What is the deal with Off Road Y's? I have a mufflex on my one car that has two 3 inch into a flowmaster 3 1/2 inch collector followd by 3inch pipe vs the Jet Hot ORY that is on another car of mine with two 3 inch into a 3 inch pipe.

On both ORY's that seems like a large bottleneck when you are bringing 6 inches of pipe to basically 3 right there.

On a 330-350rwhp car is it enough of a bottleneck to try to get a 4inch collector with several feet of 4inch pipe afterwards?

 

What!?

You lost me..... I never thought of the 'bottleneck' theroy. I think a 4 inch collector would be a bit much on an otherwise stock engine. You need some back pressure.

Some PPL just don't like, or don't feel like dealing w/ cats and emmisions equipment so they do away w/ the cats, EGR and AIR sys's...

 

Bayer I know why people use ORY's. That wasn't my question.

You have two 3 inch pipes running into a single 3 inch pipe. To me that sounds like a bottleneck. 6in. to 3in.

 

First of all you don't want back pressure in the exhaust system. You want it to be able to scavange the exhaust which helps the intake process. People are getting back pressure confused with "tuned" length. You have two 3" pipes into the Flowmaster 3x 3.5" Y. You must be necking down the pipe after the Y from 3.5" to 3".

With the horsepower you are talking about I would go with a 3.5" system from the Y on back. Yes the 3" pipe is a bottle neck to answer your question.

A 4" collector is to large for your set up. The collector should be 1.75 times the header pipe size. If you have a 1 3/4" header that works out to just a tad over 3". So you are fine on the collector size. Also the secondary pipes.

 

Thanks. That is a great answer!