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-   -   What's the deal with Bursch? (http://forums.pelicanparts.com/porsche-912-technical-forum/62107-whats-deal-bursch.html)

josh912 03-08-2002 11:28 PM

What's the deal with Bursch?
 
I was reading the thread on the 356 sports muffler and Bursch glass packs got mentioned. Why do so many people like these? I had one on the 68 and hated it. It was loud and the carbs and exhaust popped. I put the OEM on and the exhaust quieted down and sounded nice, and the carbs and exhaust quit popping. I also didn't notice any performance difference at all. With that said, whats the big deal?

COLDBASS 03-09-2002 01:54 PM

I didn't have any real affordable options. The PO of my 912E had a custom SS exhaust fabricated. The darn thing was too loud. Only other option was to go with a Bursch, I wasn't able to locate an alternate choice for under $650.00:(

Bob

bob tilton 03-09-2002 06:03 PM

what about dansk (sp?)? i know they make a stock similar to OE and are suppose to be the early banana aftermaket choice? about $325.
bob
68 L

Green 912 03-09-2002 08:05 PM

The deal is they have been tested and refined over many years and they work when used correctly.

Exhaust setups are extremely important on non-injected non-computer controlled cars. Your anecdotal experience with one setup was not a good one. Why? Perhaps you had the incorrect cam timing for the header and the setup was causing you to run lean. Lean carbs will fart and pop. No surprise that you didn’t see any improvement if the rest of the motor wasn’t in “tune” with the different exhaust pulse phasing. When the exhaust valve is starting to open the piston has not even come near the bottom of the power stroke. High energy in the cylinder blasts by the opening exhaust valve and creates a high-pressure wave and the high-pressure wave will, after a certain time, create a low pressure. As the piston ends the power stroke and starts back up it pushes the rest of the remaining exhaust gas out. At the same time the intake valve is starting to open well before the exhaust valve closes. If the intake charge velocity (in this case velocity equals pressure due to the mass and momentum of the air/fuel charge) is not high enough the exhaust will be pushed past both valves. This will even further decrease the flow rate through the carb ventures and really lean things out. The reason we want to create this pressure wave that seems to cause problems is when the timing of all 3 is right the high pressure pulse passes a set point and creates a partial vacuum during intake and helps pull MORE air/fuel mixture into the cylinder during the scavenge phase. The valve timing (cam) and exhaust pulse timing (header) set everything.

Many things go into the planning of a performance enhancement to a 356/912 motor. Size and location (RPM) of the power band, planned use of the motor, weight of the car, gear ratios and the list goes on.

I can tell in a big way when my motor is “up on the cam”. The carbs, cam and exhaust are all working in phase, the power is ON, and the motor pulls. If any of the 3 is not in phase then the motor isn’t producing power as well as its design limits will allow. At one track there are noise limits and my “J” pipe exceeds them. I have to use an insert to reduce the noise and the damm thing kills the power band for anything past 6300 RPM. Change something and you effect all to varying degree. Example. Pop in a “hot” high lift 310 deg duration cam, racers use em’ and get lots of power so why not. You just killed your idle and without the correct carb, intake and exhaust setup the motor will not produce much more power. In fact unless you are in the now much tighter and higher power band you will probably make LESS. When you stray from stock it is important to plan what your goals for the motor are and only then modify accordingly.

For lots of good info explained in an easy to read format get “How to make an old Porsche fly” by Craig Richter. It is out of print but can still be found and is well worth the search if you plan to build a 356/912 motor outside the realm of stock.

josh912 03-09-2002 09:58 PM

Here's the thing though, this was on a high performace motor. The car pulled much better from 2000-7000 rpm with the stock than the bursch. That just don't make sense.

Green 912 03-10-2002 03:36 AM

What is high performance? Hot parts don't always make a good hot motor How did you plan the cam, intake and exhaust timing? Was the header setup ment for a non stock motor? The problem as you discribed sounds like a clear example of missmatching a cam and a header. The effect of the headers on the overall performance of a 912/356 is profound. When I swich from my tuned "J" pipe to a street muffler I have to re jet and the motor amd it still only wants to be "on the pipe" ;) Get the above book. Good stuff and easy to use. Much info on what to use and WHY rather then how to assemble.

silver912e 03-10-2002 08:43 AM

Anyone know a good source for the Dansk muffler?

JuiceMan 03-10-2002 03:46 PM

Mmmmmm, I love the sound of my Bursch glasspack muffler :cool:

mein12 03-10-2002 06:15 PM

Hi Guys,

You can put any muffler you want onto the Bursch header. You can choose the sound you like best. At the track I used a straight pipe. On tracks with dB limit I used a two chamber flowmaster. I now use a polished stainless turbo style with stainless wool pack. You guys have heard this car go by. I think it is loud but not too loud. I am certain that this set-up would work on any 912. In fact I had them make this set-up for me at the Bursch factory/shop. This muffler is usually used on british cars bursch systems. I saw it laying there and asked for one on my set.
It has worked well so far... JMB

Green 912 03-11-2002 09:10 AM

Mein 912 is right on. I use 3 different ends for the header depending on where the car is running. Street, quiet track ands no restrictions track. I can feel (and hear) and can measure the difference in lap times with each of them. If you can weld it is easy to make your own too.

WFBowen 03-11-2002 07:14 PM

Josh:
I'll throw my 2bits in re:Bursch. I think Bursch was the first with the so-called extractor exhausts which, when used on an early 356 (or 40hp VWs) actually gave a little more power (maybe a placebo from the sound, but it sure seemed to work.) As Green & JMB have mentioned, it's all a matter of matching up the exhaust as part of a system. Formula B/C guys, for example, would tune their motors top to bottom; i.e. changes of the intake velocity stacks required re-calculating everything downstream until the exhaust left the pipe. For a rock-stock 912, the factory setup is probably the best, as those Porsche whiz-kid engineers always seem to perfectly tune every part of the motor to everything else.
I think that due to tighter noise restrictions, Bursch has cut back on some of their louder systems (912E glass-pack for example) and what has to be their sweetest sounding system of all - the 3-muffler early 911 system.
p.s. Silver 912E: I'm not sure that Dansk made a 912E OEM type system. I had a Bursch on mine only because there was no other choice at the time - Bursche $250; factory $1140 (if you could even find one.)

josh912 03-14-2002 10:44 AM

Thanks for the input. I just was surprised that the Bursch was no better, even at 7K. 1 year latter, that motor is infact being fitted with an adjustable megaphone (?) with the bursch headers. It will be interesting to see how well it will run.

pel55 01-13-2018 12:50 AM

Quote:

Originally Posted by Green 912 (Post 406359)
For lots of good info explained in an easy to read format get “How to make an old Porsche fly” by Craig Richter. It is out of print but can still be found and is well worth the search if you plan to build a 356/912 motor outside the realm of stock.

The book is available as an ebook now at Vintage Tech Info: https://vintagetechinfo.com

andybullen 02-09-2018 08:35 AM

I have a Bursch and it's raspy and delicious

fbarrett 02-13-2018 12:02 PM

Put a Bursch on my near-stock 912 in about 1969, and half a century later, it's still there. All the stuffing burned out of the muffler, and the pipe flanges needed welding once, but it sounds great. Mine has the detachable muffler, so I can bolt on a straight pipe for track use.


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