Lsd Unique Plenum
1 - 13 of 13 Posts
I'm gonna be in on a cats/plenum package hopefully as soon as he offers it, or as soon as i have the funds (probably the latter).
Joined
·
6 Posts
But...he came back today with proper SAE correctly dyno charts. Check below!!
Here's what he said:
now the sae corrected numbers smoothed to 3
baseline sae 239.1
+ cats 248.1 (+9 rwhp) WHY?
+ plenum 256.7(+8.6)
total gained = 17.6
just about the same.
so what I want to know is this...
why did the sae corrected number RAISE the cat and LOWER the plenum but come out about the SAME?
all_bark has attached this image:
Here's what he said:
now the sae corrected numbers smoothed to 3
baseline sae 239.1
+ cats 248.1 (+9 rwhp) WHY?
+ plenum 256.7(+8.6)
total gained = 17.6
just about the same.
so what I want to know is this...
why did the sae corrected number RAISE the cat and LOWER the plenum but come out about the SAME?
all_bark has attached this image:
Corrected or Uncorrected
Dynojets can read corrected or uncorrected horsepower. Because different weather conditions can result in different air densities and different oxygen concentrations, the weather can have a significant effect on power output. The SAE has a standard set of correction factors that can be used to normalize all power outputs to what they would be at sea level, on a 60 degree day, with 0 percent humidity. Every Dynojet has a small weather station built in to feed the appropriate temperature and barometric pressure readings to the computer so it can calculate this factor. The difference between 0 percent and 100 percent humidity is about a seven percent correction. A temperature change from 60 to 90 degrees, on the other hand, will have an effect of about a 2.8 percent. A difference in elevation from sea level to 5000 feet is worth a whopping 20 percent!
If you use uncorrected data, the changes in power output due to weather conditions could be misconstrued as being a result of something else. For example, if you have a dyno sheet showing that a header made a 15-hp gain, but the runs were done on different days and the plot was made with uncorrected data, you can't be sure if that is really a 15-hp header, or an 8-hp header and a 7-hp weather change.
Corrected numbers, on the other hand, can be suspect in certain cases as well. Turbocharged cars running at high altitude, for example, might be more accurately represented by uncorrected numbers. Say you are testing an FD3S RX-7 in Denver, where the elevation is approximately 5,000 feet. Shiv Pathak, master of our FD3S RX-7 project, reports that he always sees higher boost levels at high altitude. The reason is simple. The wastegate opens when boost is 12 psi higher than the normal sea-level reference air behind the wastegate actuator diaphragm (air that has been stuck in there ever since the diaphragm was sealed somewhere in Hiroshima). As the air density drops at high altitude, the actual pressure in the boosted intake manifold remains constant. The boost gauge, though, reads pounds of boost over ambient pressure. If the ambient air pressure in Hiroshima was 14.5 psi when that diaphragm was sealed, but it is only 13.5 psi when Shiv drives through the mountains, his boost gauge will read 1 psi higher than normal.
The SAE correction factor used by Dynojet assumes that lower air pressure at the sensor box means lower air pressure in the intake manifold, though, so at 5,000 feet the dyno is applying a 20-percent correction factor to compensate for a loss of air density that the engine never sees. This is fine if you are doing all your tests in Denver, but if you do one test in Denver and one test in New Orleans (the highest mountain in New Orleans is 12 feet above sea level) uncorrected numbers will be more accurate.
The SAE correction factors are only accurate over a relatively limited range, and the Dynojet software is smart enough to warn you when two runs with wildly different correction factors are being compared. The software in New Orleans can't check your glovebox for that last dyno printout from Denver, though, so you'll have to warn yourself.
Courtesy of Dave Coleman
Dynojets can read corrected or uncorrected horsepower. Because different weather conditions can result in different air densities and different oxygen concentrations, the weather can have a significant effect on power output. The SAE has a standard set of correction factors that can be used to normalize all power outputs to what they would be at sea level, on a 60 degree day, with 0 percent humidity. Every Dynojet has a small weather station built in to feed the appropriate temperature and barometric pressure readings to the computer so it can calculate this factor. The difference between 0 percent and 100 percent humidity is about a seven percent correction. A temperature change from 60 to 90 degrees, on the other hand, will have an effect of about a 2.8 percent. A difference in elevation from sea level to 5000 feet is worth a whopping 20 percent!
If you use uncorrected data, the changes in power output due to weather conditions could be misconstrued as being a result of something else. For example, if you have a dyno sheet showing that a header made a 15-hp gain, but the runs were done on different days and the plot was made with uncorrected data, you can't be sure if that is really a 15-hp header, or an 8-hp header and a 7-hp weather change.
Corrected numbers, on the other hand, can be suspect in certain cases as well. Turbocharged cars running at high altitude, for example, might be more accurately represented by uncorrected numbers. Say you are testing an FD3S RX-7 in Denver, where the elevation is approximately 5,000 feet. Shiv Pathak, master of our FD3S RX-7 project, reports that he always sees higher boost levels at high altitude. The reason is simple. The wastegate opens when boost is 12 psi higher than the normal sea-level reference air behind the wastegate actuator diaphragm (air that has been stuck in there ever since the diaphragm was sealed somewhere in Hiroshima). As the air density drops at high altitude, the actual pressure in the boosted intake manifold remains constant. The boost gauge, though, reads pounds of boost over ambient pressure. If the ambient air pressure in Hiroshima was 14.5 psi when that diaphragm was sealed, but it is only 13.5 psi when Shiv drives through the mountains, his boost gauge will read 1 psi higher than normal.
The SAE correction factor used by Dynojet assumes that lower air pressure at the sensor box means lower air pressure in the intake manifold, though, so at 5,000 feet the dyno is applying a 20-percent correction factor to compensate for a loss of air density that the engine never sees. This is fine if you are doing all your tests in Denver, but if you do one test in Denver and one test in New Orleans (the highest mountain in New Orleans is 12 feet above sea level) uncorrected numbers will be more accurate.
The SAE correction factors are only accurate over a relatively limited range, and the Dynojet software is smart enough to warn you when two runs with wildly different correction factors are being compared. The software in New Orleans can't check your glovebox for that last dyno printout from Denver, though, so you'll have to warn yourself.
Courtesy of Dave Coleman
1 - 13 of 13 Posts
Join the discussion
Join now to ask and comment!