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OK, if any of you folks are like me, you probably do a search in eBay on "Nissan Murano" every now and then just to see what pops up for sale. Well, there is this new thing on there called, "Nissan Murano Sensor Mod Add 20+ HP". This little gizmo reminds me of the "Cap Accessory Improves Look" item (essentially a plastic cap you can probably buy at a hardware store). The sensor mod is going for $9 (the cap kit is $4.95 for the curious). The kit probably consists of a resistor and instructions.

Curious, I searched the web for 'intake sensor modification' and found this site that describes how the modification is done (though not on a Murano):

http://sherb.nismo.org/howto/intake_air_temp.html

Basically, a resistor is installed to effectively alter the voltage that the ECU reads from the air intake sensor. This makes the ECU think the incoming air is cooler than it is. The ECU makes the fuel system pump more fuel in the intake creating more power. The result is probably noticable, but at the cost of burning more gas.

I don't know where on the Murano you would install this nor I would I want do it because of the possible repercussions in the engine (fouled plugs, excessive unburned fuel, along with a serious drop in gas mileage).
 

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Sorry for the late reply. I've been thinking on how to answer this in depth. For the short version see this thread.

Homer hit the nail on the head. The engine is an air pump, making it breath better is where you get performance increases. Always has been, and as far as I can tell always will be.

Over the past several years, several changes have been made in increasing complexity. These changes were primarily necessitated by environmental protection laws, which made the manufacturers dig deeper to provide performance and meet EPA restrictions.

But all through that, decreasing the air to fuel mixture ratio to a rich condition (less than 14.7:1 == stoichiometric) is good for acceleration but you don't want to run rich at constant speed. Plugs foul in rich mixtures and then start to perform poorly and when that happens your back to no HP gain or even loss.

Now I'm not certain of the sequence of technology and my memory has a lot of holes and this is by no means complete, but will take a stab. People chime in and correct me, I know I'm missing a lot here, perhaps even misstating some things. I learned this stuff 15 years ago and am going by poor memory. It's really a lot more complicated than this...

O2 (oxygen) sensors and catalytic converters. The catalytic converter is typically a honeycomb ceramic impregnated with a catalyst (I believe at one time it was platinum?). As the catalytic heats up it burns off the excess hydrocarbons (unburned fuel like running rich). Most O2 sensors used back then and I think still widely used today toggle around .5 volts indicating rich or lean air fuel mixtures, see note***. The key is they toggle, they don't give a reading that can be interpreted as a precise mixture ratio. So these sensors are tied to computers that are essentially a bang-bang controller (with time averaging) that adjusted carburetors or injectors fuel flow. So if the O2 sensor detected a lean condition, the computer would tell the carb or injectors to allow more fuel, etc. But this is no use for accelerating. During acceleration, the computer would go to a preset rich air fuel mixture. Ignition timing needs to be advanced too, and you detect the operator wants to accelerate by vacuum, throttle position sensors, Wide Open Throttle WOT sensors versus rpm sensors etc).

Obviously that helped reduce the amount of unburned hydrocarbons to a great degree, but the allowable limits were tightened. So, enter air temperature (ambient outside) and flow sensors (flapper doors). Air temperature and flow was used as a guide to determine air mass. If the air mass was greater, then the fuel had to be adjusted accordingly...but for acceleration only, the O2 still serves for constant speed driving. So the "fuel map" was developed that was basically a table or algorithm that said for this mass use that fuel. That way, the car would produce less hydrocarbons over a wider range of air temperatures. MAP sensor plays in here too as well as altitude sensors etc. Air temperature and flow is one means of determining air mass but it does not take into account other factors such as barometric pressure, altitude, and humidity, all of which change air mass/density and the optimum (performance versus environment) rich air fuel mixture for accelerating.

So obviously, that helped reduce hydrocarbons but we love our environment so...stricter standards again. Now enter the Mass Air Flow (MAF) sensor. Which to me is essentially a hot wire anemometer. You pass current through a wire as the air flows over the wire and cools it (mass effect), you have to send in more current to keep the wire hot. So the MAF directly determines the air temperature, flow and most importantly mass. So once again it looks at the fuel map table or algorithm and computes the right amount of fuel to inject for acceleration, all things considered (performance and environment).

