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Thread: V-Twin

  1. #21
    There are other 2 cylinder options.

    Honda makes a 470cc parallel twin
    Kawasaki makes 300cc and 650cc parallel twins
    Yamaha makes a 500cc parallel twin

  2. #22
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    Quote Originally Posted by Mbirt View Post
    EPM (Montreal) switched from a monocoque and Ape to Rotax DS450 and spaceframe this year and placed 14th at Lincoln (their first sanctioned competition of the year) to jump 222 spots in the FS-World ranking. I can't speak for them to attribute previous performances to problems with the Ape v-twin, but I did observe lots of trouble just getting it to start at several events.
    Yeah I was team lead at EPM last year and basically came to the point where the team was trying to make a cool car instead of scoring points. Me and my co captain decided to change that. Looked at what was available to us (BRP's racing department is two hours away from our school and I'd worked at BRP in the powertrain department for 8 months so sort of had a lay of the land as to the reliability of those engines), so that was a no brainer. As for the spaceframe, again mainly a question of available resources and team size(carbon is labor intensive, think sanding molds)

    Can't really say the Ape was the reason for our recent sucky years. More a question of team organization and management. However, I will say that we blew one engine on the dyno (overcooled water system and uncooled oil system meant we pushed the engine too hard because we didn't have an oil temp sensor at first). If we,d done that on the Ape, would have cost us an arm and a leg (that's 6000$ for you people who don't know Limb Currency).

    But I'm pretty sure with the guy that took care of the engine last year that it would have run anyway, just more expensive and more time consuming(the Aprilia needs a custom trigger wheel coz the stock one isn't great from what I understand). On top of that the Aprilia shop manual isn't great (read utter crap) and the alternator seal can really wreak havoc if you're not careful (all the oil that lubricates the piston and crankshaft goes through the alternator casing through a seal to the crank shaft, if you nick the seal while installing the alternator cover, you just blew an engine). On top of that, the starter motor is undersized so if your calibration is off and you,re not starting, you need at least 4-5 starters around the shop at all times. Overall the Aprilia is sweet on paper, just extremely expensive to run and very finecky. Just have to treat the aprilia like a race engine(ie change a shit ton of expensive parts ever so often). If you want to run it,, you need a solid team of guys to get the thing down to a Tee.

    As to starting the Aprilia starting issues, in our case, it was mainly a question of extremely crappy(read inexistant) engine calibration before 2013. Team was too focused on fabricating the damn tub and not worried enough about having a functioning car(back to those pesky management issues). That coupled with retarded fuel injector placement(wet the wall more than sprayed on the valvetrain)and a fuel pressure regulator that wasn't hooked to the plenum meant that it was a recipe for disaster(Again, keep in mind we were retards for a while).

    That pretty much sums up the question of the Aprilia.

    As an aside, one engine configuration that hasn't been discussed is a snowmobile inline twin. If you want a decent compromise, I think that,s what I'd do if i wanted something in the middle without engineering a crankcase. A Skidoo inline twin http://www.ski-doo.com/technologies/...gies/4-strokes 600 is around 40kg for 60 HP(1.333HP/kg). (that's only 6 kg more than their 450 btw). Say you make a transaxle for it that ways say 5-6 kg and you've got a pretty neat package. I know for a fact that RMIT ran the Phazer 500 inline twin for a while as well as sherbrooke. They're nice little engines. If you engineer your own gearbox, you can basically run it so the crankshaft is longitudinal which means your headers come straight out the side, avoiding the heat management around the gaz tank and other stuff that gets crammed under the driver seat that inevitably comes from a laterally oriented crank. The engineering workload og engineering a gearbox is probably less of a hassle than engineering a crankcase.(just reuse a gearbox from another engine. and make a case around it)

    Finally, as an answer to your original question(I know long way to get to the point). Yes they're a good compromise. As i recall, calibrating like retards we got something like 55Hp(or as I like to call it , the point of diminishing returns from a power point of view in FSAE(considering no aero)) out of the APE for 35kg(weight of a single). So they're awesome. They're as much of a pain to package as any other engine seeing as things tend to get tight no matter what. If that engine were easier to work with, it would be perfect. Low effort to get a decent amount of power, you can concentrate on other things while having a nice light package. Or go balls to the wall and put a turbo in to get a nice light package with as much power as a NA inline 4.

