XRAY - Model racing cars

Acceleration will be a bit less although the difference isn't as big as you might think and also not that important. The lower weight improves handling to such an extent that you simply get more corner speed. So it is mid-range acceleration that counts more. Besides, with a 3.5 brushless and 6 cels you have way too much power to truly use anyway.

Run time has become a bit of an issue in the 5 cel world. On larger tracks a 3.5 really comes into its own in terms of acceleration and speed. The car has so much speed and is so easy to drive due to the lower weight that it is a blast to run. But... with all that fun it is sooo easy to use the throttle finger a bit too aggressively and drop a minute or more of runtime that you can suddenly come half a minute (or more ) short. In the GP3700 days I would have said that I felt that was part of the charm. In 12th scale and PRO10 we used to have that challenge too and it was part of the challenge to be very fast AND make runtime. However with the current crop of IB cels which drop performance after only a couple of runs that part is less fun. But then we had problems making runtime with 6 cels too with used IBs.

Tonyv, thanks for your help so far, could you please give us a good starting point for a FDR for rubber tyres on out-door ashfalt. Track is med-large and fast-flowing, only 1 hairpin at end of back strait. Will be running both LRP 3.5 and 4.0 . Thanks heaps

Should have added,the above is for 5 cell

Tonyv, also while we are on the subject. What type of track will make you dump faster. Our experience so far suggests you will dump quicker on a bigger fast flowing track. Yet theoreticly an electric motor uses more amps when spooling up from low RPM, rather than running at continued high rpm,so one would think that a tight technical track would eat battery power quicker. Yet this doesn`t seem to be the case. Whats your experience on this ? Thanks again

To answer the last question first, your finding is correct, you will dump sooner on a large flowing track. There are two basic reasons for this. The first is that electric motors are most efficient at around the 70-75% mark (at least for brushed, brushless might be a slightly different %). So running at 100% throttle most of a lap will cost you runtime. The second reason is that on smaller tracks you gear down as acceleration is now much more important. But that also reduces the amp draw even at full throttle and thus helps increase runtime more than you lose due to the fact that you now need "spool up from low RPM" more often.

For 5 cel with a LRP 4.0 you could start at around 7.0-7.5 I think. Perhaps Bart Wubben can give you a better starting point if he sees this as he has been running LRP the whole season.