Would be nice to get some dyno figures before and after this. Just for peace of mind sake.

 

After disliking the cost of various single exhaust options for auto-x use...I decided to cut the OEM catback and add the short turn down.

Modified OEM Catback:

Sectioned the OEM catback with a v-band -


Made a short turn down tip - my brother did the superb TIG welding -




Turn down tip installed -


The new catback weighs in at 9-10 lbs according to my bathroom scale.

I had the opportunity to do a back-to-back dyno session today.

OEM Catback - Peak WHP - 199.5
Modded Catback - Peak WHP - 203.8 (ignoring blip at the end)



The measurements seem to differ quite a bit in the last few data points. I'm not sure if I really believe that the HP spikes like the graph shows, though that is what the dyno recorded... However, there is a distinct 3 HP gain between 7k and 9k and the engine appears to pull a bit harder to redline. None of this is noticeable to the ol' butt dyno, but it is interesting to see how efficient the OEM catback is.

Overall, really pleased with the WHP levels and gains from the easy catback mod. The only other mod I have is a drop in K&N filter (if you call that a mod). The car is an '00 with 70k miles on the clock. The last compression check showed 200 psi across the board, which corrects to 240 psi after altitude is considered.

 

[QUOTE=nmrado,Mar 28 2009, 05:27 PM] After disliking the cost of various single exhaust options for auto-x use...I decided to cut the OEM catback and add the short turn down.

 

Nice work on the back-to-back dyno nmrado! That's a great confirmation of my datalogger testing. I'd ignore the blip at the end of the dyno graph, that looks like some kind of error in the dyno given the extreme difference between the two exhausts.

Random1 - What Ti exhausts are quieter? The Milwaukee and Kansas City NT sound readings put me as one of the quieter cars with any aftermarket exhaust.

 

Do you remember what those sound readings were? I couldn't track down a decibel meter in time for the dyno session, though the SCCA sound level testing can be done anywhere.

 

I was co-driving Corey's (cap'n pants) car during both these events. The actual readings are almost irrelevant because they varied so much from one day to the next due to test location, but we were definitely nowhere NEAR the loudest cars out there. IIRC we were just a bit quieter than the DS ITRs, but with a much nicer tone. And it makes 9k sound like 11.

Just for reference, all the CSP Miatas seemed about twice as loud as us.

 

What ever one the Schillings are running on their 03 meets the less than 93 dB for running at San Diego's Qualcomm Stadium. The other one I was thinking of is the Mugen dual titanium. It too can run at less than 93 dB with silencers in place.

I ran this configuration with a down pipe one time for a day on the street and it was very loud IMO. The whole car vibrated and my passenger complained it was painful. I thought it sounded awesome too, but not practical for non track applications including autocross.

2/7/11 EDIT: I realized this was with the down pipe right after the CAT. I now run the down pipe after the resonator at the Y cut and it is very nice.

 

i'll be subscribing to this thread & coming up with some questions - i'd like to do the exactly same as alot of you guys.

i'm not a big fan of the large exhaust canisters (anymore)

as of right now, this is how my car looks. I still have my whole OEM AP1 Exhaust system in my backyard collecting dust. I'd love to make good use of it.

This is how my rear portion of the car looks like:

having the exhaust exit underneath and getting a fairly less loud exhaust sound would be good

 

so if i got this correctly, this is what you purchased:
piping for the tip (dolphin tip pointing down)
the flange (to connect the tip & the oem exhaust)

and this is what you did to the oem exhaust:
cut after the resonator

am i correct?

 

You want alteast 3 flanges... so you have one to put on the mufflers as well.