Altitude vs. A/F Ratios

turbotudor wrote:

well he was probably just a hair lean then concidering elevation change and all the incedentals , that sucks either way. hope he gets it back together

Is this a myth for boosted cars???

Source: http://wahiduddin.net/calc/density_altitude.htm
For example, the lift of an aircraft wing, the aerodynamic drag and the thrust of a propeller blade are all directly proportional to the air density. The downforce of a racecar spoiler is also directly proportional to the air density. Similarly, the horsepower output of an internal combustion engine is related to the air density, the correct size of a carburetor jet is related to the air density, and the pulse width command to an electronic fuel injection nozzle is also related to the air density.


equation for air Density:
D= P/(R*T)

where: D = density, kg/m3
P = pressure, Pascals ( multiply mb by 100 to get Pascals)
R = gas constant , J/(kg*degK) = 287.05 for dry air
T = temperature, deg K = deg C + 273.15


For a naturally aspirated car, the pressure changes with elevation so this statment is ture. However on a boosted car the boost pressure is the pressure. 20psi in Billings is 20psi in denver.

This is something I ran across while studying to become a Mechanical Engineer. I am wondering if someone has real life experience that proves or contradicts this theory.

im talking about the difference in fuel tuning from elevation to elevation. if i take my car to vegas for instance, i would have to do 2 things for sure, pull some timing out and then fatten up my tune. air density, and atmospheric pressures are significantly different with even a 1000 foot elevation change. n/a or forced induction, it doesn't matter, tuning is key for whatever elevation you live at. i guess the only real difference would be in wheather the vehicle is carbed or injected. mine is a blowthrough system, fuel injected will usually fix itself to a certain degree, mine wont. i have to do it the hands on approach.

You make my exact point, something else is going on with forced induction, if in fact you do have to make those changes (I would assume you would know from experience)

you say atmospheric pressure changes with elevation, I completly agree. But look at the equation for air density. It is based on pressure (that is your boost pressure for boosted cars, it has nothing to do with atmospheric pressure), R which is a constant, and T for temperature (which ambient air temps may or may not change, but that is not the arguement)

I am just throwing this out for discussion because to me it doesn't make sense. I am just wondering if it is something I am missing or don't understand. Or if it really is a myth.

Who knows!! I am off to trouble shoot my wiring.

EDIT: did some quick reading and here is what I found.

With less atmospheric pressure (higher elevation) there is less particles in a certain space, so your turbo must spin faster to pack in the same number of oxygen particles as it did at sea level to obtain the same pressure. So there is a negative affect on spool up that could shift your power curve. Once full boost is reached, then everything is the same.... but at higher altitude that will be at a higher rpm.

Does that make sense? Have you witnessed slower spool at higher altitudes?

b1r-ts indeed it may seem that way. atompheric pressure is a consistant 14.7psi. that is why boost never changes. now densness of air can change (volume). pressure and voulume are 2 different things

shit i didnt see josh's post

Novaflash2002 wrote:

b1r-ts indeed it may seem that way. atompheric pressure is a consistant 14.7psi. that is why boost never changes. now densness of air can change (volume). pressure and voulume are 2 different things

it's late and I think that I might have just figured out my wiring problem on my car..... so I am fried (ha ha bad joke)

this statement makes no sense. Atmospheric pressure is not constant, it is all relative to your elevation (we already agreed upon that a few post back)

Boost never changes because your waste gate determines boost pressure (or I guess you could say your boost controller)

The density of air can change by changing volume, pressure, or Temperature. Noble gas law: PV =nRT. I am not sure what your point was with that statement but your engine displacement doesn't change with altitude, so the density of air is not affected by a volume change (again that statment confuses me.)


