Nizer

Resurrecting this thread as I'm working on a 993 build and trying to sort exhaust options.

Just wondering what I'm looking at in the two pics above. Custom headers paired to a GT3 muffler? At least one the systems appears to have a bypass valve. Anyone know the manufacturer?

listnner

GT3 mufflers?
Cant see the headers, what are they ?

boomboomthump

Both setups are custom headers, not something off the shelf. Also, the mufflers have been shortened.

@Nizer Both have valves. You can see them on @ninjabones car on each side of the muffler. @MB965 has them as well. Here's a better pic of Mike's car...

ninjabones

Interesting timing on this post. My 993 build is making very slow progress. I elected to remove the Dawe custom exhaust setup mentioned above (after only dyno time and maybe 200 miles) as I wanted heat (and couldn’t resolve all the issues/expense related to trying to do it independently from an exhaust heat exchanger). The Dawe setup was also a bit too loud for the intent of this more street-oriented build (even with the valves closed).

Any way, I’ve pulled everything off and was intending to list everything for sale when I have time. Here are the components: custom Dawe headers (3.8L), soul 997 GT3 valved bypass pipes (https://soulpp.com/product/porsche-9...-bypass-pipes/), GT3 muffler (modified/shortened for 993 fitment), end caps, band clamps, hardware and mounting bracket.

I have video and decibel readings from when it was briefly installed. I also have a pristine full sized stock gt3 muffler (unmodified) that I will also be selling (this was purchased from a friend for a different build that has since been abandoned). I’ve shown photos to illustrate the amount of shortening needed for the 993 application. Photos below. I’ll be listing this soon too.

The photos below are for the purposes of this discussion, so I haven’t listed any asking prices yet as this is not my for sale listing (and as most of you know, my asking prices will be a very fair and a fraction of what I paid). Glad to answer questions and further the discussion.








Stock full sized gt3 muffler (for comparison purposes, in the photos above you can see the weld line and how much was removed vs the stock muffler below). I do have black end caps and hardware not shown in the photos.

boomboomthump

I'd be interested to hear the videos. I believe Mike has sent me some of his but I presumed they were valves open.

Also, is there a thread you have going on your build?

ninjabones

I don’t have a build thread on this car yet. I’ll get around to it at some point.

Here’s a few videos with the above-mentioned custom Dawe/Soul/GT3 exhaust (no heat). I measured 105dB (closed) / 111 dB (open). This was a close up measurement, not the 50 ft or drive-by measurement that would be done at the track for those purposes. In the first video, I open the valves at 18s and then close them at around 30s. Also keep in mind that much of the character of the sound in the video is related to the super ridiculous cams (which i eventually swapped out for a semi-ridiculous profile instead of super ridiculous).

boomboomthump

Thanks for posting those! Agree with your wanting to yank it. Quite loud idle for a street car.

Cool setup none the less (definite engine/exhaust ****) and I'm sure someone will want to ****** it right up for their track car. Wonder if there's any way to squeeze some cats into the setup and get the sound more in-line with factory GT3 levels.

Nizer

Thanks Boomboomthump.

Ninjabones, what are you doing for the new 993 setup?

ninjabones

$$$$Cargraphic$$$$. Valved center-exit with heat and cats. Expensive... Yes. But, exactly what this car called for, especially since I had already spent so much time and effort having the rear bumper plastic welded (with heat shields etc) for the center exit. Many discussions and deliberations before eventually going this route (including Gamroth, Dawe and Nick at RSWerks). The heat exchangers are the size of coffee cans, but surprisingly work fine (I’ve tested with ambient temps in the mid 40’s). Not sure yet how’d they perform in severe cold conditions. The sound is still aggressive but much more appropriate for a street application (and my residential neighborhood). Valved for dual character, plus there are cats and heat. I'm very happy with the end result (but this is the third exhaust iteration on this build).

There’s a three-way switch in the center console for the valves (open-closed- or motec controlled to open when the vram switches over at about 5k rpm). The engine build was for max low-end torque and driveability, hence the decision for v-ram (with design input and all the goodies for the engine build from Colin at Ninemeister) in this '95 993 build rather than the GT3 intake in my former widebody 3.8L racecar (that some of you may remember).

