High Altitude Tuners: Ignition Map Question.
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High Altitude Tuners: Ignition Map Question.
As any of you that live at high altitudes already know, there is a discrepancy between map sensor readout and boost guage readings. I don't know the whole story behind why, but I do know that the map sensor gives a false reading at high altitude which can be substantial. In my case I am just under two full columns off (in Crome Pro, but it's the same on Hondata) or ~3psi.
Anyways, fuel tuning is no big deal, because you just adjust the cell that your car is reading from at any given point to achieve the AFR you want and disregard the boost level at the column heading. No big deal. But something I had never thought about until just recently, is that when you are street tuning a car, and you can'tget on the dyno, most people just take the stock ignition map and either do some sort of a step retard or a certain amount of retard per lb. of boost.
But what I'm wondering, and maybe this is a stupid question, is whether or not that retard should be moved back the same number of columns as the fuel table. And if so, shouldn't the whole ignition map be moved over as well as the retarded values? Certainly a dyno and maybe a knock detector would simplify this tuning, but what about all these ppl that create ignition maps purely by applying a retard to the whole map rather than actually tuning the ignition.
Any insight would be appreciated!!
Anyways, fuel tuning is no big deal, because you just adjust the cell that your car is reading from at any given point to achieve the AFR you want and disregard the boost level at the column heading. No big deal. But something I had never thought about until just recently, is that when you are street tuning a car, and you can'tget on the dyno, most people just take the stock ignition map and either do some sort of a step retard or a certain amount of retard per lb. of boost.
But what I'm wondering, and maybe this is a stupid question, is whether or not that retard should be moved back the same number of columns as the fuel table. And if so, shouldn't the whole ignition map be moved over as well as the retarded values? Certainly a dyno and maybe a knock detector would simplify this tuning, but what about all these ppl that create ignition maps purely by applying a retard to the whole map rather than actually tuning the ignition.
Any insight would be appreciated!!
#3
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Re: High Altitude Tuners: Ignition Map Question. (Ibiza)
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Re: High Altitude Tuners: Ignition Map Question. (flood)
arghhh, but i hate the uberdata forums, i don't run uberdata, and the likelihood of finding someone there running at high altitude who also has a comprehensive understanding of ignition tuning is a lot less than here.
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Contact SERVION from HRC hondaracingcrew.com.... Colorado tuner for real. Might be able to help you better from someone with experiance with this.
#6
Re: (PK SPEED)
I dont think you have tons to worry about as long as you have a PA (atmospheric pressure) sensor and you havent disabled it in Crome. Even if you have it disabled, i wouldnt worry tons as long as your AFRs are in check.
Really, at higher altitudes you are just pushing less air because its harder for the engine to "suck" in air at a higher altitude.
Really, at higher altitudes you are just pushing less air because its harder for the engine to "suck" in air at a higher altitude.
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Re: (xenocron)
Thx, that's what I'm looking for. I know some pretty reputable tuners around here, but I don't get a chance to see them and ask them in person very often.
Anyone else get kinda tired of all these threads ending up in go to the Uberdata forums? What are they, the Gustapo over there?
Anyone else get kinda tired of all these threads ending up in go to the Uberdata forums? What are they, the Gustapo over there?
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#8
Re: (Ibiza)
I think this is rather simple? If the ECU sees 10lb of boost as 7lb, then your 7lb collumn (whether it be timing or fuel) reflects the 10lb actual circumstance. So if your stock timing map is set up with the step retard, you should put the 10lb collumn where the 7 lb collumn is, and find out how many inches it is off, and that is how you can place the timing locals in the correct position.
Regardless, if the ECU thinks X is Y, place the X where the Y normally goes. (x=10, y=7 in this case)
Regardless, if the ECU thinks X is Y, place the X where the Y normally goes. (x=10, y=7 in this case)
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Re: High Altitude Tuners: Ignition Map Question. (Ibiza)
Are you sure it's reading incorrectly?
Atmospheric pressure can easily be 3 psi less than at sea level at very high(~5000+ ft) altitudes. Your boost gauge reads in gage pressure(psig), which is pressure over ambient(which is not necessarily 14.7 psi depending on your altitude). Your MAP sensor is reading in absolute pressure(psia), which is atmospheric ambient pressure + boost pressure.
I think the problem here is that you're expecting atmospheric pressure to be 14.7 psi, but it's NOT. In fact, pressure at 5000 ft is only 12.2 psi, or 2.5 psi less than at sea level.
So it seems reasonable to me that your MAP sensor is reading approximately the right absolute pressure in your intake manifold.
