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Discussion Starter #1
Just came back from a dyno run. Wanted to see how the car baselined prior to putting in the T/A. Only change from last time (248/292) was welded-in Flowmasters.

Results:

241/282 :mad:

BAD, BAD, FLOWMASTERS! Lost 7/10 at the wheels. Now where can I get some stock takeoffs?
 

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Mr. Bierbelly. When was the last time you dynoed? Different weather conditions? Different gas? The numbers are not THAT far off. You really think the flows are more restrictive than the stockers? Could not this difference be just within some outside variables? I can see it tomorrow: Front page, New York Times: Flowmasters Proven to Lose HP! :eek:
 

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Discussion Starter #4
Ryan L said:
What mufflers were on the car before?
Stock. I thought it felt like I lost something when the flows went on. I did. Runs were on the same dyno, but about 5-6 mos apart. Both SAE corrected.
 

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Hey bierbelly, what's up I just saw this post on stangnet.

And yes, FLOWMASTERS SUCK THE BIG ONE!!!!!!!

Stock all the way for me. :D ;)
 

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What was the temp, humidity, etc the day of each respective dyno??

I am not saying that I don't believe you, because my cobra dyno'd at 265/269 SAE corrected with a 3 angle valve job, an O/R h-pipe, weld in flows, 3.73's, synthetics throughout engine/drivetrain, and a K&N filter. I felt that this was a little lower than it should have been with my mods/setup. Someone suggested that the flowmasters were the culprit, while others say that they couldn't rob too much HP.

FWIW, on turbo stang applications, Flowmasters have been shown to rob about 40rwhp over a straight thru style muffler. I realize that on a turbo that exhaust is everything, but it still applies to N/A applications.... just not as much.
 

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FWIW. Here are my first dyno numbers on my car.

http://www.slosvt.corral.net/images/lloyddyno2.jpg

Mods at the time were, drgas x pipe, magnapack catback, kn filter, and march pullies. I also have an aluminum d/s and 4.30 gears.

My second trip to the dyno @ 4 months later was.

http://www.slosvt.corral.net/images/dyno.jpg

The first pull had the same exact power mods, only at a different time. The only change was I now had on the stock d/s, 4.30 gears, 31 spline axles, and a 31 spline trac loc. Not near enough to warrant a 20rwhp/24rwtq loss. The only way I would trust the dyno is if the pulls are made on the same day. If not I would have thought that the MAF caused me to lose 10hp and 10tq.
 

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I seriously doubt that you lost power from the flowmasters, though I also doubt that you would gain any appreciable power from them as well. There simply isn't much power to be gained/lost in the cat back until you start making more power. There are SO many variables in dyno numbers, ESPECIALLY when they are months apart. SAE correction is not perfect, but rather just a good approximation. I've personally seen many cobras in our cobra club dyno on the same dyno months apart and get different numbers... sometimes better, often worse.

Since there is so little power to be gained in the mufflers, and your numbers are so close, that the variabilty is most likely in the dyno/weather.

The real gains in exhaust are in the stock h-pipe and headers. Get an aftermarket exhaust for sound only.

Paul
 

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Discussion Starter #9
So, you're saying it's probably just within the error/accuracy of the dyno itself? Then, is it OK if I put my best numbers back into my sig, or do I have to be honest?

Yeah, I know there can be changes and inaccuracies. And if you do the numbers, the change is less than 3%, which is probably within the accuracy of the dyno itself. And it was probably more humid today than it was when I had it done last fall, temp not too different. But I'll tell you this, it sure felt like I lost some power right after the flows were put on the car. I sort of expected to lose a little down low, due to the lower back pressure, but figured I'd gain a little up top. Never figured to lose HP AND TQ top to bottom. Now I'm having doubts about opening up to a high flow H pipe (catted). Will it be too little backpressure? Should I stuff my flows full of steel wool?
 

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I wouldn't worry about it. I've never heard of someone who LOST power when they switched from a stock h-pipe to a high flow h-pipe. I had a set of flowmasters welded in and a bbk h-pipe with cats, and I DEFINITELY gained power with the bbk h pipe over the stock pipe.

