Difference between HP and wheel HP

[Sub-Vibe-R]

I listen to a reporting on the Vibe.They tested a base Vibe, auto with ABS.Engine should be a 130 hpThey put the Vibe on dynamo and they got 85 hp to the wheelI know we can lost hp from flyweel to the wheel but as much as that, it is 35% lost.How can it be possible to lost so many hp?

[NovaResource]

A loss of 45-hp through the automatic is a little high in my opinion. 25-hp is a little more realistic (less for a manual). 100 to 105-hp at the wheels should be what you would see.

[d_m_kolb]

Average with manual is about 15-20% loss to wheelsAverage with auto is 20-25% to wheels. Some are as bad as 30%.

[NovaResource]

It's not a % it's an actual number. Think about it, the same automatic trans is used behind the 130-hp and 180-hp engines in the Matrix. If the trans uses 20% that means it uses 26-hp behind the 130-hp engine but then the same exact trans uses 36-hp behind the 180-hp engine. Tell my why the same trans would require more hp to drive with a higher hp engine? The truth is the auto uses about 25-hp behind both engines. It's not a %, it's an actual horsepower number. That number is the same no matter what hp engine it's attached to has.

[d_m_kolb]

It's all ways a % and it will never be the same % for every car or combination. The Vibe loses a certain % from the crank to the wheels. A manual will lose less that a auto do to the fact the manual doesn't slip through the gears like autos does.The engine makes the HP then it has to move through everything that connects the wheels to the engine. It has to over come the friction of this whole process.

[d_m_kolb]

They will both loose the same PERCENTAGE, so the higher HP engine will loose MORE HP.Assuming 15% drivetrain loss.100 HP ENGINE will dyno out about 85 to the wheels a 15 HP loss200 HP ENGINE will dyno out about 170 to the wheels, a 30 HP loss.It's still 15%, but you loose double the HP, by doubling the HP of the engine...That is why say an 900 HP dyno for a supra or skyline is so dramatic. Again, assuming a 15% drivetrain loss (which any supra/skyline owner would kill for) that means the engine is putting out 1035 HP. If you figure the 25% for the drivetrain loss, the engine is putting out 1125 HP.

[mu_ohio]

Friction is always linear or when you double the force of an object, the friction is also doubled. That being said, typically the loss of force (torque) is pretty much a constant non matter how much it is. You can test this by saying if a Vibe 5 spd always looses 25 hp, then when the engine is putting out 25 hp at 1000 rpms, then the car couldn't move. We know this is false since our car can move at less than 1000 rpms even when we aren't considering other forces against the car like rolling friction of the tires.

[NovaResource]

Your are totally wrong. Any given trans requires an amount of horsepower to run regardless of the engine it's attached to.If a 100-hp engine looses 15-hp with a trans then a 200-hp engine will also loose 15-hp with that same trans. Why would a given trans require more horsepower from one engine than another?

[d_m_kolb]

Nope that's not right. a 100HP engine with manual trany will adverage a 15% HP loss to the wheels. a 200 HP engine with manual trany will also adverage 15% Wheel HP loss. I have seen multiple dyno runs and charts that proof this.

[NovaResource]

The TH350 in my car uses about 40-hp to run behind my 330-hp 327. If I replace my 327 with a 660-hp engine you're telling me that the same exact trans is now gonna require 80-hp to run?Wrong.It's still gonna take about 40-hp. If I install a 100-hp engine, it's still gonna take about 40-hp to turn.
[Modified by NovaResource, 9:57 PM 9/15/2002]

[F1GT]

quote:The TH350 in my car uses about 40-hp to run behind my 330-hp 327. If I replace my 327 with a 660-hp engine you're telling me that the same exact trans is now gonna require 80-hp to run?Wrong.It's still gonna take about 40-hp. If I install a 100-hp engine, it's still gonna take about 40-hp to turn.[Modified by NovaResource, 9:57 PM 9/15/2002]I second this. You are absolutely correct. If a 100 hp engine loses 15 hp to the wheels, no matter what engine swap or power-adder, it will still lose 15 hp.

