New dyno data for the altitude correction discussion (295whp SOHC)
02-28-2006, 09:05 AM
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New dyno data for the altitude correction discussion (295whp SOHC)
This thread is in an attempt to continue a great technical discussion from an older post located here: https://honda-tech.com/zerothread?id=1468119
llewsirc has officially moved to Las Vegas, and I was down there last weekend to re-tune his car and try to get some more data on this topic.
First off, changes to the car:
- Gas was changed from 91 octane to 100 octane (it is readily available at the pump in Vegas and llewsirc wanted to get it tuned on what it will now be running regularly). However, the car was properly tuned each time with NepTune.
- At the end of the session, the plugs were changed from NGK 7's to NGK 8's. Upon reading the plugs, the resulting burn looked happier.
The rest was unchanged: same car, same turbo, same exhaust, etc. To my knowledge, the only changes were the fuel and the plugs near the end of the session.
Other changes:
- The CO dyno was a dynojet (I believe it was a 248). The Vegas dyno was a dynojet (I believe a 224). I used the same gear for tuning on both dynos, so I believe the slower spool time can be attributed to the fact that the car had to accelerate a less massive roller.
The *peak* absolute boost pressure was dialed in to be the same. In reality, the CO absolute boost was reached and then held constant, while the vegas absolute boost peaked at the same point, but it reached 1 or 2 psi less and then crept up to the same peak absolute boost point. The absolute manifold pressures were the same from peak whp to redline.
The car's previous dyno (sorry guys, I can't find a scanned version of the uncorrected printouts, but the CF was 1.16, so divide the entire curve by 1.16, which yields a peak whp of 293):
The new graph (uncorrected first for you tony
:
The car made 2 more whp peak. Unfortunately I couldn't get the guys at the new dyno to keep the hp and torque axis the same on the new graph, but you can still follow along the curves. (To get the uncorrected #'s from the CO graph, simply find the value at any point and divide by 1.16.)
In an attempt to begin analyzing the curves, I'm disappointed that I could not use the same model dynojet (with the same size rollers) to do the comparison. You can see that peak torque was shifted from around 5350 to 5650. This number was also lower (from around 262ftlb to 244ftlb). I attribute this to the smaller size of the roller and the fact that the sme absolute boost pressure was not reached at the same RPM. Since the dynojet maesures horsepower based on the acceleration of a constant mass wheel, and the wheel was less massive on the new dyno chart, the car took longer to build full boost (around 300rpms later on the Vegas dyno). (Its the same reason that you commonly reach full boost at a later rpm in a lower gear. This is clearly one of the downsides of using a non-load bearing dyno to attempt to tune a vehicle.) The car had not reached full boost at the rpm where peak torque (best VE, i.e. where the motor previously breathed the best) was previously achieved. I would performed a test using a higher gear, but that would skew the data because I wanted to do the comparison using the same gears i.e. closest possible conditions.
However, we also see a similar hump in the torque curve around 6400 on both curves. Notice that this is the point where *peak WHP* was achieved on both charts. The CO chart yields 235ftlb at that point, while the Vegas chart yields 240ftlb). You can see that between peak torque and the torque "hump" at 6400, the Vegas graph drops significantly less then the CO graph. I believe that this further substantiates my theory that the peak torque was lower and later simply due to the car accelerating a less massive wheel generating a later peak boost pressure.
If we look at 7400 on both graphs (approx. redline), the CO graph yields around 175ftlb while Vegas graph also yields around 175ftlb.
So, assuming the 2 dynos are generating similar numbers (which I know it not always a safe assumption), the car made 2 more peak uncorrected whp. Analysis of the torque corves shows us that the 2 dynos generated nearly identical numbers (aside from the fact that the peak boost was not reached until later in Vegas due to the less massive roller). The elevation went from ~6000 feet to ~2000 feet... However, the biggest difference between the dyno days was with the intake air temps.
On the dyno day in CO, we had extremely cold IAT's. I was literally logging 40*-50* IATs that day (it was really really cold). On the dyno day in vegas, I was logging 100* IAT's. This will have a significant impact in the final power that is output. In EFI101, Ben Strater teaches that for every 10* C increase in temps, you lose ~3.5% power. Now, I know this is an estimation and I'm sure that it doesn't hold true 100% for every setup at every altitude in every possible condition, but it gives us a starting point for an estimate.
