Target A/F when Tuning Forced Induction?
10-27-2007, 07:34 AM
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Originally Posted by athenG
Great Post!!! I'm not sure about the timing part, it is really hard to tell if advancing the timing really did add some power to a point without putting it in a dyno. fixing the fuel curve on the street is great but I feel that the timing part should be done on a dyno since there is no point of adding timing if it actually not giving more power anymore. JMHO.
10-27-2007, 06:45 PM
#23
Thanks guys. My comments on the timing comes from experience and what theory dictates. As you increase timing, you end up producing more pressure in the chamber which ends up producing more kinetic energy in the most favorable point in the combustion cycle. From experience, I always found pump gas to be the limiting factor which determines how far you can push it before you start seeing detonation. Granted, real life doesn't always follow the theory exactly but I've found that with the octane levels that we get at our gas stations, it's hard to push the engines to max best timing before you see knock. I hear guys complaining about Cali 91oct **** all the time 
In case of 93, with FI, it's much better but you'll still be hard pressed to reach MBT or exceed it. Having alcohol in your mix helps a lot because it has lots of detonation suppression properties so you can go further. If you're tuning for race gas, then yes, dyno is key to tell you when you've reached point where adding more timing can actually hurt you. It's also important to keep in mind that dynos are not perfect. They measure power delivery within some margin of error so whatever that error range is, you can fluctuate within it and still technically make the same power or more. Just something to keep in mind.
To the OP, keep us apprised of how your tuning goes.
And lastly, GO SOX!!!! They're up 6-0 right now. This is the year, baby!!!!
In case of 93, with FI, it's much better but you'll still be hard pressed to reach MBT or exceed it. Having alcohol in your mix helps a lot because it has lots of detonation suppression properties so you can go further. If you're tuning for race gas, then yes, dyno is key to tell you when you've reached point where adding more timing can actually hurt you. It's also important to keep in mind that dynos are not perfect. They measure power delivery within some margin of error so whatever that error range is, you can fluctuate within it and still technically make the same power or more. Just something to keep in mind.To the OP, keep us apprised of how your tuning goes.
And lastly, GO SOX!!!! They're up 6-0 right now. This is the year, baby!!!!
10-27-2007, 07:27 PM
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Originally Posted by Ziggyrama
And lastly, GO SOX!!!! They're up 6-0 right now. This is the year, baby!!!
No this will be the second year thanks to F'ing M. Rivera for blowing all those save. I still can't forget how the Yanks loose a 3-0 lead.
Any ways great to have another person who can contribute to the site.
10-27-2007, 11:34 PM
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Originally Posted by MRC Motorsports
11.8 is the leanest we go on the VQ motors on 93 octane. The car pings in N/A form at 12.5 AF..
I wonder how much power us HR guys are losing with i/test pipes/exhaust due to running lean (14-16:1) a/f down low and in the mid range
10-28-2007, 10:39 AM
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Originally Posted by VitViper
O rly?
I wonder how much power us HR guys are losing with i/test pipes/exhaust due to running lean (14-16:1) a/f down low and in the mid range
I wonder how much power us HR guys are losing with i/test pipes/exhaust due to running lean (14-16:1) a/f down low and in the mid range
10-28-2007, 12:33 PM
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Originally Posted by MRC Motorsports
Well down low its not that important until you hit peak TQ areas on the graph. We generally run 13.5-12.5 on a nice smooth A/F graph. if your running 14-16 your either not under load/WOT or something is wrong with your set up.
I'm just curious... cause putting my stock intakes back on the car runs noticeably stronger in the low end and mid range. And the whole powerband is just smoother.
11-01-2007, 01:21 AM
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Originally Posted by athenG
/\ If you target your A/F around 12's then you don't know enough how weak the VQ engine. The first few years VQ has been blowing left and right and that is why most VQ tuner on this site will not run 12's A/F even on 7psi. You are comparing an Iron Block engine that is build to handle boost so your margin is bigger in term of tuning.
If that's what you thought, YIKES! Go back and read my post again .The difference isn't really in the block construction in this case but the static compression ratio and (i'm guessing here) overall design of the motor.). FI motors have different reqirements when it comes to piston design, quench area, and combustion chamber shape. Although I do want to point out that I said within one point of 12.5. 11.5 is one point away and so is 13.5. 13.5 is pretty lean, but it can work for lower powered N/A setups. 11.5 a good starting place for the lower boost pump gas high static CR setups. Higher boost (more load) and need to go richer. You also though balance timing with how much fuel you use.
