VERY open exhaust for 3.2

Patronus · 06-17-2003, 01:55 AM

I've read lots about exhaust systems on this board for the 3.2 Carrera (I drive a 85 model) and I've been wondering about the topic.

Let's assume noise and emmission is no problem and my car doesn't have a CO sensor (it doesn't). It has the stock headers with factory standard 1-in-1-out muffler.
For track days I am considering removing the muffler altogether and replacing it with a pipe that will give the exhaust system the correct length, but with zero back pressure.

My questions are:
1. The 3.2 peaks at 5800rpm, does anybody know what length the exhaust pipe should be for optimal hp at 5800rpm, if I keep the same pipe diameter?
2. Any idea how much hp, if any, will I gain on my Euro 231hp car?
3. Has anybody played around with this type of 'straight thru' exhaust before?

Thanks

fastbydrmike · 06-17-2003, 03:18 AM

Patronous,

I have an 86 with B&B headers, exhaust, mass flow intake and a chip on mine with no catalitic and and I would say it has more power. It is very loud though. It sounds like a race car and the wife doesn't want to ride in it due to the sound. I am not sure the length of the pipe.

Thanks,
Mike

thrown_hammer · 06-17-2003, 03:37 AM

I am thinking about doing the same thing. Someone suggested it to me. It was masraum(Steve). He may have some advice.

1fastredsc · 06-17-2003, 04:49 AM

The length of your replacement muffler wouldn't matter essentially. It's affect would be little to none. Header runners on the other hand are very much affected by length. Equal length runners with all in one collectors don't just create zero back pressure (not hard to accomplish), but actually get suction. As one pulse of exhaust flows through, the next is sucked by the force of the previous pulse. Hence the reason why ssi's get a little extra power over stock systems without cat's, they're very close to equal length i'm told.
BTW, one affect you'll get from replacing the muffler with just an exhaust pipe is that you'll loose maybe 50-60 lbs over stock muffler.

ChrisBennet · ChrisBennet's Garage

I would think the motor would run lean with that setup unless you burned another chip for it or used the fuel quality switch on the DME to richen it up. My 3.2 runs a little lean with a gutted cat.
Personally, I hate the really loud cars at the track. I don't want to have to use earplugs when I'm at a Driver Education event. The noise restrictions at US tracks have made them a more pleasant place IMO.
-Chris

osidak · 06-17-2003, 05:15 AM

Stock banna muffler (single in single out) packed weighs in at 29.14 pounds. Sold and shipped one early last month.

After rebuilding my engine and before installing SSI's I cranked up my car for the first time sans muffler (heat exchangers and a cat where installed) Car was LOUD. Did this at 9pm next day one of my neighbors came over, he wanted check out my new harley. I explained it was my 911 that he heard.

thrown_hammer · 06-17-2003, 06:17 AM

Would the straight pipe off the cat offer any more power than the iron hotdog or just more noise? I am considering this for DE's and maybe street driving depending on how loud it ends up being.

eurocarrera · 06-17-2003, 06:27 AM

I think this has already been discussed, but hasn't the concensus been that the Dansk pre-muffler in place of the stock catalytic converter, and a dual out (or modified stock) muffler would give similar results? Not as much HP as SSI's but close. I have the Dansk on order, and the first chance I get (i.e. when the kids go out of town), I am going to be welding on a 2nd outlet to my stock 85 muffler.

eurocarrera · 06-17-2003, 06:28 AM

oh yeah - and this setup offers a good sound with the least chance of offending your neighbors in the wee hours of the morning!

masraum · 06-17-2003, 06:59 AM

Well, I have a Cat and an O2 sensor. I removed the muffler and added a short pipe to get the exhaust out from under the bumper. To me it sounds good, it feels faster, but I don't have any numbers to prove that, and I am very conscious about more sound making me think it is faster and have tried to judge based on the reaction in situations that I drive everyday.

It is loud, but not to bad except when you are getting into it and the rpm's are up there. It is not as loud as a Harley, I don't think. I recently had to put the muffler back on for a visual inspection and was amazed at how damn quiet it is. I can hardly hear the darn thing.

It's got the sound that I like, and I lost 25-30#'s, so I enjoy it. To anyone considering it, don't just take off the muffler to test, the cat points into the back bumper and turns the car into a big resonance chamber, so you don't really get an idea of how this sounds (at least inside the car). You really need the exhaust pipe.

