SAE dyno correction factors and the LS1
SAE dyno correction factors and the LS1 Hey all...
I recall that over the years, my cars have behaved differently in the cold or in tyhe very hot. Some cars are far more down on power in the hot, and animals in the cold. Others seem good in either climate, adn seem less effected.
The SAE correction is obviously based on the amount of oxygen available for cumbustion in a given volume of air if you have the temerature, humidity, and barometric pressure.
Is it possible that the LS1 motor is just better at accessing oxygen and creating its own density than previous engines? Is it possible that the SAE correction factor is not totally accurate for our engines?
Back in Texas, I recall alot of the dyno folks mentioning that while LT1s dyno'd much worse in the heat, LS1s couldnt seem to care less. Yet the SAE correction factors treat them as the same.
We get a nice big waft of dry cold air through the US, and all of a sudden several vendors start showing off some incredible numbers. Without the benefit of any kind of obvious paradigm shift or revolutionary technology.
hrmmmm......
Thoughts?
\chris
I recall that over the years, my cars have behaved differently in the cold or in tyhe very hot. Some cars are far more down on power in the hot, and animals in the cold. Others seem good in either climate, adn seem less effected.
The SAE correction is obviously based on the amount of oxygen available for cumbustion in a given volume of air if you have the temerature, humidity, and barometric pressure.
Is it possible that the LS1 motor is just better at accessing oxygen and creating its own density than previous engines? Is it possible that the SAE correction factor is not totally accurate for our engines?
Back in Texas, I recall alot of the dyno folks mentioning that while LT1s dyno'd much worse in the heat, LS1s couldnt seem to care less. Yet the SAE correction factors treat them as the same.
We get a nice big waft of dry cold air through the US, and all of a sudden several vendors start showing off some incredible numbers. Without the benefit of any kind of obvious paradigm shift or revolutionary technology.
hrmmmm......
Thoughts?
\chris
Re: SAE dyno correction factors and the LS1 I've heard (from a reputable dyno operator) that when they dyno the same car in conditions where the correction factor is > 1 (bad air) vs where the correction factor is < 1 (good air), that the SAE numbers come out significantly higher when the correction factor is < 1. This is for the same dyno, same car, with the only difference being the weather and correction factor. If nothing else it points out that dynos are only a tuning tool. <img src="gr_images/icons/wink.gif" border="0"> Nevertheless, posting the SAE figures along with the correction factor is still the most accurate way to compare engine setups online.
TECH Apprentice
Joined: Jan 2002
Posts: 356
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From: Texas
Re: SAE dyno correction factors and the LS1 I think the comments about the LS1 not reacting to the heat are heavily based in the composite manifold vs the LT1's aluminum manifold. As the temperature of the engine increases, the LT1 gets a severe heat soak issue. The LS1 seems to be able to "hot lap" with nearly identicle times. I know many of my LT1 friends still lug the cooler to the track to ice the manifold between runs.
As far as correction factors are concerned, I think this debate will continue on for years. Some people are happy with dyno results corrected to SAE standards and others are track performance oriented.
Todd
As far as correction factors are concerned, I think this debate will continue on for years. Some people are happy with dyno results corrected to SAE standards and others are track performance oriented.
Todd
Re: SAE dyno correction factors and the LS1 I feel that the lag in power for the LT1's on the dyno when it's hot out stems from not just the aluminum intake but also the cast-iron block. FWIW, our average correction factor during the summer when I still lived in Lubbock, TX was around 1.13. In the summer of 2000, I dynoed 394 RWHP w/ a CF of 1.13 on a Dynojet in Lubbock, and I then went to MTI that same summer for a cam swap. They baselined the car on their dyno before the swap, and with a CF of 1.01 I dynoed 392 RWHP. While it's not a CF < 1, it is a considerable difference in CF's between dynos.
Dynos are 100% tuning tools, as Terry stated. People get SO wrapped up in peak dyno #'s, and it's getting really old. We have all of these magical #'s floating around without any track times. While it doesn't apply for ALL of them, many of the cars are running what I would consider big cams for stock cubes. I've seen more than one graph that would require shift points of 7,000 RPM with stock heads! It's all top-end power, and you'd better have a car setup right to get it to work its best (steep gears, FAT stall if an A4, etc.). There are many ways to eek more power out on a dyno as well, so the #'s don't mean much without track times for me.
Dynos are 100% tuning tools, as Terry stated. People get SO wrapped up in peak dyno #'s, and it's getting really old. We have all of these magical #'s floating around without any track times. While it doesn't apply for ALL of them, many of the cars are running what I would consider big cams for stock cubes. I've seen more than one graph that would require shift points of 7,000 RPM with stock heads! It's all top-end power, and you'd better have a car setup right to get it to work its best (steep gears, FAT stall if an A4, etc.). There are many ways to eek more power out on a dyno as well, so the #'s don't mean much without track times for me.
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Launching!
Joined: Nov 2001
Posts: 227
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From: Valencia, CA
Re: SAE dyno correction factors and the LS1 Well there probably aren't a lot of people that dyno their cars with out any changes, so it would be tough to have a really true sample size.
I tested two of our shop cars just to see if there was a difference. What caught my eye was an unexplainable loss of power on my car. So then I tested another car that had no changes.
The test temps were 15deg hotter, so the Correction was higher, but even with that bother cars were down on power. I think they both lost 5-8 RWHP.
There may be many reasons for this, but one thing a correction factor can't account for is how the engine runs with the colder air and denser air.
So who knows, it kinda works the same way at the track too. A car will run a lot better when the air is cold, pressure high and humidity low. My guess better than what a car would run corrected in hot muggy weather.
I tested two of our shop cars just to see if there was a difference. What caught my eye was an unexplainable loss of power on my car. So then I tested another car that had no changes.
The test temps were 15deg hotter, so the Correction was higher, but even with that bother cars were down on power. I think they both lost 5-8 RWHP.
There may be many reasons for this, but one thing a correction factor can't account for is how the engine runs with the colder air and denser air.
So who knows, it kinda works the same way at the track too. A car will run a lot better when the air is cold, pressure high and humidity low. My guess better than what a car would run corrected in hot muggy weather.
TECH Apprentice
Joined: Jan 2002
Posts: 356
Likes: 0
From: Texas
Re: SAE dyno correction factors and the LS1 I had an interesting opportunity last summer to make a point about correction factors. I dyno'd my 98 WS6 3 days apart, but 5000 plus feet in elevation difference. Correction factor in Arizona was 1.03 and the correction factor in Colorado was 1.24. The SAE corrected numbers came out to 432rwhp/398rwtq in Arizona and 426rwhp/392rwtq in Colorado. No changes made to the car, except differences resulting from the 1,000 mile drive.
Todd
Todd
