question on exhaust for a v8 engine

[Cabear]

Would this be a practical alternative for the gs400 v8 engine?

Looking for different ways to go for less torque lossa nd more gains up top, any suggestions on changing the set up, maybe add to it?

 

[JBrady]

I would not recommend this system as it would dramatically loose torque and possibly not even make more top end power.

Do a search under my name as I have written quite a bit about this.

Recommendation is 2.25" duals with a "long X pipe" (like the stock system using two Y pipes connected by a single center pipe). I have not yet tested the 2.50" vs a 2.75" vs a 3.00" center pipe so it is not clear which will make the best torque/power curve but the Y pipes design and build is important and I would suggest a merge angle of 15 degrees.

As a side note: I just picked up the latest issue of Engine Masters and they have a twin turbo Pontiac 482 CID engine that makes... GET THIS... 2886hp and and the could not record peak torque as it was OVERPOWERING the dyno!!! The most they could record was 2100 lbs/ft at 7200rpm.

Why do I mention the above? This massive engine (nearly twice the 1UZFE displacement and almost 10 TIMES the power output uses 2 inch primary pipes and 2.50" collectors in the turbo headers. Each 2.50" collector is supporting over 1400hp. I promise you do NOT need dual 2.75" pipes in your car.

 

[Cabear]

huh, interesting read. I'd figured with the bigger displacement more pipe would allow for more flow and hp up top. From what i've been told on other forums, going to a dual-to-single setup wouldnt cost me any hp downlow because of the Y pipe and as along as the pipes were sized i could make some power up top as well. very interesting.

 

[chimpy]

So do you not reccomend just running two straight pipes? like where the x pipe would be, just have two parallel pipes, keeping each bank seperate in exhaust?

 

[JBrady]

So do you not reccomend just running two straight pipes? like where the x pipe would be, just have two parallel pipes, keeping each bank seperate in exhaust?

The only reason you would want to run separate dual pipes is to obtain a certain V8 rumble exhaust note. Otherwise, you loose performance. The truth is that exhaust flow is enhanced and therefore power increased when you utililze a PROPER merge section (X or Y pipe, H pipe is a third but lesser choice).

 

[chimpy]

I am just importing an LS400 right now from Japan, and it says that it comes with a catback exhaust. In standard form (1989 LS400) are the cats located just after the dumps? Meaning, if i wanted to put on extractors, i would need to do a little custom work on the cats to fit them down just before the X pipe.

Also, do you beleive a "long x pipe" would be better then a "short x pipe". meaning, over the length of the y+pipe+y to make one really long x, compared to just a quick x before the exhausts split again...

hope i made sense

 

[Pro]

the reason for joining the two pipes by either a bridge or an x pipe is to equalise the pressure differences yeah?

 

[JBrady]

I am just importing an LS400 right now from Japan, and it says that it comes with a catback exhaust. In standard form (1989 LS400) are the cats located just after the dumps? Meaning, if i wanted to put on extractors, i would need to do a little custom work on the cats to fit them down just before the X pipe.

Also, do you beleive a "long x pipe" would be better then a "short x pipe". meaning, over the length of the y+pipe+y to make one really long x, compared to just a quick x before the exhausts split again...

hope i made sense

The cats bolt to the exhaust manifolds. Extractors/headers would require relocating the cats in some fashion. Check out www.planetsoarer.com for good pictures.

I personally like the long X style. It allows different center pipe diameters to be tried as well as a resonator for reduced noise.

 

[JBrady]

the reason for joining the two pipes by either a bridge or an x pipe is to equalise the pressure differences yeah?

Sorry but no on the X or Y. They channel the velocities into one mass stream and that creates a one way flow. They also acoustically change the sound wave shape which enhances power and is what an H pipe does.

 

[Pro]

ah okay cool.

thanks

 

[lspower]

x pipe is still okay right? i had straight dual 2.25 exhaust breathing ok but i felt a LOSS! in power so i added an x pipe then got it back

 

[JBrady]

x pipe is still okay right? i had straight dual 2.25 exhaust breathing ok but i felt a LOSS! in power so i added an x pipe then got it back

Seems strange doesn't it? That dual pipes do not perform as well as an X, Y or H pipe. Did the X improve the entire power range or low/mid only? Are you running cats? Have you posted pictures?

To your question, yes an X pipe is fine.