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CAE Tools for Car Performance Modifications?
RevHead asks: "Although after-market performance modification of cars is a discipline which claims a significant following all over the world, most of the information available on the topic tends to be more of anecdotal nature. To add to this and the plethora of conflicting information out there,
most of the tips and techniques tend to be of 'do it and see if it works' type of experimentation. I am interested in the simulation approach prior to actual experimentation to get a decent picture of what to expect during the experimentation phase, which IMHO should be safer and more cost-effective. Has anyone resorted to this approach (successfully) when it comes to engine modification, suspension design, aerodynamic performance and emission control? If so what software is available for these tasks? Which are the most popular/most effective? Does anyone know of any public-domain automotive engine models available for CAE applications such as Catia and ADAMS?"
These guys make a great one... Does nearly everything you could want I belive. I do not know if it does engine calibrations but it does most of your design work for you. It's great for engine and suspension building.
http://www.rapidline.com/calc/
Vote early. Vote often. Vote CowboyNeal.
DIY EFI is somewhat related, you will find tons of information on fuel-injection systems, with an emphasis on GM products. The mailing list archives go back about 5 years, with people posting from all different backgrounds, including Ford engineers.
Modern cars have, almost without exception, OBD-II interfaces. I'm surprised that more people have not made low cost adapters and software to use for doing telemetry and data-logging.
If you want an adapter, you need to spend over $100, probably over $300. Software can cost the same.
Where are all the sourceforge projects? Where are all the $20 in parts designs for hooking your laptop to your computer? C'mon!
There's some software here:
http://www.gmecca.com/byorc/
though I doubt that it'll do what you're looking for. AFAIK, there's no one who's able to put together detailed enough models to truly simulate a production car.
For example, if you wanted to see the result of changing spring rates, you'd need to know the exact suspension geometry and parts, materials information on the metals used in the arms, flex characteristics of all bushings, assumed frictions of all moving parts, and likely more stuff (I'm not an automotive engineer, I just play one on the weekends). And this likely would be one of the more simpler analyses.
For example, I would guess that modelling properly something as commonplace as an exhaust replacement would be ridiculously complicated. Since you'd be optimizing flow through the engine, you'd need to understand flow details of all the components in the stream. I can't see any of the auto manufacturers releasing this information to the public, or any way for budget-limited hobbyists to obtain it.
Finally, you could probably forget aerodynamic modelling without a 3-d CAE model. That's all black magic there. I have, however, considered putting the 1:18 scale model of my car into a 1:18 scale windtunnel...
-sg
It's actually not hard to read ECU ODB-II interfaces -- so easy that a little time spent googling can find howto's -- the big problem is that the code for re-programming the ECU is not available freely.
:(
If there was a good programmable ECU, like this one, available at less than $1200 that worked with 99% of all new cars, it would be worth buying. The problem with AEM's unit is that they have major difficulties keeping up with automatic transmissions on new cars, so if you own a 2002 auto, no joy for you. Oh, the other problem with them is that they aren't legal for on road use. heh.. but that's a minor setback, neither are half the aftermarket exaust systems that people have on their cars.
I think I'm going to tell my next car dealer I want an open-source car.
As I'm sure you've figured out, predicting performance can be excruciatingly difficult on a system as complex as an automobile - this is why extensive testing still ensues all designs in the Automotive world, but that doesn't mean that the commercially available CAD/CAE tools available aren't useful, just that there are too many variables and too little available computing power to model up a whole car and know exactly how it will perform.
Balpark numbers on subsystems can be had with some general purpose CAE design tools(Pro/Mechanica, Dynamic Desiner Motion, Visual Nastran, & Working Model are most common). If you are running on something less than a Cray, these will all require you to simplify your desings - thus the ballpark numbers. I'm looking forward to the day that I can open up a multithousand part assembly, run an FEA project, and have results in less than an hour - all on my desktop workstation. Right now something as simple as a MiniBaja vehicle or FormulaSAE chassis can easily take over 16hrs to run through a single FEA solution on a modern dual processor X86 system. BTW - if you are still in college, SAE Student competitions are a fantastic way to get some experience on how to make a car go.