I can listen to the radio and carry on a conversation with my wife. I attribute much of that to the fact that I have a cat which I think probably actually cuts a lot of sound that I would have with a totally open exhaust.

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by masraum
It is loud, but not to bad except when you are getting into it and the rpm's are up there. It is not as loud as a Harley, I don't think. I recently had to put the muffler back on for a visual inspection and was amazed at how damn quiet it is. I can hardly hear the darn thing.
[/B]

Hearing loss will do that.

-Chris

Joe Bob · Joe Bob's Garage

You wrote.....Let's assume noise and emmission is no problem and my car doesn't have a CO sensor (it doesn't). It has the stock headers with factory standard 1-in-1-out muffler.
>>>>>>>>>>>>>>>>>>>>>>>>

Based on the above, you are using the stock 911 heat exchangers that exit the heads, go forward, turn into a collector for ALL six exhaust ports, then make a 90 degree turn BACK (normally thru the cat) to the rear?

Am I correct? If so....."I" would lose that set up and get SSIs or headers w/o heat exchangers. They would be equal length and go straight back to the rear w/o all the turns. Attach dual stingers, mufflers or whatever to them.

The faster/easier an exhaust gas has to exit, the freer the flow is......

masraum · 06-17-2003, 07:46 AM

Mike, definitely, if emissions and such are not an issue, then SSI's and a sport muffler, or headers and a dual out muffler.

jhugh · 06-17-2003, 08:35 AM

Hi Bill Atkins! I met you & saw your Euro Carrera at Parts Heaven on Saturday. Nice car!

I've written tirelessly on this board of my exhaust search. End result.. Fabspeed premuff and Dansk dual out. Major improvement over stock and preferable in at least two ways (sound, lowend power) to the GHL headers & 2in/2out that I tried. I also had a B&B single in/dual out that was too loud. Nowadays my car has cams, a Dastek computer and revs to 7400 rpm with no discernible loss of power due to any kind of exhaust restriction. The stock headers are fine!

If I could do it over again, I'd get a Dansk premuff instead of the Fabspeed. The Fabspeed makes plenty of power but it has a slight fitment problem that causes my left muffler outlet to sit lower than the right.

My impression from all my dickery is that homespun jobs (without the benefit of pro engineering) will not make as much power, or be as balanced through the rev range, as products from the folks who've really thought it through... Dansk, basically.

Cheers,

thrown_hammer · 06-17-2003, 09:38 AM

I pulled out all the steel wool stuff out of my cat. Would this make it too loud? What is the steel wool for?

Glasgow 911SC · Glasgow 911SC's Garage

"It is loud, but not to bad except when you are getting into it and the rpm's are up there"

Have you got a sound clip of just how loud it is at idle etc?

masraum · 06-17-2003, 10:57 AM

I've got sound clips, but they aren't too me a very good representation of the volume of the sound. They were made with the speaker on a laptop.

I roll through my neighborhood in 1st at about 3000 and while it is louder than a Cadillac, it is quieter than the Harley down the road and probably some of the pick up trucks around.

http://home.swbell.net/smasraum/911sitting.mp3
http://home.swbell.net/smasraum/1stgrdriveby.mp3
http://home.swbell.net/smasraum/driving911-1.mp3
http://home.swbell.net/smasraum/driving911-2.mp3

http://home.swbell.net/smasraum/flowmastersitting.mp3
http://home.swbell.net/smasraum/flowmasterdriveby.mp3
http://home.swbell.net/smasraum/flowmasterdriving.mp3
http://home.swbell.net/smasraum/flowmasterdriveing2.mp3

The first four are a stock 3.2 with the muffler removed and the second four are the same car, but with a flowmaster muffler in place of the stock muffler.

PeteBrown · 06-17-2003, 11:18 AM

I have the folowing on my '87. It consists of a cat-bypass sawed off with an Edelbrock attached. It's loud, saved at lease 30 pounds and makes the car feel a little faster. Best of all it was cheap.

You can recreate this for $200-300 or Steve Timmins at Instant-G sells a similar setup for about $400.

Glasgow 911SC · Glasgow 911SC's Garage

That sounds like a full on race car!!! Awesome!!!

Don't know if my neighbours would like it arriving home late at night though.

The flowmaster makes a beautiful noise. I would love one considering the great price. Getting it over here could be a problem as could getting a shop to weld the appropriate bits together.

emcon5 · emcon5's Garage

I recognize that green garage floor.

Tom