Lose The Rear Cats, Lose Torque.

hognutz · Mar 2, 2006

mogs01gt said:
Nope, 4 cats on must mustangs and I think the Cali models had 6. If it was a resonator, then there wouldnt be a reason for the rear to o2 sensors .

odbII requires post cat sensors weather you have 2 or 12 so you logic there is flawed. I am not saying the pipe does not have cats. I am just not 100% possitive they are all cats. have you ever removed all 4 items to verify they are cats?

the cali cars have 6 items in the midepipe. like I said I used to think this as well but someone posted in that there were not all cats. I should just go look at my old midepipe close and end all the speculation for sure.

you could possibly be right but if you have never actually verified they are cats you are making an assumption.

mogs01gt · Mar 2, 2006

djtech said:
Well I disagree with your generalizations. I was being sarcastic in my last post because of all the people here who believe catalytic converters will give you power.

See my other posts on the thread and you'll see how I think these changes make a difference.

I wasnt making any generalizations and if you are being sarcastic, put some type of smily or something up. Why would I want to read your other posts when you post something as wrong as what I quoted?

hognutz said:
odbII requires post cat sensors weather you have 2 or 12 so you logic there is flawed. I am not saying the pipe does not have cats. I am just not 100% possitive they are all cats. have you ever removed all 4 items to verify they are cats?

How is it flawed? Why would there be two o2 sensors behind resonators and not behind the 2 front two cats if your assumption is correct? I havent torn mine apart but my friend did for ****s and giggles on his 5.0 and they werent resonators.

the cali cars have 6 items in the midepipe. like I said I used to think this as well but someone posted in that there were not all cats. I should just go look at my old midepipe close.

It was verified years ago they were cats and are there for Cali's strict emissions laws/rules.

you could possibly be right but if you have never actually verified they are cats you are making an assumption.

actually you would be the one making an assumption.

hognutz · Mar 2, 2006

okay I will check it out. if you wrong you owe me a bj for being so cocky about it. there has not been a 5.0 in mustang for a wile. I don't know anything about the 94-95 models so I can't coment on similarities. they were not even 0DBII so I know they don't have the same midpipe. maybe that guy jedi mind tricked me about them not being cats and you are correct.

djtech · Mar 2, 2006

mogs01gt said:
I wasnt making any generalizations and if you are being sarcastic, put some type of smily or something up. Why would I want to read your other posts when you post something as wrong as what I quoted?
...clip...

Perhaps we also disagree on what a generalization is. Let me list the blanket statements that you made that are not correct in all situations (a generalization):

->What happens is, when you remove the cats or get a larger mid-pipe without cats, you flow more creating more power but it moves your power band up slightly.<-

Disagree.

->Now when you put the stock stuff back on with cats, you loose that added power and it moves your power band back down so you feel it sooner.<-

Disagree.

There are many more variables present than just exhaust. The statements you made may be true in some situations but not all.

mogs01gt said:
Why would I want to read your other posts when you post something as wrong as what I quoted?
...clip...

#1). Proper etiquette of a forum is to read all the posts before posting yourself
#2). Why not?
#3). Because it is almost Friday

In all seriousness, what did I post that you felt was so wrong? You seem to agree with some of what I've been saying.

mogs01gt · Mar 2, 2006

djtech said:
Perhaps we also disagree on what a generalization is. Let me list the blanket statements that you made that are not correct in all situations (a generalization):

->What happens is, when you remove the cats or get a larger mid-pipe without cats, you flow more creating more power but it moves your power band up slightly.<-

Disagree.

->Now when you put the stock stuff back on with cats, you loose that added power and it moves your power band back down so you feel it sooner.<-

Disagree.

you can disagree all you want. The fact is that Catalytic converters produce restrictions. Restrictions reduce flow.

