My new neighbor moved in yesterday and he has 14' 911 S with Porsche sport exhaust , After hearing it, brought to the forehead again how weak my exhaust is and how awesome his sounds. I have a 997.2 c4s with ECU flash and Fabspeed comp intake - I think I lost a bit of low end torque but gained a bit at 5k+ and gained some better sound around there too with intake . I was thinking of gundo hack but read about some people losing low end torque. I love my car BUT am not willing to lose any more low end torque - the c4s is not a torque monster to begin......gundo seems like an inexpensive remedy but any thoughts on loss of torque?

 

I remember seeing posts about muffler delete pipes causing loss of torque. But nothing on Gundo/Fister/PSE. In many ways a Gundo/Fister muffler mod mimics the Porsche designed PSE. And Porsche does not have lower performance specs for cars with a PSE. Although not scientific this is enough for me to sleep at night. My 997.1 Fister'd exhaust sounds great and I do not have loss of low torque as a result.

 

I have Gundo Hack... and there's no real noticeable lack of torque. Even if there actually is some loss... it's not like you'll get into your car and be like... "OMG... it feels like I'm driving a Honda... no damn torque!"

You won't notice it.

 

Just finished up a "Gundo" mod to a set of our Maxflo mufflers that week. Results for performance were "Low end throttle response honestly feels better and midrange feels slightly stronger." I can imagine this effect being more substantial on a set of factory mufflers.

That being said, on the 997.2 our center muffler x-pipe has always been a very popular upgrade and brings out the true spirit of the car. It pairs very well with headers and modified/upgraded mufflers, and is always our go-to bang for the buck improvement for this car

 

I have a Fister D Mod on my 997.1 carrera S with an inch 3/4 cross over pipe ,,,the only difference I noticed was the great flat six sound that the stock mufflers didn,t give , I certainly would say that there was no loss of toque that I can feel ,,best value for money mode in my opinion and very easy to do ......

 

Rennlist is an amazing place. Tons of info & great people who are passionate about their cars.

One thing it isn't, is definitive. Until someone shows me a dyno sheet of before and after results regarding torque loss, its all speculation. We'd all love to believe our butt meters are well calculated. Sorry- you wont feel the loss of 2 or 5 ft pounds if indeed its there.

So- dont believe the hype. Unless youre racing in IMSA. But i think you'd have access to a dyno.

 

I am curious as to how a very minor modification to the exhaust flow aft of the cats could detrimentally affect engine torque?

 

My 2010 C4S manual definitely lost some very low end torque from the gundo hack. The only time I feel it is when I start from stop like at a light...I find my self needing to give more gas/revs when I start.
I actually stalled it a few times days after I got gundo done on car. It isn't a deal breaker the sound and high end power is worth it.

 

I absolutely felt a difference in heft after the fisters went in. It was very noticeable, and in fact I was kind of bummed about it for a few days - thinking I'd traded get-up-and-go for a little noise. I don't race IMSA, but I know I felt a noticeable difference when I stepped on the gas.

Granted, it's a great noise - but having some grunt in the 1800-3200 range is also important to me.

I whined about it for a minute and then I got over it. The only thing I could do was swap back, or push further.

I ordered up some fabspeed headers. I got the high flow cats/X-pipe too. Ok - and some overpriced bigger quad tips. (Why not?)

Then, I got an IPD plenum, and put a GT3 throttle body on there.

Welp. While we're here... might as will get an EVOMS CAI in there too.

Once all that was in, I had a custom ECU tune (protomotive). Ok. (Wipes brow, parks wallet) I believe I've had enough...

I got in the car, torque problem? Gone.
Volume and sound? Supreme.

Do I Got beef with Fister?
Oh hell no! Dude rules.
Do I Got beef with Fabspeed?
NAW!! They're awesome too!

But, suddenly my eyes went to the suspension.

So... be warned. It's a slippery slope.

 

I didn't notice any loss of torque whatsoever after installing the Fisters on my car.

 

2009 C2S 102K miles

I put on the Sharkwerks cross pipe and could feel no change despite Sharkwerks claiming an 18 HP increase. My point here is that 18 HP can not be felt IMO, it would have to be a pretty big change.

Peace
Bruce in Philly

 

True Petrolhead What did you go with for the suspension and how do you like it?

 

It is a misunderstanding of why some manufacturers have the valves open after 3.5k rpm or some level near there.

There is speculation / rumor that it is due to torque at the low end. The "Real" reason based on my direct research is that in some areas they have noise regs... now those noise regs are typically set at a certain RPM (tends to be city "cruising" assumption) and that RPM is (surprise) at that "3,500" RPM level or so.

So, for Ferrari, Porsche and others to meet noise regs in a lot of those areas in these cars, their sport exhausts or regular exhausts will be kept quieter below that level and open above that.

Before I bought my sharkwerks I looked into this pretty extensively, including with some reputable folks who had no skin in the game -- feedback was consistent that changes after cats would have either zero or virtually zero impact on torque.

Combining the above, I would not assume any material loss or gain on torque.

My own butt dyno showed zero loss, not that it matters too much since when I drive in a "Spirited manner" I keep revs high anyways.

 

The thought process is that engines needs some back pressure to create low end torque. So by making the exhaust better flowing you are creating a condition where the engine will make less low end torque in exchange for high end horsepower.

 

This is my dyno result on a stock 3.6 DFI with the addition of headers and high flow cats, the car already had third muffler delete and gutted mufflers on the baseline run.
Solid lines are baseline, dashed is after the addition of high flow cats and headers.