AlpineFunco
Well-known member
- May 5, 2021
- 599
- 723
Gen 4 Funco upgrade or new car
- Thread starter onanysunday
- Start date
FOG
Well-known member
- May 11, 2021
- 1,643
- 1,854
I understand what you’re saying about the heat losses, etc. and now think it’s not just a constant. But instead a constant and variables. Where the variables are dependent upon the amount of horsepower being applied.
I don’t know if there’s a formula that can be used to calculate what the OP wants, but I don’t think you can just use a straight percentage either.
John@Outfront
Forum Moderator
- Apr 30, 2021
- 1,346
- 1,801
i agree a percentage might no be 100% correct but i believe its close but the bottom line is it really doesnt matter. what we do know is that the engine's hp never changed.
i have seen brake being slightly applied on my dyno and a loss of 50+ hp because of it and thats only being slightly applied! RWHP is on part of the fun factor anyways, weight and hook up are some others.
HTElectrical
Active member
- May 6, 2021
- 238
- 86
Where’d My Horsepower Go? Drivetrain Power Loss & The 15% "Rule"
Can you apply a universal power loss percentage to all drivetrains?
Mar 9, 2020
Updated March 2020 - Drivetrain power loss is a common topic of conversation in the tuner world because any time you strap your car to a chassis dyno, the output being measured is at the wheel, not at the crankshaft or flywheel like the published SAE net horsepower figures used by the auto industry. Strap your 298hp Rev-Up G35 Coupe to the dyno and you may be disappointed to see little more than 220 to 230 horses measured at the rear wheels. Where did that 60-plus horsepower go? It was used up in a variety of ways before it could reach the drive wheels, the primary source being what's broadly described as drivetrain loss.
What's interesting about this example is that when you do the math, you'll see the percent loss is much higher than the 15 percent "rule" you'll find in any number of online threads on the subject. For whatever reason, drivetrain loss seems to be one of the most poorly understood subjects discussed online, so despite my love of the Internet and the limitless pornography it makes available to me, when it comes to a fairly technical subject like this it's hard to find good information.
SAE: Setting the Standard
Years ago, I needed to educate myself on drivetrain losses while heading a rulebook committee for a local racing series that wanted to use dyno tests to measure engine output and then convert the results to net horsepower. After fruitlessly Googling and sifting through endless threads polluted with half-truths and misinformation, I turned to the same source that developed the current manufacturer horsepower standard, SAE International (formerly known as the Society of Automotive Engineers). On its website you can access brief summaries of technical papers published by some of the world's leading automotive engineers.
One of the first things I learned from reading these papers was to completely disregard the 15 percent drivetrain loss "rule" (or any other percent value) that so often comes up during online discussions of rated versus net horsepower. The fact of the matter is every vehicle experiences different levels of drivetrain loss as determined by the design of its transmission and driveline components. Simply put, the amount of horsepower lost to the forces of inertia, drag, windage, pumping and friction are different for every engine, transmission and driveline design.
How Stuff Works
Everything You Need to Know About the Toyota 2JZ-GTE Engine
Everything You Need to Know About the Nissan SR20DET Engine
So the total power lost between combustion and forward motion is specific to each vehicle and therefore no single rule, percentage, or fixed number could possibly apply to all vehicles. Even on the most superficial level, this is easy enough to understand because an all-wheel-drive Subaru obviously has a lot more driveline components to spin (front, middle and rear differentials along with front and rear driveshafts and two prop shafts) and a beefier transmission to hold all that turbocharged torque, so it's naturally going to suffer from greater drivetrain losses than a Honda Fit with its much smaller and less robust transmission, smaller and lighter driveshafts (and no prop shaft) and single differential.
