XLR8

iTrader: (52)

I will be putting a 2.5" exhaust on my SE. I have a RB uncollected header. Here's my plans:

Run 2" duels from the header to the axel and go 2.5" to the muffler from there. I will be using some RB flanges to seperate the 2" duels, in case I need to pull it off(ieTII tranny coming soon). I found the u-bends and collector at summit for a reasonable price. I'm pretty sure I have to go over the axel. I know quite a few of you guys built customs for your TII swaps. Any advice? Tips? Things to do or not to do? All help is aprecciated.

Thanks

web777

Are you putting a TII engine in your car?

NanaimoRx-7

Bigger.

XLR8

iTrader: (52)

I will be keeping the 84 6port. It will be rebuilt eventually.

My motor has excellent compression as is and I won't be running but 6-7lbs initially. 84 6-port engines had the heaviest rotors which is good in my case. Slower reving, but more torque and it would be better for SC's power band. I have read the Atkins is a solid unit but like a SC, it boosts quick and doesn't build much after 6-7k. 9.4 compression, .4 higher then FD's and 89-92 TII engines. 84 engines also have 3mm apex seals OEM. 6port sleeves will be removed. Porting to the rebuild

NanaimoRx-7:
Its funny you say "bigger" I was thinking 3" initially but thought 2.5" would be fine...........your right, I know better

So....about the exhaust... Any advice? Tips? Things to do or not to do? All help is aprecciated.

rotarygod

iTrader: (1)

If you are running a positive displacement supercharger then all that you know about exhaust design gets thrown out the door. There is no need for a good scavenging exhaust because the exhaust no longer scavenges. A supercharged engine just needs to be concerned with getting the air out as fast as it can so go as big as you dare. You will come to a point though where bigger isn't doing anything else.

Just to rebut any arguments ahead of time about the nonimportance of a scavenging exhaust on a supercharged engine, ponder this... If a scavenging exhaust were important for good supercharged power, why don't blown top fuel dragsters collect the exhaust while the nonsupercharged top fuelers do?

Just remember that the larger the exhaust, the harder it is to quiet it down.

fatboy7

Its not that scavenging (ie pressure tuning) doesn't do anything, because it still does, but letting the gases escape as quickly as possible is more important, thus that is why top dragsters keep the runners short, and don't collect. The runners still have a tuned length though.

As far as a custom exhaust goes, keep it as simple as possible. Rember that turbos act like a small muffler, so I'd expect a sc with 3" to be louder than a turbo counterpart. You definately will want good presilencers on the uncollected runners. I'm not sure I'd go 3" or not on a SC. Turbos are much more sensitive to backpressure than a SC is. You are flowing alot more, so... I don't know.

XLR8

iTrader: (52)

SOOOOOoooooo, I don't need to collect it? I have heard of some NA racers running uncollected duels. I understand the scanvenging. So in all actuallity duel side pipes would be the best. I know I can't run side pipes, open header, or anything like that. If uncollected Duels would work better it would be more work, weight and cost but I want to do things right the first time.
I'm really up for opinions here??????????????????????

Fatboy7:
I am not concerned with it being too loud It is a street car though. Me and the big redneck trucks have a little competition going They love my bike.

Thanks guys

kuhlrx7

your first idea is good but I would collect at the rear muffler and it would be collected into 3 inch not 2.5 or a two in two out x type design muffler or one of the y designs installed reverse. two out uncollected = very loud and many tickets.

rotarygod

iTrader: (1)

The collected at the rear design is still my favorite as well.

XLR8

iTrader: (52)

Alot of the reason I opted for the 2.5" is my straight through muffler has a this size inlet. Didn't want to create a funnel type system.?.?. Would 3" still be better even though my muffler inlet is 2.5"?

Thanks guys

XLR8

iTrader: (52)

I've thought about it and this is my result: 2 2" pipes uncollected from a header flange to a 3" collector collecting at the rear to a 3" straight through muffler. I will have to buy another muffler which sucks because mine sounds great.
Hows that sound?

thanks

rotarygod

iTrader: (1)

The 2 1/2" will work just fine. Whether or not the 3" works better for you is another story. If your engine is not ported then the 2 1/2" will be just fine. The long primary system from Racing Beat uses a 2 1/2" collector and it works beautifully. The 3" is going to be much louder. If I were going to do a 3" then I would collect it at a 2 1/2" and then use a megaphone attached to the header to transition it to 3" immediately after collecting. I wouldn't just use a 3" collector. Try the 2 1/2" for the time being. I bet you'll like it. If you only do one and not the other, you'll never know which one would have been better. As a general rule always lean to the small side when you aren't sure. When you supercharge it, the just swap out the back section of exhaust.