Application Note: You CAN be too Rich
By Klaus Allmendinger, VP of Engineering, Innovate Motorsports
Many people with turbochargers believe that they need to run at very rich mixtures. The theory is that the excess fuel cools the intake charge and therefore reduces the probability of knock. It does work in reducing knock, but not because of charge cooling. The following little article shows why.
First let’s look at the science. Specific heat is the amount of energy required to raise 1 kg of material by one degree K (Kelvin, same as Celsius but with 0 point at absolute zero). Different materials have different specific heats. The energy is measured in kJ or kilojoules:
Air ~ 1 kJ/( kg * deg K)
Gasoline 2.02 kJ/( kg * deg K)
Water 4.18 kJ/( kg * deg K)
Ethanol 2.43 kJ/( kg * deg K)
Methanol 2.51 kJ/( kg * deg K)
Fuel and other liquids also have what's called latent heat. This is the heat energy required to vaporize 1 kg of the liquid. The fuel in an internal combustion engine has to be vaporized and mixed thoroughly with the incoming air to produce power. Liquid gasoline does not burn. The energy to vaporize the fuel comes partially from the incoming air, cooling it. The latent heat energy required is actually much larger than the specific heat. That the energy comes from the incoming air can be easily seen on older carbureted cars, where frost can actually form on the intake manifold from the cooling of the charge.
The latent heat values of different liquids are shown here:
Gasoline 350 kJ/kg
Water 2256 kJ/kg
Ethanol 904 kJ/kg
Methanol 1109 kJ/kg
Most engines produce maximum power (with optimized ignition timing) at an air-fuel-ratio between 12 and 13. Let's assume the optimum is in the middle at 12.5. This means that for every kg of air, 0.08 kg of fuel is mixed in and vaporized. The vaporization of the fuel extracts 28 kJ of energy from the air charge. If the mixture has an air-fuel-ratio of 11 instead, the vaporization extracts 31.8 kJ instead. A difference of 3.8 kJ. Because air has a specific heat of about 1 kJ/kg*deg K, the air charge is only 3.8 C (or K) degrees cooler for the rich mixture compared to the optimum power mixture. This small difference has very little effect on knock or power output.
If instead of the richer mixture about 10% (by mass) of water would be injected in the intake charge (0.008 kg Water/kg air), the high latent heat of the water would cool the charge by 18 degrees, about 4 times the cooling effect of the richer mixture. The added fuel for the rich mixture can't burn because there is just not enough oxygen available. So it does not matter if fuel or water is added.
So where does the knock suppression of richer mixtures come from?
If the mixture gets ignited by the spark, a flame front spreads out from the spark plug. This burning mixture increases the pressure and temperature in the cylinder. At some time in the process the pressures and temperatures peak. The speed of the flame front is dependent on mixture density and AFR. A richer or leaner AFR than about 12-13 AFR burns slower. A denser mixture burns faster.
So with a turbo under boost the mixture density raises and results in a faster burning mixture. The closer the peak pressure is to TDC, the higher that peak pressure is, resulting in a high knock probability. Also there is less leverage on the crankshaft for the pressure to produce torque, and, therefore, less power.
Richening up the mixture results in a slower burn, moving the pressure peak later where there is more leverage, hence more torque. Also the pressure peak is lower at a later crank angle and the knock probability is reduced. The same effect can be achieved with an optimum power mixture and more ignition retard.
Optimum mix with “later” ignition can produce more power because more energy is released from the combustion of gasoline. Here’s why: When hydrocarbons like gasoline combust, the burn process actually happens in multiple stages. First the gasoline molecules are broken up into hydrogen and carbon. The hydrogen combines with oxygen from the air to form H2O (water) and the carbon molecules form CO. This process happens very fast at the front edge of the flame front. The second stage converts CO to CO2. This process is relatively slow and requires water molecules (from the first stage) for completion. If there is no more oxygen available (most of it consumed in the first stage), the second stage can't happen. But about 2/3 of the energy released from the burning of the carbon is released in the second stage. Therefore a richer mixture releases less energy, lowering peak pressures and temperatures, and produces less power. A secondary side effect is of course also a lowering of knock probability. It's like closing the throttle a little. A typical engine does not knock when running on part throttle because less energy and therefore lower pressures and temperatures are in the cylinder.