Types of Power Loss
Breaking down the different types of losses that occur within a vehicle's drivetrain, steady-state losses occur while the vehicle is cruising at a steady or constant speed, where average angular acceleration is zero because no additional torque is being called upon to accelerate the drivetrain's rotational mass. Within the drivetrain, steady-state power losses occur from the following components: the transmission torque converter (in the case of automatic transmissions), the transmission oil pump, clutch pack drag, one-way clutch drag, seal and bearing drag, gear windage and friction, and final drive losses.
Dynamic drivetrain losses, on the other hand, include the rotational inertial losses from angular acceleration occurring within the drivetrain while accelerating. In fact, during acceleration there are losses from the rotational inertia of spinning transmission and differential internals as well as driveline components like driveshafts and prop shafts, but also from the increased load and friction being generated between the gears within the transmission and differential(s). With increased friction comes increased heat (more on that later)
It's important to understand the difference between steady-state and dynamic losses because SAE net horsepower, as reported by the auto industry, is measured in a steady-state condition. What this means is that the horsepower rating for your vehicle doesn't take into account dynamic losses that occur during acceleration. However, when you strap your car to a chassis dyno to measure its engine's output, the test is conducted at wide-open throttle and power is measured by the speed at which the dyno's rollers are accelerated. This means that drivetrain losses from rotational inertia and increasing friction, drag and windage are at work and will reduce the peak horsepower reading at the wheels.
What's Robbing Horsepower
Within the drivetrain itself, the primary loss sources are the differential and final drive, with further losses stemming from within the transmission, and in the case of AWD vehicles, from the transfer case. Within the transmission, as much as 30 to 40 percent of power loss can be attributed to the pump, with the clutch contributing another 20 to 25 percent. The rest of the loss within the transmission comes from seal drag, gear meshing, bearings, bushings and windage (drag on the gears caused by the gear oil). However, when dyno testing in the direct drive (1:1) gear, power is delivered directly through the main shaft of the transmission, so the only loss sources are windage, friction and drag, resulting in total at-the-wheel losses as low as 1.5 to 2 percent, according to published SAE data.
AWD systems like this R35 Nissan GT-R's provide tremendous traction but suffer from higher drivetrain losses than FWD or RWD systems.
Differential losses tend to be considerably larger, especially in the case of RWD and AWD vehicles where the torque path is turned 90 degrees as it enters the rear diff and exits it toward the rear wheels. In the case of hypoid-type gearsets (where the gear tooth profile is both curved and oblique) that are commonly used in RWD differentials, losses in the 6 to 10 percent range are the norm, while loss from the driveshaft(s) and prop shaft(s) tend to account for about 0.5 to 1 percent of total loss, depending on how well they're balanced and how many the vehicle is equipped with. In the case of FWD vehicles, the torque path is more direct to the front wheels and the use of efficient helical final drive gears means that drivetrain losses can be as much as 50 percent lower than on RWD and AWD vehicles.
In any drivetrain component with meshing gearsets, heat generated by contact friction between the gears is a significant contributor to drivetrain loss. This is true during steady-state driving, but is far more of an issue when the throttle is mashed to the floor and the resulting thrust force and angular acceleration builds up in these drivetrain components. The heat generated by this dynamic friction is absorbed by the transmission and differential fluid as well as radiated to the atmosphere through the transmission and differential housing(s), and in some cases, via a heat exchanger or oil cooler. This absorbed and radiated heat is literally the conversion of engine torque into thermal energy because you can't technically "lose" power but can only convert it into other things (some of our favorites being forward motion and tire smoke).
This simple illustration highlights (yellow outline) some of the major sources of drivetrain loss.
It's also worth noting that the more powerful you make your engine, the greater the thrust force and angular acceleration it's able to exert on the drivetrain, generating even more friction and heat in the process. But because both steady-state and dynamic friction vary depending on engine speed, engine load and the efficiency of the engine and drivetrain's design (how well they limit friction and the associated thermal conversion of torque to heat), there's no way to apply a universal percent loss to it. Nor is it possible to apply a fixed drivetrain loss figure to your car (say 60 whp from my Rev-Up G35 example), because as you modify the engine and increase its output its ability to generate thrust force and angular acceleration also increases (though not in a linear fashion).