A great tool that is known to produce very accurate predictions for engines is Desktop Dyno (sorry URL not handy). But again, it wants simplified parameters (not physical geometry), so the program will only be as good as the numbers you feed it, on the plus side it has a good part database so aslong as you stick to COTSH you will get accurate results.
MathCAD and Mathmatica are also very useful, but requrie strong engineering knowledge to be useful, again it all comes down to the results being only as good as the numbers you feed it.
The two big ones you mentioned (Catia and ADAMS) are also fantastic tools, but are both expensive and complex enough that unless it's your job (and you get constant training), you probably won't ever become useful with them - The world of mechanical simulation isn't as well documented at the book store as even the most obscure programing methodologies.
You make a lot of assumptions.
I know plenty of auto related companies, and I can tell you that it's far from "guesstimation". They don't just go off half assed and do something, there is a lot of engineering principle behind their products.
You asked about aerodynamics, engines, and mechanicals. In each of these areas there is a lot of work.
Aerodynamics is one of the most visible parts of design, and there is very little in the way of guessing (except, umm, for those tasteless wings and stuff that people put on their cars). A good source of information on Aerodynamics can be found via books. Specifically:
Fiberglass & Composite Materials: An Enthusiast's Guide to High Performance Non-Metallic Materials for Automotive Racing and Marine Use
by Forbes Aird
Aerodynamics for Racing and Performance Cars
by Forbes Aird
Competition Car Downforce: A Practical Guide
by Simon McBeath
Race Car Aerodynamics: Designing for Speed
by Joseph Katz
I have the Aird books, and they're very good.
Mechanical engineering is well understood and followed, especially by Cal Poly. The FSAE contests are a great proving grounds for designs.
Books by Forbes Aird and Carroll Smith are really good points to start with. The Smith books are phenomenally thorough and put you in awe. That guys has FORGOTTEN more, than most people KNOW. The Aird book is more down to earth and easier to read than the Smith books, both authors are tremendously entertaining.
Here are some books:
Race Car Chassis: Design and Construction
by Forbes Aird
Tune to Win
by Carroll Smith
Carroll Smith's Nuts, Bolts and Fasteners and Plumbing Handbook
by Carroll Smith
Engineer to Win: The Essential Guide to Racing Car Materials Technology or How to Build Winners Which Don't Break
by Carroll Smith
How to Make Your Car Handle
by Fred Puhn
For engines and mechanical systems, I find that periodicals on the subject are very informative. I learned most of what I know about engines from reading Mustang magazines. There are books out there on rebuilding engines and performance.
Here are some good books:
Turbochargers
by Hugh MacInnes
Mustang Performance Handbook : Engine and Drivetrain Modifications for Street, Drag Strip or Road Racing Use. Covers All Models of the Ford Mustang, 1979 to present.
by William R. Mathis
Ford Fuel Injection & Electronic Engine Control : All Ford/Lincoln-Mercury Cars and Light Trucks 1988 to 1993
by Charles O. Probst
Fuel Injection: Installation, Performance Tuning, Modification
by Jeff Hartman
And finally, if you want to do engine simulation on the bench, err, computer, check out Desktop Dyno 2000. It's from Motion Software, costs $50 with the Cam-Disk CD (over 2000 cam profiles). It's a great program, however like all software, garbage in, garbage out. If you expect to get reasonable data from the program, you must supply it with reasonable data.
The ODB-II spec cost $85 from SAE and the shop manual for most cars has the rest of the information you need. Now shop manuals are a bit hard to find, but a little googling and you should be able to find one for your car.
I have the SAE book and I have ordered the shop manual for my car (will be delivered in a week). I also have an order in for a DeltaDash unit (an excellent OBD-II interface and software which works with most any Subaru), but the dealer is out of stock.
You sound way into it.. My suggestion: Go work at the big three.
