http://www.aus300zx.com/forum/showthread.php?t=322675 R/T .375 60' 2.081 330' 5.602 1/8 8.517 @ 86.64 mph 1000' 10.918 1/4 mile 12.920 @ 114.41mph As the posts say, extremely hot track surface temps & likely to have pulled a lot of timing due to high air temps. No logging done so no idea what the ECU was doing, I went with only one goal and JUST got there. Brings up the point about air temp etc again, also track condition, half of Meremere track was actually uphill before the resurface (just look for vids you will see it for yourself). The last dyno run I did was on a nice mild day so yes the car made XXXKws there & then on that machine & no the figures might not line up with the results from the drags on a completely different day - that does NOT say the qtr mile result overrules the dyno result, it just says they were different.
Just a question, how often is the strip cleaned/resurfaced etc over there? over here its very frequent. I've seen old videos with what looked like weeds growing on it
The dyno is a tool to measure a vehicles POWER, so yes, I would. The track is a tool to measure speed ( distance divided by time). If a dyno gives a vehicle a power rating of x, then within the level of accuracy of the measurement'tool', that value should be honored. We have already identified that the dyno has varying shortfalls in accuracy and repeatability, but taken into consideration it does its job. Are you sure you are not confusing you analogy of car A and car B on the drag strip trap speed as a measure of "performance" not power?
No confusion here, what i wrote is what i meant. Say your car trapped 130mph-ish and made 400rwkw on one dyno and say these numbers were fairly well aligned with how much power/weight you have. You suddenly go to the next dyno shop and make 500rwkw, which one is correct? the one with the bigger number right? because everyone likes big numbers. I dunno how common that would be in NZ, but here in Aus, you gain 50rwkw just by going to another operator. There are a few such as MRC and Unigroup though that have dyno's that match MPH very closely. And here we stand, i call a truce, you believe one thing i believe another. This is turning into argument for the sake of an argument. People bicker the same over religion so me thinks it time to call it quits.
one of the reasons the trap speed is an accurate indication of power is because its based on the rate of acceleration in about 66ft/20m before the finish line not the speed you were doing that instant. so unless you are wheel spinning really bad all the way down the track or through the trap then the mph will be very consistent.
This is a typical formula used by a simple HP calculator. HP = ( MPH / 233 ) ^ 3 * lbs This is the formula used by a simple mph calculator. MPH = ( (HP / lbs ) ^ .333333 ) * 233 It is a handy calculation to be used as a rough guide but that's about all it is. Probably accurate within +/- %20 depending on engine type, induction type, transmission and many other variables. According to the simple formulas a 600 hp 3.0L turbo engine will perform exactly the same as a 600 hp 8.0L naturally aspirated engine over the 1/4 mile. This is what the parameters for a more comprehensive computer model looks like. If you were to input the figures from a dyno run into this sort of computer model then you would expect it to be reasonably accurate.
Load of bullshit Trap speed is measured using a pair of beams & the time it takes to break the second beam after the first or a laser or radar system. Acceleration IS NOT measured at the end of a qtr mile & that's why that information is never given to you on a time slip - it's never measured or recorded. You'd think if a qtr mile were such a great tool for measuring HP if you had the weight they would have a set of scales at the start line & show the estimated HP after every run. Give it away already guys you're just dragging the forum down in stupidity. Qtr mile measures performance in speed Dyno measures performance in HP
The only information you can get from a 1/4 mile trap speed is the average power it took to get that vehicle to that speed in that distance... i.e. the power you were able to get to the ground. So, if your setup/driving is good you will get a figure that is close to your actual @whp, conversely if it is bad you won't come close. So, the dyno is there to give an indication of how fast you could be at the end of the 1/4 mile... then it is up to you to set the car up and learn to drive to get it there, or there about.
As Andy has provided, from a give number (MPH trap speed) it IS possible to back calculate the approx. HP of the car. Not sure if that formula is for rear wheel HP or fly wheel HP. Not one person here is stating that a qtr mile HP calculations is replacing a dyno HP measurements, so I can't see why you are getting so heated mungzy. There is no one definitive way to get a repeated HP record. If I put my car on the Dyno in Dubbo, each run will yield a different HP number. If I go there a week later I'll get different figures again. All it tells me is I am producing approx. 165 Hp not 280 HP that I wish I could. The HP is a number and is only really important to the owner. So what! Its how you drive your car, be it on street or strip. that counts, and the fun you have doing it. We all know the Americans do things different. Lets just leave their dyno figures to them. PS if this thread get any more off a discussion level then you know what will happen.
I actually posted the formulas to show how simplistic they are and therefore that you should not put too much faith in them. HP = ( MPH / 233 ) ^ 3 * lbs MPH = ( (HP / lbs ) ^ .333333 ) * 233 Relying on a formula with two variables to accurately predict the performance of a car on a drag strip is rather optimisitic. The key to the formula is the constant 233 which I have seen vary in different calculators from 230 to 234. This constant was probably derived by analysing the performance of naturally aspirated V8 engines over the 1/4 mile, the dyno measured peak HP of the engine and the weight of the car with driver. It is a quick and dirty rough guide to the performance you can expect from a naturally aspirated V8 engine. It is taking the peak HP measurement and guessing how the drivetrain with perform throughout the run. If you are guessing how much the car and driver weigh then it is going to be even more unreliable. If you wanted a quick and dirty rough guide formula for a forced induction engine then you would need to alter the constant to better suit the power curve of a forced induction engine. The higher the boost the more the constant would need to be altered. At the end of the day such a simple formula will only be able to produce a rough guess. The further you deviate from the car described in the constant the more unreliable the guess. The Drag Race Pro computer model uses measured engine performance throughout the rpm range of the run and dozens of other variables to predict the expected performance. If there is a significant difference between the predicted performance and actual performance in a good run down the strip then it would be reasonable to assume that the dyno figures were inaccurate. See for yourself, put the dyno figures for a 500 hp naturally aspirated V8 and a 500 hp 3.0L turbo into the demo version of Drag Race Pro and see the difference in the predicted performance. I am not saying that the Drag Race Pro is the ultimate computer model only that it more comprehensive than a simple formula with two variables. http://performancetrends.com/drag_race_pro.htm At the end of the day if you are racing then the only measurement that counts is the timeslip or lap time and dyno is just an engine tunning tool. If you are into peak HP dyno competition and not interested in racing then the only measurement that counts is the peak HP on the dyno.
electric cars ill put a spanner in the works and ask about electric cars with low peak horse power but a broad range of consistent horse power. They produce good results on the drag strip given there hose power. Also what about the old school practice of boost spiking on the dyno. It was the only way to win a dyno comp back in the day and only cause they changed the rules to stop it . Most people focus on a peak not an average for there reading on a dyno. The drag strip need that power to be broader than a dyno does to be any good.
Where's your spanner? Electric motors are all about torque and the fact they can deliver max torque pretty much instantly. As we all know HP is just a function of torque (Horsepower = (Torque x Engine Speed)/5252) so if you have heaps of low down torque without having to rev hard.... You know what this thread is about right?
No matter how much horsepower your car has, if it can't put the power to the ground, it is not much good. Dyno's are great and everything... but when it comes down to it, if your car is not fast, it is not fast.
I'm saying each has its limitations trying to compare a dyno to a drag strip is like trying to compare a hamburger to a pizza its close but not the same As far as American dynos go you know the Americans, everything is bigger and better over there.
