I have a couple of questions if anyone knows the answer... I just installed a Stillen exhaust and a K&N airfilter in my 2007 M35x. MUCH more power... However, seem to get worse mileage based on the computer. (Only used two tanks of gas so far). Now I agree I am driving it a bit harder, so maybe not the most efficient, but based on the increase of horsepower, I would assume an increase of mileage. Then I started thinking... Maybe the car computer is based on some kind of "algorithm", i.e. if this much throttle, then this much mileage, etc... and not a true measure of distance and fuel consumption.
Any thoughts?
The second question, is whether or not to get the computer re-mapped. I watched an episode recently of Wheeler Dealers, and they did the same upgrade to a suburu. After the mod, they dyno it and it is at something like 204 horsepower, (or something like that), and then remap it and the new HP reading is like 240....
Any input on this would be appreciated. Does it hurt the car any if I don't remap it? If I do, is it harder on the engine, even though only used for in town and highway?
MPG Algorithm
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szh
- Posts: 15932
- Joined: Tue Jul 23, 2002 12:54 pm
- Car: 2018 Tesla Model 3.
Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
Re: MPG Algorithm
Um ... can't comment on the rest of the post, but you should understand the risk of using an oiled K&N air filter with the hot-wire MAF sensors used by Nissan/Infiniti. Please do a search on the outcomes of doing this before continuing to use it. The relatively small gain in HP is not worth it, in my opinion. 
It is best to change stock air filters more often ...
Z
It is best to change stock air filters more often ... Z
Re: MPG Algorithm
i dont see any reason for not using the K&N Filter! in every car i owned i kept the K&N Drop ins! and no problems!szh wrote:Um ... can't comment on the rest of the post, but you should understand the risk of using an oiled K&N air filter with the hot-wire MAF sensors used by Nissan/Infiniti. Please do a search on the outcomes of doing this before continuing to use it. The relatively small gain in HP is not worth it, in my opinion.
Z
even i n my m35x am using it now for about 4 months with no problems at all! in my Tribute for 2 years i never changed it and no problems! and yes i got a sensor in the Tribute Intake system!
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The00Dustin
- Posts: 1041
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- Location: Bloomington, IN
Re: MPG Algorithm
K&N posts tests on their website saying the alleged problem doesn't exist. They also suggest that you can send them a MAF and they have yet to see one where analysis actually showed the alleged problem to be the cause. I don't know whether or not the problem exists or not, but I do know people do stupid things and then lie about them because they don't want to accept responsibility, so I imagine if it has ever happened, it could easily have been caused by improperly replenishing the filter. I also imagine that dealerships are more than happy to blame anything aftermarket instead of doing a warranty repair regardless of the fact that the law says they have to prove it, and most people don't fight them on it. However, all of this is moot if the stock air filter actually catches more particles without significantly reducing airflow, and it seems like I read that to be the case (from someone on this forum, which doesn't necessarily make it fact), at least for the VK45DE.
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szh
- Posts: 15932
- Joined: Tue Jul 23, 2002 12:54 pm
- Car: 2018 Tesla Model 3.
Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
Re: MPG Algorithm
The choice remains clearly yours to make!
The general experience with hot-wire MAF systems (as used in Nissan engines) is that micro-particles of oil that will get into the airstream - regardless of how "dry" you think you have the K&N filter - and will eventually carbonize onto the heated wire of the MAF and cause problems with drivability and engine performance.
This does take time, it is not instantaneous unless over-oiled. However, if you search NICO for this issue, we do have people who have reported this issue.
In my case, I keep my cars a long, long time (bought my 2003 M45 new back in September of 2003) and don't want long-term issues that I create - particularly with something where the change is likely to be mostly unnoticeable (unlike adding a Turbo or Super-charger - which I would love to find inexpensively for my old M45 engine). So, it is safer and simpler in the long run to just replace the air filter more often (for me this means 10k - 12k miles between air filter changes).
Again, if you choose to use the K&N anyway, no one is going to stop you from doing so!
Z
The general experience with hot-wire MAF systems (as used in Nissan engines) is that micro-particles of oil that will get into the airstream - regardless of how "dry" you think you have the K&N filter - and will eventually carbonize onto the heated wire of the MAF and cause problems with drivability and engine performance.
This does take time, it is not instantaneous unless over-oiled. However, if you search NICO for this issue, we do have people who have reported this issue.
In my case, I keep my cars a long, long time (bought my 2003 M45 new back in September of 2003) and don't want long-term issues that I create - particularly with something where the change is likely to be mostly unnoticeable (unlike adding a Turbo or Super-charger - which I would love to find inexpensively for my old M45 engine). So, it is safer and simpler in the long run to just replace the air filter more often (for me this means 10k - 12k miles between air filter changes).
Again, if you choose to use the K&N anyway, no one is going to stop you from doing so!
Z
Re: MPG Algorithm
To the original question, you will not be able to map your fuel economy easily. At the simplest, the maunfacturer will map fuel consumption based upon throttle position and engine rpm. That chart looks a lot like a topographical map of your consumption in volume per unit time. MPG then is obviously also based upon what gear you are in - since that will determine vehicle speed for a given engine speed. It is complicated to map that on your own.
With substantial modifications it is essential that you get the computer remapped. However, for most people with bolt on mods it is a waste. The justification for chips and simple changes is that Nissan left horsepower on the table and you just need to pick it up (or be smarter than they were). Don't bet on that. There are engineering and commercial reasons for the OEM sacrificing easy power but I don't see any on the M35.
With substantial modifications it is essential that you get the computer remapped. However, for most people with bolt on mods it is a waste. The justification for chips and simple changes is that Nissan left horsepower on the table and you just need to pick it up (or be smarter than they were). Don't bet on that. There are engineering and commercial reasons for the OEM sacrificing easy power but I don't see any on the M35.
Re: MPG Algorithm
Well, thanks for everyone's input, I appreciate the differing views. Keith