Dyno Runs / Correction Factors
10-28-2009, 01:09 PM
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Dyno Runs / Correction Factors
Yesterday I dyno'ed my 951 to get a baseline. It has an old Autothority MAF kit with a K27/8 , no cat, 2.5 inch exhaust, and a few other mods that really dont affect power (BOV, wastegate, etc).
I wanted to get a baseline on the car before I install my Vitesse racing MAF system.
The car was dyno'ed in Denver (5000ft altitude) and the correction factor for normal atmosphere was about 1.3 yesterday due to low atmospheric pressure. Turbo correction factors are sort or suspect to me. For example, at 15psig (gauge pressure) boost the total absolute pressure inside the manifold is 11.6 psi (typical Denver absolute pressure) + 15psi or 26.6 total absolute pressure.
Now at sea level that same 15psi boost is 14.7+15 = 29.7 psi of boost inside the manifold. Now, you can crank up boost to make the same absolute pressure (some newer systems may do this automatically) but is it really the same "air". The turbo is working at a different pressure ratio and compressing the air more creates more heat. So anyways, not really sure about what the correct correction factor is. The bottom line is that non-corrected power is what I feel when driving.
On the dyno, they mapped manifld pressure but he forgot to zero the system before the runs and that made the boost on the dyno read 0.8psi low. (the zero was off by that amount after it was disconnected from the car).
Also, this was run on a Dyno Dynamics dyno. Some say they run low, some high. It seemed about right to me uncorrected based upon MPH at the dragstrip and Dynolicous on the iphone.
Here are the dyno runs.
Any predictions what the Vitesse MAF system will do?
I need to first make about 300rwhp (uncorrected) to break 110mph in the 1/4 mile. After that I want to break 115mph which will take about 340rwhp uncorrected. Will have to figure out what i need to make 340rwhp.
Little steps at a time.
-Dana
Corrected.
http://s755.photobucket.com/albums/x...09_2_small.jpg
Uncorrected
http://s755.photobucket.com/albums/x...09_3_small.jpg
And then Corrected / Uncorrected / Boost on the same graph (the uncorrected in the unlabeled trace).
http://s755.photobucket.com/albums/x...09_1_small.jpg
I wanted to get a baseline on the car before I install my Vitesse racing MAF system.
The car was dyno'ed in Denver (5000ft altitude) and the correction factor for normal atmosphere was about 1.3 yesterday due to low atmospheric pressure. Turbo correction factors are sort or suspect to me. For example, at 15psig (gauge pressure) boost the total absolute pressure inside the manifold is 11.6 psi (typical Denver absolute pressure) + 15psi or 26.6 total absolute pressure.
Now at sea level that same 15psi boost is 14.7+15 = 29.7 psi of boost inside the manifold. Now, you can crank up boost to make the same absolute pressure (some newer systems may do this automatically) but is it really the same "air". The turbo is working at a different pressure ratio and compressing the air more creates more heat. So anyways, not really sure about what the correct correction factor is. The bottom line is that non-corrected power is what I feel when driving.
On the dyno, they mapped manifld pressure but he forgot to zero the system before the runs and that made the boost on the dyno read 0.8psi low. (the zero was off by that amount after it was disconnected from the car).
Also, this was run on a Dyno Dynamics dyno. Some say they run low, some high. It seemed about right to me uncorrected based upon MPH at the dragstrip and Dynolicous on the iphone.
Here are the dyno runs.
Any predictions what the Vitesse MAF system will do?
I need to first make about 300rwhp (uncorrected) to break 110mph in the 1/4 mile. After that I want to break 115mph which will take about 340rwhp uncorrected. Will have to figure out what i need to make 340rwhp.
Little steps at a time.
-Dana
Corrected.
http://s755.photobucket.com/albums/x...09_2_small.jpg
Uncorrected
http://s755.photobucket.com/albums/x...09_3_small.jpg
And then Corrected / Uncorrected / Boost on the same graph (the uncorrected in the unlabeled trace).
http://s755.photobucket.com/albums/x...09_1_small.jpg
10-28-2009, 01:18 PM
#2
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Dana, looking at your corrected dyno chart. Am I reading this correctly: 335rwhp at 13psi?
