I have been using the search button like nobody's business, trust me. I want to read everything i can before i jump into turboing my daily driver, but just for knowledge's sake...
to my understanding....An FMU is (to most) just another way to say RRFPR (rising rate fpr). A ratio of 8:1 or 10:1 would suggest that for each additional psi of boost, the fuel pressure is increased by 8 or 10 times as much. Is this correct? Does this also imply that since the stock FMU is set at 1:1 that the stock boost is always just 1psi? i know there is a stock boost controller ( i had to replace it recently- $$$ from the factory). does it just center the boost at 1psi or does it encounter increasing boost at minimal levels but so little that a 1:1 fmu is accurate enough to work.
Second, how much pressure can a stock fuel rail accept? i cant seem to find the answer to this one. And correct me if my logic is wrong because i am no mechanic... but with a turbo setup, making up to 7-8 psi, an FMU of 8:1 would (according to my math) make for 56-64 psi on the fuel side at maximum boost... correct? or is it not that simple. If that is spread out over four injectors, it should be around 14-16 psi per injector. Again.. is it not this simple? What that translates to in metric units (cc) i dont know. But from the talks of users of this setup, the stock injectors and the fuel rail can handle this with no problem. Im just wondering (just for the sake of wondering) how this matches up with the math of the issue.
Lastly, Im a retard (no pun intended) when it comes to timing. Why is it necessary to adjust timing above the 8psi mark? could someone explain that... I would think it has to do with the backpressure created by the turbo that slows the cycle of the cylinder so much that firing a spark at normal timing would be too early and cause... would that be detonation? i hear the term used liberally but dont really know what it is. I would think it would cause the mix not to burn at all and cause flooding. Thats just what my intuition tells me, but i could be way off.
Thanks guys (and girls maybe)Farls
Ive read and read... another fuel management question
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farlsmagee6
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DammitBobby
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Re: Ive read and read... another fuel management question (farlsmagee6)
Factory FPR regulates fuel pressure to 43 psi. When adding a FMU it adds fuel pressure on top of the 43 psi. so 8:1 FMU will add 8psi for every pound of boost. Provided you have a fuel pump that can handle the load.
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hannibal
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Re: Ive read and read... another fuel management question (farlsmagee6)
Yes FMU = RRFPR, and your description is correct. But the KA does not have a stock boost controller. I'm not sure how the stock FPR works, but it doesnt increase fuel pressure based on boost (because there is no boost on a stock KA...)farlsmagee6 wrote:I have been using the search button like nobody's business, trust me. I want to read everything i can before i jump into turboing my daily driver, but just for knowledge's sake...
to my understanding....An FMU is (to most) just another way to say RRFPR (rising rate fpr). A ratio of 8:1 or 10:1 would suggest that for each additional psi of boost, the fuel pressure is increased by 8 or 10 times as much. Is this correct? Does this also imply that since the stock FMU is set at 1:1 that the stock boost is always just 1psi? i know there is a stock boost controller ( i had to replace it recently- $$$ from the factory). does it just center the boost at 1psi or does it encounter increasing boost at minimal levels but so little that a 1:1 fmu is accurate enough to work.
Quote »Second, how much pressure can a stock fuel rail accept? i cant seem to find the answer to this one. And correct me if my logic is wrong because i am no mechanic... but with a turbo setup, making up to 7-8 psi, an FMU of 8:1 would (according to my math) make for 56-64 psi on the fuel side at maximum boost... correct? or is it not that simple. If that is spread out over four injectors, it should be around 14-16 psi per injector. Again.. is it not this simple? What that translates to in metric units (cc) i dont know. But from the talks of users of this setup, the stock injectors and the fuel rail can handle this with no problem. Im just wondering (just for the sake of wondering) how this matches up with the math of the issue.[/quote]An 8:1 FMU would ADD 56-64psi to the base fuel pressure at 7-8psi. Base pressure is 43.5psi (I think). So youre actually running over 100psi. No need to worry about the rail, it can handle it. The injectors (and fuel pump) may become a concern at that pressure. But lots of guys have run 8:1 (even 10:1) FMU's at 8psi and had no problems. Most guys say you need to be extra careful around 100psi, depending on the condition of your injectors and pump.
