Jeep Wrangler Forum banner

1 - 20 of 142 Posts

·
Registered
Joined
·
904 Posts
Discussion Starter #1
I've been thinking about drive train loss lately!!!!! It was probably because I read something about Prodigy Performance claiming 400WHP for their new Turbo-Kit. And if we go with the figure that everyone on the Jeep Forums loves to quote of 33% or 1/3rd if you like to be true accurate. In this case it really works out nicely.

1/3rd of x = 400 or simply put 600hp * 1/3 = 200 Hp lost so -- that leaves us with the magic 400hp at the wheels...

200Hp-- seems pretty innocuous right? Let's convert it into something more useable like watts-- mechanical SAE HP is like 745.69 so multiple that number by 200; and bam you have like 149,000 plus watts of energy being lost! In what form? HEAT!!! That's right all of it ends up as heat! Okay, so you have all this heat. Let's use a figure everyone knows and loves British Thermal Units aka the BTU. So, now we must take that 149,000 x 3.412142 = 508,409.158 BTU being developed. Still, it is too abstract I fear for some.

Well, let's put this way 69,000 BTU will heat roughly 1800sq feet of your house. You could heat 7.3682 different rooms that are 1800sq feet or one starter McManison of 13,262. 8476 Sq Feet nicely! Or cool it if you live in a hot climate. Either way is an acceptable mental image of this transfer of energy: as one giant heater or as a giant ac system.

So, you tell me do you really think your little aluminum transmission is soaking at least 70% of this heat? Where is it going? Is your floor pan over the transmission hot enough to burst into flames? When you drive the Jeep down the road do you need to have a fan blowing over the floor pan so you don't burn yourself? Does your big gulp form the 7 11 turn from 34 F to 120 F in a matter minutes? I think not.

So, you say wait a minute the power drain doesn't last for the entire trip. It soon drops down. So, let's say it goes from 1/3rd to 1/5 th or 20 Percent... That's a big drop in loss nearly 80hp. Still, you have over 300,000 BTU of heat to deal with. So, you've just downgraded from the McMansion to the Super-Middle Class Swank Pad of 7,496sq ft roughly!!!! That's a lot of heat. And worst, yet, this means you just bumped up in hp from 400hp to 480hp. I want to know why the Chassis dyno doesn't show this miraculous event... Better than Water turned into wine-- hp from the divine power Gods-- NO LESS! So, basically, if you believe this myth that your car will get 80hp or whatever more once you've stopped accelerating it hard.... I have a few bridges to sell you in the Tri-State Area! They're older but really prime locations!


So, I'm not sure what the answer is just, yet. I have a few books ordered from Amazon on transmission design and testing and I will find out what the experts say. But, I know this 200hp isn't vaporizing in the form of heat! That is not if your Jeep still has fluids and the carpeting in it hasn't spontaneously combusted yet.
 

·
Registered
Joined
·
1,401 Posts
I read something about Prodigy Performance claiming 400WHP for their new Turbo-Kit.
No. They only said recently that they plan to use a boost controller in the near future to add more boost and aim for 400+ whp. The current kit they offer has a claimed 370-380 whp.

you have like 149,000 plus watts of energy being lost! In what form? HEAT!!! That's right all of it ends up as heat!
No. Most of the drivetrain loss is in the form of accelerating the drivetrain components.

The large (33%) drivetrain loss that has been observed is due to the use of a relatively fast acceleration sweep test on an inertia dyno. It takes energy to rotationally accelerate the engine itself, transmission, driveshafts, axles, tires, etc.

If you were to run a steady-state dyno test (where the dyno holds the engine RPM steady and records how much resistive torque was necessary to do so, rinse and repeat at many different RPMs to get data across the whole range), you would see much lower drivetrain loss. When in steady state, there is no acceleration, so the only loss is due to friction. In that case, the lost energy would all be going to heat and sound.
 

