After stalling for a while now, I have so much more to do on this stinking Blog :p. Short and sweet: I have the suspension.
I have corrected some Natural Frequency calculations and applied new-found Motion Ratio information after working through bump/droop travel and empirically measuring the MR in the rear and front of the car.
AbarthSuspensionForm This is version 0.4. I replace all the links by the same name, so you don’t need to necessarily download the sheet from this particular post.
I have finished editing a quick video that I made when I saw an opportunity to run an HPSI Unichip Stage 2 on my car (once again!). I am currently using a Seletron ChipBox and definitely enjoy it’s additional boost, however, that HPSI tune literally wants to tear your face off any chance it gets.
The thing that I take away from the ChipBox is that it is very smooth power that is smoother than most other piggyback tunes that I’ve used (TMC, RRM). The Unichip, however, is a different breed from other piggybacks and can intercept and manipulate signal voltages more than a simple +/- so you can develop your own boost maps, AFR maps and further refine your tune. Of course, the Unichip is still ultimately limited to what the ECU will allow since the Unichip is not the top authority when it comes to operating the engine, that’s the ECU’s job. The TMC and RRM piggyback boxes connect to the Boost and MAP sensors (and a cam sensor for an undisclosed reason). Though, the ChipBox unit plugs into Boost and MAP sensors it also connects to the boost solenoid and I suspect that it is to assist in reaching its target boost levels. Thus, it removes one other trick that the ECU has up its sleeve when it wants to limit boost pressure.
Here is the video: YouTube Video
As I was making my How To video for the spreadsheet I tracked down a few bugs that left out the rear torsion bar and front stay bar contribution to roll stiffness and thus, impacted the Front Roll Couple calculation.
The updated form is here: AbarthSuspensionForm.
The YouTube video is here: Fiat 500 Abarth Spreadsheet How To
Years ago when I was studying Electrical Engineering at the University of Ottawa, I had the opportunity to dive into learning what makes your car go bouncy-bounce! (Or crash! and Bang!). I held a lead role for the proposal and research stages of designing a Formula SAE car for the purpose of competing against the Carleton Ravens team which by the way, is a very formidable and capable team that has both an IC powered car and an electric powered car!
One of the things I found when looking through the maths of suspension design was just how familiar all of the equations were to acoustics. When you look at a speaker and it’s physical characteristics, you look at things like Cms (suspension compliance), magnet force, surround excursion, damping factor and so on. A speaker is a really neat device btw and you should definitely look at it in detail.
I took on a personal project to develop some basic maths for the FIAT community, having noticed that there was a lot of guesswork and “try this, try that” going on. I knew from school and my acoustics design experience, that you can select a design target and direct your approach methodically without guessing.
It is without further ado, I bring you the v1.0 of the Fiat 500 Abarth suspension design spreadsheet! AbarthSuspensionForm The spreadsheet is directly inspired by the similar looking Fat Cat models on Fat Cat Motorsports’ website. The spreadsheet can be used to determine desired spring rates, target natural frequencies and oversteer/understeer characteristics. I’ll be posting a tutorial video to work through an example and posting that as soon as I can track down the time!