4.6Gtconv

I recently installed, bbk OR/X midpipe, running spintech prostreets. It sounds good the only problem is, Between 1500-3500 rpms i lost all low end torque and power ? Is the particular reason because there is too much free flow ? and now not enough back pressure ? and if that is the case would going back to and H pipe fix this ? or would that be useless because no cats ? Help and suggestions please !! thanks

Fink

I would swap the mid pipe again and see if that solves anything. You may need to get some cats welded in.


I personally didnt feel much of a difference in torque(slight loss) when I went to an O/R H on my sixxer... but I did install longtubes at the same time.

TheNameless

with an x you should experience more power above 3500 rpms. did you take your car over 3500 rpms yet?

4.6Gtconv

Yeah I have gone over 3500 rpms, and at that range you can feel the power again, but when i want to hit the gas for a little umphh, seems like im always going to have to jam up the rpms then ?

mrtstang

I experienced the same thing when i switched my catted h to a o/r x. I could feel a slight loss in the lower rpm's.

cliffyk

Backpressure is never good, if you have lost power in a particular band then it is more likely the exhaust system has a resonance in that band that is adding restriction--given the design of the Spintech mufflers this is not surprising, they are not really intended for street use.

Read more about the back pressure myth here, and here...

Kerns

Thank you Cliffyk, I hate how everyone always talks about losing back pressure causing a loss in power. Glad there are others out there trying to correct the myth.

Rockwell28

Its weird how a lot of ppl losd low end and gain top end when running the off road midpipe vs a catted one. But according to the whole sceince behind the backpressure thing you should gain but seems as if th pl who do it lose low and gain up top.

PurpleIcedGT

Rockwell.....wait what??????!

scottybaccus

Many folks never understand that low end torque is created through exhaust velocity. The high velocity gasses create momentum in the exaust that lets the flow actually create a draw on the exhaust port, evacuating the cylinders and during valve overlap, pulling the intake charge into the chamber. It's knd of a natural supercharging.

Now that you have big high flow pipes, you have to spin higher rpm to move enough volume of gasses to get back to that velocity level. This means the power band moves up the rpm range. Do you make more torque? Yes, but at at different rpm.

Too many people make changes like this, overshooting the usable range of their normal use and killing the daily performance. You may scream at the strip, but life sucks around town.