No Rule is Universal
In the end, there's no easy way to estimate the drivetrain loss your vehicle experiences on the road or even on the dyno. Coast-down tests are sometimes used on a dyno to attempt to measure frictional losses, but because this test is not dynamic (meaning they're not done while accelerating, but rather while coasting to a stop with the direct drive gear engaged but the clutch depressed so that the engine and transmission aren't linked) it really only captures steady-state drivetrain losses as well as rolling resistance. So rather than attempting to convert your vehicle's dyno-measured wheel horsepower to a SAE net horsepower figure using a percentage or a fixed horsepower value, you're far better off accepting the fact that these two types of horsepower measurements aren't easily correlated and forego any attempt at doing so.
Can you apply a universal power loss percentage to all drivetrains?
Mar 9, 2020
Updated March 2020 - Drivetrain power loss is a common topic of conversation in the tuner world because any time you strap your car to a chassis dyno, the output being measured is at the wheel, not at the crankshaft or flywheel like the published SAE net horsepower figures used by the auto industry. Strap your 298hp Rev-Up G35 Coupe to the dyno and you may be disappointed to see little more than 220 to 230 horses measured at the rear wheels. Where did that 60-plus horsepower go? It was used up in a variety of ways before it could reach the drive wheels, the primary source being what's broadly described as drivetrain loss.
What's interesting about this example is that when you do the math, you'll see the percent loss is much higher than the 15 percent "rule" you'll find in any number of online threads on the subject. For whatever reason, drivetrain loss seems to be one of the most poorly understood subjects discussed online, so despite my love of the Internet and the limitless pornography it makes available to me, when it comes to a fairly technical subject like this it's hard to find good information.
SAE: Setting the Standard
Years ago, I needed to educate myself on drivetrain losses while heading a rulebook committee for a local racing series that wanted to use dyno tests to measure engine output and then convert the results to net horsepower. After fruitlessly Googling and sifting through endless threads polluted with half-truths and misinformation, I turned to the same source that developed the current manufacturer horsepower standard, SAE International (formerly known as the Society of Automotive Engineers). On its website you can access brief summaries of technical papers published by some of the world's leading automotive engineers.
One of the first things I learned from reading these papers was to completely disregard the 15 percent drivetrain loss "rule" (or any other percent value) that so often comes up during online discussions of rated versus net horsepower. The fact of the matter is every vehicle experiences different levels of drivetrain loss as determined by the design of its transmission and driveline components. Simply put, the amount of horsepower lost to the forces of inertia, drag, windage, pumping and friction are different for every engine, transmission and driveline design.
How Stuff Works
Everything You Need to Know About the Toyota 2JZ-GTE Engine
Everything You Need to Know About the Nissan SR20DET Engine
So the total power lost between combustion and forward motion is specific to each vehicle and therefore no single rule, percentage, or fixed number could possibly apply to all vehicles. Even on the most superficial level, this is easy enough to understand because an all-wheel-drive Subaru obviously has a lot more driveline components to spin (front, middle and rear differentials along with front and rear driveshafts and two prop shafts) and a beefier transmission to hold all that turbocharged torque, so it's naturally going to suffer from greater drivetrain losses than a Honda Fit with its much smaller and less robust transmission, smaller and lighter driveshafts (and no prop shaft) and single differential.
Types of Power Loss
Breaking down the different types of losses that occur within a vehicle's drivetrain, steady-state losses occur while the vehicle is cruising at a steady or constant speed, where average angular acceleration is zero because no additional torque is being called upon to accelerate the drivetrain's rotational mass. Within the drivetrain, steady-state power losses occur from the following components: the transmission torque converter (in the case of automatic transmissions), the transmission oil pump, clutch pack drag, one-way clutch drag, seal and bearing drag, gear windage and friction, and final drive losses.
