The effectiveness of test (straight) pipe on a NSX!

[VietNamNSX]

This topic had been discussed a few times before, but this time, instead of speaking based on what you might have heard, think, etc - I think it would be much more educational if people who have some hard facts can comment on this. Note that I have not done a dyno hp test on this so I donot have much info on what is gained or lost. The questions are:

- Does the NSX actually lost some low-end torque with the test pipe? Does it gain any high-end hp? (Taking it in and out and i could have swear that the car pulled just a little bit harder down-low with the cat back on.)
- If any hp gained up in the high-RPM range - How much and at what RPM? For example: On the freeway, downshifhting to third at 75mph, or from a drag-race, would the NSX benefit from the effect of more torque or more hp? (With everything I have done to it, this car can go but i can't gauge the differences in acceleration between the effects of the cat or the test pipe.)

At the end, if the cat is back on permanently, can I remove the cat cover, holding together by 6 bolts on each side, to save some weigh? And what is inside the cat?

 

[PhiAlpha44]

I think the power gains (or losses) in this area is pretty insignificant. I have test pipes, but I added them when I added my headers. So it obviously felt more powerful the next time I drove it. But what's better than that is the SOUND! The car sounds SO GREAT with headers, test pipes and after market exhaust. Personally, if there was a 2-3 horsepower gain by going to test pipes, then yippee. If there was a 2-3 hp loss, the hell with it, I'd still do it because it sounds so great. But who knows, I could be completly wrong. Maybe somebody can show dyno numbers of 10 hp gains and losses depending on the set up. Personally, I feel there is more torque down low. But that's just my butt in the seat, not electronics hooked to the car.

 

[TURBO2GO]

It really depends on the rest of the setup... someone here did an actual dyno, I believe it was a 3 HP difference and I believe he already had a header and aftermarket exhaust. Its probably less than that stock. More if you have a supercharger. That cat cover weighs nothing... don't bother.

 

[nsxtasy]

It also makes your car stink.

 

[ryan1926]

It really depends on the rest of the setup... someone here did an actual dyno, I believe it was a 3 HP difference and I believe he already had a header and aftermarket exhaust. Its probably less than that stock. More if you have a supercharger. That cat cover weighs nothing... don't bother.

My car was dyno'd with the straight pipes on and off and we only saw a 3hp gain with the straight pipes on with the mods in my signature line.

 

[nimdivino]

What makes sense to me is this.

I remove the cat and keep it for smog purposes, it doesn't matter if I was running headers and exhaust or not. Cats are just too expensive for the NSX, so I'd rather save them especially when I'm running headers. From my past experience, headers tend to burn-up cats. Testpipes will definitely benefit from headers and exhaust, but I highly doubt it on stock headers. There will be more torque with cats on, but will benefit on high-end with test-pipes and sounds good.

niM

 

[BATMANs]

How long do cats on NSX's typically last under normal usage?

replacement costs?

For the pre-95 NSX can't u use aftermarket cats?

 

[nimdivino]

Cats should last a loooong time, someone said forever but that's only when you're engine is running in tip-top shape. If you installed a brand new cats, but engine is running really rich, the cat won't last 3 mos coz extra gases will just eat the cat.

Aftermarket headers does free up a lot of exhaust gases hence why we benefit with higher HP, but in turn giving more stress to the cat and will wear it out faster.

OEM cat from dali racing (better pricing than dealership) = $800+
Save your cats now, buy test pipes = ~$200

You may get better performance, you may not depending on your setup BUT you'll definitely not loose HP either. Then you just save about $800+ in the long run, and you get a good sounding exhaust.

Dali racing sells 95+ aftermarket cats.

nIM

 

[Ponyboy]

"Effectiveness" depends on what you want the test pipes to do. The benefits are increased hp (though not much by anyone's standard), auditory performance (subjective), and lighter weight (significant). But they do make the car smell (not so bad), they are LOUD, and they're not emissions compliant. So Al Gore will run you over in his 7 liter Suburban if he finds out you're running them.

FWIW, lots of companies sell aftermarket test pipes for the NSX, not just Dali (whom has a less than stellar reputation).

 

[VietNamNSX]

So, say these are the attributes of the test pipe on a NA NSX, (plus the possibility that the pipe can take away some torque because of a lack of back-pressure), what about the question of drag racing or downshifting to 3rd at 75mph? Would a NSX perform better at these conditions with the cat because it has more torque down-low, or it wouldn't really make a diffrence?

