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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.
 

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jvitale,

Do you think changing the whole exhaust system would eliminate the flatten pipe? For instance, is the flattened pipe a part of the cat back that will be taken out anyway if replace by a performance cat back? Or is it something we willhave to get rid of even if we got perfomrance cat back?
 

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Restriction

Sounds like a winner, can't wait to hear what a difference it makes.
 

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Thanks for the great detective work. You have really done a lot by comparing parts at the dealer and heavily checking your car both inside and out.

I hate to frustrate you, but this flat piece in the exhaust was brought up back in October... http://www.altimas.net/forum/showthread.php?s=&threadid=6948

And in this thread, http://www.altimas.net/forum/showthread.php?s=&threadid=9863 it is brought up again, with links to pictures of the maxima exhaust.

Anyway, I already went by the muffler shop and they said it would be super cheap to replace this section of pipe. I would like to dyno my car, then replace the section and dyno again, but that would be a lot of money out if I am still planning on getting a cat-back exhaust! So.... not quite ready to shell out the dough to be the lab rat!

I AM thankful for you finding out that the muffler is not variable-flow on the 3.5. I had thought it was. But looking at my Dealer Product guide that tells all about the Altima, it is not an option on the 3.5! Good detective work again!!
 

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I knew about the flat spot in our exhausts, and that would make sense of mossy's numbers. Not the overall hp of course, but the tremendous gains he achieved with just his cat-back.
 

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And going on this logic, we could probably achieve more hp than that out of the cat-back. Just looking at mossy's exhaust without the flat spot gave us the 15 hp back to equal the maxima's. Now when you consider that people will make a cat-back for the maxima(which will undoubtably gain hp over stock). So considering the research that you did to establish that everything else was the same between the two cars, than we should all look to gain more than 15 hp on a more finelly tuned mandrel bent exhaust.
 

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jlangton said:
And going on this logic, we could probably achieve more hp than that out of the cat-back. Just looking at mossy's exhaust without the flat spot gave us the 15 hp back to equal the maxima's. Now when you consider that people will make a cat-back for the maxima(which will undoubtably gain hp over stock). So considering the research that you did to establish that everything else was the same between the two cars, than we should all look to gain more than 15 hp on a more finelly tuned mandrel bent exhaust.
So the logic is that if both Maxima and Altima 3.5 has upgraded its exhaust, then both hp figures will be extrmely similar. Probably more for Altima since it has dual mufflers.

The Altima will also gain more from using CAI than Max because it has a better flowing exhaust. The gearing of the Altima will also make the Altima have a better 0-60 time due to its shorter gears compare to Max's.
 

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I find this hard to believe. A few things from my experience on working with exhaust systems.

For example. If you know the 98+ FBODYs they have a CRIMP on the driver side of the exhaust, where it goes under the driver seat and floor board. The reason for this crimp is due to clearance problems with the road. I have a feeling this is the same due to the DUAL exhaust on the 3.5L Altima.

When people replaced this CRIMPED exhaust on a big V8, just this section, it showed no gains.

The section of exhaust maybe moon shaped (crimped), but it is slightly WIDER than the rest of hte exhaust. This gives the same space for the exhaust to travel.

No exhaust crimp or any type of restriction will cause a 15 hp gain guranteed.
 

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Russ2kSE, You definatly could be right, but you can't completly rule out the possibility that this could be true. And i didn't say that that WAS the way i said, i just said going by what jvitale told us, that this might be the case. maybe, maybe not, either way we won't know till someone can get some good, accurate dyno runs posted.
 

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3.5-SE said:


So the logic is that if both Maxima and Altima 3.5 has upgraded its exhaust, then both hp figures will be extrmely similar. Probably more for Altima since it has dual mufflers.
Sorry but the Altima's dual exhaust will not give better HP #'s then the maxima's. The alty's exhaust is not even real duals, all it is is a fashion statement that hert's performance because of the extra weight.



The Altima will also gain more from using CAI than Max because it has a better flowing exhaust. The gearing of the Altima will also make the Altima have a better 0-60 time due to its shorter gears compare to Max's. [/B]
B.S. again, the altima will never have a better flowing exhaust, at best, equal to the max's. As for better 0-60 times? Wrong again, my 6spd max has a longer first gear then your Alty's {which helps traction a bit} and 2nd gear is perfect for 0-60 because it goes to 62 MPH rather then the altimas 67MPH in 2nd gear.


BTW guy's, don't get the idea I don't like Altima's or anything like that, I think both the max and Altima are great cars. I ahd a hard time choosing between the two. :)
 

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emax said:


Sorry but the Altima's dual exhaust will not give better HP #'s then the maxima's. The alty's exhaust is not even real duals, all it is is a fashion statement that hert's performance because of the extra weight.