Quote »Lastly, Im a retard (no pun intended) when it comes to timing. Why is it necessary to adjust timing above the 8psi mark? could someone explain that... I would think it has to do with the backpressure created by the turbo that slows the cycle of the cylinder so much that firing a spark at normal timing would be too early and cause... would that be detonation? i hear the term used liberally but dont really know what it is. I would think it would cause the mix not to burn at all and cause flooding. Thats just what my intuition tells me, but i could be way off.
Thanks guys (and girls maybe)Farls[/quote]Timing is controlling when the spark fires (and therefore when the air/fuel mix begins to burn). I'm not completely sure of the physics involved in retarding timing, but the purpose is to prevent engine damage and detonation. Imagine if the mixture ignited at TDC. The piston would try to push the rod thru the crank. In a more powerful motor, its safer to ignite the mixture (fire the spark plug) later. IIRC, Retarding timing reduces power, but creates a safer situation for a turbo motor.
Okay, thanks for searching first: these are good questions and the kind we should have more of around here!
A RRFPR/FMU rated at 8:1 will raise the fuel pressure 8 psi for every 1 pound of boost. Likewise, a 1:1 model - like stock - will raise the fuel pressure 1 psi for every 1 pound of boost. This would mean, assuming you have a base fuel pressure of around 40 pounds, with the 8:1 at 5 psi you should be around 80psi of fuel pressure (40 + (8*5) ). The stock fuel pressure regulator does in fact add more fuel as you increase load (boost), just 1:1 is typically not enough.
I have never heard any problems of a fuel rail actually bursting from too much pressure. The stock lines are fairly solid and, assuming all your connections are fresh, should have NO problem with whatever pressure you throw at it with a FMU/RRFPR. It is a metal line, even rubber lines can easially handle well over a hundred psi (check the raiting on the hose). This shouldnt be an issue for you.
Timing is kind of a funky thing that not a lot of people understand properly. The reason timing ever changes in an engine is because you always want to have peak cyl pressures at the exact right time, right at or just after TDC (top dead center). What this means is you want the mixture (air/fuel) to be exploding with maximum force JUST as the piston is about to start heading downwards on the power stroke. This would be simple to do if the combustion rate was constant at all times while driving, but its not. Fuel/air mixtures at different temperatures, different ratios (rich or lean), different octanes, and different pressures take different amounts of time to burn completely. An intake charge of air and fuel compressed to 8 psi will ignite and combust MUCH faster than a similar charge at atmospheric pressure: the mixture is simply more reactive and "ready to explode." Because of this, you need to fire the spark LATER (retard) as the piston is coming around towards top dead center... because the mixture burns faster you have to ignite the spark as the piston is closer to top dead center, which hopefully results in peak cyl presures excactly at the right time. Figuring out exactly how much later you need to have the spark fire to achieve the best power is part of the skill involved with tuning, but for basic applications most people simply suggest a roundabout amount of degrees to retard per pound of boost (around .5 degrees).
If I explained all of this well enough to understand, it should also be clear why ignition must be advanced (spark fired prior to TDC) when RPMs increase. Because your (non boosted) air intake mixture at a given temperature will take a fairly static amount of time to combust, as RPMs increase and the piston starts moving faster and faster, you need to start igniting the fuel EARLIER so as to get full combustion by the time the piston is at top dead center. Think of throwing a ball in front of a moving car. The faster the car is moving, the earlier you are going to have to throw the ball out in order to have the car hit it, right? Same idea here: you want to time when to start igniting the fuel, so that by the time the flame has spread and the explosion has the most power, the pistion is right at the top and ready to be pushed down by it. Again with the car/bar analogy... if you throw the ball harder/faster, you actually are going to have to throw the ball later as the car is closer to you, in order to time the ball + car hitting at the exact right time. Same deal with boosted applications and more volitile mixtures... The explosion happens faster so it has to be begun (ignited) later in order to achieve that perfect meeting point at TDC (or just after actually).
Detonation is when timing (for one of many reasons) is NOT correct. Imagine firing the spark too early, as the pistion is still making its way upwards towards top dead center. The force of the explosion of air/fuel is actually pressing downward on the pistion as it normally would, except the pistion is still trying to come upwards in its cycle. This results in a battle of pressures, and puts a lot of stress on the engine (specifically the rings on the piston)... The explosion certanly wouldnt be enough to reverse the direction of the piston, but the piston will suffer a LOT of damage from the mis-timed explosion. This is why knock is so bad in boosted applications. It takes mere SECONDS of serious knock to destroy ring lands, pistons, rods, everything. At 7000 RPM the piston is in its compression stroke (coming up towards TDC and compressing the intake charge) 29 times per second. On high boost applications like in race cars, you dont even hear detonation before the engine is completely destroyed. The timing goes out and thats it, boom.
