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2020 SPS, M6, Go Mango
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Hey all

Curious what others people's thoughts are on the accuracy of the performance pages, specifically the dyno sections. How exactly does this measure power? Is it measuring like a true dyno, or is it guessing what it "should" be based on incoming factors, throttle usage, etc?

The dyno usually will barely crest 400hp after full throttle acceleration. We all know rated power is at the crank, and wheel hp is after a loss of 20% or so via drive train loss. But I also doubt it is somehow measuring power at the rear wheels.

Soo...?
 

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2018 Scat Pack SHAKER in Plum Crazy- GONE :-(
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Based on projected torque based on calculated fuel/timing map based on ambient air and engine temp (and actual fuel relating to timing map). So, my W.A.G. is that it is "fairly" accurate, especially in reference to other times in the same vehicle which is all dyno's are really good at, right? (before/after comparison with same combo on same dyno, not comparing 1 dyno to another)
 

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2020 Dodge Challenger Hellraisin Scat Pack
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Hey all

Curious what others people's thoughts are on the accuracy of the performance pages, specifically the dyno sections. How exactly does this measure power? Is it measuring like a true dyno, or is it guessing what it "should" be based on incoming factors, throttle usage, etc?

The dyno usually will barely crest 400hp after full throttle acceleration. We all know rated power is at the crank, and wheel hp is after a loss of 20% or so via drive train loss. But I also doubt it is somehow measuring power at the rear wheels.

Soo...?
Performance Pages dyno torque is derived from engine load which is itself a derived value. Torque is "computed" from load and from this HP is calculated.

The formula for HP is rather simple: Torque x RPM / 5,252.

"Torque" in the above formula is what is derived from the load.

The numbers PP supplies for torque and power are interesting but are really not test dyno grade numbers. I view these numbers once in a while just to get a feel for how hard, or not, the engine is working under some conditions. For instance in my Hellcat on a drive from CA to AR I sometimes monitored these dyno numbers just to see how hard the engine was working to maintain speed on the freeway and when climbing grades to clear passes at between 2700 feet to over 7000 feet.

More recently with my Scat Pack I view these numbers as I drive around to get a feel for how hard the engine is working. I have not yet had it out on a long freeway road trip.
 

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When you look at your tune with HP tuners, there is a calculated and expected flywheel Torque. When my 2015 was new I had to have the Transmission reflashed because it threw a code, something about "unexpected Torque" or "Torque Calculation error", can't quite remember so I would think they are fairly accurate if Actual Torque was different than calculated Torque and it knew it and threw a code.
 

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When you look at your tune with HP tuners, there is a calculated and expected flywheel Torque. When my 2015 was new I had to have the Transmission reflashed because it threw a code, something about "unexpected Torque" or "Torque Calculation error", can't quite remember so I would think they are fairly accurate if Actual Torque was different than calculated Torque and it knew it and threw a code.
The HP Tuners device uses the same engine load to derive torque and power from as PP.

I would hazard a guess that any limit threshold numbers regarding torque levels at various places in the transmission are based on real dyno numbers correlated with what the engine controller arrives at using the telemetry it has available and from which it calculates engine load.

The PP torque/HP numbers are not junk, and are relative, but not something I'd use to try to "tune" the engine or even confirm its "tune".
 

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I just add a zero to everything and am perfectly happy.;)
 

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You can calculate estimated horsepower based on the vehicle’s weight & trap speed (or ET). Performance Pages could simply do that because it knows your speed & time & hopefully the engineers included the vehicle’s weight. The formula is shown here.

There are several online calculators & they give similar but slightly different results. One of the differences is that “234” constant shown in the above link which is derived from empirical data based on many drag strip runs. This explains more.
NOTE: sometimes the graphs won't display because of the secure "https". This is mentioned on the stealth316 website. Delete that prefix if you want & see all the data.

Some of the online calculators provide crank horsepower & some deduct 10%-15% for drive train loss and give you WHP. But it's all a rough figure.

But real dynos are not exact either. From what I’ve seen there is lot of variation comparing horsepower between a Dynojet and a Mustang dyno.
 

