Im running two 40 series with factory y & tail pipe and the truck runs a lot better. I've always had flows and always will.

 

I have the super 44. With a few runs by seat of the pants plus my own attemt at 0-60 it gave 2-3 thenths.

I used a stop watch so it is only ball-park, but I have 3.23's which probily makes more of difference then it would with 4.11's.

 

I just switched to a dual set-up with the Borla XR-1 mufflers and it blows away the flowmaster performance wise and especially sound wise.

 

flows are better than stock, but worse than any other aftermarket muffler. i've ran them on several trucks because i love the sound. you swap to another muffler and a difference can be felt. if you worry about a couple hp than run a good flowing muffler. if you like the sound of flows, than run them. i will going back to dyno next month w/ only a muffler swap.

 

Read the article I posted so you quit looking like noobs. lol.

There are tons of different versions of Flowmasters. Some flow 250cfm others I'm sure flow over 1000. Guys on tech have ran single chamber Flows on the dyno, unbolted and ran again and gain 2rwhp on heads & cam cars. As said, some are for people to toss on for sound, others are for race applications. People on here toss regular flowmasters on supercharged/turbo/heads/cam applications and wonder why the muffler can't keep up.

 

all mufflers give you some back-pressure which you need to have( most of the time you run you engine) when you on the street. They will be more restrictive than opn cut-outs, of course but they are designed to do so. now as far as how much back-pressure... flomaster has very little back-pressure, about the same as lets say, a glasspack. Stock mufflers are very restrictive. Any less-restrictive muffler will raise your hp / torque, if you get the right set-up. I would however get a set of cut-outs, if you want to run open headers at the track, it would be fine.

 

anyone here using a resonator box as descibed in the article?

 

I run 50 series 4"in 4" out and the sound is very mean.Full throttle is second to none imo.
I switched from 4" in 4" out magnaflow.The truck didn't lose anything and actually gained more down low under light throttle.
If I get a chance to post sound clip I will.

 

hence the name ROBMASTERS....

 

Considering that I personally know two individuals running race series Flows on their 9 second cars at MIR (406cid Vega and 408cid Mustang) I think that this Flowmaster bashing is unwarranted.

It started with the F-body crowd due to the less than optimal design of the cross flow style catback. Now the in thing to do is bash the brand and state hearsay as fact.

If members of the NMRA can run their Mustangs into the 8 second zone and beyond with a pair of Flows what keeps the LS people from being able to do the same?

It's about what size, series, and overall exhaust design that you have that dictates how your truck will perform.

Go on LS1tech and see how many Heads/Cam cars have Flowmaster style 3" I/O diameter mufflers on their true dual setups and lay down over 420 RWHP.