Using that for an estimate: (37.7* C - 10.0* C = 27.7* C change). So, 3.5% * 2.77 (for temp adjustment) = 9.70% power loss from going ftom 50*F to 100*F IAT's. So ASSuming that this temp correction is correct across the powerband, 295whp * 1.097 = 324whp.
Would the car have made 329whp if the car was in Vegas at 40* IAT's? We can't say for sure unless we put the car under the same conditions, which probably won't happen in Vegas
. However, we have tried to hold as much constant as possible between the tunes to give the best possible honest, unbiased data that we could get.
So, to sum it up:
- Did the change in altitude allow the car to yield higher power? Slightly, however the torque curves generated were nearly identical (except for the later spool times due to the less massive roller in Vegas).
- Did it make 340whp, NO.
- Would it have made more if the IAT's were the same? Yes. How much more? We can't say for sure, but a decend educated guess yields 324whp.
- is 324WHP >= 340WHP? No, so the CO dyno correction definitely overinflated the readouts in CO.
- Are we claiming that is made 324WHP? NO. That's just a decent educated guess for argument's sake.
So in conclusion, altitude does hurt us FI guys too, and dyno correction algorithms do overinflate the numbers at high altitudes, BUT not as much as the recent bandwagon would dictate. The car made slightly more peak power with 50*-60* hotter air at a lower altitude.
PS, for anyone interested in seeing the corrected #'s in Vegas, CF of 5%:
Also, after finishing the test for this thread to my satisfaction, we tried to turn up the boost to see if she would make more power. The reuslt was 20 less whp. This car is really choking up top with the log manifold, 2.5" DP and .48 ar hotside. We will retune this car in the near future with some significant changes in the exhaust area
llewsirc has officially moved to Las Vegas, and I was down there last weekend to re-tune his car and try to get some more data on this topic.
First off, changes to the car:
- Gas was changed from 91 octane to 100 octane (it is readily available at the pump in Vegas and llewsirc wanted to get it tuned on what it will now be running regularly). However, the car was properly tuned each time with NepTune.
- At the end of the session, the plugs were changed from NGK 7's to NGK 8's. Upon reading the plugs, the resulting burn looked happier.
The rest was unchanged: same car, same turbo, same exhaust, etc. To my knowledge, the only changes were the fuel and the plugs near the end of the session.
Other changes:
- The CO dyno was a dynojet (I believe it was a 248). The Vegas dyno was a dynojet (I believe a 224). I used the same gear for tuning on both dynos, so I believe the slower spool time can be attributed to the fact that the car had to accelerate a less massive roller.
The *peak* absolute boost pressure was dialed in to be the same. In reality, the CO absolute boost was reached and then held constant, while the vegas absolute boost peaked at the same point, but it reached 1 or 2 psi less and then crept up to the same peak absolute boost point. The absolute manifold pressures were the same from peak whp to redline.
The car's previous dyno (sorry guys, I can't find a scanned version of the uncorrected printouts, but the CF was 1.16, so divide the entire curve by 1.16, which yields a peak whp of 293):
The new graph (uncorrected first for you tony
:The car made 2 more whp peak. Unfortunately I couldn't get the guys at the new dyno to keep the hp and torque axis the same on the new graph, but you can still follow along the curves. (To get the uncorrected #'s from the CO graph, simply find the value at any point and divide by 1.16.)
In an attempt to begin analyzing the curves, I'm disappointed that I could not use the same model dynojet (with the same size rollers) to do the comparison. You can see that peak torque was shifted from around 5350 to 5650. This number was also lower (from around 262ftlb to 244ftlb). I attribute this to the smaller size of the roller and the fact that the sme absolute boost pressure was not reached at the same RPM. Since the dynojet maesures horsepower based on the acceleration of a constant mass wheel, and the wheel was less massive on the new dyno chart, the car took longer to build full boost (around 300rpms later on the Vegas dyno). (Its the same reason that you commonly reach full boost at a later rpm in a lower gear. This is clearly one of the downsides of using a non-load bearing dyno to attempt to tune a vehicle.) The car had not reached full boost at the rpm where peak torque (best VE, i.e. where the motor previously breathed the best) was previously achieved. I would performed a test using a higher gear, but that would skew the data because I wanted to do the comparison using the same gears i.e. closest possible conditions.