This is why people put so much effort into making sure the timing is right even in lower boost applications. Also higher octane gas helps (the higher the octane, the SLOWER the mixture will burn, allowing timing to be advanced a little - or in our case - retarded less), as well as alchy which does much the same thing.
Okay okay, I'm done typing now. Hopefully all this helps you. If you are confused about anything please feel free to ask. I or someone else around here will be happy to help. Again thanks for taking the time to search, and THANK YOU for being one of the few who is actually trying to wrap your head around the concepts before you go shopping for parts. Keep up the good work and good luck!
A RRFPR/FMU rated at 8:1 will raise the fuel pressure 8 psi for every 1 pound of boost. Likewise, a 1:1 model - like stock - will raise the fuel pressure 1 psi for every 1 pound of boost. This would mean, assuming you have a base fuel pressure of around 40 pounds, with the 8:1 at 5 psi you should be around 80psi of fuel pressure (40 + (8*5) ). The stock fuel pressure regulator does in fact add more fuel as you increase load (boost), just 1:1 is typically not enough.
I have never heard any problems of a fuel rail actually bursting from too much pressure. The stock lines are fairly solid and, assuming all your connections are fresh, should have NO problem with whatever pressure you throw at it with a FMU/RRFPR. It is a metal line, even rubber lines can easially handle well over a hundred psi (check the raiting on the hose). This shouldnt be an issue for you.
Timing is kind of a funky thing that not a lot of people understand properly. The reason timing ever changes in an engine is because you always want to have peak cyl pressures at the exact right time, right at or just after TDC (top dead center). What this means is you want the mixture (air/fuel) to be exploding with maximum force JUST as the piston is about to start heading downwards on the power stroke. This would be simple to do if the combustion rate was constant at all times while driving, but its not. Fuel/air mixtures at different temperatures, different ratios (rich or lean), different octanes, and different pressures take different amounts of time to burn completely. An intake charge of air and fuel compressed to 8 psi will ignite and combust MUCH faster than a similar charge at atmospheric pressure: the mixture is simply more reactive and "ready to explode." Because of this, you need to fire the spark LATER (retard) as the piston is coming around towards top dead center... because the mixture burns faster you have to ignite the spark as the piston is closer to top dead center, which hopefully results in peak cyl presures excactly at the right time. Figuring out exactly how much later you need to have the spark fire to achieve the best power is part of the skill involved with tuning, but for basic applications most people simply suggest a roundabout amount of degrees to retard per pound of boost (around .5 degrees).
If I explained all of this well enough to understand, it should also be clear why ignition must be advanced (spark fired prior to TDC) when RPMs increase. Because your (non boosted) air intake mixture at a given temperature will take a fairly static amount of time to combust, as RPMs increase and the piston starts moving faster and faster, you need to start igniting the fuel EARLIER so as to get full combustion by the time the piston is at top dead center. Think of throwing a ball in front of a moving car. The faster the car is moving, the earlier you are going to have to throw the ball out in order to have the car hit it, right? Same idea here: you want to time when to start igniting the fuel, so that by the time the flame has spread and the explosion has the most power, the pistion is right at the top and ready to be pushed down by it. Again with the car/bar analogy... if you throw the ball harder/faster, you actually are going to have to throw the ball later as the car is closer to you, in order to time the ball + car hitting at the exact right time. Same deal with boosted applications and more volitile mixtures... The explosion happens faster so it has to be begun (ignited) later in order to achieve that perfect meeting point at TDC (or just after actually).
Detonation is when timing (for one of many reasons) is NOT correct. Imagine firing the spark too early, as the pistion is still making its way upwards towards top dead center. The force of the explosion of air/fuel is actually pressing downward on the pistion as it normally would, except the pistion is still trying to come upwards in its cycle. This results in a battle of pressures, and puts a lot of stress on the engine (specifically the rings on the piston)... The explosion certanly wouldnt be enough to reverse the direction of the piston, but the piston will suffer a LOT of damage from the mis-timed explosion. This is why knock is so bad in boosted applications. It takes mere SECONDS of serious knock to destroy ring lands, pistons, rods, everything. At 7000 RPM the piston is in its compression stroke (coming up towards TDC and compressing the intake charge) 29 times per second. On high boost applications like in race cars, you dont even hear detonation before the engine is completely destroyed. The timing goes out and thats it, boom.
