Hmmm very interesting stuff....

Hadnt Eric found a setup that was used by a Honda team (hart racing, i think?) in the Mid-west very similar to this? He had a thread about it a while ago seeing who was interested

I love the idea, but I am with everybody else. If you've got exhaust, and j-pipe.. you will probably loose power, or not gain much at all.. The addition of a S/C with all these goodies, can easily mean 350whp for a TL-S (most likely a 6MT, but hey, ya never know!)

If Actros was able to accomplish 320whp on a 5AT TL, withOUT using a HBP and just a j-pipe (eshit), ct exhaust and im not sure if he had pro-cats or not....

 

I am getting this as a fall back in case shit... cuz the procats last wat 2 years max

 

How does anyone think we're going to lose power from going catless? Not going to happen.

 

^ lack of back pressure.. its quite possible

 

Even so, you're always going to pick up hp and midrange torque. Low end torque is the only thing to worry about but I'm betting that with the stock exhaust piping and mufflers there's going to be plenty of backpressure.

 

oh yea.. with a stock exhaust, the back pressure probably wont be an issue... but some of us who have ATLP exhaust/j pipe and a CAI are worried that too much air flow = loss of back pressure... i guess only the dyno will tell

 

This is what I've heard and read somewhere before... dont flame me pls

I thought it's not the backpressure that makes you lose tq down low; it's because removing the pre cats changes the resonant frequency of the exhaust. Kinda like short intake runners are good for High RPM power and long intake runners are good for down low tq.

Anyone else heard this before?

 

^ hmm interesting concept

 

The resonant frequency you speak of is called scavenging. Not really applicable in our cars because the exhaust merges into one inside of the heads.

With too little backpressure you can overscavenge the cylinders during valve overlap but it depends on a lot of things and especially cam size. We may or may not lose low end with no cats. I have a feeling we won't since the primary cam isn't that aggressive.

 

You got me interested in this and I did a little reading and found this on wikipedia:

"Great care must be used when selecting the length and diameter of the primary tubes. Tubes that are too large will cause the exhaust gas to expand and slow down, decreasing the scavenging effect. Tubes that are too small will require additional force to expel the exhaust gas from the chamber, causing unneeded labor on the engine and ultimately a loss of horsepower. This is true for all parts of the exhaust system. In competitive environments it's often required to select the header based on the specific application of the engine. Since engines produce more exhaust gas at higher RPMs the header will respond differently across the RPM range. Typically, large primary tubes offer the best gains in horsepower and torque at higher RPMs, while smaller tubes offer the best gains at lower RPMs. Many people who put race headers on their vehicle experience a noticeable low-end torque loss. This is a result of insufficient exhaust gas output at lower RPMs. The exhaust expands once it enters the primary tube and slows down, reducing the scavenging effect. Many automotive mechanics and enthusiasts erroneously conclude the loss in torque was due to a lack of back pressure. Despite the low-end torque loss, at higher RPMs the engine will produce more horsepower and in race situations, the vehicle should be faster.

Some headers are also resonance tuned, to create a low-pressure reflected wave rarefaction pulse which helps scavenging during valve overlap. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. By tuning the length of the primary tubes additional scavenging can be achieved if the pulse is generated at the exact moment valve overlap occurs.

Some modern exhaust headers are available with a ceramic coating. This coating serves to prohibit rust and to reduce the amount of heat radiated into the engine bay. The heat reduction will help prevent intake manifold heat soak, which will decrease the temperature of the air entering the engine."

 

=) SC guys like me? LOL

well one thing is for sure... we are running on a V6 already... so the torque vs back pressure is somewat different... i mean... we should look at the Team Acura TL to see if they had cats on or not... coz pulling out a corner u need torque.. and itz not like they will be running at max speed.. so hp is somewat not a useful number for their purpose.. =)

 

you will never lose power going catless. you will nevernevernevernever. the powerband will shift to different rpm range. i don't need low end torque. if i'm gonna haul ass, its gonna be 100mph+ on the freeway. i want my power to be at where i need it. 3.5-5k and up. back pressure is not a necessity as many may think. exhaust systems don't add power. it frees restricted power.

 

I am one that does not believe the backpressure myth...

everyone on this site who talks about loss of back pressure mentions this e-shift performance test with procats and a custom jpipe... how reliable is that... it is HEARSAY

 

more air more power right??? so why not