However, we also see a similar hump in the torque curve around 6400 on both curves. Notice that this is the point where *peak WHP* was achieved on both charts. The CO chart yields 235ftlb at that point, while the Vegas chart yields 240ftlb). You can see that between peak torque and the torque "hump" at 6400, the Vegas graph drops significantly less then the CO graph. I believe that this further substantiates my theory that the peak torque was lower and later simply due to the car accelerating a less massive wheel generating a later peak boost pressure.
If we look at 7400 on both graphs (approx. redline), the CO graph yields around 175ftlb while Vegas graph also yields around 175ftlb.
So, assuming the 2 dynos are generating similar numbers (which I know it not always a safe assumption), the car made 2 more peak uncorrected whp. Analysis of the torque corves shows us that the 2 dynos generated nearly identical numbers (aside from the fact that the peak boost was not reached until later in Vegas due to the less massive roller). The elevation went from ~6000 feet to ~2000 feet... However, the biggest difference between the dyno days was with the intake air temps.
On the dyno day in CO, we had extremely cold IAT's. I was literally logging 40*-50* IATs that day (it was really really cold). On the dyno day in vegas, I was logging 100* IAT's. This will have a significant impact in the final power that is output. In EFI101, Ben Strater teaches that for every 10* C increase in temps, you lose ~3.5% power. Now, I know this is an estimation and I'm sure that it doesn't hold true 100% for every setup at every altitude in every possible condition, but it gives us a starting point for an estimate.
Using that for an estimate: (37.7* C - 10.0* C = 27.7* C change). So, 3.5% * 2.77 (for temp adjustment) = 9.70% power loss from going ftom 50*F to 100*F IAT's. So ASSuming that this temp correction is correct across the powerband, 295whp * 1.097 = 324whp.
Would the car have made 329whp if the car was in Vegas at 40* IAT's? We can't say for sure unless we put the car under the same conditions, which probably won't happen in Vegas
. However, we have tried to hold as much constant as possible between the tunes to give the best possible honest, unbiased data that we could get.So, to sum it up:
- Did the change in altitude allow the car to yield higher power? Slightly, however the torque curves generated were nearly identical (except for the later spool times due to the less massive roller in Vegas).
- Did it make 340whp, NO.
- Would it have made more if the IAT's were the same? Yes. How much more? We can't say for sure, but a decend educated guess yields 324whp.
- is 324WHP >= 340WHP? No, so the CO dyno correction definitely overinflated the readouts in CO.
- Are we claiming that is made 324WHP? NO. That's just a decent educated guess for argument's sake.
So in conclusion, altitude does hurt us FI guys too, and dyno correction algorithms do overinflate the numbers at high altitudes, BUT not as much as the recent bandwagon would dictate. The car made slightly more peak power with 50*-60* hotter air at a lower altitude.
PS, for anyone interested in seeing the corrected #'s in Vegas, CF of 5%:
Also, after finishing the test for this thread to my satisfaction, we tried to turn up the boost to see if she would make more power. The reuslt was 20 less whp. This car is really choking up top with the log manifold, 2.5" DP and .48 ar hotside. We will retune this car in the near future with some significant changes in the exhaust area
02-28-2006, 09:28 AM
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HUGE THANKS to servion for the tune.
glad we had a chance to get some testing done.
i wish we could have done testing with alittle more constant variables (ie same dyno, and temps) but this will atleast give some people a place to start some discussion.
i will try to find the CO uncorrected numbers, but i dont know if i have them.
the car will be getting a equal length manifold, .63 turbine, 3in DP and possibly a cam in the next month or so.
then we can compare a "street" setup to more of a "mild race" setup
thanks to 1320 Motorsports here in Las Vegas for the use of thier dyno.
Thanks to Jeremy for comin out to tune (not like ti is hard to convince anyone to fly to vegas for the weekend )
thanks for everyone here on honda-tech that have helped answer my questions.
Las Vegas's Fastest / Quickest SOHC Honda in the making
glad we had a chance to get some testing done.
i wish we could have done testing with alittle more constant variables (ie same dyno, and temps) but this will atleast give some people a place to start some discussion.
i will try to find the CO uncorrected numbers, but i dont know if i have them.
the car will be getting a equal length manifold, .63 turbine, 3in DP and possibly a cam in the next month or so.
then we can compare a "street" setup to more of a "mild race" setup
thanks to 1320 Motorsports here in Las Vegas for the use of thier dyno.
