Exhaust restriction/velocity and torque

[Pranav]

Last year I ran on a 54mm restrictor on a brand new motor, 297/260.

After a full season, this winter I reduced my 2.25" pipes to 1.875" for about 18", and put in thicker gear lube, ran 304/261 on a 57mm.

I'll take it.

[drecords]

Last year I ran on a 54mm restrictor on a brand new motor, 297/260.

After a full season, this winter I reduced my 2.25" pipes to 1.875" for about 18", and put in thicker gear lube, ran 304/261 on a 57mm.

I'll take it.

7 ft-lbs of torque is impressive

[Supercharged111]

Last year I ran on a 54mm restrictor on a brand new motor, 297/260.

After a full season, this winter I reduced my 2.25" pipes to 1.875" for about 18", and put in thicker gear lube, ran 304/261 on a 57mm.

I'll take it.

Did it nose over harder up top though? You running stock y pipe?

[Pranav]

Yes on stock y pipe, my "restrictor" pipes are simply what connect the manifolds to the y pipe in place of the cats.

Downstream of the y pipe is a 3" pipe and dynomax straight muffler.

I need to pull up.my old dyno to compare the curves.

[Pranav]

Comparing my charts it did not nose down any further up top; same peak HP at the same RPM. I just gained more lower range torque and the it looks like the peak torque number is a few hundred RPM earlier.

Same HP at the same peak RPM, just more torque and earlier/lower in the range.

Remember, it wasn't JUST the pipes, I took out some intake restrictor and also did run thicker gear lube this time for more protection.