This is why running overly-rich mixtures can not only increase fuel consumption, but also cost power.
Until next time... Keep On Tuning!
-Innovate Motorsports
By Klaus Allmendinger, VP of Engineering, Innovate Motorsports
Many people with turbochargers believe that they need to run at very rich mixtures. The theory is that the excess fuel cools the intake charge and therefore reduces the probability of knock. It does work in reducing knock, but not because of charge cooling. The following little article shows why.
First let’s look at the science. Specific heat is the amount of energy required to raise 1 kg of material by one degree K (Kelvin, same as Celsius but with 0 point at absolute zero). Different materials have different specific heats. The energy is measured in kJ or kilojoules:
Air ~ 1 kJ/( kg * deg K)
Gasoline 2.02 kJ/( kg * deg K)
Water 4.18 kJ/( kg * deg K)
Ethanol 2.43 kJ/( kg * deg K)
Methanol 2.51 kJ/( kg * deg K)
Fuel and other liquids also have what's called latent heat. This is the heat energy required to vaporize 1 kg of the liquid. The fuel in an internal combustion engine has to be vaporized and mixed thoroughly with the incoming air to produce power. Liquid gasoline does not burn. The energy to vaporize the fuel comes partially from the incoming air, cooling it. The latent heat energy required is actually much larger than the specific heat. That the energy comes from the incoming air can be easily seen on older carbureted cars, where frost can actually form on the intake manifold from the cooling of the charge.
The latent heat values of different liquids are shown here:
Gasoline 350 kJ/kg
Water 2256 kJ/kg
Ethanol 904 kJ/kg
Methanol 1109 kJ/kg
Most engines produce maximum power (with optimized ignition timing) at an air-fuel-ratio between 12 and 13. Let's assume the optimum is in the middle at 12.5. This means that for every kg of air, 0.08 kg of fuel is mixed in and vaporized. The vaporization of the fuel extracts 28 kJ of energy from the air charge. If the mixture has an air-fuel-ratio of 11 instead, the vaporization extracts 31.8 kJ instead. A difference of 3.8 kJ. Because air has a specific heat of about 1 kJ/kg*deg K, the air charge is only 3.8 C (or K) degrees cooler for the rich mixture compared to the optimum power mixture. This small difference has very little effect on knock or power output.
If instead of the richer mixture about 10% (by mass) of water would be injected in the intake charge (0.008 kg Water/kg air), the high latent heat of the water would cool the charge by 18 degrees, about 4 times the cooling effect of the richer mixture. The added fuel for the rich mixture can't burn because there is just not enough oxygen available. So it does not matter if fuel or water is added.
So where does the knock suppression of richer mixtures come from?
If the mixture gets ignited by the spark, a flame front spreads out from the spark plug. This burning mixture increases the pressure and temperature in the cylinder. At some time in the process the pressures and temperatures peak. The speed of the flame front is dependent on mixture density and AFR. A richer or leaner AFR than about 12-13 AFR burns slower. A denser mixture burns faster.
So with a turbo under boost the mixture density raises and results in a faster burning mixture. The closer the peak pressure is to TDC, the higher that peak pressure is, resulting in a high knock probability. Also there is less leverage on the crankshaft for the pressure to produce torque, and, therefore, less power.
Richening up the mixture results in a slower burn, moving the pressure peak later where there is more leverage, hence more torque. Also the pressure peak is lower at a later crank angle and the knock probability is reduced. The same effect can be achieved with an optimum power mixture and more ignition retard.
Optimum mix with “later” ignition can produce more power because more energy is released from the combustion of gasoline. Here’s why: When hydrocarbons like gasoline combust, the burn process actually happens in multiple stages. First the gasoline molecules are broken up into hydrogen and carbon. The hydrogen combines with oxygen from the air to form H2O (water) and the carbon molecules form CO. This process happens very fast at the front edge of the flame front. The second stage converts CO to CO2. This process is relatively slow and requires water molecules (from the first stage) for completion. If there is no more oxygen available (most of it consumed in the first stage), the second stage can't happen. But about 2/3 of the energy released from the burning of the carbon is released in the second stage. Therefore a richer mixture releases less energy, lowering peak pressures and temperatures, and produces less power. A secondary side effect is of course also a lowering of knock probability. It's like closing the throttle a little. A typical engine does not knock when running on part throttle because less energy and therefore lower pressures and temperatures are in the cylinder.
