DAVE05GT

Like I said, I am referring to individual 05 owners who are claiming hp gains in the 10 hp arena. If you are some kind of modular 4.6 engineer and you know that the 05's don't respond to any exhaust upgrades like other Mustangs than those folks must be delusional. If not then your opinion is not as convincing to me as a dyno sheet provided by several people who actually have the mufflers and have taken their time and effort to dyno them and post it for the rest of us. I'm only interested in these figures out of pure curiosity because like you I tended to believe that no one would see any gains from just mufflers because of what I had read in the past, and further, even if Corsa's claims are proven I'm still not buying a set because they are over priced. You can believe everything a magazine tells you or you can do some research for yourself and then form a more educated opinion and possibly even gain 10 more hp, your choice.

F1Fan

Hi Dave05GT,

It doesn't, we found no difference in A/F ratio with any of the three axle back systems we tested with an optimized tune for the Steeda CAI, JBA shortys, Magnaflow Tru-X Pipe w/cats on 93 octaine fuel. So there would be no power or torque advantage to altering the timing or fuel for any axle back system that didn't make a difference in A/F reading on the WBO2 readout. My guess is that NO performance axle back system will need a different tune once the tune has been optimized for the engine and exhaust components ahead of the mufflers under test for two reasons. First unless the new muffler is so restrictive that it can alter the A/F ratio there would be no improvement in power to be had and second because I tested an open pipe approximating the length of the stock Ford mufflers and could measure no difference in A/F ratio. This tells me that there is no power to be had by altering fuel or timing unless the A/F ratio was altered by the mufflers. So if I were to test Corsa's muffs and use the same SAE correction factors the baseline data would still be good enough for comparison purposes. A few ponys +/- is not going to make any difference as the dyno's are not that repeatable.

HTH

DAVE05GT

http://motownmuscle.com/forums/printthread.php?t=12646

http://www.corsaperf.com/mustang.htm

Here are two, I know one is Corsa's but it's just for reference. I happened across one or two others that I couldn't find again in the amt of time I had to look because it was just someone posting the #'s on some forums but with more time I'm sure you can pull them up and those are what I'm refering to. F1 Fan, you make a good arguement but I don't understand why these people would go through the hassel of posting this stuff if it was BS.

bahbahblacksheep

Dave, its not reading and believing magazines. Where I live, there are 3 of the biggest mustang tuners in North America. There's Sean Hyland Motorsports, there's Steeda, there's Dasilva racing. I've talked to some of these guys at length about exhaust tuning on the 2005 4.6 3V Mustang and the concensus is that you change the axle backs for sound and looks (ie tips), but unless you are going to do something more extensive like long tube headers, cat deletes, forced induction etc...there will be little to no gain (if not a loss in performance). I have talked to people who are in the know. They are good guys who could make tons of money selling me parts but they don't.

AND, with regards to DYNOS...

You can run your car on the dyno 3 times and I bet you get different numbers each time. They'll be in a certain range but different numbers each time. That's what I mean when I don't trust dyno numbers. Obviously if the results are repeatable over time and under similar conditions then there might be more to it. But if I see a dyno with 2 runs...one stock and one with a mod and there's a small variance in the numbers, it could be explained by other factors

DAVE05GT

Alright your not understanding my point here. I know the general concensus on axle-backs and I'm sure the ones I have didn't give me much power but I would like someone who is a member of this site to do some before and after pulls with these things to see what all the hype is about. I feel like I'm on Corsa's pay roll here but all I'm saying is that I've seen convincing data to support both sides of this one and I would like to know one way or the other without being rash and saying Corsa and those who own their products are full of $#!^. I've heard the same things as you have and you telling me over and over again is a waste of time because I'm keeping an open mind here on this one. I've seen multiple people back up Corsa's claims on dynos but not one who has posted dyno results that show otherwise, just a bunch of people giving their opinions. Also, dynos are not usually off by 10hp, the conditions (humidity, air temp, engine temp) could account for a difference like that but not just the dyno.

F1Fan

Hi Dave05GT,

The test on motownmuscle was done on a completely stock car except for the addition of the Corsa muffs. This is what I found, when you have a stock exhaust system and add a straight through rear muff you may get some improvement in power but not as much as on a car with better breathing further upstream like headers, high flow cats etc. BUT the problem is that once you have the upstream components working adding a straight through rear muffler can make a car VERY loud and you may also lose mid-range torque and HP. This is what happened when we dyno'd the pieces of straight pipe clamped to the stock over axle pipes. Not ideal for a street car or even a race car if the mid-range losses are not significantly offset by larger power gains in the upper RPM range.

Personally I don't think the individuals reporting some power gains with XYZ brand axle backs are trying to deceive us, they are just telling us what they found under the conditions they had at the time they tested. Of course there's a large amount of variation in how dyno power is calculated from the raw dyno torque readings and it is rare that the people reporting their results are using SAE corrections for air temp at the intake inlet (if hey even bother to measure the actual inlet air temps.), and barametric pressure. Also hot dyno pulls and back to back pulls will not show accurate power numbers due to hot soak of the engine. A funny thing I found with the Steeda CAI was that when dyno testing on a warm-hot day (this is SoCal afterall), with a hot car and the hood open can kill your power numbers even if you have a pair of large (48" inchers), high flow fans blowing at the car. Closing the hood after a fan powered cool down and pumping lots of air at the car during a dyno pull can result in 10-20HP more power than wih the hood up and I'm sure under some conditions even more. I did not have my Meziere electric water pump hooked up with the switch to turn on the rad fans at the time of the crazy testing I did so I don't know how much more power can be found with lower coolant temps and avoiding a hot soaked engine. BTW, I baselined the car and then retested with the Meziere using SAE corretions and it's good for about 10+HP depending on RPM range you look at.

HTH

DAVE05GT

F1Fan,
Some more good info, and thats what I meant when I was talking about your car's intake/tune etc. and the results you were getting with your setup. People think you can take say a C&L and Predator combo usually rated around 26hp max and throw on an x-pipe (12hp max), plus pulleys (8hp max) and have a 46 hp increase at the rear wheels. Not true, these are the best #'s people could get on an otherwise stock car and they are not cumulative. This is why I didn't just say yep, Corsa's marketing reps are a bunch of scam artists.

About the engine heat soak, a lot of folks agree with you and say that the radiator is just a little small on these cars for doing consecutive dyno pulls and that they require a little longer than normal cool off time in between pulls.

As far as people "cooking the #'s" and not reporting SAE corrected figures, or running at colder temps to get more hp is just shady. I agree that folks should be skeptical of dyno results especially when it's from the manufacturer, but if Corsa's setup is giving stock 05's 10+ hp then attaboy to them and if not then I sure hope they sound $300 better than my SLP's.

BTW, thanks for being so helpful with the header questions.

drbobvs

Fi fan,
Do you think I would get any power increase or sound change with just adding shorty headers (Ford Racing)without any other mods?


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bahbahblacksheep

Dave, although it goes against my logic, I think you have convinced me to keep an open mind about this one also. It's more like I hope that these mufflers can actually get 13hp. I have my fingers crossed. I'm still digging to find out more about the corsas.

DAVE05GT

Yeah it goes against mine too, if I were to search on this site a little I could pull up a least a few posts where I dogged Corsa pretty bad about their claims. Thats why I waited until I got a really good price on some like new Power Flows before I got them since I knew I wouldn't get any performace from them but the sound is worth every penny of $150 to me. But even if the claims are real, I still agree with F1Fan that once other mods are added, the Corsa's will be obsolete.