Cat Replacement pipes.

[NSX2NV]

Has anyone with a 97+ NSX replaced the cats with straight pipes? I have the hi boost CTSC with Taitec GT lightweight ans Taitec Headers on my car. I wanted to get a few extra hp by removing the cats. I spoke to a few people and have been told that approx 15-20rwhp can be gained but it may trigger a CEL. Also they informed me that the AEM is out for OBDII Nsx's and with the EMS the CEL problem can be resolved.

Any suggestions if this is a good idea to gain some more power and what replacement pipes are available. Taitec only offers 91-94 pipes and Comptech no longer has them on their site.

Thanks

 

[Devin@AEM]

Test pipes will throw a CEL unless you use an O2 simulator. Several companies make them.

AEM does not have an OBDII NSX EMS application.

 

[ktan]

approx 15-20rwhp can be gained but it may trigger a CEL.

Thanks

I really don't think it will even come close to that number, do a search on prime for test pipes for more accurate opinions.

I don't run cats on my car just because of my inter/after cooler situation, my O2's are hung in the atmosphere and I do not get a CEL. My car is a 95 OBD II

 

[NSX2NV]

I just finished the search. The average gain I see is 13 hp with the by pass pipes. I also managed to find 97+ high flow cats, althought the gain is only 5-7 whp this seems to be a better route due to emissions.

Thanks for the help guys.

 

[gobble]

I have a low boost CTSC and ran a dyno before and after installing test pipes. The only reason I installed them was to get more accurate air/fuel readings.

I gained zero horsepower and lost a bit of torque. If you search through my posts from the last several weeks, you can find before and after dyno's. The car was very loud, embarassingly loud, on the street when combined with header and exhaust. I took them out the day after the dyno test.

 

[Jasil]

From what I've read test pipes will give a gain on a otherwise stock exhaust, but on a header/cat-back exhaust you will not see negligible gains. Don't forget that HP doesn't add up. ex. 10hp air filter, 15hp header, 10hp test pipe, 10 hp cat back......if that were the case you could have a 335 crank HP NSX pretty easy.

 

[TitaniumVtec]

I had my cats off for a few weeks as I wanted to hear how the headers/muffler would sound with not restrictions. It added so much volume to the exhaust that I loved it!! However, the back of my car would turn black after 10 minutes of driving. Then after a week or two, the paint turned yellow. I had to wax/compound the yellow crap off the back of my car. I decided that the cool sound was not worth the extra work Also, w/o the cats, the exhaust on my car was toxic. I could not let my car idle in the garage without stinking up the whole damn house! Besides, a few extra HP is not worth the extra emissions you'll be producing (damn, I can't believe I said that!).

 

[john@johnhudakracing]

Has anyone with a 97+ NSX replaced the cats with straight pipes?

Sure.

I have the hi boost CTSC with Taitec GT lightweight ans Taitec Headers on my car. I wanted to get a few extra hp by removing the cats.

Ok.

I spoke to a few people and have been told that approx 15-20rwhp can be gained but it may trigger a CEL.

Hah hah, 97+ NSX test pipes of everflowing +20.. yeah I think I want a set of those too! I guess there must be a problem with my CT's. Although I haven't conducted a dedicated dyno test as I prefer to just leave the test pipes or cats attached to each exhaust for install simplication when doing swaps... so far as real world gains that sounds high.

On the CEL, so long as your replacement set has provisions for the OE 02 sensors practically everything should be fine. The down stream 02 sensor will inevitably get fouled, and all it's looking for really is that the down stream 02 sensor is showing less than the upstream 02 sensor. If it is really a concern then there are electrical options as Devin mentioned.

In practice, my own experience at the track is that I don't ever even recall so much as a check engine light firing with the updated replacement ECU, but obviously each specific instance may differ as peripheral factors can influence emissions as well- like hi-boost superchargers and fuel management. :biggrin:

Also they informed me that the AEM is out for OBDII Nsx's and with the EMS the CEL problem can be resolved.

As Devin mentioned there is no ODBII NSX EMS application. There are more limited EMS solutions for the ODBII application.

Any suggestions if this is a good idea to gain some more power and what replacement pipes are available. Taitec only offers 91-94 pipes and Comptech no longer has them on their site.

IMO absolutely a good idea and it sounds/smells a little better too. In the absence of an off the shelf solution I would suggest to just go to a reputable local race/muffler shop and have a set made from stainless or mild steel depending on how much you want to spend. As I recall your lightweight uses 60mm piping. It wouldn't be very expensive and it's not that hard. You can always swap exhaust components around at your whim it's not that difficult and it takes just a few minutes and extends to you as the user the most options.