This is why running overly-rich mixtures can not only increase fuel consumption, but also cost power.
Until next time... Keep On Tuning!
-Innovate Motorsports
Last edited by SamuraiSam; 11-01-2007 at 01:50 AM.
11-01-2007, 01:33 AM
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Ziggyrama, I find it interesting that you're in the "advance timing until it knocks" camp. What kind of equipment do you use to monitor detonation? Absolutely on a well-designed higher compression engines trying to run any reasonable amount of boost, the fuel will be THE limitation (as opposed to an engine being knock limited)
When you can't tune to MBT like on the VQ with pump gas I've been instructed to watch the tractive effort/instantaneous torque output per load site and look at the 'gain' as timing is added. If you were to plot out the torque gain per degree of timing you generally see a 'bell curve' effect - as you get closer to the detonation threshold at any one load site, the TE gain becomes incrementally smaller per degree of timing added. Just by paying attention to this curve you should be able to arrive at powerful yet safe values while avoiding the deliberate knocking method. I'm not saying you're never going to knock during the tuning session, but it should be possible to keep from knocking while under full boost with the 'plateau' method.
You sound like you have quite a bit more experience than I do, which I'm not going to attempt to argue with, but the method that I outlined above does seem like a safer one. Maybe it doesn't work in the real world on a VQ for some reason that I don't know about.
BTW - I think you meant to say that you'd find the engine more prone to knocking [due to overly advanced ignition] near the VE peak / torque peak.
Agreed 100% about not trying to build a timing map on the street. It's absolutely a great idea, after dyno tuning, to do street tuning as that's the condition the car will be driving in- and pull timing if needed. Usually though any additional knocking on the street that didn't exist on the dyno is going to be due to a heat soak issue instead of too much timing, so you might want to then bump up your target AFR at that load row and add a bit more fuel for thermal management sake. My guess method would be that if you are hitting a max of 250 kpa and you would be seeing knock due to heat issues on the street at 200kpa (you can check the air intake temp sensor datalog to verify) to bump up each row starting with the problem row another .2 or .3 AFR and see where that goes.
I'm not trying to start any arguments or flat-out disagree with the professionals posting in this thread, but just sharing what I have learned from formal training as well as conversations with a few of some of the most experienced tuners in the country.
When you can't tune to MBT like on the VQ with pump gas I've been instructed to watch the tractive effort/instantaneous torque output per load site and look at the 'gain' as timing is added. If you were to plot out the torque gain per degree of timing you generally see a 'bell curve' effect - as you get closer to the detonation threshold at any one load site, the TE gain becomes incrementally smaller per degree of timing added. Just by paying attention to this curve you should be able to arrive at powerful yet safe values while avoiding the deliberate knocking method. I'm not saying you're never going to knock during the tuning session, but it should be possible to keep from knocking while under full boost with the 'plateau' method.
You sound like you have quite a bit more experience than I do, which I'm not going to attempt to argue with, but the method that I outlined above does seem like a safer one. Maybe it doesn't work in the real world on a VQ for some reason that I don't know about.
BTW - I think you meant to say that you'd find the engine more prone to knocking [due to overly advanced ignition] near the VE peak / torque peak.
Agreed 100% about not trying to build a timing map on the street. It's absolutely a great idea, after dyno tuning, to do street tuning as that's the condition the car will be driving in- and pull timing if needed. Usually though any additional knocking on the street that didn't exist on the dyno is going to be due to a heat soak issue instead of too much timing, so you might want to then bump up your target AFR at that load row and add a bit more fuel for thermal management sake. My guess method would be that if you are hitting a max of 250 kpa and you would be seeing knock due to heat issues on the street at 200kpa (you can check the air intake temp sensor datalog to verify) to bump up each row starting with the problem row another .2 or .3 AFR and see where that goes.
