Z,
You think the main reason that 4WD is better is that it yields more regenerative braking?
I.....I......I......
Disagree.
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Z,
You think the main reason that 4WD is better is that it yields more regenerative braking?
I.....I......I......
Disagree.
Those transient issues which hurt turbo performance also hurt NA performance. The engine is doing the same job, so why treat the peripherals differently? If the rules were to place the throttle body after the resitrictor for all types of induction, then turbocharging would be a more difficult choice. The current proposed rumor highly biases a turbo choice for powertrain in the future.Quote:
Originally Posted by apalrd
No, Bemo. But that is kind of the point of creating a dialogue on the forum, correct? The unofficial FSG rules were removed after they were leaked onto the forums and the community was able to respond, both on the forums and in formal letters of complaint.Quote:
Originally Posted by Bemo
I agree. But the Americans are who suffer more than the Europeans with the late rules. If you are an American team wishing to compete in Europe and at Michigan or Lincoln, your car needs to be running 1 to 2 months earlier than the Europeans. That is a lot of time, which is why we are well into our development for the 2015 season. We are also involved in providing feedback for some of the proposed rules.Quote:
Originally Posted by Dunk Mckay
Yup. And what happens when the oil supply runs out? Like in a high-G situation on an engine originally developed with a wet sump? If the turbo is always removing the oil from itself with vacuum by dumping it into the intake, if it isn't supplied with oil it will overheat.Quote:
Originally Posted by GXP_Matt
I am not worried about turbocharging an FSAE car. I have access to resources which makes it possible for me to try different things and brake a few engines getting to a good turbocharged system. For a smaller team, however, creating a good working turbo system becomes yet another barrier preventing upward motion in the FSAE classes.Quote:
Originally Posted by GXP_Matt
I like the risk in racing. Go to the pits of any circletrack race and you will quickly get run over by a 3500# car driving 20mph with no clutch. The organisers of the event are worried that fresh people to racing won't know how to operate dangerous devices like race cars in a safe manner. Guess what FSAE is full of? Thousands of 20 year olds who have never gone to a race track and built their first car. If you are concerned with litigation than you have to cover your ass. Safety rules and other preventative measures make sense when you stand in the organizer's shoes.Quote:
Originally Posted by Mumpitz
Thanks for the photos Matt. Everything looks pretty wedged in. Do you have any data about the ambient temps in the engine compartment? We put peak temperature stickers everywhere to track the hotspots for cheap.Quote:
Originally Posted by Mbirt
GFR's simulations give us a lot of guidance. I have been speaking for myself and not for the team. If turbos happen, it just means that I get a bigger budget and new toys and more people dedicated engine development and engine sponsor resourcing. I have had potential sponsors turn me down for sponsorship because I was not running a turbocharger.
I think that changing up the turbo rules would need to be couple with a rule creating separate classes. A small and underfunded team working against their university is never going to be able to compete against turbo-charged hyper-aero cars. But as an organiser you can't simply remove all of the fun and learning possibilities surrounding aero developement and engine development. It would turn FSAE into Baja, which is just a parade of the same car driving around the track testing to see who has the higher quality construction.
It could, depending on the wording of the rules. I think that's what the plenum volume limit tries to fix. But I don't like how difficult plenum volume is to measure. A turbo also doesn't just have the time delays of filling the manifold (which can be helped with transient controls and ETC, NA or turbo), they also have time delays of spooling the turbo, and building boost to whatever high pressure the team wants to run. A supercharger does not usually have this issue as it can build boost without significant exhaust mass flow.Quote:
Originally Posted by Swiftus
Maybe the rules should allow the throttle to be downstream of the restrictor and compressor but require it to be close to the compressor? Or the plenum volume restriction should only apply to the space between the compressor and throttle (allow additional, unmeasured plenum volume between the throttle and engine?)
We currently run software/calibration changes to help with the filling delays of a 4.5L plenum (on a 450cc engine).
Uh, if you can't supply pressurized oil to the turbo then you'll have bigger problems on your hands very quickly, like a spun rod bearing and after that some unintended engine block ventilation...Quote:
Originally Posted by Swiftus
I don't think you understood my point that the proposed turbo rules make it EASIER on smaller teams, since the installation is simplified. A small team could slap a turbo running a few lbs of boost on an un-optimized engine package (maybe even intentionally compromise the engine for weight savings) and be making more torque than a fully built and CFD optimized NA engine of a well-funded larger team.
Wherever a volume is set for the plenum, it is going to add a step and therefore more time to tech inspection. At every competition without a dedicated scrutineering day, it will be adding more time onto a process which already cannot be completed within the allotted amount.Quote:
Originally Posted by apalrd
...which happens quite often in FSAE?... How many cars complete Endurance? Autocross? Skidpad?Quote:
Originally Posted by GXP_Matt
I did understand what you said. And for a no more effort or time but a lot more money, a well funded team could make more power for less weight without any compromises in safety or performance. Turbo manufacturers would be having a field day because of the huge demand for tiny turbos! 'Custom turbo sized for a 250-610cc engine you say? How much are you willing to spend?'Quote:
Originally Posted by GXP_Matt
This point's intent was to show that making turbos easy will simply widen the gap. If it is currently a lot of effort for small gains, than imagine the same amount of effort for huge gains? Does the small team have the resources to try and keep up with the big teams?