MB965

The Cargraphic system looks well designed and built. That puts a lot of plumbing in a tight space! Should give you the lower sound level you want and looks like it plugs right into the factory heater piping.
Sound level is quite user preference, so I think someone will want your previous system. And valves are fun to use
When I did my 4.0 build I wanted max performace with streetable sound level. The Rothsport headers with their valved GT3 muffler really hit the mark for me. In valves closed mode mine is a lower level than yours was.
My GT3 muffler was not cut down like your's and uses Rothsport valve assemblies. Could be that your cut down muffler modifications resulted in higher sound levels in the valves closed mode.
Valves open results in the obvious higher sound level and adds much more low frequency. With the Rothsport MOTEC tuning, valves open mode switches a second tune worth +25 hp and torque at 5,200 rpm.

Sorry I missed your last years post on the gasoline fueled cabin heater. My only excuse is that I was at the Rolex 24. Good thing Bill V paid attention and had some photos! Looks like you have moved on to a new solution for cabin heat.
My desire to have max engine performance resulted in my going down a very deep rabbit hole and eliminating power steering, AC and heat from the engine while still having those systems. It was a major project but fit for a retired engineer to tackle.
Not sure if the heating system details are pertinent anymore.

ninjabones

I am still very interested in your setup, as I appreciate others who also geek out on these over-the-top 993 builds. The gas heater is super cool and I’d love to see more photos and you’re real world usage analysis (sound levels, how you vented the exhaust and ducted the intake, how much heat and noise is generated in the trunk, how fast it heats up and generally how its worked out for you both pros and cons).

We also noted quite a bump in performance when tuning for both open and closed exhaust valves… but even more important for this build (with emphasis on low end torque for the street rather then max top end HP in my old race car) was tuning for varioram intake runner position as well as exhaust valve position.

This dyno sheet is not from my car (I believe it is one of Colin’s builds) that just shows the impact of optimal tuning for vram position and how much low end torque advantage you get with the vram setup. For top end HP, I think the GT3 intake is still the way to go.

listnner

Are those the 45mm long primary version ?
Their 42mm version has a much larger heat exchanger.
Did Colin recommend the 45mm version for your build ? Only asking as in previous discussions he had said stock is best.

boomboomthump

Wow.

Now please tell me there's video clips of this thing like your previous setup...

boomboomthump

I think you meant ID. The 45MM has the smaller heat exchangers. 42MM is the longer ones.

Bill Verburg

Do you need cats?

wrt Cargraphic exhaust pictured here

45mm ID primary is a good size for 3.6 to 4.0 under 7200rpm

the merge after the primary does little to nothing for power/torque on an even fine motor like a 911, in this application it is mostly for sound attenuation

the merge here is also poorly located as is the 90° bend

again for a street oriented motor stock header/heat exchanger w/ non merged cat bypass and modified stock muffler is the best bang for the buck, even the best headers on a muffled system are not going to give anywhere near the results that they do when opened up w/o anything but properly spec'd open pipe after the collector

stock bas muffler are also poorly designed for performance the inlet is caped at the end of the perforated inlet pipe forcing the gasses to exit through the small tuvbe and perforations


a mod is to increase the bypass tubes size

the best mod is to remove the inlet cap and connect the inlet to the outlet w/ perforated tube then rewrap w/ either f/g, ss, or scrapple

You want the tubes to be as straight as possible the closer to the exhaust ports they are because in those environments the gasses are moving w/ the highest velocity and the coast to deflect them is highest, at the ports the exhaust V is ~120m/s +/-, as the gas cools the V drops significantly , the muffler or cat will be the biggest factor is slowing the gas V til it is only a few m/s at the exit too atmosphere.

after properly sized tube, perforated tube , again properly sized is the most efficient conveyer of exhaust gas, straight is always better than curved, changes in cross-sectional area are 2 edged, they can be functional and utile in an open system but not so much in a muffled one.
w/ RS cams there isn't a lot of overlap for any header to bite on, this shows the overlap for a 993RS


compare that to 911S cams shown here, the overlap here gives a an open header something too really work w/