See if this logic makes more sense to you guys... I will show how the whole equation brakes down.

noble gas law: PV = nRT (hold true for all gases)
Air Density: (mass/volume) ...... n/V (using the same symbols as above)

Simplify the two and you get: n/v = P/(R*T) This is the equation I posted earlier

in words that equations states: air density equals pressure divided by the product of the gas constant times Temprature

So the only way to make air denisty higher is increase the pressure or decrease the temprature....... and again becuase your car is boosted your pressure doesn't change with elevation.

but the tune of air fuel ratio does. take a carberated car from our current elevation of 3750 feet above sea level actual, and drive that bitch to old faithful. i dont give a fuck if you make 12,000 hp at 3750 feet, it will fell and drive like a 125 horse first gen small block with smog controls. i do make my statements from experience. math and shit can say one thing, but put it in actual world tests and it will prove that 2 +2 does not equal 4, more like 3.5... im not trying to argue, all im saying is higher elevation means you need more timing and less fuel to correctly burn your fuel. lower elevation equals less timing and more fuel to burn efficiently.

i should not have said volume. take a plastic bag for instance. just put enuf air in it so it does not flatten out in billings. drive to the top of bear tooth pass it will be as flat as a pancake. now take it to the coast and it will buldge like a mother. same volume that entire time.
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your 1 bar map is good for atmospheric pressure. 2 bar is 14.7 psi and 3 bar 29.4. likeyou stated you have to make your engine work harder, thats why the waste gate controlls your boost. if it works off of atmospheric pressure wouldnt the same car with a weather change make less boost if the borometer (atmopheric pressure) went to like 29.4 wouldnt that car have no boost at all?

what is changing is the Mass of the air (weight does not exist lol thats a chemisrty thing). that is why colder air has more mass or as we call it (denser/heavier) and warmer has less mass (thinner/lighter).

i kNow that on a warmer day in billings the exact same car will not make the same boost at the same rpm with the same tune everything the same as a cold day via the airs different mass'. thats not a change in atmosperic pressure it is a change in the airs mass.


ill have to talk to my brother about this shit, he can expain things a bit easyer than i can that why he is an engineer and i am the enforcer.

I thought 1 bar = 14.5 psi?

I do know from my experience yes on a cooler day the car definitely feels much more peppy.. I also know that when there are changes in atmospheric pressure it affects the way the car runs. I've monitored atmospheric pressure from my car during tuning and here in billings it has been as low as 12.8 and as high as 13.2. But I usually don't see it deviate from that range. I would leap for joy if I ever were to read an atmospheric pressure of 14 or higher here in Montana, but it won't happen because we are not at sea level. Closer to sea level = more powa, easier boost.

I've had to make changes to my atmospheric compensations tables within my map, adding wastegate duty at lower pressures to try to compensate. But you can't do it too much as of course the turbo is working harder to get the same manifold pressure.

1 Bar is equal to atmospheric pressure wich is 14.7lbf at sea level.

http://en.wikipedia.org/wiki/Atmospheric_pressure

so the real question is.....is 14.7 atmospheric pressure really zero? is a car sitting there not running already boosted to 14.7lbf? or is that canceled out when you start it up and you have vacuum? or do they cancel each other out?

Thanks for discussing.... hopefully no one thinks I am being a dick since I don't know some of you. I am just thinking through things and trying to understand. By no way do I think I have all the exact answers and understand things.

Josh are you refering to a boosted carbuerated car? or NA? Or maybe it doesn't even matter.

Novaflash2002 wrote:

i should not have said volume. take a plastic bag for instance. just put enuf air in it so it does not flatten out in billings. drive to the top of bear tooth pass it will be as flat as a pancake. now take it to the coast and it will buldge like a mother. same volume that entire time. This is a perfect example to show how atmoshperic pressure changes with elevation. You missed the wording at the end though. it's not costant voulme in the case of a balloon it can shrink and stretch.... it is however constant mass.
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your 1 bar map is good for atmospheric pressure. 2 bar is 14.7 psi and 3 bar 29.4. likeyou stated you have to make your engine work harder, thats why the waste gate controlls your boost. if it works off of atmospheric pressure wouldnt the same car with a weather change make less boost if the borometer (atmopheric pressure) went to like 29.4 wouldnt that car have no boost at all? I agree, your boost gauge is reading the boost generated by your turbo and has nothing to do with atmospheric pressure.