Do you have a K27/6 or K27/8?
Do you have a K27/6 or K27/8?
10-28-2009, 01:25 PM
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Three Wheelin'
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Update.
Here is the video of the run.
http://www.youtube.com/watch?v=U71tTCbHXm4
K27/6. Add about 1psi to the boost numbers because it wasn't zerod correctly.
Also on the dyno dynamics webpage http://www.dyno.com.au/dyno/controll...rt/showFAQPage they say this about boost (but they down allow FAQ downloads so I dont know the answer).
Low Boost
Frequently the maximum boost achieved on the dynamometer is less than the boost achieved on road.
* What causes this?
* What can I do to reduce this effect?
So not sure what to think of this. My boost gauge shows 16psi (autometer gauge).
-Dana
Here is the video of the run.
http://www.youtube.com/watch?v=U71tTCbHXm4
K27/6. Add about 1psi to the boost numbers because it wasn't zerod correctly.
Also on the dyno dynamics webpage http://www.dyno.com.au/dyno/controll...rt/showFAQPage they say this about boost (but they down allow FAQ downloads so I dont know the answer).
Low Boost
Frequently the maximum boost achieved on the dynamometer is less than the boost achieved on road.
* What causes this?
* What can I do to reduce this effect?
So not sure what to think of this. My boost gauge shows 16psi (autometer gauge).
-Dana
10-28-2009, 01:30 PM
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Yes, that is what it showed. But realistically, it is about 255hp uncorrected for altitude. I think that is number that is interesting to me. The car doesn't accelerate based upon corrected hp, only accelerates based upon on uncorrected HP.
That's why i want to make at 300hp uncorrected (and then 340-350). Corrected HP is only to boost ego.
-Dana
10-28-2009, 01:36 PM
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BTW thank John for pestering me about getting the MAF system installed.
It got me to go get the car dyno'ed yesterday. Snowing like crazy today. Gets me closer to getting it installed.
-Dana
It got me to go get the car dyno'ed yesterday. Snowing like crazy today. Gets me closer to getting it installed.
-Dana
10-28-2009, 02:00 PM
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K27/6
Yes, that is what it showed. But realistically, it is about 255hp uncorrected for altitude. I think that is number that is interesting to me. The car doesn't accelerate based upon corrected hp, only accelerates based upon on uncorrected HP.
That's why i want to make at 300hp uncorrected (and then 340-350). Corrected HP is only to boost ego.
-Dana
Yes, that is what it showed. But realistically, it is about 255hp uncorrected for altitude. I think that is number that is interesting to me. The car doesn't accelerate based upon corrected hp, only accelerates based upon on uncorrected HP.
That's why i want to make at 300hp uncorrected (and then 340-350). Corrected HP is only to boost ego.
-Dana
- Something does not look right with the corrected numbers. A K27/6 is not going to make 335rwhp at 13,14 or 15psi boost.
- Boost curve looks odd for K27/6.
- Did you record your AFR?
- Are the dyno charts showing HP at the crank or RWHP?
10-28-2009, 02:01 PM
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10-28-2009, 02:14 PM
#8
Three Wheelin'
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The AFR ratio was all over the place. The dyno didnt record it but they had a stand alone system with a recorder. At idle it was showing (at the tailpipe, no cat) about 15.5:1. The AFR dropped down to 11.5:1 in the middle and then kinda leaned out up top. Just not really stable. I will email and try to get the AFR.
The numbers should be RWHP. But again, i think the correction factor is off. The uncorrected seems about right to me. 255hp. I weighed the car as it was yesterday. 3100lbs. + 170 for me, so 3300lbs. The car runs (uncorrected) MPH in 1/4 mile at 103-104. It should take about 290 crank HP to run those MPH (uncorrected of course). Figuring 15% loss through drivetrain that is about 246rwhp. So very close (as far as predictions go) to the uncorrected RWHP.
Some people at this altitude say to use about a +15% correction factor for a turbo instead of the +20-30% that the weather stations on the dynos typcially try to use. The corrected numbers to me are suspect.
