I'll let my new times do the speaking:

18.10 @ 75.3
18.00 @ 75.3

I couldn't bear to do anymore runs...

I can feel a significant decrease in low end torque and power. Granted it does sound good, but is really just a $150 noisemaker. I was expecting around 5 hp, or maybe slightly less, but I believe I've lost nearly 20 ft-lb. of torque or more, with not much power increase in the upper RPM (certainly not enough to make up for the drop in 1/4 mile time).

I will be reverting back to stock ASAP...

Anyone had better luck with a different muffler? (Sucks to pay $150 and lose 1.5 seconds on your quarter mile, it feels like a 4-banger now)

 

That is why I went with gibson. They make um vehicle specific. I am sorry about the loss of hp I could relate. [sm=headbang.gif]

 

Did you actually do any kind of testing to show you gained HP with the Gibson?

 

I've been checking on some of these oddities myself and have little to offer to help you. There is also a real set of folks in existence that thoroughly believe that a louder exhaust is making them go faster. I had the same thought back in the 60's when my first muffler got a hole iin it. Boy was I exited. 85 horsepower and I thought it was a race car.

What I have concluded is that there is little 'hidden' power on any of these vehicles. There is little to be gained from simple mods to exhaust. Even the guys screaming and raving about how great their new air cleaner works have not taken into account that they replaced a DIRTY air filter with a clean one. A better comparison might have happened if they had gone to the track with a clean element and timed the car, then switched over to the majic one.

The investment required is much deeper into the working of things under the hood. Yes, some chip changes will modify the performance curve because they ask for more timing, more fuel and more air. In the end sacrficing mileage. At the very least any modification will get the car worse mileage because the driver is 100% sure that it has GOT to be going FASTER. They all do when you are expecting it and dont measure against a clock or dyno. It will if you think so positive that the foot lands harder on the pedal????

So about the only way an exhaust will actually do anything at all it when it is a true equal length header design, and dual all the way from front to back. Even then, I suspect you wouldnt see more than 15 horsepower on a stock motor and the investment and perhaps voiding warrenties and such is simply not worth it. Even then, I have come to the conclusion that the engine tuning is based on the amount of stock back pressure that is found in the original design. A REALLY great exhaust may even cause problems unless other facets of the tuning are taken into very serious account.


To get a little more, you'd also have to do the intake sytem change and the chip at the same time. I still think that you'd get nothing worthwhile till the camshaft were changed and a proper tuning curve for this new cam was programmed into your puter. In other words, you would have to really change about everything to match the cam.



It's ok though, no-one believes me anyway. A louder exhaust is ALWAYS faster, right? Bigger wheels/tires used to work too. Oh, almost forgot air shocks????

 

Go to this site GIBSON and tell me what you think.

 

Remember that temp., wind resistance, track, and others are important factors...if your times are not taken with the same parameters your times will not be consistent...

Performance mufflers do make you loose a tad of low end but after you are in the high rpm's you should pull faster...really don't know how you lost almost 2 secs....that is too much...I mean, I only used a $30 muffler, got rid of the cat and did not loose SO much low end...man, I don't know what to tell you...sad you paid all that dough and found out it was not worth it...

 

I have to agree with Blazingsadle. Changing the muffler and the pipes after the cat is nothing more then a noise maker. Your exhaust doesn't make power, your engine does. The only way your going to free up some of that power on the output side is to install headers. The rest of it is too far downstream to make any difference, as your test results show.

 

Now, I know the stock muffler is decently restrictive. Could the numbers shown on the Gibson be correct? It appears as though they tested my same engine, only in a 2-door blazer. One thing that immediately catches my eye is the fact that they don't show what RPM that power and torque is made... If you get an additional 21 ft-lbs of torque at 5000 RPMs but lose 30 ft-lbs at 2800 RPM, then it's going to end up still slowing you down. I'm gonna e-mail them and see if I can't get a hold of the actual dyno graph...

 

What you should be worried about is not the peaks, but the area under the curve. The more area under the curve, the better overall your vehicle will perform. Now with that said, you want to look at 1st gear all the way from idle to shift. Then 2nd & 3rd will be the rpms where the shift drops them down to. You may not get off the line as well, but if 2nd and 3rd gears have their respective area under the curve that much higher than stock, you may make up for doggin' off the line.

Peak HP is fun for braggin' rights, but it really doesn't mean much. What is a nice thing to have is 90% of peak torque available off the line like my Bonneville has. A nearly flat torque curve is a great thing, but that's what the blower does to most torque curves.

 

I agree. This is why the peak hp numbers offered by companies really means nothing to me now. I want a dyno so I can actually SEE where the power is made, and where (if applicable) power has been taken away...

I would guess that the dynomax gave me a slightly better HP peak, but gave that peak so late that it didn't matter at that point. The damage had already been done...