what is changing is the Mass of the air (weight does not exist lol thats a chemisrty thing). that is why colder air has more mass or as we call it (denser/heavier) and warmer has less mass (thinner/lighter).

i kNow that on a warmer day in billings the exact same car will not make the same boost at the same rpm with the same tune everything the same as a cold day via the airs different mass'. thats not a change in atmosperic pressure it is a change in the airs mass. Replace where you said mass and use density it makes it easier to see the logic. Sorry i use equations because that is how my brain works. (air density) n/v=P/RT you can see right there that as the temp. changes the air density will change. higher temp equals lower density.... i.e. makes your car work harder.




ill have to talk to my brother about this shit, he can expain things a bit easyer than i can that why he is an engineer and i am the enforcer.

A 1 bar map sensor measures up to 14.7psi (already present due to our atmosphere) +0 psi theoretically. However typically its more like the 14.7 of the atmospheric pressure plus 1-7 psi depending on the voltage curve of the sensr and the ECU resolution. A 3bar can read 29spi more than atmosphere, that is why its called a 3br. 3x14.7=44.1 psi. Although usually to run near 29 or higher you would need a 5 bar map sensor.

The air density, pressure or temps whill change and that is what is effecting the tune, however that is why so many cars use MAF sensors instead of Map sensors. Map Sensors are much tougher to fine tune and need more tuning depending on elevation. Similar to a carborated engine. MAF sensors can correct easier and are simpler to tune for all these variables. That is why so many older cars used MAF sensors. Now that ECU's have higher resolution the use of a MAP sensor makes more sense and fine tuning can be done for more situations. Also a lot of ECU's now days have corrections for barametric pressure and more precise intake air temperature sensors to be more accurate.

There are so many variable that some cars simple will change how they run but this should not be the case on a Subaru with the type of ECU and monitoring system it uses. I can drive my car all over and it always feels the same. If its really hot out the airflow % will be the same and it makes the same power. This is part of the reason I am still running a MAF sensor. Altough Its a restriction and would be nice to no longer run. I have huge cams, solid lifters and a large plenum intake manifold however it runs like a stock car with a lot more power. Temperature will have some effect but if you have a properly setup cooling/air cooling setup this will also be minimal. My car has made 460hp on both 60 and 100 degree days with no correction factor on the dyno to compensate for the temp differance.

The point B1R is making is very true that elevation on a boosted car should not effect the overall power output. Some things as said will benefit from minor tuning changes(temp, humidity, barametric pressure, etc.) but this is why when you dyno a boostted car you are not supposed to look at corrected numbers. The car should be making the same power and flowing the same amount of air regaurdless of elevation. Search the interweb and you will see when comparing number of NA engines corrected dyno numbers are compared all the time, however FI cars need to compare uncorrected numbers to accurately compare apples to apples.

Haven't kept up with this whole discussion but am I missing something?

This DA calc on dragtimes still allows correction for boosted cars. Only nitrous cars get no correction.

http://www.dragtimes.com/da-density-altitude-calculator.php

pv=nrt i rember this equasion for one reason i called it the pervert equastion. (little j/k there) yea im an idiot sometimes the more i thought about it atmospheric pressure has to change, or the weather wouldnt. to put it easier the higher you go the less air you have, that is why you can get away with more compression at higher alittudes. with pauls car was tuned in denver where it is 5280 feet, and billings elv is 3800 (thats a guess) he is running leaner, via the air is thicker particals are closer togehter. he has the same fuel but more air with it. o yea keep up with the equasins i havent seen many in a long time because i havent used them much any more. i got lazy and use a ti-92 to make it quicker and easier on myself lol.

oyea gm uses map and map sesners together. once you hit about 450 rwhp we tend to get rid of the mafs, and go to a speed denisty tune with the map and iat (intake air temp senser working togehter. the mafs tend to run out of air past 4500 rpm.

holy cow this conversation went completely too far... simple way to look at it.
a car tuned in denver(higher actual elevation than here) can be run here, but the tune will need to be changed due to actual elevation, air density and atmospheric pressure here.

