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Discussion Starter #1

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The Member
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JWT

I definately have no regrets that i got one ;)
 

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My MO's faster than yours
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Did you test it before or after the ECU had time to adapt to the new air flow? Or did you reset your self? After my install I left the neg. bat cable off for a good 30 minutes. And restarted the car and idled for another good 10-15 minutes. Youll have to redo allyour saved radio settings...but it was sure worth it..
 

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Discussion Starter #4
You're right, I forgot to mention that, I reset the ECU after switching back to some decent fuel. I didn't want any learned ignition timing info still running around the ECU.
 

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How does one reset the ECU? Only by disconnecting the ground on the battery?
 

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Discussion Starter #6
Yeah. I unplugged it for a few hours.

Some cars have small capacitor back-ups for volitile computer memory for when changing batteries which is why I left it unplugged for so long, though I honestly have no idea if the Mo has this or how long is necessary.
 

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SHIFT_FASTER
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I don't think the numbers you get after resetting the computer are valid. These numbers represent the initial values programmed for the computer.

The computer works like this:
1. read mass airflow sensor (MAF).
2. look up the cell in fuel map table corresponding to current RPMs and incoming air mass.
3. inject amount of fuel specified in fuel map cell.
4. read oxygen sensor in exhaust. if air-fuel ratio not correct, adjust cell in fuel map table.

The fuel map will contain reasonable values for a completely stock Murano. If you suddenly add more air (ie intake), and reset the computer, the fuel map has not had time to adjust to the additional air. This will cause the engine to run leaner (more air) until the various cells have all been updated. This will give you more power than the optimal fuel map values, because the optimal values take into account additional fuel needed for cooling purposes, etc.

To make the readings closer to real world conditions, I would do the following, once without the intake, and once with the intake:

1. Reset computer
2. Drive in a variety of ways for 200 miles
3. Measure the performance

Unfortunately, this brings ambient factors such as temperature, into play, as it's more difficult to match the conditions when you're waiting a few days or weeks between measurement. All in all, it's pretty difficult to prove any real-world numbers on such a complicated system.
 

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Tyler,

I received my JWT CAI but was planning to install it next weekend. Are you saying that I should just install and not reset the ECU?
 

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Discussion Starter #9
I really doubt resetting the ECU has anything to do with the CAI. The airflow sensor sees how much air is coming in and adds the apropriate amount of fuel, and if you give it more air then it sees more. It's not like we're fooling the ECU/MAS by giving it unmetered air, or pegging out the MAS at it's peak voltage. For my test, resetting the ECU was purely to purge any fuel timing information from the 87 octane gas I had been running, I see no reason that you would need to do the same, especially since the car will re-learn with a new tank of fuel anyway given time.
 

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Mr. 3 K, 3/3/5. 5K,10/5/7
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I'm with you MightyMo Grip :D
 

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MightyMo said:
I really doubt resetting the ECU has anything to do with the CAI. The airflow sensor sees how much air is coming in and adds the apropriate amount of fuel, and if you give it more air then it sees more. It's not like we're fooling the ECU/MAS by giving it unmetered air, or pegging out the MAS at it's peak voltage. For my test, resetting the ECU was purely to purge any fuel timing information from the 87 octane gas I had been running, I see no reason that you would need to do the same, especially since the car will re-learn with a new tank of fuel anyway given time.
Let me try this a different way: the airflow sensor does not give an absolute value, it gives a relative value. That value is checked by the oxygen sensor, and the base value is updated. No you aren't fooling the sensor, but that sensor is not the only one that affects the amount of fuel added.

The computer continually updates the fuel tables to adjust for changes in sensor function and various other factors, in order to keep the engine running at the air-fuel ratio specified for the current operating conditions. If you clear the updated values, then you go back to the start again. It will take time for the values to be updated to the point where the engine is running at the specified air-fuel ratio.

Running the engine leaner will give more power, but cause more heat. If you clear the computer, you will cause the engine to run very slightly leaner. We're talking a barely noticeable amount leaner, not enough to cause problems. Just adding the intake without resetting the computer will also cause the engine to run slightly leaner for a while. The computer will try to fix this by updating the fuel tables. This will occur slowly enough that you won't be able to notice the gradual loss of power.

I'm not saying the intake won't add power. I'm a firm believer that the values quoted (5-8hp at the wheels) are realistic. I'm just saying if you compare the stock air filter to the pop charger, you'll notice a much bigger difference if you reset the computer, but that difference won't last.

In other words, no, I wouldn't bother resetting the computer when you add the charger... in fact, I didn't reset mine. Resetting the computer won't make a difference in the end.

Sorry if that isn't clear, I can't do any better than that.
 

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Discussion Starter #13
That makes some sense. Guess I'll just have to go do another test run after a few tanks of fuel to see :D
 

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Tyler_Canada said:


Let me try this a different way: the airflow sensor does not give an absolute value, it gives a relative value. That value is checked by the oxygen sensor, and the base value is updated. No you aren't fooling the sensor, but that sensor is not the only one that affects the amount of fuel added.

