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given rwhp, approximate crank hp

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Old 05-23-2009, 08:14 PM
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withagee
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Default given rwhp, approximate crank hp

Have had the car on jack stands for quite a few months adding parts here and there. Recently got the car tuned at Forged Performance.

The guys that knew I was working on the car also knew my goal was at least 400 rwhp. We got that...+

Lets say I'm making 400 rwhp based on the dyno sheet... Can a reasonable approximation of the crank hp be made given that number or is more information necessary? By "crank hp", I am referring to the hp numbers that car manufacturers specify.
Old 05-23-2009, 09:19 PM
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davidv
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Parasitic loss of the drive train increases with speed, so figure between 5-17 percent. Multiply drive horsepower by 1.05 and 1.17. That's about 420-468 horsepower at the crank.
Old 05-23-2009, 09:33 PM
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freedonutss
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Forged performance utilizes a dyno dynamics which typically read lower than other dynos.
Old 05-24-2009, 08:56 AM
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withagee
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Originally Posted by freedonutss
Forged performance utilizes a dyno dynamics which typically read lower than other dynos.
Wow. Really? Well... that sounds great if typically it reads lower than actual... would you know if that's the case? Love to find out I got a little more bang for my bucks.
Old 05-24-2009, 09:05 AM
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withagee
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Originally Posted by davidv
Parasitic loss of the drive train increases with speed, so figure between 5-17 percent. Multiply drive horsepower by 1.05 and 1.17. That's about 420-468 horsepower at the crank.
Help me understand this in more familiar terms, please. Are you saying the drive train causes greater and greater hp loss at the wheels the faster you go? I don't have a clue but I'd like to learn. My first thought would be it would have less and less effect because momentum or inertia... see where I'm coming from?

thanks
Old 05-24-2009, 09:54 AM
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freedonutss
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Originally Posted by withagee
Wow. Really? Well... that sounds great if typically it reads lower than actual... would you know if that's the case? Love to find out I got a little more bang for my bucks.
Yes that is the case, Dyno dynamics read lower than other dynos. Remember, a dyno is just numbers. What you can do at the track with the numbers is what really matters.

Live your life a quarter mile at a time, all the other bs doesnt matter. For those 10 seconds or less, your free.
Old 05-24-2009, 11:19 AM
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blazefast
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I usually figure 10-15% for RWD, about 10 percent higher for AWD, and add a bit more if you have an automatic transmission, as the torque converter on a stock transmission gives you significant power loss.
It's hard to say exactly how much power you're losing, but what does it really matter? All the power in the world means nothing if you can't put it to the ground.


PS - SWAT came into my house, disrespected my whole family, because somebody narcd me out, and you know what? IT WAS YOU!
Old 05-24-2009, 01:51 PM
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withagee
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[QUOTE=blazefast;7361950] It's hard to say exactly how much power you're losing, but what does it really matter? All the power in the world means nothing if you can't put it to the ground. [QUOTE]

Just a metric I use in my overall strategy. Know your enemies (art of war). Good starting point for that would be manufacturer's claim of crank hp, no?

Next move is getting both rear wheels churning. I have a base model. Leaning towards Quaife. Understand it's a relatively simple install and have read good reviews. This should aid in getting all that power in my world to the ground.

PS - sorry about the whole SWAT thing... I was bored.
Old 05-24-2009, 05:23 PM
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BrazenZ
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Originally Posted by freedonutss
Forged performance utilizes a dyno dynamics which typically read lower than other dynos.
It's not that dyno dynamics reads lower, its that dynojet numbers are usually inflated.

Last edited by BrazenZ; 05-24-2009 at 05:33 PM.
Old 05-24-2009, 05:39 PM
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0jiggy0
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It sounds like you need a number to brag to your friends. So why don't you just say 500hp who cares?
Old 05-24-2009, 06:34 PM
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withagee
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Originally Posted by 0jiggy0
It sounds like you need a number to brag to your friends. So why don't you just say 500hp who cares?
Brag? not hardly sport...... if I was the type maybe your familiar with I could just say "500hp" many thousands of dollars ago, right? I'll say 500hp when a reputable tuner like Sharif says the machine is there. I'm well past the age that I find it necessary to walk about with all muscles contracted. If you're smart you have goals; if you're wise you have strategies to reach those goals; if you're experienced you have metrics to measure your progress to your goals

Sounds like I care, huh? you bet your ride I do. Thanks for your input.
Old 05-24-2009, 06:38 PM
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withagee
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Originally Posted by BrazenZ
It's not that dyno dynamics reads lower, its that dynojet numbers are usually inflated.
Interesting
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