I have noticed lately that my car doesnt have that get up and go that I usually have. I have in the last 6 months moved from Austin to Phoenix and had to switch from 93 octane to 91 since that is all they have here. I have just hit 45K miles. Can anyone think of what might be wrong and where my horsepower has gone?

 

not to nit-pick but it is torque that you lost not horsepower
torque gets you going
HP keeps you going

 

Can ya provide more details? How've you been maintaining the car? Mods? Etc etc... could be many things so we'd need more info....

 

I have not done any mods other than put a air hog filter in my car about 10,000 miles ago.

 

You could start by cleaning the filter. Altough they last forever you still need to clean them espiecially if your out in the desert with all the dust.

 

Just throwing an Idea out but maybe a Maf issue. Can you elaborate more on the problem your having.

 

yeah let's hear more details

 

Horsepower is a function of torque and RPM. A car like the S2000 is a "torqueless wonder," because it can put out the horsepower of a V6 Altima even though it only has as much torque as a base 1.8L Sentra. It does this by revving up to 9000RPM (on older models... the new ones have a lower rev limiter and more torque if I remember correctly). Unfortunately, this means that an S2000 only feels powerful if you can rev it up pretty high. In city driving, an S2000 feels a lot less powerful than it really is, because it has very little torque, so power is only available at high RPMs. The VQ-powered Altima and Maxima, on the other hand, has plenty of torque on hand, so we can make well over 200 horsepower without having to rev up to 9000RPMs. Our rev limiters seem low to many Honda/Acura owners who have to rev their cars all the way to outer space to get any power. That's why it's so attractive for Nissan owners to get ECU modifications (and stiffer valve springs if necessary, and balance shaft removal on cars like the Spec-V) in order to raise the rev limiter. If a "torqueless" engine can make mad power by revving high, then nice torquey engines like the ones Nissan uses make crazy power by revving high. We just have to reinforce them so they won't break at high RPMs.

Back to the issue at hand:

You say that only low end performance is gone? Can you pinpoint around what RPM the car starts to feel "normal" again? It it around 3500/4000RPM by any chance?