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Have you ever even looked at the design of the stock mufflers???

Face it, there simply isn't much power in the cat-back (particular if you just swap out mufflers), unless you've "got a bannana in your tailpipe"

I can't believe that you think that the flowmasters are a "bottleneck" compared to the stock mufflers.

Go ahead and post your best numbers; ultimately they are just that, numbers. Furthermore, (and I'm not suggesting that you didn't) but did you compare your ENTIRE hp/torque, and not *JUST* the peak numbers? Peak numbers are like relatively meaningless to begin with.

-Paul

97MattGT said:
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:
:confused:
 

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Discussion Starter #22
Bright Blue Cobra said:
Have you ever even looked at the design of the stock mufflers???

Face it, there simply isn't much power in the cat-back (particular if you just swap out mufflers), unless you've "got a bannana in your tailpipe"

I can't believe that you think that the flowmasters are a "bottleneck" compared to the stock mufflers.

Go ahead and post your best numbers; ultimately they are just that, numbers. Furthermore, (and I'm not suggesting that you didn't) but did you compare your ENTIRE hp/torque, and not *JUST* the peak numbers? Peak numbers are like relatively meaningless to begin with.

-Paul

:confused:
In reverse order, no, just the peak numbers. I wanted to compare the old and new runs throughout the entire range, but I hadn't gotten an electronic copy before. This time, I brought a floppy, but the dyno place had their computer crash sometime between then and now, so my old data is lost, unless I can find the sheet they printed out for me before.

I'm not suggesting that the Flowmasters are MORE restrictive than stock, but that perhaps the stock system is better balanced wrt backpressure, and that if you put less restrictive mufflers into the system, you actually lose power. Is it POSSIBLE that FORD had it right from the git-go?
 

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Is it POSSIBLE that FORD had it right from the git-go?
I will let you know when I get back from the track.
 

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bierbelly said:


Is it POSSIBLE that FORD had it right from the git-go?
I would think that my sig shows the answer. Having a reasonable amount of backpressure will keep cylinder pressure from bleeding down during the overlap cycle. During valve overlap, if the pressure in the exhaust is less than the pressure in the intake manifold, the fresh air and fuel will come right in thru the intake valve, and fly right back out through the exhaust valve. There goes valuable cylinder pressure/air volume. Those of you that think the idea of backpressure helping power is a myth, keep on telling yourself that.:rolleyes:
 

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Discussion Starter #25
32VHEMIJR said:

I would think that my sig shows the answer. Having a reasonable amount of backpressure will keep cylinder pressure from bleeding down during the overlap cycle. During valve overlap, if the pressure in the exhaust is less than the pressure in the intake manifold, the fresh air and fuel will come right in thru the intake valve, and fly right back out through the exhaust valve. There goes valuable cylinder pressure/air volume. Those of you that think the idea of backpressure helping power is a myth, keep on telling yourself that.:rolleyes:
So, do you think that the Flows caused a greater reduction in BP than would changing out the cats? I see you've got an O/R pipe matched with stock muffs. Or is there a relationship as to WHERE the BP is located, such that it's OK back at the muffs, but detrimental in the crossover pipe?
 

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I think an unrestrictive setup before the CB is good. You need some unrestrictive length to take advantage of the resonant frequency tuning of the pulses coming out the primaries. I do have a feeling that the flowmasters flow plenty. Maybe they flow too well for your setup....who knows?
 

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Discussion Starter #27
32VHEMIJR said:
I think an unrestrictive setup before the CB is good. You need some unrestrictive length to take advantage of the resonant frequency tuning of the pulses coming out the primaries. I do have a feeling that the flowmasters flow plenty. Maybe they flow too well for your setup....who knows?
Well, that was my question! Maybe I'd be better off with a high flow cat and a stock cat back. Maybe the Flows are reducing the backpressure too much. And finally...WHO does know?:confused:
 

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bierbelly said:


Well, that was my question!
Relax pal. I'm trying to help:mad:
 

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Discussion Starter #29
32VHEMIJR said:

Relax pal. I'm trying to help:mad:
I know, and I'm agreeing with your suggetion that some back pressure is a good thing. Don't take me wrong. I wan't flaming or anything. A good experiment would be to get those tunable mufflers (can't remember the name of them, but they're readily available for motorcycles, and I understand they're now made for cars), and dyno-tune the back pressure of the mufflers to optimize. Obviously, it would be different depending on other mods. MM&FF, where are you when we need you?

The reason I posted at all was to inform our brethren that low restriction exhausts ain't necessarily always the best way to go, and in fact can be detrimental.

Sorry if you took me wrong.:eek:
 

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As far as a high flow cat-back goes, most people find some gains from a good one. For example, goto Magnaflow's web site and they tested a stock 99+GT on the dyno and then slapped the cat-back on for some decent gains. Look at the dyno chart they have. It shows some gains across the band. Someone on Stangnet posted their dyno results about 2 weeks ago before and after the Magnaflow cat-back and got some decent gains. They were not as lofty as the Magnaflow dynos though.

Bierbelly, one thing to consider is that your cat-back is probably a 2.25 inch and the Flowmaster muffler is probably a 2.5 inch with an adapter pipe there. Maybe could be something going on with that???
 