[mu_ohio]

quote:The TH350 in my car uses about 40-hp to run behind my 330-hp 327. If I replace my 327 with a 660-hp engine you're telling me that the same exact trans is now gonna require 80-hp to run?Wrong.It's still gonna take about 40-hp. If I install a 100-hp engine, it's still gonna take about 40-hp to turn.[Modified by NovaResource, 9:57 PM 9/15/2002]I second this. You are absolutely correct. If a 100 hp engine loses 15 hp to the wheels, no matter what engine swap or power-adder, it will still lose 15 hp.He isn't abosuletly correct. A transmission doesn't require power to run, rather it changes the form of the force. To really understand power, you really have to look at the force the engine is creating or lb/ft of torque. You transmission then turns the force into something that can be put to the wheels. With any conversion of a force from one form to another it will degrade. A transmission looses this force from a couple major things, namely HEAT, noise, and deflection. These are all cause by one major thing, FRICTION. Friction is constant even when the force increases. Meaning that the co-efficient of the friction in an engine will be a constant. Multiplying the co-efficient by the force you will notice that if you double the force, the loss will also double, ie:400 ft/lb * .15 = 60 ft/lb loss800 ft/lb * .15 = 120 ft/lb lossOk, now to the question of how it can loose more power, well lets take a look at what happens with high power cars. 1. Does the tranny get hotter and need a cooler? If you answer yes, then that's a cause for loss of power 2. Does the tranny get louder and maybe need better balancing? If you answer yes, then part of the power is lost to sound.3. Does your tranning slip when you add power? If you answer yes, then you are loosing power from the parts difflecting more.I'm sure the smarter ones can come up with more ways to loss power, but from those you can see that the tranny is not working the same at 400 lb/ft or 800 lb/ft torque. BTW, HP is the rate at with the force is being applied. A dyno doesn't measure HP, but rather torque on the drum. If anyone still disputes the fact then I will pull out as many physic references that I can find.

[NovaResource]

This is the problem with talking technical on a board with non-gearheads.quote:1. Does the tranny get hotter and need a cooler? If you answer yes, then that's a cause for loss of powerAdding power isn't what causes more heat in the trans. In an automatic trans it's the slippage in the torque converter. Yes, HP is a mathmatical number calculated from measured torque. As torque increases, a torque converter will slip more and generate more heat but that also depends on the loosness of the converter. If you have a tight converter, you won;t get alot of slip.quote:2. Does the tranny get louder and maybe need better balancing? If you answer yes, then part of the power is lost to sound.Power lost to sound?!? Proof you don't know what you're talking about.quote:3. Does your tranning slip when you add power? If you answer yes, then you are loosing power from the parts difflecting more.Parts difflecting? In an automatic, the slippage is in the converter like I mentioned above or in the bands slipping. If the bands are slipping then you have a bad trans and no good to base hp loss. In a manual, the only slipage is in the clutch. If it's slipping is a problem with the clutch, not the trans.quote:If anyone still disputes the fact then I will pull out as many physic references that I can find.You can quote all you want from your physics references, we don't race on paper and we don't dyno engines or paper either.

[mu_ohio]

I was going to type a reply out of emotion to you Nova, but I guess people are asses and this board just proved it. I hope that you aren't treated in the same mannor.BTW, making a statement like "Proof you don't know what you are talking about" is very lame when you make no attempt to PROVE why that statement is wrong.Thanks to most on this board and I'll miss coming here, but I really don't want to mingle with asses.

[d_m_kolb]

I'm actually really enjoying this post like I hope everyone else is to because I love to argue when I know I'm right. Nova Please be a little less brutal in your replys. I understand that's just how you are and I'm very glad you hang around here but some members probably newer one might take offense.Now back to the topic.You are too fixated on 40 HP. The other factor that comes in is TORQUE! Why do most people forget that torque is just as important as HP??Also, it's not just the tranny, there is power lost on the rear end, drive shaft, torque converter, wheels, and gravity. A friend of mine has a 350ci LS1 V8,in his 98 TA, if he were to upgrade it to a LS6 with about 400 HP, It would still lose about 15 percent from the crank to the wheels. The tranny doesn't take a certian amount of power to run, it is power that is lost in the the transfers of power from one mechanism to another. Power loss does grow with power input, but it's not really constant. You have said it takes 40HP to turn your trany with 330 HP but if your engine were to drop 4 cylinders and you were then only making half the normal HP you'd only be losing 20 HP through the trany. There are a few factors you're dealing with. There's dynamic friction--losses due to materials moving against each other which acts counter to the force applied. Yeah, sure there are bearings and all that but there is steel on steel contact, stuff is sliding at some point even if it is just the bearings against their housing. Friction is MULTIPLIED with FORCE using a friction coefficient, which you can multiply by the applied force to calculate the friction loss. It is usually a fairly linear relationship and is pretty constant with temperature for metals. In a transmission you could probably calculate an overall friction coefficient, it would depend heavily on the construction of the particular transmission though. But basically, this particular part can be thought of as a percentage.

