1. In 2000, the 5th Gen Maxima was introduced. Their were two different emissions setups available depending on where the car was being sold... Federal and California. 2. In 2001, this was changed and all Maximas now conform to the California emissions requirements. 3. The 2000 Federal emissions setup has three O2 sensors. One located on each side of the y-pipe close to the exhaust manifold. The third is located after the main catalytic converter. 4. The CA emissions models have four O2 sensors. The initial two O2 sensors remain the same as on the federal model, except they bolt up in slightly different locations in the exhaust. The rear O2 sensor on the Federal car is replaced by two downstream O2 sensors, located behind each precat. So basically there are four O2 sensors with one located both before and after each precat in the y-pipe. 5. The rear precat in the CA emissions cars is entirely located within the y-pipe, so the rear exhaust manifold on the Federal and CA cars is identical. The front precat is somewhat built into the exhaust manifold. This is another difference between the Federal and CA cars. These differences are further illustrated in the pics below. 6. When buying an aftermarket y-pipe, most places make two versions... one Federal... one CA. The difference is that on the Federal model, the y-pipe runs all the way up to the exhaust manifold on both sides of the engine. On the CA model, the y-pipe runs to the exhaust manifold on the rear side (just like the Fed model), but on the front side, it only runs to a flange located after the front precat. Therefore the stock front manifold and precat remain intact. This fact alone will reduce the performance gain realized by installing an aftermarket y-pipe, when compared to a Federal model. Stillen has done something a little different. They have made a two piece y-pipe that will fit either a Federal or CA emissions Maxima. The main piece is made to bolt up to a CA emissions vehicle. The second piece goes where the front precat is located on the CA emissions vehicle and is flanged to bolt up to the Federal front-side exhaust manifold. With this basic understanding, it is relatively easy to see where I came up with the following idea. One of the main restrictions in the stock y-pipe is the precats. Since the CA y-pipe only replaces one precat it is not as beneficial as the Federal y-pipe. So, why not try to "convert" my car from CA emissions to Federal emissions and use the Federal y-pipe. Now, by "convert", I mean the following: 1. Do whatever is cost-effective to gain the lost HP inherent in the CA emissions models. 2. Do so without generating any check engine lights. 3. Setup the car so it will still pass emissions testing. With this in mind, I decided to give it a go. The first step was to relocate the O2 sensors to after the main cat (similar to the Federal car, except there are two of them). This managed to keep the ECU happy, eliminating concern #2 above. Since the main cat remained in the exhaust system, it should still pass emissions testing in AZ providing that the car is already up to normal operating temperature. This O2 sensor relocation can be viewed by clicking here. The next step was to order a Federal front-side exhaust manifold. The exhaust manifold was easier to find that I had anticipated. I checked with my local Nissan dealership's parts dept and found that the part number was the same for all Maximas from '95-'00. This made my search much easier. I visited Car-Part.com and searched for the Federal emissions front-side (actually called left-hand side) exhaust manifold and found many places with this part. I bought mine from AA Auto in Little Rock, AK for $50 delivered. The next step in this process was get some dyno results to baseline my car before proceeding with this modification. You can see all of my dyno results by clicking here. Once I received the y-pipe from Stillen, there were more logistics to work out. Since I was the first person to attempt this modification, I was trying to collect all of the necessary data to accurately quantify the results of this mod. By doing so, it would help others decide if this modification was right for them. So, I finally came up with the plan of installing just the main part of the Stillen 2-piece Y-pipe, as is normally done with CA emissions cars and taking the car to get dyno'ed again. This was followed by installing the Federal front-side exhaust manifold and the second piece of the Stillen Y-pipe. This part of the project is detailed nicely in the pics below. It was fairly straight forward with few complications. I test drove the car from it's cool state and didn't receive any check engine lights which takes care of concern #2 above. Our discussions on Maxima.org concluded that the only time I should get a check engine light would be when the car was cool, before the main cat had a chance to heat up. Luckily, the setup I have now with the relocated O2 sensors is sufficient to keep this from happening. Now a trip to the dyno shop was in order again. You can click the above link to view all of these dyno results, but here's a summary (keep in mind that these are wheel HP and my car is an automatic): initial (baseline dyno) - HP = 174 @ 6430 Torque = 171 @ 3730 after Stillen 1st pc install - HP = 187 @ 6390 Torque = 182 @ 3710 after