High flow cats and horsepower
High flow cats and horsepower There is a lot of debate and rumors around the impact of high flow cats on HP and torque. Here are some actual numbers. This article is from HotRod Magazine's Do it yourself series "engines", Spring 2008. They take a 6.0L truck engine and mod it from mild to wild. I highly recommend the article. Anyway here is what they have to say about cats:
On avg the cats "cost" just 2.6 HP and 3.8 lb/ft of torque through the entire power range. Please keep in mind this is at the flywheel NOT the rear wheels.
I know this is just one study but I figured I'd put it out there.
I know this is just one study but I figured I'd put it out there.
On avg the cats "cost" just 2.6 HP and 3.8 lb/ft of torque through the entire power range. Please keep in mind this is at the flywheel NOT the rear wheels.
I know this is just one study but I figured I'd put it out there.
I know this is just one study but I figured I'd put it out there.
I wonder what the difference would be with a higher hp motor. If the I have the cash I might do a before/after dyno comparison with my car when I get my magnaflow 59959 cats put on.
Part 1: bolt ons (headers, cats, LQ9, LS1 ,LS6 and FAST intakes, new rockers)
Part 2: heads and cam (L92 and L76 intake and several cams) then a carb intake.
Part 3. Magnuson 1900 series blower and alky injection.
They ended up with 751 HP on the stock bottom end
There is a lot of debate and rumors around the impact of high flow cats on HP and torque. Here are some actual numbers. This article is from HotRod Magazine's Do it yourself series "engines", Spring 2008. They take a 6.0L truck engine and mod it from mild to wild. I highly recommend the article. Anyway here is what they have to say about cats:
On avg the cats "cost" just 2.6 HP and 3.8 lb/ft of torque through the entire power range. Please keep in mind this is at the flywheel NOT the rear wheels.
I know this is just one study but I figured I'd put it out there.
I know this is just one study but I figured I'd put it out there.
On avg the cats "cost" just 2.6 HP and 3.8 lb/ft of torque through the entire power range. Please keep in mind this is at the flywheel NOT the rear wheels.
I know this is just one study but I figured I'd put it out there.
I know this is just one study but I figured I'd put it out there.
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Just removed my well-ported MAC mid's and ORY ... replaced them with 1 7/8" primaried American Racing headers with cat'd Y ... gained 25/17. Cats are 200 holes per inch instead of most aftermarket cats which are 300 holes per inch.
Re'
I think the cats might be 300 holes-per-inch which will be a little more rsetrictive, however, form all the dyno comparison I have seen on this forum, the QTP's are about as good as they get. You'll def pick up some good power.
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.......been getting it for over 20 years. 
Holes per inch isn't really meaningful. You need to find out CFM.
We sell Random tech cats. They have ceramic core ones for modified motors and them higher flowing metal substrate core ones for wildly modified motors. Both flow better than most mufflers!
We sell Random tech cats. They have ceramic core ones for modified motors and them higher flowing metal substrate core ones for wildly modified motors. Both flow better than most mufflers!
200 holes-per-inch is a HUGE difference ... who you tryin' to kid? I've had both the ceramic core Random Tech 'bullets' AND metal core Random Tech 'bullets' cats and they both robbed me of power on the dyno, whereas, with the 200 hole-per-inch American Race Header cats cost me nothing noticeable ... period. CAT's vs mufflers? Where the did THAT come from? Same diameter cats with 200 holes-per-inch will ALWAYS outflow cats with 300 holes-per-inch ... doesn't take a rocket scientist. Did I misread what you typed or did you mis-type what I just read?
200 holes-per-inch is a HUGE difference ... who you tryin' to kid? I've had both the ceramic core Random Tech 'bullets' AND metal core Random Tech 'bullets' cats and they both robbed me of power on the dyno, whereas, with the 200 hole-per-inch American Race Header cats cost me nothing noticeable ... period. CAT's vs mufflers? Where the did THAT come from? Same diameter cats with 200 holes-per-inch will ALWAYS outflow cats with 300 holes-per-inch ... doesn't take a rocket scientist. Did I misread what you typed or did you mis-type what I just read?
Holes per inch is NOT a measurement of flow. As such you cannot compare one brand to another like that. One brand could have larger holes and the other smaller. They could be structured differently from brand to brand. Holes per inch is an advertising method that doesn't give any data as to how the cat actually flows. That is what we are saying.
So you know I'm being truthful ... here's a link to a post about the power I picked up:
https://ls1tech.com/forums/showthrea...1128&highlight=
This an excerpt from the thread:
Originally Posted by Mike Norris
Hey All,
Jack just picked up his car and should be on here after a bit. The 1 7/8" headers fit great and the cats have all kinds of clearance. The car pulling away sounded great and had no raspiness to it as it did when it had the Mac's and OR Y on there.
I was very surprised at the gains from the change of the Mac's w/ OR to the ARH 1 7/8" w/ Cats with no tuning changes. I did a locked baseline run Sunday after Jack dropped off the car to have a fair comparison instead of going back to the old runs. My base runs were close to Jack's last dyno numbers.
I will let Jack post up the numbers if he wishes. I can tell you the gains were more then what was predicted here by Disturbed Bird before the tune. I can get more specific once Jack posts.
Have a good one all.
Mike Norris
__________________
Mike Norris Motorsports
101 First Street
Winter Garden, FL 34787
407-616-2518
thevettedr@aol.com
www.mikenorrismotorsports.com
Jack just picked up his car and should be on here after a bit. The 1 7/8" headers fit great and the cats have all kinds of clearance. The car pulling away sounded great and had no raspiness to it as it did when it had the Mac's and OR Y on there.
I was very surprised at the gains from the change of the Mac's w/ OR to the ARH 1 7/8" w/ Cats with no tuning changes. I did a locked baseline run Sunday after Jack dropped off the car to have a fair comparison instead of going back to the old runs. My base runs were close to Jack's last dyno numbers.
I will let Jack post up the numbers if he wishes. I can tell you the gains were more then what was predicted here by Disturbed Bird before the tune. I can get more specific once Jack posts.
Have a good one all.
Mike Norris
__________________
Mike Norris Motorsports
101 First Street
Winter Garden, FL 34787
407-616-2518
thevettedr@aol.com
www.mikenorrismotorsports.com
More info on flow:
http://www.randomtechnology.com/index.html
http://www.randomtechnology.com/technical.html
http://www.randomtechnology.com/index.html
In fact, Random Technology high efficiency catalytic converters actually have a higher flow capacity than many mufflers. As an example, a 3" diameter 7000 series SuperStainless catalytic converter flows 617 cfm. Most 3" diameter high performance mufflers flow less than 475 cfm at the same test pressure. Random Technology direct fit SuperStainless catalytic converters are available for most domestic and imported vehicles. Custom catalytic converters with inlets and outlets up to 5" in diameter are available.
Thanks that is good to know but I don't think its that simple. Flow isn't a the best representation of restiction. For instance if the engine itself only flows 300 CFM then it wouldn't make much of a difference if the cats flowed 400 or 600 CFM.