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Full Version: Factory muffler versus straight thru muffler
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retrotech
I would like any input on performance, dyno info, associated with different mufflers. I have an altered 911 muffler, dual outlet. I would like to replace with 14" stainless mufflers that weigh 3lbs each. I could drop 20# of the rear. But I am afraid that the straight through muffler, will not produce enough, or as much back pressure as 911 type. Result in loosing some mid range torque. Is there anything that could off set this, short of internal changes, cam, etc.?
DanT
don't you have a 2.7 or 2.8 twin plug? If so you want your power up in the RPMs...tht is where those motors live.
The more wide open the muffler the higher up your power range.

We recently had a 2.5L Spec Boxster dynoed with a stock muffler and then with a totally gutted stock muffler...gained about 11 HP higher up in the RPM range...take that for what it is worth.

On my 914-6 with 2.7RS motor I ran a completely gutted twin pipe muffler with great results....I tend to like the look and sound of that muffler compaired with the dual setups. A completely gutted 911 muffler is not that heavy..
brant
911's do fine with straight through as track beasts..

type 4's on the other hand need a cross over or some back pressure and don't do well without at least a collector combining the 2 banks.

(although the really sweet 911, exhausts also have some type of cross over)

2cents.
retrotech
Dan,

Did you sacrifice any performance from 3k to 5k? I drive my car on the streets allot in the summer, along with DE days. It is a 2.8 single plug, 10:3 - 1 compresson. I have been testing on a dyno, getting main jet & air corr. jet, for max power. I love the street midrange, and don't want to loose it. The weight loss at the tail is a nice bonus.
J P Stein
Call or write Steve Weiner & ask him this question.
I asked him a week or 2 ago.
brant
QUOTE(J P Stein @ Nov 29 2006, 06:02 AM) *

Call or write Steve Weiner & ask him this question.
I asked him a week or 2 ago.



you gonna share?

brant
retrotech
JP,

What did he say? I am going to contact Richard at PMO also, but I wanted some first hand input from people that have made the change.
d914
no real back up, but choke down the carbs a little, better venturi effect and mid range, open upthe exhaust for the top end, watch out for the increase in sound output!!

Eric but 40's on my 2.5 and it sounds like its much more streetable vs the 46's I had..

my $0.02!!!
J P Stein
QUOTE(retrotech @ Nov 29 2006, 08:44 AM) *

JP,

What did he say? I am going to contact Richard at PMO also, but I wanted some first hand input from people that have made the change.


Hi JP:


> Steve:
> I could use some advice on an exhaust system for my 914.At present,
> the 2.7L has a Triad muffler....and it's just fine except for its
> weight (28lbs). I'm headed for E mod and need to get down to (or as
> close as possible) to minimum weight (1700 lbs).
>
Understood.

> How important is a balance tube between the headers. I can fab one
> with a disconnect between them if you think it's worth while....I seem
> to remember your saying that it's good for midrange power (which is
> important in AX).
>
Its very important for low & mid-range power.

> Assuming the above is a good plan, what about stingers?
> Light weight is important ....and noise is an issue...tho not as
> important as weight.
>
Not good for anything except open track and only in an engine with
aggressive cams.

> Anything you can advise is better than the crap rolling around in my
> head.
>
I'd suggest a Flowmaster Series 80 muffler. Its a dual-in/dual-out and
works very well. Plus, its light.

--
Steve Weiner
Rennsport Systems
Portland, Oregon
503.244.0990
E-mail: porsche@rennsportsystems.com

For Porsche High-Performance Parts, Upgrades, Racing Components and
Performance-related Information,
Visit Rennsport Systems on the Internet at:
http://www.rennsportsystems.com

----------------------------------------------------------------------------------------------------------------------------------------------------
So there ya go. He has told me in the past that he has done the dyno work to back this up and he's never steered me wrong before..... and as I've said in the past.....pick your gurus with care.
retrotech
Damn, that exactly what I didn't want to hear, but knew. I want that free weight also. I will check Flowmaster site.

