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Was the air quality very poor from the fires? IF it was really bad, it could explain a drop but 3 seconds is a huge loss
every turn we had to put on the brakes and park your car. ....... you have to wait until the car is straight before you add power. only the 800hp nascar truck got a decent time, but even he was 2-3seconds off his best.
there were several cars that really badly oiled the track down
The drag strip quarter mile trap speed MPH seems to correlate well with the average dyno power between the shift points holding the vehicle weight constant.
The ET can be all over the place depending on the suspension, tires, track condition, driver skill, etc. so it's not a good measure of engine power. I assume that same is even more true about lap times on a road course, so many other factors.
Different acceleration ramp. Your final gear ratio is at the axle. You tire diameter is a lever that slows down the drum acceleration but allows more too end speed.
A load Dyno won't see it as much. But when all you're doing is counting the time between drum revolutions, a larger tire will accelerate it slower. Which over more time reads less energy applied to the drum.
The trade off is a lot more drum speed.
Other result is like...
(New tire diameter / old tire diameter) * old axle ratio = new axle ratio..[/QUOTE]
Do you see the error in your statements..... however you are right, the rear tire size DOES effect rear axle ratio when changed. BUT that is not your statement. YOU said, that a larger tire will accelerate the drum slower, this in NO WAY means there is less energy applied to the drum. you take the angular velocity of the drum at two points in time during the acceleration .... that change in KE (Joules) vs the time is the HP. any given HP will have the same rate of change of KE. (by definition) you are trying to invent your own physics definitions. dont do that! In other words, you measure the change in RPM of the drums over 1 second , with a taller tire, the RPM difference will be based on two higher RPM values. the net calculation will show no difference in power..... in fact, it might be slightly more due to gains in efficiency (rollng friction, or gearing does that) does this make sense??
It certainly wasn't "doctored".
That's the graph their computer spit out. They claimed that the correction factor was always the same, on their dyno.
Something was clearly wrong.
Yes, it was doctored.
Maybe it's the same shop who did this:
Can you see it now? Back in the day when this happened, it was 'Z' who gets credit for noticing it.
BTW, the displayed cheat was worth 70 rwhp, so that car only dyno'd at 401 rwhp, not 471.
So Greg, I'm sure that your 2nd graph was manipulated in the same way. Who gave you this run, and which shop did it - they are clearly cheaters too.
So the next question is, how were they able to do that?
Hint - There are more clues in the displayed run conditions...
Some people hook up the dyno air temperature sensor to the intercooler outlet tank. This will give inflated corrected power numbers from the dyno, but it can actually be quite helpful with tuning. This is because if the intercoolers heat soak or cool down while the adjustments are made, the power correction formula will undo some of this effect that can garble there effect of tuning changes on power. It’ll be easier to find the best setting for fuel and spark that way. Better yet, one can also run garden hose of water thru the intercoolers to stabilize them into a near-constant temperature while the changes are being made.
One should of course let the car reach normal temperature, unhook the ambient temperature probe from the intercooler, etc. to get an actual measured power run.
A separate issue is that pump gas turbo cars’ power can’t really be corrected to standard ambient conditions because the knock (and other) constraints shift. SAE J1349 correction factor standardizes temperature to 77-degrees F, 29.23inHg and dry, 0-percent humid air. A turbo car should by dynoed for the final power number in conditions that are as close to these conditions as possible. Temperature and elevation are the biggest deals, humidity less of an issue.
i think its funny when people post about things they THINK they know about and then also claim to be an expert. Yes, you are dead on right. any system can produce bogus output data, a dynojet 248e is very accurate and truly representative of an car's performance .
Originally Posted by SwayBar
Yes, it was doctored.
Maybe it's the same shop who did this:
Can you see it now? Back in the day when this happened, it was 'Z' who gets credit for noticing it.
BTW, the displayed cheat was worth 70 rwhp, so that car only dyno'd at 401 rwhp, not 471.
So Greg, I'm sure that your 2nd graph was manipulated in the same way. Who gave you this run, and which shop did it - they are clearly cheaters too.
So the next question is, how were they able to do that?
Hint - There are more clues in the displayed run conditions...
