Nizer

Anyone have experience with this system?

https://www.cargraphic.de/en/your-ve...ngtkitxghflap/

boomboomthump

I've done an extensive amount of searching (including YouTube) and all I've been able to find is a few clips of the mufflers only or mufflers + sport cats (and mufflers + Cargraphic modified stock cat).

Haven't found any clips or info including the headers or even the muffler versions which have valves in them.


I have it in my head that at some point I'd like the full version that includes the valved mufflers.

Bill Verburg

The issue is the merge
look at the following closeups of 993 exhaust flow
993


993RS


993ss

993RSR sprint



I only show the intake for 993 but the same patterns exit for all

ideally you want smooth non turbulent flow w/ a some space between pulses, the space is a partial vacuum but only when the sides are kept separated, merge them and there is no longer a vacuum between pulses, and turbulence is introduced to the system the amount of the turbulence is determined by the specific geometry of the merge. When the merge is properly done as in a good collector there is no problem and the flow can even be enhanced/ The larger and more oblique the merge the more of an issue is introduced.

.The whole point of merged sides is an artifact of odd fire engines which a Porsche flat 6 is not. It is there to relive the overloading of the collectors by consecutively firing cylinders on each side. When a merge is used on an even fire motor like ours it is introducing the exact issue that it solves on an odd fire engine.

for comparison here's a odd fire engine a Chevrolet odd fire V8


not the consecutive fire of #2 and #6 on the right side and #3 an #1 on the left

instead of a merge they could cross #6 from the right collector to the left and #1 from the left to the right, that's what was done on the old Ford GT40s

Porsche did a similar config on their racing flat 8s depending on the crank configuration used

Nizer

Thanks for the response Bill. Just wish i had some idea of what i was looking at.

Bill Verburg

upper is left side red is exhaust pulse, blue partial vacuum between pulses, shows end of cyl 1 exhaust followed by cyl 2 followed by cyl 3

green is intakes which can be ignored in this context.


lower is the same for the righ ts ide and cyl 4, 5 and 6

notice that densest red zone in one side corresponds in time w/ the densest blue zone on the other side? for best most efficient flow you want separation and no turbulence, imagine the result of the red on right slamming into the blue on the left, the more oblique the angle of incidence the more turbulence is introduced and the poor the flow. I have back-to-back dyno runs showing the effect which is a ripple in the torque curve caused by the induced turbulence, On average torque will be similar just less smooth. certainly, either separated or crossed cat less is better than w/ a cat.



The pulses leave the exhaust port @ 100 to 120 m/s and slow as they cool and turn, so much slower when entering the muffler and even slower exiting it.

at 6800rpm there will be ~ 1.8 pulses in a given pipe at a time, they expand and slow a lot in in the collector the smaller it is the less slowing there w/ proper merge design which also calms any turbulence, the vac from 1 helps pull the next along, there are also acoustic waves moving through the system at the speed of sound in the pipes ~1700m/s in a properly designed open system these acoustic waves create an additional vac. at the exhaust port at a specific design rpm to help suck additional spent mixture out. In a closed i.e. muffled system w/ little I/O valve overlap such as a stock 993 this doesn't really happen to a meaningful extent.

The primary plus for a merged system is going to be acoustic the above-mentioned sound waves will have a larger volume to propagate into this abets decibel mitigation efforts., To do this you want a small connection w/ an acute incidence angle that doesn't promote cross flow, it solely allows the acoustic effects to come into play.

Here's a fuller look at all 4 cycles and effects



and a simpler look at a 4 cyl open system w/ actual instrumented readings

Nizer

Bill, thanks for the more detailed and thorough explanation. I understood the general concept of managing exhaust pulses, but I have a much better understanding now. I guess what's still unclear is how this applies to the Cargraphic exhaust that I posted. Most of the exhaust solutions for the 993 appear to follow similar designs - headers, with or without heater boxes, x-pipe, with or without cats, and the same mufflers, with minor variations. Hard to differentiate between any of them.

This is another full system under consideration. Built by M&M, who know a but about Porsche performance.

https://www.fvd.net/de-en/BES9930010...cell-cats.html

Bill Verburg

The l/r connection is mostly marketing though there are some dB attenuation and tone altering effects

consider carefully the connection between the l/R sides
if the gasses hit head on =><= this is worst case

if they merge at an acute angle w/ little spill over that is the best case except for keeping the sides separated

here's an example of best case design w/ L/R merge


here's what was on a 993RSR


and a good GT3 design w/ cats



The FVD design is better than the Cargraphic

997 tt/rs

Good gt3 design is EuroPipe of course.

Guys 993 RS exhaust is any diffrent to carera s2 ?

Nizer

So more ways to get it wrong with systems utilizing crossover pipe.

Not sure EuroPipe still makes the 993 system. It's not on their website but I've sent them a message.

boomboomthump

At the end of the day, it's not 1996 and we're not talking about competitive cup car racing in the hands of professional drivers where a microcosm of performance gain may be of any real world value.


Personally, I do not like how non-merged exhaust sounds on our motors. Also, 99.99999% of us will be fully satisfied with something that simply sounds nice and puts a smile on our faces.



$0.02

fnckr

A point regarding sound. Many, if not most, of the great sound reviews that Fister mufflers garner are with no changes to the stock catalytic converter pipe. That pipe maintains separation in the exhaust gas from left and right.

Bill Verburg

True. there is no factory system for 993 that merges left and right, factory did connect them for 911 from '75 thru 89 and then a repeat one size larger for 964. these were almost the worst possible designs ever.

I was fortunate to be able to listen to many 993 exhaust variation while doing tech lines at various tracks, among the best are the Fister 2s w/ separated cat by pass or w/ stock cats



The stock 993 muffler is also only so so in design

stock 993


motor sound 993, just enlarges the shortcut pipe


993tt style is the best of the 3, that's what I use.


even the GT3 rear muffler keeps the sides separated except for the acoustic cross just before the tips

Bill Verburg

The sound quality is highly subjective as is the drivers impression of the impact of the x-over on the torque curve

The absolute best I've ever heard is the Fabspeed RSR on my slightly hot-rodded 993 powered C3, haven't dyno'd it yet but it feels much livelier and the torque curve is definitely smoother than the basically open pipes w/ headers that used to use on that car. The Flowmaster muffler that was used there previously was a poor choice as the 2 sides rammed into each other creating havoc for flow efficiency, don't know what the muffler internals of the Fabspeed look like but Joe and I had a long talk about it and I got the impression that the internal flow is similar to the 993tt w/separated sides just in the single can.

For a track car in my area track noise is also a big concern, my system while fine to me for both street and track will occasionally fail LRP sound w/o turndowns added to the tips


here you can see a stock 993 3.6 , separated cat by pass and Fabspeed x-pipe, not the ripples in the Fabspeed torque curve and they have on of the btter designs of that type, of course either is an improvement over the stock and chip tuning could improve any of them

71-3.0-911

Speaking of sound. How much of this cars exhaust is Hollywood magic? I always loved how this 964 3.6 turbo sounded. Starts at about 1:04 and I assume everyone knows the Bad Boys 964...

Nizer

This the Fabspeed RSR system that you're referring to?


Assume this catless version uses the FlowMaster muffler that you referenced?