The computer continually updates the fuel tables to adjust for changes in sensor function and various other factors, in order to keep the engine running at the air-fuel ratio specified for the current operating conditions. If you clear the updated values, then you go back to the start again. It will take time for the values to be updated to the point where the engine is running at the specified air-fuel ratio.

Running the engine leaner will give more power, but cause more heat. If you clear the computer, you will cause the engine to run very slightly leaner. We're talking a barely noticeable amount leaner, not enough to cause problems. Just adding the intake without resetting the computer will also cause the engine to run slightly leaner for a while. The computer will try to fix this by updating the fuel tables. This will occur slowly enough that you won't be able to notice the gradual loss of power.

I'm not saying the intake won't add power. I'm a firm believer that the values quoted (5-8hp at the wheels) are realistic. I'm just saying if you compare the stock air filter to the pop charger, you'll notice a much bigger difference if you reset the computer, but that difference won't last.

In other words, no, I wouldn't bother resetting the computer when you add the charger... in fact, I didn't reset mine. Resetting the computer won't make a difference in the end.

Sorry if that isn't clear, I can't do any better than that.
The 02 sensor is so much further downstream in the situation that it effects engine performance more for the sake of emissions than performance.

Resetting the ECU is good, however the ECU will adapt within a few miles of driving so its a moot point whether or not you do it.

That "CAI" might give you better throttle response off the line and higher HP but don't expect any performance gains in city driving. It'll be sucking in hot air until enough outside air evacuates the hot air being sucked in by the filter.

That being said, I plan on putting a Z-tube + BMC CDA made for the 350Z onto my Murano when I get it. It retains the beneficial effects of a high flow filter yet is completely shielded from any effects of high heat. I plan on hooking the tubing up to the stock air dam since there doesn't seem to be any real issues with its location. The Z-tube seems to be much smoother than the stock intake thus reducing the amount of turbulence (slowing down of air) in the intake.

www.bmcairfilters.com
 

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RE: "That being said, I plan on putting a Z-tube + BMC CDA made for the 350Z onto my Murano when I get it. It retains the beneficial effects of a high flow filter yet is completely shielded from any effects of high heat. I plan on hooking the tubing up to the stock air dam since there doesn't seem to be any real issues with its location. The Z-tube seems to be much smoother than the stock intake thus reducing the amount of turbulence (slowing down of air) in the intake."

Can you elaborate on the BMC CDA (what is it?) and if you install a Z-tube will you document?

Thanks
 

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Mr. 3 K, 3/3/5. 5K,10/5/7
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I would love the little more punch on WOT. However (someones favorite word) I don't want any more noise, I like quite inside, ergo my added external and internal sound deading. Anybody got a quite CAI.
 

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GripperDon said:
I would love the little more punch on WOT. However (someones favorite word) I don't want any more noise, I like quite inside, ergo my added external and internal sound deading. Anybody got a quite CAI.
BMC CDA

www.bmcairfilters.com

use the one for a 350Z

You won't have heatsoak issues. It will always draw in cold air, and you don't run the risk of sucking in water. Very highly regarded in the "real" racing world (not this import tuner fast and the furious stuff). You can find BMCs or Carbonios on racespec audi S4's RS4s, M3's & etc. Not cheap though. $270.

Either that or just get a drop-in filter if you believe in those. (I don't) Haven't been able to check out a stock airbox but from the looks of a few pics, it doesn't seem to be too restrictive.

Dave
 

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DAVE

Can you tell me more as to what a "drop in filter" is as compared to the OEM Murano filter. Thanks for the response, I'll look at the link you provided.
 

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GripperDon said:
DAVE

Can you tell me more as to what a "drop in filter" is as compared to the OEM Murano filter. Thanks for the response, I'll look at the link you provided.
Drop in filter = K&N, ITG, BMC (stock replacement filters made of oiled cotton gauze or oiled foam)

Many people buy them, many people believe in them. I do not however, but i'm giving you all the options. Here's something to read about them.

http://www.bobistheoilguy.com/airfilter/airtest1.htm

I will say though that starting off the line, there is a marginal improvement in airflow, however once the car is moving, the difference in flow between a clean stock filter and a K&N is negligible.

Basically, just change your paper airfilter more frequently. And if you're inclined to, drill a 2" hole in your airbox and run tubing down to the lower grille to ensure little restriction pre-filter.

My thoughts are that if you're looking for some WOT punch, an exhaust is in order. From the looks of the stock exhaust, its uber restrictive in the way that its designed and the piping is way too small. Perhaps that's how they managed to detune the engine down to 245 HP. By freeing the restriction, you then up the HP/TQ which could place added stress on the CVT.

It seems like for the most part, the intake is the least of the VQ engine's worries on the Murano. I only plan on upgrading the intake because I plan on getting some custom work done to the exhaust if possible.

Its kinda ridiculous that 6 months before I even get it, I have all my mods planned out. Either way, I'm thinking about just increasing the diameter of the exhaust marginally after the third cat while still mainting two mufflers. I haven't done much muffler research to be honest, but I'll be looking for some nice quiet ones. I doubt it will be worth it, but i'll have a lot of $$$ to throw around after I part out on my Passat.

Dave
 

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Mr. 3 K, 3/3/5. 5K,10/5/7
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Wonderful reply, thank you very much, I look into all this further :D
 
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