Exhaust Drone on New Engine
 

The engine on my 88 Turbo-look 3.2 has undergone a substantial rebuild taking the HP at t wheels from around 200 to 260+

The engine runs great with the exception of a drone in the 2,500-3,200 RPM range that makes the vehicle almost unusable for anything but track applications.

The exhaust is currently a Billy Boat Header System with Heat Exchangers and a BB muffler. This is the second muffler iteration from BB - their first version was a single unit the current installation is two mufflers - one on each side.

Does anyone have a suggestion about how to get rid of the drone without sacrificing performance?

Thanks

I haven't looked at the BB website to look at the orientation of your system, but one idea is to add a couple of free flowing resonators. Dynomax makes a nice small bullet shaped stainless race muffler that makes a nice resonator, and based on its straight through construction shouldn't add much restriction at all. If you could somehow fit those into your system, that might take care of the droning.

I had a BB exhaust on my SC and the drone was so bad I would get dizzy and nauseous. I got rid of it and got a MIlle Miglia and it is sublime in everyway. B&B is junk. Porsche Exhaust, Porsche Muffler - Mille Miglia - High Quality Performance Exhaust

Do you have the single or dual out muffler? I had bad drone with my single and converted it to dual, it was a lot better. I think I also tried some baffles inside the outlet pipes too and helped a lot, it was just a round disk with holes in it spot welded inside. I know you shouldn't have to do all this to an expensive system but!

Conatact/Dealler for Mille Miglia Exhausts
 

Do you have a dealer or contact phone for Mille Miglia exhausts. Their web site does not seem to be very responsive today.

I have heard good things about their products.

Montanaro, Yeah I don't know what is up with their website today. I was on it not too long ago and everything was working fine. So I would just check back in a few days. I have the single in dual out on mine and everyone that hears it loves it. Plus at hwy speeds there is NO drone whatsoever.

Here's a video of my 3.6 with a magnaflow. Not too loud, not too quiet, and no drone:

1974 Porsche 911 with 3.6 and Magnaflow - YouTube

The problem with the B&B headers is you are choices for muffler are basically B&B as nothing else fits.

Not sure how other owner's exhaust systems are going to help your situation, especially if their system doesn't use the same components. An owner with the same/close engine with an identical exhaust with less drone would be the best indicator.

Off hand, I assume you're not looking for a wholesale replacement system but a progressive, cost-effective solution. I'd begin with blocking off one muffler outlet (if both banks merge at some upstream location). That usually works. The next step might be to install a connecting (crossover) tube between the HE outlets and the muffler inlet(s). Beyond that, modify or replace muffler(s). Thin wall mufflers (stainless or otherwise) tend to drone. Anedotal: My Dansk 2in/2out stainless muffler drones only at 2900-3000 rpm.

Some, all or none of these might produce the same power. Depending on the final drive ratio and gear selected, it's also possible to minimize being in the rpm-drone range.

Sherwood

Thanks for the replies
 

The first BB exhaust configuration was two in/two out. We did plug an outlet and it helped a little.

The current BB exhaust has a muffler on each side.

Adding a cross-over pipe before the mufflers was the next step I am considering but I was hoping someone, a was suggested above, has had success in a similar situation.

I am still trying to figure out how to get a hold o Mille Migila Exhausts as their web site seem to be misbehaving for the past several days.

Thanks,
David

Montanaro - try info@millemiglia.com.au or then phone # +61 2 9326 0325

David,

If you really want to fix the drone, you will need a muffler of sufficient volume (like the factory ones) and that means a custom solution due to the proprietary B&B header spacing.