When in doubt... if you cant control all the variables, or are in doubt, just look at actual " uncorrected" values.... then you can see what the car is actually doing on that day. I usually make sure i grab the SAE and the uncorrected numbers off all dynos and do one in the cold of winter and the heat of summer for correlation
mk
Originally Posted by ptuomov
Here’s something that is relevant for turbo cars.
Some people hook up the dyno air temperature sensor to the intercooler outlet tank. This will give inflated corrected power numbers from the dyno, but it can actually be quite helpful with tuning. This is because if the intercoolers heat soak or cool down while the adjustments are made, the power correction formula will undo some of this effect that can garble there effect of tuning changes on power. It’ll be easier to find the best setting for fuel and spark that way. Better yet, one can also run garden hose of water thru the intercoolers to stabilize them into a near-constant temperature while the changes are being made.
One should of course let the car reach normal temperature, unhook the ambient temperature probe from the intercooler, etc. to get an actual measured power run.
A separate issue is that pump gas turbo cars’ power can’t really be corrected to standard ambient conditions because the knock (and other) constraints shift. SAE J1349 correction factor standardizes temperature to 77-degrees F, 29.23inHg and dry, 0-percent humid air. A turbo car should by dynoed for the final power number in conditions that are as close to these conditions as possible. Temperature and elevation are the biggest deals, humidity less of an issue.
Nothing wrong with those curves per se. There are 2 different runs, red and blue. Both the torque & HP numbers appear the same at 5252 RPM for the red set and for the blue set. Red engine not making much torque below 3500 is another story...
did you NOT see the correction factors?>>>>>> LOOK!!
Considering that the lowest non-hurricane reading in the lower 48 states was 28.10" in New York in 1914, the reading on the lower graph of 26.10 is just a little bit suspicious.
Yes, I had to look it up. I'm something of a weather geek, but not that bad.
Considering that the lowest non-hurricane reading in the lower 48 states was 28.10" in New York in 1914, the reading on the lower graph of 26.10 is just a little bit suspicious.
Yes, I had to look it up. I'm something of a weather geek, but not that bad.
Do the dyno sheets have a date and location? I can’t see the sheet on my phone for some reason. If they do, then one can check the actual weather conditions and correct the correction factor! Anyone up to the task?
Considering that the lowest non-hurricane reading in the lower 48 states was 28.10" in New York in 1914, the reading on the lower graph of 26.10 is just a little bit suspicious.
Yes, I had to look it up. I'm something of a weather geek, but not that bad.
yeah.. got to love the dyno run being conducted during a near record lowest barometric reading ever seen on the earth.. Greg has to be a LITTLE more aware of these subtleties .
Originally Posted by ptuomov
Do the dyno sheets have a date and location? I can’t see the sheet on my phone for some reason. If they do, then one can check the actual weather conditions and correct the correction factor! Anyone up to the task?
So with a lower pressure, there's less force, or air available to fill the cylinders of the engine, so the software corrects for that and increases the correction factor accordingly, and in the case, by 15%.
BTW, this dyno was run in California, and someone went thru a lot of trouble to take the Dynojet sensor, put it a container, and create a partial vacuum to 'fool' the readings so it will make its correction accordingly by adding 15% to the run.
Apparently the team who did it wasn't as clever as they thought they were since they weren't aware their cheat is displayed in plain sight for everyone to see.
Now take a look again at Greg's second dyno - where are the run conditions? That should have been clue #1 for Greg that something's not right with that sheet.
Another thing. At the time EVERYONE who had that same roots supercharger kit were putting out roughly 400 rwhp. And all of a sudden, here's one doing 471, which was automatically suspicious even before discovering the cheat.
The point being, for anyone to take that 2nd GTS graph seriously is just silly. And to use it as 'proof' that dynos can't be trusted is irresponsible to say the least.
Just like a gun. It's not the gun that kills people, it's the person wielding it:
Don't blame the gun, blame the person.
Don't blame the dyno, blame the cheaters.
And finally, all things being equal and true:
Don't blame the dyno, blame the engine it's measuring.
