Good info and good point!
Thanks,
Tony
Thanks,
Tony
More power with or without cats?????
- Thread starter Z O SICK
- Start date
yes having cats on will make more boost but that doesnt mean its going to make more power then o/r.
Say you ported your heads and put LTs on your car. You will make LESS boost but gain power. Boost is just a measure of restriction.
I GAINED power going from my catted H to an O/R MRT H pipe. To the comment to the person said someone lost power switching to an O/R X was because they didnt retune for it and went leaner. Thats why he didnt make any more power.
My car with the cats on it smells worse then the O/R pipe does. I love the sound to. i just had to put my stock H pipe back on the other day to go to inspection. The car felt like shit. I used to be able to lay into it around 3500 RPMS in 2nd gear and leave a 200 ft strip. i could barely spin the tires in 1st with the cats on. Put the O/R pipe back on last night car feels much better.
The TQ and Hp curve do not change. Here is my before and after graph. identical curves. O/R made more power period
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Just put in a set of 4.10s and...ABACADABRA... your low end torque will re-appear! ;-)
Seriously, I have headers AND an O/R X; my gears offset the loss and allow my car to breathe up top.
With your ported Apten, you may actually pick up power on the low end with the O/R X. Some who has done this may want to correct me if I am wrong.
Thanks for the dyno sheet "juiced46". It always helps to have some objective material to back something up. Do you think the MRT off-road H has something to do with the fact that your car didn't loose anything down low? I have always been of the opinion that off-road H's were better down low than off-road X's. This isn't based on back to back dyno runs, but simply seat of the pants experience. I installed an off-road X on my old 99' Cobra and lost a ton of torque down low(seat of the pants meter). Two days later I installed the same brand X with cats and the car felt fine again.
A couple of misnomers on this thread
here's the theory behind engines in general (and imgoing to toss around some vauge numbers, so bear with me, i dont feel like looking it up)
here's the facts
there is a certain ratio of fuel to air that needs to be burned for optimal power
the more fuel/air you burn, the more power you get
(i'm not even going to get into the timing aspect, so we'll stop here)
now, why do you think cars come supercharged / turbo charged? thats right, to burn more air/fuel
now, with that in mind, WHY IN GODS NAME would you want to RESTRICT airflow when the WHOLE REASON you have that metal box with screws in it is to get more air flowing..
whats that all mean?
Cats restrict air flow, stock exhaust restricts air flow, and on a force inducted engine, reducing airflow restriction is the key to easy, safe power.
bigger intake, bigger "out take" (exhaust) the smoother and better flowing the "in" (intake, IC pipes, blower) the "through" (heads, in ourcase thats about it) and "out" (exhaust from the block back) the more effecient, more powerful, and longer lasting your set up will be.
so ditch the cats, you'll thank yourself for it later
here's the theory behind engines in general (and imgoing to toss around some vauge numbers, so bear with me, i dont feel like looking it up)
here's the facts
there is a certain ratio of fuel to air that needs to be burned for optimal power
the more fuel/air you burn, the more power you get
(i'm not even going to get into the timing aspect, so we'll stop here)
now, why do you think cars come supercharged / turbo charged? thats right, to burn more air/fuel
now, with that in mind, WHY IN GODS NAME would you want to RESTRICT airflow when the WHOLE REASON you have that metal box with screws in it is to get more air flowing..
whats that all mean?
Cats restrict air flow, stock exhaust restricts air flow, and on a force inducted engine, reducing airflow restriction is the key to easy, safe power.
bigger intake, bigger "out take" (exhaust) the smoother and better flowing the "in" (intake, IC pipes, blower) the "through" (heads, in ourcase thats about it) and "out" (exhaust from the block back) the more effecient, more powerful, and longer lasting your set up will be.
so ditch the cats, you'll thank yourself for it later
TargeT,
What you say seems to make sense, and definitely on supercharged cars. My 99 wasn't blown when I put the off-road X on it. Does anyone know of an off-road pipe comparo thread in the archives here?
What you say seems to make sense, and definitely on supercharged cars. My 99 wasn't blown when I put the off-road X on it. Does anyone know of an off-road pipe comparo thread in the archives here?
My thoughts exactly. :rockon:
i have the exact same set-up as someone on here and i have 459rwhp and 477 rwtq, i have no cats on my Bassani's, while he has 451 rwhp and 460 rwtq with cats on his bassani's...
Those are some nice gains just from taking off the cats. One more question. Can i somehow tell my car that i have cats with my predator so i dont trip any codes or do i just have to buy mil elimators?
Tony
Tony
Yes.
