Avg. HP loss through Drivetrain?
The link explains it better than i could. Basically it says, say your engine makes 400hp. You dyno it (or acclerate it). It takes 30 seconds to spin the dyno drums up to max rpm, or to acclerate the car to 140mph. Now you put an 800hp engine in with the same drivetrain. You acclerate the drums in 18seconds now or accelerate to 140 in that time. You are now having to acclerate at a faster rate.
All fluid robs energy. Every tooth on a gear creates friction. This robs energy. The faster you accelerate the hotter it gets. Heat is energy. Think about it like this. If you have a swimming pool. Stick a skimmer net in there on a pole (the thing you use to get the leaves out). Move it with a constant force against the water, see how much the pole bends. Say the pole bends 2" over 8 foot. Say you put about 20lb of force on that pole when moving the net through the water. Now put 40lbs of pressure on the pole thus moving the pole faster through the water. This WILL bend the pole more as it takes MORE force to accelerate faster through a fluid. The pole will also bend say 4" in 8 foot. It will not only bend 2" though.
The exact same principle applies to every fluid carying piece in your driveline like your rear end, your transmission. The u-joints rob power, even the bearings and the axels.
All fluid robs energy. Every tooth on a gear creates friction. This robs energy. The faster you accelerate the hotter it gets. Heat is energy. Think about it like this. If you have a swimming pool. Stick a skimmer net in there on a pole (the thing you use to get the leaves out). Move it with a constant force against the water, see how much the pole bends. Say the pole bends 2" over 8 foot. Say you put about 20lb of force on that pole when moving the net through the water. Now put 40lbs of pressure on the pole thus moving the pole faster through the water. This WILL bend the pole more as it takes MORE force to accelerate faster through a fluid. The pole will also bend say 4" in 8 foot. It will not only bend 2" though.
The exact same principle applies to every fluid carying piece in your driveline like your rear end, your transmission. The u-joints rob power, even the bearings and the axels.
Last edited by Shawn MacAnanny; Nov 26, 2008 at 04:38 PM.
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Could not have said it better.....
It is one of the things that is overlooked by most builders. We have had cars that make less power at the crankshaft than others and still manage to win. In a restricted rules class you try to free up all that drag or driveline loss. It's horsepower no matter how you look at it. Once we are at the limit of the combination we find ways to reduce the loss.
We removed the 5th gear in our trans, any weight reduction reduces the power needed to accelerate. Aluminum pressure ring clutches, Aluminum flywheels. Micro Polished trans and rear axle gears. Aluminum driveshaft.
We would run wheels with a 3" backspace so we could narrow the housing an additional 3" each side. Trust me it all adds up.
Also because we raced and maintain our stuff we would run less pre load in the pinion and in the trans. It hurts longevity and strength but that is racing.
The last time we ran at the dyno then installed the engine in the car the loss at the wheels was 8%.
It made over 600 horsepower at the crank so that was 24 horsepower that we had freed up.
Robin
It is one of the things that is overlooked by most builders. We have had cars that make less power at the crankshaft than others and still manage to win. In a restricted rules class you try to free up all that drag or driveline loss. It's horsepower no matter how you look at it. Once we are at the limit of the combination we find ways to reduce the loss.
We removed the 5th gear in our trans, any weight reduction reduces the power needed to accelerate. Aluminum pressure ring clutches, Aluminum flywheels. Micro Polished trans and rear axle gears. Aluminum driveshaft.
We would run wheels with a 3" backspace so we could narrow the housing an additional 3" each side. Trust me it all adds up.
Also because we raced and maintain our stuff we would run less pre load in the pinion and in the trans. It hurts longevity and strength but that is racing.
The last time we ran at the dyno then installed the engine in the car the loss at the wheels was 8%.
It made over 600 horsepower at the crank so that was 24 horsepower that we had freed up.
Robin
I was at 430rwhp through my six speed. I'll let you know in a couple of weeks what it ends up being through a stalled TH400. It will most likely be in the high 300's to low 400's, but I'll go a lot faster at the track.
