Drone with standard exhaust

[Ick2006]

I'm a newbie here having purchased a great looking 2007 BMW z4 2.5si Sport roadster a couple of weeks ago

It's perfect apart from having an annoying drone between around 1800 and 4000 RPM in any gear when accelerating or maintaining speed up a hill, which is particularly noticeable from the drivers seat, less so from the passenger seat. It's the same with the roof up or down.

MOT was done just before I bought it and the independent BMW garage I've used for years (with a 325i) has done an Inspection II, brake fluid, etc and had a good check-over of the car and can't find any faults.

He says that the exhaust looks like it's the original and is unmodified though thinks the exhaust does sound a little louder than others he's seen.

I've had a good look through the forum for similar problems but can only mainly find related questions from people with exhausts that are too quiet or when modified.

I'd really appreciate any thoughts on this as it's spoiling my enjoyment of the car

[MACK]

I'm a newbie here having purchased a great looking 2007 BMW z4 2.5si Sport roadster a couple of weeks ago

It's perfect apart from having an annoying drone between around 1800 and 4000 RPM in any gear when accelerating or maintaining speed up a hill, which is particularly noticeable from the drivers seat, less so from the passenger seat. It's the same with the roof up or down.

MOT was done just before I bought it and the independent BMW garage I've used for years (with a 325i) has done an Inspection II, brake fluid, etc and had a good check-over of the car and can't find any faults.

He says that the exhaust looks like it's the original and is unmodified though thinks the exhaust does sound a little louder than others he's seen.

I've had a good look through the forum for similar problems but can only mainly find related questions from people with exhausts that are too quiet or when modified.

I'd really appreciate any thoughts on this as it's spoiling my enjoyment of the car

When he said it looks unmodified did he just check for an aftermarket replacement rather than any work to the original. Work to the original is hard to see on the car as most usual cut the top of the backbox off then weld it back on. On the car it's not easy at all to see that area.

[Ick2006]

He definitely said that it looks original and unmolested... even the clamps, etc looked like they've been there and untouched since new. Also mentioned that sometimes the internal baffles rust but the outside looks ok. Plausible do you think?

[Silverzedtom]

I also have a 2.5si and didn’t have any drone with the standard set up. My money is on it either blowing, or someone has modified the back box or resonator.

Have you been under the car and looked at the joint nearest the manifold? These are prone to rusting and would be near you when driving.

[Ick2006]

Thanks to you both for your comments, I really appreciate it. However, you'll have to excuse my ignorance on exhausts...
This I think is a photo of the type of exhaust on my car... is the resonator the bit in the middle before the backbox?

s-l1600.jpg (41.12 KiB) Viewed 813 times

Regardless, I think I'll have to get it to an exhaust specialist. Can anyone recommend one in or near Leeds, that could repair or renew depending on what they find?

[Russ59]

The bolts/nuts that hold the exhaust to the down pipes are prone to rusting away, common fault.
3 out of the 4 nuts on mine rusted away.

[buzyg]

There is a bit of a drone with the standard ///M exhaust, from 1-2k. Not unpleasant, but not the gorgeous mellow waffle, that builds to a wild banshee howl, from 6k upward.

[Wafoo]

I had the exact same problem in my car, an annoying droning across all rev ranges, lucky the fix was easy, just leave the wife at home when you take the Zed for a drive!

[Smartbear]

I had the exact same problem in my car, an annoying droning across all rev ranges, lucky the fix was easy, just leave the wife at home when you take the Zed for a drive!

Yes, the “wife delete” option although very effective can be very pricey when you consider losing half your property/pension etc
Rob

[heavymetalthunder]

Just a thought, could it be the sound generator mod? With both foams removed, it can be a bit loud/drony on acceleration.

[Machine monkey]

He definitely said that it looks original and unmolested... even the clamps, etc looked like they've been there and untouched since new. Also mentioned that sometimes the internal baffles rust but the outside looks ok. Plausible do you think?

If there are any clamps on the exhaust it has been cut and off the car and possibly modified. The BMW exhaust is one bit from the down pipes from the manifold to the very pipes the tips fit on. As mentioned the top is cut off for any internal mods so could be hard to tell without dropping the exhaust.

The exhaust is mad from stainless steel even the internals so unlikely that its rusted or damaged.

The sound generator theory is a valid one and worth checking. If you have a pipe coming off the TB intake tube connection. Heading to the firewall Bulkhead on the passenger’s side below the ECU box then that’s likely the problem. And simply putting some foam back in it will help.

[R60BBA]

Use it as an excuse to get a Supersprint