slowfive0

Sounds like a nice combo. That is probably the big difference between my flowmaster combo and most others out there. I have (2) mufflers and they are both huge. 22" long to be exact. Also 3". I think most guys that have tried the flowmaster have used the dual in/dual out or a big single style muffler.

[QUOTE=joeyc125;4587434]I ran a 12.87 with a SINGLE flowmaster 40 series
single in single out. This was definitely not the best combination for the truck, but its what I had on it when I put the blower on. This was in my crew cab z71 LT full interior, approx. 5800lbs stock 6.0 with a 215 224 114 isky cam and small obx headers. I have since went to dual 2.5" super 40's that are decently quiet, no drone at all, and have the flowmaster sound that I really like. When I still had the blower, it felt quite a bit stronger after going from single 3" in with the stock exhaust piping to the dual 2.5". I would say it would have picked up a tenth or two. This was all on 6psi, really woke up at 8psi, probably in line with your times at 8psi.[/QUOTE

What is your exhaust/combo? Did you just drop the exhaust and picked up .23? That's amazing! I'm going to drop mine in the spring and see what difference it makes. Hell, if I picked up .23 I'd already have my 11 second 1/4 mile time!!!! Whoo Hoo!!!

mhotrodscooter

iTrader: (13)

.[/QUOTEWhat is your exhaust/combo? Did you just drop the exhaust and picked up .23? That's amazing! I'm going to drop mine in the spring and see what difference it makes. Hell, if I picked up .23 I'd already have my 11 second 1/4 mile time!!!! Whoo Hoo!!! [/QUOTE]

It's a dual in/out big block series. I've got 2.5 going in & 3" coming out y'd into a single 4" tailpipe.. Yep basically I got under the truck & unbolted the exhaust and moved it over, .23 & 2 mph faster with open exhaust.

old motorhead

iTrader: (10)

I had dual 3" exhaust from the headers back leading to an x pipe then to dual 3" in/out flowmasters. I went as far as measuring back pressure in front of the mufflers. It had 4psi of back pressure from about 4000 rpm on up. They were loud as hell too. I changed them out for a pair of magnaflows. They were a little quieter and I'm assuming they flow better too. You can see straight through them. If I remember right, this was with a 6.0L and MP112 blower. I didn't measure much difference in boost or power. I think with a bigger blower, there would have been a pretty good power diff.

slowfive0

Nice!!! I would be extremely happy to pick up two tenths that easy. I will defintely drop my exhaust in the spring and post up the difference. For that matter, I'll even drop it in two places (before cats and after the x-pipe but before the mufflers.

Interesting. Did you run it at the track before and after the muffler change? There is no disputing that a straight thru muffler design will flow better, but Flowmaster claims that their mufflers can actually assist with scavenging hence making some better power. I'm definitely going to do some more testing in the spring. I'm on the fence, but as long as the loss isn't more then 2 tenths, I'm cool with keeping them (love that sound).

old motorhead

iTrader: (10)

Didn't run it at the track. I can't see where there's ANY scavenging with 4psi of back pressure. Maybe on a low power n/a build with little or no back pressure. I would think 4psi is a pretty big amount. I might be able to simiulate that now by putting a tennis ball in one side (have X pipe)

slowfive0

I'm no engineer but your logic makes sense. I guess we'll find out next year. I'm curious about my backpressure now-lol!

2ktransam

iTrader: (12)

I used to have a Flowmaster on my TA. It lost 38RWHP running through the muffler vs the cutout. I took it off and put a Magnaflow on and it sounds close to the same and it picked the power back up.

slowfive0

Was that the transverse mounted muffler behind the rear axle?

jiar577

iTrader: (2)

Damn, I've read long ago about Flowmaster loosing power but that's a lot!!

Holty

iTrader: (6)

I used to run dual flowmaster 40 series. Best 1/4 time is 12.14 @ 111mph - I switched to Magnaflow race mufflers but have not ran it since. I don't feel any difference in power though. I liked the flows sounded better.