gnx7

iTrader: (28)

I plan to have about 425-450rwhp in my 2900lb (with driver) LS1 powered RX-7 M6 3:90's. I am very weight conscious and trying to shave off unneeded poundage from the car....

Here is my combo:
'98 23K mile shortblock, home ported 5.3's (2.02 valves, 5 angle VJ), TSP 233/239 112LSA cam, LS6 intake, ported stock TB, 1 3/4" LT headers, March pulley, no a/c....

I do plan to shoot a 150hp NOS shot at the drag strip...But the car is mainly a daily driver and 1x/month road race car (main intention).

Dual 3" with Xpipe will produce more upper end power.... and a single 4" will produce more low end torque with a sacrifice of upper power I've been led to believe. Not sure what is right though. I know LG Motorsports prefers the duals with Xpipe and he loves all around torque.

Any thoughts would be great. I think with a single exhaust I could shed an easy 25lbs vs. going dual with an X-pipe. However I'd rather have more power as 25lbs is only a few extra hp to negate it.

Also what is is the quiestest muffler that still makes great power. I was thinking of putting on an Ultraflo or some other straight thru type Dynomax muffler. I've had good experience with their produces on my GN powered RX-7's.

Thanks,

-Mark

LS1BirdDRG

My friend has a Datsun 260Z w/ smallblock. He's not making the power you'll be making but he has a 3" y-pipe setup and I know his car would sound alot better with duals. Sound means alot to me, even if it's alittle heavier. Although, I'm not sure what 4" would be like. Sorry, I guess I'm not much help but I do know I gained alot on the top end when I went to duals and didn't seem to lose any low end.

gnx7

iTrader: (28)

anyone else have some insight?

-Mark

jrp

iTrader: (16)

whats the clearance like on the RX7? also do you mean 3" off headers into a 3" Y expanded to a 4" catback?

i think your getting a little carried away, even a 2.5" dual exhaust setup should support the power you need. 3" is better and 4" is overkill.

5POINT7

I think a 3" x pipe setup will do you fine. I wouldn't go 4" with stock cubes.

As far as quiet mufflers...Magnaflow 4x9 or Borla XR-1 hands down. Both are quiet.

gnx7

iTrader: (28)

I'll probably just do dual 3" with an Xpipe the whole way. I've used the Ultraflos... but I'm sure the the normal Magnaflo is a bit quieter.

jrp- I was meaning dual 3" off the headers, into a 3x3x4" "Y" and then single 4" out to the back.

The clearance is pretty good on the RX-7 for duals. The driveshaft is tucked up nice and high in the tunnel.

-GNX7

Mooobunnny

iTrader: (1)

With a good x-pipe you should pick up more everywhere over the 3 inch to 4 inch system IMO....