nevermind

 

You guys who keep saying it's a percentage and "that's it" are not justifying yourselves. He is asking WHY is it a percentage, and no one has answered that yet.

The fact is that the percentage is bunk and so is a constant number. I have stated before that in order to get a loss percentage you would have to measure HP on an engine dyno AND a chassis dyno, then calculate. This loss percentage would be unique to YOUR car at THAT SPECIFIC power level.

Here is why:

The factory CLAIMS that stock power is 271. For all we know it could be 300 and it could be 250. That would dramatically alter a drivetrain loss percentage on a car with 225 AWHP, wouldn't it? That could put loss anywhere from 10% to 25% for that car. However, we have no way of knowing what the engine HP really is. The percentage provides only a very rough estimate.

This is one good reason why dyno numbers are useless in comparing cars power levels, especially on different dynos.

Case in point, I dynoed 292 AWHP and can outrun guys that dynoed 320 AWHP on a different dyno.

Dyno numbers are only good for tuning and comparing yourself against yourself.

Drivetrain loss is parasitic. This means that it takes power to move the parts and it does not give any back. These parts have capacities. Power capacities, heat capacities, rotational capacities, etc. Once you start nearing their limit with more power, more heat (given of as useless energy as power increases) and more vibration through a drivetrain, more power will be lost as power levels increase.

This can almost be looked at as a percentage of loss, but it is not linear (the stock loss percentage will not be the same as a modified car's loss percentage) so the number can also be looked at as semi-constant.

So if the percentage is not linear then it is not a constant percentage as the majority public implies/accepts. However, this makes it easier to estimate/baseline over a broad range of cars and power levels. I would say that the higher the power levels, the less accurate a loss percentage becomes.

You can measure a percentage of ANYTHING. What percentage of your wealth (or lack thereof) is in your pocket vs. your bank account? What percentage is your shoe size vs. your height? Etc, etc, etc.

In Marketing, demographics (age, income, gender, education, etc) are inaccurate and cannot reliably be used to segment a market. Someone who makes 30K a year can very possibly like Cheerios just like the guy who makes 100K a year (as an example). However, even due to its pointlessness, demographics are still used because they are cheap to measure and provide an "accurate enough" picture of consumers/habits.

Same thing with dyno loss percentages. They mean nothing, but are easy to understand and estimate with. Take them with a grain of salt.

 

Since the 4g63 has been around awhile, has anyone or company actually engine dynoed it to see what the 2.0 liter output really is with this turbo? I would like to know the true crank HP number and how close to 271 it really is. I'm hoping it is underrated from the factory.

 

You couldn't even apply that across the board if it did exist. Especially if it was a motor from a different year (1990-2002). Heck even the 05's have a different rating. On top of that, some may put out 285 and some may put out 260 due to minute manufacturing variations.

 

Wow. I know there are car to car variences on the dyno, but I am shocked that the same engine coming off the assembly line even with minute variations would show that kind of significant HP difference. So an engine bench dynoed at 285 and another at 260 just because of a "slight variation". Imagine how much more difference there is when you add drivetrain loss.

I know if I was an engineer, I would not be happy with that kind of HP variation engine to engine. Maybe 1 to 2 HP.

 

I am leaning more toward what EVOTEXAS is saying. Theoretically it just makes more sense then if the loss was a fixed percentage. It would be nice to know what the actual engine output is? Anyone at all know this rating. Has it even been tested?

Shane

 

If someone wanted to take the time and effort, I am sure that the 4G63 could be put on a dyno, but you would have to set up the intercooler, the pipeing, the engine, exhaust ect to get a correct figure. Just changing the intercooler piping for example would result in a differetnt hp number not to mention exhaust ect. It would be a pita to try and get all of that set up to get a crank number, but if anyone wants to try then go right ahead.

 

Such is life.