HP Differences
 

Anyone know what the difference is between the 99 and up GT with 260hp and the 98 GT with only 225 hp. What did they do to get the extra 35 hp?


Thanks!

The '99- up GT's have what are called PI (Power Improved, Product Improved, whatever you think it stands for) heads. These heads flow considerably better than the non-PI heads on my car. The intake manifold is also slightly different on the '99-up's. Another difference is the newer GT's have a returnless fuel system (Doesn't effect power though).

The cams are also diffrent. Less Lift, longer duration. Oh, a quick question. Why do the duration of the intake side of the Cams differ from one cylinder bank to another?

I might be answering my own question, but I'm thinking it may be because of the intake, there trying to equal out intake flow.

Actually the cams are the same for both heads. They have a split duration between intake and exhaust. So the exhaust valves with .540 duration will stay open longer than the intake valves at .510.

Basically the difference in the cars is the heads/cams.

Bill