:-(
:-(
But first, hit the search engines. There's so much freakin' info out there now. Also, the SAE technical papers are an awesome resource. However, they are typically expensive. At the big 3, we had the complete set in our research library and I could check them out 50 at a time. What a library..
Don't miss what is being done in the Formula SAE programs at universities around the country and world (FSAE). That is an incredible program and competition.
I took a systems job at one of the big three. I'd always had a strong interest in cars, but it grew *way* out of control in that environment.
I had a $60K workstation and access to all of the goodies - both the commercial stuff and the proprietary code. Today, your average PC has more than enough power to run these types of simulations.
I used ADAMS Vehicle in those early days for my kinematic suspension modeling.
Much more interesting to me were the proprietary engine simulation tools. Those were difficult to learn to use, but extremely powerful. Constructing an accurate model is a lot of work. Millions of dollars went into that company's engine sim development.
I regularly used those tools to study my engine. Serious geek-fest. Most of my geek friends just did NOT get it.. Search for Navier-stokes.
They had an 'optimizer' for the simulator that would 'wiggle' selected variables and find the best combinations for a particular goal. I found their optimizer somewhat cumbersome and ended up scripting my own (this all ran under UNIX). With this I could optimize valve event timing, and intake and exhaust dimensions. I also decided to develop my own graphing and reporting scripts for gnuplot. Of course all of this was on my own time and was done over a very long period.
I had wanted to use the CFD tools to model the airflow through my cylinder head ports at a more detailed level, but didn't get around to it before I moved on.. It was just a lack of time (not tools) that prevented me. I had gotten as far as pulling silicone molds of my ports and had them laser CMM'd. Funny thing is, the company did not get around to doing port CFD for another year (had I not been out having fun or something, I might have been the first their).
Eventually, I moved on
A year later, I ended up wanting to develop a traction control system for my race car. I decided to simulate it, knowing that such development would likely eat some pistons. I ended up writing an engine and chassis simulator in support of the project.
This simulator used the torque curve from my engine simulations, dyno runs and data acquisition as input. I used Mitchell's book to develop a simple tire traction model, etc. It was Newton physics coming back to haunt me and probably the funnest program I've ever written. Pretty simple code.
William Mitchell's _Race Car Vehicle Dynamics_ is considered a modern bible. It is *awesome*. Since the original publication Mitchell has released some of his software. I haven't checked the code out.
Gordon P. Blair's _Design and Simulation of Four Stroke engines is also excellent. His two stroke book is also considered a bible. I believe he has released simulation code for both.
Both are available via the SAE.
Of the two, I consider engine simulation a far more challenging problem. Most of the commercial simulators are *toys* and fairly crude. However, they can still be very useful.
Of those available, Ricardo's WAVE is reputed to be among the best (definitely not a toy) and is one of the few that would be used by a large manufacturer. Word on the street says it is a ripoff of an early version of a big-3 simulator, but that is just a rumor.
RaceTech magazine has published some good info on suspension simulation and one of the authors, Mike McDermott is a strong proponent of open sourcing his tools. Here's a link to get you started: http://www.mgbv8.co.uk/frontsus.htm
Along the way I learned to be a pretty good fabricator and welder. I have a pretty decent metal shop with a large 2 axis CNC mill and a Logan 12x48" lathe. The lathe is in the laundry room.
I cannot tell you how much this car-hacking improved my skills and abilities as a system engineer and architect. I still believe that the most complex and challenging projects of my career have been on my own race car (and oh BTW, you die if you get it wrong). So I absolutely encourage you to dive in, hit the books, whatever floats your bowl.
Today, I drive a Z06 Corvette and am Completely satisfied. I can build a car with better performance, but not with the *refinement* that car has. My quicker, faster, more nimble, louder and more violent road race car just isn't the same anymore, big slicks or not
The Unversity of Michigan Transportation Research Institute has some good tools you may want to look into.
http://www.umich.edu/~driving/sim.html