Where is it on the SC400? Trying to decide if its worth going with a cat-back exhaust system, or just the muffler from RMM. Most bang for the buck assesment. Any feedback would be appreciated. Thx.

 

I did the cat back oin my sc4. Not sure about performance because I have not gone back to the track yet, but it is louder. It sounds like im driving a boat now. There may be some power gained somewhere because I can chirp my tires off the line after installing the cat back. Its the do luck one. pics posted in the forum.

check out peter scotts bigpond diehard soarer page. He has some graphs of power gains after headers and exhaust mods.

 

Backpressure is concentrated at the front end of the system. Replacing just the mufflers won't gain much, its the piping right after the cats that has the greatest restriction.

 

Has anyone here tried a custom true dual exhaust system here? I'm talkin' about dual cats with an X or H-pipe instead of two Y-pipes and a single cat. I'm particularly interested in anyone that has done so and passed smog in California. That's a move I'm about to make...

Here's Peter Scott's exhaust article, BTW...

http://www.users.bigpond.com/pgscott...asurements.htm

 

I'm designing one right now with a company called Magic Touch Designs (they deal w/ exotics, mainly the plymouth Prowler), but I live in FL and the emisions are different here. All the testing should be done by the end of November, and I should have the final system tweaked by Christmas.

Keith

 

FYI, on the SC4, there are 2 cats from the factory tucked up near the manifold, the "y" pipe goes to a front muffler/resonator, then "y's" back out to the rear resonators.

Stock : 2 cats, 3 resonators, 2 rear main mufflers

 

Well technically there are three cats, but the two on the down pipes don't do much so I'm not that concerned with them.

 

Hey keith were in orlando? I'm going to UCF right now. Are you or that company anywhere close to UCF? I'm thinking we should REALLY get a SC meet in orlando. I've seen A LOT of SC owners in orlando or close to orlando. It would be nice to get together for a lil bit.

 

Japanese spec exhaust is very quiet compared to the US spec exhaust - your standard rear mufflers would outflow my standard mufflers by miles.
Best bang for you buck would have be to leave the rear mufflers alone , leave the front section alone , and replace the middle mufflers and centre cat/resonator with custom straight through pipe and some sort of balance pipe - be that Nascar style x-pipe or the longer type as seen on V8 Supercars.
I went for the x-pipe in the end.
My current V8 exhaust

 

I'm actually right near UCF . Actually graduated from there years ago myself.....took me 7 years but at least I graduated w/ 2 degrees... you know what they normally call people who have been in college for 7 years ...Doctors (am I ; no). You know what UCF stands for - "U cant finish!!. On a side note, I'm off Dean and University; and Titan Motorsports is on Goldenrod between 50 and University (closer to 50). I've counted about 5 people on this forum from O-Town, but several attempts to get a "Club meet" together have failed. We do need to get some people together and maybe just watch a game or go cruising or something. Maybe a track night at Bithlo to see who has the fastest Orlando SC!

One of these days......

 

yo keith I'm ike a mile from you. I'm right off 50 and econ. I'm right down the street from valencia comm. college. I'm tellin you we HAVE to get a orlando SC meet. It would be so awesome. We really need to race our SCs. I'd be in last place but it still would be fun as hell. I live in a house right now so we can probably meet here for awhile and hit the tracks. We should get something started. It would really be awesome.

 

Peter, this is the first I have heard of a Japanese vs. USA spec exhaust. Have you ever heard a USA spec SC400 or LS400? Whisper quiet. The mufflers on the 1990-1994 LS400s and the SC300-400s look identical to each other. I realize looks are not definitive but the USA cars are VERY quiet. My 99 LS400 has the exact same exhaust EXACT as the 1995-2000 LS400s. Completely quiet. I can't imagine it being quieter.

The exhaust diagram you show in on your website is from an 95-2000 LS400. The mid muffler/resonators on a SC have the cans perpendicular to the road and the LS has them parallel. Each has the unique side entry and end exit. The LS also has the short 2.5" (60mm) cut and spliced outlets from the cats. I will post pics of mine when I get the chance.

You may also note that I am currently running without rear mufflers and although the center mufflers still keep things very quiet there was a 1 mph increase in trap speed in the 1/4 mile. I agree with you that the stock cats flow well and the center section of the exhaust is the most restrictive but I doubt the USA rear mufflers would flow well enough to allow an upgraded center section to make its full potential.

 

lex400sc, actually there are only 2 cats. The center section is a straight through resonator. If you remove the 2 cats from the downpipes you will have NO cats.

One of the biggest problems of emission control is the levels at cold start. The engine is running rich and the cats are not up to operating temperature. If you move the cats they will take longer to heat and therefore catalyze the gasses. The larger a cat is the longer it takes to heat. The stock cats flow well. The stock manifolds suck. Very few good options exist for replacing the stock manifolds requires. Peter show a very nice system but even though it would pass a sniffer when heated it is not technically emissions legal and would fail a visual inspection. Short of replacing the stock manifolds your best bet is to leave the cats as they are and build a high flow system from there.

 

Does the whisper quiet apply to SC300's as well? Mine has a drone that is not pleasant, not like a well-tuned aftermarket. It looks all stock and I am pretty sure it is. But it is not whisper quiet.

 

My SC400 wasn't whisper quiet when I got on it. It was about as loud as a stock Z28 actually.

JBrady, so you're saying the third cat is not legally considered a cat at all? So if I had it removed and smogged, then my car would pass inspection? I had the outlet of the "third cat" cut off and saw an intricate layer of honeycomb mesh inside. To the best of my knowledge, that's what a catalytic convertor has inside as well.