What's suspect on that dyno sheet? Both runs were in 3rd gear...so it is an apples to apples comparison. First time I took my car to the dyno was with the Flowmaster installed, I just wanted to see what the curve looked like. But that run came in handy when I returned with the B&B installed and the speed limiter still in place. It's not like the B&B run was not in 3rd gear.

And yeah...it's not a 30 hp difference, but pretty significant nonetheless especially since my car was stock back then!

Manny

 

No disrespect was meant, but I don't see how these can be taken as solid proof. There was evidently some time gap between runs, so how much of the difference was due to that?

Where both runs corrected to SAE?

All I'm saying is this:

Stock exhaust - - - - Flowmaster - - - - - Any other catback

<----------------------less than 30HP----------------->
...................................<--------------30HP gain--->

On a stock or near stock LS1 going from the factory exhuast to a catback or cutout won't net you 30bhp. So how can going from a better than factory exhaust (FLowmaster) to an alternative net a BIGGER gain?

Logically speaking something isn't right there.

Now I'm not dissing the claim or claiming bs. I totally believe the Flowmaster is a restriction on most LS1's.

But it's too often portrayed that if you have a lid + Flowmaster LS1 you'll gain near to 30rwhp by swapping to another catback. I personally feel this is very misleading.

 

Yes there was some time between the two dyno runs, but no changes were made, the same dyno was used, the conditions were about the same as well.

I agree with you that the more you mod the car, the more of a difference the type of exhaust you have makes, after all, the engine is an air pump, but still, there was a significant difference between for me by swapping out exhausts. Needless to say I am happy with the B&B.

 

i'm switching to something else

 

You realize this thread is almost a year old.

 

thats the first ive heard of a cutout having that much on a magnaflow. magnaflow is one of the best flowing catbacks on the market. i remember several posts of only a 5-10 rwhp difference with the magnaflow vs. cutout.

 

I dont believe it either...

 

Dont believe it...that was my mistake, dont know why I didnt fix that post ....I meant to. It was 12rwhp, not 34rwhp...the 34 gain was tq just before peak tq. Im actually glad someone dug this thread up and reminded me...

 

has anyone done a comparison on a 2 chamber flowmaster/b&b or any other? i bet the difference will amaze you. i had a 95' stang that had a full 2 1/2" flowmaster system with i think 50 series. swapped that out for 3" mandrel bent 40 series with dumps and picked up 21rwhp and almost 15rwlb this was on a bolt on car. maybe its just the 80 series suck, but you cant say all flowmasters do.

brody

 

Where exactly was the cutout put on your car?

 

on my bolt-on M6, i saw 2rwhp/2rwtq gain over my magnaflow with a cutout open

 

Thats a bum post I forgot to correct that I posted about on post #28(I didnt correct it now because it was quoted and I thought I made it clear what was up on it). Sorry again fellas, Ill go back and redo that post.

 

since we are pilling on, i know a heads/cam car that lost 14hp through a hooker vs. cutout

 

Since I posted up way back on this thread, a friend of mine who's a Flowmaster believer installed cut outs on his Y and ran it at the track. I was there and there was NO DIFFERENCE open or closed. This was with Pacesetters and ORY. Believe it or not.

 

Why is it hard to believe? Oxidizr himself said that the Magnaflow catback is restrictive after 400 rwhp. That's why, at the time, they were developing a race catback for f-bodys. I don't know if that's still in the works or not.

All the Magnaflow talk is hearsay. It's no better than Hooker, GMMG, Corsa, either Loudmouth's...on a stock or bolt-on car, they all show about the same exact gains. It's not "one of the best flowing catbacks". It's no different than any other catback out there. The Flowmaster is an exception because it's a crossflow and things get diverted a little. ONLY the 80 series is in question, which is limited to f-bodys. Any other Flowmaster muffler (one or two chamber) will flow fine.

