chadnol10

iTrader: (41)

how much of a difference will there be between high flo cats vs. no cats when it comes to performance and sound. i'm thinking about sounding my ecu chip in for a tune but i'm not sure if i wanna have cats put on or not with my new headers.

Torque_Wrench

iTrader: (13)

If you don't use the cats, it will be really fu*king loud! With a decent amount of rasp. I like that sound myself but other don't. Performance wise.....look at it this way...if you got LT headers and no cats and a straight through muffler, then you got pretty much NO BACKPRESSURE. And you actually have to have a certain amount of backpressure to operate normally. You may loose some torque on the bottom.

Starz T/A 17

iTrader: (6)

I mean unless you know the guy, Id ask for brand and whatnot, some cheapo cats will blow out after a while or be very restrictive

chadnol10

iTrader: (41)

what cats and who has the best price?

caviness

iTrader: (14)

search metal cats,cost you about 5hp,they are the best.oh yea before i forget,if somebody tells you you need backpresure,stick him right in the jaw hard as u can,cause he is giving you misinformation!!!!

caviness

iTrader: (14)

they are not all the same you get what you pay for!!

chadnol10

iTrader: (41)

what about magnaflow

caviness

iTrader: (14)

good choice.

Torque_Wrench

iTrader: (13)

Hey I hate to burst your bubble....but you ain't "stick" ing me right in the jaw. I do this for a living! You have to have a certain amount of backpressure to run at optimal performance levels. No backprerssure = loss of low end torque. Trust me on this because I've been to classes from general Motors since 1998 and I've taken the calsses and listened to the instructors for GM tell me that you HAVE to have a certain amount to preform correctly. So do you suppose the General Motors and all their vast knowledge just made that up?

Ace$nyper

iTrader: (8)

You never said you passed those classes.

It's not back pressure it's well I'll give you a hint the letter V and speed.

I see General Motors classes are about as worthwhile as investing in their stock lmfao.

Torque_Wrench

iTrader: (13)

So in all your wiseness, you think that no backpressure will not hurt your low end torque?

If so, then you're as useless as the other guy.

Ragtop 99

iTrader: (7)

When you say you do this for a living, do you mean design exhaust systems?

I don't think GM is wrong, I think you misheard or misunderstood. Backpressure doesn't increase low end torque. Exhaust gas velocity and pulse timing do. The problem is that it is tough to build an emission compliant system with no backpressure. GM engineers tune the car around that fact. If the backpressure is removed as part of the exhaust work and then one changes the tuning. Without changing the tune, performance can be negatively impacted in some cases.

Loss of low end torque on some header systems is due to loss of exhaust gas velocity, not failure to acheive back pressure. In fact many headers for these car show gains in the low end.

Ace$nyper

iTrader: (8)

I never said I was loaded with wiseness, just your blatent misunderstanding and chest beating does seem to put me miles ahead of you as far as simple understanding on exhaust theorys.

I happen to have a top of the line header maker in my phone, he's a dear friend. Possibly have picked a trick or 2 up from him.

It won't if you propperly setup your exhaust back pressure is always bad, no if ands or buts.

Where this rumor that if you arn't lying GM foolishly pushed to you, started is many exhausts when you lose backpressure *thats a good thing* You also lose exhaust volcity and the bigger part of the puzzle scavanging.

Scavanging is why a car with headers will make more power then one thats open blocked. Esp in the whole band instead of just peak and top of the RPM band when the gases move faster due to engine speed.

So what is it, GM offers that poor a level of classes to tech or are you lieing online for crediblity? Either way it's kinda sad.

Ragtop 99

iTrader: (7)

Knock off the name calling and pissing and stick to the technical discussion or this will be closed.

Torque_Wrench

iTrader: (13)

You are 100% correct in your reply. And basing what my GM instructor told the class In Blountville Tn., on April 6th of 2006 was "on the vehicles produced today, a certain amount of backpressure if needed to make your vehicle preform at optimal levels"....he also did mention that all OEM vehicles are made with very restrictive exhaust systems and freeing up some backpressure is needed.

As for what I do for a living is, I am the Service and Parts manager at a GM Dealership. And we do exhaust also.

So keeping that in mind, we put headers (LT's) on a 2001 Camaro and used 3 inch pipe and a Loudmout muffler. The car actually ran worse. We went back and replaced the 3 inch pipe with 2 1/4 and the car ran suprisingly better.

Torque_Wrench

iTrader: (13)

Simple friend....I'm not lying for credibility (who would do that?)....the simple mistake is....the class didn't go in depth about the theroy of scavanging or exhaust gas pulsation. The Instructors remark was stated earlier (i won't write it down again)....and I take his word for it.

Ragtop 99

iTrader: (7)

The 2.25" pipe might have increased gas velocity on the low end. some headers with 2.5" collectors instead of 3" show better low end gains, but some of it was from lack of tuning.

Ace$nyper

iTrader: (8)

Then he should not have brought it up and over simplfiled that, because you were informed impropply and to the best of your ablity shared your info that wasn't correct.

There by spreading misinformation.

These cars are large motors and move a good deal of air, I'm not quite sure why a simple setup of long tubes and a mostly 3" straigh setup would hurt the car. Unless the ECU was being picking as long as the headers were of a good make and I can't off hand name a poor Long tube for these cars it should have helped the whole band.

2.25 piping would probbly be too small for a motor of this size, stock is 2.7 from what one of the stickies on this site said, and the most "choking" part is the muffler.

Torque_Wrench

iTrader: (13)

We had actually had a Nelson PCM tuned for this car and before we put the PCM in...(with the 3 inch pipe) the car did miss ever slightly. The PCM cleared alot of that up except for the Bank 2 spark plugs had been fouled in that short time.

I also noticed on my own truck.....I put LT headers on it and fabbed my own cat-less Y and wnet into a Dynatech muffler and I also noticed I lost considerably on the low end torque. So days later I got my PCM re-tuned for a catted Y and I re-installed my 2 cats with the same header and muffler set up, and I noticed a definite increase in the low end torque and power.

These examples are what I'm basing my responses from.

I'm not trying to call names or **** in anyone's face, but it seems everytime a person posts some advice stating their personal experiance on here, then some one like "Ace Snyper" or "Caviness" responds by calling you a liar or saying that your "stupid" or your ideas "suck". Why even post on LS1Tech if others are going to go right off and call you a liar? That's what I don't like about guys like that. Why not listen to others experiance and offer your insight into it instead of tryin to make someone look like a dick?

NoGamesLS1

iTrader: (16)

Was the car tuned after the header/exhaust install? Probaly not. There is your problem, not the loss of backpressure. Why do the fastest motors in the world run straight headers then?