·
Registered
Joined
·
485 Posts
It's really hard to imagine that the acceleration of the mass is the major, or even a significant amount of the calculated loss. The dyno runs I've seen reached a maximum RPM and were held long enough to not be gaining any more speed before the throttle was cut, meaning the loss due to acceleration was done and a steady state was achieved. I know it plays a large part in the driving experience and real world efficiency, though.

I've heard and read that 3% is a good round number to use as a loss for any gear set the power feeds through. A tranny will have a number of these sets depending on what gear is running and if the lay shaft is being used. Manual trannys are spinning all the gears even if they only use one or two sets at a time. That's why I contend that overdrives add an inefficiency to the system, where a straight through top gear would be more efficient. Overdrives seem more hype than fact, except that if the top gear was straight through, the lower gears would have to be larger to carry more torque.

Another fairly large loss must be the differential. Hypoid gears are not very efficient and they need heavy weight lubricant that has a lot of pumping losses. But they can get rid of a lot of heat as they are right out there in the wind stream with a lot of surface area and sitting crossways.

Auto trannys have a large capacity cooling system with a water to water heat exchanger. They also have a constantly running oil pump and internal oil pressure feeding through lots of passages. The torque converter is very good at making heat as it does it's own pumping and slipping. Autos dump lots of heat just to survive.

Even the brakes use some power. Disk brakes are always dragging a bit.

When you consider that the engine wastes about 2/3 of the fuels energy, it really makes the whole package seem pretty bad. Then remember that the trans, drivelines and differentials are only there to adapt the engine to the wheels. What a terrible system! It's only that we've had a hundred plus years to refine it to this point that makes it seem as good as it is. And it's why pancake motors in the wheels, instead, would be so nice. If we could just figure out how to supply them with efficient power.
 

·
Registered
Joined
·
1,401 Posts
It's really hard to imagine that the acceleration of the mass is the major, or even a significant amount of the calculated loss.
No imagination necessary. It's all explained by well understood laws of motion. Simple physics, combined with the fact that the Wrangler has more heavy-duty (which are literally more heavy) drivetrain components than typical cars.
 

·
Registered
Joined
·
1,542 Posts
No imagination necessary. It's all explained by well understood laws of motion. Simple physics, combined with the fact that the Wrangler has more heavy-duty (which are literally more heavy) drivetrain components than typical cars.
not to mention I'm sure they're not machined with the tightest tolerances.
 

·
Registered
Joined
·
485 Posts
No imagination necessary. It's all explained by well understood laws of motion. Simple physics, combined with the fact that the Wrangler has more heavy-duty (which are literally more heavy) drivetrain components than typical cars.
Sorry you missed my point that there is a difference between steady state delivery and accelerating mass. If you can't separate those two, you can't really talk about how much loss there is in a given system. Driving involves both, constant power delivery does not, accelerating a system under load is both. Driving on the highway vs. driving in town. Simple physics. The imagination part was considering what percentage of the total was acceleration in a hypothetical situation. We don't know unless we have a chart of rate of change, total RPM achieved, how many times and the mass of the system. We also don't know how much energy was recovered during deceleration while driving our hypothetical drivetrain. So, we have to imagine a bit to discuss the variables. See what I mean?
 

·
Registered
Joined
·
1,401 Posts
Ok. Let me put it another way...

No imagination necessary, because there are already multiple dyno results (from an acceleration sweep test) with peak numbers about 30-33% lower than the SAE certified net engine power output results (which are obtained with steady-state tests). Both RIPP and JeepLab independently got similar results.

As Krakus pointed out, there's no way that the majority of that is due to friction in the drivetrain, because that would produce absurd amounts of heat. The majority therefore must be due energy lost to accelerating the drivetrain.
 

·
Registered
Joined
·
1,401 Posts
The dyno runs I've seen reached a maximum RPM and were held long enough to not be gaining any more speed before the throttle was cut, meaning the loss due to acceleration was done and a steady state was achieved.
What kind of dyno runs have you watched?