[NovaResource]

quote:Thanks to most on this board and I'll miss coming here, but I really don't want to mingle with asses.What? Running home to your mommy? Bye.
[Modified by NovaResource, 9:08 AM 9/17/2002]

[NovaResource]

Yes, torque is what is actually measured and while there will be frictional losses due to increased torque, it's not linear. Hp losses will grow as hp (and torque) increase but it's not a direct 1 to 1 relationship. A trans that uses 35-hp with a 150-hp engine isn't going to use 70-hp behind a 300-hp engine. This is why a % number can't be assigned to a trans.

[mu_ohio]

quote:I'm actually really enjoying this post like I hope everyone else is to because I love to argue when I know I'm right. Nova Please be a little less brutal in your replys. I understand that's just how you are and I'm very glad you hang around here but some members probably newer one might take offense.Now back to the topic.You are too fixated on 40 HP. The other factor that comes in is TORQUE! Why do most people forget that torque is just as important as HP??Also, it's not just the tranny, there is power lost on the rear end, drive shaft, torque converter, wheels, and gravity. A friend of mine has a 350ci LS1 V8,in his 98 TA, if he were to upgrade it to a LS6 with about 400 HP, It would still lose about 15 percent from the crank to the wheels. The tranny doesn't take a certian amount of power to run, it is power that is lost in the the transfers of power from one mechanism to another. Power loss does grow with power input, but it's not really constant. You have said it takes 40HP to turn your trany with 330 HP but if your engine were to drop 4 cylinders and you were then only making half the normal HP you'd only be losing 20 HP through the trany. There are a few factors you're dealing with. There's dynamic friction--losses due to materials moving against each other which acts counter to the force applied. Yeah, sure there are bearings and all that but there is steel on steel contact, stuff is sliding at some point even if it is just the bearings against their housing. Friction is MULTIPLIED with FORCE using a friction coefficient, which you can multiply by the applied force to calculate the friction loss. It is usually a fairly linear relationship and is pretty constant with temperature for metals. In a transmission you could probably calculate an overall friction coefficient, it would depend heavily on the construction of the particular transmission though. But basically, this particular part can be thought of as a percentage.This was what I was trying to express in my posts. I was thinking last night about this topic and something came to mind. Many times when we talk about bolt-ons we state that yeah it may make x-hp at the crank but then we also state that the gain at the rear wheel is less by the same % that the tranny looses.

[d_m_kolb]

If I made a very inefficient driveline that lost a set amount of horsepower, say, 75 hp, and bolted it to a 150 hp motor, I would put down 75 hp to the ground. No arguments, right?Now, if I bolted that same driveline to a weaker version of the same motor, that made 70 hp, would I make negative horsepower?? No. Would it turn the driveline at all? Most likely. It wouldn't put EXACTLY 35 hp to the ground (50% loss like before), maybe 25 hp to 30 hp. That would account for the set hp losses and the percentage hp losses. Now I know that these numbers are not even close to real world examples, but they seem to get the message across.There are no TRUE rules or written in stone guidlines on drivetrain losses.In general 15% to 20% for manuals, and 20%-30% for automatics. In general FWD have less loss than RWD, but there are examples of really efficent RWD drivetrains, and examples of really poor FWD drivetrains...There is no set "power" to move a drivetrain. In reality, the power sapped by the drivetrain does not stay proportional with engine output. a 100HP engine that puts 85 HP to the wheels (15%) that does not mean that a 1000 HP engine would only put down 850 HP to the wheels (15%). In reality, the 1000 HP might put down 925 WHP. Who knows. There is a point of diminishing returns, where you have to beef up the transmission/gearset/workings to handle the high HP so that it actually RAISES the drivetrain losses in ultra high HP cars with weak factory components, but some cars which can use the basic stock factory drivetrain to insane HP levels might only have a 10 or 15% loss even for a RWD car.You would think that a transmission that saps 15 HP from a 100 HP engine would only sap that same 15 HP from a 1000 HP engine? Think about the physics of it man. There is 10 times the load on the transmission of the 1000 hp ENGINE. That does not directly translate into 10% more drag/ware/lost HP, but it does somewhat work against the HP gained in the engine, and what, in general keeps the drivetrain losses fairly consistent across HP levels using the same tranny.Lastly...there's no way to prove ANY of this unless you are willing to dyno with 2 seperate engines, and then dyno each engine on a engine dyno and compare the 2 results to determine drivetrain losses.

