This hp difference has been really bothering me since I bought the car on 9/14. It has taken me over 2 months of comparing specs in service manuals, comparing numerous engine part numbers and crawling under the cars, but I finally cracked the code on the difference in the HP ratings between the 02 Alty and 02 Max.
As we all know, the Alty makes 240hp @ 5800 rpm and 246 lb-ft torque @ 4400 rpm while the Max cranks out 255 and 246 at the exact same rpms, respectively. Having known this from the start I suspected that it was something very simple because mechanical modifications would have changed the torque figures and/or would have raised the RPM at which the Max achieves its 255hp (higher than 5800 rpm). Also, Nissan is in the business of making money. They do this by interchanging parts between all of their vehicles to keep R&D and production costs down. Nonetheless, I went to the dealer and had them compare several part numbers between the Alty and Max. Pistons, cams, head gasket, head, ECU, intake manifold, exhaust manifold, all the same. I have also been communicating with an 02 Max owner on Maxima.org. He has been kind enough to provide me with specs out of his service manual. The key spec there was compression pressure. Both identical at 185 psi. So, if the mechanicals are the same, why the hp difference. Must be something with the exhaust downstream of the exhaust manifolds. So I checked out the Y pipes. Same. Same rear Cat also. Main muffler just rear of the cat is actually larger on the Alty. No problem there. The Max has that variable capacity muffler, not the 3.5 Alty (only the 2.5 Alty). But the Alty has dual exhaust which gives the exact same effect, if not better. So what gives? Well I was lying down under my car playing around with the gas tank to see if it was loose. Has anyone else noticed that when the tank is full and you come to a stop there’s this clunking sound when the gas sloshes forward. I thought the tank was loose. It wasn’t. Just a very cheap and flimsy plastic tank. But while I was yanking on the tank to see if it was loose, I was holding on to the exhaust pipe just under the tank for leverage. That’s when I found it. There is a one-foot section of pipe directly under the gas tank that has been intentionally restricted (flattened) by Nissan. The upper half of the pipe is flattened which makes it impossible to spot unless you are looking for it (the pipe is shaped like a half moon looking at a cross-section). This is how Nissan lowered the HP on the Alty so as not to compete with the Max. Makes perfect sense also. Do you all remember the C&D report (7/01 issue) on the 99 SVT Mustang that lost 20hp because its exhaust was flattened 20mm to clear the rear control arm. The Alty is flattened much more than 20mm.
Sorry for the long story. As soon as I get a chance I’m going back under my car with a hack saw and cut the flattened section out and replace it with a new section. So for about $10 I can re-gain that 15hp back.
As we all know, the Alty makes 240hp @ 5800 rpm and 246 lb-ft torque @ 4400 rpm while the Max cranks out 255 and 246 at the exact same rpms, respectively. Having known this from the start I suspected that it was something very simple because mechanical modifications would have changed the torque figures and/or would have raised the RPM at which the Max achieves its 255hp (higher than 5800 rpm). Also, Nissan is in the business of making money. They do this by interchanging parts between all of their vehicles to keep R&D and production costs down. Nonetheless, I went to the dealer and had them compare several part numbers between the Alty and Max. Pistons, cams, head gasket, head, ECU, intake manifold, exhaust manifold, all the same. I have also been communicating with an 02 Max owner on Maxima.org. He has been kind enough to provide me with specs out of his service manual. The key spec there was compression pressure. Both identical at 185 psi. So, if the mechanicals are the same, why the hp difference. Must be something with the exhaust downstream of the exhaust manifolds. So I checked out the Y pipes. Same. Same rear Cat also. Main muffler just rear of the cat is actually larger on the Alty. No problem there. The Max has that variable capacity muffler, not the 3.5 Alty (only the 2.5 Alty). But the Alty has dual exhaust which gives the exact same effect, if not better. So what gives? Well I was lying down under my car playing around with the gas tank to see if it was loose. Has anyone else noticed that when the tank is full and you come to a stop there’s this clunking sound when the gas sloshes forward. I thought the tank was loose. It wasn’t. Just a very cheap and flimsy plastic tank. But while I was yanking on the tank to see if it was loose, I was holding on to the exhaust pipe just under the tank for leverage. That’s when I found it. There is a one-foot section of pipe directly under the gas tank that has been intentionally restricted (flattened) by Nissan. The upper half of the pipe is flattened which makes it impossible to spot unless you are looking for it (the pipe is shaped like a half moon looking at a cross-section). This is how Nissan lowered the HP on the Alty so as not to compete with the Max. Makes perfect sense also. Do you all remember the C&D report (7/01 issue) on the 99 SVT Mustang that lost 20hp because its exhaust was flattened 20mm to clear the rear control arm. The Alty is flattened much more than 20mm.
Sorry for the long story. As soon as I get a chance I’m going back under my car with a hack saw and cut the flattened section out and replace it with a new section. So for about $10 I can re-gain that 15hp back.