Thanks to Jeremy for comin out to tune (not like ti is hard to convince anyone to fly to vegas for the weekend
)thanks for everyone here on honda-tech that have helped answer my questions.
Las Vegas's Fastest / Quickest SOHC Honda in the making
02-28-2006, 10:19 AM
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Re: New dyno data for the altitude correction discussion (servion)
i dont really have much time to go through the post in detail.
its going to be very difficult to have a perfect scenerio.
but, if you were really trying to figure out the difference its pretty simple.
ok you got ur co dyno chart that reads 339 whp corrected.
then you get 309 whp corrected in vegas.
thats an error of 8.8% if the car was dyno'd with the similar parameters.
the correction factor is suppose to take in account multiple things such as baro pressure, temp, elevation, humidity etc.
yes the pulls in co was colder, but the elevation is lower on the lv chart.
uncorrected they are doing about the same. you make up for the elevation but lose due to it being hotter.
the fact of the matter is that they are doing roughly the same numbers regardless of it being in LV or CO.
8.8% is going to be huge on a high hp plot.
its going to be very difficult to have a perfect scenerio.
but, if you were really trying to figure out the difference its pretty simple.
ok you got ur co dyno chart that reads 339 whp corrected.
then you get 309 whp corrected in vegas.
thats an error of 8.8% if the car was dyno'd with the similar parameters.
the correction factor is suppose to take in account multiple things such as baro pressure, temp, elevation, humidity etc.
yes the pulls in co was colder, but the elevation is lower on the lv chart.
uncorrected they are doing about the same. you make up for the elevation but lose due to it being hotter.
the fact of the matter is that they are doing roughly the same numbers regardless of it being in LV or CO.
8.8% is going to be huge on a high hp plot.
02-28-2006, 10:23 AM
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Just out of curiousity...I know last time the guage read 25psi while the map sensor read 20psi. Was it still reading this way in vegas? Or were they right on par with each other?
I see its still majorly choking up top from exhuast restrictions. What cam are you running llewsirc?
Also, servion, couldn't the 12-13whp (I believe he made 283 uncorrected) just be attributed to the 9 point raise in octane. I mean, you did retune the car on 100 octane right? Same absolute boost though, right?
I see its still majorly choking up top from exhuast restrictions. What cam are you running llewsirc?
Also, servion, couldn't the 12-13whp (I believe he made 283 uncorrected) just be attributed to the 9 point raise in octane. I mean, you did retune the car on 100 octane right? Same absolute boost though, right?
02-28-2006, 10:25 AM
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Re: (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">Just out of curiousity...I know last time the guage read 25psi while the map sensor read 20psi. Was it still reading this way in vegas? Or were they right on par with each other?
I see its still majorly choking up top from exhuast restrictions. What cam are you running llewsirc?</TD></TR></TABLE>
The boost gauge was less than 25... I'm not exactly sure what it was reading because I was tuning off of the datalogs, but it was definitely not 25 on the gauge. He's running a stock cam (z6 I believe)
I see its still majorly choking up top from exhuast restrictions. What cam are you running llewsirc?</TD></TR></TABLE>
The boost gauge was less than 25... I'm not exactly sure what it was reading because I was tuning off of the datalogs, but it was definitely not 25 on the gauge. He's running a stock cam (z6 I believe)
02-28-2006, 10:29 AM
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Re: New dyno data for the altitude correction discussion (Mase)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">...
the fact of the matter is that they are doing roughly the same numbers regardless of it being in LV or CO.
8.8% is going to be huge on a high hp plot.
</TD></TR></TABLE>
Absolutely! I find that a lot of people are under the impression that altitude doesn't affect FI cars at all, which is simply not the case. High altitude hurts both fi and n/a. The goal of this test was not an attempt to try and see now much a dyno correction factor is off (because that will always change from setup to setup), but to try and see how much this car was affected directly by the altitude
the fact of the matter is that they are doing roughly the same numbers regardless of it being in LV or CO.
8.8% is going to be huge on a high hp plot.
