3.6 Exhaust Solution - Finally! Pics

[Mike Feinstein]

One of the biggest challenges many of us face in performing such an engine swap is coming up with a great performing and great sounding exhaust system especially if you want to retian the stock HE's and have useable heat. 993 HE's are hard to improve upon so I really wanted to stick with them.

My original system was developed in a neighborhood muffler shop after hours. Here's a pic:


It quieted the engine just fine but it seems that it was really wasting precious hp's in the process. After a year of use (and about 5 DE's) the Magnaflow muffler had turned dark blue in the center indicating extreme overheating. My car spent some time in the hands of a respected tuner (Motor Werks Racing) getting some upgrades and dyno tuning (including reworked injectors, street and track chips burned, and lo and behold, a new custom exhaust system).

Here are some pics of what we came up with. The pipes exiting the HE's are 2.5" and flare to 3" at the muffler inlets. Note that there are stainless clamps that are easily removable to release the tips (or rotate them down for the noise meter at the track). This allows for removal of the disc/baffle system for track days. The baffles are about 5" long with 3 concentric discs with holes in them. The opening of the baffle has a 1" hole and the back end is capped off. This forces exhaust gas through the center of the baffle and out through kevlar baffling material before exiting the tail pipe. Mufflers are 5" Dynatech racing mufflers.



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The sound without the baffles is amazing. Very low throaty tone with substantial volume. Fortunately, there is minimal drone, possibly due to the changing diameter pipes. The Dynatech mufflers are straight through with only a parallel mesh screen in the exhaust path. This will obviously be the track setup, and the track chip was tuned for this setup.

With the baffle, the cadence and timber are identical, with less volume. Much more tolerable for the street. The entire system was ceramic coated to help keep the heat inside the pipe where it belongs (hot air flows faster...or so they say).

With about 200 miles under my belt since everything was finished, I am a very happy camper. The car pulls like a freight train with seemingly limitless intensity which builds strongly as the rpm's increase under WOT.

I've often said that if given unlimited funds to buy or build the perfect sports car, I wouldn't come up with anything different than I have now. This recent change has taken it to the next level. For me, this is nirvana.

[anthony]

Since you did dyno tuning, did you come up with before/after figures for the new exhaust?

Looks awesome btw!

[Jack Olsen]

Looks great.

It looks like it would be louder than what you had before though. Is it?

Did you consider criss-crossing they two pipes instead of the U-turns?

And it would seem to be easy to A/B those two systems on a dyno. Did he? Also, how'd the new chip/tuning help?

[Mike Feinstein]

Unfortunately, I don't have numbers that were specific to the exhaust change only. Chip tuning, Bosch F-3-CS race plugs, injector rework and balance, and exhaust netted me 31 hp with the track setup and 29 for street.

Interestingly, I dyno'd 260+ on a dynojet a few months earlier. Identical setup on a dynapack was 221....now 252rwhp. Further proof that there is no consistency between dyno systems. There is a very noticeable improvement on the butt dyno. Of course, lap times will be the proof. Will be doing a NASA event in March. Counting the minutes.


Jack...I asked the same question about crossing over the pipes. My mechanic told me that 993 motors seem to perform best with no mixing of exhaust gasses between banks. He's apparently built these systems before for 993 race cars with good success. I'm also assuming that the KISS principal applies here. With the cost of dyno time and his time, I didn't spend the money to swap exhaust systems to do a/b comparisons...although it would have been interesting.

Regarding volume, yes, in either configuration it is louder, but it's a different...and I'd have to say, better sound quality. I guess it's due to pipe diameter but it's definately a deeper, throatier timber in either case. With the baffles in place, it is very tolerable for my taste on the street. The benefits of chip tuning will hopefully become apparent at the track next month.

[ischmitz]

Nice setup. My Magnaflow can has also turned bluish but it does not bother me. I figure I could take some rubbing compound to it but that's low on my list.

I am more curious as to where your additional HP comes from. If you still have your old exhaust a 1:1 comparison of power and noise would be really interesting. How is the sound compared to the old setup?

Cheers,
Ingo

[typ550]

Having heard Mike's exhaust, with and without baffles, just this morning, I will say the sound kicks butt!

[Jack Olsen]

I didn't mean to do an X- or H-pipe, but just to straighten out the outlet pipes from the collector to the mufflers, one going over the other (and the other one going under), so that both paths were straighter. (Imagine crossed arms for a visual.)

I imagine that oce you're that far down the exhaust path, it doesn't really matter, though.

Is the 31 hp increase relative to the setup you had before, or stock? Were you running a stock chip before?