Thanks
Randal
QUOTE(retrotech @ Nov 29 2006, 04:11 PM) *

Damn, that exactly what I didn't want to hear, but knew. I want that free weight also. I will check Flowmaster site.

Thanks




If you call Flowmaster you can talk to a technical specialist. In some cases they are willing to do dyno work with your engine to confirm the power profile.




J P Stein
99.95 from Summit Racing.
http://store.summitracing.com/partdetail.a...mp;autoview=sku
drew365
When I dyno'd my 2.7 twin plug we did 3 pulls:
1. SuperTrapps w/ 18 disks, 196.5 h.p. @ 7K, 165.9 Ft. Lbs @ 5100
2. SuperTrapps no disks wide open, 186.8 h.p. @ 6800, 162.7 Ft. Lbs. @ 5200
3. Magnaflow mufflers (a V8 type, real loud), 188.6 h.p. @ 6600, 165.8 Ft. Lbs. @ 5100

I can post the sheets if you want to see them but I got the best results with 18 disks in the Supertrapps which gives it some back pressure. I should have dyno'd it with less disks but we ran out of time. Fewer disks would create more back pressure. I've had the engine rebuilt since I did these pulls so I would like to do another session. I'll let you know when I do.
retrotech
Enough said, I'm putting my modified 911 muffler back on.
I got up to 214.6 hp @ 5900, 186 ft lbs @ 5900. My HP drops off a bit after that, because it leans out.
drew365
I thought I should add that I remembered last night I took 13 disks off the SuperTrapps at the track and went out with 5 disks which is much more back pressure and the car was a pig, no power at all. I only ran half a session and came in and put the rest of the disks back on. This wasn't dyno, just seat of the pants but for my car a little back pressure works, too much chokes it.
Randal
QUOTE(drew365 @ Nov 29 2006, 09:42 PM) *

When I dyno'd my 2.7 twin plug we did 3 pulls:
1. SuperTrapps w/ 18 disks, 196.5 h.p. @ 7K, 165.9 Ft. Lbs @ 5100
2. SuperTrapps no disks wide open, 186.8 h.p. @ 6800, 162.7 Ft. Lbs. @ 5200
3. Magnaflow mufflers (a V8 type, real loud), 188.6 h.p. @ 6600, 165.8 Ft. Lbs. @ 5100

I can post the sheets if you want to see them but I got the best results with 18 disks in the Supertrapps which gives it some back pressure. I should have dyno'd it with less disks but we ran out of time. Fewer disks would create more back pressure. I've had the engine rebuilt since I did these pulls so I would like to do another session. I'll let you know when I do.



Interesting.

The guys at Flowmaster say that backpressure is vital and is built into their design. Wish you could have tried that muffler that JP linked.
J P Stein
[quote name='Randal' date='Dec 1 2006, 10:55 AM' post='827154']
[quote name='drew365' post='825765' date='Nov 29 2006, 09:42 PM']
The guys at Flowmaster say that backpressure is vital and is built into their design. Wish you could have tried that muffler that JP linked.
[/quote]

I'll tell ya what, I'll try it. I'm happy with the Triad set-up...power wise....
gots more than I can put to good use now (a personal problem biggrin.gif ), so the investment is for a weight loss.
Anybody want a Triad muffler...moderately cheep..only used on Sundays by an old guy.
Randal
[quote name='J P Stein' date='Dec 1 2006, 04:18 PM' post='827435']
[quote name='Randal' date='Dec 1 2006, 10:55 AM' post='827154']
[quote name='drew365' post='825765' date='Nov 29 2006, 09:42 PM']
The guys at Flowmaster say that backpressure is vital and is built into their design. Wish you could have tried that muffler that JP linked.
[/quote]

I'll tell ya what, I'll try it. I'm happy with the Triad set-up...power wise....
gots more than I can put to good use now (a personal problem biggrin.gif ), so the investment is for a weight loss.
Anybody want a Triad muffler...moderately cheep..only used on Sundays by an old guy.
[/quote]



The flowmaster folks were pretty helpful JP. I'll bet they can figure out what is perfect (and light) for your car.


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