</TD></TR></TABLE>
Absolutely! I find that a lot of people are under the impression that altitude doesn't affect FI cars at all, which is simply not the case. High altitude hurts both fi and n/a. The goal of this test was not an attempt to try and see now much a dyno correction factor is off (because that will always change from setup to setup), but to try and see how much this car was affected directly by the altitude
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02-28-2006, 10:31 AM
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Re: (llewsirc)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by llewsirc »</TD></TR><TR><TD CLASS="quote">guage boost was ~25 psi
absolute boost (as seen by netpune was ~20psi) Neutral</TD></TR></TABLE>
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?
absolute boost (as seen by netpune was ~20psi) Neutral</TD></TR></TABLE>
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?
02-28-2006, 10:39 AM
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Re: (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?</TD></TR></TABLE>
I'm not sure what "IDK" means, but yes the peak pressure read at the MAP was the same between CO and Vegas FYI, he also posted a video of his gauges on the dyno from the CO tune, but that vid was a pull on more boost (which resulted in less power by the way, much like the same situation in Vegas).
EDIT: Now that I read your first quesiton again, I think I misunderstood you. Yes, in CO the gauge was at 25psi. In vegas, the gauge was more than 20psi, but less than 25psi... I'd have to say around 22psi. But in both cases, the absolute boost was the same
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?</TD></TR></TABLE>
I'm not sure what "IDK" means, but yes the peak pressure read at the MAP was the same between CO and Vegas
FYI, he also posted a video of his gauges on the dyno from the CO tune, but that vid was a pull on more boost (which resulted in less power by the way, much like the same situation in Vegas).EDIT: Now that I read your first quesiton again, I think I misunderstood you. Yes, in CO the gauge was at 25psi. In vegas, the gauge was more than 20psi, but less than 25psi... I'd have to say around 22psi. But in both cases, the absolute boost was the same
02-28-2006, 11:03 AM
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Re: (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">"IDK" - I don't know.
I'm not sure what relevancy my question had, but I think its a direct reflection of compressor efficiency at elevation.</TD></TR></TABLE>
You're right in the sense that the lower altitude yields a lower pressure ratio (ther vertical axis on a compressor map) for the same absolute boost pressure. I.E., the turbo has to provide less boost over atmospheric pressure to get to the same absolute boost pressure.
I'm not sure what relevancy my question had, but I think its a direct reflection of compressor efficiency at elevation.</TD></TR></TABLE>
You're right in the sense that the lower altitude yields a lower pressure ratio (ther vertical axis on a compressor map) for the same absolute boost pressure. I.E., the turbo has to provide less boost over atmospheric pressure to get to the same absolute boost pressure.
02-28-2006, 11:19 AM
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Re: New dyno data for the altitude correction discussion (servion)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by servion »</TD></TR><TR><TD CLASS="quote">
Absolutely! I find that a lot of people are under the impression that altitude doesn't affect FI cars at all, which is simply not the case. High altitude hurts both fi and n/a. The goal of this test was not an attempt to try and see now much a dyno correction factor is off (because that will always change from setup to setup), but to try and see how much this car was affected directly by the altitude </TD></TR></TABLE>
its not so much the altitude, rather i would say its directly proportional to the air density. density altitude is simply one way to express the air density.
Since density is weight divided by volume, you gotta consider the weight of each of the molecules in the air.
Absolutely! I find that a lot of people are under the impression that altitude doesn't affect FI cars at all, which is simply not the case. High altitude hurts both fi and n/a. The goal of this test was not an attempt to try and see now much a dyno correction factor is off (because that will always change from setup to setup), but to try and see how much this car was affected directly by the altitude
</TD></TR></TABLE>its not so much the altitude, rather i would say its directly proportional to the air density. density altitude is simply one way to express the air density.
Since density is weight divided by volume, you gotta consider the weight of each of the molecules in the air.
02-28-2006, 12:35 PM
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Re: (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?</TD></TR></TABLE>
the dyno it the above thread is from CO.
in CO i was seeing 25 psi guage (actually 24.8 on my greddy profec) / 20absolute
in LV im seeing 22 psi guage (actually 21.8 on my greddy profec) / 20 absolute
i am running a stock head and stock cam.
http://www.turbod16.com/viewto...art=0
IDK, thats just what he said. But either way, same absolute boost right?</TD></TR></TABLE>
the dyno it the above thread is from CO.
in CO i was seeing 25 psi guage (actually 24.8 on my greddy profec) / 20absolute
in LV im seeing 22 psi guage (actually 21.8 on my greddy profec) / 20 absolute
i am running a stock head and stock cam.