I'm not trying to start any arguments or flat-out disagree with the professionals posting in this thread, but just sharing what I have learned from formal training as well as conversations with a few of some of the most experienced tuners in the country.
Last edited by SamuraiSam; 11-01-2007 at 01:48 AM.
11-01-2007, 01:45 AM
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Originally Posted by VitViper
I'm just curious... cause putting my stock intakes back on the car runs noticeably stronger in the low end and mid range. And the whole powerband is just smoother.
11-01-2007, 06:38 AM
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Originally Posted by SamuraiSam
11.8 is conservative. Most low boost pump gas setups are good within 1 point of 12.5:1. Base maps as a rule are too rich and do not have enough timing so I wouldn't worry that you are leaner then the base map.
I'm disputing that 11.8 is not conservative on VQ. You are giving an advice on a VQ motor right? Well I'm just stating that no VQ Tuner will run their A/F this high especially on peak TQ and pump gas. If this is conservative then why do I see many Subaru and Mitsu performance cars which run as rich as 10 to 1 stock on the dyno? and even Most RB Motors running as little as 9 psi will be in the high tens factory? That I think is conservative and OEM tend to do that just for added safety.
I'm no expert here but I'm just stating what are the consensus here. This is also the reason why people should go to a tuner that has experience on their car.
Last edited by athenG; 11-01-2007 at 06:40 AM.
11-01-2007, 06:45 AM
#32
Samurai, in response to your post, don't worry I don't take offense to you questioning my statements. I'm glad people are thinking with their own heads and not just assuming everything others post is right. Glad you're doing that. Generally, there are various schools of thought when it comes to tuning and different people try to get to the same point in different ways. Are some ways better than others? Probably.
Anyways, I don't think I follow this:
^^^ Knock, aka detonation, is a result of uncontrolled burn during combustion cycle. The temps and pressures in the cylinder end up igniting the mixture at another point other than the source of the spark which creates a secondary flame front. This creates abnormal pressures and temp fluctuations which can have damaging effects. Once the flame fronts collide, the piston can actually rattle and if it's severe enough, it will be audible which we all know as that 'marbles in a tin can' sound or pinging. If you can hear it with your ear without det-cans, it's serious. Mild detonation cannot be heard without an instrument so tuning with a knock detection device is key. From your statement, sounds like you suggested that the engine can be knock limited which I don;t understand. I don't know what that means. As I see it, detonation is combination of various conditions imposing their will on the fuel so the limit is always tied to the properties of fuel. Perhaps you can clarify.
^^^ I like that approach. It's scientific and organized. How long does it take you to go through a map and get the timing advance curves like this? Generally, timing maps are 3D maps, functions of load and RPM. I am curious to hear how you can cover most cells in your map like this, with respect to RPM. You will want to cover most cells in your map to make sure you don't have trouble spots however, from experience, you can make a very good guess based on some initial points on the map that you dialed in, how the timing curve should look like and then interpolate the other cells to fill the numbers. Build a smooth curve and then test it to make sure it works. Record where you think you have trouble spots and correct them. Basically, nature like smoothness. Your timing profile should not jump up and down as you climb through the RPMs and loads. If it does, you'll end up with lumpy power delivery with some power flat spots that will feel 'weird'.
The assumption is that you have a good idea where you should be roughly. If you advance a couple degrees too far and you start seeing knock, pull it back. The knock you experienced at the threshold is mild and will not cause damage to the engine. Inducing some knock during tuning is unavoidable, and I think we agree there. Even stock cars that have dynamic timing advance do it to some degree and they're set up that way from factory. The key is to not be a bone head and continue to advance when the engine is telling you to lay off. That's just (un)common sense.
I've used det-cans in the past for knock detection. I also used stock knock sensor coupled with knock correction feedback in the ECU (not Nissan ECU) to see when the ECU thinks it is knocking which it was actually amazingly good at. There are some limitation to what the ECU can detect as far as knock though. Believe it or not, your ears are the most sophisticated listening device you can get so use them with an amplification device and you can't go wrong. More than you ever wanted to know about knock and how to measure it (awesome info):
http://home.netcom.com/~bsundahl/kno...nockSounds.htm
^^^ In a way, yes. Basically, you can usually get away with least amount of ignition advance when you're at or near the engine's VE. For example, at 4000RPMs, for a given load, you will be able to advance to some timing X. That happens to be near the engine's VE point. As you climb through the RPMs, given the load is fairly stable, you can start advancing the timing from there on without inducing knock, X+1 at 4300, X+2 at 4600, etc. To spin it another way, if you were to set the timing to a single value for the entire RPM range, 1000-7000 RPMs, X+10 which you can get away with at 6000RPMs, as you climb down the RPMs, you'll knock more and more severely as you approach the VE point. I guess that was my thought I was trying to convey.