Again I will have to agree to disagree on that. Depends on the car, sensors, ECU and engine. A complex and propely tuned setup will need no changes. There are many ECU's and sensors that can compensate for any change. It just depends on how much you wanna spend and how much engineering goes into. Same reason an OEM car can run the same all over the world on different gases.

thats right, but we are talking about a car that doesnot have the stock garbage in it, self tuning works on stock vehicles, but not one that is "tuned for such n such " the internal variables of an aftermarket tuning only will go so far. regaurdless, his shit blew up and he probably will take steps in the future to prevent it from happening again, hopefully...

im a firm beliver in runnning tad rich to prevent detonation. you can made a modified engine tune just as reliable as the std engine tune. but you sacrifice some power usually when you do. take my buddy jasons gto. he doesnt have knock sensors in it right now, so i am tuning old school with it (by ear listing for pinging). i know that i can pull more out of the engine but i dont because he hasnt fixed that yet.

Yeah, that is how I tune my car. You hear the knock and let off. I am planning on getting a very advanced knock system that works with the Autronic, but it is very expensive. It actually has 2 sensors, one for each side.

There is no need for anything that expensive, build some DET cans or even buy some. They make systems that you can run through your stereo system. I however am a strong believer that to get the most HP with a safe margin you need to make any timing changes on a dyno. If you can audibly hear detonation its already too late. Especially on a boosted car making lots of power. When you hear the pinging you are already damaging things. Higher HP just means you will have probably caused more damage. Not to mention that type of tuning works great on older V8's but now days most cars are not knock limited. If you are hearing detonation you have way overtimed your engine. Seems too many people these days think newer engines will make the most power right before knock which is just not the case. You can make as much if not more power with less timing and be no where near the knock limit.

The ultimate goal of tuning is making the most power with the least timing required. If you can run 7 degrees total timing and make the same power as 12 degrees why would you try and run more than 7? Thats why a dyno is so useful. You can watch for the Tq to drop as you add timing. Once you hit that back it off as much as you can while maintaning MBT and you will have a safe and fun setup.

Thanks to whoever started this a a seperate thread for me! Now we can go back to arguing!

haha

I think the main point is to think about the QUALITY of the air vs altitude. More specifically.... oxygen content of the air at what altitude.
Break it down simple..... OXYGEN(Air), Fuel, Ignition. The basis for the most basic camp fire. Same truth for anything with a flame. What is the important part of the air? Oxygen.
http://www.skyrunner.com/story/pikespeako2.htm
http://www.altitude.org/why_less_oxygen_at_altitude.htm
http://www.altitude.org/calculators/oxygencalculator/oxygencalculator.htm
http://www.allstar.fiu.edu/aero/oxygen.htm


This is why There is no compensation for Nitrous cars.... You are already force inducing oxygen into the car chemically. NO2 is one part nitrogen and two parts oxygen. Nitrous Oxide is NON-FLAMMABLE and the nitrogen does nothing for the engine.... we're using the two parts oxygen (oxidizer) to force feed the engine with chemistry. And this is why you have to fatten up the fuel mixture because you're tossing over twice as much oxygen into the engine.

I think you just have to look at it the right way. You are looking at it from an engineer standpoint like you're building an air plane and looking at air density. But air density really is not the focus.... it's the oxygen content. Air density is a measurement you can use to find out oxygen content.

Dr.Auto wrote:

I think you just have to look at it the right way. You are looking at it from an engineer standpoint like you're building an air plane and looking at air density. But air density really is not the focus.... it's the oxygen content. Air density is a measurement you can use to find out oxygen content.

