Exhaust advice

[ericwitte]

Hi everyone,

Built up my 3.2 to a 9.8:1 3.4, 964 cams, Andial flowed intake with different MAF and larger injectors, bored TB, MK long tube headers, Xtreme heads with bigger valves.
Street and rally use only

I have a cool old 73 Bischoff stainless muffler that was modified in period with twin tailpipes - question is, am I restricting the engine too much with a muffler like this? Do I need something with larger outlets? Pipes are inboard of the inlets.


Thank you!


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[Bill Verburg]

Originally Posted by ericwitte

Hi everyone,

Built up my 3.2 to a 9.8:1 3.4, 964 cams, Andial flowed intake with different MAF and larger injectors, bored TB, MK long tube headers, Xtreme heads with bigger valves.
Street and rally use only

I have a cool old 73 Bischoff stainless muffler that was modified in period with twin tailpipes - question is, am I restricting the engine too much with a muffler like this? Do I need something with larger outlets? Pipes are inboard of the inlets.


Thank you!


Sent from my iPhone using Tapatalk

Some say yes others no

My 2cents probably a little at the top of the rev range, not so much around town

also depends on the size of the inlets

are the M&Ks at least 1 5/8" ID?

[ericwitte]

Hi Bill!

Yes they are 1 5/8”. I built the engine for more low end torque and felt that 1.75”, while better for top end, would not be as helpful on the street. The Xtreme CNC program was also designed for lower end. Trying to move torque curve down. Car should be ~2250lbs so it should be pretty sprightly.


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[safe]

If its made like they used to make these (I have one on my 3.2 engine) Both the inlet and outlet are in the same chamber, lower half of the muffler. Its not going to restrict anything. My engine peaked at 220 whp @ 7000

[targa72e]

I tested several different mufflers many years ago on the Dyno. The Red line is a muffler modified like you have pictured. The Blue line is a early muffler with outlets on both ends and the Green is a set of megaphones.



Engine was as 3.0L with big port heads, later 9.3 to 1 pistons, stock cams and CIS. I was running SSI heat exchangers. As you can see all runs were all pretty close with megaphones making the most HP and TQ. Also tested a stock two in one out muffler (not shown) and lost 10-15 HP and TQ across the board.

john

[ericwitte]

Originally Posted by safe

If its made like they used to make these (I have one on my 3.2 engine) Both the inlet and outlet are in the same chamber, lower half of the muffler. Its not going to restrict anything. My engine peaked at 220 whp @ 7000

Thank you. This engine should be putting out high 200s at the crank-I agree with your comment about inlet and outlet in same chamber. Once engine is broken in, will see if it feels restricted at all on hard accel.


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[ericwitte]

Originally Posted by targa72e

I tested several different mufflers many years ago on the Dyno. The Red line is a muffler modified like you have pictured. The Blue line is a early muffler with outlets on both ends and the Green is a set of megaphones.



Engine was as 3.0L with big port heads, later 9.3 to 1 pistons, stock cams and CIS. I was running SSI heat exchangers. As you can see all runs were all pretty close with megaphones making the most HP and TQ. Also tested a stock two in one out muffler (not shown) and lost 10-15 HP and TQ across the board.

john

Thank you.


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