KaiserBill
04-08-2015, 11:45 PM
https://www.youtube.com/watch?v=qqQzU-q8S2o
Everyone, loves power! We know it. We see it. It sells cars, trucks, tractors, computers, winches, blenders ect and so on.... It has become the advertisers best tool for selling people on motor vehicles and of course modifications for the home turner. The cleaver ladies and gentlemen of the advertizing companies world wide have come up very devious ways of marketing vehicles power ratings. It's not that the car manufacturers are lying-- they just aren't forthcoming with information.
Usually manufacturers love to say things like SAE Net Horsepower Standard X HP... So what is this mysterious standard? Well basically it says that the manufacturer must test his or her engine on the dyno with all the accessories and exhaust requirements for the vehicle to be road legal. Thus you are given a crankshaft output measurement. So, what does that mean to home tuner? Well, not much really. It means that in some laboratory like setting the manufacturer setup a collection of engines perhaps maybe 5-10 engines that they feel best represent this engine and they test them. They get a bunch of numbers on torque and horsepower and so on. They do some simple statistics to develop the details they want and they calculate the manufacturing tolerances and poof they get your end results which is the engine produces X Hp under Y conditions and with our manufacturing capabilities this engine will Z tolerance in power. All of these get boiled down two numbers: X Hp SAE Net and Y Torque Net.
These are sadly not really totally representative of the engine found under your hood. Yes, that's right your engine under the hood may or may not make manufacturer's claimed HP. Just like your vehicle may or may not be identical to the same model sitting in the lot due to manufacturing tolerances! And tolerances really do matter! This where it gets really really difficult to test items on your own. Even car magazines really don't have the capabilities to do proper testing on a product. Usually, because they lack the time to do so before publication.
So, this becomes the great domain of the internet and so much conjecture. And since people in advertizing know that people like technical information they usually like to feed them tools and just enough information to be dangerous with it on the internet!
What do I mean by being dangerous? Well, by dangerous I mean merely overstating possible information without having a proper sample size of the items in question to really make usable generalizations. In my field we call that a hasty generalization and it isn't good. I think of the best cases of this drive-train power loss. This is one of the more complex areas of testing in the tuner world because it requires the elimination of many variables and it creates great controversy because people want a simple multiple by x to get y solution. There just really isn't one. There you go you cannot go to your chassis dyno system and expect to get really any good data on your out at the crankshaft. The best you can do is figure out what you're getting at the wheels. Which is an important piece of the puzzle but it doesn't tell you much.
So, for example you've got engine x rated by the manufacture for 350hp at the crankshaft (SAE Net HP). Okay, that is great , sounds awesome, sounds like you have or going to have great HP at the wheels. So you dyno chassis test the engine and find out that you've only got 200 HP at the wheels? And you're scratching your head because 42.8571% was just some how lost to the ether of the Mechanical Gods? What happened? Well, you might chalk this up to having a totally inefficient drive-train. Or you might say wait a minute-- why not check my engine. Then you find out that wait half of that 42.8571% was really not at all lost due to the drive train. It was in fact found to be lost in the manufacturing process of the engine. You lost a little over 21% due to the fact that your engine wasn't as well built as it could be. Sure, it fell within the manufacturer's tolerances and it is still fits their within their 350hp class requirements but it isn't exactly 350hp! Now, once you know this fact you start to work on the drive-train. And figure out is there any way I can save some power loss in the transmission? Or, can I do something to the rear end and maximize their performance-- sure maybe I'll only 1%-2% here or there but if I turn 21+% down to 18% I've saved 26+ hp to be sent to my wheels and the ground instead of wasted as heat and friction. That is without even touching the engine. If you touch the engine and blue print it and do other things who knows what you can do.
Essentially, my point is before you start accepting data from people who've chassis dynoed their engines only-- ask them have they tested the engine itself outside of the frame? Have they measured the crankshaft Hp? Have the really looked into the drive train loss because you know what you might find that your going to be surprised. For example if some one tells you that a stock JKU engine is making 190hp at the wheels and 285HP at the crankshaft-- and that proves that Wranglers loose 33% roughly of their power to waste in the transmission, transfer case, and rear differentials. And that they slapped on a turbo or supercharger and now have 360HP at the rear wheels... I would think twice before I accept that 33% loss in power-- first off you would need 540hp at the crankshaft to achieve 360hp at the rear wheels... That is not going to happen with a bolt on kit. You just cannot develop that power with a 10.2:1 compression ratio engine with 93octane pump gas on an engine that hasn't been hand built. Its just going to pre-detonate or the engine management system will reduce the fuel to prevent that knock and thus reduce power creation. So, while the 360Hp at the rear wheels is not in dispute, the crankshaft hp has to be. It is more likely that you're getting much lower amounts of power loss in the drive-train to account for your 360hp at the rear wheels. The only way to know for sure is to put the engine on a dyno and test it outside of the chassis.
However, all of this testing costs lots of money. So, you either basically make claims you cannot really back up with empirical evidence or you state the claims you can. I make x at the wheels within x amount of error percentage and that I can prove. Which I'm cool with. It will allow you do a lot of calculations. However, it wouldn't let you predict anything about if you put new engine x mod in your truck with any reliability. Because all you know is the end result. You've got 360Hp at the wheels. You really don't know if you have 540hp or some other number that is much less than that. Which means when you put new modification x and expect to see result y-- you'll probably be very disappointed.