You point out exactly what I am talking about. Oxygen content is what we care about, but oxygen content is directly related to air density... which is directly related to pressure by the noble gas law which I have referenced several times. So in a boosted car pressure does not vary and so oxygen content should not vary either.

I need to look back at my heat transfer book and look at the equations for an internal combustion engine. You can calculate power output of an engine using entropy.... entropy is the measure of storage energy in a substance. Entropy is determined by temperature and pressure, so again in a boosted car you never see a change in pressure. (its either entropy or enthalpy that I am referencing, I can't remember which word is correct right now but I know the principle is true.)

Since I am back on this topic I will try to clarify. I think spool up is affected by altitude but air density (i.e. oxygen content is not affected with a boosted car.... if you disagree look at the basic equation, it is as clear as it can be.... so please stop saying that it does change (BOOSTED CARS ONLY)

If you believe this argument, ask yourself this. Why does air density (oxygen content) vary with altitude, its because the pressure decrease the higher the alititude. But once it goes into your charge piping your turbo determines that pressure and that has nothing to do with altitude.

A quote from Wikipedia:
"The percentage of oxygen in air, at 21%, remains almost unchanged up to 70,000 feet (21,000 m). The RMS velocities of diatomic nitrogen and oxygen are very similar and thus no change occurs in the ratio of oxygen to nitrogen. However, it is the air pressure itself, the number of molecules (of both oxygen and nitrogen) per given volume, which drops as altitude increases."

I see what you're trying to say. And it's a valid argument. But no matter how you look at it altitude will effect even boosted cars.
It doesn't matter that you're 21psi of boost at sea level is still 21psi at 10,000ft. It's not the same oxygen content. There will be less oxygen content.

Something else to think about...... is 21psi boost at 10,000ft really 21psi? Or is it really 17psi considering baro at that altitude no matter what you're auto meter says?

One thing that I have always wondered about was oxygen injection to farther oxygenate the air going into the engine. But at what point does the cost vs result justify not just using NO2? lol

but there is still a starting point at whatever the adj elev is, and n/a, turbo, supercharged, and nitrous cars all go faster at lower elevations because of density of air and quality of air. why wasnt columbus wrong, and the earth was really flat, we wouldnt be having this conversation haha

b1r - TS wrote:

If you believe this argument, ask yourself this. Why does air density (oxygen content) vary with altitude, its because the pressure decrease the higher the alititude. But once it goes into your charge piping your turbo determines that pressure and that has nothing to do with altitude.

Please read the first part of this link http://www.skyrunner.com/story/pikespeako2.htm

I know this has to do with regards to the human body and breathable oxygen...... um...... but that's the same thing our engines do. Breath air and rley on the oxygen content in the air for the performance the same as the human body does.

The lowest 60 miles of the atmosphere is very well mixed and thus maintains roughly the same proportions of the different gasses is consists of. O2 is actually only a bit more than one fifth (21% by volume, 23.14% by mass) of the atmospheric gas. (Most of what you breath, 78% by volume, 75.51% by mass, is nitrogen.) Since the O2 part of the atmospheric pressure is constant, we can simply equate the percent decrease in total pressure to the percent decrease in O2. For example, from 1000 mb to 500 mb the pressure decreases by ½. The O2 partial pressure (pressure exerted by O2 portion of the gas) decreases from 231.4 mb (23.14% of 1000 mb) to 115.7 mb (23.14% of 500 mb), a reduction of ½ just like the total pressure.

Matt your article is just more support for my theory. The human body is a NA engine, put an oxygen maks on and then you have a boosted engine.That article talks about how the o2 content of air remains consistant at 21%... and then it goes on to talk about how the air density changes with elevation due to pressure. (I agree with all of this). But the key word there is pressure, boosted cars determine pressure. So yes 21psi is 21psi... even if you are at the bottom of the ocean (your charge piping is a closed system, atmospheric conditions do not affect your boost inside your piping because the piping is rigid...if it was a balloon that could expand and contract it would be a different story.)

