Common Race Car / Engine Calculations
Discussion
I am a computer programmer by day. The company I work for have introduced this new policy whereby between projects we can work on developing personal software projects in order to test out new technologies.
I want to do something car releated (unsurprisingly) and was thinking of writing some calculators/forumlas for common problems that have to be solved when setting up race cars / building engines etc etc.
Can anyone give me any ideas of common problems that have to be solved/calculated? I can work out how to do the calcs myself I just need some ideas.
I want to do something car releated (unsurprisingly) and was thinking of writing some calculators/forumlas for common problems that have to be solved when setting up race cars / building engines etc etc.
Can anyone give me any ideas of common problems that have to be solved/calculated? I can work out how to do the calcs myself I just need some ideas.
I've been looking around at what software is currently about. I've seen some where you can put in the dimensions of conrods, pistons, valves, camshaft profiles etc. and it gives an estimated power and torque curve for that engine. Think I might start having a go at that. Not sure where to start though so maybe time to go to the library and get some books!
I suspect you would need to estimate several efficiencies to create a model - which would have a very significant impact on the accuracy on the predicted power/torque. Companies would empirically find these efficiencies by testing a variety of engines on a dyno.
In effect, the program will be a parametric model fitted to experimental data. Without experimental data, you would not be able to tune the model.
That being said, if you had figures for your drivetrain (from the manufacturers testing), injectors etc etc you might be able to give it a go?
In effect, the program will be a parametric model fitted to experimental data. Without experimental data, you would not be able to tune the model.
That being said, if you had figures for your drivetrain (from the manufacturers testing), injectors etc etc you might be able to give it a go?
fatjon said:
one I would like is to work out the flow rate required in a water pump for a given engine and radiator efficiency.
If you had the temperatures of the ambient air, radiator efficiency, pipe diameters/lengths and heat output of the engine, this would be very achievable. Grab a heat transfer textbook - shouldn't take too long. You could try to verify your figures by carrying out the calculation on several existing cars to see what safety factor manufacturers use....alephnull said:
I suspect you would need to estimate several efficiencies to create a model - which would have a very significant impact on the accuracy on the predicted power/torque. Companies would empirically find these efficiencies by testing a variety of engines on a dyno.
In effect, the program will be a parametric model fitted to experimental data. Without experimental data, you would not be able to tune the model.
That being said, if you had figures for your drivetrain (from the manufacturers testing), injectors etc etc you might be able to give it a go?
Yes I thought about testing and proving the model with experimental data. I am sure I will be able to get hold of some data from some where. I think if I can get a basic model for calculating torque based on the engine dimensions first and use assumed values for volumetric and thermal efficency and expand from there. I can then add in losses into the cooling system and the effects of valve area and head design etc on VE.In effect, the program will be a parametric model fitted to experimental data. Without experimental data, you would not be able to tune the model.
That being said, if you had figures for your drivetrain (from the manufacturers testing), injectors etc etc you might be able to give it a go?
I've got Heywood's Internal Combustion Engine Fundermentals which has lots of complex equations so will have a good read of that.
I've written a fairly sizeable spreadsheet (only in Excel, eventually I get round to putting it into Matlab) that encompasses:
Brake setup - Caliper force, line pressures, servo assist, axle torques, forward weight shift and resulting bias requirements.
Gear ratios - Maximum gear speeds, shift points, wheel torques, diff vectoring.
Dampers - Natural frequencies and their required damper force/velocity curves.
Load transfer - Calculate dynamic corner loads for given steady state lateral acceleration. Working in incorporating this into a combined longitudinal/lateral acceleration at the moment.
Suspension geometry - Doesn't calculate anything, more some data recorded from a 3D model.
Engine data - Piston velocities (mean and max), primary/secondary/combined accelerations, gas volume/pressure/temperature, thermodynamic cycle and a predicted torque output for any given VE. Calculates forces on piston wrist pins at TDC, accelerations away from BDC and TDC and BMEP.
Engine geometry - Calulates piston to deck clearance, capacity, clearance volumes, static and dynamic compression ratios, some basic camshaft and headflow data still in progress.
Engine harmonics - Work in progress.
It's probably riddled with errors and pretty basic, but it's been in work since 2008 and will continue to grow as I constantly update and refine the model. Some ideas for you though!
Stuff I would like to do in future, tyre models (got a basic load sensitivity curve so far), downforce/drag, proper calculated 1/4 mile times taking into account gear ratios, drag etc. Eventually I would like to be able to predict the time taken to complete a given course, but that is probably years off yet, I'll most likely get bored before then.
I would love to incorporate all this into a phone app but I have no programming background whatsoever.
Brake setup - Caliper force, line pressures, servo assist, axle torques, forward weight shift and resulting bias requirements.
Gear ratios - Maximum gear speeds, shift points, wheel torques, diff vectoring.
Dampers - Natural frequencies and their required damper force/velocity curves.
Load transfer - Calculate dynamic corner loads for given steady state lateral acceleration. Working in incorporating this into a combined longitudinal/lateral acceleration at the moment.
Suspension geometry - Doesn't calculate anything, more some data recorded from a 3D model.
Engine data - Piston velocities (mean and max), primary/secondary/combined accelerations, gas volume/pressure/temperature, thermodynamic cycle and a predicted torque output for any given VE. Calculates forces on piston wrist pins at TDC, accelerations away from BDC and TDC and BMEP.
Engine geometry - Calulates piston to deck clearance, capacity, clearance volumes, static and dynamic compression ratios, some basic camshaft and headflow data still in progress.
Engine harmonics - Work in progress.
It's probably riddled with errors and pretty basic, but it's been in work since 2008 and will continue to grow as I constantly update and refine the model. Some ideas for you though!
Stuff I would like to do in future, tyre models (got a basic load sensitivity curve so far), downforce/drag, proper calculated 1/4 mile times taking into account gear ratios, drag etc. Eventually I would like to be able to predict the time taken to complete a given course, but that is probably years off yet, I'll most likely get bored before then.
I would love to incorporate all this into a phone app but I have no programming background whatsoever.
Edited by Kozy on Wednesday 4th May 13:21
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