Do you mean that they ran the engine up to the rev limiter, and it stopped accelerating due to the rev limiter? If so, that is completely unrelated.

During the acceleration sweep through the rpm range, there definitely is acceleration (not steady state). Hitting and holding throttle at the rev limiter doesn't really count as achieving steady state, because the computer is artificially reducing full-throttle power output of the engine to prevent it from accelerating.
 

·
Registered
Joined
·
2,148 Posts
A slightly twisted view...

I've been thinking about drive train loss lately!!!!! It was probably because I read something about Prodigy Performance claiming 400WHP for their new Turbo-Kit. And if we go with the figure that everyone on the Jeep Forums loves to quote of 33% or 1/3rd if you like to be true accurate. In this case it really works out nicely.

1/3rd of x = 400 or simply put 600hp * 1/3 = 200 Hp lost so -- that leaves us with the magic 400hp at the wheels...

200Hp-- seems pretty innocuous right? Let's convert it into something more useable like watts-- mechanical SAE HP is like 745.69 so multiple that number by 200; and bam you have like 149,000 plus watts of energy being lost! In what form? HEAT!!! That's right all of it ends up as heat! Okay, so you have all this heat. Let's use a figure everyone knows and loves British Thermal Units aka the BTU. So, now we must take that 149,000 x 3.412142 = 508,409.158 BTU being developed. Still, it is too abstract I fear for some.

Well, let's put this way 69,000 BTU will heat roughly 1800sq feet of your house. You could heat 7.3682 different rooms that are 1800sq feet or one starter McManison of 13,262. 8476 Sq Feet nicely! Or cool it if you live in a hot climate. Either way is an acceptable mental image of this transfer of energy: as one giant heater or as a giant ac system.

So, you tell me do you really think your little aluminum transmission is soaking at least 70% of this heat? Where is it going? Is your floor pan over the transmission hot enough to burst into flames? When you drive the Jeep down the road do you need to have a fan blowing over the floor pan so you don't burn yourself? Does your big gulp form the 7 11 turn from 34 F to 120 F in a matter minutes? I think not.

So, you say wait a minute the power drain doesn't last for the entire trip. It soon drops down. So, let's say it goes from 1/3rd to 1/5 th or 20 Percent... That's a big drop in loss nearly 80hp. Still, you have over 300,000 BTU of heat to deal with. So, you've just downgraded from the McMansion to the Super-Middle Class Swank Pad of 7,496sq ft roughly!!!! That's a lot of heat. And worst, yet, this means you just bumped up in hp from 400hp to 480hp. I want to know why the Chassis dyno doesn't show this miraculous event... Better than Water turned into wine-- hp from the divine power Gods-- NO LESS! So, basically, if you believe this myth that your car will get 80hp or whatever more once you've stopped accelerating it hard.... I have a few bridges to sell you in the Tri-State Area! They're older but really prime locations!


So, I'm not sure what the answer is just, yet. I have a few books ordered from Amazon on transmission design and testing and I will find out what the experts say. But, I know this 200hp isn't vaporizing in the form of heat! That is not if your Jeep still has fluids and the carpeting in it hasn't spontaneously combusted yet.
You are correct. A lot of it is not in the form of heat. Start off by learning how a torque converter works. A lot of your answer is right there.
Then maybe a book on P.T. Barnum, to learn about marketing. :drinks:

What's really important in the whole forced induction upgrade debate is, can you beat your buddy to the best parking spot at the beach volley ball tournament. Got to love Summer! :awesome:
 

·
Registered
Joined
·
485 Posts
Useless,

I didn't say anything about rev limiters. Huh?

Maximum horsepower isn't based on a rev limiter. It's the highest point in the horsepower curve. The engine can still rev higher, but at lower efficiency. When it is putting out it's maximum horsepower and reaches that point it is no longer accelerating. Therefore, inertia is not robbing power. Up to that point, while the engine is accelerating, it is.

