You are here: Forums Speed Shop Tuning and Modification Horsepower to Weight Ratio

Horsepower to Weight Ratio

22 messages,  Last post on Oct 24, 2006 at 4:56 PM

You are in the Speed Shop Tuning and Modification Forum. Your Host is steve_

What is this discussion about? Dodge Viper, Porsche Carrera GT, Chevrolet Corvette, Ford Mustang SVT Cobra, Performance Mods

Messages Page 3 of 3 1 2 3 Prev Next Last

Go To Msg # Search This Discussion

#19 of 22 Re: Horsepower to Weight Ratio [steve_] by starrow68 Oct 07, 2006 (5:01 pm)
Replying to: steve_ (Oct 06, 2006 8:21 pm) Low wt/HP cars are not just a hoot on the street. I see many trailered into HPDE track events that don't have plates and not all of them are driven at the limits, for that matter neither are the street legal ones. Last weekend I got to watch a 70-72? Pantera with a 351 Cleveland engine, best sounding machine I've heard lately, go around Buttonwillow Raceway. It was formerly a race car owned by Bob Woodhouse, still in World Challenge, and had been updated after sitting for over a decade. Probably 450+ HP for a package that should have been under 3000 lbs. The guy was very conservative on track, not a replaceable car. Randy
#20 of 22 torque and gearing by jimveta Oct 21, 2006 (7:34 pm)
Steve, torque really is just torque and is the same once it gets to the wheels whether it comes from the engine or tranny. Non-inertial chassis dynos (those that apply a constant/braking load and can hold a car at a particular RPM) can show *REAL* torque output at the wheels. When you choose that option, you'll see high revving I4 cars making something like 250hp and 800 lb-ft.   Now if you're wondering then how does that work out with the equation of HP = Tq * RPM / 5252, you have to measure the RPM where you measure the torque. So the HP works out because RPM is not the engine rpm, but rather the wheels (or equivalently dyno rollers).   I think a good way to think of torque is the ability gain HP faster.
#21 of 22 hp / weight by jimveta Oct 21, 2006 (7:47 pm)
While I agree that having higher hp / weight ratio is more ideal.. I think one has to also consider that hp / weight is not static, meaning that when most quote hp/weight, they are really stating the *peak* hp/weight ratio.   As an extreme example, try putting an F1 engine in a Hummer.. yes, the (peak) hp/weight fiqure will improve a great deal, but I bet it'll actually be slower in most cases! We can talk about the subject of torque, but we can omit the term "torque" entirely to simplify things and simply speak of HP, but now include RPMs.   So to truely determine the potential performance from hp/weight figures, we need to also consider hp/weight across all RPMs. But if we were to settle on "single" figure that's indicative of such across the board performance, perhaps *average* HP / weight would be it. Popular Hotrodding magazine for exmaple, scores participants' engines based on average HP in their annual EngineMasters contest.   Going back to the F1 example, it reminds me of a Motortrend article I read a few years ago where the author had his first experience driving an Forumla car. He stated that it was like learning how to drive a manual tranny all over again.. because clutching in at 4000+ rpms, still stalls the car!! Although I guess that's to be expected because that was close to where his car idled. I've read of more recent cars idling even higher..   Another example is Edmunds' own review of the Subie WRX wagon with automatic tranny: http://www.edmunds.com/insideline/do/Drives/Followup/articleId=48462 Accelerating right off idle resulted in 0-60 of 8.7 seconds. Brake launching at 3000 rpms, spooling the turbos up results in a 0-60 of 6.7 seconds. I should say though that the performance of turbocharged cars are even harder to model because not only does HP vary by RPM, but there is a transient effect varying HP at the same point of waiting for the turbos to spool up, if not already.   Another in similar vien was a C&D comparison of various cars. The S2000 faired significantly worse doing 5-60 (high 8's) than 0-60 (slipping the clutch in at nearly 5000 rpm; 6.1 if I recall). And again, I think we can predict or model these outcomes if we look at power delivery instead of only peak output.
#22 of 22 Re: Horsepower to Weight Ratio [subygt] by brianapal Oct 24, 2006 (4:56 pm)
Replying to: subygt (Oct 02, 2006 4:24 pm) 1995 Corvette 1999 Corvette 2001 Corvette I am missing something here Subygt?????????   You compare these cars to a 2007.   It is 2006 and they are selling 2007 Corvettes!   I agree that the weight to horsepower ratio does mean something but why are you talking about ancient history??? But your comparisons are meaningless. Why don't you compare a 2007 Porsche to a 1958 Corvette? That would be a real valid comparison wouldn't it!   The 2007 Corvette coupes and convertibles and the 2007 ZO6 are all street legal cars that are great sports cars!    It is pretty obvious that you don't own any of the 3!

Messages Page 3 of 3 1 2 3 Prev Next Last

Go To Msg # Search This Discussion

You are here: Forums Speed Shop Tuning and Modification Horsepower to Weight Ratio