Everyone, loves power! We know it. We see it. It sells cars, trucks, tractors, computers, winches, blenders ect and so on.... It has become the advertisers best tool for selling people on motor vehicles and of course modifications for the home turner. The cleaver ladies and gentlemen of the advertizing companies world wide have come up very devious ways of marketing vehicles power ratings. It's not that the car manufacturers are lying-- they just aren't forthcoming with information.
Usually manufacturers love to say things like SAE Net Horsepower Standard X HP... So what is this mysterious standard? Well basically it says that the manufacturer must test his or her engine on the dyno with all the accessories and exhaust requirements for the vehicle to be road legal. Thus you are given a crankshaft output measurement. So, what does that mean to home tuner? Well, not much really. It means that in some laboratory like setting the manufacturer setup a collection of engines perhaps maybe 5-10 engines that they feel best represent this engine and they test them. They get a bunch of numbers on torque and horsepower and so on. They do some simple statistics to develop the details they want and they calculate the manufacturing tolerances and poof they get your end results which is the engine produces X Hp under Y conditions and with our manufacturing capabilities this engine will Z tolerance in power. All of these get boiled down two numbers: X Hp SAE Net and Y Torque Net.
These are sadly not really totally representative of the engine found under your hood. Yes, that's right your engine under the hood may or may not make manufacturer's claimed HP. Just like your vehicle may or may not be identical to the same model sitting in the lot due to manufacturing tolerances! And tolerances really do matter! This where it gets really really difficult to test items on your own. Even car magazines really don't have the capabilities to do proper testing on a product. Usually, because they lack the time to do so before publication.
So, this becomes the great domain of the internet and so much conjecture. And since people in advertizing know that people like technical information they usually like to feed them tools and just enough information to be dangerous with it on the internet!
What do I mean by being dangerous? Well, by dangerous I mean merely overstating possible information without having a proper sample size of the items in question to really make usable generalizations. In my field we call that a hasty generalization and it isn't good. I think of the best cases of this drive-train power loss. This is one of the more complex areas of testing in the tuner world because it requires the elimination of many variables and it creates great controversy because people want a simple multiple by x to get y solution. There just really isn't one. There you go you cannot go to your chassis dyno system and expect to get really any good data on your out at the crankshaft. The best you can do is figure out what you're getting at the wheels. Which is an important piece of the puzzle but it doesn't tell you much.
So, for example you've got engine x rated by the manufacture for 350hp at the crankshaft (SAE Net HP). Okay, that is great , sounds awesome, sounds like you have or going to have great HP at the wheels. So you dyno chassis test the engine and find out that you've only got 200 HP at the wheels? And you're scratching your head because 42.8571% was just some how lost to the ether of the Mechanical Gods? What happened? Well, you might chalk this up to having a totally inefficient drive-train. Or you might say wait a minute-- why not check my engine. Then you find out that wait half of that 42.8571% was really not at all lost due to the drive train. It was in fact found to be lost in the manufacturing process of the engine. You lost a little over 21% due to the fact that your engine wasn't as well built as it could be. Sure, it fell within the manufacturer's tolerances and it is still fits their within their 350hp class requirements but it isn't exactly 350hp! Now, once you know this fact you start to work on the drive-train. And figure out is there any way I can save some power loss in the transmission? Or, can I do something to the rear end and maximize their performance-- sure maybe I'll only 1%-2% here or there but if I turn 21+% down to 18% I've saved 26+ hp to be sent to my wheels and the ground instead of wasted as heat and friction. That is without even touching the engine. If you touch the engine and blue print it and do other things who knows what you can do.
Essentially, my point is before you start accepting data from people who've chassis dynoed their engines only-- ask them have they tested the engine itself outside of the frame? Have they measured the crankshaft Hp? Have the really looked into the drive train loss because you know what you might find that your going to be surprised. For example if some one tells you that a stock JKU engine is making 190hp at the wheels and 285HP at the crankshaft-- and that proves that Wranglers loose 33% roughly of their power to waste in the transmission, transfer case, and rear differentials. And that they slapped on a turbo or supercharger and now have 360HP at the rear wheels... I would think twice before I accept that 33% loss in power-- first off you would need 540hp at the crankshaft to achieve 360hp at the rear wheels... That is not going to happen with a bolt on kit. You just cannot develop that power with a 10.2:1 compression ratio engine with 93octane pump gas on an engine that hasn't been hand built. Its just going to pre-detonate or the engine management system will reduce the fuel to prevent that knock and thus reduce power creation. So, while the 360Hp at the rear wheels is not in dispute, the crankshaft hp has to be. It is more likely that you're getting much lower amounts of power loss in the drive-train to account for your 360hp at the rear wheels. The only way to know for sure is to put the engine on a dyno and test it outside of the chassis.
However, all of this testing costs lots of money. So, you either basically make claims you cannot really back up with empirical evidence or you state the claims you can. I make x at the wheels within x amount of error percentage and that I can prove. Which I'm cool with. It will allow you do a lot of calculations. However, it wouldn't let you predict anything about if you put new engine x mod in your truck with any reliability. Because all you know is the end result. You've got 360Hp at the wheels. You really don't know if you have 540hp or some other number that is much less than that. Which means when you put new modification x and expect to see result y-- you'll probably be very disappointed.