Megaphone 'Cookie Cutter' Exhausts

Andy · Post by **Andy** » Sat Jan 06, 2007 1:43 pm

Ok

Please can one of you techies tell me why some megaphones have cookie cutter ends, not esthetics I presume?

hot66 · Post by **hot66** » Sat Jan 06, 2007 5:01 pm

the cookie cutter bit is actually an insert with a 'spiral' (cork screw style) going down the length of the exhaust pipe

Lightweight_911 · Post by **Lightweight_911** » Sat Jan 06, 2007 5:56 pm

The 'cookie cutter' inserts in the end of the megaphone are intended to create a scavaging effect inside the megaphone ('coanda' effect) which aids exhaust extraction.

They also have the added benefit of preventing the ends of the pipe from collapsing if you ground them.

James, most megaphones do not have any spiral attached to the cookie cutters - those in the picture below were custom-made for Kurt Zimmerman in an attempt to quieten down the ex-917 megaphones on his 3.5litre twin-plug slide-valve Ginther Tribute car (Sloop II):

hot66 · Post by **hot66** » Sun Jan 07, 2007 9:05 am

thanks Andy, I was under the impression the originals had the spiral s

steve wright · Post by **steve wright** » Mon Jan 08, 2007 9:18 am

great paperweights for the desk Andy

911flyboy · Post by **911flyboy** » Mon Jan 08, 2007 11:01 am

Andy,
Was it your silver 911R at CLM that had these fitted or was it Alans? How loud, other than very, are these things?

steve wright · Post by **steve wright** » Mon Jan 08, 2007 11:15 am

mine were about 140 decibels at 4,500rpm... a bit over the top for a track day

I used to push the car out the garage and coast down the hill otherwise it rattled the windows in the neighbours house.

911flyboy · Post by **911flyboy** » Mon Jan 08, 2007 11:24 am

Fair one! The dansk twin tip muffler is probably or more sensible option then. Those megaphones do look great though!

steve wright · Post by **steve wright** » Mon Jan 08, 2007 11:39 am

take a look at my post a few weeks ago on the difference an exhaust makes before you purchase...

Lightweight_911 · Post by **Lightweight_911** » Mon Jan 08, 2007 5:01 pm

911flyboy - I was at CLM with my silver 911R-inspired car fitted with megaphones - but they weren't the type shown above with the cookie cutter inserts (they were short stainless steel versions).

The silver 911 you're referring to was almost certainly Steve's car.

As for the noise level, you need to ask people who were following me - the noise inside the car was glorious !

hot66 · Post by **hot66** » Mon Jan 08, 2007 5:07 pm

Lightweight_911 wrote:

As for the noise level, you need to ask people who were following me - the noise inside the car was glorious !

the noise outside was glorious too

Ian Gunney · Post by **Ian Gunney** » Mon Jan 08, 2007 8:04 pm

I can still see the guys face when you went past him through the tunnel at CLM Andy - you didn't need to speak French to understand him

IanMcLeod · Post by **IanMcLeod** » Mon Jan 08, 2007 9:26 pm

steve wright wrote:mine were about 140 decibels at 4,500rpm... a bit over the top for a track day I used to push the car out the garage and coast down the hill otherwise it rattled the windows in the neighbours house.

That's approx 12 times louder than a loud track day limit (105db)

:-o

Ian.

steve wright · Post by **steve wright** » Tue Jan 09, 2007 8:56 am

I must admit I've given up on the megaphones principally because I couldn't get the fueling right with the standard injection pump but also because I was having to wear ear plugs whenever I drove it.

Coming home from an early drive one morning, my wife could hear me 3 miles away

It was at that point that I realised it was only a matter of time before the boys in blue questioned whether it was standard in period