-Dana
The numbers should be RWHP. But again, i think the correction factor is off. The uncorrected seems about right to me. 255hp. I weighed the car as it was yesterday. 3100lbs. + 170 for me, so 3300lbs. The car runs (uncorrected) MPH in 1/4 mile at 103-104. It should take about 290 crank HP to run those MPH (uncorrected of course). Figuring 15% loss through drivetrain that is about 246rwhp. So very close (as far as predictions go) to the uncorrected RWHP.
Some people at this altitude say to use about a +15% correction factor for a turbo instead of the +20-30% that the weather stations on the dynos typcially try to use. The corrected numbers to me are suspect.
-Dana
10-28-2009, 02:59 PM
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abs pressure at 5000 ft ASL ~ 12.2 psia
for a NA motor:
14.7/12.2 ~ 1.20 or 20%
for a turbo (13 psi boost)
14.7 + 13/12.2 + 13 ~ 1.1 or 10%
at least that's how I would do it...
plus additonal for and temp/humid/baro P differences from the std atm
for a NA motor:
14.7/12.2 ~ 1.20 or 20%
for a turbo (13 psi boost)
14.7 + 13/12.2 + 13 ~ 1.1 or 10%
at least that's how I would do it...
plus additonal for and temp/humid/baro P differences from the std atm
10-28-2009, 03:20 PM
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I picked 11.6 because I have hardly ever seen correction under 20% on any dyno. Also, I worked with some very good calibrated industrial equipment that true atmospheric pressure was needed. An average/normal reading I saw was about 800mbar absolute pressure so i just picked that.
Using the method that you used (and 14psi boost for the error that was found) and then 800bar, its about 13%. Still some pressure ratios to take into account for turbo efficiency so looking at the numbers that is where I think most people get the roughly 15% for a typical day up here. I would also guess some of that 15% that many say for turbo correction factor is comparing cars that were run at sea level and this altitude.
But corrected would be with the following:
110% 280.5hp
112% 285.6hp
115% 293.25hp
Still maybe high for a K27/6. But the uncorrected number seems to mesh with drag strip MPH. So maybe it is right? Not sure. But absolute numbers are not so important. I want to see before and after the MAF upgrade so i will just use the same dyno.
-Dana
-Dan a
Using the method that you used (and 14psi boost for the error that was found) and then 800bar, its about 13%. Still some pressure ratios to take into account for turbo efficiency so looking at the numbers that is where I think most people get the roughly 15% for a typical day up here. I would also guess some of that 15% that many say for turbo correction factor is comparing cars that were run at sea level and this altitude.
But corrected would be with the following:
110% 280.5hp
112% 285.6hp
115% 293.25hp
Still maybe high for a K27/6. But the uncorrected number seems to mesh with drag strip MPH. So maybe it is right? Not sure. But absolute numbers are not so important. I want to see before and after the MAF upgrade so i will just use the same dyno.
-Dana
-Dan a
10-28-2009, 03:55 PM
#11
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Myself, I have found dynos to be pretty optimistic. As you are aware, They used a 1.23 correction factor on my first dyno. That produced ~410 hp at 23 psi falling to 17-18 (too small of compressor). However, with that said I ran 107mph with that same compressor on at the time, up here at altitude at full weight. The hotside was quite a bit larger than what you have, so that is probably why it even had any top end at all.
Since, with a larger compressor 57mm it has went almost 117 mph.
What does all this mean to me.... well even though the car may have made 400 hp at one point in the power band it is evident that b/c of the falling boost it did not make that much at the end of the track hence the lower trap speed. Then when I used a larger compressor with the same hotside and held boost to redline it ran a much higher trap. I have also noticed that since I have been trying to use a smaller hotside the same holds true regarding top end power. Using the dyno numbers to get what a trap speed could be, may be only a small indicator. I have found that even though the dyno may say high 400's the trap speeds are closer to just over 400 hp. This is just in my case which had a clutch variable and compounding speed aspect that was missing for the first half of the track.
Another thing I have done, is gauge my "trap speed HP" against my accelerometer program on my Iphone and it was very close (~420 at the time).
I did this also with another listers car that made 400 hp on the dyno and his car actually was pretty correct to the dyno number (rather than trap sped hp). He is using a similiar turbo to you too. It was pretty impressive considering, but may have been due to a better gearing setup and use of a 2 step .
anyway enough rambling.