B.S. again, the altima will never have a better flowing exhaust, at best, equal to the max's. As for better 0-60 times? Wrong again, my 6spd max has a longer first gear then your Alty's {which helps traction a bit} and 2nd gear is perfect for 0-60 because it goes to 62 MPH rather then the altimas 67MPH in 2nd gear.


BTW guy's, don't get the idea I don't like Altima's or anything like that, I think both the max and Altima are great cars. I ahd a hard time choosing between the two. :)

I see your stand view. YOu own a maxima, so you talk for the Maxima. But why are you defending for the 2002? You only have a 4th gen, which doesn't even stand close to a 2000 Maxima.
 

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Russ2kSE said:
I find this hard to believe. A few things from my experience on working with exhaust systems.

For example. If you know the 98+ FBODYs they have a CRIMP on the driver side of the exhaust, where it goes under the driver seat and floor board. The reason for this crimp is due to clearance problems with the road. I have a feeling this is the same due to the DUAL exhaust on the 3.5L Altima.

When people replaced this CRIMPED exhaust on a big V8, just this section, it showed no gains.

The section of exhaust maybe moon shaped (crimped), but it is slightly WIDER than the rest of hte exhaust. This gives the same space for the exhaust to travel.

No exhaust crimp or any type of restriction will cause a 15 hp gain guranteed.
Damn the guy over there " 3.5-SE" is leaking out all kind's of B.S.! I am suprised you did not say anything, I just gave him my thoughts :D . He thinks his fake duals and longer 2nd gear will help make his car quicker then a max 0-60. Better with a CAI too? WTF!?
 

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emax said:


Damn the guy over there " 3.5-SE" is leaking out all kind's of B.S.! I am suprised you did not say anything, I just gave him my thoughts :D . He thinks his fake duals and longer 2nd gear will help make his car quicker then a max 0-60. Better with a CAI too? WTF!?

As the guy who started the thread said, the Altima shares the same engine as Maxima. To put things in perspective, Maxima uses the Altima's engine. :D
 

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emax said:


Damn the guy over there " 3.5-SE" is leaking out all kind's of B.S.! I am suprised you did not say anything, I just gave him my thoughts :D . He thinks his fake duals and longer 2nd gear will help make his car quicker then a max 0-60. Better with a CAI too? WTF!?
I agree.. He doesn't have real hand experience so he really has no idea what he is talking about.
 

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3.5-SE said:



As the guy who started the thread said, the Altima shares the same engine as Maxima. To put things in perspective, Maxima uses the Altima's engine. :D
And even more perspective. The Altima and Max use the Pathfinders engine.
 

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Discussion Starter · #17 ·
The flattened section is part of the OEM cat-back. This clearly explains why the Mossy system produced such tremendous gains.

Russ2kSE, I know you have your doubts, but it is a scientific fact about the Mustang losing 20hp because of a crimp in the system. I do not know about a F body, but I would guess that the engine just did not have anymore power to give.
 

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"Sorry but the Altima's dual exhaust will not give better HP #'s then the maxima's. The alty's exhaust is not even real duals, all it is is a fashion statement that hert's performance because of the extra weight.





B.S. again, the altima will never have a better flowing exhaust, at best, equal to the max's. As for better 0-60 times? Wrong again, my 6spd max has a longer first gear then your Alty's {which helps traction a bit} and 2nd gear is perfect for 0-60 because it goes to 62 MPH rather then the altimas 67MPH in 2nd gear.


BTW guy's, don't get the idea I don't like Altima's or anything like that, I think both the max and Altima are great cars. I ahd a hard time choosing between the two. "
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Even though I went with the possibility of keeping as much hp through the exhaust as the maxima, I have to agree with emax's statements here. Especially if you go with the assumption that what i said was right, you're still working with the same engines, so there is no way you could have BETTER exhaust flow than the maxima, especially considering our fake dual's, but i do think that we will have an equal flowing exhaust......just not better.
 

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Russ2kSE said:


And even more perspective. The Altima and Max use the Pathfinders engine.
wassup w/altimas always sharing engines w/trucks and the like?! hehe
Jay
 

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jlangton said:

Even though I went with the possibility of keeping as much hp through the exhaust as the maxima, I have to agree with emax's statements here. Especially if you go with the assumption that what i said was right, you're still working with the same engines, so there is no way you could have BETTER exhaust flow than the maxima, especially considering our fake dual's, but i do think that we will have an equal flowing exhaust......just not better.
So if the Altima has the exhaust swapped, it will have very similar hp figure as the Maxima, if not the same.... is this correct??
 
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