i just put a single in dual out flowmaster type muffler on and ran it out in front of the rear tire. it sounds great but it feels slower than before. all i have is the exhaust and a k&n cold air intake. i plan on putting headers, e fan, underdrive pulleys, and getting a bama custom tuner for all that. will that bring everything together or do i already need to change my exhaust to something more restrictive? should i run duals all the way out the back?

 

To be honest, you're expecting too much out of the exhaust mod. At best you get about 5% more hp or about 7.5, which is hard to "feel". You won't get slammed into the seat by just adding an airfilter and exhaust. Just the way it is. Small bolt-on mods may "add-up" to greater hp, but by themselves they don't make major improvement.

 

yeah that part i figured. the k&n made a feelable difference for the better but the exhaust actually felt like it hurt the performance. it felt better with just the k&n than the k&n and exhaust. i'm just wondering if all the mods together will complement the exhaust or will the headers just make it worse? will the bama tuner help make all of that stuff work to its full potential?

 

How long have you had the exhaust on? It takes a bit for the ECU to adjust, and the enviromental factors may be different. On cold days, my truck runs great; while hot humid days make it run like a dog. Give it some time.

Dollar for dollar, I hear more great responses about the bama tuner than I do about any other performance mod.

 

the better the flow, the better the go! at least that should be what it is in theory. When I got my exhaust, I had the stock intake with a K&N drop in. and it sounded weird, and didn't really give much more performance. Once I put a CAI in there it sounded more full and gave more power, but since you've already got the intake, I don't know what to tell ya.

What size is you're exhaust and what size is the intake?

 

not sure what size the intake is but the exhaust goes straight from the stock 3rd cat to a 2 1/2 in. pipe about 4 in. long to the muffler the exits to 2 pipes that are about 2 1/2 feet long out the side with 3in. tips.

 

A new exhaust shouldn't cause less performance. If anything it would add or just stay the same. Most people get exhaust for the sound and or performance. I have never heard of people lossing performance from and exhaust unless you installed it wrong and or it has a leak in the piping.

 

Actually, a less restrictive exhaust sometimes causes problems with lower RPM torque, while helping high RPM HP. Although I know this is true, I'm not sure how you can properly determine the best exhaust setup.

The problem involves the velocity of the exhaust gases and the fact that the exhaust system "pulses". At lower flow rates, more restriction (particularly smaller pipes) is supposed to keep things moving more quickly and aid "scavenging" when the exhaust valve opens -- however, it's murky as to how to design for this exactly.

I think that takes some serious work and may even be more empirical than theoretical in order to get it right (that is: you may have to play with it and can't just calculate it).

 

i just put my borla proxs on a couple of weeks ago and felt an immediate improvement in power. Not a lot, but enough to notice. I was being told on these forums that if I got a flowmaster and dumped it before the rear axle that I would lose torque. I was also told that flowmaster is more for sound improvement and less for performance, so that probably has to do with it.

 

^ exactly

 

Rule of thumb with modern vehicles for scavenging is if you keep the Cats on you will have enough restriction close enough to the exhaust valves to not lose low end torque.

 

I just put on a Flowmaster 40 with the same exit you have, duals out in front of the tire, and I noticed much more torque and a beter idle. Try unplugging your negative battery cable and leave it off for about 15 minutes, then plug it back on.