flywheel or Rear-wheel?
05-27-2008, 08:17 PM
#41
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The Vette engine actual has several subtle differences.
But that aside, I truly believe any Fbody Ls1 makes a genuine 320-350bhp SAE Net. The "advertised" figure was a whole lot cheaper option than really detuning the engine.
I think it was Popular Hotrodding. And if I remember the article correctly they used a different type of engine dyno and admitted that the engine would need to make 'x' more hp to be inline with GM's ratings. However I do believe it made something like 7 or 9hp more which is less than a 2% variance.
Caution maybe but not the constant understatement that appears on forums.
And yes apples to apples. But its so rare that it happens. As there are way too many variables. As not every graph post (or even the majority) are anywhere near using the same standards.
Yep and if you do a little research it's generally considered that point of view is non realistic and for the hopeful.
It stands on several reasons:
-Even without engine alterations when cars where rated at SAE Net and not Gross they lost a lot of HP, sometimes over 100hp.
-If they really produced that kind of power why the hell where those cars not WAY faster. And no, citing the tyres is not an excuse, because today old cars run modern tyres.
-Are you seriously saying that an old OHV lump with it's origins in the late 40's early 50's, using no form of CAD or CAM, with pretty poor manufacturing tolerances (by today's standards) actually produce more specific hp (bhp/litre) than modern engines like the Dodge Hemi and the LS7?
Interesting reading:
But that aside, I truly believe any Fbody Ls1 makes a genuine 320-350bhp SAE Net. The "advertised" figure was a whole lot cheaper option than really detuning the engine.
I think it was Popular Hotrodding. And if I remember the article correctly they used a different type of engine dyno and admitted that the engine would need to make 'x' more hp to be inline with GM's ratings. However I do believe it made something like 7 or 9hp more which is less than a 2% variance.
Caution maybe but not the constant understatement that appears on forums.
And yes apples to apples. But its so rare that it happens. As there are way too many variables. As not every graph post (or even the majority) are anywhere near using the same standards.
Yep and if you do a little research it's generally considered that point of view is non realistic and for the hopeful.
It stands on several reasons:
-Even without engine alterations when cars where rated at SAE Net and not Gross they lost a lot of HP, sometimes over 100hp.
-If they really produced that kind of power why the hell where those cars not WAY faster. And no, citing the tyres is not an excuse, because today old cars run modern tyres.
-Are you seriously saying that an old OHV lump with it's origins in the late 40's early 50's, using no form of CAD or CAM, with pretty poor manufacturing tolerances (by today's standards) actually produce more specific hp (bhp/litre) than modern engines like the Dodge Hemi and the LS7?
Interesting reading:
I know that the older cars went by gross hp but so did everything. That was the standard of the day. They were "underrated" compared to most other cars on the market. If you dyno'd an LS7 under that system then maybe it would make 600 hp instead of 505. It's all relative.
05-27-2008, 08:28 PM
#42
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When you're making more horsepower, you're doing more work per unit time. The rated horsePOWER of the engine indicates the amount of work the engine can produce per unit time. Torque and horsepower are intrinsically related. Friction from the surface is what moves the automobile. The greater the force you can give the rotating tires, the greater the ground will propel the car. When considering two engines with a disparity in horsepower rating and all other things being equal, I don't see how the total friction from the bearings and everything would magically increase for the engine that makes more horsepower. The inertia of the drivetrain pieces wouldn't magically increase either. Someone correct me if I'm wrong. There are some things I could be overlooking.
05-27-2008, 10:01 PM
#43
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The moment of inertia of the drivetrain does not increase. The angular acceleration does. Everything you need to know is in the formula τ = Iα. τ is torque, I is the moment of inertia(constant for a given drivetrain), and α = angular acceleration. When the angular acceleration of the drivetrain increases (when the car accelerates more quickly) it requires more torque to due so. If I is constant then τ(the power lost to the drivetrain) must increase when α increases.
torque = rotational intertia * angular acceleration is the rotational analog of F=ma. The fluids inside the transmission, etc., are subject to drag. As with a moving vehicle through air (a fluid), more horsepower is required to plow through the atmosphere at higher and higher speeds/accelerations. The same is true for the internal drivetrain components. I would venture to say the percentage obviously isn't fixed but in a closely space domain.
