SSI 2k RPM Drone Is Horrible!

[s2k9k]

Recently installed SSI heat exchangers with SSI GT3 center exit exhaust on my 1980 911SC. Sounds amazing on idle and highway speeds. No drone at all. But in town driving between 1800-2100 RPM, the drone is so loud its causing headaches. Is this with all dual exhausts? Might just have to go back to 2 in, 1 out if the droning is this bad with dual exit.

[Saadi996tt]

I have an M&K exhaust with SSi’s and the drone was really bad but I contacted M&K and they sold me baffle tips that made the drone go away completely. Maybe you can do something similar, if not please let me know If you decide to sell that setup. I will be able to use it on a new build I’m working on.


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[darrin]

you might want to try capping (or installing a damper in) one of the exhaust pipes. 2 in/2 out mufflers are pretty notorious for drone -- see this thread for some good comments/ideas https://forums.pelicanparts.com/porsche-911-technical-forum/735480-drone-mufflers-ssis-backdating-heat-my-head-hurts-2.html

[OldSpool87]

Put an internal cap (driver’s side) on my two out on my SC. Drone is now very minimal and barely noticeable.

[faverymi]

It's your muffler.

There are more livable muffler options. But it's a personal choice.

Opinions are like asses. Everyone has one

[Kevin Stewart]

I had BB headers and muffler with 4" tail pipes. It turned on car alarms driving by and droned. I had 2.5 inch tail pipes put on sounds amazing and it doesn't turn on car alarms or drones, same headers and muffler.

[75 911s]

I haven't found a dual out that doesn't drone at the very least a little, but usually a lot.

The GT/K from Achtungkraft is the best for very little to no drone in my personal experience. No affiliation. I own a MK 2/2 and a custom Bischoff midyear 2 in 1 out that I modified using the old PCA article to make it a 2 out. The MK is light and beautiful, but it howls the most on my setup. I bought the tips which help a bit. For my road trip I close one side because it just gets to you.

My home made bischoff howls a bit too, but less so at cruising speeds.

The Achtung doesn't seem to resonate, but it's loud even at the quietest setup.

I think the best wife muffler is a stock 2/1 out.

[shoooo32]

Most aftermarket mufflers have some drone there - 1800-2000 is not a great RPM to cruise. Try shifting down a gear.

[Bill Douglas]

Originally Posted by shoooo32

- 1800-2000 is not a great RPM to cruise. Try shifting down a gear.

Not good for the engine too.

[Jeff Higgins]

Listen to Tony and Bill - air cooled 911 motors really don't like being lugged like that. That drone you are hearing is nothing more than a mournful cry from your poor motor - "downshift, please!".

Everything just works better if you let these guys spin up a little bit. The fan is blowing more refreshing cool air over the motor, the piston squirters open, oil pressure and circulation improve. All goodness. So be kind, listen to your motor, and let her spin a little. They really like that a lot better.

[Kevin Stewart]

reduce the tail pipe diameter from 3"to 2.5

[s2k9k]

Originally Posted by Jeff Higgins

Listen to Tony and Bill - air cooled 911 motors really don't like being lugged like that. That drone you are hearing is nothing more than a mournful cry from your poor motor - "downshift, please!".

Everything just works better if you let these guys spin up a little bit. The fan is blowing more refreshing cool air over the motor, the piston squirters open, oil pressure and circulation improve. All goodness. So be kind, listen to your motor, and let her spin a little. They really like that a lot better.

Wow this is new news too me. I’m used to letting the motors relax at lower RPM when cruising in town light to light.

What RPM would you consider “shift point” when driving around town. Would be okay to ride 3k rpm or so?

[s2k9k]

Originally Posted by Bill Douglas

Not good for the engine too.

Just learning here so I want to ask, what’s “normal” shifting points for these cars? I always have shifted all cars around 2-2.5k rpm when driving manual and in town driving I’m around that rpm.

[Jeff Higgins]

I consider anything under 3,000 rpm to be "lugging" it. Unless I'm more or less coasting down a hill, or rolling to a stop. In other words, under little or no throttle. If I'm on the throttle at all, even light throttle around town, I try not to let it drop below 3,000 rpm, although I won't get upset if I let it go down to 2,800 or so very briefly. That means I'm shifting at 4,000 rpm or so any time I'm accelerating, even at a "polite" pace around town. These motors really thrive on this treatment, living long happy lives at a little higher rpm than you might be used to, if you are coming from other types of engines. These are not American V8's - they really like spinning up, even under light throttle. Try it for awhile and see how much happier both you and your car are, being a little more "playful", even when slogging through town.

[Bill Douglas]

I'm about the same as Jeff.

[Kevin Stewart]

I have the B&B dual-in, dual-out muffler currently. Because of its massive 3-inch outlets, it resonates like a dentists's drill between 2000 and 3500 rpm. I had the two outlets reduced to 2 inches to eliminate the resonance.

A B&B single outlet is going to be quieter than a dual-out. My advice would be to see how you like the single outlet before you add a second hole, and expand that outlet hole from the size of a nickel on up, cautiously, testing in between cuts.
__________________
Jack Olsen
1972 911

[tobluforu]

I had one on my 72, lasted one year as it was horrible to drive around town in. I luv loud, but it was flat out way too loud for the street, almost embarrassing.
The post above from kevin stewart, uh, are you Jack in disguise, wtf is that all about?

[Kevin Stewart]

Originally Posted by tobluforu

I had one on my 72, lasted one year as it was horrible to drive around town in. I luv loud, but it was flat out way too loud for the street, almost embarrassing.
The post above from kevin stewart, uh, are you Jack in disguise, wtf is that all about?

Hi I am not Jack, this was his reply years and years ago, I tried it and all the droning went away and it cut the volume in half. I was just as surprised as you. It went from just awful to an amazing cool sound.

Every time I drive the car I think of that post and thank Jack Olson.

[Mr. Merk]

I have B&B headers and they had terrible brain crushing drone with the the B&B 2 out muffler.

I had a Borla 2 in/1 out installed and it made a massive difference. The muffler has "broken in" a lot since then and has gotten really loud so there is a bit of drone but nothing in comparison to the 2 out.

The GT3 muffler is what's causing your problem

[G450X]

I have an ‘82 SC, I also tried the GT3 2/2 (with SSI’s) and the drone was rough to take, if I recall correctly, between 2k-2.7k rpm or so.

I went with an M&K 2/1, and it’s much quieter. I also tried a ‘74 factory 2/1, and it was a bit too quiet, but probably perfect for a “don’t upset the neighbors” type community.

If you have the time to search there are several threads on SSI’s and 2/2 exhaust drone.