Imagine a salt flats car running flat out and reaching top speed. It is no longer accelerating it's gear train and it is putting out it's full horsepower. Imagine driving on level ground on the highway at 60 mph. No longer accelerating, but steady state. Drivertrain losses at that point are not based on accelerating mass, but constant friction losses. That is the point that seems so hard to get. Yes, accelerating mass takes energy, we all know that. But take that away and you can discover how much loss comes from pumping oil and other friction sources. If a vehicle is constantly accelerating and coasting, like driving around town, it has both losses. The engine flywheel is a big source of this. But including the flywheel inertia doesn't help refine the overdrive gear losses. We need steady state losses to look for refinements in gears and oils.

You can argue it if you wish. Rev limiter? Yeah, that's it. It's just the rev limiter.
 

·
Registered
Joined
·
904 Posts
Discussion Starter #11
You are correct. A lot of it is not in the form of heat. Start off by learning how a torque converter works. A lot of your answer is right there.
Then maybe a book on P.T. Barnum, to learn about marketing. :drinks:

What's really important in the whole forced induction upgrade debate is, can you beat your buddy to the best parking spot at the beach volley ball tournament. Got to love Summer! :awesome:
Why would you assume I'm speaking about a torque converter.
 

·
Registered
Joined
·
904 Posts
Discussion Starter #12
No. They only said recently that they plan to use a boost controller in the near future to add more boost and aim for 400+ whp. The current kit they offer has a claimed 370-380 whp.



No. Most of the drivetrain loss is in the form of accelerating the drivetrain components.

The large (33%) drivetrain loss that has been observed is due to the use of a relatively fast acceleration sweep test on an inertia dyno. It takes energy to rotationally accelerate the engine itself, transmission, driveshafts, axles, tires, etc.

If you were to run a steady-state dyno test (where the dyno holds the engine RPM steady and records how much resistive torque was necessary to do so, rinse and repeat at many different RPMs to get data across the whole range), you would see much lower drivetrain loss. When in steady state, there is no acceleration, so the only loss is due to friction. In that case, the lost energy would all be going to heat and sound.


Gears are subject to constant angular acceleration even if the rpm is constant. All we need are small fix amounts to continue to accelerate or decelerate the transmissions gears depending on our desires. My point is that since our gears are always in constant angular acceleration they must also always have a constant centripetal force that either increases or decreases depending on the rpm thus causing the gears to mesh, vibrate, and potentially slip. Not to mention to make noise. So, all of this must occur no matter the actual rpm or rpm range...

Even if we take into account gear inefficiencies-- there is just no way it can be 33%...


So, getting back to my 500k+ BTU's even if you're only producing this for 30-40 seconds that is like exposing the transmission to 1000F for 30-40 seconds. Imagine all that heat??? It would need to be transferred somewhere? Where did go to? Furthermore, once you drop to your lower rate why don't you see an increase in power? It should happen. If accelerating hard caused me to dissipate 200hp into heat and constant operation caused it to say hover around a loss of 100hp.... Why don't these chassis dynos show a sharp spike upwards when they hold maximum peak HP throttle for any length of period?

There is a simple way to test your statement. Go to a chassis dyno hit the gas and hold it for 3 minutes or 4 minutes at 5,000rpm (it seems to be the peak point). You should get back all that hp you claim was used in the fast acceleration minus friction, vibration, and sound.


As for you gears being so heavy duty... Compared to what a Nissan Altima's gearbox or an Eaton Fuller Road Ranger Super 18?