[d_m_kolb]

This is more info to prove my point.Click Here

[DABEAR95]

Hey guys, take a look at this link on the camaro forum. There are some serious folks posting on this site in this section. Some of you may have heard of Chuck Riddeck (sp?) http://web.camaross.com/forums/showthre ... train+loss JasonHere is an exerpt with some actual dyno numbers...-------------------------------------------Injuneer-As noted above..... drivetrain losses are NOT a straight percentage. That is just a number quoted for convenience of quick conversion of rear wheel HP to flywheel HP. There is both a "fixed" and a "variable" component of drivetrain loss.To keep it simple, think of driveline losses as consisting of two different components:Inertial:This is the energy required to bring the mass of the drivetrain to peak rotational speed. It is a "fixed" value. As long as the mass of the rotating parts doesn't change, and you bring them up to the same RPM, the energy absorbed is "fixed", and is not a function of the HP being transmitted.Frictional:Energy is lost to friction in bearings and gear surfaces. The friction loss is roughly proportional to the loads being transmitted. Double the torque and you double the forces acting on gear faces and bearings. So frictional losses are directly proportional to torque/HP.My data points for a 381 LT1 driving through a Street Twin, T56, 3" chrome moly driveshaft, 12-bolt 3.73's, and 17" wheels with 315 drag radials were:Motor: 425rwHP/486fwHP = 12.6% loss1-stage N2O: 555rwHP/633fwHP = 12.3% loss2-stage N2O: 670rwHP/762fwHP = 12.1% loss.When you consider that the 12-bolt is rated at about 7% loss, it accounts for a good portion of the losses. Bending the torque around a 90-degree corner exacts a price.When I converted to the TH400, the convertor slip (at least I think that's what it is - I know squat about auto trannies) became significant, increasing with the torque being transmitted:Motor: 390rwHP/486fwHP = 19.8% loss2-stage N2O: 600rwHP/762fwHP = 21.3% loss-----------------------------------------------------------------------

[QUIKAG]

I think DaBear has a winner!! So, both people are right. There is a fixed component and a variable component.

[Lorin]

I have really been enjoying this thread - it brings back fond memories of engineering school (GO PURDUE!). Engineers like to assign linear equations to things whenever possible to simplify calculations. But the reality of most things in nature is that the linear assumption is usually only valid for a limited range of parameters. This is one of the reasons calculus and other higher order math is taught in undergraduate engineering programs. The math permits more advanced research and applications.

[Stang2Vibe]

Wow. You talk about a real brain exercise. I've been scrambling my brains over this while reading the entire thread. I wonder how much brain power is lost through the thought process when using full concentration as opposed to the usual half which is typical when I am reviewing posts? Oh, Lord almighty, please don't bother trying to answer that one, we might start a full blown post war here!I was actually coming to a conclusion on my own before the answer was given. Neither side of the arguement was fully answering the question, so I knew there had to be something more to it. I know that there will be a set amount of force in the drivetrain that will have to be overcome regardless of the power output of the engine that is connected to it. This force is required to overcome the inertia of the parts and will be directly affected by their weight. But there is also the factor of the increased internal friction between the moving parts when increased force is applied to the system. This force will be variable and relative to the amount of force applied. Therefore, the answer that was given makes sense. 1.) There is a fixed inertial force that must be overcome to turn the drivetrain components and 2.) The amount of power needed to overcome the friction of the drivetrain will increase as the power applied increases, however this amount of increase will diminish as more and more power is put into the system. Ok, that makes sense, I can accept that.On a side note, diminishing returns was mentioned earlier in this thread and it was not used accurately. Diminishing returns is the idea that, at some point, as more and more resources, money, power, etc. are put into the equation, we net less and less gain from the addition. In many cases, diminishing returns will lead into negative returns where for each additional increment of input, we experience a negative growth in output. An example of a negative return in relation to engines would be if someone invented a new type of piston that could, through its design, increase hp output of the engine by 5 hp. But the new pistons are made of a very heavy metal alloy and take 8 hp away from the engine when it is running. Therefore, we have a net gain of -3 hp by adding these new pistons, meaning the addition of the parts makes us lose power instead of gaining it (negative growth).