complete install - HP = 187 @ 6600 Torque = 180 @ 3780 Before you say it looks like I lost torque with mod, take a look at the dyno plots: To summarize these results, the main gain was from the 1st piece of the Stillen Y-pipe. The second piece in tandem with the Federal emissions front-side exhaust manifold only yielded a small improvement. Output increased over 4000-6000 rpm range by only about 3 ft-lbs of torque and 3 HP. This mod did not show any improvements on the patented butt-dyno either as it was barely noticable when driving. I am pleased that this mod did work functionally (ie everything bolted up together and I didn't get any check engine lights), but I don't believe others will benefit much from this test, except for the knowledge that the front precat is not a significant restriction of our exhaust path. It was fun seeing one of my ideas through to completion, which is good because I'm uncertain whether small gains were worth the $90 I spent plus 8 hours of work (not counting this site) and I believe I counted 11 battle scars on my hands/forearms. Oh well. I guess we'll never know unless we try. This is just a side note. My car was substantially louder with the Stillen y-pipe installed. In fact, it was so much louder that I ended up removing my Greddy muffler and reinstalling the stock one (with some nice tips of course). This quieted it back down to almost stock levels. The "bees in a can" sound so many of us have heard about on Maxima.org is barely evident in my car. It appears only at high rpms or when revving the car in neutral and sounds like a slight vibration eminating from the flex section in the Y-pipe. |
If you have any questions about this mod or what's coming next, feel free to send me an email. |
2001 Nissan Maxima SE Anniversary Edition Y-Pipe/Exhaust Manifold Modification |
I decided to run the blue O2 sensor wires next to the existing red and white ones. You can see the O2 sensor at the bottom of this pic to the left of the motor mount. |
Pic #2 of the two setups. Which one do you think will flow better??? One thing to point out here is the location of the O2 sensor bungs. The CA emissions setup is on the left hand side of the exhaust manifold. The Fed setup is on the right hand side in the Stillen piece. This will require the "blue" O2 sensor wires to be lengthened. |
Pic#1 of the stock FED emissions exhaust manifold. Note the three bolts for the y-pipe. The CA emissions model has a five bolt flange that attaches directly to the front precat. |
Pic #2 of the stock FED emissions exhaust manifold. Notice that there are no O2 sensors in this manifold. There are two in the y-pipe and one after the main cat. |
Pic of the stock FED emissions exhaust manifold bolted up to the 2nd piece of the Stillen Y-pipe. |
To remove the front-side exhaust manifold, you need to remove the radiator. Look at all of the space there is now!!! You will also have to remove the heatshields surrounding the front precat. This is necessary to clear the couplings on the a/c compressor. Other than that, the removal of the exhaust manifold and front precat is pretty straight forward as long as you remove them as one unit out the top of the engine compartment. |
Pic#1 of the Federal emissions setup (w/Stillen 2nd piece) that I'm putting in next to the stock CA emissions setup with the built-in precat. Look at that BEAST! |
If you have any questions about this mod or what's coming next, feel free to send me an email. |
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Here's a pic, from under the car,of the Stillen piece installed. Now that everything was bolted in, I just needed to put my radiator back in and take her for a spin. |
1. In 2000, the 5th Gen Maxima was introduced. Their were two different emissions setups available depending on where the car was being sold... Federal and California. 2. In 2001, this was changed and all Maximas now conform to the California emissions requirements. 3. The 2000 Federal emissions setup has three O2 sensors. One located on each side of the y-pipe close to the exhaust manifold. The third is located after the main catalytic converter. 4. The CA emissions models have four O2 sensors. The initial two O2 sensors remain the same as on the federal model, except they bolt up in slightly different locations in the exhaust. The rear O2 sensor on the Federal car is replaced by two downstream O2 sensors, located behind each precat. So basically there are four O2 sensors with one located both before and after each precat in the y-pipe. 5. The rear precat in the CA emissions cars is entirely located within the y-pipe, so the rear exhaust manifold on the Federal and CA cars is identical. The front precat is somewhat built into the exhaust manifold. This is another difference between the Federal and CA cars. These differences are further illustrated in the pics below. 