So, let's say you see a drop in loss. Let' say now your chassis dyno for miraculous reason shows that you are now making 555hp at the rear wheels. That means 45 hp was lost to heat and sound. If we do the math again we see it is roughly 114,498 BTU. Let's subtract 50K in BTU value for pumping oil in the differentials and so on. So that leaves us with about 64,000btu still more then enough to heat/cool your average 1200sq ft one bed apartment nicely. Let's say that 70% of that heat is soaked up in the transmission alone. It has the majority of your moving parts after the engine itself, after all, so this is where the majority of lost power will occur. Then you have 44800 BTUS to some how make go away? That's a lot of heat to wick away in a transmission.

44800 BTU for any extended trip like say driving 4-5hrs on highway even at 70-80mph would most like result in your gear oil or transmission fluid turning into a sludge in your transmission and the gearbox breaking...

I know my Eaton-Fuller Road Ranger 6spd runs about 270 degrees when operating with a Izuzu Inline 6 7.8l engine making 250hp and 750ft-lbs peak at 1500rpm... You know I run that all day long for extended periods. I've never seen my gearbox glow cherry red like a header on a top-fuel dragster.


So, we must come to one of two inescapable conclusions:

1) We have no direct way to relate power loss or gain from a chassis dyno test to a phantom flywheel calculation (which is very possible).

or

2) We have to say that, perhaps, our chassis dyno tests have a much greater percentage of error than we first thought?


Now, we can test this out simply: if we test a 3.6L Pentastar engine on a chassis dyno first; thus, we establish the baseline power for the engine output at the wheels; then we establish the engine's power by dynoing it alone establishing the baseline for the crankshaft. So, it really won't matter if the engine makes 285hp or 225hp. Just as long as we have the two baselines. So, then we put a turbo or supercharger on it and get say 285+100hp or 385hp. If we get .33% less using the above mentioned testing method we know we can directly correlate a relationship between drive train loss and 33% as a constant in the Jeep. If not we have to ask some questions about fundamental assumptions.

Myself, I think it is actually both. From my research chassis dynos are just not as accurate to tell wheel hp alone much let along give us any conclusions using phantom flywheel calculations for crankshaft hp.
 

·
Registered
Joined
·
904 Posts
Discussion Starter #13
Here is another good example of a transmission with a fixed rated of hp usage. A supercharger! We all know that a supercharger uses a specific amount of hp to create maximum hp. So, let's say you have a system that creates 1300hp on 50hp. Let's say this same unit works for 500hp to 800hp baseline engines. We know that we can do this simple calculation: (500-50)+1300 = 1750hp maximum potential hp to (800-50)+1300= 2050hp. We know that no matter what the input hp is we will only require 50hp to make an extra 1300hp.

We wouldn't think ,"Oh no, my engine jumped up 300 hp on the baseline; so, I guess my Super will now need 150hp to operate at max hp production. So instead of 2050hp peak hp, I can only expect 1900hp."

So, what is so fundamentally different that we would think that we should see amazing increases in transmission loss that is proportional to the power output.
 

·
Registered
Joined
·
1,401 Posts
I didn't say anything about rev limiters. Huh?
I'll re-quote exactly what you said as a reminder:

The dyno runs I've seen reached a maximum RPM and were held long enough to not be gaining any more speed before the throttle was cut
Maximum RPM is just that. The maximum operating RPM of the engine where the rev limiter kicks in.

I'm now guessing that you intended to say "RPM at which maximum HP occurs"? I'm sure you can see now where I got the idea that you were talking about a rev limiter.

Sounds like you are talking about a steady-state dyno test.

I already talked about steady-state vs acceleration sweep tests in my initial reply on this thread. I know the difference. I acknowledge that you are pointing out that there is no acceleration (and therefore no inertial losses due to the drivetrain) in a steady state test, or when a vehicle has reach its maximum aerodynamically-limited speed.

However, I have no idea what point you are trying to make.

Let me remind you of the topic of this thread: Calling into question the reported ~33% drivetrain loss in Wranglers.

The dyno results that show a ~33% loss are acceleration sweep dyno runs. Not steady state. Therefore, inertial losses due to accelerating the drivetrain are involved.

