2008 endurance DNFs

[NabilUofL]

I was wondering how many teams that DNF the endurance had heatsoak problems that caused them to not restart? My team and I are still tracing what actually caused our mishap. The debate stands at amps being unbalanced initially versus heat soak of the engine stressing the electrical causing the balance to be off.

and yes UofL had the 2 foot flames out of the exhaust during deceleration. We like to call them afterburners http://fsae.com/groupee_common/emoticons/icon_smile.gif

[NabilUofL]

I was wondering how many teams that DNF the endurance had heatsoak problems that caused them to not restart? My team and I are still tracing what actually caused our mishap. The debate stands at amps being unbalanced initially versus heat soak of the engine stressing the electrical causing the balance to be off.

and yes UofL had the 2 foot flames out of the exhaust during deceleration. We like to call them afterburners http://fsae.com/groupee_common/emoticons/icon_smile.gif

[screwdriver]

Well rather than heat-stressed electrical systems, I'd rather look at the consumers that are active when the engine needs cooling, like the water-pump and the fans. Take them out of the car and test their current-consumption and performance.

I can also recommend doing a charge balance, ie measuring the current consumption by the consumers vs. the charging-current from the alternator.

Flames as in:
http://www.formulastudent.de/typo3temp/pics/1ecdbf1553.jpg (http://www.formulastudent.de/fileadmin/user_upload/all/2007/bilder/FSG07//FSG20070812/FSG20070812_1285_Hirvonen_35pc.jpg)

[JamesWolak]

Lawrence Tech had the same issues. We never tested before 5pm (or with our body) so we never ran into this issues when running endurance tests.

[Hector]

What engine are you guys running? The early-to-mid 2000s CBR600RRs are notorious for not being able to restart when hot. A friend of mine has an 2005 600RR and every time he stalls it in traffic on a hot day he has to drop the clutch to get it to start. After searching the internet turns out that it's a common problem for them.

[VFR750R]

There's hot start levers on single cylinder motorcross bikes to let some cool air in past the carb. Supposedly any liguid gas in your intake tract will turn to gas fumes in a hot engine will expand and push out all available oxygen making them hard to start.

[Kirk Feldkamp]

It's a pretty common strategy on to have all zeroes on your fuel map in your cranking RPM cells from ~50% all the way up to 100% throttle position. If there is a hot start problem, the driver floors the gas pedal and continues to crank. Since the fuel injectors won't do anything during the following cranking, the super rich air in the intake runners and plenum becomes progressively leaner until a 'better' mixture ratio is reached, and the engine lights off. If you end up flooding your engine during cranking, or have a hot start issue, this will almost always solve the problem.

-Kirk

[Maverik]

Look at your current/electrical side... unless you are running 150C or higher on the engine, I can guarantee it's not a hot start problem mechanically minded. We've run the cbr600rr's forever. The stock bikes it's an electrical problem as well with the reg/rectifier getting to hot, again not mechanical. Sparky nonsense...

[JamesWolak]

I have to agree with Maverik. Ours was definitely electrically related. Though with the temps we were seeing the motor wouldn't have lasted through the rest of endurance.

[Mustang Mac]

I to have to agree with Maverik. Hot start issues on the Honda are caused by electrical and cal. issues. Ran it for 4 years, no problems at all and my last year that thing would fire first crank every time, cold or hot. Just need to have a very well sorted system.

[B Lewis @ PE Engine Management]

My experience over the years with FSAE has been that most "hot start" problems are due to not having the fuel tables correct under hot conditions like during the driver change of the endurance. Usually, just adding more fuel when the engine is hot solves this problem. This assumes, of course, that there aren't any mechanical or electrical problems.

[Discretely elite]

Unfortunately for us, its not that it didn't start. It would not even crank. We had 2 of those small batteries hooked up in parallel but I believe they both got drained regardless. For 09 we are going to have a switch between the 2 so that after driver change there is a fully changed new battery to restart the car.

[hillcountry]

Do you have carbon fiber near any electrical connections? Maybe the run kill relay? Don't forget that carbon conducts.

There is an insulator paint that many teams seem to use, but if you get things toasty the paint can get get gooey and short through the carbon to the chassis. That will kill a battery in no time. Or to generalize, any short will kill a battery in no time.