Paul

bierbelly said:
So, you're saying it's probably just within the error/accuracy of the dyno itself? Then, is it OK if I put my best numbers back into my sig, or do I have to be honest?

Yeah, I know there can be changes and inaccuracies. And if you do the numbers, the change is less than 3%, which is probably within the accuracy of the dyno itself. And it was probably more humid today than it was when I had it done last fall, temp not too different. But I'll tell you this, it sure felt like I lost some power right after the flows were put on the car. I sort of expected to lose a little down low, due to the lower back pressure, but figured I'd gain a little up top. Never figured to lose HP AND TQ top to bottom. Now I'm having doubts about opening up to a high flow H pipe (catted). Will it be too little backpressure? Should I stuff my flows full of steel wool?
 

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Bierbelly,

Don't let the lower numbers be a blow to your ego. Put the higher numbers in your sig and keep smiling. You have a nice, quick ride :):D

I'm personally shocked to hear that you felt a negative SOTP difference with the flowmasters. My car certainly didn't feel any faster when I added them, but the extra sound rumbling from the exhaust pipes did play with my head a little... More sound = more power, doesn't it? :) Wheeeeeee!
 

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Thats why you cant really go by dyno numbers. The best way to tell a gain from a mod is to get a before/after dyno AND most importantly a before/after 1/4 run.
 

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I don't know guys....bierbelly himself said that he felt a loss in power. He just got numbers to confirm his thought.

It's also known that chambered mufflers don't make the power that straight-through mufflers do. He does have a headswap car with 10.5:1 compression and a set of headers. So it very well could be that the flowmasters are a bit of a bottle neck.

If a stock cat-back was put back on and a redyno showed to regain the power...i would just love to see the sh*t eating grins on all the faces of flowmaster owners! :lol:
 

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See, I keep telling you people that FlowMaster SUCKS!!!!!!!!!!!!! Now, maybe some of you will believe me. :p
 

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Mustang92 ran 12s with Flowmasters. I think he recently swapped to Magnaflows and installed a Bullitt intake. He went back to the track and gained .1-.2, but its most likely the gain is from the Bullitt intake alone. I think muffler mods should only be done for sound on n/a cars.
 

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AZsmoothie said:


My car certainly didn't feel any faster when I added them, but the extra sound rumbling from the exhaust pipes did play with my head a little... More sound = more power, doesn't it? :) Wheeeeeee!

THAT'S A RICER COMMENT!!! HAHAHA, Just kiddin!:D I completely agree, I love my flowmasters. I had them welded in first and then did the o/r pipe 1 month later. I really think you guys are on crack if you say you can feel a difference (gain or loss in SOTP) in stock mufflers versus flowmasters (assuming no h pipe or header change) on a mostly stock, normally aspirated 4.6. As far as restrictions go, they are very similar...restrictions are minimal. Now if you changed your H pipe at the same time too and then told me that you felt a SOTP change, I would be more likely to agree. I'm not trying to flame anyone, I'm just thinking that the old mind may be playing tricks on a few of you : ) True, his dyno #'s show differences, but there are MANY factors that could have impacted them, and most of those factors are listed in the above posts.

Good luck guys,
Mike
 

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As far as dyno pulls and 1/4 runs go....which are the best mufflers or catbacks for HP and better times? I've always loved the Flowmaster sound, so I've never paid attention to others.
 

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I dynoed 293RWHP with 2 chamber flowmasters maybe I should put my stock mufflers back on and hope for 300 at the wheels. A 98 cobra dynoed the same day as me. The car had a straight through muffler and basically the same mods. That car dynoed a whopping 1RWHP more than me.
 

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To me, having a car without about 300 horsepower, it would be pretty hard to distinguish the gain or loss of 7 horsepower, when driving it on the street. You MIGHT see a difference on the track, but what if the air, or altitude of the track is different from the last one that you ran on. Then would you notice??? Probably not.

Dyno's are just a good way of approximation. The track is always the best way to tell where the car is at. And I really doubt you would have seen any difference at the track. JMHO....
 
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