    PS: power to weight summary

    Single BRP = 1.22 hp/kg. (43HP - 35 kg)
    Inline twin = 1.33 hp/kg (60HP - 45kg with gearbox)
    Aprilia 550 = 1.5 hp/kg (53 Hp - 35kg)
    Inline 4 = 1.44hp/kg (80 HP - 55kg)
    Paul Charbonneau
    Formule Polytechnique Montreal
    2009 - 2012 - Suspension Lead
    2012 - 2013 - Team Captain
    2013 - 2014 - Suspension and Electronics Lead

  3. #23
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    We tossed around the idea of the Ski-doo/ROTAX 600ACE for a while since we had a few of them and experience on the snowmobile side. Its not a svelte engine by any means. 4 stroke snowmobiles are expected to be more reliable and fuel efficient than their 2 stroke brethren at the cost of some weight and power. From a fuel economy standpoint the 600 is hands down the best engine in the industry. However, like you mentioned it is like 90-100 lbs and doesn't have a gearbox. It is also incredibly tall (one of the other Kettering guys might have a reference pic next to a WR450). On the plus side, it is amazingly knock resistant when combined with boost and high ethanol fuels. If you did it right and relocated the dry sump tank (which is the backside of the motor stock) so you could lay it down a little bit, even if you coupled it with a CVT it would probably make a nice package for sure.

    For peak power out of it, FWIW, we were making about 85-90 hp at the crank, which seemed to be about peak for all the other teams running the same engine.
    Any views or opinions expressed by me may in no way reflect those of Stewart-Haas Racing, Kettering University, or their employees, students, administrators or sponsors.

  4. #24
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    Quote Originally Posted by RenM View Post
    To the technical side of things: slower burn rate is a geometrical thing. Simplified the burn speed remains constant. With a larger bore the flames travel longer.
    Sure you can turbocharge a single, but it wont work very well especially in fsae configuration. If you had taken your time and dig a little deeper than just the surface of this topic you´d know that in fsae conditions a turbocharger has to deal with hugely unfavourable circumstances.
    The overall massflow is very low, leading to small turbochargers. Small turbochargers do however always have a bad overall efficiency.
    Your exhaust gas flow is hugely pulsed as is your intake, requiring a large charge pressure.
    The dynamics in an fsae car are enormous. The turbo has to be accelerated in a very short period of time. For acceleration you need power, so you close your wastegate and your exhaust backpressure rises.
    Because of these points you will not be able to reach a positive pumping loop in an turbocharged fsae single, even though it is possible under different circumstances.
    I also wanted to show how unsubstantiated several of these points are, but I was getting way too into it and wasting too much time. So I'll keep it simple.

    1. Burn speed remains constant eh? The single-cylinder engine has a greater quench percentage of bore area area than a 600/4, so that helps with turbulence. High charge density is also possible with good intake designs that negate the effect of the restrictor on a pulse-by-pulse basis. We're not the only single-cylinder team running only 30 degrees max ignition advance at WOT.

    2. With an 85+ hp KTM and several fuel economy wins, tell Wisconsin that turbocharging a single doesn't work well in FSAE. I don't consider 65-72% compressor efficiency to be bad at all. And large exhaust pulses work great for quick spool, it's the boost creep due to insufficient wastegate flow that gets you.

    3. The "pea shooter" exhaust tips dirtbikes and ATV's come with stock are smaller than the turbine housing restriction--it's no big deal.
    -----------------------------------
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

  5. #25
    Quote Originally Posted by Mbirt View Post
    I also wanted to show how unsubstantiated several of these points are, but I was getting way too into it and wasting too much time. So I'll keep it simple.

    1. Burn speed remains constant eh? The single-cylinder engine has a greater quench percentage of bore area area than a 600/4, so that helps with turbulence. High charge density is also possible with good intake designs that negate the effect of the restrictor on a pulse-by-pulse basis. We're not the only single-cylinder team running only 30 degrees max ignition advance at WOT.

    2. With an 85+ hp KTM and several fuel economy wins, tell Wisconsin that turbocharging a single doesn't work well in FSAE. I don't consider 65-72% compressor efficiency to be bad at all. And large exhaust pulses work great for quick spool, it's the boost creep due to insufficient wastegate flow that gets you.

