Duke57TT im still inclined to this opinion also, but i can see some aspects and elements of the % argument also. But i still cant get my head around big hp cars losing soo much power to the ground. And another thing, when people work out their hp from their mph, the hp they are getting is bhp and not rwhp?? Thats how all my v8 mates work their stuff out. RWhp or RWkW never gets talked about. Its always at the motor.

Quote: Originally Posted by skybt1 Its always at the motor. Yup!

Too much variance in Chassis Dynos, the most acurate way to test/tune a motor is on the engine dyno.. if i was building a new motor, i would put it on the engine dyno first! Actually, i might do that with my new motor.. it wont be making much power, but it's always good to know. If i can get a engine HP figure, then a RW figure, we can all see how much i lose through a T700 and 9 inch Some original photos have not been recovered yet.

Quote: Originally Posted by Epitaph Too much variance in Chassis Dynos, the most acurate way to test/tune a motor is on the engine dyno.. if i was building a new motor, i would put it on the engine dyno first! Actually, i might do that with my new motor.. it wont be making much power, but it's always good to know. If i can get a engine HP figure, then a RW figure, we can all see how much i lose through a T700 and 9 inch There is way too much variance in chassis dynos, i fully agree here. You can drive down the road and either gain or lose 20 or 30kw. Will be interesting with your results from motor to wheels. Some solid evidence providing the chassis dyno is not on laughing gas. Whats made you go the T700? Is it for an rb? Some original photos have not been recovered yet.

Quote: Originally Posted by EAT-30T So idealy this should trap 100-105mph... (not 100% sure on his exact weight?) If you go to the track and trap those speeds then your about on your money.... I think alot of you people forget about CFM .. If you can push more air in without restriction then of course you will make more power and not necesarrly show a bigger PSI reading. mine did 101mph with 171rwkw now does 108 with 191rwkw

I havent even bothered reading much of this thread at all because what does it matter. The true quarter mile is a black strip of road that is approximately 400m long, and it has a timer would you believe. Dynos are useful for tuning but cannot always give an accurate indication of a cars 1/4 mile time. Picture this......2 cars which have exactly the same dyno rwhp figure of 300rwhp. Now think that 1 of the cars have some extra mods which dont increase rwhp at all such as; 4.11 diff instead of 3.45, 3500rpm Torque Converter, Transbrake (which can help considerably on the strip (I can talk from experience), Aftermarket Engine Management, Executive Model instead of Heavier Calais Model..........Now just guessing, but the car with all the mods done (but still has same peak power) im guessing will cover the 1/4 mile quicker, and it could be substantially quicker. Just incase people are going to comment and say engine management will help, well i agree, but some dont understand why. If you have a car which needs timing adjusted so as not to detonate up the top in the revs and peak power range, then you are compromising the mixtures down lower in the range. Whereas with engine management, you still may have the same peak power as someone else, but your power will be delivered most likely quicker and more torquier and at the precise mixtures starting at idle, all the way up to redline. So really, the dyno is a useful tuning tool, and can give you a guide of your 1/4 mile, but with so many other variables, and with so many fudged dyno figures or high reading dynos, then you cant truly expect to know the capability of the car until you take it down the strip and get a time. I would prefer a great quarter mile time rather than a high dyno figure reading. And those that have hp that seems alot lower than others, yet the 1/4 mile times are very quick, then i guess there is 2 things that it could be.....1. the car is a freak and it just happens to be ballistically quick on the strip with low numbers or 2. go to another dyno shop or even a couple, and then compare the readings and you just may be surprised.

Quote: Originally Posted by Epitaph Duke57TT did you read the thing i posted at all? Heat is power. We're talking about it being a percentage because of the Heat/Stress the extra power will put on a component, therefore losing more of the power. I'm not gonna argue it black and blue, because it is something that everyone has a different opinion on. So for my black and blue argument 200kw at 17% is 34kw but at a 1000kw it would be 170kw. 170kw of heat dissapated through a driveline is alot of heat. Put your hands near a 2200w heat element and then tell me your driveline is dissapating 170kw. Enough to heat about 30 houses. To really understand what is happening you would have to calculate all the cross disectional tension and reflexion of a driveline and its contact surfaces of each individual component. Way beyond what most people can understand. So once you have calculated the torque required to turn the mass, the frictional forces working against the engine, inertia and the ten thousand other calculation to make an accurate assessment of the driveline and its power sucking ability then you may get close to what you where looking for. For the record No dyno whether is a chassis/hub or engine dyno it accurate. They are just a tuning tool. Every brand uses different calcualtions to measure the output. MPH to BHP is just a guesstimate at your HP level. It will be slightly under what you actually have as it doesnt and cant take into consideration what your parsistic losses are through your driveline. every car is different and the base calcs are not usally changed to reflect this. If you want a happy dyno reading take your bling rims off and whack some 15in rims with skinny tyres on it. Oh and some thin diff and gearbox oil.... the later model commys in the T56 boxes use auto gearbox fluid.