02-28-2006, 12:37 PM
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Re: (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">"IDK" - I don't know.
I'm not sure what relevancy my question had, but I think its a direct reflection of compressor efficiency at elevation.</TD></TR></TABLE>
proves that in CO a turbo has to work harder (25 guage instead of 22 guage) to make the same 20 psi of absolute boost.
I'm not sure what relevancy my question had, but I think its a direct reflection of compressor efficiency at elevation.</TD></TR></TABLE>
proves that in CO a turbo has to work harder (25 guage instead of 22 guage) to make the same 20 psi of absolute boost.
02-28-2006, 01:03 PM
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Re: (llewsirc)
I didn't read the whole thing through, just a couple quick questions. The SAE numbers in CO will add power based on altitude and take away power based on air temp that day. The SAE in Vegas will not do much for altitude (i think, i don't know what the elevation is there), but will add power for air temp. There are a few different factors contradicting each other in this situation and they really cloud the results to a point where not much can be determined. I don't have alot of time to read over all of what was originally posted, so if i'm missing something, forgive me and give me the short version of it and i'll get back to this later...
02-28-2006, 01:24 PM
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Re: (tony1)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 »</TD></TR><TR><TD CLASS="quote">I didn't read the whole thing through, just a couple quick questions. The SAE numbers in CO will add power based on altitude and take away power based on air temp that day. The SAE in Vegas will not do much for altitude (i think, i don't know what the elevation is there), but will add power for air temp. There are a few different factors contradicting each other in this situation and they really cloud the results to a point where not much can be determined. I don't have alot of time to read over all of what was originally posted, so if i'm missing something, forgive me and give me the short version of it and i'll get back to this later...</TD></TR></TABLE>
Tony, I am not trying to generate a number of how far off a correction factor is between the 2 elevation dyno results: I'm trying to provide as much data as possible to try and get an idea of how much altitude affects power for a typical FI engine (or at least this one). I don't think it would be reasonable to try and "re-correct" a dynojets correction factor for many reasons (most of which we covered in the previous thread). So, I posted the uncorrected Vegas #'s, and I would have re-posted the uncorrected CO dyno #'s, but I don't have a scanned version of them so I posted the corrected ones along with the CF. The CO CF was 1.16 and the LV CF was 1.05, but they really don't matter too much in reagrds to this discussion; the point is that we dynoed a car in 2 different elevations while trying to hold constant as many variables as possible to see how much the altitiude (and other conditions that go with it, i.e. density altitude, etc.) affected the power output.
So basically, we have dyno #'s from the same car at different altitudes with different recorded IAT's. I tried to speculate as to the uncorrected output in LV with Ben Strader's IAT correction figures. Tony, if you get a chance to read the whole initial post, I would like to see your thoughts on the matter
Tony, I am not trying to generate a number of how far off a correction factor is between the 2 elevation dyno results: I'm trying to provide as much data as possible to try and get an idea of how much altitude affects power for a typical FI engine (or at least this one). I don't think it would be reasonable to try and "re-correct" a dynojets correction factor for many reasons (most of which we covered in the previous thread). So, I posted the uncorrected Vegas #'s, and I would have re-posted the uncorrected CO dyno #'s, but I don't have a scanned version of them so I posted the corrected ones along with the CF. The CO CF was 1.16 and the LV CF was 1.05, but they really don't matter too much in reagrds to this discussion; the point is that we dynoed a car in 2 different elevations while trying to hold constant as many variables as possible to see how much the altitiude (and other conditions that go with it, i.e. density altitude, etc.) affected the power output.