^^^ This is a tuning approach I disagree with Basically, you go on the street, you start knocking because you're heat soaking. The reason for that is because you're ingesting hotter air. Hotter air has higher detonation affinity. I think we can all agree on that. For example, let's say, at RPM X, load Y, IAT 100F, you can get away with 25 degrees of advancement. Now, if you were to take the same conditions, X and Y and change the IAT to 150F (not uncommon depending on how good your intake is), you will most certainly knock just because of the properties of air you're taking in. So, looks like you come from the school of thought that in situation like this, you throw some fuel at it for cooling purposes and call it fixed. The problem I see with that is that it doesn't actually fix the real issue here. So you got it to work right today when it's hot. Great! 5 months later, it gets cold, you're dumping extra fuel for no good reason and you're leaving safe power on the table.
To correctly fix this, you apply IAT compensation to the base ignition map. IIRC, UTEC does this and so some other OEM ECUs I've seen. This idea seems to be popular from what I can tell and that's because it works. Basically, you have another 2D map that applies a timing correction to base timing, according to IAT readings. For example, 30F correction +2, 50F correction +1, 70F correction 0, 90F correction -1, 110F correction -2, etc. So, when you tune, you get the base map working right, and call that your point 0 in your comp map. In the example I just mentioned, that's 70F. From there on, as IATs drop, you can add timing slowly and safely to make more power. As temps rise from your baseline, start pulling timing to compensate for the knock inducing temps by reducing the timing which was the problem in the first place. This way, you keep your fueling right, you don't introduce odd AFR hills and valleys in your fuel curve and things work reliably through the seasons.
I apologize for the long response. Once I get blabbing about tuning, there's no end in sight
I don't take offense to you questioning my statements. I'm glad people are thinking with their own heads and not just assuming everything others post is right. Glad you're doing that. Generally, there are various schools of thought when it comes to tuning and different people try to get to the same point in different ways. Are some ways better than others? Probably.Anyways, I don't think I follow this:
Originally Posted by SamuraiSam
Absolutely on a well-designed higher compression engines trying to run any reasonable amount of boost, the fuel will be THE limitation (as opposed to an engine being knock limited)
Originally Posted by SamuraiSam
When you can't tune to MBT like on the VQ with pump gas I've been instructed to watch the tractive effort/instantaneous torque output per load site and look at the 'gain' as timing is added. If you were to plot out the torque gain per degree of timing you generally see a 'bell curve' effect - as you get closer to the detonation threshold at any one load site, the TE gain becomes incrementally smaller per degree of timing added. Just by paying attention to this curve you should be able to arrive at powerful yet safe values while avoiding the deliberate knocking method. I'm not saying you're never going to knock during the tuning session, but it should be possible to keep from knocking while under full boost with the 'plateau' method.
The assumption is that you have a good idea where you should be roughly. If you advance a couple degrees too far and you start seeing knock, pull it back. The knock you experienced at the threshold is mild and will not cause damage to the engine. Inducing some knock during tuning is unavoidable, and I think we agree there. Even stock cars that have dynamic timing advance do it to some degree and they're set up that way from factory. The key is to not be a bone head and continue to advance when the engine is telling you to lay off. That's just (un)common sense.
I've used det-cans in the past for knock detection. I also used stock knock sensor coupled with knock correction feedback in the ECU (not Nissan ECU) to see when the ECU thinks it is knocking which it was actually amazingly good at. There are some limitation to what the ECU can detect as far as knock though. Believe it or not, your ears are the most sophisticated listening device you can get so use them with an amplification device and you can't go wrong. More than you ever wanted to know about knock and how to measure it (awesome info):
http://home.netcom.com/~bsundahl/kno...nockSounds.htm
Originally Posted by SamuraiSam
BTW - I think you meant to say that you'd find the engine more prone to knocking [due to overly advanced ignition] near the VE peak / torque peak
Originally Posted by SamuraiSam
Usually though any additional knocking on the street that didn't exist on the dyno is going to be due to a heat soak issue instead of too much timing, so you might want to then bump up your target AFR at that load row and add a bit more fuel for thermal management sake. My guess method would be that if you are hitting a max of 250 kpa and you would be seeing knock due to heat issues on the street at 200kpa (you can check the air intake temp sensor datalog to verify) to bump up each row starting with the problem row another .2 or .3 AFR and see where that goes.
