downpipe and low-end (~2K) torque - loss?
 

Since I've had a downpipe on my car (about a week or two), I've noticed that I don't have as much low end torque as I used to - I used to be able to give it some gas on the freeway at around 2K rpm (5th gear) and it would pull pretty good, it doesn't seem to do that now.

Did anyone else notice this? I deffinitely notice more power on the high end, but the low end torque seems to be reduced...

If no one noticed this, could it be a leaky exhaust gasket? Could removing and reinstalling my O2 sensor have hurt it (the O2 sensor, that is)?

We're certainly not talking about a huge difference here, but somewhat noticeable. I guess it's possible that I'm just not giving it as much gas as I was before, even though I think I am, because I can hear the turbos so much more now.

:confused:

I didn't notice any decrease in power on the low end when I put mine in. The only thing that will cause this is a mid pipe. Well that and single turbos.

A leaky gasket you would definitely hear. It would be louder, so I doubt it's that.

From dynoplots I've seen, usually the reverse happens with the downpipe adding low-end torque(with the main cat in place). The downpipe allows the primary turbo to spool up faster.

Re: downpipe and low-end (~2K) torque - loss?
 

In that situation I just downshift. I never stomp on the gas unless my rpms are near 3k in 3rd through 5th gear. I remember reading on the big list about torque load (many moons ago) and stress on the motor. Basically, it's not the best thing for out little 13B's to accelerate from that low an rpm; places an inordinate amount of stress on the motor.

Of course, this was 3 yrs ago and my memory doesn't work too well anymore :). I wouldn't worry about it.

hmmm... well, it may be just in my head. I drove home tonight with the stereo up so that I couldn't hear the turbos & seemed like normal.

oh, on the theme of higher stress at lower rpm, I agree... I've even heard that you run a bit more lean on the low end, esepcially at WOT (although, I can't make too much sense of that)... I generally downshift to pass, but just picking up speed is another story.

thanks guys.

I recently had a downpipe put in and I noticed the same thing as BrianK. I think that the downpipe makes the exhaust sound a tad louder and that makes it appear that you do not have as much power at the low end. I also can hear the turbos much more now.

Lower back pressure is supposed to reduce lower torque and increase upper end. So, it's normal to expect that a DP or CB would reduce some lower torque. However, it shouldn't be too sluggish off the line.

I've heard it many times before but does anyone actually know the reason why less back pressure reduces low end torque?

Certain level of Back Pressure is needed for the torbos to function properly.
 

Was told by Peter Farrell