Do you get more torque with or w/o the cat?

[SpeedAintFree]

I just heard on horsepower tv, that when they only put in a hi-flow cat they would have more torque (im guessing with less top end) than a test pipe set up. now he was talking about a 92 mustang, but does the same apply to our cars? I was debating between a DP or a HF-Cat and just ordered a DP because it was cheaper, good or bad move?

 

[bmwisthekey]

i know u were talking about choosing between a high-flow cat or a test pipe, but then u said u bought a DP ( downpipe) if thats the case, yeah i think u made a good move, stock DP is rather restrictive, but whether u go with a high flow cat or test-pipe might come down to emissions laws in your area, but to talk about the mustang on hp tv with the high flow cat making more power over a test pipe on horsepower tv it was NA and u dont want an exhaust that is " Too" free flowing, usually the case with forced induction vehicles the more free flowing the exhaust is the more power there is to be made ( im not saying go slap a 5in exhaust on u know what i mean)

 

[JayRolla]

Yep he is right. The higher flow exhaust on a N/A v8 or whatever will add hp but you loose a little torque. You need a little back pressure to keep a smooth power band. Now with a boosted car you want the most freeflowing exhaust as you can. You may lose some off boost power but who really cares about that.

 

[90gst_sean]

The turbo itself acts as all the restriction the engine needs.

 

[Auto RS T]

Now that you got the downpipe you can just pick up the test pipe for cheap, or make your own. A more free flowing exhaust on a turbo charged vehicle can show power gains by unrestricting the exhaust flow, the turbo already gives the motor the restriction it needs. After a downpipe/test pipe install on a 92 FWD Turbo me and my buddy noticed and increased spool up response.

 

[blackrosenova40]

A turbo does not create a restriction an engine "needs", engines do not "need" exhaust restriction. On a N/A vehicle, exhaust flowing the correct way will create a siphoning effect making the exhaust actually flow quite easily through. On a turbocharged vehicle, you want the quickest spool time, making more horspower and torque, than trying to perfect the siphoning effect that you would like on a N/A vehicle.

There is a term for this siphoning effect , cant recall what it is.

 

[blueman803]

scavenging

 

[blackrosenova40]

Thats the word I was looking for