Dynamic drivetrain losses, on the other hand, include the rotational inertial losses from angular acceleration occurring within the drivetrain while accelerating. In fact, during acceleration there are losses from the rotational inertia of spinning transmission and differential internals as well as driveline components like driveshafts and prop shafts, but also from the increased load and friction being generated between the gears within the transmission and differential(s). With increased friction comes increased heat (more on that later)
It's important to understand the difference between steady-state and dynamic losses because SAE net horsepower, as reported by the auto industry, is measured in a steady-state condition. What this means is that the horsepower rating for your vehicle doesn't take into account dynamic losses that occur during acceleration. However, when you strap your car to a chassis dyno to measure its engine's output, the test is conducted at wide-open throttle and power is measured by the speed at which the dyno's rollers are accelerated. This means that drivetrain losses from rotational inertia and increasing friction, drag and windage are at work and will reduce the peak horsepower reading at the wheels.
What's Robbing Horsepower
Within the drivetrain itself, the primary loss sources are the differential and final drive, with further losses stemming from within the transmission, and in the case of AWD vehicles, from the transfer case. Within the transmission, as much as 30 to 40 percent of power loss can be attributed to the pump, with the clutch contributing another 20 to 25 percent. The rest of the loss within the transmission comes from seal drag, gear meshing, bearings, bushings and windage (drag on the gears caused by the gear oil). However, when dyno testing in the direct drive (1:1) gear, power is delivered directly through the main shaft of the transmission, so the only loss sources are windage, friction and drag, resulting in total at-the-wheel losses as low as 1.5 to 2 percent, according to published SAE data.
AWD systems like this R35 Nissan GT-R's provide tremendous traction but suffer from higher drivetrain losses than FWD or RWD systems.
Differential losses tend to be considerably larger, especially in the case of RWD and AWD vehicles where the torque path is turned 90 degrees as it enters the rear diff and exits it toward the rear wheels. In the case of hypoid-type gearsets (where the gear tooth profile is both curved and oblique) that are commonly used in RWD differentials, losses in the 6 to 10 percent range are the norm, while loss from the driveshaft(s) and prop shaft(s) tend to account for about 0.5 to 1 percent of total loss, depending on how well they're balanced and how many the vehicle is equipped with. In the case of FWD vehicles, the torque path is more direct to the front wheels and the use of efficient helical final drive gears means that drivetrain losses can be as much as 50 percent lower than on RWD and AWD vehicles.
In any drivetrain component with meshing gearsets, heat generated by contact friction between the gears is a significant contributor to drivetrain loss. This is true during steady-state driving, but is far more of an issue when the throttle is mashed to the floor and the resulting thrust force and angular acceleration builds up in these drivetrain components. The heat generated by this dynamic friction is absorbed by the transmission and differential fluid as well as radiated to the atmosphere through the transmission and differential housing(s), and in some cases, via a heat exchanger or oil cooler. This absorbed and radiated heat is literally the conversion of engine torque into thermal energy because you can't technically "lose" power but can only convert it into other things (some of our favorites being forward motion and tire smoke).
This simple illustration highlights (yellow outline) some of the major sources of drivetrain loss.
It's also worth noting that the more powerful you make your engine, the greater the thrust force and angular acceleration it's able to exert on the drivetrain, generating even more friction and heat in the process. But because both steady-state and dynamic friction vary depending on engine speed, engine load and the efficiency of the engine and drivetrain's design (how well they limit friction and the associated thermal conversion of torque to heat), there's no way to apply a universal percent loss to it. Nor is it possible to apply a fixed drivetrain loss figure to your car (say 60 whp from my Rev-Up G35 example), because as you modify the engine and increase its output its ability to generate thrust force and angular acceleration also increases (though not in a linear fashion).