05-28-2008, 10:23 AM
#44
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https://ls1tech.com/forums/showpost....8&postcount=10
the things called STICKIES arent there to make the page look cute.........open some up and read them........
the things called STICKIES arent there to make the page look cute.........open some up and read them........
05-28-2008, 12:06 PM
#46
Im confused as to how people are arguing against using a certain percentage of drivetrain loss (say 15% as used in previous posts) as a very basic gauge of Rwhp? There are tons of variables (tranny, gears, rear, etc) that will cause this number to vary but people just use this as a general guide as to what a car potentially should be making at the rear wheels given a fly wheel horsepower rating (engine dyno rating). The best method though is to just get the car dynoed to know for sure. Also, why wouldnt the amount of HP lost increase as the power you make increases? Honestly im just basing this off what ive seen cars dyno and I could be completely wrong but lets say you have a car with the same drivetrain setup and one is a stock ls1 while the other is a twin or large single turbo iron block 408 making 1000hp on an engine dyno. The stock ls1 loses say 50 hp from its flywheel rating to its rwhp measure, does this mean that the 1000 flywheel hp (again measured with an engine dyno), should then leave you with 950 rwhp on the twin or single large turbo setup?
05-29-2008, 01:10 AM
#47
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ok so sum this up for me:
Car companies rate their hp at the engine, and the 01/02 camaro ss was rated at "325 hp," and that was supposedly at the engine, but it was under rated and that number was actually closer to the rearwheel hp. Correct?
So the 03/04 cobra was rated at 390 hp, and since car companies rate at the engine, this 390 hp is at the engine. Correct?
Speaking of Ford, an 02 mustang gt is rated at 260 hp, so this is at the engine too, right?
Car companies rate their hp at the engine, and the 01/02 camaro ss was rated at "325 hp," and that was supposedly at the engine, but it was under rated and that number was actually closer to the rearwheel hp. Correct?
So the 03/04 cobra was rated at 390 hp, and since car companies rate at the engine, this 390 hp is at the engine. Correct?
Speaking of Ford, an 02 mustang gt is rated at 260 hp, so this is at the engine too, right?
05-29-2008, 09:57 AM
#49
ok so sum this up for me:
Car companies rate their hp at the engine, and the 01/02 camaro ss was rated at "325 hp," and that was supposedly at the engine, but it was under rated and that number was actually closer to the rearwheel hp. Correct?
So the 03/04 cobra was rated at 390 hp, and since car companies rate at the engine, this 390 hp is at the engine. Correct?
Speaking of Ford, an 02 mustang gt is rated at 260 hp, so this is at the engine too, right?
Car companies rate their hp at the engine, and the 01/02 camaro ss was rated at "325 hp," and that was supposedly at the engine, but it was under rated and that number was actually closer to the rearwheel hp. Correct?
So the 03/04 cobra was rated at 390 hp, and since car companies rate at the engine, this 390 hp is at the engine. Correct?
Speaking of Ford, an 02 mustang gt is rated at 260 hp, so this is at the engine too, right?
05-29-2008, 10:47 AM
#50
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ok well then what do the stock 03 cobras put down at the rear wheels on average, and what about the 99-04 GTs?
Im building a sbc and im trying to get an idea of what cars have what horsepower numbers at the wheels to see where I will compare...
Im building a sbc and im trying to get an idea of what cars have what horsepower numbers at the wheels to see where I will compare...
05-29-2008, 05:24 PM
#51
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Best bet is do some research on other forums and the web.
BUT be mindful of STD/SAE and Dynojet/Mustang Dyno numbers it'll give you at least a 20rwhp variance on almost any car making over 200hp.
BUT be mindful of STD/SAE and Dynojet/Mustang Dyno numbers it'll give you at least a 20rwhp variance on almost any car making over 200hp.