Ah but we're not done...we love our environment but we also love performance. The MAF sensor and fuel map does good but the map was fixed and does not take into account other things, not sure of all but examples to me would be the gas itself, differences in engines and engine wear. So the fuel map basically has to change or adapt. Enter adaptive controls one I'm familiar with is called the Kalman filter. It allows the computer to sense through it's MAF, O2, temperature, and various sensors and adjust the fuel maps accordingly. This is part of the reason why the ECU for the Z has been so difficult to crack and why performance mod attempts have resulted in initial dyno run small gains but then back to no gains or even loss on subsequent runs. IT LEARNS!

So, I suspect highly, but don't know for sure, that this resistor trick that used to work in the old days won't after about 20 minutes (what we have seen in the Z forums as the ECU "learning curve"). And worse, might even throw a code or the Check Engine Soon light. In any event, you don't want to run rich forever, just for acceleration. Even today, constant speed air fuel ratio mixture is still determined by the O2 sensor(s).

***There are some O2 sensors that yield measurable readings that equate to an air fuel ratio, not just bang-bang. But these sensors used to be really expensive. I suspect they still are and aren't used to a large extent. But before the mass air flow stuff, you could build a circuit around one of these to set your air fuel ratio and fool the computer. I highly suspect that won't even work today.

Hydrocarbons are only part of the environmental story but is what you talk about when running rich as this $9 mod suggests it does ... :bsflag: .

As the air to fuel ratio increases you run "lean". That is greater than 14.7:1 or stoichiometric. In lean conditons the engine produces other bad things, if memory serves NOX??? At any rate, the curves oppose each other and the lowest emissions considering hydrocarbons and NOX is right at stoichiometric. So all things considered, the objective of the computers is to run as close to 14.7:1 as possible for all conditions and variations. Meaning running lean also is a bad thing. Now running lean in extreme cases can cause severe engine damage, not just spark plug. As the mixture gets lean, the spark plug can't ignite the mixture as well and results in non-uniform combustion inside the chamber and can create hot spots that can burn through the piston (doesn't ignite the whole chamber). But slightly lean mixtures can produce better gas mileage depending on a whole lot of stuff I forgot. I do remember the pre-combustion chamber though. Essentially a small combustion chamber that was run slightly rich and then expelled itself into a large combustion chamber that was run slightly lean. Resulted in great gas mileage and the hydrocarbons were low but the NOX ouput would be higher.

I heard a story (perhaps urban legend, never was able to confirm this) from a friend about the pre-combustion chamber. Honda had developed a pre-combustion chamber engine, mass produced it, sent it to the states, congress passed a law before the cars left the boats, honda turned the boats around, took the engines out and put in engines without pre-combustion chambers but WITH catalytic converters. Anyhow, thought it was interesting even if it's urban legend!

Ok you folks with better memories and knowledge than I have...chime in here and correct me.
 

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Ah, I think you got it all, alright.
You CAN help the MAF a bit, but generally it isn't worth it.
But if the MAF is restricted (sometimes with a screen. sometimes with plastic extrusions in the MAF chamber itself) you can eke out a tiny bit of HP. But, screw it up and you are out <>$300. And it will only help if the balance of Gozinta vs Gozouta needs a little help on the Gozinta side.

Once you have your Borla and your cold air induction and your ............brain fart.............catalytic............then "probably" the best value thing you can do is talk to Hypertech about a chip (If you are lucky) or a "new" ECU. There is another outfit in Tulsa (can't remember the name) that does nice chip work. Would you believe that is who I used for both my Mustang and my Corvette...........Getting old sucks. The only thing it is better than.......... is not getting old........

BTW, The Catalytic I couldn't think of is Random Technologies. That's if you want to be legal or if you are in a state that checks that kind of thing. Otherwise, if you are an outlaw you can just put a Catalytic "test pipe" on there.

After that it gets silly. You need to get into cams and other expensive stuff and when you do that, you have to decide where do you want the power and where do you want to give it up.
Because now you are going into the land of "peaky" HP and Torque.
I was in all that stuff for a time and you just can't believe how that stuff bores me these days.


I haven't heard of Jacobsen since I bought an ignition system from him many years ago. It had a fancy name, long forgeotten, but it was a capacitive discharge system that needed points to fire it.
Put it on a dirt race car in the early seventys.

I never heard that story about Honda and the precombustion engines and the boat.
Shoot, I never heard of precombustion chambers.

Now I'm ready to talk some Murano and leave this Quest for HP to the kids. The Murano already has the proper mix of power and height to scare the bejeesus outa me (and I usta race grand national cars back in the day), blush, blush.