So basically, we have dyno #'s from the same car at different altitudes with different recorded IAT's. I tried to speculate as to the uncorrected output in LV with Ben Strader's IAT correction figures. Tony, if you get a chance to read the whole initial post, I would like to see your thoughts on the matter
02-28-2006, 02:04 PM
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Re: (servion)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by servion »</TD></TR><TR><TD CLASS="quote"> Tony, if you get a chance to read the whole initial post, I would like to see your thoughts on the matter </TD></TR></TABLE>
me too
as well as other tuners.
me and jeremy talked about this, and he does a good job of dumbing it down for me.
im looking forward to a good discussion
</TD></TR></TABLE>me too
as well as other tuners.
me and jeremy talked about this, and he does a good job of dumbing it down for me.
im looking forward to a good discussion
02-28-2006, 06:27 PM
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Re: (Bryson)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bryson »</TD></TR><TR><TD CLASS="quote">Hrmm interesting. do you know the altitude of the area?
At any rate, this very good information to have! Good work jeromy..</TD></TR></TABLE>
the dyno facility is on the back side of the LV airport,
according to this site: http://www.airnav.com/airport/KLAS
the elevation is 2181 ft. i would say the dyno was within 50ft of that.
Vtaaak y0 -- still on a 2.5 DP. we wanted to keep as much of the variables the same.
i have a all the parts for a 3in DP in the mail (as well as my 3 in exhaust )
At any rate, this very good information to have! Good work jeromy..
</TD></TR></TABLE>the dyno facility is on the back side of the LV airport,
according to this site: http://www.airnav.com/airport/KLAS
the elevation is 2181 ft. i would say the dyno was within 50ft of that.
Vtaaak y0 -- still on a 2.5 DP. we wanted to keep as much of the variables the same.
i have a all the parts for a 3in DP in the mail (as well as my 3 in exhaust
)
02-28-2006, 11:07 PM
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theres too many factors...
I didnt read everything with a fine tooth comb, so dont criticize if I miss something. But all we are trying to figure out is if the turbo compensates for the lack of density. You have two different altitudes at two different temps, which both effect density. Your guessing and estimating a lot and your results are pretty close to each other.
The proper way would be to measure the actual density of the air at dyno day. This would take out two variables that wouldn't have to be estimated by ben strater (altitude and temperature)
I'm still in the boat of altitude doesnt effect FI cars. We all know that it has to effect it somewhat. The turbo is obviously going to have to spin faster. We don't know if its actually working more (less exhaust back pressure)... But theres really not going to be comparison to an NA car where the only induction it gets is atmospheric pressure.
I dont see a dyno solving the mystery, more like a physics professor.
The turbo did provide the same amount of boost though...and the same amount of boost means the same amount of air (in the same engine)
I didnt read everything with a fine tooth comb, so dont criticize if I miss something. But all we are trying to figure out is if the turbo compensates for the lack of density. You have two different altitudes at two different temps, which both effect density. Your guessing and estimating a lot and your results are pretty close to each other.
The proper way would be to measure the actual density of the air at dyno day. This would take out two variables that wouldn't have to be estimated by ben strater (altitude and temperature)
I'm still in the boat of altitude doesnt effect FI cars. We all know that it has to effect it somewhat. The turbo is obviously going to have to spin faster. We don't know if its actually working more (less exhaust back pressure)... But theres really not going to be comparison to an NA car where the only induction it gets is atmospheric pressure.
I dont see a dyno solving the mystery, more like a physics professor.
The turbo did provide the same amount of boost though...and the same amount of boost means the same amount of air (in the same engine)
03-01-2006, 07:14 AM
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Re: (DaZman69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 »</TD></TR><TR><TD CLASS="quote">
I didnt read everything</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 »</TD></TR><TR><TD CLASS="quote">I didn't read the whole thing through</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">i dont really have much time to go through the post in detail</TD></TR></TABLE>
id like to hear comments after everyone has actually read the entire post
I didnt read everything</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 »</TD></TR><TR><TD CLASS="quote">I didn't read the whole thing through</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">i dont really have much time to go through the post in detail</TD></TR></TABLE>
id like to hear comments after everyone has actually read the entire post
03-01-2006, 07:49 AM
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Re: (DaZman69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 »</TD></TR><TR><TD CLASS="quote">theres too many factors...
I didnt read everything with a fine tooth comb, so dont criticize if I miss something. But all we are trying to figure out is if the turbo compensates for the lack of density. You have two different altitudes at two different temps, which both effect density. Your guessing and estimating a lot and your results are pretty close to each other.
