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September 11th, 2010, 11:55 AM
Cat. converters and torque
I am debating whether there are gains to be had by removing or upgrading my cat. converters. My options are basically
-leave them
-gut them (for off-road racing use only)
-replace them with high flow cats
-eliminate them with a straight pipe (again, off-road racing use only) :)
I would really like advice because I am approaching this dilemma scientifically (is that a word?) and my
strategy is the following:
- absolutely no loss of torque is acceptable
- I am on a very tight budget
I understand just enough about "exhaust aerodynamics" (that's definitely not a word) to be confused and undecided.
*I have experienced great loss of low rpm torque from reducing back pressure in small engines
*I understand that back pressure is somehow needed unless we are talking full race high rpm launching geared & slicked race vehicles
*I heard that velocity is good for creating or encouraging a good intake charge
*I know there are rythmhs to intake and exhaust pulses, but don't know much about how to optimize them
*Chevy trucks is my experience often sound smoother and meaner with the stock cats
On that note a restriction that chokes power on my 110k mile factory cats and a cheap mod that could drop a few tenths of my 1/8 mile ET is irresistible. What do you recommend. Stock truck with 3.42 gears and a 4.8 Vortec, would like 4.10s in the future. Dreaming of heads and cam but that will not happen soon unless I win the lottery. Plan on a cold air intake, under-drive pulleys, electric fan, and new oxygen sensors plus wide-band to perfect my tune. I have advanced timing and overall "aggression" and it has responded well.
Current exhaust setup: (please don't laugh)
- cheap Summit shorty headers with stock old gaskets, wrapped with DEI thermal tape and spray.
-stock cats, seem ok 110k miles
- stock midsection, couple tiny rust leaks in this :(
- rusty but not badly leaking catback with OLD Flowmaster but sounds good
Thanks guys! :)
I am debating whether there are gains to be had by removing or upgrading my cat. converters. My options are basically
-leave them
-gut them (for off-road racing use only)
-replace them with high flow cats
-eliminate them with a straight pipe (again, off-road racing use only) :)
I would really like advice because I am approaching this dilemma scientifically (is that a word?) and my
strategy is the following:
- absolutely no loss of torque is acceptable
- I am on a very tight budget
I understand just enough about "exhaust aerodynamics" (that's definitely not a word) to be confused and undecided.
*I have experienced great loss of low rpm torque from reducing back pressure in small engines
*I understand that back pressure is somehow needed unless we are talking full race high rpm launching geared & slicked race vehicles
*I heard that velocity is good for creating or encouraging a good intake charge
*I know there are rythmhs to intake and exhaust pulses, but don't know much about how to optimize them
*Chevy trucks is my experience often sound smoother and meaner with the stock cats
On that note a restriction that chokes power on my 110k mile factory cats and a cheap mod that could drop a few tenths of my 1/8 mile ET is irresistible. What do you recommend. Stock truck with 3.42 gears and a 4.8 Vortec, would like 4.10s in the future. Dreaming of heads and cam but that will not happen soon unless I win the lottery. Plan on a cold air intake, under-drive pulleys, electric fan, and new oxygen sensors plus wide-band to perfect my tune. I have advanced timing and overall "aggression" and it has responded well.
Current exhaust setup: (please don't laugh)
- cheap Summit shorty headers with stock old gaskets, wrapped with DEI thermal tape and spray.
-stock cats, seem ok 110k miles
- stock midsection, couple tiny rust leaks in this :(
- rusty but not badly leaking catback with OLD Flowmaster but sounds good
Thanks guys! :)