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well maybe in usa its a difference of dyno thats why they get only 280 and maybe cos automatic gear, with manual people get 320 in stock
 

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Better with Butter
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Not on a chassis dyno they don't. Not stock.
 

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What I mean is this: both in the U.S. and in Europe (everywhere else too) you have chassis and engine dynos.

For the auto manufacturers, they use engine dynos, with bare engines (with headers of some sort) on a stand. This is the industry standard (SAE) method for getting power/torque numbers to claim and publish.



For the average guy walking (or driving) off the street, an engine dyno is waaaaay more expensive to run on--can you imagine the labor costs in taking the engine out of the car, dynoing it, then putting it back in?

Therefore, when someone posts that they ran their car on a dyno, you can pretty much bet it's on a chassis dyno. Here in the U.S. -or- Europe.
 

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The biggest problem with dyno numbers is that they can be modified to make the customer happy. (Chassis) Dynos measure the hp and torque at the wheels, unless you take your engine out and put it on an engine dyno. The chassis dyno will show around 15%-20% less than the engine dyno due to losses in the transmission, driveshaft, etc. That number can be lowered depending on modifications made. Most chassis dynos allow you to put a correction factor to account for these losses. The correction factors can be manually enterred, so a dyno operator can put in whatever percent he wants to make his customer happy. Most good dyno operators will not put in a correction factor and will just tell you what the hp and torque are at the wheels (which is essentially all that really matters). However most people want to see BIG numbers or want to compare their car to the factory numbers. So dyno operators have been using correction factors to make them happy. Everyone wants to say that their car has a big HP number, but all I care about is how much of the HP is actually getting put to use by being transferred from my tires to the road.
 

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well maybe in usa its a difference of dyno thats why they get only 280 and maybe cos automatic gear, with manual people get 320 in stock
This post is why I said "not on a chassis dyno."

You're comparing apples to blueberries here.

In Europe (or anywhere, for that matter), people who claim they put their own cars on dynos are NOT getting 320 stock with manuals; they're getting something like 280 HP. They might be claiming 320 because they're guesstimating the power at the crank by the rule-of-thumb 15%-20% power-loss factor. That is, "I got 280 HP on this dyno run, now multiply by 1.15 for drivetrain losses. That gives me about 322 HP at the crank."
 

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The biggest problem with dyno numbers is that they can be modified to make the customer happy. (Chassis) Dynos measure the hp and torque at the wheels, unless you take your engine out and put it on an engine dyno. The chassis dyno will show around 15%-20% less than the engine dyno due to losses in the transmission, driveshaft, etc. That number can be lowered depending on modifications made. Most chassis dynos allow you to put a correction factor to account for these losses. The correction factors can be manually enterred, so a dyno operator can put in whatever percent he wants to make his customer happy. Most good dyno operators will not put in a correction factor and will just tell you what the hp and torque are at the wheels (which is essentially all that really matters). However most people want to see BIG numbers or want to compare their car to the factory numbers. So dyno operators have been using correction factors to make them happy. Everyone wants to say that their car has a big HP number, but all I care about is how much of the HP is actually getting put to use by being transferred from my tires to the road.
Generally, the chassis dyno correction factor is used to normalize to environmental variations from STD. 60degrees - 29.92baro and 0 percent humidity.

http://www.gtamc.com/forums/showthread.php?p=532760
 

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Generally, the chassis dyno correction factor is used to normalize to environmental variations from STD. 60degrees - 29.92baro and 0 percent humidity.

http://www.gtamc.com/forums/showthread.php?p=532760
Generally that is correct, however it is entered in manually by the operator. He can put in whatever he wants. Some operators enter in an additonal correction factor to guesstimate the power at the engine. I had a friend of mine who has a dyno in his shop show me how he can change the factors and make any HP numbers he wants. Dynos are a great tool to determine the gains you get from doing mods, but to compare dynos from different people (especially when they are run on different dynos) without knowing all the details is almost pointless. Next time I go by my friend's shop I will have my new 335i dyno'd twice. The first time to get legit numbers, the second time to put in some crazy factors to see how high I can get the numbers. I will scan in the dyno sheets when I get back home. Then everyone can see that stock numbers are probably around 260HP at the wheels and that with a good dyno cheat the "stock" horsepower can be raised to well into the 300s, maybe even 400+.
 
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