Where to bring the 1-3 and 4-6 pipes together.

[Jim Kueneman]

Here is a simulation comparison of how changing the length of where Dutra Duals are recombined. I (and Doug Dutra) always say the further back the better. This is an Oregon Cams 819 ground on a 106 LCA with 9.4:1 compression build I just got back from the machine shop. Compares the joining “Y” for the Dutras at 18”, 32” and 60”. Like I always preach for daily driving it is well worth it for low end torque.

Note: Doug Dutra has proven it with seat of the pants testing. He put the Y back buy the rear axle on a build and said he it was a noticeable difference in low end torque when he was creating the Dutra Duals back in the day.

My Dart is about 45” back and @RustyRatRod also just did this and found noticeable torque.

 

[halfafish]

Very interesting. Would this longer-is-better business apply to Clifford shorty's also?

 

[Jim Kueneman]

Very interesting. Would this longer-is-better business apply to Clifford shorty's also?

Yup, that is what @RustyRatRod is using.

 

[Jim Kueneman]

Very interesting. Would this longer-is-better business apply to Clifford shorty's also?

And longer is better for _low_end_torque_..... notice it rolls off sooner for higher RPM.

 

[halfafish]

And longer is better for _low_end_torque_..... notice it rolls off sooner for higher RPM.

That's what I'm looking for. I figure this car will never see north of about 4500 RPM so I'm shooting for idle to about 4K for the operating range.

 

[RustyRatRod]

Longer is better for lots of things.

 

[Jim Kueneman]

Longer is better for lots of things.

These days in simulation only....

 

[halfafish]

Longer is better for lots of things.

I knew that was coming. I'm only surprised it took this long to show up.

 

[RustyRatRod]

I knew that was coming. I'm only surprised it took this long to show up.

SO I'm slippin.

 

[Rug_Trucker]

I was thinking an H pipe as close to the collectors was a V8 thing. Thought the same for the 6.

I have full length duals on my Duster with an H. Now is the X more trendy?

 

[Jim Kueneman]

I was thinking an H pipe as close to the collectors was a V8 thing. Thought the same for the 6.

I have full length duals on my Duster with an H. Now is the X more trendy?

The crossover goes where it needs to go to make the curve do what you want it to do. There is no correct one spot. The X may have some small advantage and it makes the tone different. Most new cars are X and that is one reason for the sound modern performance cars make.

 

[RustyRatRod]

I was thinking an H pipe as close to the collectors was a V8 thing. Thought the same for the 6.

I have full length duals on my Duster with an H. Now is the X more trendy?

It's not a cross over in the dual exhaust sense. It's a wye. Where two pipes come together.

 

[Killer6]

And longer is better for _low_end_torque_..... notice it rolls off sooner for higher RPM.

Yeah, for that combo, the best curve there is actually the 32" Y,.....by a bit.

 

[chryslercruiser]

What I want is the low end of the pink, that carries like the white line!!

How to get there? More exhaust work, or switch to a different intake manifold?

Does increasing the primer exhaust pipe size, before the collector do anything to get the pink torque line to carry farther up the range like the white one?

Or splitting the difference in primary length between the top two torque readings? ( am guessing the 32" and 60" torque curves are the best for low-midrange, tho I can not read the actual graph on this computer very well)

What engine simulation program is this? And do I need one?