I dyno'd with another board member here back in April. Our cars had the same pulley, CAI, exhaust, etc. but he had an O/R X-pipe and I had a catted X-pipe. We even used the same custom tune (just turned off the 02's via Predator). Other than spark plugs and an idler our cars were identical. He dyno'd about 20 RWHP lower. We were all suprised! Just to make sure it wasn't the idler or the plugs, another guy (again, same exhaust, CAI, pulley and tune) jumped on the rollers and ended up making ~ 15RWHP more. These are the final numbers after tuning each car for a good A/F. :shrug:
If you used the same tune then the AFs would be different. Swapping to an O/R pipe leans it out
Yeah and beyond all that, the real test would have been swapping him pipes because it really doesn't matter who's making more power than the other, - factory cars can run 20-30whp different on the dyno - also it sounds like you were on the same dyno, but it's not 100% clear - if it's different dyno's it's even more flawed, and even if it's the same dyno your cars could be at different engine temps, etc.
The only real test is back-to-back pulls on a hot car, with swapping 1 component at a time.
The only real test is back-to-back pulls on a hot car, with swapping 1 component at a time.
Bah.... running without cats is so ghetto. Can you say hillbilly? I can't freaking stand riding next to a redneck car that has that exhaust smell all the time... don't your passengers ever complain about how it stinks inside your ride? And DON'T tell me without cats there is no difference... hahaha.
the biggest un-answered question that now arises to all the catless believers saying air pump, more intake, more outtake, etc, etc.... cats are a restriction, more power period especially on a supercharged car....
if that is the case then what about headers? they obviously are more efficient, theres no doubt they flow better.
then why is there reported losses with bassani mlh, bbk longtubes, kooks, etc? granted every car doesnt see a loss but there are plenty of people out there completely unsatisfied with their results. EVEN with a re-tune numbers didnt change. this can only lead to the conclusion that there should be "some" backpressure. how much? who knows but until there is more proof theres nothing here that holds any water except for a bunch of opinions.
the guy who poasted his dyno chart up earlier. he gained over 30rwhp. i just cant believe that unless his cats were clogged or somethng. :shrug:
if that is the case then what about headers? they obviously are more efficient, theres no doubt they flow better.
then why is there reported losses with bassani mlh, bbk longtubes, kooks, etc? granted every car doesnt see a loss but there are plenty of people out there completely unsatisfied with their results. EVEN with a re-tune numbers didnt change. this can only lead to the conclusion that there should be "some" backpressure. how much? who knows but until there is more proof theres nothing here that holds any water except for a bunch of opinions.
the guy who poasted his dyno chart up earlier. he gained over 30rwhp. i just cant believe that unless his cats were clogged or somethng. :shrug:
Redneck? I dont think so. If i was a redneck id be driving a lifted 1984 Ford pickup with flowmasters.
Inside of my car does not smell at all. My clothes dont smell, nothing. :rollseyes It smells worse when the cats are on.
then thay are clogged. which would explain the 20+ rwhp increase
sigh...
You must be dreaming. Smells worse than when the cats are on? Maybe ask one of your friends who aren't into performance cars if your car has any foul smell... I was just at an exhaust shop and saw an '01 mustang GT with an offroad H-pipe, and it smelled something awful....
You must be dreaming. Smells worse than when the cats are on? Maybe ask one of your friends who aren't into performance cars if your car has any foul smell... I was just at an exhaust shop and saw an '01 mustang GT with an offroad H-pipe, and it smelled something awful....
Sorry they arent clogged. So you are saying i made 451rwhp SAE on clogged cats, a catback, non ported blower 2.93 and a filter/? :lol: :lol:
I put my stock H pipe on for a few days last week and the O/R H has a better smell. Nobody complains when they drive in or behind my car. Everyone has their opinions. Ill keep my o/r pipe over any catted pipe. If you dont like the smell, then keep your cats on. IMO the O/R pipes do not smell bad at all.
pretty much :lol:
with the same setup as you and an apten i made 502 rwhp, with clogged cats i made 477 rwhp. subtract 25 rwhp for an apten and BINGO your right at 452 rwhp....
cats dont smell man. theyre odorless. if your cats stink then theyre bad or your tune is off, period.
catted or non catted? who cares thats all personal preference. i like my car quiet, thats the only reason mine are on. :coolman:
seeing as how the smell is off subject, is anyone gonna give an opinion on the whole header theory. if the "AIR PUMPS" so many people like to call our engines need to flow more in and out then whats up with the whole header problem? it is more efficient, right? i think this lays to rest the whole less restriction on the exhaust side is good.
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