No Rule is Universal
In the end, there's no easy way to estimate the drivetrain loss your vehicle experiences on the road or even on the dyno. Coast-down tests are sometimes used on a dyno to attempt to measure frictional losses, but because this test is not dynamic (meaning they're not done while accelerating, but rather while coasting to a stop with the direct drive gear engaged but the clutch depressed so that the engine and transmission aren't linked) it really only captures steady-state drivetrain losses as well as rolling resistance. So rather than attempting to convert your vehicle's dyno-measured wheel horsepower to a SAE net horsepower figure using a percentage or a fixed horsepower value, you're far better off accepting the fact that these two types of horsepower measurements aren't easily correlated and forego any attempt at doing so.
Last edited by a moderator:
FOG
Well-known member
- May 11, 2021
- 1,643
- 1,854
dbart
Well-known member
- May 5, 2021
- 2,571
- 3,128
Without reading every response here, I would say....
UPGRADE.....................to a NEW car.
:lmao:
It's a lot of fun spending other people's money!
:bag:
:dbart:
UPGRADE.....................to a NEW car.
:lmao:
It's a lot of fun spending other people's money!
:bag:
:dbart:
John@Outfront
Forum Moderator
- Apr 30, 2021
- 1,346
- 1,801
I agree. Great article and echos that there are many factors in the equation. Therefore the RWHP numbers everyone claims is just bragging rights that don’t amount to anything. An LS motor that puts out 400 wheel Hp in a 2600 LB car is not even a match to a lighter car with a subaru putting out 400 wheel. Not even in the same ball park.
great discussion!!
all I know is that 425 rwhp in a 2200 LB car gets it on!
I have said it many times that I feel that every 100# in a car is probably worth 50 hp. Or in other words if you lose 100 lbs then you could have 50!hp less and feel the same. A 2800 car would need to add 300 engine hp to the mix compared to a 2200 car. I know that’s not science but it’s my opinion
great discussion!!
all I know is that 425 rwhp in a 2200 LB car gets it on!
I have said it many times that I feel that every 100# in a car is probably worth 50 hp. Or in other words if you lose 100 lbs then you could have 50!hp less and feel the same. A 2800 car would need to add 300 engine hp to the mix compared to a 2200 car. I know that’s not science but it’s my opinion
- Thread starter
- #48
onanysunday
Well-known member
- May 7, 2021
- 3,215
- 2,963
So roughly 3 to 4 years ago they took E85 away from us at the pump. It had usually tested around 80%. Then we had flex fuel 50/50 which I have been running and tuned on. The last two times my Chevron has not had flex at Lake Pleasant PKWY and I have gone to 91st Ave and Olive. They are now carrying only E85 at the pump. Both times it has tested just over 80%. Call it 81-82. I asked her today if this is always going to be available. She said yes. I have been doing 3.6 gallons of E85 and 1.9 gallons of 91 gas for a 50% mix. With the retune it would be easy to go back. Easier to make more power. Down side is stoich drops from approx. 11 to 1 down to 9 to 1. (IIRC). So worse mileage. Right now I get 3mpg and bring 70-75 gallons for each trip. IIRC Before on E85 I was getting 2.6 mpg. Making more power thinking I would be somewhere in the 2.5 range. I added the 5 gallon tank with transfer pump so 20 gallons total. Right now the car will go approx. 55 miles which we do sometimes on a ride. Range would drop to approx. 40 miles maybe a little more. With 2-3 gallons left it starts laying over in the turns. This means bringing 80-85 gallons for each trip. Hard decision which way to go. Yes I am a horsepower junkie.
- Thread starter
- #50
onanysunday
Well-known member
- May 7, 2021
- 3,215
- 2,963
Talking to our tuner at the shop the mileage takes a pretty good hit but power is not a huge difference between 50% and 80%. I think we will give it a squeeze with 50.
Rockwood
Well-known member
- May 5, 2021
- 4,814
- 6,117
True...