If you want "one of the best flowing catbacks," get a Loudmouth series or a GMMG. They're basically straight pipes. No muffler can outflow them. Magnaflow's good for the price, but I often find it's blown up into this incredible catback simply because it's immensely popular. Because of the price, so many people have it, it's blown up to be way more spectacular than it really is.

 

The actual design really doesn't matter. Fluid dynamics tells us that any muffler that flows as well as an equivalent piece of straight pipe is not going to lose any power. Manufacturers understand this. That's why a Magnaflow, Hooker, etc. makes just as much power as a LM or GMMG.

 

Holy crap this scares me. I dont know what kind of muffler I have. I looked but i dont see any kind of name on it. can someone help me out

 

That's not true. There is a change in medium. How do you think bullet mufflers lower dB? The bullet is made of a different medium. It helps cancel out sound waves. However, air flow, when hitting this medium, WILL SLOW DOWN. A bullet is not a 0 hp loss. There is loss, it's just usually negligible.

As for a magnaflow muffler, have you ever seen the inside of one? It's a straight through pipe peppered with holes. The holes divert sound into the muffler, which is packed with a packing material. Maybe steel wool, I forget. Well, this DOES disrupt flow. It's not a whole lot when compared to a chambered muffler like a Flowmaster, but it will definitely slow things down. Pair that with the split that has to happen - splitting the one inlet into two outlets - and you wind up with horsepower loss due to exhaust velocity being reduced significantly.

It doesn't matter that the Magnaflow is a "straight through" design. Magnaflow's definition of "straight through" is totally different than the "striaght through" found on an SLP Loudmouth catback. Plain and simple, SLP's design is better for flow and will generate more power 100% of the time in an apples to apples environment (same A/F ratio, same conditions, same car, gearing, transmission, etc...). At stock power levels, this is pretty negligible, but get into high horsepower levels and you'll get a much larger horsepower reduction through a Magnaflow muffler than through an SLP LM1. Why? Because horsepower gain and loss IS NOT linear. When the Magnaflow's limit approaches, the gains drop off like a rock. Straight through or not, the Magnaflow is much more restrictive than the SLP LM1 and you will approach the limit much faster.

Same principle with exhaust pipe length. Every foot of exhaust pipe you run will slow exhaust gases down more and more, robbing power. Limit the bends, limit the pipe length. Pipe is not perfect and its surface is full of friction. Flow isn't the only thing that determines a good exhaust setup. "Fluid mechanics" is a bad example because text book diagrams assume models are perfect. Real life is not like this. Real exhaust pipe is coarse and will slow down airflow more and more the larger the distance. Put in any kind of muffler and you slow it even more, regardless what type. Even a bullet will slow things down and cost you some amount of power.

 

Let me try to clarify. The flow capacity of a given exhaust system - including the muffler - must meet the flow requirements of given engine. If that is the case, then the particular design of the muffler is irrelevant. If the engine needs 400cfm and the muffler flows 400cfm, it doesn't matter. This is simple logic.

Just because a system looks closest to straight pipe, doesn't mean it flows better in all circumstances than more conventional looking mufflers. The Hooker Aerochamber is a case in point. At appropriate power levels, its design approaches the efficiency of straight pipe. When the requirements of the engine are greater than its flow capacity, then of course power will drop off.

With that in mind, will a LM or GMMG produce more power 100% of the time than a Hooker or Magnaflow? No. Is there a point in power production where the latter would constitute a greater restriction that the former? Perhaps. It just depends on how much each flows.

Here are a couple of statements from David Vizard: "I am somewhat surprised that it is still commonly believed that building power and reducing noise are mutually exclusive. If we have a 2.5-inch muffler that flows 400 cfm, the engine reacts to this just the same as it would a piece of straight pipe flowing 400 cfm."

The full article is at: http://www.popularhotrodding.com/eng...exh/index.html.

 

I cant wait to get rid of this POS flowmaster and get a borla mouth