 

[TURBO2GO]

So, say these are the attributes of the test pipe on a NA NSX, (plus the possibility that the pipe can take away some torque because of a lack of back-pressure), what about the question of drag racing or downshifting to 3rd at 75mph? Would a NSX perform better at these conditions with the cat because it has more torque down-low, or it wouldn't really make a diffrence?

at 75MPH, it probably won't make a hill of beans difference. You need to do something a lot more significant to get something noticeable in a situation you are describing.

 

[BATMANs]

Ideally any engine needs to gain maximum port velocities for both in and out.

Too big of a port and at low RPMs air moves slower, but gains velocities at higher RPMs. Too small of a port and at low RPMs air moves fast, but chokes towards the higher RPMs.

 

[BD]

So, say these are the attributes of the test pipe on a NA NSX, (plus the possibility that the pipe can take away some torque because of a lack of back-pressure), what about the question of drag racing or downshifting to 3rd at 75mph? Would a NSX perform better at these conditions with the cat because it has more torque down-low, or it wouldn't really make a diffrence?

With my NA2 NSX. I have test pipes.

when viewing the dyno chart, below VTEC, the power and torque arrives about 200 RPM later than when I had the cats on. However, after VTEC point, I gain more HP and the power curve became more aggresive.

So for every day driving, probably not going to make any difference. I certainly did feel it. However, when I'm on the freeway and downshift to the VTEC sweep spot, the RPM climb much faster.

All that said, I also have one of the best header out there for NSX;it is has a rather large bore size when compare to USDM headers (DC sports, Comptech, and even Taitec), that may have contributed to additional VTEC power surge.

 

[SilverStone05]

you guys with the NA2 2002+ cars, where are you sourcing your test pipes from? i tried in vain to find some and came up empty handed. no one near me will even make a set for me for fear i'm some type of fed. :tongue:

 

[BD]

you guys with the NA2 2002+ cars, where are you sourcing your test pipes from? i tried in vain to find some and came up empty handed. no one near me will even make a set for me for fear i'm some type of fed. :tongue:

I took it to a muffler shop and they made a set for me for $150 bucks!!! They even used a maching to expend the piping to match my header.

 

[Diablo360]

you guys with the NA2 2002+ cars, where are you sourcing your test pipes from? i tried in vain to find some and came up empty handed. no one near me will even make a set for me for fear i'm some type of fed. :tongue:

Dali doesn't have them? Email Mark and ask.......


As for the effectiveness of test pipes: they sprinkle magic dust into the air, remove about 20lb's of weight and make my JGTC sound badass, what more is there to know :biggrin:

 

[TURBO2GO]

you guys with the NA2 2002+ cars, where are you sourcing your test pipes from? i tried in vain to find some and came up empty handed. no one near me will even make a set for me for fear i'm some type of fed. :tongue:

I had to switch over completely to NA1, Vance has NA1 header and NA2 muffler, he had no choice but to use a custom bypass pipe to mate these two together. I am not sure he could run cats even if he wanted to, I don't know.

I was in the same boat as he where I bought an NA2 exhaust and then an NA1 header, but I was lucky enough to be able to have my exhaust refabricated in time. I know GT-Rom does have NA2 bypass pipes if you need them. But I think the decision to remove them for HP gains is questionable. I do think there is some torque loss on the bottom end. And we have a documented gain at the top end of only 3 HP *WITH* a supercharged engine. Its probably a 1-2 HP gain up top and a loss of 3-4 pounds of torque down low.

 

[SilverStone05]

Dali doesn't have them? Email Mark and ask.......


As for the effectiveness of test pipes: they sprinkle magic dust into the air, remove about 20lb's of weight and make my JGTC sound badass, what more is there to know :biggrin:

I emailed Mark and he wasn't sure if they would fit. I'm not going to take the chance.

 

[TURBO2GO]

I emailed Mark and he wasn't sure if they would fit. I'm not going to take the chance.

Try GT-Rom.

 

[nsxtacey]

I think there are test pipes that fit na1, na2 non lev, na2 lev. I have na2 non lev which are just straight pipes theres no bend in it like na2 lev test pipes.

I have a dyno with cats and will do a dyno after the pipes are installed.

One thing I am concerned about is that in my area there are spot inspections where the cops just pull a bunch cars over. Last thing I want is my car impounded cuz theres no cats. Cops can also pull you over for noise volation which is subjective but if they see you have no cats they can just impound your car too. Never happened to anyone I know but I'm sure its happend before to someone.