Here is an example of a dyno run that RIPP performed. Take note of how quickly it accelerates through the RPM range. This is a typical style of dyno test that performance parts manufacturers and magazines use to create dyno charts and determine wheel HP: https://www.youtube.com/watch?v=87CkeT6WSg4
 

·
GO STEELERS !
Joined
·
2,164 Posts
This thread might as well be in Chinese!!!! I don't know what your talking about with all this HP since my goal is to slowly crawl over big rocks. But it is definitely impressive knowing people on the forum know about all this crap !!!
 

·
Registered
Joined
·
524 Posts
Drivetrain loss is very real and can be observed quite easily on a manual transmission with a rear locker.

Put the Jeep in 2WD.

Jack up the rear wheels.

Put the tranny in 1st.

Push the clutch in.

Attempt to rotate one of the rear wheels, as slow as possible, to avoid measuring rotating mass inertia.

Doesn't exactly spin freely does it? And thats the minimum loss. That torque will go up as speed goes up. And thats not even including drivetrain inertia, torque converter losses, or the transfer case operating in 4LO.

Next subject:

A drivetrain can easily handle 100's of kilowatts of waste heat being dumped into it. Although you will never get that to happen for more than a few seconds with a passenger vehicle unless you're on a racetrack.

Lets say our "drivetrain" has a specific heat somewhere between steel and aluminum, so how about 650 J/kg/C.

Lets say it weights 100lbs, or 45kg.

So it requires 30000J to have its temperature raised 1 degree C.

Lets say we are dumping 100hp of waste heat directly into the drivetrain. That would NEVER happen on a Jeep for more than a few seconds, even with a turbo and 500 peak horsepower. But lets just say its happening somehow.

So 100hp is about 75kw, or 75k joules per second.

So in 10 seconds, or drivetrain rises a whopping 25 degrees C. And thats without any cooling system, including zero cooling to the airstream around it.

But yes, it heats your house up or whatever.
 

·
Registered
Joined
·
524 Posts
Energy storage in rotating masses is dependent heavily on geometry, not just mass.

Tranny gears/axles/driveshafts are all very small diameter and not going to store much energy.

Wheels/tires probably store much more energy than the entire drivetrain including the flywheel, at the speeds that are being discussed (dyno pulls).

At low speeds where the engine is putting out max power (1st gear or lower), the drivetrain is storing very little energy. None of the parts with large diameters are spinning fast except the flywheel, and that doesn't store enough energy to be important here.
 

·
Registered
Joined
·
615 Posts
Chassis dynos are not used to measure absolute hp, they are used as tuning tools.
You can manipulate the numbers on a chassis dyno by adjusting tire pressure, tire construction, tire size, strap tension underhood temps etc etc..
Don't worry about the absolute numbers, the idea of their value is to determine gains and losses when tuning.

Until someone engine dynos a 3.6 with full accessories and factory exhaust we will never know the true drivetrain loss.
And, throwing a JK on the dyno with 37" mud tires at 26psi is eating a tonne of power. Sit one on there with 26" tall fuel mileage designed tires and see what happens.
 

·
Registered
Joined
·
1,401 Posts
Gears are subject to constant angular acceleration even if the rpm is constant.
Say what? Constant angular acceleration would result in constantly increasing angular speed. Angular acceleration produces a change in angular speed. If RPM (angular speed) is constant, then angular acceleration MUST be zero.

And just like linear acceleration (which requires a force), angular acceleration requires an angular force (aka torque). Applying force requires energy, regardless of whether it is linear or angular. Energy is converted into angular motion when a torque is applied to an object with mass. This is angular acceleration.

If you cannot agree with this, then there lies your problem. You need to learn physics before you attempt to make sense of this drivetrain loss issue.


So, getting back to my 500k+ BTU's
No! That's just nonsense. Stop that! All conclusions you draw based on this incorrect assumption are complete nonsense.

