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Thread: What's the deal with engine and tranny reliability?

  1. #1
    I worked the enduro on Saturday and was surprised by the relatively poor reliability of the bike powerplants.

    My thoughts are:
    1. Are these engines dry-sumped in FSAE cars? I suspect not, and wonder how they can last as long as they did without one. Seems like oil slosh, not present in the bike, would be a real problem, as UO can attest.

    2. Why did two (that I know of) transmissions eat themselves? U of Hawaii was especially sad, sounding like someone left a pair of pliers in their gearbox. Seems to me that bike trannies in a car have a very difficult time due to having about 10x the traction. In a bike, the rear tire just spins, venting off the torque. In the car, though, all that torque has no where to go -- and starts eating gear teeth. Or, is it simply poor shifts by the driver?

    I guess my real thought is, is this size bike engine and tranny appropriate for the fictious weekend racer product? Or is a larger engine more appropriate if for no other reason than reliability. I'm curious for your comments.
    Tube-frame, carbon composite-shell, Honda-powered, mid-engine Mini: www.kimini.com.
    Buy my book: How to design and build a mid-engine sports car - from scratch. http://www.kimini.com/book_info/

  2. #2
    I worked the enduro on Saturday and was surprised by the relatively poor reliability of the bike powerplants.

    My thoughts are:
    1. Are these engines dry-sumped in FSAE cars? I suspect not, and wonder how they can last as long as they did without one. Seems like oil slosh, not present in the bike, would be a real problem, as UO can attest.

    2. Why did two (that I know of) transmissions eat themselves? U of Hawaii was especially sad, sounding like someone left a pair of pliers in their gearbox. Seems to me that bike trannies in a car have a very difficult time due to having about 10x the traction. In a bike, the rear tire just spins, venting off the torque. In the car, though, all that torque has no where to go -- and starts eating gear teeth. Or, is it simply poor shifts by the driver?

    I guess my real thought is, is this size bike engine and tranny appropriate for the fictious weekend racer product? Or is a larger engine more appropriate if for no other reason than reliability. I'm curious for your comments.
    Tube-frame, carbon composite-shell, Honda-powered, mid-engine Mini: www.kimini.com.
    Buy my book: How to design and build a mid-engine sports car - from scratch. http://www.kimini.com/book_info/

  3. #3
    A 600cc supersport bike engine is fine for the weekend autocrosser. Most of the problems I've ever seen with FSAE engine reliability come back to either inadequate oil supply or some other dumb mistake (like using an engine that looks like it sat on the bottom of Lake Erie for awhile).

    As far as oil systems go, when I was in school, we did a stock wet sump with chopped pan (2003), a super chopped oil pan with wet sump and Accusump (2004) and a homebrewed drysump (2005). All three of those setups had LOTS of drivetime on them.

    The 2003 setup pretty much worked fine, every once in awhile you'd get a blip of low oil pressure in a corner, but I don't really remember it shelling engines.

    The 2004 setup (once we put the Accusump on) worked perfect- the oil pan was about 1" deep, we never saw any oil pressure drops, and as a bonus we even had oil pressure on engine startup.

    The 2005 setup blew up a number of engines. In fact, the UMR team DNS'd enduro in Detroit last month because of the dry sump system (an evolution of the 2005 design) and converted back to a wet sump before Fontana. They still DNF'd enduro in Fontana, but this time it was electrical. *beats head against wall*

    I'm not saying dry sumps do not work on FSAE cars, but if I was going to build one for myself as a weekend SCCA autocross car (or to take to FSAE for that matter), I'd do a wet sump with a thin oil pan and an Accusump. The effort spent on making a dry sump work on an FSAE engine that was orinally wet sumped could be put to better use in my opinion.

    All in all, I did tech inpection 3 days at West, watched all dynamic events, and it was painfully obvious that simplicity = reliability.

    I think the OU guys said overheating caused their "blowed up motor", not oil sloshing. Correct me if I'm wrong.

    Btw, the kimini is pretty cool.
    --------------------------
    Matt Giaraffa
    Missouri S&T (UMR) FSAE 2001 - 2005

  4. #4
    Dry sumps dont work and people loose oil pressure.