There are many more variables present than just exhaust. The statements you made may be true in some situations but not all.
#1). Proper etiquette of a forum is to read all the posts before posting yourself
#2). Why not?
#3). Because it is almost Friday

In all seriousness, what did I post that you felt was so wrong? You seem to agree with some of what I've been saying.

If I read the rest of your posts, I would have used it in the quote. I only quoted what I read and had an opinion on so that is all that matters. I dont have an opinion on the other ones so they dont matter.

hognutz said:
okay I will check it out. if you wrong you owe me a bj for being so cocky about it. there has not been a 5.0 in mustang for a wile. I don't know anything about the 94-95 models so I can't coment on similarities. they were not even 0DBII so I know they don't have the same midpipe. maybe that guy jedi mind tricked me about them not being cats and you are correct.

a BJ huh? Im not being cocky, if you dont like the why I type, dont read it.

hognutz · Mar 2, 2006

like I said I will post either way. If I am wrong I am wrong.

I was joking by the way I don't really want a bj from you. ha ha. just a little humor did not intend to get you all pissy.

300bhp/ton · Mar 2, 2006

mogs01gt said:
The fact is that Catalytic converters produce restrictions.

That's not exactly true.

Some cats can be a restriction. David Vizard (reknown engineer & author) tells us that we need 2.2cfm for every 1hp generated by the engine to not affect flow.

Magnaflow Carsound CATS flow at around 450cfm, so 450 / 2.2 = 205bhp supported flow rate per CAT.

But in the case of the Mustang the CAT only has to handle gases from one cylinder bank or 4 cylinders, so in essence those Magnaflow CATS will have ZERO restriction on an engine producing 410bhp. On engine's producing more power the restirction will be incremental, so even on a 500bhp engine the loss is only likely to be somewhere around 5-20bhp at most, but maybe not even that.

Random Technology's Metal Matrix 3" 7000 Series CATS flow at 598cfm, so the will support 272bhp or upto 544bhp on a dual exhaust setup at ZERO restriction.

The thing all CATS do affect is the exhaust pressure wave. This can have quite a dramatic affect on bhp. However there is no way I know of to get around it.

If you like I can post a link to an article which covers exhaust theory (flow and pressure wave) indepth.

djtech · Mar 2, 2006

mogs01gt said:
you can disagree all you want. The fact is that Catalytic converters produce restrictions. Restrictions reduce flow.

Isn't that obvious? I would never disagree with that statement, glad you've changed your mind to agree with common sense.

mogs01gt said:
If I read the rest of your posts, I would have used it in the quote. I only quoted what I read and had an opinion on so that is all that matters. I dont have an opinion on the other ones so they dont matter.
...clip...

I'll have to remember your name then.... when mogs01gt posts he doesn't pay attention to the whole thread. This makes corresponding with you not worthwhile. I'm here to learn and express my opinions with folks who can converse intellegently (which means informed).

300bhp/ton said:
That's not exactly true.

Some cats can be a restriction. David Vizard (reknown engineer & author) tells us that we need 2.2cfm for every 1hp generated by the engine to not affect flow.
...clip...
If you like I can post a link to an article which covers exhaust theory (flow and pressure wave) indepth.

Please provide that link, I think something present in the pipe would impede flow.

timeless2 · Mar 2, 2006

It's not bad yet, but let's keep focus on the Tech, not the attacks, please.

mogs01gt · Mar 2, 2006

djtech said:
Isn't that obvious? I would never disagree with that statement, glad you've changed your mind to agree with common sense.

I'll have to remember your name then.... when mogs01gt posts he doesn't pay attention to the whole thread. This makes corresponding with you not worthwhile. I'm here to learn and express my opinions with folks who can converse intellegently (which means informed).

Please provide that link, I think something present in the pipe would impede flow.

wow, lets assume someone hasnt read the thread because he quoted one post. Sorry if I missed your post, since you obviously are so well informed.

mrvax · Mar 2, 2006

jimfitzgerald said:
Don't waste you money on a catted X. When and if you get one, get an O/R X. Plus, they are cheap.

