Exhaust

I am currently ordering all the parts for my dual exhaust set up. I have ordered 2 dyno max muffers high flow welded(which allow the most airflow thru); 2 BMW schitner exhaust tips and I need some info on a cat. I was looking on buying 2 Random cats. The sight and the company seems like they have a good rep. Has any heard or has these I want to know what they are about. They are $280 pricey a piece. Or help refer me to better converters. Also planned on running 3" pipe. Is this bad or good or go with 2 7/8"?

This is my first post. 97 Red SVX

[mbtoloczko]

Need more info about your exhaust to give advice. Dual pipes from the manifold back? Cat back?

yeah replacing the cats and dual the rest of the way back(no res)

[svxfiles]

If you are going with true duals, then 3" is WAY too big!
, unless you have other mods, like NOX, turbo, supercharger, stay with 2" id MAX for true duals, and 2.5" id max for a single. You will lose a lot of bottom end if you don't. Tom

[Chiketkd]

Originally posted by svxfiles
If you are going with true duals, then 3" is WAY too big!
, unless you have other mods, like NOX, turbo, supercharger, stay with 2" id MAX for true duals, and 2.5" id max for a single. You will lose a lot of bottom end if you don't. Tom

Agreed. For a dual set-up, 3" is way too big. Some big block muscle car guys use dual set-ups with that size piping. For our 'smaller' 3.3L engines, that would be over kill unless going to forced induction...

-Chike

[Motorsport-SVX]

to be honest, Random Technology cats never sold
that well, the best cat for your $ is to buy Carrsound
cats (dist thru Magnaflow too )
The LS1 club in Tx did dyno testing various cats last yr
and Carrsound came out on top.

I agree that 3" is too big.

For the SVX I think 2 - 2.5" is the best for keeping the weight down, better clearance and for scavenging exhaust gases by maintaining an ideal exhaust flow velocity.

BTW, has anyone tried the Moroso Spiral, Edelbrock Tru-flow and Hooker Header Aerochamber mufflers?

[mbtoloczko]

Might sound a bit too extreme, but the more I read about exhaust systems, the more I convince myself that the primary pipes could be kept as small as 1.5" OD for best all-around performance. For dual exhaust, step up to 2.25" OD at around 35-55" from the exhaust manifold.

motorsport ty for the tip on the random cats that can save me alot of money on this project. I want max proformance but I want a truely aggressive sound. What if I went with a 3" inlet and a 3" outlet on the cats (to open the resticted flow more) to a 2 1/2 pipes back to the mufflers.(Dynomax ultra flow welded) Then 3"into mufflers and out to tips. Would that be ok to go from 3" to 2 1/2 to 3" and out? I figure the bigger the pipes the deeper the sound. Or use 3" to 2 3/4 to 3" or not. I know you all suggested smaller I just want to here alot of different opinions. 97 red in the beginning stages (off the record it has been -50 for 6 days strait.)

[NapaBavarian]

As I recall someone went to duals before and said it sounded whiney and ricey, basically turns it into t 1.65L engines so you might want to find out what the outcome has been from previous people.

[SVXRide]

Does Alaska have yearly emission inspections? You might want to consider just running a single high flow cat (I got a Magnaflow piece from Dayle's shop) around 60-70 inches back from the engine. Since I'm reading the same theoretical info as Mychailo ( ), I'd also recommend keeping the size of your primary pipes small in order to keep your engine's bottom end performance (see Tom's comment above). The Subaru engineers did a good job with the exhaust manifolds and you can basically look at the engine almost as two 3 cylinder engines. You might want to consider going with primary pipes of around 1.5 inches I.D. feeding into a Magnaflow high flow cat with 3 inch inlet and outlet (the cat would serve as your expansion chamber) and then running 3 inch pipe back to the tips you want.
-Bill

[wawazat??]

Originally posted by mbtoloczko
...but the more I read about exhaust systems, the more I convince myself that the primary pipes could be kept as small as 1.5" OD for best all-around performance.

Scientific Desing of Intake and Exhaust Systems??

New Christmas book Mychailo?

Todd

[mbtoloczko]

Originally posted by wawazat??


Scientific Desing of Intake and Exhaust Systems??

New Christmas book Mychailo?

Todd

Yeah, that was some good bedtime reading. :-) I thought I had it all figured out after I read that book. Then I stumbled across this article:

http://www.cafefoundation.org/aprs/EPG%20PART%20IV.pdf

Seems to suggest that mass velocity is far more effective than sonic reflections at generating a vacuum at the exhaust valve in the latter part of the exhaust stroke. Unfortunately, the article doesn't go into enough depth to get sufficient info to accurately apply the concepts to the SVX.

[SVXRide]

Todd,
1. Smith & Morrison - Gods of Exhaust Design!
2. Aren't you supposed to be on vacation?

Mychailo,
Think we should start welding up an R&D exhaust with "blind legs"?
Did you catch the "...single most effective way to increase the Subaru horsepower output..." comment in the article?
I've got to read the article a couple more times - I'm still wrestling with the tuning for sea level and tuning for 8-12k feet of altitude info presented (as I really don't have any desire to yank the engine out of my car and put it into a plane )

-Bill (ready to weld up an R&D "chamber/muffler", just waiting for the signal....)