A large amount of discrepency between acceleration sweep dyno test results and SAE net engine hp results is due to the amount of energy required to accelerate (angular) all of the drivetrain components: crankshaft, flywheel, transmission gears/shafts, transfer case gears/shafts/chains, driveshafts, etc., all the way to the wheels/tires themselves. These are all rotating components with mass and angular momentum (moment of inertia) that require torque to be accelerated. The more quickly they are accelerated, the more of the engines torque goes into accelerating the drivetrain components themselves.

Also, see the video of the dyno run in my previous post to see that there is quite significant acceleration involved in the type of dyno run that comes in about 33% lower than SAE net engine hp.


Furthermore, once you drop to your lower rate why don't you see an increase in power? It should happen. If accelerating hard caused me to dissipate 200hp into heat and constant operation caused it to say hover around a loss of 100hp.... Why don't these chassis dynos show a sharp spike upwards when they hold maximum peak HP throttle for any length of period?
Again, see the video in my previous post to see how these dyno runs work. It is a quick acceleration through the RPM range, so dyno charts from these types of runs would never show a "spike" in power as you suggest. They don't hold the engine at peak HP for any length of time at all. They are acceleration sweep dyno runs. See the theme here yet? Acceleration :)

A steady state dyno test WILL show higher results (less loss) because it completely removes the loss due to drivetrain inertia by settling into a steady state (no acceleration) before taking a measurement at each point through the rpm range.


...If we get .33% less using the above mentioned testing method we know we can directly correlate a relationship between drive train loss and 33% as a constant in the Jeep. If not we have to ask some questions about fundamental assumptions.
The 33% loss will not be constant. There are two major factors that will cause a difference:

1) The type of dyno. A different inertia dyno with a different type of drum (different moment of inertia) will cause the acceleration sweep to happen more quickly or slowly. Lower drum inertia -> faster acceleration sweep -> higher inertial loss due to accelerating the drivetrain. The amount of inertial drivetrain loss is a percentage based on the ratio of the drivetrain's total inertia to the dyno drum's inertia. Luckily, I believe DynoJet uses standard specs for their drums, so all inertial accelerations sweeps on any of DynoJet's dyno's should be safely comparable. Other brands may use different specs for their drums. Even more complicated, some dynos can be setup to simulate the load of the mass of the vehicle and the aerodynamic drag, and dynamically change the effective inertia of the drum throughout the acceleration sweep. This most accurately represents the power put down by the wheels while accelerating the vehicle in the real world, but requires accurate entry of the vehicle's mass and drag-area coefficient (CdA - this is not easy to obtain if not already experimentally determined and published by someone else). This is why you can't, for example, compare DynoJet results to Mustang Dyno results. They are both acceleration sweep tests, but with different drum specs and configurations.

2) Now let's reasonably assume that we'll use the same dyno, configured the same way, for our before/after dyno tests. There is still the smaller component of drivetrain loss due to friction. This will be a constant amount of torque (not hp!). After adding the turbo/supercharger and running on the same inertia dyno again, the inertial losses will scale up with the engine power gains, but the frictional losses will be the same as they were before. The end result is that the observed total drivetrain loss will be a slightly lower percentage of the crank hp.
 

·
Registered
Joined
·
615 Posts
Here is an example of a dyno run that RIPP performed. Take note of how quickly it accelerates through the RPM range. This is a typical style of dyno test that performance parts manufacturers and magazines use to create dyno charts and determine wheel HP: https://www.youtube.com/watch?v=87CkeT6WSg4
What the heck were they doing?
The rate at which that thing spun the barrel would make me believe there was 3500hp at work.
I'm no dyno expert, but that was the fastest barrel spin I've ever seen.
I'v
e been around plenty off high hp vehicles on the dyno, and none have ever spun the roller that quickly.
 
1 - 20 of 142 Posts
Top