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The one I did has a full 3" path through it on each side, so I do not think its restrictive. Hard to tell if the one from alleykat is restrictive, depends on how they cut the pipes. It's also not on a 993TT. I think the one that Basal did actually is a bit larger and probably mixes more. Knight's is even larger given its really two 4" pipes facing each other. Mine is below.
The one I did has a full 3" path through it on each side, so I do not think its restrictive. Hard to tell if the one from alleykat is restrictive, depends on how they cut the pipes. It's also not on a 993TT. I think the one that Basal did actually is a bit larger and probably mixes more. Knight's is even larger given its really two 4" pipes facing each other. Mine is below.
Cheers,
Mike
When you first posted yours, I could tell it was large enough to flow well. That's my apprehension about anything on the market. Don't think it's effective, or has enough area to reap any rewards.
Interesting design, thanks for the picture! Are those mufflers or cats in line after the X pipe? Why did you put the bypasses in, you looking for more sound?
Any other pictures? :-)
I dont have many other pics since im still perfecting it.The pic below was before adding the vertical passes which yes did change the sound.I did it before on a Lambo so I tried it on my car.It's a lot of trial and error of course.There is no cats on this at all,those cans are resonators from Vibrant.I have adjustable 02 restrictors on all 4 sensors.
Excuse the rushed thru welding,since its a tester I didn't take my time.Also didn't bother brushing the tubing before welding.I'll do that on my final final version.
Originally Posted by Basal Skull
Yes that is interesting with the bypasses. With no adjustable joints, that's pretty tough making things to fit the flanges exactly, l had difficulty just welding one joint d/t stainless expanding with the welds!
Stainless does pull way more easily than mild steel.We had a good bit amount of fixturing going on with this setup.If you look at any of the 997 non TT setups none look like this.All the others go back into the bumper sides then back down.I wanted mine super compact and aggressive looking.You can see the resonators a little bit peeking from back of the car.
Originally Posted by OverBoosted28
The smaller area of the X-pipe, just seems as though each bank would fight the other, to get through. Like the larger chamber for the mix.
It flows pretty well actually.One way to tell if one side wasn't getting flow,it simply wouldn't be the same color.
.I have adjustable 02 restrictors on all 4 sensors.
Excuse the rushed thru welding,since its a tester I didn't take my time.Also didn't bother brushing the tubing before welding.I'll do that on my final final version.
I used the adjustable O2 sensor bungs too.
What are you talking about 'rushed' those welds look really nice, you must do this professionally (or could if you don't)!
Post 2 has a sound clip but its far from the best quality.Just a cell phone clip from the passenger seat. I will get a real video once im happy with everything and finish adding the tips.
I built a 3" with custom muffler/ resonators a while back. I'm currently researching methods to get rid of the drone at 2000-3000 rpms.Mostly 2400 rpms Can anyone chime in on the drone level with the different exhaust setups.
I can add a helmholtz tube or add tubing length after the muffler before the tip. Maybe a u turn in the old muffler location.
I plan on measuring cabin noise before and after.
does anyone have cabin noise readings?
I built a 3" with custom muffler/ resonators a while back. I'm currently researching methods to get rid of the drone at 2000-3000 rpms.Mostly 2400 rpms Can anyone chime in on the drone level with the different exhaust setups.
I can add a helmholtz tube or add tubing length after the muffler before the tip. Maybe a u turn in the old muffler location.
I plan on measuring cabin noise before and after.
does anyone have cabin noise readings?
I got these for a good price and am pretty happy with them. They do drone pretty bad at about 2000-2500 rpm. I usually never stay in that rpm, so it's not too much of a pain. They're pretty much a "U" shape, so not sure if that'd cancel any drone. Might create more.
I built a 3" with custom muffler/ resonators a while back...
I can add a helmholtz tube or add tubing length after the muffler before the tip. Maybe a u turn in the old muffler location. ..
does anyone have cabin noise readings?
helmholtz tube sounds interesting, maybe where the old muffler was, just before the tips? - would seem to be the easiest thing to try. Could vary the length or amount of packing to see how it changes the sound.
I could take some cabin noise readings, I probably have drone although I guess it's little bit of a perception thing (not quite sure what it is) and might be different depending on who is listening. It doesn't bother me. Capping off one of the twin tips like I did probably is a helmoholtz tube type of thing, it seemed to change the sound at lower rpm but I did't think it changed much at higher rpms (but that was before I added the inserts - haven't really had a chance to take it out since I put the inserts in).
Another option might be to make a tube that connects the two sides - like an H type (vs X over) where your exhaust crosses over which might change the sound too (although there may not be any space for that actually).
Here's a pic of your car from your thread:
I should have time this month to experiment with different methods to get rid of the drone. First I'll try the helmholtz tube in the area of the stock muffler location. I'm using a phone app to measure frequency and decibels
I don't want to tie the two sides together at this point.
Was out at the track April 1 and had a chance to try it out on the track (and the 3 hour drive there and back). Car ran great, exhaust looks good after inspection with no loose or broken parts (was a little anxious about that). No check engine light with the O2 sensor spacers (for the distal sensor). Took it easy on the track for the first 1/2 of the day, then second half was driving a little faster. Sounded good, and afaik wasn't too loud (could hear the 991 gt3 in front of me and it shifting easily - that thing shifts so quick, it would shift through 3 gears while I'm rolling on the gas in one gear, I try to shift as little as possible while the pdk cars seem to want to shift as often as possible, very different approach to driving). No problems on the drive to and back, louder than my old exhaust (umw sport cats/roock mufflers) but not bad. Sounded great in the tunnel!
11-30-2015, 03:42 PM
Gonna try and make it a weekly thing again.
