Benefits of Removing Cat and Running Straight Pipe?

[Joker]

the less backpressure the better on any engine. scc did a test years ago about all the aftermarket headers for hondas and none of them made any more whp than no header at all. all thru the rpm band, the no-header run made the most horsepower and torque.
(i'll see if i can find the mag somewhere...)

Less backpressure is better, NONE is not...by putting 2 1/2" pipe on any of our normally aspirated cars is overkill in every sense of the word. If you think your car is slow now go ahead and try it.....

To clarify I assume when you say "no header at all" you mean the engine was tested w/its stock exhaust manifold? The only other meaning would be the car had no exhaust manifold at all, esentially running the cylinder head "open" which makes no sense.

A header w/a good design should make some gains on our cars, when I say good design that doesnt mean the 4 into 1 DC header that recently came out. 4 into 1's are for higher (5000+ rpm) applications which means on the lower end your dead...unless of course you drive around at or near redline all day. Do some research, DC's own website highlights this fact!

Just trying to help out the inexperienced. Peace.....

T

[alhope34]

I'll have to agree with Joker on the backpressure thing... Take it away and you'll have absolutely no acceleration from a dead stop at all. An engine NEEDS backpressure to work and run properly. If a 2.5" pipe was better, why wouldn't Toyota use it? A lot of people buy the Honda Fit because of its 3 extra hp. If a larger pipe was really necessary Toyota would have used it. It's because the car needs to have the backpressure there to have decent enough low RPM torque.

[black2yaris]

Originally Posted by Joker

Less backpressure is better, NONE is not...by putting 2 1/2" pipe on any of our normally aspirated cars is overkill in every sense of the word. If you think your car is slow now go ahead and try it.....

To clarify I assume when you say "no header at all" you mean the engine was tested w/its stock exhaust manifold? The only other meaning would be the car had no exhaust manifold at all, esentially running the cylinder head "open" which makes no sense.

A header w/a good design should make some gains on our cars, when I say good design that doesnt mean the 4 into 1 DC header that recently came out. 4 into 1's are for higher (5000+ rpm) applications which means on the lower end your dead...unless of course you drive around at or near redline all day. Do some research, DC's own website highlights this fact! Just trying to help out the inexperienced. Peace.....

: clap:





thanx for clearing that up & saving some people on this thread/YW some cash on useless exh.systems
..can you give us your opinion on what is a good set up for exhaust on our Yarii ....
some here want a fart can with sound ,
some of us want to improve preformance on a Yarii with in reason on a street car,
some want a Yarii they can weekend track with,
then some are just Ricers
.... any advice is welcome Thanx in advance

[largeorangefont]

Originally Posted by black2yaris

: clap:





thanx for clearing that up & saving some people on this thread/YW some cash on useless exh.systems
..can you give us your opinion on what is a good set up for exhaust on our Yarii ....
some here want a fart can with sound ,
some of us want to improve preformance on a Yarii with in reason on a street car,
some want a Yarii they can weekend track with,
then some are just Ricers
.... any advice is welcome Thanx in advance

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

[kurokoma-kun]

Originally Posted by largeorangefont

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

What is your opinion of the one etimago is proposing for GB?
http://www.yarisworld.com/forums/showthread.php?t=9047

[largeorangefont]

Originally Posted by kurokoma-kun

What is your opinion of the one etimago is proposing for GB?
http://www.yarisworld.com/forums/showthread.php?t=9047

There is no info on piping diameter, but the price sounds good :)

[Black Yaris]

Originally Posted by largeorangefont

The best system would be a header back mandrel bent 2 inch system with a straight through muffler such as Magnaflow. You can use a single high flow cat between the 2 02 sensors and probably won't get a CEL.

I agree, but I recommend 2.25... I had the 2 inch at first and noticed a gain, but was not happy with the muffler. so I decieded to say hell with it and go 2.25 mandrel from the cat back with a new res and a flowmaster, and that made a HUGH difference though out the whole RPM range... IF I lost anything in the low end (i doubt I did) it was not felt and the gain out weighted the loss

[joey1320]

Originally Posted by Joker

Less backpressure is better, NONE is not...by putting 2 1/2" pipe on any of our normally aspirated cars is overkill in every sense of the word. If you think your car is slow now go ahead and try it.....

To clarify I assume when you say "no header at all" you mean the engine was tested w/its stock exhaust manifold? The only other meaning would be the car had no exhaust manifold at all, esentially running the cylinder head "open" which makes no sense.

A header w/a good design should make some gains on our cars, when I say good design that doesnt mean the 4 into 1 DC header that recently came out. 4 into 1's are for higher (5000+ rpm) applications which means on the lower end your dead...unless of course you drive around at or near redline all day. Do some research, DC's own website highlights this fact!

Just trying to help out the inexperienced. Peace.....

T

no i meant no header/manifold at all. just open exhaust out of the head.
i'll try to find the mag. around the apartment somewhere but not sure if it will still be around, since its an old mag.

and yes they did make more whp/tq with nothing connected to the head... i'm not a designer/engineer so i'm not sure as to how/why but it did...

[alhope34]

Originally Posted by joey1320

and yes they did make more whp/tq with nothing connected to the head... i'm not a designer/engineer so i'm not sure as to how/why but it did...

Probably more top-end torque? I am absolutely positive there is low end torque lost if there is not enough back pressure.