Jim, I went from my stock 6 cats H pipe to a Magnaflow Hi-flow catted (2) X pipe. It was any thing but a waste of money. Really helped the car mostly upper rpms. I cannot run cattless where I live.

mogs01gt · Mar 2, 2006

mrvax said:
Jim, I went from my stock 6 cats H pipe to a Magnaflow Hi-flow catted (2) X pipe. It was any thing but a waste of money. Really helped the car mostly upper rpms. I cannot run cattless where I live.

I wonder if Jim referring to a track only car??? I dont want to assume though.

SamMan · Mar 2, 2006

Well I am not sure about the reason and I dont want to get into the debate really but I would like to add myself to the list of those who felt noticable decrease of low end TRQ when removing the cats. This was especially pronounced when spraying. It actually allowed me to hook up ALOT better and vastly improved my 1/8th times as I wasnt trying so hard to feather it out of the hole.

I think I would prescribe to the idea that when removing cats your powerband is moved higher into the RPM range.

300bhp/ton · Mar 2, 2006

djtech said:
Please provide that link, I think something present in the pipe would impede flow.

Well in many ways your right.

But it will only impede flow if it restricts it below the flow requirement.

Think of it this way, If a regular road/street with one lane each way can flow 2 cars at a time. Yet all that is needed is the ability to flow 1 car at a time. So when a restriction occurs such as a parked car (respresenting the CAT), it has only taken the flow from 2 to 1 (2 - 1 = 1). But as the requirement is only the ability to flow one car at a time, it will not affect it.

Now this is quite an indepth thread, but if you do spend the time to read it, it will be very worth while and probably open your eyes to exhaust setups (it did mine ).

http://www.ls1tech.com/forums/showthread.php?t=139142

Now you'll want to skip to post 6 first as the rest is just specific to Fbody's. Post 6 concentrates on headers. Then skip down to post 13 onwards, this is the info from David Vizard.

300bhp/ton · Mar 2, 2006

SamMan said:
Well I am not sure about the reason and I dont want to get into the debate really but I would like to add myself to the list of those who felt noticable decrease of low end TRQ when removing the cats. This was especially pronounced when spraying. It actually allowed me to hook up ALOT better and vastly improved my 1/8th times as I wasnt trying so hard to feather it out of the hole.

I think I would prescribe to the idea that when removing cats your powerband is moved higher into the RPM range.

Yes this is correct.

Remember HP = torque x rpm / 5252

So even if your car makes the SAME torque but slightly higher in the rpms you will gain in HP, but it may feel like a loss in the low end, due to a slightly different profile of the curve and the comparitive difference between low end and high end power.

02BlkStang · Mar 2, 2006

topless98gt said:
Here's a test for everyone to try: remove your mid-pipe and your cat-back. Drive your car and see how sluggish it is.

Drove to an exhaust place about 8 months ago with just my H pipe on, had vans passing me off the line

jstreet0204 · Mar 2, 2006

mogs01gt said:
Nope, 4 cats on must mustangs and I think the Cali models had 6. If it was a resonator, then there wouldnt be a reason for the rear to o2 sensors .

This is correct. The first set are Light-off cats or mini cats that are placed closer to the manifolds to get hot very quickly. The second set are conventional cats. I don't know about the cali models.

Jonstantine · Mar 7, 2006

o3redfire said:
Regarding emmissions .... I put cats on the car this past FALL - passed emissions 1st shot. AND I GAINED HP AND TORQUE. My exhaust was just TOO big and I was losing some power obviously. My NA numbers went from 307/308 to 315/316 -this is from scott's thread

i believe what you said happened - but i dont believe your explanation of it
you dont lose power from too big of an exhaust

the most important exhaust tuning is in your secondary/collector pipe lengths
your cats acted as a resonator box (2nd page very bottom)
http://superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/

that should resolve your exhaust questions

Lose The Rear Cats, Lose Torque.

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