Since, with a larger compressor 57mm it has went almost 117 mph.
What does all this mean to me.... well even though the car may have made 400 hp at one point in the power band it is evident that b/c of the falling boost it did not make that much at the end of the track hence the lower trap speed. Then when I used a larger compressor with the same hotside and held boost to redline it ran a much higher trap. I have also noticed that since I have been trying to use a smaller hotside the same holds true regarding top end power. Using the dyno numbers to get what a trap speed could be, may be only a small indicator. I have found that even though the dyno may say high 400's the trap speeds are closer to just over 400 hp. This is just in my case which had a clutch variable and compounding speed aspect that was missing for the first half of the track.
Another thing I have done, is gauge my "trap speed HP" against my accelerometer program on my Iphone and it was very close (~420 at the time).
I did this also with another listers car that made 400 hp on the dyno and his car actually was pretty correct to the dyno number (rather than trap sped hp). He is using a similiar turbo to you too. It was pretty impressive considering, but may have been due to a better gearing setup and use of a 2 step .
anyway enough rambling.
10-28-2009, 04:11 PM
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what was the air temp/humid baro P on that day?
obviously temp inside the dyno room or intake air
good cf calc http://wahiduddin.net/calc/calc_hp.htm
std conditions SAE
temp 77 F
humid 0%
atm P 29.235 in hg (990 mbar)
altitude 0 ft ASL (sea level)
as temp goes down, CF goes down, 60F is +2%
as humid goes up, CF goes up, small effect from 0 to 50% is only -2%
as atm P goes up, CF goes down my guess -1%
as alt increase, so does CF
so 2 - 2 - 1 ~ -1% + 10% from above ~9% cf
using the calc
60F/30%/29.000/5000' gives a cf of ~24%, but this does not account for turbocharging, so I guess 1.09 is pretty close
obviously temp inside the dyno room or intake air
good cf calc http://wahiduddin.net/calc/calc_hp.htm
std conditions SAE
temp 77 F
humid 0%
atm P 29.235 in hg (990 mbar)
altitude 0 ft ASL (sea level)
as temp goes down, CF goes down, 60F is +2%
as humid goes up, CF goes up, small effect from 0 to 50% is only -2%
as atm P goes up, CF goes down my guess -1%
as alt increase, so does CF
so 2 - 2 - 1 ~ -1% + 10% from above ~9% cf
using the calc
60F/30%/29.000/5000' gives a cf of ~24%, but this does not account for turbocharging, so I guess 1.09 is pretty close
10-28-2009, 04:52 PM
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Another thing I have done, is gauge my "trap speed HP" against my accelerometer program on my Iphone and it was very close (~420 at the time).
I did this also with another listers car that made 400 hp on the dyno and his car actually was pretty correct to the dyno number (rather than trap sped hp). He is using a similiar turbo to you too. It was pretty impressive considering, but may have been due to a better gearing setup and use of a 2 step ..
I did this also with another listers car that made 400 hp on the dyno and his car actually was pretty correct to the dyno number (rather than trap sped hp). He is using a similiar turbo to you too. It was pretty impressive considering, but may have been due to a better gearing setup and use of a 2 step ..
I had the wrong weight for the car plus me (i used 3000lbs on dynolicous). So the iphone spit out 232hp from a section gear pull. Putting in a little more weight would make it close to what the dyno gave. So in general, I think the uncorrected number is in the ballpark.
Now I just need to drop the car off at your house and get it over 115mph....
-Dana
10-28-2009, 06:54 PM
#14
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Yes dynolicious,
yes it is/was my opinion the program was closer to the corrected number. My car at the time, probably had a lower trap speed due to the clutch considering it wouldn't get going until half track. The program showed 123 mph vs a 117 with a really crappy 1/8 mile.
Bring it on by hehehe .. are you back in town??
yes it is/was my opinion the program was closer to the corrected number. My car at the time, probably had a lower trap speed due to the clutch considering it wouldn't get going until half track. The program showed 123 mph vs a 117 with a really crappy 1/8 mile.
Bring it on by hehehe .. are you back in town??