How you'd change your timing is that you might want to pull a degree or two out of some of the higher boost areas since your compressor is going to work much harder at a higher pressure ratio to achieve that same absolute pressure that's easier to get at sea level. So you might have a bit more heat to contend with for the same pressures you'd see in your cylinder as the sea level guy. It shouldn't take radical changes though.
Atmospheric pressure can easily be 3 psi less than at sea level at very high(~5000+ ft) altitudes. Your boost gauge reads in gage pressure(psig), which is pressure over ambient(which is not necessarily 14.7 psi depending on your altitude). Your MAP sensor is reading in absolute pressure(psia), which is atmospheric ambient pressure + boost pressure.
I think the problem here is that you're expecting atmospheric pressure to be 14.7 psi, but it's NOT. In fact, pressure at 5000 ft is only 12.2 psi, or 2.5 psi less than at sea level.
So it seems reasonable to me that your MAP sensor is reading approximately the right absolute pressure in your intake manifold.
How you'd change your timing is that you might want to pull a degree or two out of some of the higher boost areas since your compressor is going to work much harder at a higher pressure ratio to achieve that same absolute pressure that's easier to get at sea level. So you might have a bit more heat to contend with for the same pressures you'd see in your cylinder as the sea level guy. It shouldn't take radical changes though.
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Re: High Altitude Tuners: Ignition Map Question. (Def)
MAP sensor is an absolute pressure where as boost guage is a dial pressure, ie different between MAP and the atmosphere.
Lower atmosphere means the Boost guage will read higher than MAP sensor.
Simple.
Lower atmosphere means the Boost guage will read higher than MAP sensor.
Simple.
#11
That's a good point. Boost is relative to what the atmospheric pressure is. But the MAP sensor messures density, so the fact that it measures a lower MAP value even though boost is technically higher doesn't mean you're pushing more air. The ignition advance/retard is relative to the air density so it doesn't matter what elevation you are in -- you still want the same amount of timing for the same amount of air.
In short, DO NOT reduce the timing based on your boost gauge, base it on the MAP sensor.
In short, DO NOT reduce the timing based on your boost gauge, base it on the MAP sensor.
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Re: (johncui)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johncui »</TD></TR><TR><TD CLASS="quote">That's a good point. Boost is relative to what the atmospheric pressure is. But the MAP sensor messures density, so the fact that it measures a lower MAP value even though boost is technically higher doesn't mean you're pushing more air. The ignition advance/retard is relative to the air density so it doesn't matter what elevation you are in -- you still want the same amount of timing for the same amount of air.
In short, DO NOT reduce the timing based on your boost gauge, base it on the MAP sensor.</TD></TR></TABLE>
His IATs will be higher given the same turbo for the same absolute pressure as his setup would produce at sea level. Heck, given ANY turbo they will be higher just because the air had to be compressed that much more.
So it might not be a bad idea to trim down the timing a degree or two at higher absolute pressure.
In short, DO NOT reduce the timing based on your boost gauge, base it on the MAP sensor.</TD></TR></TABLE>
His IATs will be higher given the same turbo for the same absolute pressure as his setup would produce at sea level. Heck, given ANY turbo they will be higher just because the air had to be compressed that much more.
So it might not be a bad idea to trim down the timing a degree or two at higher absolute pressure.
#13
Re: (Def)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Def »</TD></TR><TR><TD CLASS="quote">
His IATs will be higher given the same turbo for the same absolute pressure as his setup would produce at sea level. Heck, given ANY turbo they will be higher just because the air had to be compressed that much more.
So it might not be a bad idea to trim down the timing a degree or two at higher absolute pressure.</TD></TR></TABLE>
The ECU should compensate for any IAT differences...especially as slight as they may be.
His IATs will be higher given the same turbo for the same absolute pressure as his setup would produce at sea level. Heck, given ANY turbo they will be higher just because the air had to be compressed that much more.
So it might not be a bad idea to trim down the timing a degree or two at higher absolute pressure.</TD></TR></TABLE>
The ECU should compensate for any IAT differences...especially as slight as they may be.
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Re: (xenocron)
Man, this is like a whole pgmfi reunion at HT!! I was going to ask the question over there, but I figured more ppl would see it sooner here.
Anyways, can I just slip in a quick plug for John's software?! I was reluctant to plunk down the $150 for CromePRO, since there is a free version and datalogging programs that are available out there....but it has been worth every penny and more. I love the program, and it has made tuning a breeze. I have had it less than a month, and have three cars tuned quite succesfully.
Anyways, can I just slip in a quick plug for John's software?! I was reluctant to plunk down the $150 for CromePRO, since there is a free version and datalogging programs that are available out there....but it has been worth every penny and more. I love the program, and it has made tuning a breeze. I have had it less than a month, and have three cars tuned quite succesfully.