That link has some good info on it for sure.
Going by what he was saying answer this for me...
Say you have a 383 that makes 450 HP at 7,500 RPM and you also have a 454 that makes 525 HP at 6,000 RPM. You put both engines in a car with the same drive train, witch one will be robbed of more power?
The 383 is twisting more RPM, therefore more friction and more fluid passing over the gears. so with what he was saying, in this case the lesser power engine would be robbed of more power.
Another thing, you said that every drive line part has an "efficiency" Well, once that part reaches it's point of efficiency wouldn't it stop robbing anymore power?
Going by what he was saying answer this for me...
Say you have a 383 that makes 450 HP at 7,500 RPM and you also have a 454 that makes 525 HP at 6,000 RPM. You put both engines in a car with the same drive train, witch one will be robbed of more power?
The 383 is twisting more RPM, therefore more friction and more fluid passing over the gears. so with what he was saying, in this case the lesser power engine would be robbed of more power.
Another thing, you said that every drive line part has an "efficiency" Well, once that part reaches it's point of efficiency wouldn't it stop robbing anymore power?
Baked, you are incorrect, but only about 99%. Each part does not rob a fixed amount of power, i.e. it does not take a fixed amount of HP to turn a certain part. Remember that torque x rpm / 5252 = hp. In most drivelines you are changing rotational directions more than once, plus fluid losses, plus thermal losses, plus gearing losses (yes, these are offset by the add'l leverage). Add a slipping clutch/non-locked converter and you lose more. The formula is VERY complex but it is close enough to consider it a fixed percentage and indeed the measured loss goes up as the engine power goes up, both HP and torque. The losses will be slightly higher at higher RPMs due to the formula above, but only slightly. In stock driveline f-bodies, 15% on manuals and 18% on autos gets damn close. Anything you do from there changes things. It's hard to improve that except with light driveshafts, clutches, wheels, and flywheels. Everything else reduces efficiency, but increases other things like leverage or longevity. It's all about what you are after. If you are a manual, you'll be closer to 15%, autos closer to 20% loss. Some of your big *** stalled autos, heavy rears, tall geared, fat tired jobbies can lose well over 20% but the trade off of leverage and/or longevity is worth it to drag racers. Only way to know for sure is to engine dyno, then chassis dyno the same day. Even then you'll get variations from different chassis dynos. Short of learning 2-4 years of physics in one post, you are safe taking the words of those who have been there for years doing this.
Good/bad converters can do a lot. The converter that was in my 4L80E was hungry no doubt. Here are some numbers to scratch your head with..
My old 347ci motor 449rwhp locked / 402rwhp unlocked 8.95%
My new 418ci motor 521rwhp locked / 469rwhp unlocked 9.00%
What about the trans itself and the drum inside. Also the rear.. A lot comes in to play..
My old 347ci motor 449rwhp locked / 402rwhp unlocked 8.95%
My new 418ci motor 521rwhp locked / 469rwhp unlocked 9.00%
What about the trans itself and the drum inside. Also the rear.. A lot comes in to play..
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Yes that is what i am saying. Every part in your drivetrain has an 'efficiency'. The 9" rear end is less efficient due to the lower pinion and heavier rotating mass. It will rob MORE power the MORE horsepower your engine makes. For instance look at engines that flywheel dyno 1000hp. They only put around 800 or so to the wheels. Its always a percentage loss. Never a set ammount.
Even the engine performance is based on a volumentric efficiency which is a percentage. For instance a gen 1 sbc displaces 350 cu.in. Even with the most advance EFI system that could be run on them it still could never match the LS1 (at 346cu.in) for fuel mileage. It's a more efficient design. It's the same displacement moving the same air in a more efficient way. Efficiency is only ever measured as a percentage. The drivetrain has a negative PERCENTAGE loss of efficiency.
