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**Disclaimer - I'm sharing to show my exhaust project refresh. By no means am I an engineer, exhaust designer, nor anything along those lines. My good friend is a fabricator and I'm sharing what he's making for my car at based on what I want and feel will work well. All of this is theory and speculation based on info learned from many members here over the years and their findings.**
over 5 years ago I had my good friend build me the exhaust of my dreams at the time. Based on a lack of budget headers were not in the equation at the time. What was absolutely necessary was a merge section (x-pipe if you will) to make it sound like all GT3's should as well as a larger than stock diameter exhaust system. The original exhaust was our interpretation of the FVD race rally exhaust which was the most amazing exhaust i had heard at the time. The video's of that dayglow red 996 rally car are saved on my computer to this day. The result was a full 63mm (2.5") exhaust with merge pipe, custom built mufflers and slash cut 997 GT2 inspired "tips"...not tips actually just slash cut pipes because I didn't want the added weight of tips. Couple pics of the original setup
Fast Forward to current, it's time for a refresh and I'm finally ready to put headers on the car to see if there's any difference. The question became build vs. buy on the headers. Building gave complete freedom in design but in some instances it's much more expensive to build from scratch, sometimes it's not worth the effort to re-invent the wheel where you can take advantage of something produced in bigger quantities and with economies of scale. The build vs. buy decision is really comes down to how much do you want to spend to get exactly what you want. Even with my buddy doing the work at a really reasonable rate for me, the build decision on the headers would have worked out to over $3k. There's a reason the Charles D headers are expensive...it's because they are labor intensive artwork and stainless parts such as merge collectors are much more expensive than you might think. I looked around for pre-made options to see if there were headers that were close enough for the job and while none of them completely fit the bill, here's what I ended up doing.
I purchased the M&M Germany / FVD 996 GT3 sport headers. With the Rennlist discount through FVD they were < $1400 shipped to my door. they are 316 stainless, coated and my biggest concern was how good or bad the collectors on them were going to be. I'm happy to report the collectors aren't quite Burns quality but they are very good. One thing not mentioned in the specs and that was a piece of info hard to get was primary tube length. For those interested the primary length is right around 23". I put all of the parameters I had through the burns design program when looking to build headers and their specs came back with a design for stepped headers with a primaty length of 25.5 ", so these may not be completely ideal but they are pretty close to where I needed them to be. The stepped vs. non-stepped is something I've read about back to my drag racing days....but in going pre-fabbed vs. custom you throw the stepped possibility out the window. Headers can be found here:
What i didn't like about these headers, they choke down to 55mm (54mm per my measure) at the exhaust flange in order to be able to mount to the factory (small) GT3 exhaust system. This is where having a fabricator friend comes in handy. We cut the flanges off of the headers, trimmed them back slightly to the 63mm mark and welded on v-band flanges to have them terminate in the diameter i wanted. Something to note here, this 63mm figure was also a figure that burns mentioned in their design program. For a proper merge collector to function it's supposed to be a slightly smaller diameter than the final exhaust diameter and then transition out to the final exhaust diameter. How much that restriction is is a function of camshaft profile, exhaust pulses and other topics I can only pretend to scratch the surface of. In some instances that restriction is much smaller than the final exhaust diameter, for this engine I went with the burns info and went to 63mm (2.5"). Pictures of the modified headers.
That brings me to where the project stands now. We will use these burns short transition cones after the v-band to transition out to 70mm and construct an exhaust similar to the original in 70mm. I'll post pictures as the rest comes along.
When it's all said and done I will be doing dyno runs as I need to classify the car for NASA Time Trials this year, but unfortunately the dyno runs will not likely be a good apples to apples comparison to the original exhaust. That's partially because I've changed a couple other things since the original dyno of my car but mainly because i changed the ring an pinion which means dyno runs in a different gear than before and with a slightly different gear manipulation for the numbers. None the less I'll report what she does when it's all done.
I clearly haven't learned to use flickr in place of photobucket...I apologize for the double pictures I'll try to fix tomorrow.
**edit** if any of you are as much in awe of some of these great fabricators as I am, my friend also built what may be the only set of 180 degree headers in existence for a C5 Z06 documented here:
His Z06 is sitting in my garage at the moment and sounds closest to a Ferrari 355 if i had to put a finger on it. Really weird to hear that sound coming out of a C5 corvette.
Killer work, looking forward to seeing the results! I'm with you, sometimes it's fun to go a different route, sometimes it can be a royal pain in the ***. In the end once you get it right and make a few pulls to 8K it's all worth it though. (Thanks for the reminder that I've been slacking on making a similar post and dyno run as well )
I'll be very interested in your dyno results. A lot goes into designing an exhaust. Are you chipped?
I'm trying to get Friday off to get to the NNJR event on Friday. Otherwise, I'll go for the weekend.
me too! Just worried they won't be a good comparison to the original based on many factors. I'm most interested to see the torque curve changes over HP. When we built my first exhaust we cleaned up all of the welds on the factory manifolds which leaves a lot to be desired. My car made pretty solid power with the exhaust only on factory tune. I'm also going to be on a dyno in a different shop as the original dyno runs were on a dyno that's no longer in service. What I can be happy about with the original numbers is it made more power back to back vs an '03 cup car so I'll take that.
I do have an RS tuning (Germany) ECUin the car that's a bit of a mystery as far as what it's exactly tuned for but it's in there and seems to run pretty OK. Stock throttle body and plenum though.
I should be at Mid Ohio for NNJR but I have a wild hair to maybe go run the Grassroots Motorsports Ultimate Track Car Challenge at VIR that same weekend. I'll have to see how things play out there.
"I do have an RS tuning (Germany) ECUin the car that's a bit of a mystery as far as what it's exactly tuned for but it's in there and seems to run pretty OK. Stock throttle body and plenum though."
The (standard) RS Tuning /Cargraphic ECU map is designed for a complete Cargraphic/Phoenix R-Sport Exhaust System, the rest is stock
@tom03 - Thanks for the info on that, I've tried to call / contact them a couple of times but with limited success due to language barriers.
Exhaust updates - The hard parts are pretty much done at this point.
Center section / muffler build on the bench as it was progressing, new mounting bracket for center section mounted to engine plate. Slip sections with springs will be used entering the center section to allow for graceful expansion.
Center section finished and mocked in place behind the heat shields, notice that instead of hard mounting with clamps around the mufflers we have moved to cradles for the mufflers with springs to hold them to the cradles again in the interest of allowing everything to expand and contract gracefully.
Just need the connector pipes with primary o2 bungs and tail pipes and it'll be ready for a test drive.
"@tom03 - Thanks for the info on that, I've tried to call / contact them a couple of times but with limited success due to language barriers."
...language is always an issue...
However the R-Sport exhaust is an x-pipe 200 cell HJS cat which looks like your design. Would be interesting if you reach the additional horse power like the Cargraphic/RS-Tuning exhaust.
Picked it up this weekend and then promptly had to leave for a week of work travel this week so i only had about a 20 min drive behind the wheel for any driving impressions. Seeing as though I haven't driven the car since October it sure felt good but I'm not sure I could do a valid before and after from a power level perspective being that it's been so long since i drove it last. Dyno and MPH data from the track will tell that story better.
My old setup sounded pretty darn good, this takes it up a notch. Little deeper off of throttle yet higher pitched up high. Didn't think my car could sound any better than it did before but the equal lengths have changed the tone just enough to make it perfect now.
02-19-2018, 08:47 PM
Exhaust Project v.2