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Re: (xenocron)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xenocron »</TD></TR><TR><TD CLASS="quote">The ECU should compensate for any IAT differences...especially as slight as they may be.</TD></TR></TABLE>
Honda ECUs adjust timing based on the IAT? I know way more about MAF ECU's, so I'm not sure. If so then that's good.
The amount will not be as insignificant as you think it will.
Let's say you want 24.7 psia, or about 10 psi over sea level pressure.
At 5000 ft you'll have to run a pressure ratio of about 2. At sea level that is more like a PR of a little less than 1.7. That's a pretty big difference in the amount of heat you're going to put into the air compressing it. That's the same heat difference in going from 10 psig at sea level to near 15 psig, which is definitely a factor.
Honda ECUs adjust timing based on the IAT? I know way more about MAF ECU's, so I'm not sure. If so then that's good.
The amount will not be as insignificant as you think it will.
Let's say you want 24.7 psia, or about 10 psi over sea level pressure.
At 5000 ft you'll have to run a pressure ratio of about 2. At sea level that is more like a PR of a little less than 1.7. That's a pretty big difference in the amount of heat you're going to put into the air compressing it. That's the same heat difference in going from 10 psig at sea level to near 15 psig, which is definitely a factor.
#16
Re: (Def)
i still think it would be safest/most correct to move everything over one collumn.
Regardless of why the ecu sees the difference in pressure, it still does. And for some specific pressure that is going into your intake manifold the ecu sees a different one. So your fuel value will be correct (assuming you tuned it with a wideband) but the timing value will not be optimized. (not that a stock timing value is 'optimized,' but it should be a better starting point)
Regardless of why the ecu sees the difference in pressure, it still does. And for some specific pressure that is going into your intake manifold the ecu sees a different one. So your fuel value will be correct (assuming you tuned it with a wideband) but the timing value will not be optimized. (not that a stock timing value is 'optimized,' but it should be a better starting point)
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Re: (Si Shane)
Your post makes no sense.
The turbo is there to deliver the actuator set pressure to the manifold. Thats its job ad is why it was originally developed for use on Aircraft to fly higher.
Now history lesson over we can move to adiabatic efficiency. The turbo will provide the same boost to the inlet manifold its just that the pressure ratio will be higher which will normally mean not only is there more compression going on, but also the efficiency of the compressing reduces so even more heat is added to the charge.
Problem is that the higher pressure ratio places more load of the turbo and hence the turbine workrate such that exhaust manifold pressure will be much higher at altitude with inlet manifold pressure staying the same, on VTEC you could have more problems of reversion and more exhaust residuals staying in the chamber...
There is no quick fix. Map both altitudes properly really.
The turbo is there to deliver the actuator set pressure to the manifold. Thats its job ad is why it was originally developed for use on Aircraft to fly higher.
Now history lesson over we can move to adiabatic efficiency. The turbo will provide the same boost to the inlet manifold its just that the pressure ratio will be higher which will normally mean not only is there more compression going on, but also the efficiency of the compressing reduces so even more heat is added to the charge.
Problem is that the higher pressure ratio places more load of the turbo and hence the turbine workrate such that exhaust manifold pressure will be much higher at altitude with inlet manifold pressure staying the same, on VTEC you could have more problems of reversion and more exhaust residuals staying in the chamber...
There is no quick fix. Map both altitudes properly really.
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Re: (Def)
Thx for all the input guys. I think this is kinda of an interesting question, because it really requires an understanding of not only how a motor reacts to the thinner air, but also how the Honda ecu works and how it reacts to these differences.
I'm gonna go ask some local tuners and get some input from them as to their methods (and to see if there is any logic behind it )
I'm gonna go ask some local tuners and get some input from them as to their methods (and to see if there is any logic behind it )
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Re: (JonnyCoupe)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JonnyCoupe »</TD></TR><TR><TD CLASS="quote">
Now history lesson over we can move to adiabatic efficiency. The turbo will provide the same boost to the inlet manifold its just that the pressure ratio will be higher which will normally mean not only is there more compression going on, but also the efficiency of the compressing reduces so even more heat is added to the charge.</TD></TR></TABLE>
Not necessarily. You could move to a more efficient part of the map since your mass flowrate will be similar to the absolute pressure the engine sees at sea level, but the compressor is operating at a higher pressure ratio. In fact, most turbos would tend to see a higher adiabatic efficiency in the midrange/top end of the powerband at higher altitude for a given boost pressure just because you are letting it see less mass flowrate.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">
Problem is that the higher pressure ratio places more load of the turbo and hence the turbine workrate such that exhaust manifold pressure will be much higher at altitude with inlet manifold pressure staying the same, on VTEC you could have more problems of reversion and more exhaust residuals staying in the chamber...