I use the dyno as a tool. Bill and I have been dynoing the car once or twice a year since 2008 (and I did it before that since 2001 but without the Sharktuner). We try to get the same dyno, but they didn't seem to stay in business very long... We try to get the car tuned as close as we can to our specs on the dyno, then do the final tuning at altitude during race week. We've used Dynojets, Dynapacks, and Mustang dynos. They give different numbers, but we just focus on AFR, knocks, RPM, and comparative rwhp per session.
It's not about bragging rights as much as getting the car to run the best it can during the event. If your selling something, you want something to advertise. If you're a bench racer, then that's all you have to show for the money you put into your car (other then shiny parts). But to serious performance people, it's a tool to get the car to run the best it can, whether it's lap times, quarter miles, engine/car endurance, top speeds, or just get great engine response.
__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM) http://928.jorj7.com
yep, it's a little ignorant to look at a dyno that has had been either altered or had bad inputs, and condemn all dynos, just as you wouldnt believe a scale output for someone weighing more weight than they claim. thats why i always use "actual" data which is uncorrected on all dynos JUST incase there is a variable that i have no control of or a mistake or misreading has been made.
Originally Posted by SwayBar
Very good, nicely done!
So with a lower pressure, there's less force, or air available to fill the cylinders of the engine, so the software corrects for that and increases the correction factor accordingly, and in the case, by 15%.
BTW, this dyno was run in California, and someone went thru a lot of trouble to take the Dynojet sensor, put it a container, and create a partial vacuum to 'fool' the readings so it will make its correction accordingly by adding 15% to the run.
Apparently the team who did it wasn't as clever as they thought they were since they weren't aware their cheat is displayed in plain sight for everyone to see.
Now take a look again at Greg's second dyno - where are the run conditions? That should have been clue #1 for Greg that something's not right with that sheet.
Another thing. At the time EVERYONE who had that same roots supercharger kit were putting out roughly 400 rwhp. And all of a sudden, here's one doing 471, which was automatically suspicious even before discovering the cheat.
The point being, for anyone to take that 2nd GTS graph seriously is just silly. And to use it as 'proof' that dynos can't be trusted is irresponsible to say the least.
Just like a gun. It's not the gun that kills people, it's the person wielding it:
Don't blame the gun, blame the person.
Don't blame the dyno, blame the cheaters.
And finally, all things being equal and true:
Don't blame the dyno, blame the engine it's measuring.
Jorg, and you know the 25 years of moding and dynoing ive had on a vast number of engines. dynos, particularly the dynojet is a measuring tool. it is very accurate. you can search for the same dyno (actually the same) and it makes little difference. you accelerate the drums, or you dont. its like a drag race, either you ran 10flat, or you didnt. are their factors, certainly, but on the dyno there are subtle changes that can be made. tire pressure, strap down force and the air that is being consumed by the engine.. the correction factors can make a big difference , so can others..........but uncorrected will be what the engine and chassis did on that particular day. you cant cheat it. proof is 20 years of dynoing my cars where ive never had a variance more than 2-5 hp that wasnt due to a problem and never had more than 10hp due to conditions.. you have seen the dyno runs... ive posted most of them here. brake dynos use different conversions, still valid, but not as "actual" as a dyno jet. again, if you can know the size and mass of a drum, and measure a change in angular velocity vs time, then you can easily measure HP accurately.
Originally Posted by jorj7
I use the dyno as a tool. Bill and I have been dynoing the car once or twice a year since 2008 (and I did it before that since 2001 but without the Sharktuner). We try to get the same dyno, but they didn't seem to stay in business very long... We try to get the car tuned as close as we can to our specs on the dyno, then do the final tuning at altitude during race week. We've used Dynojets, Dynapacks, and Mustang dynos. They give different numbers, but we just focus on AFR, knocks, RPM, and comparative rwhp per session.
It's not about bragging rights as much as getting the car to run the best it can during the event. If your selling something, you want something to advertise. If you're a bench racer, then that's all you have to show for the money you put into your car (other then shiny parts). But to serious performance people, it's a tool to get the car to run the best it can, whether it's lap times, quarter miles, engine/car endurance, top speeds, or just get great engine response.
__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM) http://928.jorj7.com
08-31-2020, 06:25 PM
