Exhaust Layout and Flex Pipe

[RJ138]

I have a 4 inch downpipe that I want to connect to a 4 inch cutout pipe and then reduce down to 3 inch with a flex pipe directly after. The flex pipe will then connect up to a FWD Performance 3 inch exhaust system. I'm a little concerned about having the flex pipe so far down into the system, it will be almost in the middle of the car. The car has a Polybushing solid front and passenger motor mount and a home filled trans mount so that should reduce engine movement significantly so maybe the flex pipe won't matter as much. Any thoughts?

[Mopar318]

If you are using the donut gasket with the spring bolts you really dont need a flex pipe.

[Ondonti]

Why do you think he has a standard donut on a 4" downpipe?

[GLHNSLHT2]

lol :)

[RJ138]

If you are using the donut gasket with the spring bolts you really dont need a flex pipe.

I'm using a v-band connection.

[Mopar318]

People, including me have ran 3" donuts on stock housings. Sometimes people go to larger downpipes after the flange, so you never know.

I ran a V-band connection too, with no flex pipe. This was on a setup with a side exit exhaust, and semi solid rear bobble. I never had any problems. The further down the flex pipe, the more lever action you will get. It should be fine putting it where you need too, I have seen plenty of setups like that.

[RJ138]

People, including me have ran 3" donuts on stock housings. Sometimes people go to larger downpipes after the flange, so you never know.

I ran a V-band connection too, with no flex pipe. This was on a setup with a side exit exhaust, and semi solid rear bobble. I never had any problems. The further down the flex pipe, the more lever action you will get. It should be fine putting it where you need too, I have seen plenty of setups like that.

It looked goofy to me when I laid the system out, so figured I would ask. I will proceed as planned. Now to chop up my dump tube to get it to mate up with the rest of the system is going to be fun.:yuck:

[turbovanman²]

You should have it as close as possible to the front. I had the same issue, no room, but managed to put my dump right after the flex pipe.

[Ondonti]

I have read from a Japanese Skyline builder that he goes much larger on the flex tube then the actual exhaust. I can't remember if he was using 4" flex on 3.5" exhaust or 4.5" flex. He said this was very important. This was something that was translated and on a Skyline blog, professional shop, not a hobbyist.

[Polygon]

Interesting.

I would kinda' like to hear why. Not because I think they're wrong, just curious.

[RJ138]

Well if anyone knows of a reasonably priced 4" flex pipe that is around 4" long I could add it into my downpipe. I have only seen ones that are 8" and 10", and these are only the lengths of the flex material.

I may just ditch the dump all together, 4" is a little excessive but would be pretty cool.:cool: