[louie_perm]

I've figured out what the drone at ~1,500 rpm is related to (at least in my case)--vibrating oil hoses. The hoses that go between the oil pump and the oil cooling radiator vibrate. The pump itself also emits some noise at the same frequency. The frequency increases with engine speed, obviously, and around 1,500 rpm is where something resonates. I say "something" because I'm not sure exactly what is resonating. (The whole apparatus looks to be well constructed and fitted, by the way. So does the IC.)

I've stuffed some pipe insulation around the hoses where they contact various pieces in the front of the engine bay. They don't touch the engine block, so I don't think I have to worry about the pipe insulation melting--it's that spongy black rubber type. I may put some foil tape around it at some point. Anyway, the pipe insulation nearly returns the sound to normal--pre-Dinan--as far as I can remember.

Anyone know of any more-elegant solutions? The hoses are just the right length for the distance they have to cover, so there is no chance of re-routing them.

I'm also 99.9% sure that the extra noise was not related to the turbos, wastegates, etc., for those who might wonder about increased turbo noise. I don't notice any, and I've spent quite a bit of time listening under the hood the past few days while my wife revved the car.

I'm seriously considering getting the BMW Perf exhaust now--I'm just a few miles from Tischer. I don't like Dinan's tips. Maybe then the exhaust drone will cover up any remaining oil pump drone.

[scott@bmwhn]

We had the exact same problem with a customers car and as far has i know the tech just readjusted the hoses. I would recommend bringing it back to whoever installed it and let them know the issue

-Scott

[scott@bmwhn]

BTW the Performance exhaust is very nice and suprisingly more agressive than Dinans

[tooch]

exactly what hoses are we talking about? i have the same issues however i don't have dinan upgrades i'd like to experiment with your fix.

[louie_perm]

Scott,
Thanks for the info. I have to go by the dealer anyway, so I'll check with them about an adjustment. And yes, I've heard the BMW Perf exhaust is more aggressive than the Dinan. I kinda like that idea, plus the perfect fit and the better-looking tips (IMHO).

Tooch,
These are the oil hoses that run from the front top side of the engine, just below where the oil cap is located, to the oil cooler (radiator), which is tucked in front of the passenger-side front wheel well behind the bumper. They run in the space between the front of the engine and the back of the water coolant-radiator fan housing.

You will only have these hoses if you have an oil cooler, and all models don't automatically have one. The best way to tell if you have the oil cooler is to look inside the front passenger-side wheel well for the vent on the backside of the OC radiator.

Caveat: I haven't seen the OE oil cooler, so I'm assuming that the hoses for the OE will run a similar path and look similar to those used by Dinan.