Simulation software for the Elan
Posted: Sat Oct 20, 2007 10:45 pm
Elementary simulation software for the Lotus Elan.
This whole thing started out quite innocently. Chatting with another Elan owner brought up the question as to the car?s possible top speed (with the tires and differentials available, an empty question). Well, a little work later brought a work sheet in which various vehicle parameters could be entered, and an estimate of the horsepower for a certain speed required was output. This is in worksheet ?Aerodynamic Drag?.
There is another spreadsheet in distribution that allows the user to calculate so-called optimum gearbox ratios (you can ask for a copy of this spreadsheet, it is too large to post). In any case, a debate developed about the optimum staging of gearbox ratios. So the suggestion was made that the aerodynamic drag work sheet be expanded to calculate acceleration times and thus allow ratio design to be optimized for minimum acceleration time.
Well, a little later, and various factors that affect acceleration were included, and a bunch of results tables and graphs generated that allow the obsessive and compulsive of us to determine the effect of various changes, even if they can hardly be discerned in real life.
So you can see the effects of different torque curves (low RPM torque vs high RPM power). See the effects of short shifting for different torque curves. See whether it is more beneficial for performance to increase the horsepower by 10% or decrease the weight and aerodynamic drag by 10%. And bunches of other things.
Posts in this forum have asked questions that can be answered by this spreadsheet, like what speed will my Elan do at X RPM, using Y differential ratio, Z tire size? What effect on performance will lightening the flywheel have? Even, in a tongue in cheek moment, what effect does the front bumper trim strip have on performance?
For most of us with daily drivers, these questions are of mainly academic interest. But if you are restoring your car from scratch, knowing the effects of some possible modifications can guide you in your restoration, whether you want an authentic appearance or are willing to make modifications. The Elan is a complex system, with a large number of sub-optimal systems dictated by the knowledge or economics of the day. One change may not have much of an effect, but identify and implement a second change, a third change, and there is the possibility of producing an Elan substantially improved over the original while using Chapman?s original design genius.
In any case, this is rather simple software, not that rigorously tested, that does not rise to the level available to F1 teams. But it has sort of opened my eyes about how different things affect performance. I hope that it improves your understanding also.
The spreadsheet is 1.8MB, so can't be uploaded in its original form. The spreadsheet is ZIPped. But LotusElan.net does not accept .ZIP files, so the file is renamed with a .XLS extension. After you download it, rename the file back to .ZIP, and extract the spreadsheet.
Be sure to tell me about invalid results, incorrect formulas, questionable assumptions, etc that always afflict the programmer. And also send me requests for enhancements etc.
Also, please send me other dynamometer curves, whether charts or tables. I will include them in the spreadsheet and post the updates.
And I am looking for camshaft lift curves, again either charts of tables.
If you modify the spreadsheet, please send me a copy.
Have fun.
David
1968 36/7988
This whole thing started out quite innocently. Chatting with another Elan owner brought up the question as to the car?s possible top speed (with the tires and differentials available, an empty question). Well, a little work later brought a work sheet in which various vehicle parameters could be entered, and an estimate of the horsepower for a certain speed required was output. This is in worksheet ?Aerodynamic Drag?.
There is another spreadsheet in distribution that allows the user to calculate so-called optimum gearbox ratios (you can ask for a copy of this spreadsheet, it is too large to post). In any case, a debate developed about the optimum staging of gearbox ratios. So the suggestion was made that the aerodynamic drag work sheet be expanded to calculate acceleration times and thus allow ratio design to be optimized for minimum acceleration time.
Well, a little later, and various factors that affect acceleration were included, and a bunch of results tables and graphs generated that allow the obsessive and compulsive of us to determine the effect of various changes, even if they can hardly be discerned in real life.
So you can see the effects of different torque curves (low RPM torque vs high RPM power). See the effects of short shifting for different torque curves. See whether it is more beneficial for performance to increase the horsepower by 10% or decrease the weight and aerodynamic drag by 10%. And bunches of other things.
Posts in this forum have asked questions that can be answered by this spreadsheet, like what speed will my Elan do at X RPM, using Y differential ratio, Z tire size? What effect on performance will lightening the flywheel have? Even, in a tongue in cheek moment, what effect does the front bumper trim strip have on performance?
For most of us with daily drivers, these questions are of mainly academic interest. But if you are restoring your car from scratch, knowing the effects of some possible modifications can guide you in your restoration, whether you want an authentic appearance or are willing to make modifications. The Elan is a complex system, with a large number of sub-optimal systems dictated by the knowledge or economics of the day. One change may not have much of an effect, but identify and implement a second change, a third change, and there is the possibility of producing an Elan substantially improved over the original while using Chapman?s original design genius.
In any case, this is rather simple software, not that rigorously tested, that does not rise to the level available to F1 teams. But it has sort of opened my eyes about how different things affect performance. I hope that it improves your understanding also.
The spreadsheet is 1.8MB, so can't be uploaded in its original form. The spreadsheet is ZIPped. But LotusElan.net does not accept .ZIP files, so the file is renamed with a .XLS extension. After you download it, rename the file back to .ZIP, and extract the spreadsheet.
Be sure to tell me about invalid results, incorrect formulas, questionable assumptions, etc that always afflict the programmer. And also send me requests for enhancements etc.
Also, please send me other dynamometer curves, whether charts or tables. I will include them in the spreadsheet and post the updates.
And I am looking for camshaft lift curves, again either charts of tables.
If you modify the spreadsheet, please send me a copy.
Have fun.
David
1968 36/7988