Lol i found out the hard way. I was driving home and a mustang pulls up next to me. He wanted to go so we did. I had my cutout open on the way home to enjoy the loudness. lol Anyways we go and I felt so slow in the lower rpm range until I got going. I tell you what though I see such a huge increase in upper rpm power with my LT headers. I love them

BTW I still beat him

 

i believe you lose the exhaust velocity when you remove the rest of the exhaust system and run nothing but headers. correct me if im wrong though.

mine does the same thing. feels a little less peppy down low w/o the catback on.

 

The cut outs will kill low end torque especially if you have them right near the collector. The point at which the exhaust provides the scavenging pulses(which is where the benefit of LT headers comes from) is directly related to the length of the collector. For a typuically driven street car with average gears and stall speed, a collector can be upwards of 40" long to get the torque peak down to where it's useful (and seat of the pants obvious).
With the cut outs at or near the end of the header, then the peak is way up in the torque curve and you get that sluggish response at low RPM. The difference can be 40 ft lbs or more at 3000 RPM.

 

My cutout is at the rearend

 

surprised you did feel much of a loss with open cutout. I ran my car with a flowmaster muffler and then without that muffler, basically a open pipe dumping over the axle acting like a rear cutout if you will. Car felt faster with the open pipe all around because of the extra flow, while keeping similar exhaust tuning length of the pipe.

i can see a open header making less lowend cuz its tuned for high rpm power when its open collector or the cutouts are placed within 30 inches of the collector. That will tune over 5000rpms, and TPI is done making power since 4500

 

I'm curious. What do you have for an exhaust system?

 

My car and 2 of my buddies had cutouts and we made 4-5 hp more on the dyno. Friend had dyno we used almost daily. He first trying only removing the muffler. but that did nothing.

We all had the cutouts on the pipes right at where the floor pan bends up to the firewall.

We all had Incon twin turbo kits but I don't see what that changes.

 

You're not talking about LT headers with a turbo.

 

I don't know I mean the headers are very long go to the bottom of the oil pan. But my new exhaust is dumped before the rear end and a bullet muffler.

 

Different set of principles between long tube headers and a turbo. With your turbo you're not concerned about tuning collector lengths. At least not in way we do in a normally aspirated setup.

 

Actually comes to find out. I gained better track time with them off. SO my exhaust goes liek this. LT headers then two straight pipes into a Y. At the rear end I have a cutout. ALl exhaust is 3"