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bierbelly said:


I know, and I'm agreeing with your suggetion that some back pressure is a good thing. Don't take me wrong. I wan't flaming or anything. A good experiment would be to get those tunable mufflers (can't remember the name of them, but they're readily available for motorcycles, and I understand they're now made for cars), and dyno-tune the back pressure of the mufflers to optimize. Obviously, it would be different depending on other mods. MM&FF, where are you when we need you?

The reason I posted at all was to inform our brethren that low restriction exhausts ain't necessarily always the best way to go, and in fact can be detrimental.

Sorry if you took me wrong.:eek:
No harm no foul. I think the muffs you're thinking about are supertrapps. I've heard them on other cars and they sound like ass. I dont know what they would sound like on a stang.
 

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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.
:) no , I'm not somking crack buddy. But when I had the swap done, going home I floored it getting on the highway and the car did seem a tad stronger. to me it just makes sense for a 2 1/2, 2 chamber muffler to be less restrictive than the factory 2 1/4 inch.
 

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Discussion Starter #33
OK, went home yesterday and compared the old dyno graph to the new one. Virtually no difference in HP and TQ down low, say up to about 3600 rpm. Only diff was near the top in peak HP and TQ.

Did a little research on the net. Found a ricer site (NSX) where the guy said that Flowmasters were even more restrictive than stock (obvoiusly for their cars). Also found a biker site where they did some dyno runs on a Harley with straight pipes. They placed a variable restrictor (a washer connected to a bolt) in the exhaust stream. They found a noticable hole in the power when the washer was parallel to the flow stream, but the hole levelled out when the washer was turned into the flow stream. Intermediate results when the washer was turned 45degrees to the stream. So SOME restriction is better than none. But what does that say about the Flows? Too restrictive? Hmmmmm....:confused:
 

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I THINK that when MM&FF had just started building up superfly, The first mod that they did was weld in 2 chamber flowmaster and lost 3hp (same day and dyno). They ended up keeping them b/c they liked the sound.
 

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Discussion Starter #35
MeanMystic said:
I THINK that when MM&FF had just started building up superfly, The first mod that they did was weld in 2 chamber flowmaster and lost 3hp (same day and dyno). They ended up keeping them b/c they liked the sound.
AHA! I am vindicated!:D

Well, I like the sound too. Guess you can't have it all.:(
 

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Very good, Bierbelly. Good thread. Now you may put back your old HP/TQ numbers! ;)

Magnaflow will be getting a call from Delaware soon I guess!
 

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Discussion Starter #37
mrvax said:
Very good, Bierbelly. Good thread. Now you may put back your old HP/TQ numbers! ;)

Magnaflow will be getting a call from Delaware soon I guess!
Vax, you know, even Flowmasters will wear out eventually. THEN I'll put in something new.
 

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mrvax might potentially have hit on something with the expansion of weld-in mufflers. Have the exhaust gases go from a full 2 1/4" exhaust to a wider muffler and then compressing it back to 2 1/4" could possibly cause undesireable pressure drops, especially in a chambered muffler, where pressure is far more important than velocity to move air from one chamber to the next. In a straight through muffler, pressure drop may have less of an effect on velocity, explaining why many people have good results with welding in Ultra Flows and Magnapacks.

I'm just speculating, and ignoring a whole lot of variables, but it's an idea.

I'm going to be welding in some Dynomax Super Turbos soon, want my old mufflers? One of them has a pea-sized hole in it, hehe.
 

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Don't count on it. I had a 88GT with Flows. They were put on 6 months before I got the car. I had it myself for about 4 years. Those Flows seem to last a pretty long time.
 

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I'm toying with the idea of buying a Flowmaster CB system, or at least some weld-ins and so I've been searching for posts like this one. Let me just say this, dynos (eaven when sae-corrected) can vary a little - even 7 rwhp/ 10rwtq. Here are some facts from my 2 dyno experiences with my stock 2001 GT 5-speed:

first dyno session

first run - 216 rwhp/259 rwtq (SAE-corrected)
second run - 212 rwhp/252 rwtq (SAE-Corrected)

4000 miles
5W30 Mobil One synth
air silencer removed
93 octane/winter blend RFG Chicago gas

Second dyno, different dyno shop

first run - 217 rwhp/260 rwtq (SAE-corrected)
2nd run - 224 rwhp/267 rwtq (SAE - corrected)

7000 miles
5W20 Ford Synth blend
Air silencer trimmed
93 octane - summer/regular non-RFG blend gas

Other than the fuel, I don't see how anyone could make many conclusions on my car based on my dynos.

Back to Flowmasters - I am biased when it comes to the sound of Flowmasters. Even though I am still bone-stock, I just think the Flowmaster sound is the best traditional Muscle-car Mustang sounding exhaust out there. I WANT the Flowmasters to at the very least not rob any power from the car! However, it would seem that when the exhaust gas flow really gets going, the Flows sap some of that flow in the higher rpms.

At the same time, you'd probably have to have a more controlled dyno experiment to prove they rob hi-rpm power. Yet, early indications here on this post and others would indicate it just might rob a little high-end power on n/a vehicles.

And yet, I may just allow for hat trade-off since the sound is so excellent!

Anyone have some additional SAE-corrected dyno data that can show us whether or not their car might have lost/gained power from Flowmaster exhaust?

Bierbelly - did you do just one run or severalruns on the dyno? If you did more than one run, could you post those dyno numbers too? How about your pre-Flow dyno numbers? What were your worst dyno numbers on the pre-Flows you are comparing your post-flows too?
 
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