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We all know rated power is at the crank, and wheel hp is after a loss of 20% or so via drive train loss. But I also doubt it is somehow measuring power at the rear wheels.

Soo...?
20% is no longer accepted as accurate since auto transmissions have become way more efficient. With that said how much each drivetrain loses is not an exact science.
 

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20% is no longer accepted as accurate since auto transmissions have become way more efficient. With that said how much each drivetrain loses is not an exact science.
100% ^
parasitic loss depends on the car and its configuration.
The supercharger alone on a hellcat requires some 75hp to churn up....
electric vs power steering.
auto vs manual trans.
RWD vs AWD.
too many varibles to apply a universal %.
 

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...
electric pump vs engine driven pump power steering.
...
EDITED: ^ That alone is worth the 15HP on the newer 392s!
 

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20% is no longer accepted as accurate since auto transmissions have become way more efficient. With that said how much each drivetrain loses is not an exact science.
While automatics have become more efficient the torque converter kind still exact a parasitic power loss. The "loss" diminishes some when at some speed the torque converter is locked up and fluid coupling (temporarily) replaced by a direct engine to transmission connection.

IRS adds to the drive train loss, also, and this is present of course 100% of the time.

The load parameter is based on various other telemetry which reflects how hard the engine is working. This includes the power that is lost due to the drive train, water pump, A/C system, alternator, and even the power necessary to spin the supercharger in the case of the Hellcat/RE.

Since Dodge must know owners are going to use this digital display to "dyno" their car's engine output I'm sure the output has been tweaked to ensure it will/can deliver numbers that match the advertised HP/torque claims.

A "failure" to get the reading to its max numbers is likely due to operating conditions. The engine controller seeks to deliver the torque demanded by the driver as signaled by the electronic gas pedal. The engine controller will do this but it doesn't necessarily have to deliver max torque and thus HP under every hard application of the throttle.

And there can be other factors which can have the output lower than it would otherwise be. Weather conditions, gasoline quality, engine "tune" to name the ones that come to mind.

Based on my experience ideal conditions are needed when using full throttle for the digital torque/HP numbers to get close to the advertised torque/HP numbers. Remember too the peak HP is obtained at some high RPM level over the torque peak RPM. The advertised HP number might only be present a short time before as the engine reaches the max power RPM point and continues to the point it triggers the rev limiter.

Thus unless one was staring at the PP dyno "gauges" he might miss this. In my experience when operating my Hellcat at full throttle the car/road took 110% of my attention. I did not have the luxury to stare at the dash to admire the speed, or the torque and HP numbers.
 

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While automatics have become more efficient the torque converter kind still exact a parasitic power loss. The "loss" diminishes some when at some speed the torque converter is locked up and fluid coupling (temporarily) replaced by a direct engine to transmission connection.

IRS adds to the drive train loss, also, and this is present of course 100% of the time.

The load parameter is based on various other telemetry which reflects how hard the engine is working. This includes the power that is lost due to the drive train, water pump, A/C system, alternator, and even the power necessary to spin the supercharger in the case of the Hellcat/RE.

Since Dodge must know owners are going to use this digital display to "dyno" their car's engine output I'm sure the output has been tweaked to ensure it will/can deliver numbers that match the advertised HP/torque claims.

A "failure" to get the reading to its max numbers is likely due to operating conditions. The engine controller seeks to deliver the torque demanded by the driver as signaled by the electronic gas pedal. The engine controller will do this but it doesn't necessarily have to deliver max torque and thus HP under every hard application of the throttle.

And there can be other factors which can have the output lower than it would otherwise be. Weather conditions, gasoline quality, engine "tune" to name the ones that come to mind.

Based on my experience ideal conditions are needed when using full throttle for the digital torque/HP numbers to get close to the advertised torque/HP numbers. Remember too the peak HP is obtained at some high RPM level over the torque peak RPM. The advertised HP number might only be present a short time before as the engine reaches the max power RPM point and continues to the point it triggers the rev limiter.

