uksi/1986/1078/regul...

54. (1) Every vehicle propelled by an internal combustion engine shall be fitted with an exhaust system including a silencer and the exhaust gases from the engine shall not escape into the atmosphere without first passing through the silencer.

(2) Every exhaust system and silencer shall be maintained in good and efficient working order and shall not be altered so as to increase the noise made by the escape of exhaust gases.

[buggalugs]

Manifold makes a big difference too.

[161BMW]

There will be a rear box which has a silencer
Centre box removed

[aka_kerrly]

I've heard of a few people who want to ditch their TVR I6 and put a BMW S54 in instead!!

ITB's eg Jenveys or perhaps even E36 M3 S50 bodies plus a fancy exhaust manifold ought to spice up the existing bmw lump.

Or scrap the 2.5 and put a 3.0/3.2 and do it properly?

[Lowtimer]

Ah, you didn't mention silencer boxes. I thought you were proposing simple pipework coming back from the manifolds.

If you still have silencers then all you have to worry about is

a) that a copper does not interpret "Centre box removed" as "altered so as to increase the noise made by the escape of exhaust gases".

and b) that it is not excessively noisy.

If push comes to shove what b) amounts to is, in essence, no more than 80 dB(A) when measured in 3rd gear, at three quarters of max RPM, from a measurement point 7m away and 1.5m off the ground.

The UK law putting it into effect:
http://www.legislation.gov.uk/uksi/1986/1078/regul...

The EU directive setting the noise limit:
http://eur-lex.europa.eu/legal-content/en/ALL/;ELX...

The annex determining the measurement method:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?...

Edited by Lowtimer on Monday 3rd November 18:16

[R11ysf]

Surely displacement has something to do with it too? My Tuscan S is a 4 litre not a 2.5. That must have an effect???

[161BMW]

Lowtimer said:

Ah, you didn't mention silencer boxes. I thought you were proposing simple pipework coming back from the manifolds.

If you still have silencers then all you have to worry about that it is not excessively noisy.

If push comes to shove what that amounts to is, in essence, no more than 80 dB(A) when measured in 3rd gear, at three quarters of max RPM, from a measurement point 7m away and 1.5m off the ground.

The UK law putting it into effect:
http://www.legislation.gov.uk/uksi/1986/1078/regul...

The EU directive setting the noise limit:
http://eur-lex.europa.eu/legal-content/en/ALL/;ELX...

The annex determining the measurement method:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?...

Bloody hell
Thanks for the heads up
Are you a lawyer or something :-) ?
I did so some searches and as far as I could tell straight through exhausts are road legal and will pass MOT
And by straight through I mean basically no centre box just rear box

[Leins]

R11ysf said:

Surely displacement has something to do with it too? My Tuscan S is a 4 litre not a 2.5. That must have an effect???

I would think so! The largest displacement straight-6 that BMW ever made in a car was a 3.8L. I reckon one of those installed in an E30, with a more free-flowing exhaust, might get closer to it, but would still need further fettling to be very similar IME

[Lowtimer]

To be honest I don't think, within reasonable limits, the displacement of an engine in itself makes much difference to the character of the sound. Some of the fattest and most luxurious V8 burbles can be heard out of the back of an old Daimler 2.5 litre V8, or a 3.0 Triumph Stag, and a well tuned 1600cc Triumph straight-six sounds very much the same as a 2.5 litre TR5 or TR6 engine.

Obviously a 37 litre Rolls Royce Griffon V12 sounds very different to a 3 litre Ferrari 250GTO, but a 2.5 litre Daimler can sound very similar to a 6.3 litre Chrysler.

[Lowtimer]

OP, passing an MOT is of course necessary, but passing an MOT does not necessarily make your exhaust legal from the noise point of view

The reason I know about this is I have been through it with a particular car of mine in the past, and ended up changing the exhaust, which I am reasonable sure was actually legal according to road traffic law, but was evidently annoying people, and causing me to be of unwanted interest to the law and the council environmental health department (which you will find has very sweeping powers indeed relating to perceived noise nuisances).

In actual reality, of course people have all sorts of modified exhausts. What it boils down to is that if your neighbours or a passing officer of the law find your car sufficiently noisy that they think you're taking the mick, then you can expect to get stopped at some point and subjected to an attitude test. At that point if they still think you are taking the mick, you might have to jump through various official hoops, including formal testing.

If no-one finds the car offensively noisy, and you drive it with consideration, then in practice you are highly unlikely to be of interest to anyone. But in theory almost any modified exhaust which the general public find excessively noisy MIGHT put you the wrong side of officialdom, which is not a good place to be even if you are technically legal (and frankly, I am not in the habit of having my cars formally noise tested to prove them legal, and I'm sure you're not either).

Use common sense and discretion and I am sure you will be ok.

[161BMW]

Thanks for the heads up :-)

[MagneticMeerkat]

Lowtimer said:

To be honest I don't think, within reasonable limits, the displacement of an engine in itself makes much difference to the character of the sound. Some of the fattest and most luxurious V8 burbles can be heard out of the back of an old Daimler 2.5 litre V8, or a 3.0 Triumph Stag, and a well tuned 1600cc Triumph straight-six sounds very much the same as a 2.5 litre TR5 or TR6 engine.

Obviously a 37 litre Rolls Royce Griffon V12 sounds very different to a 3 litre Ferrari 250GTO, but a 2.5 litre Daimler can sound very similar to a 6.3 litre Chrysler.

It makes some difference, but not loads. In terms of the Triumph straight sixes they were essentially the same engine with capacity changes. Although the 2.5 had, from the factory, a split exhaust manifold. All the others were a six into one setup. The primary things that affect exhaust note: number of cylinders, number of valves, firing order, aspiration type etc. were all the same.

In terms of the V8s you mention both Daimler and Chrysler were making hemispherical combustion chambers. It's quite possible Daimler copied the Chrysler firing order, to give the burble you describe.

For the classic Detroit sound, produced by two-valve OHV on a cruciform crank, a number of different firing orders were used. The one we all know is 1,8,4,3,6,5,7,2 - used by GM. As far as I recall Ford and Mopar had different setups. Chrysler engines tend to sound a bit more brutal at high revs and idle a bit erratically. For some reason they also seem to spew out grey exhaust smoke. Fords have a more mellow characteristic, especially the MEL big sedan engines. Although the 427/428 race engines have a spine tingling quality at high revs.

V8s are weird anyway, as they don't fire evenly across the cylinder banks. Actually I lie: European V8 engines do. Which is why they sound rubbish. Well I think they do, some people like them, but it's a sort of sanitised sound. Akin to the auto-tuned Atomic Kitten version of 'Tide is High' compare to Debbie Harry (I know she covered someone else, but y'know).

I'm not even sure what point I'm making any more, goodbye.