This is why people put so much effort into making sure the timing is right even in lower boost applications. Also higher octane gas helps (the higher the octane, the SLOWER the mixture will burn, allowing timing to be advanced a little - or in our case - retarded less), as well as alchy which does much the same thing.
Okay okay, I'm done typing now. Hopefully all this helps you. If you are confused about anything please feel free to ask. I or someone else around here will be happy to help. Again thanks for taking the time to search, and THANK YOU for being one of the few who is actually trying to wrap your head around the concepts before you go shopping for parts. Keep up the good work and good luck!
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farlsmagee6
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Re: (fiznat)
EXCELLENT POST! about halfway through i was already nodding my head in approval. it makes much more sense now as far as timing is concerned. Im assuming its better to retard the timing a little TOO much than not enough or not at all instead of having the bang coming whil the piston is still in the squish stroke (suck, squish, bang, blow is the way i always refered to them)- lots of contradicting force! so yeah.. that makes much more sense.
also- great post on the fuel pressure.. now the whole 100psi threshhold makes sense also. Just for the knowledge of it though, i just assume this 100psi would be distributed evenly over the four injectors. with about 40 psi stock from the stock fmu, adding 8 pounds of boost on an 8:1 downstream fmu would add around 64 psi equals a little more than 100 psi. does this mean each injector is handling a total of 25 psi? can anyone translate the math into metric units? or viceversa- 270cc stock injectors = ??? lbs per injector . Id just like to know at what capacity that would run stock injectors (ie 85% 95% 120%, obviously anything above 90% to me is gonna be getting into the risky area)- because as i say, lots of guys do it and do it safely, but I feel better when i know just exactly WHAT im doing to my car and HOW im doing it.
A WHAT IF...If i were trying to reduce the used capacity on the stock injectors, I could hypothetically run a lower ration FMU, say 7:1 to get it under 100psi or within a running capacity I'm comfortable with for the stock injectors. But how is this going to affect Air/Fuel ratio? I know it will lean it out, but how lean is too lean? This is another area Im a little shady on. At a certain point i would think too little fuel would create a situation where there is little or no combustion in the cylinder- is this another form of knock? What are good air/fuel ratios (i know ive read this before, but by now ive forgotten as ive been researching over the last two months)
thanksfarley
also- great post on the fuel pressure.. now the whole 100psi threshhold makes sense also. Just for the knowledge of it though, i just assume this 100psi would be distributed evenly over the four injectors. with about 40 psi stock from the stock fmu, adding 8 pounds of boost on an 8:1 downstream fmu would add around 64 psi equals a little more than 100 psi. does this mean each injector is handling a total of 25 psi? can anyone translate the math into metric units? or viceversa- 270cc stock injectors = ??? lbs per injector . Id just like to know at what capacity that would run stock injectors (ie 85% 95% 120%, obviously anything above 90% to me is gonna be getting into the risky area)- because as i say, lots of guys do it and do it safely, but I feel better when i know just exactly WHAT im doing to my car and HOW im doing it.
A WHAT IF...If i were trying to reduce the used capacity on the stock injectors, I could hypothetically run a lower ration FMU, say 7:1 to get it under 100psi or within a running capacity I'm comfortable with for the stock injectors. But how is this going to affect Air/Fuel ratio? I know it will lean it out, but how lean is too lean? This is another area Im a little shady on. At a certain point i would think too little fuel would create a situation where there is little or no combustion in the cylinder- is this another form of knock? What are good air/fuel ratios (i know ive read this before, but by now ive forgotten as ive been researching over the last two months)
thanksfarley
Re: (farlsmagee6)
From a pure physics standpoint, all the injectors (and everything else in the system upstream of the FPR) sees the same pressure. Obviously there are inconsistencies, but they will all see close to the full 100psi.
Overall amount fuel being sprayed is a function of flow rate, injector pulsewidth and pressure differential between the fuel rail and the manifold.