Thus unless one was staring at the PP dyno "gauges" he might miss this. In my experience when operating my Hellcat at full throttle the car/road took 110% of my attention. I did not have the luxury to stare at the dash to admire the speed, or the torque and HP numbers.
A Torque converter Multiplies Torque. When the output side(Engine side) is spinning faster than the output side (Transmission) this increases torque.
 

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A Torque converter Multiplies Torque. When the output side(Engine side) is spinning faster than the output side (Transmission) this increases torque.
Yes, but there is still a loss associated with this fluid coupling. That is why in order to improve gas mileage numbers and reduce CO2 output car makers have resorted to torque converters that can be locked when the torque multiplication feature falls below a certain level.

It also has drive the development of automatics that do away with a torque converter and instead use clutches. The clutch slips very briefly when taking off from a stop -- just like the clutch in a manual transmission car -- but once under way the clutches are disengaged/engaged with minimal slippage. And once in a gear there is no slippage.
 

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Yes, but there is still a loss associated with this fluid coupling. That is why in order to improve gas mileage numbers and reduce CO2 output car makers have resorted to torque converters that can be locked when the torque multiplication feature falls below a certain level.

It also has drive the development of automatics that do away with a torque converter and instead use clutches. The clutch slips very briefly when taking off from a stop -- just like the clutch in a manual transmission car -- but once under way the clutches are disengaged/engaged with minimal slippage. And once in a gear there is no slippage.
I believe what you are referring to is a "Clutch Flite". Those were awesome, an Automatic transmission mounted to a bellhousing with a clutch pack so you could launch the car like a stick shift car at the track and it would shift like an automatic (fast and accurate). I'd love to have that setup with the 8 speed, no need for a stall speed converter! 3 pedals and an auto shifter would keep everyone guessing!
 

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Yes, but there is still a loss associated with this fluid coupling. That is why in order to improve gas mileage numbers and reduce CO2 output car makers have resorted to torque converters that can be locked when the torque multiplication feature falls below a certain level.
The torque converter is locked up on the dyno when measuring hp/tq so fluid coupling doesn’t really have anything to do with any readings that we are talking about.

My last car I did a locked and unlocked dyno and there was a 35 hp difference for reference.
 

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I believe what you are referring to is a "Clutch Flite". Those were awesome, an Automatic transmission mounted to a bellhousing with a clutch pack so you could launch the car like a stick shift car at the track and it would shift like an automatic (fast and accurate). I'd love to have that setup with the 8 speed, no need for a stall speed converter! 3 pedals and an auto shifter would keep everyone guessing!
I was not referring to the Clutch Flite transmission. I vaguely recall something called that or something like that.

What I was referring to was in particular the Porsche PDK transmission which uses two wet clutch packs each driving an input shaft. One shaft runs inside the other and are coupled to different gear sets. One clutch pack (pack because they are multi-plate clutches) is connected to odd gears the other to even gears. One is connected to reverse gear, too.

Had a chance to experience this transmission when I had a loaner vehicle, Macon a couple of times, and a Cayenne at least once. Upon taking off the computer controls the amount of engagement and gets the vehicle moving off promptly. Gear changes lack that "soft" feel because the transmission has no fluid coupling. But the gear changes are not harsh either. Clutches are disengaged/engaged in such as way the transition from one gear to the next is pretty smooth. The transmission's performance was quite impressive.

Downsides? Of course came with a higher price -- much like the Hellcat's A8 vs. the 6-speed -- and the weight was considerable vs. a comparable manual transmission. But the transmission appeared quite durable. Vehicles were "tested" using the transmission's launch control and even after dozens of these back to back the transmission fluid temperature was well within spec. Porsche claimed it didn't even bother to count the number of times launch control was used.

On the track the transmission was quite impressive. The general rule is to avoid changing gears in mid turn to avoid the risk of upsetting the car. In one test of a car with PDK the driver left the transmission in automatic shift mode. At some point in a turn the transmssion shifted. The shift was so smooth and yet fast the driver and the passenger both commented upon the shift in mid turn.

Some other car makers offer similar transmissions generally with one clutch pack servicing all gears. The clutch can be wet and a single or multi-plate type or dry and single or multi-plate type. I really haven't kept current on the various offerings for some time.
 
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