altering muffler question. 1 in to 2 out

[FinallyGotOne]

went to

http://www.dietersmotorsports.com/twinpipe911.htm

911 twin pipe muffler conversion.

On my 79 911sc i have been discussing with a mechanic to do this. his belief is that with allowing more flow there will be a noticeable difference in performance.

He said if I removed the catalytic converter for a test pipe, my low end torque will suffer, so i will have to turn up the idle which was not recommended.

What is everyones thoughts and experiences with this. Any performance upgrade with following Dieters recommendation.

[FinallyGotOne]

someone has to have an answer here...

[FinallyGotOne]

stillno answers here. I did do a search but it came up with no real info. other than sound. I'm not willing to do any mods just for sound purposes.

[rs6er]

Before I switched to SSIs, I ran with a cat bypass pipe for years. If anything, the car felt faster without the cat. Can't speak to the dual pipe muffler though.

[Tim Hancock]

FinallyGotOne,

Here is a link to my 2 out DIY muffler alteration I did to my '79 SC. My cat was previously gutted, but I cut it apart and welded in a center perforated tube surrounded by packing to kind of duplicate a cat bypass. DIY stock muffler mod, 1 out to 2 out, SC

As I state in the above post, I did some non scientific timed acceleration tests before and after my mods and I saw no increase or decrease in performance. My mod left the 180 deg perforated tube on the right side of the muffler in place, but I did yank the packing out and added a big outlet hole with a flange added to allow me to bolt in a blockoff plate if the sound ended up being too loud.

[FinallyGotOne]

This is one of those posts that I hope to get many responses from. Tim thanks for the info, I did notice that the one item you did not mention was this :

• Take a cutting torch and remove the U-turn pipe from the end chamber.

I wonder if this does anything in the way of performance?
Also, removing the catalytic converter I am told decreases low end torque, but will increase upper end. I certainly do not want to lose any low end torque.

I know headers or ssi from an earlier year will give me an increase in performance, and my long time understanding is that more unrestricted flow is helpful. It seems odd that TIM did not see an increase in the performance low end? I wonder if he did not remove the catalytic if it would have been better?

LOOKING FOR SOME AUTO CROSS AND RACER GUYS TO HELP ME OUT HERE...

Thanks everyone...

[DanielDudley]

SSIs are wonderful. Nobody ever seems to reccomend anything else for an SC.

[jhubs]

FinallyGot One,

Here is a thread you might want to check out: $100 Muffler Mod 1 in 2 out + Sound & HP

Jerry

[Joe Bob]

You can let all the exhaust all you want but you will still have SIX cylinders, necked down to ONE single pipe, going through....what.....4-5, 90 degree bends, then through a catalytic convertor, then through a baffled stock muffler......

A one in muff with a dual outlet is a waste of time and money.

[jhubs]

FinallyGotOne,

A 1 in, 2 out stock muffler is NOT going to provide you with a "noticeable differende in performance." Very few of us can tell the difference between 217 HP and 221 HP. It is going to be the sound that will be the difference. I've learned one thing on this Forum and that is... Porsche owners love the sound of their cars. If you really want to increase performance that you can truely feel, get a Steve Wong chip.

Mikez is correct, "...you will still have SIX cylinders", but there are a lot of Porsche owners out there spending a lot of time and money putting on SS mufflers, headers, roll bars, tails, spoilers, air cleaners, wheels etc. on their Porsches for a lot of different reasons.

For most of us it's a hobby and hobbies are usually expensive and time consuming, but it's about passion and it keeps us alive and curious. The "Arts" i.e. creativity, do that to us, it's part of being human.

I fly fish and have 6 fly rods worth $4k! I spend a lot of time and money chasing trout only to catch them and put them back in the river. But it's fun, stimulating and a creative outlet.

No matter what you do to your Porsche, have fun doing it!

Jerry




Even if it is just with Photoshop!

[mkossler]

There is no chip-based solution for a stock 3.0 liter 911 SC.

To the best of my knowledge, the choices to improve performance with a CIS-equipped 3.0 are limited:

Add SSI headers or the equivalent with a free-flow muffler like a Dansk Sport or MK.
Grind cams to a 964 profile.
Increase engine displacement (of course) while maintaining compression ratio.
Upgrade Engine.

[jhubs]

Oops, sorry, mkossler is correct. I did not pay attention to the year and model of your car.

Jerry

[Zeke]

Originally Posted by FinallyGotOne

Also, removing the catalytic converter I am told decreases low end torque, but will increase upper end. I certainly do not want to lose any low end torque.

You can't have it both ways. Exhaust is not a dynamic device. It is a compromise to provide the best performance for the intended use of the car.. The reasons for any exhaust modification are for specific performance gains. Most people feel that a freer flowing exhaust and the resultant increase in upper RPM performance (providing that the air/fuel mixture is still correct, or corrected) is worth the loss of some of the lower RPM torque. After all, one doesn't approach the autocross track at 2-3K RPM. But, you can go too far with free flow w/o significant changes to the engine parameters (like compression, or reworked heads).

[FinallyGotOne]

Thanks everyone. Guess I may just stay as it is. I may go the ssi later. that is the advice I needed/