    3. The "pea shooter" exhaust tips dirtbikes and ATV's come with stock are smaller than the turbine housing restriction--it's no big deal.
    Many things work if you try hard enough, strive to collect data, and test to optimize.
    Steve Krug
    Wisconsin Racing

  6. #26
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    Quote Originally Posted by EPMPaul View Post
    As an aside, one engine configuration that hasn't been discussed is a snowmobile inline twin. If you want a decent compromise, I think that,s what I'd do if i wanted something in the middle without engineering a crankcase. A Skidoo inline twin http://www.ski-doo.com/technologies/...gies/4-strokes 600 is around 40kg for 60 HP(1.333HP/kg). (that's only 6 kg more than their 450 btw). Say you make a transaxle for it that ways say 5-6 kg and you've got a pretty neat package. I know for a fact that RMIT ran the Phazer 500 inline twin for a while as well as sherbrooke. They're nice little engines. If you engineer your own gearbox, you can basically run it so the crankshaft is longitudinal which means your headers come straight out the side, avoiding the heat management around the gaz tank and other stuff that gets crammed under the driver seat that inevitably comes from a laterally oriented crank. The engineering workload og engineering a gearbox is probably less of a hassle than engineering a crankcase.(just reuse a gearbox from another engine. and make a case around it)

    Finally, as an answer to your original question(I know long way to get to the point). Yes they're a good compromise. As i recall, calibrating like retards we got something like 55Hp(or as I like to call it , the point of diminishing returns from a power point of view in FSAE(considering no aero)) out of the APE for 35kg(weight of a single). So they're awesome. They're as much of a pain to package as any other engine seeing as things tend to get tight no matter what. If that engine were easier to work with, it would be perfect. Low effort to get a decent amount of power, you can concentrate on other things while having a nice light package. Or go balls to the wall and put a turbo in to get a nice light package with as much power as a NA inline 4.

    PS: power to weight summary

    Single BRP = 1.22 hp/kg. (43HP - 35 kg)
    Inline twin = 1.33 hp/kg (60HP - 45kg with gearbox)
    Aprilia 550 = 1.5 hp/kg (53 Hp - 35kg)
    Inline 4 = 1.44hp/kg (80 HP - 55kg)
    Thanks for the input, Paul. I was hoping you would drop in and tell us about the engine change.

    I've updated your hp/kg list with some real numbers achieved by teams. I've squeezed 90 hp out of a 600 ACE with turbocharging and E85 for another competition, so I've included that figure. It doesn't look very impressive stock at 60 hp and 40 kg. 35 kg is heavy for a single cylinder, Hondas and Yamahas are closer to 31-32 kg. 43 hp is also low, 50 is easily achievable, 60 can be had from 450 cc with some effort. Same goes for the Ape, one team has hit 78 hp.

    Single = 1.88 hp/kg. (60HP - 32 kg)
    Turbo single = 2.30 hp/kg (85HP - 37 kg)
    Turbo 600 ACE = 1.8 hp/kg (90HP - 50kg with turbo and gearbox)
    Aprilia 550 = 2.23 hp/kg (78 Hp - 35kg)
    Inline 4 = 1.64hp/kg (90 HP - 55kg)
    -----------------------------------
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

  7. #27
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    How much power do you need?

    If someone could make a graph of engine power on the x-axis and time/effort/resources on the y-axis and the compared it to the attached graph, engine selection would be pretty easy I would imagine!

    Attached graph is done in OptimumLap using the "default FSAE Aero car", which weighs 230 kg, has average FSAE aero and is using a CVT (to make comparison between different power levels more relevant), the car was run around the 2012 FSG endurance track.
    Attached Images
    KTH Racing '03-'08
    Dartmouth Formula Racing '07

  8. #28
    Hi,

    @EPMPaul: why is the stock Aprilia trigger wheel bad? We had no issues with the cam signal in the years we used/use the Aprilia (2009 until now)? The manual is not the best, but all torque values are given and with reading the Ape forum and especially Allen Noland's facebook page the engine can be assembled right and ways better than it comes from the Aprilia plant. The oil seal in the alternator cover is one thing often made wrong by Aprilia but the problem of shearing the o-rings on the hollow pin between left crankcase and the alternator cover during assembly can simply be solved with two chamfers and a bit of sand paper to round the edges. The starter motor is a well known problem but the forum knows help. In this and other forums there are endless threads discussing the Ape. Aprilia put a lot of hope in the SXV/RXV but the bike was no success (most reasons were self-made problems from Aprilia). Now the production seems to be stopped, a new model can not be seen on the horizon, bikes and engines are getting fewer with the typical effect on prices and numbers of new/used engines...