Josh is now bringing a twist to the arguement (I agree, stupid Columbus he could have fixed all of this).
Cars do run faster at sea level, but that is due to a whole list of reasons.... one example being Air density or air quality whatever word you want to use, does affect how efficiently your turbo works and that is why you see correction factors but it does not affect your a/f ratio again because your boost pressure overrides all (and now we are back at our same arguement)

regaurdless, that fact still remains, an n/a car at sea level vs a n/a car at a higher elevation makes different hp due to that elevation. when you add boost or a power adder to this engine, power will increase but, the increase will be different because of the starting point of the n/a engine whether you are at sealevel or 10,000 feet.

I think the last sentence B1R said is a very good point. If you are at 8500 ft and the manifold pressure is 70 Kpa or you are at 700 ft and 1/4 throttle and your manifold pressure is at 70 Kpa, the pressure is the same hence the A/F ratio will be kept the same. What the sensors are seeing is the same volume of air. So the fact that a car may run different is a moot point. They may but the A/F ratio should be the same. For a given load/amount of air their should be the same amount of fuel. When you throw in other sensors like TPS or IAT corrections you may see a change. But that is not due to the elevation it self. You could see those same changes at sea level on a hot day. The Temps and throttle position are making the changes. Same reason you can run 1 psi at 50% throttle and it will feel much different than 1 psi at full throttle. The VE of the engine is effected by the restrictions of the TB.

The reason NA cars are more effected by altitude is because they typically have a VE of 60-70%, while boosted cars have a VE over 100%. Typically closer to 110% VE on a turbochaged car. So when the barometric pressure is say 70 Kpa then if you have 70Kpa manifold pressure you are at 100% VE. The NA engine can not get to 100% VE. So as the Barometric pressure decreases the amount that the engine can ingested is effected.

A turbo engine however will work differently here. The typical boost control is either atmo referenced with a target differential pressure or target absolute pressure. So the boost set at 21 psi will remain at 21 psi, however the compressor wheel speed may change to keep up. Higher speed at higher elevation.
This is why I don't consider the typical dyno correction factors to be relevant with turbocharged engines. It is a very common practice all around the world to not allow SAE correction factors on Turbo engines due to the lessened effect of Barometric and atmospheric differences. Also once its turbocharged the engine baseline of the NA engine has nothing to do with the power it will now make.

200kpa inside the manifold @ 20km = 200kpa inside the manifold @ 250,000 feet above the planets surface. Do you think space shuttle keeps the cabin pressurized at the levels around them in space (around 5kpa'ish) or replicate the pressure at sea level (give or take)?

so basically you are stating that the tune is always the same. okay, then that means that you can get a handata or whatever tuned computer and put it in your car and it will work.even though it was tuned at sea level. and you can take that computer and it makes, lets just say, 400 whp. you take that same setup to 10000 feet and it will still make 400whp? i dont think so. thats why my dads car ran a best of 10.20 at our track and then went to mission bc and ran a fuckin 9.70? gee thats weird, the car obviously mkes more power at lower elevation...

turbotudor wrote:

the increase will be different because of the starting point whether you are at sealevel or 10,000 feet.

This is the exact point.

turbotudor wrote:

so basically you are stating that the tune is always the same. okay, then that means that you can get a handata or whatever tuned computer and put it in your car and it will work.even though it was tuned at sea level. and you can take that computer and it makes, lets just say, 400 whp. you take that same setup to 10000 feet and it will still make 400whp? i dont think so. thats why my dads car ran a best of 10.20 at our track and then went to mission bc and ran a fuckin 9.70? gee thats weird, the car obviously mkes more power at lower elevation...