I am all for making the competition more interesting with the easier implementation of complex technologies like E-throttles and turbochargers.
BTW, what do you do at BorgWarner Turbo Systems?
My thoughts exactly. For someone who comes on here and calls all current Formula students, and I quote,Quote:
Originally Posted by stever95
Mr. Z would understand the simple Dynamics problem comparing the traction loads available for FWD, RWD, and 4WD configurations on a given vehicle.Quote:
Originally Posted by Z
Thinking out loud, with the electric cars I've seen running a Motor-on-Hub arrangement, wouldn't the inertia losses on a 4WD Electric car be lower than on a 2WD Combustion car? In the electric car there's another set of wheel/tire/hub to turn in addition to the four electric motors, however that is offset by not having to operate an engine/transmission/drive chain/differential/driveshafts, intuition would suggest that combining lower inertia losses and a higher tractive potential for an equivalent power level would give higher acceleration, all other things being equal, no? Someone please correct me if I'm wrong.
Z,
We've gone down this road before a while ago on a different thread, discussing drag strip methods for the FSAE acceleration event.
Considering your third question, you may be 'confident [we] will all fail', but I remember your explanation concerning inertial resistance to pitch motions about the rear-wheel.
However, in order for resistance to pitch motions to come in to play, there must be pitch motions. In other words, there must be enough grip off the line to lift your front wheels in the first place.
You basically agreed to that, by saying we should assume a start line acceleration of 2.5g.
Like I said before, I don't see that happening with 'normal' tires on a 'normal' track. 1.5g might be doable.
You still haven't told me where you do your tire shopping.
I'm sure there are things we can learn from drag racing, but I feel you're a bit overeager to draw parallels.
This is how sticky a drag strip is:
https://www.youtube.com/watch?v=x5wQajhGaeI
so this:
http://bit.ly/Uj6YRP
comes as no suprise.
On the other hand, I don't remember seeing cars in a circuit race class lifting their front wheels.
Again, no surprise, they'll just have their rear wheels spinning instead.
If you want to make a point about how slow and boring current FSAE car designs are, and how stupid 4WD is, please point out a single race car that can go around corners (i.e. one that doesn't do its runs on a duct tape track, using tires with 9.5" walls at <0.5 bar that last 3km at most), and that accelerates quicker to 60km/h than the fastest 4WD electric FSAE cars.
Regarding the weight distribution on 2WD (combustion) cars. If you only look at acceleration then yes, you want to design a static weight distribution as close to the driven axle (usually rear). That's why dragracers look the way they do. However, there are 4 dynamic events in formula student, where 3 out of 4 require some sort of lateral force creation. With minimal load on the front axle, minimal total lateral force is created needed for cornering. I guess every team that has some sort of lap simulation will agree that the average speed during these 3 dynamic events is significantly increased by increasing cornering speed. I won't mention F1, ok maybe I did. Therefore increasing points obtained significantly. So yes, you take a slight hit on 75 points from acceleration, but you gain a lot more on 50+150+300=500 points. Hmm... hard decision.
Then you have the issue of balancing the car for these 3 dynamic events. Even if you can get close to a good setup, a slighty hickup will cause the car to oversteer with a very rearward CoG (ask the people from the DUT11 for example). Yes drifting is a lot of fun, but it's also not very quick around a corner. As added bonus you'll wear out your tires quite rapidly, which is costly at ~150 dollars a pop.
And then I haven't even mentioned tire load sensitivity yet...
Note: if anyone has 2.5G tires I will trade them for ours :)
Rear weight bias in fsae has definateley been done quite well by maryland
https://fbcdn-sphotos-g-a.akamaihd.n...81080726_n.jpg
as far as lateral force generation goes, if I remember correctly, there weren't many SAE cars faster around a skid pad, or scca autocross. (even though it was heavier than most)
transient response and the length required to get the weight distribution could be improved with a custom, short engine/driveline as discussed by other in this thread.
One problem with the rear weight distribution which will be getting worse with the proposed rules is trying to get the aero balance to where it should be. In my non-aero-person opinion, with current packaging "maximum" downforce on a minimum length car would likely occur with an aero balance pretty close to 50:50. With these new rules who knows? Maybe some low-powered aero teams might show up with 65% front weight distribution and skinny rear tires to maximise total balanced downforce? (i am choosing to keep the questionable claims of creating massive underbody downforce in their other threads)
It will interesting to see if any of the top teams come up with something radically different in these new rules
Daniel,
If your theory on axle loading held true, there would be no point to reducing mass. Minimal axle loading may create minimal lateral force, but there is less mass to move. See the Deltawing concept.
Having done quite a bit on turbo tuning with the UoW cars, I agree with GXP_Matt that turbo implementation would be easier. Drainage was a frustrating problem and on some cars resulted in much victory smoke. Also, the amount of work required to make the turbo provide a gain was huge. This doesn't seem to be appreciated by many, who think it's just a matter of whacking on a turbo and boosting like hectic. With the proposed intake path, it would be possible to do just that. I don't see this as a problem, because it forces teams who go down that path to realise the other requirements for successful turbo implementation (assuming the oiling and some lag issues have been resolved by the new layout). I can go through my take on these requirements if anyone is interested, but suffice to say they are applicable to real world situations.