Homer
 

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There are probably things that can be done to increase output (but I agree with others that the air sensor mod belongs with tornadoes, $20 electric 'turbochargers' a.k.a bilge-blowers, and gas-line magnets in the rip-off hall of fame).

I have to wonder if folks searching for more power (I saw a thread on using theNismo 350Z muffler/exhaust somewhere) have considered that the jury is still out re: long term reliability of the CVT even at STOCK power levels? My hat's off to those willing (and with deep enough pockets) to explore this territory.
 

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LOL! yeah, ripoff hall of famers...

The CVT has some margin since the MO has a rated tow capacity of 3500lbs, but we still don't know what it is. But a 6HP increase (on the Z) should be no problem...that is if you want to spend $1000+ for the Nismo Z catback! By my way of thinking, an awfully expensive stainless steel muffler.:31:

On the otherhand, I tend to agree, the MO has plenty of power as is. So does the Z...but then you can never have enough power! :D

But that is why we mod our cars. The grass is always greener, to be different, to customize, to push the limits. So to each their own, as it should be. I just find it a fascinating topic.
 

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Believe me, I'm a Tim Allen disciple when it comes to "more power". I am in a constant quest for more power with my Typhoon. 12's, anyone? On street tires, with all luxury conveniences intact? For under $2k in mods? And fragged tranny's are a fact of life in the Syclone/Typhoon world, for sure. But, there have been many explorers before me, so I know:
- what to do to stave off failure
- what it will take to break my Typhoon trans
- who to go to for a bulletproof rebuild/kit
- what it will cost to make it bulletproof at the power level I want.

The folks that first explored that turf spent some big bucks, only to have mutiple rebuilds fail almost immediately. It took a tranny expert buying a Syclone and using his truck as a test bed for new ideas for the Sy/Ty trans situation to stabilize.

CVT experts are gonna have to be grown from scratch....
 

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Sorry for the late reply. I've been thinking on how to answer this in depth. For the short version see this thread.

Homer hit the nail on the head. The engine is an air pump, making it breath better is where you get performance increases. Always has been, and as far as I can tell always will be.

Over the past several years, several changes have been made in increasing complexity. These changes were primarily necessitated by environmental protection laws, which made the manufacturers dig deeper to provide performance and meet EPA restrictions.

But all through that, decreasing the air to fuel mixture ratio to a rich condition (less than 14.7:1 == stoichiometric) is good for acceleration but you don't want to run rich at constant speed. Plugs foul in rich mixtures and then start to perform poorly and when that happens your back to no HP gain or even loss.

Now I'm not certain of the sequence of technology and my memory has a lot of holes and this is by no means complete, but will take a stab. People chime in and correct me, I know I'm missing a lot here, perhaps even misstating some things. I learned this stuff 15 years ago and am going by poor memory. It's really a lot more complicated than this...

O2 (oxygen) sensors and catalytic converters. The catalytic converter is typically a honeycomb ceramic impregnated with a catalyst (I believe at one time it was platinum?). As the catalytic heats up it burns off the excess hydrocarbons (unburned fuel like running rich). Most O2 sensors used back then and I think still widely used today toggle around .5 volts indicating rich or lean air fuel mixtures, see note***. The key is they toggle, they don't give a reading that can be interpreted as a precise mixture ratio. So these sensors are tied to computers that are essentially a bang-bang controller (with time averaging) that adjusted carburetors or injectors fuel flow. So if the O2 sensor detected a lean condition, the computer would tell the carb or injectors to allow more fuel, etc. But this is no use for accelerating. During acceleration, the computer would go to a preset rich air fuel mixture. Ignition timing needs to be advanced too, and you detect the operator wants to accelerate by vacuum, throttle position sensors, Wide Open Throttle WOT sensors versus rpm sensors etc).

Obviously that helped reduce the amount of unburned hydrocarbons to a great degree, but the allowable limits were tightened. So, enter air temperature (ambient outside) and flow sensors (flapper doors). Air temperature and flow was used as a guide to determine air mass. If the air mass was greater, then the fuel had to be adjusted accordingly...but for acceleration only, the O2 still serves for constant speed driving. So the "fuel map" was developed that was basically a table or algorithm that said for this mass use that fuel. That way, the car would produce less hydrocarbons over a wider range of air temperatures. MAP sensor plays in here too as well as altitude sensors etc. Air temperature and flow is one means of determining air mass but it does not take into account other factors such as barometric pressure, altitude, and humidity, all of which change air mass/density and the optimum (performance versus environment) rich air fuel mixture for accelerating.