6. When buying an aftermarket y-pipe, most places make two versions... one Federal... one CA. The difference is that on the Federal model, the y-pipe runs all the way up to the exhaust manifold on both sides of the engine. On the CA model, the y-pipe runs to the exhaust manifold on the rear side (just like the Fed model), but on the front side, it only runs to a flange located after the front precat. Therefore the stock front manifold and precat remain intact. This fact alone will reduce the performance gain realized by installing an aftermarket y-pipe, when compared to a Federal model. Stillen has done something a little different. They have made a two piece y-pipe that will fit either a Federal or CA emissions Maxima. The main piece is made to bolt up to a CA emissions vehicle. The second piece goes where the front precat is located on the CA emissions vehicle and is flanged to bolt up to the Federal front-side exhaust manifold. With this basic understanding, it is relatively easy to see where I came up with the following idea. One of the main restrictions in the stock y-pipe is the precats. Since the CA y-pipe only replaces one precat it is not as beneficial as the Federal y-pipe. So, why not try to "convert" my car from CA emissions to Federal emissions and use the Federal y-pipe. Now, by "convert", I mean the following: 1. Do whatever is cost-effective to gain the lost HP inherent in the CA emissions models. 2. Do so without generating any check engine lights. 3. Setup the car so it will still pass emissions testing. With this in mind, I decided to give it a go. The first step was to relocate the O2 sensors to after the main cat (similar to the Federal car, except there are two of them). This managed to keep the ECU happy, eliminating concern #2 above. Since the main cat remained in the exhaust system, it should still pass emissions testing in AZ providing that the car is already up to normal operating temperature. This O2 sensor relocation can be viewed by clicking here. The next step was to order a Federal front-side exhaust manifold. The exhaust manifold was easier to find that I had anticipated. I checked with my local Nissan dealership's parts dept and found that the part number was the same for all Maximas from '95-'00. This made my search much easier. I visited Car-Part.com and searched for the Federal emissions front-side (actually called left-hand side) exhaust manifold and found many places with this part. I bought mine from AA Auto in Little Rock, AK for $50 delivered. The next step in this process was get some dyno results to baseline my car before proceeding with this modification. You can see all of my dyno results by clicking here. Once I received the y-pipe from Stillen, there were more logistics to work out. Since I was the first person to attempt this modification, I was trying to collect all of the necessary data to accurately quantify the results of this mod. By doing so, it would help others decide if this modification was right for them. So, I finally came up with the plan of installing just the main part of the Stillen 2-piece Y-pipe, as is normally done with CA emissions cars and taking the car to get dyno'ed again. This was followed by installing the Federal front-side exhaust manifold and the second piece of the Stillen Y-pipe. This part of the project is detailed nicely in the pics below. It was fairly straight forward with few complications. I test drove the car from it's cool state and didn't receive any check engine lights which takes care of concern #2 above. Our discussions on Maxima.org concluded that the only time I should get a check engine light would be when the car was cool, before the main cat had a chance to heat up. Luckily, the setup I have now with the relocated O2 sensors is sufficient to keep this from happening. Now a trip to the dyno shop was in order again. You can click the above link to view all of these dyno results, but here's a summary (keep in mind that these are wheel HP and my car is an automatic): initial (baseline dyno) - HP = 174 @ 6430 Torque = 171 @ 3730 after Stillen 1st pc install - HP = 187 @ 6390 Torque = 182 @ 3710 after complete install - HP = 187 @ 6600 Torque = 180 @ 3780 Before you say it looks like I lost torque with mod, take a look at the dyno plots: To summarize these results, the main gain was from the 1st piece of the Stillen Y-pipe. The second piece in tandem with the Federal emissions front-side exhaust manifold only yielded a small improvement. Output increased over 4000-6000 rpm range by only about 3 ft-lbs of torque and 3 HP. This mod did not show any improvements on the patented butt-dyno either as it was barely noticable when driving. I am pleased that this mod did work functionally (ie everything bolted up together and I didn't get any check engine lights), but I don't believe others will benefit much from this test, except for the knowledge that the front precat is not a significant restriction of our exhaust path. It was fun seeing one of my ideas through to completion, which is good because I'm uncertain whether small gains were worth the $90 I spent plus 8 hours of work (not counting this site) and I believe I counted 11 battle scars on my hands/forearms. Oh well. I guess we'll never know unless we try. This is just a side note. My car was substantially louder with the Stillen y-pipe installed. In fact, it was so much louder that I ended up removing my Greddy muffler and reinstalling the stock one (with some nice tips of course). This quieted it back down to almost stock levels. The "bees in a can" sound so many of us have heard about on Maxima.org is barely evident in my car. It appears only at high rpms or when revving the car in neutral and sounds like a slight vibration eminating from the flex section in the Y-pipe. |
