Hello,

Have a DT Header on the way...This is what I'd like to do...

Header to 2.5" Highflow cat,2.5" to Flowmaster  two chamber Muffler that has two 2.25" outlets,then 2 tail pipes,one on each side. Is this to much flow???I know it needs back pressure but the cat should hold it back some.....It's a 8valve 1.6 I need opions before I order cat and muffler.

Thanks Tom K.

 Ever heard a fart in a wind tunnel               Kidding

 I don't think you'll have much back pressure if any ( even with cat ), I have 2"  (O.D.)all the way with no cat and a turbo muffler and you don't feel alot of tailpipe exhaust ( hand on end of pipe) that's with a fresh engine in it.

 Maybe go 2.25 to the muffler and 1.5 dual out of the muffler??

 My .02
Steve.

Ive been told anything over 2.25 - 2.5 is to much and will result in loss of power..


I have a calmini header and I am running 2.5 and its pretty perky.


I have also hear d putting a flowmaster on a tracker/kick will be very loud....and thus not highly recomended (this is what the muffler shop told me)

(Ive also heard it will make your car sound like a boat unless you have a v8)

One of the technicians at work told me that the less backpressure you have the better. I found this hard to believe, as backpressure makes bottom end better, but I found that while I was running my trackick with the cat but no muffler, it works better all around (bottom end and top end)

One of the technicians at work told me that the less backpressure you have the better. I found this hard to believe, as backpressure makes bottom end better, but I found that while I was running my trackick with the cat but no muffler, it works better all around (bottom end and top end)

Hmmm thats interesting, seems to defy what one would think, maybe I should try something like this out and see what the results are

Ive wrote many articles on this discussion.

Backpressure at the valve, on the head, at the exhaust port.... is bad.. always, from a power perspective. Its true you can burn a valve with too little BP, but then you have a wimpy engine. But... I've never burnt a valve, even with 2" straight pipe on my 3 Cyl 1.0L sprint at 7500 RPM... which I drove for 60,000 kms.

However, too little backpressure in your exhaust can create more backpressure on the head at the exhaust valve, specifically at lower RPM.

Without delving into a 3 page discussion.... when you have too little backpressure in your exhaust system, the exhaust pulse (which is followed by a vacuum pulse) rushes out of the exhaust leaving a vacuum behind it, and fresh air rushes INTO your exhaust to fill the vacuum, and collides with the next exhaust pulse, creating backpressure at the head.

This goes away at higher RPM for a HP gain, the best exhaust is horn shaped like on a motorcycle. Narrow at the begining and slowly widening, this gives you the most area under the TQ curve, or in other words, the most overall HP in your powerband.

For me, this was the best setup, and still is I cant believe how well it works:

http://x90.zukiweb.com/bbs/index.php?topic=644.0

The sound is awesome at 5000 RPM but so quiet below that, and yet great overall TQ. (I think the reason is the dual setup, one pipe is about a half wave length longer then the other pipe, so at lower RPM's the noise cancels out)

-Steve

I have also hear d putting a flowmaster on a tracker/kick will be very loud....and thus not highly recomended (this is what the muffler shop told me)

(Ive also heard it will make your car sound like a boat unless you have a v8)

]

I have the doug thorley header, 2.5" to the muffler a 3" big block 2 chamber flowmaster, then 2.25" the rest of the way out.  Mine actually sounds pretty good, which surprised me when I put it on, but I really like it now.  Its not that loud and not that annoying fart can buzzing sound.  Granted it is not quiet, you can hear it...but doesn't sound all that rice-burner-ish.

Don't laugh the muffler was given to me

You don't want backpressure, that's what you're trying to get rid off but what you do want to do is to keep the exhaust velocity up for good scavenging. The problem is people fit too large an exhaust in an effort to remove backpressure and then say that they lost power because the engine needs some backpressure to run right. What they really did was to open it up so much that the velocity of the exiting gases fell and the scavenging effect with the pulses was lost. In effect what you are looking for is the smallest pipe with the least backpressure for the job. You can even reduce the pipe dia. at the rear of the system a little as the heat is going out of the gases at that stage and they are starting to slow down.

Just to clarify for some what scavenging is, it is in effect creating a vacuum to help draw out the exhaust gases and at the same time also helps to draw in a fresh charge. Backpressure is the enemy of this.

Ive wrote many articles on this discussion.