Yes... on a boosted car I would expect to see peak power the same. However what you won't see stay the same is the shape of the power curve and that is why your dad's car can run faster times at lower altitudes. Lower altitudes cause your car to work "easier".... turbo will spool up quicker and less heat will be generated. But once things get to there maximum boost pressure, aside from the benefit you are getting from the different temperatures the maxiumum power output will be the same.

Here is my same statment made by someone else with maybe better wording (source:http://www.ultimatecarpage.com/forum/technical-forums/14658-hp-loss-high-altitudes.html)
Quote:
Originally Posted by taz_rocks_miami
Exactly, that's why I just asked about normaly aspired engines. Turbo and Supercharged engines generaly don't care at what altitude the road your driving on is

They do if you are pushing along at max boost all the time
The turbo is setup to provide boost up to wastegate pressures. BUT the amount of boost is determined by the speed of the impellor ( driven by exhaust gas speed ) and the wastegate control.
So trubos take longer to get the bosst going and dont' initially increase power at the same rate as at ground level. ONCE the turbo is spinning fast enough and producing enough boost for the wastegate to want to blled some off THEN it is at the same power as sea level. So at higher alts they tend to be more laggy and more peaky.
BUT with MODERN ECUs this often re-maps and shifts the wastegate actuator electornically ( as opposed to earluer/cheaper mechanical )

Again if you look at my earlier post a car using a MAP sensor will be more prone to some changes in how it runs. But if the same pressure is in the manifold yes it will have the same A/F ratio. Using a Map sensor makes it tougher since its just measuring Manifold absolute pressure and then also needing input from the IAT. Again thats why so many cars run MAF sensors or both. They can measure Mass airflow. I can tell you 100% my car intakes the same airflow at sea level as it does at the top of the beartooth's. I get exactly the same Mass flow and boost, I can digitally verify this. No changes to the tune or duty cycle of the boost controller. Another thing is how is your dad's car setup? There are many other variable that can effect this but the topic is that for a given amount of air the same fuel will be injected regardless of altitude. If you have less air the car obviously will not run the same, but a hot day, dry day and many other things can cause these differences. The actual elevation will not change the calibration of the tune. Thats like saying if I turn the boost down I need to retune my car. Just because I run less boost doesn't make the timing or A/F values change.

Also we all know that every track is different, you can never compare track times between track with 100% accuracy. Especially comparing a track like ours that is usually got very dry air and lots of dust. Let alone less than perfect track prep. Also what were the temps? I bet the temp and humidity were not the same on both runs. That makes more of a difference than elevation will. I am saying temps staying the same a car will run the same A/F ratio regardless of the elevation. I am not saying your car will feel/run the exact same no matter where you are. That does not mean the A/F ratio has changed. Just that there are other variables effecting performance. I think I am commenting on the original topic "A/F ratio vs. Elevation" not my car runs different when I go to _________.

Why not just rig you're EGR valve open all the time? You'll get even more air into the intake then......

book learnin. not the same as street learnin. well then just fix it automagically.

Matt where are the updates on your car? I'm curious to see what's been done now.

Who has EGR's anymore, well besides all the people trying to slow down global warming. Besides the fact the EGR air is no longer mostly oxygen and now its mostly carbon dioxide. Not oxygen like you would get at the top of the mountains.

I'm not saying I learned this in a book, I have seen it on my cars as well as many others. Talk to anyone that runs a dyno and they will tell you that boosted cars don't get SAE correction because of that. Some dyno programs even have a special correction for boosted cars that only use Temp instead of all the factors that SAE uses. Another reason why I think dyno's should only be used for tuning and not for bragging. Track times say a lot more about what you and your car can really do.

This is one of those topics that can go round and round forever...... I'm done. lol

I'm going to go force induce my car with my high performance EGR yo..... lol

Updates on my car? hmmm.... I guess it has been awhile since I've updated. I've been updating the "matt fiat x-1/9" thread in the garage but not the monster 1.5l build thread I should link them together. I have a handful of pics I can post to show some progress if you want. Just seams like I'm not getting anywhere. lol