    Bikes dont have near the cornering forces that a FSAE car can have (2 vs 4 tires for stability) hense the oil getting slashed around on corners, pickup for pump is starved, loose oil pressure.

    FSAE cars weight alot more then a bike, clutches and trannys dont like that.

    People have bad tunes.

    Bad drivers.

    Almost all engine fires happened because a rod went through the block and oil got on the header....and the oil issues are what made that rod disconnect from the crankshaft.

    Some teams do modify the internals of the engines to squeeze out more power, if not done right this will lead to failures as well.

    On the trannys, it might also be the differential/chain drive causing problems. The chain tensioning and differential housings are student designed/made and are not perfect.

    I am sure there are many many more.
    Mike Duwe
    UWP Alumni

    Former Drivetrain Leader and Team Captain

  5. #5
    ha, ask and you will receive....

    Darn bit on the differential, otherwise I would have beatcha Matt!

    If you look at the abuse that the engines are going through overall with the heavy cars, heavy abuse, heavy cornering/accel/braking, bad tunes and look at how many engines are still running after competition (not counting failures of things external to the engine) I would give them a lot of reliability credit. Many teams do bring back the same engines 2 years in a row.
    Mike Duwe
    UWP Alumni

    Former Drivetrain Leader and Team Captain

  6. #6
    The transmissions are made for a bike with one round tire having a small contact patch that will usually do a wheelie if you get on it too hard. These cars have two 6-8 inch slicks with a contact patch about the size of your hand. Our transmission problems have come from down shifting. Some teams don't use the clutch when down shifting and if the driver isn't careful it is easy to put it into 2 gears at once and shear the teeth off of the gears.
    John Grego
    2008 Suspension Lead
    Texas A&M University

  7. #7
    I think the bike engines/trannys have really shown their reliability and durability as well. As mentioned, these machines are designed, built, calibrated, tuned and set up by amateurs... Its amazing they do as well as they do!

    We've had great luck for years with the CBR transmission... Our engines have always been used when we got them, and then abused by us. I've inspected 5 or 6 of the transmissions from past cars we've run and they all look pretty damn good. Seems like the dogs on 2nd and 3rd get a bit peened, which can be dressed up once or twice before replacement with a good file.

    Don't forget you have a bit of a fuse, called the clutch. I would **hope** that bike OEM's would design to handle everything the clutch can deliver to the input shaft. With a ~500lb or less car, we've had no issues delivering around 70hp to the tires through a stock clutch.
    Kettering University FSAE Alumni

  8. #8
    We've had tranny problems in the past, mostly associated with bent shifting forks (caused by trying to shift under power)allowing 2 gears to be engaged simultaneously. Additionally, the turbo/supercharged cars can add up to 50% more torque then the stock bike has and transmissions and clutches are really torque limited, not power.

    Most blowups are caused by overheating or oil starvation.
    'engine and turbo guy'
    Cornell 02-03

  9. #9
    Also, certain engines don't respond well to being used as a semi-stressed engine. We floated a lot of valves in '03 semi-stressing the engine. IN '04 the problem went away very quickly when we designed the loadpath around, rather than through, the engine.
    Buckingham

  10. #10
    I'll say that as far back as I recall (04) we haven't had any engine or transmission grenading at competition with the F4i. Dry sump system in 07 (first year) was a little leaky and had some teething issues, but once it was all figured out kept pressure.

    We did spin a journal bearing after 06 competition, as a function of the oil system not having been primed before running our 06 race motor, rebuilt with higher compression pistons. Connecting rod started to loosen up and piston started smacking the valves, etc... engine wasn't too happy about that.

    Other than that, only issue I've seen is on our 05 motor we had a bent shift fork, and clutch plates have had light to moderate discoloration after a while. I'd be pretty curious as to how our 07 clutch plates look like after competition, with the whole thing being dry rather than wet (oops!).

    To be honest I'm absolutely amazed we haven't had catastrophic failures and major injuries, related to either vehicle and engine stuff or machining/welding/heat treating/oxy-acetylene to 4-5-6-7-8am.

    Amazing how your perspective on this stuff changes when you graduate..
    Colorado FSAE | '05 - '07
    Goodyear Tire & Rubber | '07 - '11
    NASCAR Engineer | '11 - ??

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