Even the engine performance is based on a volumentric efficiency which is a percentage. For instance a gen 1 sbc displaces 350 cu.in. Even with the most advance EFI system that could be run on them it still could never match the LS1 (at 346cu.in) for fuel mileage. It's a more efficient design. It's the same displacement moving the same air in a more efficient way. Efficiency is only ever measured as a percentage. The drivetrain has a negative PERCENTAGE loss of efficiency.
Last edited by Ls1talk; Mar 30, 2021 at 10:01 PM.
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Think of it like this if you shoot a 50 cal into a pool of water it will explode on impact.you shoot into the same pool of water with a 22 caliber it will go deeper because it has less power meaning less friction that sounds crazy but actually a fact sound silly but friction is complicated lol took a while for me to understand it also just a different way to understand the concept even though it's off subject.
Don't you check post dates???
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On Parasitic power loss Here's some suggestions, to help cut back on friction from your diff try using a straight SAE 50 with double the friction modifiers if required for some limited slip rears, it won't hurt anything especially if it's a quarter mile car or weekender ride, not recommended for everyday street use or over 500 hp at the rear, I used this in my Buick to knock off .4 seconds through the trap, and tire air pressures are critical, BTW pull the axles part way out and pack the axle bearings with heavy chassis grease as they have a tremendous load to handle The little things will add up.
Here's some suggestions, to help cut back on friction from your diff try using a straight SAE 50 with double the friction modifiers if required for some limited slip rears, it won't hurt anything especially if it's a quarter mile car or weekender ride, not recommended for everyday street use or over 500 hp at the rear, I used this in my Buick to knock off .4 seconds through the trap, and tire air pressures are critical, BTW pull the axles part way out and pack the axle bearings with heavy chassis grease as they have a tremendous load to handle The little things will add up.
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The 4L85E and 10.5 full floating 14 bolt with a mechanical finger chopper fan eats about 22% in my 97 Express van. The 4L80E and 9.5 semi float 14-bolt with an electric fan setup in my 99 Tahoe eats right at 20%. Losses climb with the square of RPM as well. Down where peak torque happens you may only lose 12%. You have some parts of the driveline that is near a constant power loss such as the fluid pump in the trans and other losses that are variable like friction and oil windage.
T56 car is 13% seems to work most accurately. Making 02-04 C5z closer to 410flywheel even with 4.10 gears. But years ago an bone stock 2003 c5z made 363whp and an 01 made around 340whp bone stock also and on dynojets.
Some 01-02 f cars t56 make 300whp give or take. 300x1.13=340 and for Automatic cars of same years are about 10whp less.. 290whp. Using 17-18% from what some like to use for loss.. But for 4l60e trans I like using 17.5%..
So, 290x1.175=340 flywheel.
Long long ago, rule of thumb was higher for automatic cars at 20% dt loss. But trucks with heavier dt parts and taller tires or heavy tires, 12 bolt rears etc.. Will have higher % of dt loss. Along with gears. Cars with over 4.00 will technically read 10whp less on dyno. I have seen difference when I went to 4.10s in my 98 WS6 back in 2010.
Some 01-02 f cars t56 make 300whp give or take. 300x1.13=340 and for Automatic cars of same years are about 10whp less.. 290whp. Using 17-18% from what some like to use for loss.. But for 4l60e trans I like using 17.5%..
So, 290x1.175=340 flywheel.
Long long ago, rule of thumb was higher for automatic cars at 20% dt loss. But trucks with heavier dt parts and taller tires or heavy tires, 12 bolt rears etc.. Will have higher % of dt loss. Along with gears. Cars with over 4.00 will technically read 10whp less on dyno. I have seen difference when I went to 4.10s in my 98 WS6 back in 2010.
This may be a dumb question but, I was wondering what the Avg. horsepower loss is through the drive train on a LS1 car (Both A4 and M6)? I am interested to see what the numbers are! Also I am wondering if a Stalled Automatic makes a difference? I used the search option, but didn't see what I was looking for. Thanks in advance for the info!