Basically, you go on the street, you start knocking because you're heat soaking. The reason for that is because you're ingesting hotter air. Hotter air has higher detonation affinity. I think we can all agree on that. For example, let's say, at RPM X, load Y, IAT 100F, you can get away with 25 degrees of advancement. Now, if you were to take the same conditions, X and Y and change the IAT to 150F (not uncommon depending on how good your intake is), you will most certainly knock just because of the properties of air you're taking in. So, looks like you come from the school of thought that in situation like this, you throw some fuel at it for cooling purposes and call it fixed. The problem I see with that is that it doesn't actually fix the real issue here. So you got it to work right today when it's hot. Great! 5 months later, it gets cold, you're dumping extra fuel for no good reason and you're leaving safe power on the table.To correctly fix this, you apply IAT compensation to the base ignition map. IIRC, UTEC does this and so some other OEM ECUs I've seen. This idea seems to be popular from what I can tell and that's because it works. Basically, you have another 2D map that applies a timing correction to base timing, according to IAT readings. For example, 30F correction +2, 50F correction +1, 70F correction 0, 90F correction -1, 110F correction -2, etc. So, when you tune, you get the base map working right, and call that your point 0 in your comp map. In the example I just mentioned, that's 70F. From there on, as IATs drop, you can add timing slowly and safely to make more power. As temps rise from your baseline, start pulling timing to compensate for the knock inducing temps by reducing the timing which was the problem in the first place. This way, you keep your fueling right, you don't introduce odd AFR hills and valleys in your fuel curve and things work reliably through the seasons.
I apologize for the long response. Once I get blabbing about tuning, there's no end in sight
11-01-2007, 06:53 AM
#33
Originally Posted by athenG
I'm disputing that 11.8 is not conservative on VQ. You are giving an advice on a VQ motor right? Well I'm just stating that no VQ Tuner will run their A/F this high especially on peak TQ and pump gas. If this is conservative then why do I see many Subaru and Mitsu performance cars which run as rich as 10 to 1 stock on the dyno? and even Most RB Motors running as little as 9 psi will be in the high tens factory? That I think is conservative and OEM tend to do that just for added safety.
I'm no expert here but I'm just stating what are the consensus here. This is also the reason why people should go to a tuner that has experience on their car.
I'm no expert here but I'm just stating what are the consensus here. This is also the reason why people should go to a tuner that has experience on their car.
So, if you think you can run 12.0 at high loads, WITHOUT alcohol injection, on a FI car, I'd like to know how. I want to know the secret
11-01-2007, 07:11 AM
#34
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Originally Posted by Ziggyrama
To correctly fix this, you apply IAT compensation to the base ignition map. IIRC, UTEC does this and so some other OEM ECUs I've seen. This idea seems to be popular from what I can tell and that's because it works. Basically, you have another 2D map that applies a timing correction to base timing, according to IAT readings. For example, 30F correction +2, 50F correction +1, 70F correction 0, 90F correction -1, 110F correction -2, etc. So, when you tune, you get the base map working right, and call that your point 0 in your comp map. In the example I just mentioned, that's 70F. From there on, as IATs drop, you can add timing slowly and safely to make more power. As temps rise from your baseline, start pulling timing to compensate for the knock inducing temps by reducing the timing which was the problem in the first place. This way, you keep your fueling right, you don't introduce odd AFR hills and valleys in your fuel curve and things work reliably through the seasons.
I apologize for the long response. Once I get blabbing about tuning, there's no end in sight
I like it when you starti blabbing... I learn more new things.
Last edited by athenG; 11-01-2007 at 07:13 AM.
