James Bailey

Correct a single somewhat loud exhaust has a smoother sound which is similar to the Ferrari flat crank v-8 sound and seems like it is at higher RPMs. A much more European sound rather than the "Damn the mufflers fell off the 69 Chev pickup again...." but to each his own

hopwood

The sound of a single pipe is in my view superior. It is somehow a more 'resolved' sound, I wouldn't say it sounds anything like a flat plane crank V8 (thank god, they don't sound like V8s at all to me) I'd say it does share some character with the recent AMG V8s, which is a good thing.

Joel
79 4.7 with Y pipe and 3" single

Iwanna928

To me it would come down to a buget that I had in mind. First I would start with headers. Then if I had it in my buget I would go X pipe or Y to true duals. Others wise a Y into a single. That would no doubt be cheaper and easier to install.

I have duels with headers. It sounds very nice in my opinion and I get compliments ALL the time on the way she sounds.

I had no cats(took them out) and it was just to loud. Fun at first and then it became annoying. I put in a glass pack in its place(18 inches) and 2 dynomax bullets at the back end. Know I can hear myself think, talk on the phone and listen to my stereo. But when I get on it she starts to roar!

Stephen

rgs944

I was going back over my old threads and noticed this one was never completed with the end result. Someone might be able to use it for future reference. I do not know if I gained any HP but it is definetly a lot lighter system and I think it sounds amazing. My total project cost came to well under $500. It is a well made x-pipe I found on Ebay going into a flowmaster Y collector and 3 in. single back to a flowmaster 40. I purchased an entire mandrel bent kit from flowmaster that gave me all the angles and bends I needed. The flowmaster 40 sits in the spot of the original driver side resonator. It looks like it belongs there. Below is a link to hear it.

z driver 88t

One thing to keep in mind on Ott's website is that the 3-inch exhaust comes off 2.25 inch pipes. All the others come off a 2.5 inch pipes so it's not clear if the 10HP loss is a restiction caused by the 2.25 or the 3-inch or a combination.

In comparing the graphs in the lower RPM range I'm inclined to think the 2.25 inch is dominating the power loss or at the least is a significant contributor.

SMTCapeCod

Props for closing the loop! I wish the forum tracked when threads are opened and required the O/P to tick a 'closed' box or something- short of locking the thread.

I hate it when protracted searching/clicking finally yields that spot-on thread...that evaporates and turns into a cliffhanger when the participants & O/P meander off before the problem is resolved.

Mongo

I don't really think there is a loss on collecting to a 3" after cats on a stock S4. I can understand if it is supercharged, which would require a 3.5" single exhaust most likely; incredibly difficult to muffle on a street car.

The result of keeping a 3" single after the cats on a 32v would probably bump up the torque as the exhaust gasses are still hot and compressed. Probably the best way to ensure no loss of HP is to have a straight through 3" single pipe exhaust after the cats using a Magnaflow muffler. A Flowmaster can be utilized though, but it's optimal location would be at the back of the car rather than where intermediate mufflers are. RGS, sorry, I am not trying to say your location is poor. I believe that as the exhaust cools toward the exit at the rear, using a multi-chamber muffler like a Flowaster 40 would still maintain the heat in the gas passing out the tail pipe to maintain performance if not gain more HP and torque. That being said, a 3" single pipe does gain in torque and HP over the stock setup, which I believe is closer to 2 1/8" rather than 2.25".

rgs944

I might look at shifting the flowmaster further back someday. The reason I chose the location is that I was not sure if the 40 was going to be enough. So I left the option open of putting something else behind it. Overall I am very happy with it. My priorities were sound, sheding weight and keeping the price low. If I gained HP that is great, and is'nt the easiest and cheapest way to gain performance is if you just lose some weight? The car feels nice and is plenty fast enought to have a lot of fun, or get into a lot of trouble. I guess it all depends how you look at it. I would like to hear some feedback on the sound from you guys. I think it sounds great but I guess I am not a very objective observer.

Mongo

My change over will include a straight through muffler made by Jones Exhaust called the Max Flow. It is a Magnaflow knock-off. I will also have a glasspack that is 22" long in the intermediate area to really tone down the drone since I will be swapping my cats in and out. The x-pipe in the front is going bye bye in favor of the after cats merge.

Speedtoys

Here is my dyno chart with stock headers, into shortie cats, a burns stainless 2.5-->3" collector, 3" to flowmaster 3 chamber, to 3-->2.5" spliter for dual tips.



Mods other than exhaust...umm..very old mouse nest stuffed OEM style air filter....bout it.


Automatic 88 S4.

928mac

Hmmm not much gain eh Speedtoys.

All I did to mine was to remove the cats and install an H-pipe.
I did make sure that the H cleared the bell-housing as having to drop exhaust to remove the cover really ticked me off.
I like the sound and you can hear it if you click the tire smoke link in my sig.

Mongo

Lose the Flowmaster in the intermediate area or relocate it to the rear. It is slowing the exhaust down too much at that location. Other than that a factory S4 dynos 270 to the rear and an 8hp gain is not a bad thing!

heinrich

Rick posted the definitive 928 exhaust information available. Basically Louie Ott's research proves that:

intake and exhaust resonance need to work together
separate pipes make less power than a single pipe
simple single pipes make less power than separate pipes with an X or H
back pressure is a factor when there's no X or H
bigger pipes do not necessarily make more torque or power, in fact they can make a lot less
3" appears to be the best

LEADASS

I'm curious, what are your thoughts of the same on a super charged car? I'm trying to figure the best setup for my car. I've got some headers with a header x-pipe and a pair of hi-flow cats, what to do the rest of the way back? I'd love to hear your input before I put anymore cash into it. Noone makes a dual setup for the 86' cars so I'll have fab it all anyway. Thanks, Brian

heinrich

Forced air is entirely different. Your goal there is to push air volume into the motor. When it exits, I'm not clear that anything but "get the gases the hell out" is the goal. Tim Murphy is your expert there.