[Mike Feinstein]

Ingo,

It was explained to me that the Magnaflow is designed/intended to have inlets on one end, and outlets on the other. There is an >< (sideways X) design inside the muffler. For our purposes we were forcing exhaust in each end. Where the gasses meet under pressure, there is a tremendous heat buildup and backpressure created. It then exits out each end on the other (longitudinal) side of the muffler. None of this is emperically confirmed by anything but a dark blue M-flo at the center of the system. At least that's the story...FWIW. It also seems that mine was poorly welded with at least 2 or 3 exhaust leaks that couldn't be seen from underneath.

Chris....thanks for the kind words.

Jack.....your description makes sense, but I don't really know the answer. I'm guessing it's related to the KISS principal. The system is so short and open, that I'd be surprised if there is any hp difference to be gained in either case.

The hp gain is relative to the setup I had before, but Matt found a few issues that certainly would have contributed. For one, my V-ram flaps weren't perfectly calibrated...they are now. I was using a Cyntex chip sourced from Dr. T, but it seems that it was burned for a US DME....mine's a Euro version. Needless to say, there were numerous fault codes and it's likely I was running in a "safe" mode and didn't even know it! Furthermore, my injectors were not well balanced (flow calibration). There wasn't time or money to do dyno pulls after each step. My goal was to get the car optimized and put this chapter to bed without selling my offspring. So, there were many contributing factors and I have no idea what percentage can be attributed to the exhaust change alone.

The funny thing is...I had no idea that things were amiss. Compared to the stock 3.2, it was a night and day improvement. With everything dialed in, I am confident that all is right now. The whole project came about when Matt noticed that I had belched a flame out my left tail pipe upon deceleration coming into turn 1 at RA. This tipped him off that there might be a duty cycle or injector problem on one side. It went from there...

[VincentVega]

Very cool, thanks for posting. I was going to install a magnaflow just like yours but might rethink that. Power is key, but I need to make sure it's not too loud. Any sound clips?

Is the magnaflow available??

[Mike Feinstein]

Chris,

We had cut off the flanges to use on the new system and I told Matt to toss the remaining bits. No, sorry, no clips. Volume tolerance is a very personal thing (and hard to discern through small PC speakers). Typ550 (the other Chris above) said he would leave the baffles out all the time.

[rattlsnak]

Mike, thanks for the ideas, Im going to be building mine soon and cant decide what to do. I do have another option Im playing with though, since my car is a '72 and dont have the oil tank in the way, Im seriously thinking of going with the SuperCup setup. (same one I used on my 993)

Where did the inserts come from? they look exactly like the CC inserts that I used on mine. http://www.carchemistry.com

[randywebb]

Have you done dyno runs with the inserts in & out?

[k9handler]

Nice Mike....I may need to look into that type of system when I return to the US with mine.

[ScottKelly911]

that looks like a great system, I'd love to hear it. Can you post a wav file?

[Mark Howard]

Mike - is that the same Targa you bought in Baton Rouge? If it is, you have done some work to her! Love the exhaust, coolest design I've seen!

I'm still stuck in Afghanistan, only two more months! Can wait to get back to the garage. My girls will need some TLC after being stored for a year.

Mark

[Mike Feinstein]

Mark (Rattlesnake)....yes, with no oil tank to get in the way, you have more options. The inserts came from Dynatech, but I suspect they're an exact ripoff of the Carchemistry version.

Randy, no dyno's with inserts in and out. Next time I'm on the dyno, I'll give it a try. We suspect the inserts are costing 8-ish horsepower...that's why they'll stay in the toolbox at the track.

Mark, yes, it's the very car that you checked out for me 3 years ago. Glad to hear there's light at the end of the tunnel. Get home safely man. And thanks for all you're doing!

[911nut]

Originally posted by Mike Feinstein
The whole project came about when Matt noticed that I had belched a flame out my left tail pipe upon deceleration coming into turn 1 at RA. This tipped him off that there might be a duty cycle or injector problem on one side. It went from there...

Sounds like that was the source of your muffler overheating problem.

[MuffinMan]

Mike, the exhaust looks great! Congratulations on moving your car to the next stage. The shop that did my 3.6 transplant also makes custom exhausts. Although I did not use their setup, it looks almost identical to what you're running, with the difference being the use of Spintech mufflers. Nevertheless, they said they did back to back testing and added a simple "connector" pipe between the two separate pieces, and it gave them more power. Unfortunately, I can't remember the actual number quoted, but they said it made a notable difference. I'm looking forward to seeing (hearing) a video if you get the chance to make one!

The black box in this illustration is the cross/connector pipe my shop was referring to:

[warpspd]

So what did the exhaust setup cost you?

[warpspd]

Dynatech mufflers are about $100 a piece according to their web site.

Did you have to cut the factory headers to use the three bolt flanges? I think my headers have different flanges. They are three bolt but not as symetrical. I think this is the type of system that I am going to go for too. I am using the factory cat right now so I could get on the road but I am going to ditch it soon. Any more info on the setup would help us 3.6 guys...