11-01-2007, 08:30 AM
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Ahh i wish i could read through everything and write some stuff up this second but I have stuff to do, i'll be back today or tomorrow guys. Thanks in advance for all the info
11-01-2007, 10:29 AM
#36
Originally Posted by athenG
hhhmm, based on what I have read, I was advised to only use Fuel for Temp Correction in Utec. Your post seem to make sense but isn't that adding/Sub Fuel Correction should be also suffice with the Temp Compensation in Utec?
I like it when you starti blabbing... I learn more new things.
I like it when you starti blabbing... I learn more new things.
My school of thought is to establish the fueling first and then work with timing to extract extra power. I always want to be within certain AFR, no matter what IATs I see. If that means that I knock with that AFR with high IATs, I fix it by reducing advancement that is based directly on the IAT that is causing the issue in the first place.
I am just not a big fan of fixing timing issues with fueling. When you knock because of IATs, it's because you're advancing too far so you should fix that and not apply, as I see it, a bandaid in form of extra fuel. Also, if detonation is severe enough, no extra fuel will fix that and there is such a thing as too much fuel
which can be disastrous (cylinder wash). Although I doubt you'll need to worry about that.Different strokes for different folks
In the end, would going to 10.8 with extra 2 degrees of advancement be better than 11.0 with 2 degrees less? Good question
11-01-2007, 10:51 AM
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I guess I was not clear enough, my post was not intended on the Knock and how to correct them. I agree on your method and I was just asking if I should just leave the Timing Adjustment to 0 in UTEC when compensating on temp change.
For example, I was tuned around high 60F to low 70F with IAT around mid 40C. Now that my IAT is around 20's coz of the weather plus having a better air flow on my Bumper, I just have Utec compensate on the Fuel side since the air is more denser. I was advice to just correct the Fuel using the Temp Compensation and leave the timing as is. If in case I do see knock and my A/F is on spot on where I wanted it (11.0-11.5) then the logical way is to pull some timing.
For example, I was tuned around high 60F to low 70F with IAT around mid 40C. Now that my IAT is around 20's coz of the weather plus having a better air flow on my Bumper, I just have Utec compensate on the Fuel side since the air is more denser. I was advice to just correct the Fuel using the Temp Compensation and leave the timing as is. If in case I do see knock and my A/F is on spot on where I wanted it (11.0-11.5) then the logical way is to pull some timing.
11-01-2007, 10:59 AM
#38
Originally Posted by athenG
I guess I was not clear enough, my post was not intended on the Knock and how to correct them. I agree on your method and I was just asking if I should just leave the Timing Adjustment to 0 in UTEC when compensating on temp change.
For example, I was tuned around high 60F to low 70F with IAT around mid 40C. Now that my IAT is around 20's coz of the weather plus having a better air flow on my Bumper, I just have Utec compensate on the Fuel side since the air is more denser. I was advice to just correct the Fuel using the Temp Compensation and leave the timing as is. If in case I do see knock and my A/F is on spot on where I wanted it (11.0-11.5) then the logical way is to pull some timing.
For example, I was tuned around high 60F to low 70F with IAT around mid 40C. Now that my IAT is around 20's coz of the weather plus having a better air flow on my Bumper, I just have Utec compensate on the Fuel side since the air is more denser. I was advice to just correct the Fuel using the Temp Compensation and leave the timing as is. If in case I do see knock and my A/F is on spot on where I wanted it (11.0-11.5) then the logical way is to pull some timing.
I guess my question then would be, why would you want to do that? Your AFR is determined on the amount of air you're taking in, which is why you have a MAF sensor...or a MAP if you're really serious.
11-01-2007, 12:40 PM
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With FI, we typically use MAP and Utec has it's own Table Map for fuel on various loadXRPM. I'm no expert but isn't that as temperature drops air get denser and with that your A/F will be of? So let say i'm tuned to a perfect 11.3 A/F at 45C IAT and as the weather drops and my IAT drop to 15C, will my A/F will be the same with out any compensation?
11-01-2007, 07:05 PM
#40
Originally Posted by athenG
With FI, we typically use MAP and Utec has it's own Table Map for fuel on various loadXRPM. I'm no expert but isn't that as temperature drops air get denser and with that your A/F will be of? So let say i'm tuned to a perfect 11.3 A/F at 45C IAT and as the weather drops and my IAT drop to 15C, will my A/F will be the same with out any compensation?