    35 kg is the weight for the standard Ape with oil and water. Our's is dry at about 31 kg.

    IMO a low-weight V-twin is the best solution for FSAE. It weights almost the same like a single, has a wider usable speed range, more power (the Ape is closer to an inline-4 than a single), runs smoother and has less vibration. Packaging is more complex (two heads --> two exhaust header, two airbox runners, two coolant hoses), but it's worth the effort.

    Regards,
    Leibi

  9. #29
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    Quote Originally Posted by Mbirt View Post
    I also wanted to show how unsubstantiated several of these points are, but I was getting way too into it and wasting too much time. So I'll keep it simple.

    1. Burn speed remains constant eh? The single-cylinder engine has a greater quench percentage of bore area area than a 600/4, so that helps with turbulence. High charge density is also possible with good intake designs that negate the effect of the restrictor on a pulse-by-pulse basis. We're not the only single-cylinder team running only 30 degrees max ignition advance at WOT.
    You will get higher turbulence and thus a higher flame speed with a single compared to a four, especially as most 4 cylinder engines cylinder heads are optimised for a large filling rather then for turbulence and the low average piston speed resulting from the decreased rpm due to the restrictor. However this was an argument against Zs "everything gets better with a one cylinder engine". And i have not writen anything about a 4 cylinder engine. I meant in comparison to a two cylinder engine and my arguments stands.

    2. With an 85+ hp KTM and several fuel economy wins, tell Wisconsin that turbocharging a single doesn't work well in FSAE. I don't consider 65-72% compressor efficiency to be bad at all. And large exhaust pulses work great for quick spool, it's the boost creep due to insufficient wastegate flow that gets you.
    in 2012 Wisconsin won fuel economy at FSAE, however they were almost 20% slower then the team that won endurance. Its easy to save fuel when you are going slower.
    in 2011 Wisconsin had the same fuel consumption as Tu Munich with a 4 cylinder engine.
    I dont see how this is an argument that a turbocharged single can work excellent. And you don't take into account that a turbocharged single will be much harder to drive then a naturally aspirated car.
    The problem is that FSAE straights are extremely short. When the longest straight only lasts for 3 seconds you can not afford to have your boost pressure build up for over a second, especially if you consider that the distance traveled is the acceleration integrated twice over time.

    65% compressor efficiency isn't that bad, however its in an area of the compressor map that wont be used too often and 60% turbine efficiency is bad. Plus you get a really bad overall turbine efficiency due to your wastegate. Turbines work way better with a more constant gas flow as their efficiency drops in the slopes of the massflow. What is the point in having one large pulse, that you can not fully use and for the rest of the cylce you are left with no power at all, slowing the turbo down. Believe it or not on a 2 cylinder engine, you will get the same overall engine efficiency with a modern mechanical supercharger as with a gt12 as turbocharger, and i bet its not getting any better with a single.

  10. #30
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    Quote Originally Posted by EPMPaul View Post
    Single BRP = 1.22 hp/kg. (43HP - 35 kg)
    Inline twin = 1.33 hp/kg (60HP - 45kg with gearbox)
    Aprilia 550 = 1.5 hp/kg (53 Hp - 35kg)
    Inline 4 = 1.44hp/kg (80 HP - 55kg)
    I dont think that the power to weight ratio of the engine is very meaningful. Youd have to compare the power to overall weight (including driver) to get a real comparison:

    Driver weight: 70 kg, Car weight taken from Homepage

    Gfr 450 single: 158 kg 55 Hp -> 228 kg -> 0.24 hp/kg
    Erlangen 550 V2: 165 kg 76 Hp -> 235 kg -> 0,323 hp/kg
    Stuttgart 600/4: 167 kg 90 hp -> 237 -> 0.38 hp/kg

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