However, the increased heat load will accelerate @onanysunday off the top of the next dune quicker, so he will spend less time heating it (at a higher temperature). In the end, and this is pedantry at its finest, the intercooler should be sized to the load, not the boost.
Flow will be a factor though. If pressure loss is high because the core won't flow the power, heat rejection is significantly worse.
Was gonna say: I think that VQ will make all but crazy LS power. You'll have less tractability, but if your complaint is just power and not low RPM response, throw more boost at it.
As the article posted after this states, there are lots of losses in a drivetrain. Inertial loss (and even then, the quicker you accelerate it, the larger the losses and it doesn't scale linearly) is just a part of the equation. The more power you send through a transmission, the more the gear faces are shoved against each other, the more friction loss there is (coefficient of friction vs just friction), this scales linearly, so a simple percentage is accurate for just this part of the equation.
Inertial loss is part of why you see less power readings in lower gear ratios on a dyno, or you "gain" more power in lower gears with lighter pullies or flywheel or wheels. Frictional losses are part of why you see less power per additional pound of boost (assuming efficiency isn't out of the sweet spot).
HP.Habits
Active member
- Jul 16, 2021
- 159
- 147
following, Some great discussion on here.
Kraut_n_Rice
Site Sponsor
- May 9, 2021
- 2,510
- 1,949
You think he's gonna lift sooner? He's after more. LOL
The VQ that he has built will take a ton of power, but it's complicated and heavy. If you want to make "easy", "cheap" bigger power there really is only one answer. He could make more HP with less weight if he ditched the VQ and went LS. The cheaper solution for him currently is obviously more boost.
Yes, a Honda guy knows the limitations of a platform. But, if you want to be different and swing for the fence, go for it. I'll watch! I currently have the stuff to rod and stud a J35a4 and a J37a1. Just need to find pistons and pick one to build.
Rockwood
Well-known member
- May 5, 2021
- 4,814
- 6,117
Dune is only so tall. More power means he gets to the top sooner. :biggrin:
VQ35 is a pretty light engine, not J light, but definitely lighter than an LS, especially one making 5-600whp like the VQ he has built. Sure, LS will make more power, but how much more than 600whp can you really put into a Gen 4 before it becomes completely ridiculous? :biggrin:
Last edited by a moderator:
- Thread starter
- #55
onanysunday
Well-known member
- May 7, 2021
- 3,215
- 2,963
This thing was only showing 7 lb of boost on my gauge and I was thinking the gauge had an issue. Put the new hoonigan gauge on there and it's still showing 7 PSI. That is the spring and then we were using the boost controller to hold the wastegate shut to make more boost. So we originally Dynoed this thing at 12 lb of boost. Obviously the boost controller isn't working. Car still hauls ass at 7 lb. Should be really fun if we crank it way up.
- Apr 29, 2021
- 2,229
- 3,247
Start playing in the 14+ boost range on a light weight engine. It's night and day.
- Thread starter
- #57
onanysunday
Well-known member
- May 7, 2021
- 3,215
- 2,963
Next phase before dyno. Remove the Camco Fab muffler after 17 years so there is no restriction. Install a bung for an O2 sensor. Car has been running without one for years. If I continue to be happy with this car in the next year or two I might tear it down for a complete powder. What a job that would be.
John@Outfront
Forum Moderator
- Apr 30, 2021
- 1,346
- 1,801
is that a 3.0? that looks like a big turbo for that.........
richard h
Well-known member
- May 5, 2021
- 1,406
- 1,262
It is, just putting mine back together now. The nice part is getting to finally make all the finishing touches just like you want. The hardest part of the job is the thinking about it before you start.
John@Outfront
Forum Moderator
- Apr 30, 2021
- 1,346
- 1,801
have sat and thought about the best, cleanest way to do things a lot on my own car, like lots of hours and the more you think, the cleaner it gets, but whos going to pay for that right?