So obviously, that helped reduce hydrocarbons but we love our environment so...stricter standards again. Now enter the Mass Air Flow (MAF) sensor. Which to me is essentially a hot wire anemometer. You pass current through a wire as the air flows over the wire and cools it (mass effect), you have to send in more current to keep the wire hot. So the MAF directly determines the air temperature, flow and most importantly mass. So once again it looks at the fuel map table or algorithm and computes the right amount of fuel to inject for acceleration, all things considered (performance and environment).

Ah but we're not done...we love our environment but we also love performance. The MAF sensor and fuel map does good but the map was fixed and does not take into account other things, not sure of all but examples to me would be the gas itself, differences in engines and engine wear. So the fuel map basically has to change or adapt. Enter adaptive controls one I'm familiar with is called the Kalman filter. It allows the computer to sense through it's MAF, O2, temperature, and various sensors and adjust the fuel maps accordingly. This is part of the reason why the ECU for the Z has been so difficult to crack and why performance mod attempts have resulted in initial dyno run small gains but then back to no gains or even loss on subsequent runs. IT LEARNS!

So, I suspect highly, but don't know for sure, that this resistor trick that used to work in the old days won't after about 20 minutes (what we have seen in the Z forums as the ECU "learning curve"). And worse, might even throw a code or the Check Engine Soon light. In any event, you don't want to run rich forever, just for acceleration. Even today, constant speed air fuel ratio mixture is still determined by the O2 sensor(s).

***There are some O2 sensors that yield measurable readings that equate to an air fuel ratio, not just bang-bang. But these sensors used to be really expensive. I suspect they still are and aren't used to a large extent. But before the mass air flow stuff, you could build a circuit around one of these to set your air fuel ratio and fool the computer. I highly suspect that won't even work today.

Hydrocarbons are only part of the environmental story but is what you talk about when running rich as this $9 mod suggests it does ... :bsflag: .

As the air to fuel ratio increases you run "lean". That is greater than 14.7:1 or stoichiometric. In lean conditons the engine produces other bad things, if memory serves NOX??? At any rate, the curves oppose each other and the lowest emissions considering hydrocarbons and NOX is right at stoichiometric. So all things considered, the objective of the computers is to run as close to 14.7:1 as possible for all conditions and variations. Meaning running lean also is a bad thing. Now running lean in extreme cases can cause severe engine damage, not just spark plug. As the mixture gets lean, the spark plug can't ignite the mixture as well and results in non-uniform combustion inside the chamber and can create hot spots that can burn through the piston (doesn't ignite the whole chamber). But slightly lean mixtures can produce better gas mileage depending on a whole lot of stuff I forgot. I do remember the pre-combustion chamber though. Essentially a small combustion chamber that was run slightly rich and then expelled itself into a large combustion chamber that was run slightly lean. Resulted in great gas mileage and the hydrocarbons were low but the NOX ouput would be higher.

I heard a story (perhaps urban legend, never was able to confirm this) from a friend about the pre-combustion chamber. Honda had developed a pre-combustion chamber engine, mass produced it, sent it to the states, congress passed a law before the cars left the boats, honda turned the boats around, took the engines out and put in engines without pre-combustion chambers but WITH catalytic converters. Anyhow, thought it was interesting even if it's urban legend!

Ok you folks with better memories and knowledge than I have...chime in here and correct me.
Hi,

I see you are very familiar with air/gas mixture topic. I recently imported an US 0'4 Murano in Europe. I installed LPG system (which is quite popular in Europe, 1 liter is double of the price of regular fuel) After while all 3 cats went bad (which is normal as the exhaust gas is completely different) so I removed the "honeycomb" and put back the shell. (the LPG is considered as ecological fuel so it can pass the emission tests)

Now let's go to my problem/question. The LPG system is set to read air/gas mixture ratio from Mo's ECU. But the ECU is confused because of getting wrong info from O2 sensors (no cats) and the end result is the higher fuel consumption and loss of power @ higher RPM.
The LPG system can be manually adjusted and it is possible to set preferred air/gas mixture ratio. Do you know what is normal ratio (when it has all cats and everything works just fine) at this type of Mo's?
NOTE: Usually the car's normal petrol and LPG ratio should be the same.

Tnx a lot in advance.
 
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