As boost goes up, your IPW will go up slightly based on the increased airflow through the MAF, and your Fuel Pressure will go up due to the FPR. So your overall amount of fuel getting dumped in goes up. If you want to reduce your fuel pressure, you need another way to fake out the extra fuel, IE, higher flow injectors or a longer IPW. Altering either of the above will require tuning the ECU.
Another way to do it is an extra injector type setup as an auxiliary fuel supply, like what is found on some wet shot NOS systems. This gets you into a wet manifold setup and is pretty undesirable though when you consider the cost compared to a tunable ECU.
Overall amount fuel being sprayed is a function of flow rate, injector pulsewidth and pressure differential between the fuel rail and the manifold.
As boost goes up, your IPW will go up slightly based on the increased airflow through the MAF, and your Fuel Pressure will go up due to the FPR. So your overall amount of fuel getting dumped in goes up. If you want to reduce your fuel pressure, you need another way to fake out the extra fuel, IE, higher flow injectors or a longer IPW. Altering either of the above will require tuning the ECU.
Another way to do it is an extra injector type setup as an auxiliary fuel supply, like what is found on some wet shot NOS systems. This gets you into a wet manifold setup and is pretty undesirable though when you consider the cost compared to a tunable ECU.
Thanks man
Okay, injector duty cycle is not a function of fuel pressure, but rather pulsewidth. Pulsewidth describes how long the injector is "open" (how long it is spraying fuel, measured in mS - milliseconds). As RPMs increase in any motor, the amount of time the injector has to spray fuel also decreases. Smaller injectors (like stock) have pintle openings that are simply not big enough to get the required amount of fuel sprayed in the small window the injector has during the intake stroke. Increasing the fuel pressure actually increases how much the injector can spray. Imagine holding your thumb over a garden hose, with the water turned on to a low pressure. Remove your thumb quickly and only a little bit of water will come out. Now increase the pressure in the hose and quickly remove your thumb again: much more water will spray out. Same thing here. Increased fuel pressure is a quick fix to compensate for injectors that are too small.
You also seem to be confusing fuel pressure and injector size. You dont divide the pressure in the rail by the number of injectors, each injector will see just about the full pressure in the rail: it is not distribuited evenly like you said. Even still, when you are looking at injector size, like 270cc, that is not a measurement of how much pressure the injector takes, rather it describes how much fuel the injector can spray: 270 cc of fuel per minute. You may have noted that injectors are also rated in pounds. It is roughly a factor of 10: a 550 cc injector is roughly the same as a 50# (fifty pound) one. Either way, these numbers refer to maximum fuel output, not maximum fuel pressure input.
There is not another kind of detonation. You need more fuel in order to match the added air you pushed in with the turbo: the ratios must remain the same ("stoich" in order to get an efficient combustion). Stoich for a normal (non boosted) car is around 14 parts air to 1 part fuel (14:1). Boosted cars run slightly richer around 12:1 or so. The reason for the extra fuel is for cooling purposes. Running a 14:1 AFR in a boosted car would be considered "lean," but technically it is not: stoich means by definetion that each part of fuel in the mixture has enough oxygen to compltely combust. Running at stoich means that you are burning all of your fuel efficiently. The extra fuel added in boosted applications is not burnt at all. This extra fuel is used to help cool things down in the cyl. Things get extremely hot inside the combustion chamber, and with each degree of temperature the chances of detonation go up. Remember that the intake charge is extremely volitile, and it becomes even more so as it is compressed by the piston and heated up even more. When things get this hot, the fuel mixture can actually combust without any spark at all. This as you can probably imagine is very bad: as you need to have full control of exactly when combustion begins. Heat is your enemy, and the extra fuel is used to help combat it by cooling things down below a threshold in the combustion chamber.
Hope this makes sense...
EDIT: yeah, foley did a good job describing it as well. When he says "IPW" he means "injector pulsewidth"
Okay, injector duty cycle is not a function of fuel pressure, but rather pulsewidth. Pulsewidth describes how long the injector is "open" (how long it is spraying fuel, measured in mS - milliseconds). As RPMs increase in any motor, the amount of time the injector has to spray fuel also decreases. Smaller injectors (like stock) have pintle openings that are simply not big enough to get the required amount of fuel sprayed in the small window the injector has during the intake stroke. Increasing the fuel pressure actually increases how much the injector can spray. Imagine holding your thumb over a garden hose, with the water turned on to a low pressure. Remove your thumb quickly and only a little bit of water will come out. Now increase the pressure in the hose and quickly remove your thumb again: much more water will spray out. Same thing here. Increased fuel pressure is a quick fix to compensate for injectors that are too small.