The proper way would be to measure the actual density of the air at dyno day. This would take out two variables that wouldn't have to be estimated by ben strater (altitude and temperature)
I'm still in the boat of altitude doesnt effect FI cars. We all know that it has to effect it somewhat. The turbo is obviously going to have to spin faster. We don't know if its actually working more (less exhaust back pressure)... But theres really not going to be comparison to an NA car where the only induction it gets is atmospheric pressure.
I dont see a dyno solving the mystery, more like a physics professor.
The turbo did provide the same amount of boost though...and the same amount of boost means the same amount of air (in the same engine) </TD></TR></TABLE>
I agree there are more variables than I would have liked, but we held as many constant as possible. Its not very often that I get a chance to tune the same car at multiple altitudes so I thought I would hold as much constant as possible and retune.
The point was that (*assuming the 2 dynojets used output similar results*) the same car made more power with hotter IATs at the same boost simply by going to a lower altitude. At least that right there means something.
I didnt read everything with a fine tooth comb, so dont criticize if I miss something. But all we are trying to figure out is if the turbo compensates for the lack of density. You have two different altitudes at two different temps, which both effect density. Your guessing and estimating a lot and your results are pretty close to each other.
The proper way would be to measure the actual density of the air at dyno day. This would take out two variables that wouldn't have to be estimated by ben strater (altitude and temperature)
I'm still in the boat of altitude doesnt effect FI cars. We all know that it has to effect it somewhat. The turbo is obviously going to have to spin faster. We don't know if its actually working more (less exhaust back pressure)... But theres really not going to be comparison to an NA car where the only induction it gets is atmospheric pressure.
I dont see a dyno solving the mystery, more like a physics professor.
The turbo did provide the same amount of boost though...and the same amount of boost means the same amount of air (in the same engine) </TD></TR></TABLE>
I agree there are more variables than I would have liked, but we held as many constant as possible. Its not very often that I get a chance to tune the same car at multiple altitudes so I thought I would hold as much constant as possible and retune.
The point was that (*assuming the 2 dynojets used output similar results*) the same car made more power with hotter IATs at the same boost simply by going to a lower altitude. At least that right there means something.
03-01-2006, 08:16 AM
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Re: (llewsirc)
Good post. I really dont care about the whole correction factor BS anymore so I have dont an opinion about it. I do care about how my car reacts to different elevations and from my data with timeslips and dataloges here is some info I would like to share. From my experience, efficient turbo cars are not phased in performance from alltitude, my car runs the same #'s everywhere I go, I know the turbo works harder at higher elevation because of the extra shaft speed needed to get the boost level where you had it at the lower elevation and can decrease VE because of an increase of exhaust backpressure.
Here are my #'s on the mountain
Cortney Green ('95 Civic) 10.083 148.28
Cortney Green ('95 Civic) 9.951 145.80
Cortney Green ('95 Civic) 10.052 148.10
Here is Vegas
Cortney Green '95Honda 9.916 147.29
Pomona
Cortney Green '95Honda 9.896 144.69
Cortney Green ('95Honda) 9.891 145.30
Cortney Green ('95Honda) 9.957 145.31
Cortney Green ('95Honda) 9.969 144.03
Cortney Green ('95Honda) 9.916 144.69
Pomona Numbers are a little tainted because of a new untuned turbocharger but if you look at the MPH #'s at vegas and colorado you can see that the car makes close to the same HP at both tracks with the higher mph being at the higher elevtion.
That is all I have but those are REAL #'s with huge differences in atmospheric conditions and not a huge change in performance.
Here are my #'s on the mountain
Cortney Green ('95 Civic) 10.083 148.28
Cortney Green ('95 Civic) 9.951 145.80
Cortney Green ('95 Civic) 10.052 148.10
Here is Vegas
Cortney Green '95Honda 9.916 147.29
Pomona
Cortney Green '95Honda 9.896 144.69
Cortney Green ('95Honda) 9.891 145.30
Cortney Green ('95Honda) 9.957 145.31
Cortney Green ('95Honda) 9.969 144.03
Cortney Green ('95Honda) 9.916 144.69
Pomona Numbers are a little tainted because of a new untuned turbocharger but if you look at the MPH #'s at vegas and colorado you can see that the car makes close to the same HP at both tracks with the higher mph being at the higher elevtion.
That is all I have but those are REAL #'s with huge differences in atmospheric conditions and not a huge change in performance.