Would replacing stock cats with test pipes on a supercharged car be a good thing? In that, would there be HP and TQ gains to be had from such a modification?

I have my thoughts, but I have a disagreement with person on the possible benefits of this.

Thanks -

 

Anything is better than the OEM cats, especially if you have a turbo or SC setup. I wouldn't get test pipes though since ALOT of people have said that they are raspy. I have the Kinetix Resonated pipes and they sound great with the Borla.

 

The arguement is that the incresed flow of the testpipes will drop the boost on superchager and result in a loss of HP and torque -

To get more precise, the arguement is:
with the increase of expelled gasses cyclinder pressure will decrease as a result. Supercharger can not maintain the same levels as boost is dependent on rpm so a loss of cyclinder pressure in this case will result in a loss of power until you increase boost pressure to gain back the loss of pressure that resulted in the application of the test pipes

I'm not saying which side I am on yet.

 

Following that logic would mean that the more restrictive the exhaust, the higher the boost and the higher the HP/Tq gains. That can't be true. The idea is to get more air into the engine and out of the engine to make more power. I would ignore the PSI and look at the dyno as my guide.

 

Vortech & ATI = Upgrade to HFC or TP

Stillen & HKS = Leave stock in place or you may end up lean or with less HP.

 

The Vortech is completely tunable with the R4 software and a laptop for simple mods.

 

I was the perfect example of this . I had on headers and RT cats on when I put on the Vortech SC . I only could make 7.2lb's of boost . I got rid of the Rt's and got resonated test pipes...couldnt stand the rasp of the RT's nor the test pipes . I ended up with Crawford cats . Went back to the dyno...I made 9.5lb's of boost but lost HP . I had to retune it a little more aggresively to get back the HP I lost

 

So do you say go with the HF cats or is it even worth it?? Side not just wanted to say thanks to the guys that have been posting alot on these kind of threads! You know who your are!

 

So right now I have resonated test pipes. I am currently buying the parts for my Vortech install. I could really care less about the sound. Cant call it rice if it has almost 400 HP! Anyway, is the general concensus that test pipes will lower boost pressure thus resulting in less HP? As asked earlier, is it a really noticable dfference? Would I be better of to get HF cats?

Zach

 

Ok, losing boost is not a big deal. More flow means more power. Lower boost level for the same amount of compressor speed is good because it means you aren't wasting as much HP pumping around exhaust. (This assumes you aren't leaking boost in the compressor or intake.)

While more boost is generally a good thing, better boost is what you want.

 

read post #19 and #21.

https://my350z.com/forum/showthread....ortech+pulleys

Less boost and the same rwhp.....

 

Correct me if Im wrong but doesnt this mean that if I can produce the same RWHP with say 7.5 psi as I did with 9.5 psi, then I am more efficiently using the boost or something like that?

 

For the people that are worried about the raspy sound,

I'm not 100% sure if its the same for S/C's (i'm pretty sure it is the same), but on TT's the raspy sound gets eliminated by the extra airflow going through due to the boost. With my TT I can't even hear the test pipes anymore. I had them on before the TT, so I know what kind of sound they made. I have heard that on a F/I kit you can even go with non-resonated test pipes (which are even raspier than resonated one's), and you will not hear a thing. Even most exhausts become quieter after you install a TT kit (once again, I think its the same for a S/C as well), due to the more freerer airflow so it gets through the exhaust quicker.

On to Zivman's question, I believe that either replacing your stock cats with HF cats or Test Pipes will increase HP. You want the car to be able to breathe easier by letting more air pass through faster. So a less restrictive system would be more effective than the stock cats, because power is ussually gained by increased mass airflow.

 

I lost a lot of rasp after my s/c install....sounds a lot nicer now.

 

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This is exactly what I was thinking from the begining, but the other fellow wouldn't/couldn't see this. The car may loose boost pressure as a result of opening up the exhaust, but this doesn't translate into a loss of power. Only the reading on the boost gauge

 

Ok. Running 7.5 psi and getting the same amount of RWHP as a person running 9.5 psi would be much more efficient, and would be better for the
SC. Reason being that it is not running as hard/hot as it would be with 9.5psi. Thus adding to the longevity of you SC system, and probably your engine.

Therefore adding test pipe would be a good thing, because you are opening up the exhaust system allowing the car to pump out the exhaust more freely as Zivman said above I believe.


Correct me if I'm wrong please.

 

Thats exactly right. If you produce the same rwhp at a lower boost, that means that your engine is running more efficiently. By running more boost, you make your SC work harder, and in return straining it more, which can decrease its longetivity (sounds logical). So you want to produce the most power at the lowest boost possible.

Up to date, I have never heard of anybody loosing HP after adding cats or test pipes. I highly suggest that you add breathing mods (ie. exhaust, test pipes, cats, headers, plenum, etc) to any F/I and N/A car (headers don't fit on a TT). Breather mods are what opens up your power range and removes most of the restrictions. One breahter mod might not make much of a difference, but you will definantly feel the difference when you combine a few of them.