You also seem to be confusing fuel pressure and injector size. You dont divide the pressure in the rail by the number of injectors, each injector will see just about the full pressure in the rail: it is not distribuited evenly like you said. Even still, when you are looking at injector size, like 270cc, that is not a measurement of how much pressure the injector takes, rather it describes how much fuel the injector can spray: 270 cc of fuel per minute. You may have noted that injectors are also rated in pounds. It is roughly a factor of 10: a 550 cc injector is roughly the same as a 50# (fifty pound) one. Either way, these numbers refer to maximum fuel output, not maximum fuel pressure input.
There is not another kind of detonation. You need more fuel in order to match the added air you pushed in with the turbo: the ratios must remain the same ("stoich" in order to get an efficient combustion). Stoich for a normal (non boosted) car is around 14 parts air to 1 part fuel (14:1). Boosted cars run slightly richer around 12:1 or so. The reason for the extra fuel is for cooling purposes. Running a 14:1 AFR in a boosted car would be considered "lean," but technically it is not: stoich means by definetion that each part of fuel in the mixture has enough oxygen to compltely combust. Running at stoich means that you are burning all of your fuel efficiently. The extra fuel added in boosted applications is not burnt at all. This extra fuel is used to help cool things down in the cyl. Things get extremely hot inside the combustion chamber, and with each degree of temperature the chances of detonation go up. Remember that the intake charge is extremely volitile, and it becomes even more so as it is compressed by the piston and heated up even more. When things get this hot, the fuel mixture can actually combust without any spark at all. This as you can probably imagine is very bad: as you need to have full control of exactly when combustion begins. Heat is your enemy, and the extra fuel is used to help combat it by cooling things down below a threshold in the combustion chamber.
Hope this makes sense...
EDIT: yeah, foley did a good job describing it as well. When he says "IPW" he means "injector pulsewidth"
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farlsmagee6
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Re: (fiznat)
aha! the lightbulb turns on. now i realize how i was muddling up the two measurements and the whole fuel pressure thing- Im an accountant so i like to figure out exactly where all the numbers are coming from... i wish i was a better mathemetician so i could figure out what the final afr would be, but i guess the best way to figure it is just to hook up the wideband and gauge it.
I want to eventually get into tuning and everything else, so i figured this would be a good starting place. next is learning how to actually do the tuning with and s-afc or e-manage. After i actually get this first setup installed and working and UNDERSTOOD, then Ill bump up one step with injectors, tuning, and added boost. Thanks for the info guys
I want to eventually get into tuning and everything else, so i figured this would be a good starting place. next is learning how to actually do the tuning with and s-afc or e-manage. After i actually get this first setup installed and working and UNDERSTOOD, then Ill bump up one step with injectors, tuning, and added boost. Thanks for the info guys
Detonation is unwanted, uncontrolled/erratic combustion at the same time or after the spark event occurs. It can happen because of incorrect timing, too low of octane fuel, too much boost, etc. (I have a really cool picture of detonation taken from inside the cylinder while it occurs in a book i have, i wish i could show it)
Dont forget about pre-ignition too.Pre-ignition is when unwanted combustion happens before the spark event. It usually happens from a hot spot on the piston or in the combustion chamber.
stoich is 14.7:1 btw
pretty good explanation. I like the car/ball analogy
Dont forget about pre-ignition too.Pre-ignition is when unwanted combustion happens before the spark event. It usually happens from a hot spot on the piston or in the combustion chamber.
stoich is 14.7:1 btw
pretty good explanation. I like the car/ball analogy
Re: Ive read and read... another fuel management question (farlsmagee6)
Excellent impromptu write-up. *applause*
...and in the spirit of newbie questions:
What is this wideband o2 sensor i keep reading about?
I've tried searching, but only find vague references to it. Any help is appreciated, and if this deserves a new topic just say so and I will copy and paste this out of here.
...and in the spirit of newbie questions:
What is this wideband o2 sensor i keep reading about?
I've tried searching, but only find vague references to it. Any help is appreciated, and if this deserves a new topic just say so and I will copy and paste this out of here.