Backpressure at the valve, on the head, at the exhaust port.... is bad.. always, from a power perspective. Its true you can burn a valve with too little BP, but then you have a wimpy engine. But... I've never burnt a valve, even with 2" straight pipe on my 3 Cyl 1.0L sprint at 7500 RPM... which I drove for 60,000 kms.

However, too little backpressure in your exhaust can create more backpressure on the head at the exhaust valve, specifically at lower RPM.

Without delving into a 3 page discussion.... when you have too little backpressure in your exhaust system, the exhaust pulse (which is followed by a vacuum pulse) rushes out of the exhaust leaving a vacuum behind it, and fresh air rushes INTO your exhaust to fill the vacuum, and collides with the next exhaust pulse, creating backpressure at the head.

This goes away at higher RPM for a HP gain, the best exhaust is horn shaped like on a motorcycle. Narrow at the begining and slowly widening, this gives you the most area under the TQ curve, or in other words, the most overall HP in your powerband.

For me, this was the best setup, and still is I cant believe how well it works:

http://x90.zukiweb.com/bbs/index.php?topic=644.0

The sound is awesome at 5000 RPM but so quiet below that, and yet great overall TQ. (I think the reason is the dual setup, one pipe is about a half wave length longer then the other pipe, so at lower RPM's the noise cancels out)

-Steve

You don't want backpressure, that's what you're trying to get rid off but what you do want to do is to keep the exhaust velocity up for good scavenging. The problem is people fit too large an exhaust in an effort to remove backpressure and then say that they lost power because the engine needs some backpressure to run right. What they really did was to open it up so much that the velocity of the exiting gases fell and the scavenging effect with the pulses was lost. In effect what you are looking for is the smallest pipe with the least backpressure for the job. You can even reduce the pipe dia. at the rear of the system a little as the heat is going out of the gases at that stage and they are starting to slow down.

Just to clarify for some what scavenging is, it is in effect creating a vacuum to help draw out the exhaust gases and at the same time also helps to draw in a fresh charge. Backpressure is the enemy of this.

Great Great Information,

Now I understand something with some great background information

I have the doug thorley header, 2.5" to the muffler a 3" big block 2 chamber flowmaster, then 2.25" the rest of the way out.  Mine actually sounds pretty good, which surprised me when I put it on, but I really like it now.  Its not that loud and not that annoying fart can buzzing sound.  Granted it is not quiet, you can hear it...but doesn't sound all that rice-burner-ish.

Don't laugh the muffler was given to me

I stand corrected 

Ok,

You guys talked me into it.... .I had a flowmaster on a V6 Dodge Pick-up and it sounded like a Nascar!!!...Kinda looked like one to....LOL.But the DT Header is the Split one that has the two into one pipe into one large one...You Know......Tri Y.... So it should work ok...If not I just drop the pipe from the converter to the muffler to 2.25. Heck the way I drive it might be smashed shut in a few weeks...LOL.

Later Tom K.

Quote from: toolman21 on March 28, 2006, 01:50:34 PM

I have the doug thorley header, 2.5" to the muffler a 3" big block 2 chamber flowmaster, then 2.25" the rest of the way out. Mine actually sounds pretty good, which surprised me when I put it on, but I really like it now. Its not that loud and not that annoying fart can buzzing sound. Granted it is not quiet, you can hear it...but doesn't sound all that rice-burner-ish.

Don't laugh the muffler was given to me

I stand corrected

Hehe...seriously...its not that bad....just saying.

From my experience, I have the Calmini Header running to 2" exhaust.   The Muffler Shop (yeh, original name for a muffler shop) told me anything more than 2" would not really make sense on a 4 cylinder, this was the owner telling me and hes an old family friend.   I have the stock cat though, Im meaning to replace or just get rid off completely.   I can see exhaust coming out real good, it sounds great, and it added a good chunk of HP, enough to easily get the tires spinning into 2nd.   Granted, i have the 16 valve though.

Silver is running a Calmini header, catless into stock size tubing and muffler. The exhaust smell is nasty without the cat and I wouldn't recomend going catless on a ragtop. It seems to work fine, though.

The Green Goblin is running a Hawk header into a 2" high flow cat, 2" Dynomax muffler and 2" tailpipe. The sound is very quiet idling, just as quiet as stock, but a little deeper tone and when I get on it, it gets a little louder than stock, but also deeper tone. Kinda sounds like a good throaty performance ricer sound, not the buzzy fart can style ricer wannabes...