</TD></TR></TABLE>
You are missing that the turbine will also get a bit of "help" from the lower atmospheric pressure since it will be able to operate at a higher pressure ratio with the same exhaust manifold pressure.
It's hard to say really. You could see higher exhaust manifold pressures, or you could see very similar ones to the same setup running the same boost at sea level. There is no general rule here.
Another thing to think about is that you're going to heat the air up more compressing it more, but then it's harder to cool that hot air down since your IC is using low density thin air to cool down this much more dense and hotter intake charge. So with the same setup, expect higher post compressor temps as well as a slightly smaller temperature delta across the intercooler core. Higher temps will almost surely be seen, so again, I'd knock back the timing a degree or two in the area around your "target boost."
Now history lesson over we can move to adiabatic efficiency. The turbo will provide the same boost to the inlet manifold its just that the pressure ratio will be higher which will normally mean not only is there more compression going on, but also the efficiency of the compressing reduces so even more heat is added to the charge.</TD></TR></TABLE>
Not necessarily. You could move to a more efficient part of the map since your mass flowrate will be similar to the absolute pressure the engine sees at sea level, but the compressor is operating at a higher pressure ratio. In fact, most turbos would tend to see a higher adiabatic efficiency in the midrange/top end of the powerband at higher altitude for a given boost pressure just because you are letting it see less mass flowrate.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">
Problem is that the higher pressure ratio places more load of the turbo and hence the turbine workrate such that exhaust manifold pressure will be much higher at altitude with inlet manifold pressure staying the same, on VTEC you could have more problems of reversion and more exhaust residuals staying in the chamber...
</TD></TR></TABLE>
You are missing that the turbine will also get a bit of "help" from the lower atmospheric pressure since it will be able to operate at a higher pressure ratio with the same exhaust manifold pressure.
It's hard to say really. You could see higher exhaust manifold pressures, or you could see very similar ones to the same setup running the same boost at sea level. There is no general rule here.
Another thing to think about is that you're going to heat the air up more compressing it more, but then it's harder to cool that hot air down since your IC is using low density thin air to cool down this much more dense and hotter intake charge. So with the same setup, expect higher post compressor temps as well as a slightly smaller temperature delta across the intercooler core. Higher temps will almost surely be seen, so again, I'd knock back the timing a degree or two in the area around your "target boost."
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Re: (Def)
Wow. This is all pretty interesting to me. Everybody's explanations seam to make sense, but not all of them are based in fact, or maybe it is incorrectly applied fact since there seem to be many different solutions proposed.
Is there anyone here that has some good experience with high altitude tuning? I know several of the bigger name racers here locally (several of which can be found on http://www.fastestfwdstreetcars.com) use the same map here as they do at low altitude. I'm guessing based on that that cells and columns do not need to be shifted, although there may be some consideration made by way of timing while they are at high altitude (i.e. timing at the dizzy, or timing adjustments made to the whole map.)
Any other thoughts?
Is there anyone here that has some good experience with high altitude tuning? I know several of the bigger name racers here locally (several of which can be found on http://www.fastestfwdstreetcars.com) use the same map here as they do at low altitude. I'm guessing based on that that cells and columns do not need to be shifted, although there may be some consideration made by way of timing while they are at high altitude (i.e. timing at the dizzy, or timing adjustments made to the whole map.)
Any other thoughts?
#21
Re: (Ibiza)
Again...in a Honda ECU, there is a sensor called the PA sensor. Barometric pressure sensor. The ECU uses this as a reference for altitude purposes. It allows the ECU to know approximately at what altitude the car is running at so that it can make slight changes in the calculations it makes to inject fuel into your cylinders and control the timing of when the spark plugs fire.
You think honda made different maps for cars being shipped off to Denver? ...and then told them "you can't drive that car down out of the mountains"
You think honda made different maps for cars being shipped off to Denver? ...and then told them "you can't drive that car down out of the mountains"
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Re: (xenocron)
No I don't think that. I understand that the Honda ecu or any automotive ecu takes more things into account in a fraction of a second than most ppl could comprehend. However, I do think by turbo charging the motor you begin to throw some new factors into the mix that need to be accounted for.
On a side note, car manufacturers did use to offer re-tuned cars that were sold at high altitude. Especially with carburated cars this was a big factor.
On a side note, car manufacturers did use to offer re-tuned cars that were sold at high altitude. Especially with carburated cars this was a big factor.
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