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SVTPerformance's Chain of Restaurants
Road Side Pub
RWHP vs BHP
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<blockquote data-quote="tt335ci03cobra" data-source="post: 16329882" data-attributes="member: 68944"><p>Too many variables. Rotational mass, height and rolling resistance of wheels and tires alone can distort any data. A sticky 28x12.50 drag slick at 15psi on a heavy old steel wheel will dyno far lower than a thin lean hard wall 24x8 economy all season tire on a carbon fiber rim. Put a 44” mud bogger on a 67hp del sol and it might just throw a rod.</p><p></p><p>Now consider internal issues like heat management. 50° changes the molecular state of aluminum or steel enough so that traces of loss bring to happen known as thermal loss. Very minor fusion is happening basically. Too cold to fully meld, but there’s some spit swapping of electrons at play... animals.</p><p></p><p>How about inertia loss. An object wants to remain at its current state so motivating it to do otherwise more tq. As rpm rises, there is additional resistance to spin that needs to be countered. As time to spin to rpm is reduced, additional motivation is required. Spinning a given car from 60-160mph in 4 seconds vs 15 seconds in 4th gear brings up many many variables besides just power needed. Assuming all variables are the same, simple math says you’ll just need x more tq/hp to do so, but in reality it’s almost always about 2-5% more than that. Inertia and thermal drag play into effect.</p><p></p><p>In general, I like to use what it lost stock vs engine hp (assuming healthy testing on a 70° day with low humidity) so let’s say 50hp/50tq and add on an extra 10% of that for every 100tq added.</p><p></p><p>Take a stock 6000rpm redline 400/400 car like a 2006 gto. They make 350/350wheel.</p><p></p><p>So it’s using about 50/50. Rpm is low on that car and it balances out well.</p><p></p><p>Take that car to 900whp/900wtq on a stockish redline of 6000rpm, and I’d personally assume 50/50 loss like stock and an addition 10% per 100tq so we are up 550tq vs stock. 10% of the original 50 loss at stock power level is 5tq. Multiplied 5.5 times is 27.5 Added to the original 50 I get 77.5tq loss at 900wtq so I’d guess the engine is actually about a 980/980 engine on an engine dyno fully dressed with accessories. This is all assuming everything is healthy and optimal regarding heat management, fluids and so on, wheels and tires are the same, drivetrain weight is same or lower, clutch is better etc.</p><p></p><p>I do this because builds aren’t done in a vacuum. We don’t just add power, we improve the half shafts, get better clutches etc and lighter driveshafts etc. lighter wheels etc.</p><p></p><p>I don’t buy the 15% garbage. It’s lazy math that’s as valid as saying I must have a 15% slower 60yd dash than someone of similar composition who is 15% taller. False.</p></blockquote><p></p>
[QUOTE="tt335ci03cobra, post: 16329882, member: 68944"] Too many variables. Rotational mass, height and rolling resistance of wheels and tires alone can distort any data. A sticky 28x12.50 drag slick at 15psi on a heavy old steel wheel will dyno far lower than a thin lean hard wall 24x8 economy all season tire on a carbon fiber rim. Put a 44” mud bogger on a 67hp del sol and it might just throw a rod. Now consider internal issues like heat management. 50° changes the molecular state of aluminum or steel enough so that traces of loss bring to happen known as thermal loss. Very minor fusion is happening basically. Too cold to fully meld, but there’s some spit swapping of electrons at play... animals. How about inertia loss. An object wants to remain at its current state so motivating it to do otherwise more tq. As rpm rises, there is additional resistance to spin that needs to be countered. As time to spin to rpm is reduced, additional motivation is required. Spinning a given car from 60-160mph in 4 seconds vs 15 seconds in 4th gear brings up many many variables besides just power needed. Assuming all variables are the same, simple math says you’ll just need x more tq/hp to do so, but in reality it’s almost always about 2-5% more than that. Inertia and thermal drag play into effect. In general, I like to use what it lost stock vs engine hp (assuming healthy testing on a 70° day with low humidity) so let’s say 50hp/50tq and add on an extra 10% of that for every 100tq added. Take a stock 6000rpm redline 400/400 car like a 2006 gto. They make 350/350wheel. So it’s using about 50/50. Rpm is low on that car and it balances out well. Take that car to 900whp/900wtq on a stockish redline of 6000rpm, and I’d personally assume 50/50 loss like stock and an addition 10% per 100tq so we are up 550tq vs stock. 10% of the original 50 loss at stock power level is 5tq. Multiplied 5.5 times is 27.5 Added to the original 50 I get 77.5tq loss at 900wtq so I’d guess the engine is actually about a 980/980 engine on an engine dyno fully dressed with accessories. This is all assuming everything is healthy and optimal regarding heat management, fluids and so on, wheels and tires are the same, drivetrain weight is same or lower, clutch is better etc. I do this because builds aren’t done in a vacuum. We don’t just add power, we improve the half shafts, get better clutches etc and lighter driveshafts etc. lighter wheels etc. I don’t buy the 15% garbage. It’s lazy math that’s as valid as saying I must have a 15% slower 60yd dash than someone of similar composition who is 15% taller. False. [/QUOTE]
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RWHP vs BHP
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