Thanks for that, really interesting read Some original photos have not been recovered yet.

im pretty confident that its a percentage as the article states. you have alot of heat coming from 1000 kw engine so your going to lose a percentage of it through the driveline but i may be wrong

its definately a topic of many varied opinions. I was convinvced it was a figure but now im unsure between being a figure or a percentage.

dynos are a tuning tool.who give a **** about hp readings.run some times.****.dyno comps are for testing metalurgical streght of blocks and components and for knobs that cant drive.

yeh it can be a figure or percentage which ever way you look at it but it will be different depending on the power, gearbox etc of the car

there has to be a basic figure as well as a percentage, otherwise how do you explain a 1hp electric engine not being able to turn a driveline at all? If you go by percentage only it should turn them and make say .8rwhp

Quote: Originally Posted by ATMO_BT1 there has to be a basic figure as well as a percentage, otherwise how do you explain a 1hp electric engine not being able to turn a driveline at all? If you go by percentage only it should turn them and make say .8rwhp Dead right^^^^ Every basically standard driveline in a VL will use about the same figure, but this figure will be different to the basic standard for a later model commodore or if it has been modified. I think where people get confused is that you have a VX GTS that make 300FWKW and then turns about 235-245RWKW. What the drivetrtain loss is can be expressed as a figure - 65kw or as a percentage of the total output 21%. Applying though that formula to a car that has been modified is wrong as you need to know 2 out of the three numbers to get a result. In this case when a car is modified you dont know the engines output and you dont know the extra energy losses through the driveline or if there is any. So you cant calculate engine power by quoting, figures you dont have. I know that kinda is hard to read but i guess you can sorta get the drift of what i mean.

Applying your example of the VX GTS for all cars in general, on average drivetain loss would be approx 20% manual and 30% auto depending on converter etc etc etc.... Me personally, i'd rather a nice healthy MPH reading at the end of the 1/4.

Quote: Originally Posted by ATMO_BT1 there has to be a basic figure as well as a percentage, otherwise how do you explain a 1hp electric engine not being able to turn a driveline at all? If you go by percentage only it should turn them and make say .8rwhp I never looked at the other side of the spectrum at 1 or 2 hp. Makes even more sense then looking at the higher side of the hp range. I think that by using percentages you get a rough idea. But at the end of the day each driveline is going to use a certain amount of power/energy. If a driveline sucks say 60kw and you tune an engine at 300kw and then 400kw then the same driveline will still only take 60kw to turn it and make it work. I dont think that there would be enough heat or possible increase in sound energy(if any) produced to make such a big impact on the rear wheel figure. Thats how im seein it anyway..

i can vouch for this car, if it is running at 6psi its an animal easily pulled away from me, and ive got a turbo conversion at 9psi with 600x300, 2 1/2 exhaust with a 3 inch cat.

It's all just a function of energy really. It most certainly isn't a single value and the variance in loss is small enough that you can consider it a single percentage. Say your car has 100kw at the flywheel, then you put 100kw through the clutch, it might slip 0.001mm radially, then you put it through the gears, each tooth might flex 0.001mm, then you have the dynamic friction in the bearings etc etc. All This transfer of energy and manifests itself in noise, heat etc. Now say you put 200kw through the flywheel, the clutch might now slip 0.002mm radially, each gear tooth flex 0.002 and so on. Now these things aren't all linear but once it's all calculated out it's pretty close. This is also an overly simplistic way to look at it as there are a lot more variables, but they all follow similar principles.

Quote: Originally Posted by theVLguy i can vouch for this car, if it is running at 6psi its an animal easily pulled away from me, and ive got a turbo conversion at 9psi with 600x300, 2 1/2 exhaust with a 3 inch cat. hey man thanks for the comment yer it was only on 6 psi aye i thought u would have kept up with me aye broke my gearbox on the way home from the coast that night aye lol Some original photos have not been recovered yet.