[mu_ohio]

quote:Wow. You talk about a real brain exercise. I've been scrambling my brains over this while reading the entire thread. I wonder how much brain power is lost through the thought process when using full concentration as opposed to the usual half which is typical when I am reviewing posts? Oh, Lord almighty, please don't bother trying to answer that one, we might start a full blown post war here!I was actually coming to a conclusion on my own before the answer was given. Neither side of the arguement was fully answering the question, so I knew there had to be something more to it. I know that there will be a set amount of force in the drivetrain that will have to be overcome regardless of the power output of the engine that is connected to it. This force is required to overcome the inertia of the parts and will be directly affected by their weight. But there is also the factor of the increased internal friction between the moving parts when increased force is applied to the system. This force will be variable and relative to the amount of force applied. Therefore, the answer that was given makes sense. 1.) There is a fixed inertial force that must be overcome to turn the drivetrain components and 2.) The amount of power needed to overcome the friction of the drivetrain will increase as the power applied increases, however this amount of increase will diminish as more and more power is put into the system. Ok, that makes sense, I can accept that.On a side note, diminishing returns was mentioned earlier in this thread and it was not used accurately. Diminishing returns is the idea that, at some point, as more and more resources, money, power, etc. are put into the equation, we net less and less gain from the addition. In many cases, diminishing returns will lead into negative returns where for each additional increment of input, we experience a negative growth in output. An example of a negative return in relation to engines would be if someone invented a new type of piston that could, through its design, increase hp output of the engine by 5 hp. But the new pistons are made of a very heavy metal alloy and take 8 hp away from the engine when it is running. Therefore, we have a net gain of -3 hp by adding these new pistons, meaning the addition of the parts makes us lose power instead of gaining it (negative growth).I think that the answer you came up with could be modified a little. Two things that need to be considered. As ther percentage lost decreases, so does the ability of the transmission to accept the power. For example, if you jump from 100hp to 200hp, you might see a decrease in the transmission loss percentage. At a certain point though, the percent lost will approach 100%. This would occur say if you add 1000 hp because you overcame close to 100% of the fiction in the transmission. I know that people would not be stupid enough to try something like that, but you have to put limits on the min and max power of the tranny. The lower would be the amount need to overcome inertia, and the upper would be the point at which the tranny could no longer convert the engergy. Second, the power need to move the object is eliminated from the equation once the parts are in motion unless it accelerates.. If you remember, a object at rest will remain at rest unless acted upon by an outside force. An object in motion will remain in motion unless accted upon. The transmission will only require a force to accelerate it which should be linear. From that we can say that to keep the tranny going at a certain speed, it will need just enough power to cancel the effects of friction. To accelerate the tranny, we will need the force to increase inertia plus cancel the effects of friction. My point was, that if a transmission can only hold a certain range of power, you won't see a large change in the loss of power especially in a low power engine. Now if we are talking 1000-2000hp, then I fully agree that you will see a good decrease in percentage lost to friction.BTW, diminishing returns is always a factor of a return where the application of additional resource yields less than proportional increase in output.

[Stang2Vibe]

Yes, you've pretty much said what I was thinking.The min is the smallest amount of power needed to overcome the inertia of the drivetrain's moving parts. The max would be the highest power rating the tranny is designed to accept. Therefore, as you have stated, we could never reach these high numbers because our tranny's couldn't handle that much power anyway.quote:the upper would be the point at which the tranny could no longer convert the engergyFor this, read "tranny blows up".

[XRSizzler]

To answer the original posters question, there may be a difference in how he measured the wheel hp. Mustang dynos typically measure 10-15% less then DynoJet dynomameters, hence the 85whp instead of 100-105whp. He didn't state what kind of dyno he used. Or if it was corrected to STP.Mo

[andrewmva]

quote:Nope that's not right. a 100HP engine with manual trany will adverage a 15% HP loss to the wheels. a 200 HP engine with manual trany will also adverage 15% Wheel HP loss. I have seen multiple dyno runs and charts that proof this.You are absolutely 1000% correct... I'm at the dyno everyother day. the clutch and tranny have a MAJOR impact on that figure...we running 1200+hp and trust me a $10,000 tranny and an $4,000 clutch don't loose as much power.