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 Post subject: BEC vs CEC...
PostPosted: January 13, 2012, 5:00 pm 
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Joined: April 3, 2011, 3:37 am
Posts: 5
Hey Everyone

I am just in the planning stages of my build, and i have a couple questions for all those with bike engine'd cars

I guess the first thing i want to know is.. even with similar hp figures, why does a bec seem to be so much quicker than a locost with a car engine with the same amount of hp?

Say a locost with a cbr900 engine.. 140hp ish looks SOOOOO much quicker than one with a toyota 4age that also has 140hp which looks slow and sluggish. is it purely a weight thing?

Would love to hear what people have to say!

Thanks in advance
Jim


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 Post subject: Re: BEC vs CEC...
PostPosted: January 13, 2012, 5:53 pm 
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Always Moore!
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Joined: November 9, 2007, 3:40 pm
Posts: 3939
Location: Pittsburgh, PA
I would guess weight and gearing. It seems like most bike transmissions end up being pretty short when installed in a car (the reason behind the 7k ear drum beating people complain about with highway driving).

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 Post subject: Re: BEC vs CEC...
PostPosted: January 13, 2012, 5:58 pm 
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Joined: May 24, 2010, 6:10 am
Posts: 61
Location: Hawkes Bay, New Zealand
I can pick up my complete engine(2005 ZX10r) including wiring and computer and Im no weight lifter. With my chain driven diff weighing less than 10kg there is a huge % of weight saved. The lighter the car, the bigger the difference the weight makes.


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 Post subject: Re: BEC vs CEC...
PostPosted: January 13, 2012, 9:55 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 5909
Location: SoCal
What they said, it's justa power to weight ratio. I'm curious though whether you mean faster solely by lap time, or are you saying that they sound faster?

I've gotten exactly one ride in a Hyabusa-power Locost and yeah, I can say that even in the 30-minute ride we took on the freeway, the angry-bee-in-your-helmet gets old in a hurry. Also, because a bike engine has no flywheel, the driveshaft, axles, wheels and tires take its place. Because of that, instantaneous engine speed variations have a very annoying effect, like the driver is repeatly bumping the gas pedal, up and down, up and down, over and over, about twice a second. It's the drivetrain winding up and taking out the slack on one side of the drivetrain, then backing off and riding the other side. If he merely pressed on the gas a tiny bit more or less it would instantly vanish, but because of it you couldn't ever leave the gas pedal in exactly the same position for any more than maybe 10 seconds.

Starting off from a stop is tricky, also due to the missing flywheel. Even the owner who'd had it for several years stalled it twice. Then there's having no reverse.

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 Post subject: Re: BEC vs CEC...
PostPosted: January 14, 2012, 8:20 pm 
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Joined: July 17, 2009, 10:56 pm
Posts: 378
Like Kurt says I can see the BEC being used for road could be annoying,1st gear is super tall with the remaining 5 being VERY closely spaced,for example using my R1 the speed difference between the top of 2nd and the top of 3rd is only 20kph.You either have a sluggish car(even easier to stall) off the line due to the tall 1st gear or it revs too high on the freeway,hard to have it both ways.

However if its strictly for track duty,there's no way in hell I'm going back to car based power.....EVER. :D


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 Post subject: Re: BEC vs CEC...
PostPosted: January 14, 2012, 8:50 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 5909
Location: SoCal
Oh sure, for track, all the disadvantages go away and it's nearly the perfect choice for a light car.

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Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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 Post subject: Re: BEC vs CEC...
PostPosted: January 15, 2012, 12:24 am 
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Joined: April 3, 2011, 3:37 am
Posts: 5
thanks for all your replies everyone.. really good food for thought..


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