Hot motor - AGAIN!?!

[Cardnim]

Morning guys,

Quick bit of history:
- racing a Cat SX2
- had 2 previous motors - both Speed Passion v3 6.5 - both bought second hand from fellow oOplers
- both previous motors eventually got so hot that the internals melted enough to ruin the smoothness.
- have tried different combos of spur / pinions and replaced every bearing and ensured no fouling on drivetrain.

So.. now to last night.
- decided not to muck around with 2nd hand motors, so bought a brand new SP v3 6.5; fitted last night for my first club meeting with it.
- after first qualifier the motor was up at 80C!
- fitted a make shift heat sink to it which seemed to bring it down a degree or two.
- but Im really scared (and bloody frustrated) that Im about to cook another (£70!) motor in the first couple of race meets.

I have checked everything that I know of - drivetrain, gearing, binding, bearings - but cannot find anything that is amiss.

The timing on the motor hasnt been touched from factory default (which seems to be in the centre of the timing adjustment ie about 5 degrees)

The ESC is a Speed Passion GT2.0 (lpf) which has its timing turned down to zero and the "DRRS" (start boost thing) down to 3 "normal" from a range of 1 - 9 (9 being max).
Tried it on 1 but still getting the heat.

Top drivers both from my club, and from Schumacher and others have offered me help, but I feel guilty constantly going back to them, (and feela bit embarrased too!) but I dont know enough.

...the SX2 just seems so complicated and Im new to this so really struggling to know what to do.

Any (and all!) advice and suggestions very gratefully recieved guys

[Cardnim]

Should just add my gearing...

Internal gearing = steel idler set = 22 / 33 (IR = 2.70)

Pinion / Spur = 24 / 80

Final Drive Ratio = 9.0

[DCM]

Not knowing the esc and motor, I can only suggest you get advice on gearing and timing settings, as they will dramatically affect heat, plus driving style. Otherwise, your looking at something binding on the car.

[Cardnim]

Really appreciate the help DCM (I wish my car was as fast as your response!! hehehe)

One of the Schumacher guys was helping me with the gearing, and Im running close to the ~8.6 FDR that he recommended so not sure its that (but will try a few different versions!)

Two things Ive thought might be coming into play but not sure:
1 - the track is high grip astro, and Im only opening the throttle fully once, for less than a second coming onto the straight. The rest of the time, Im cruising round somewhere about 50% throttle.

2 - Could the ESC software version be giving me problems. If the firware is set for a modified motor or high end timing, but Im changing the settings to turn it all off/down, then would that cook the motor?

[DCM]

to much timing can cook the motor, but I am a Tekin man, so couldn't really offer you any suggestions on the settings for a speedpassion.

[Big G]

I'd probably gear down on the pinion. It sounds like you're not using much of that top speed anyway

[Gareth J]

it sounds like something may be binding I run a 7.5 sp with sp esc with timings high in my 410 and its hardly even warm

[Cardnim]

Cheers DCM, Gaz and Gareth.

@Gareth - thanks for that. Its helpful to hear others running the same motor. I know the SP v3 arent supposed to be a hot runner (like an LRP)

I'll check for binding again, but I build each part of the drivetrain seperately, and then test after each bit is added. It all feels pretty smooth.

[bigred5765]

the best thing to do with gearing is make sure the car is at full revs(so you here the motor scream) at 3/4 the length of the main stright. its hard to give a gear ratio as we dont no how big the track is, gear the car / motor to suit the track,ps 80 deg doesnt seem that hot to me

[mattybucks]

I would put the kit spur back on the car 83 i think, and run about a 20-22 tooth pinion.

Firmware on a SP - I use the 205 mod firmware, with the standard settings out of the box settings.

Make sure nothing is binding, and that the belts are not to tight.

[sosidge]

A few thoughts...

For a GT LPF you should be on software version 205MOD, you shouldn't really have any problems running that software on maximum timing or punch.

A 6.5 in 4wd with the LPF may be pushing the ESC's abilities a little. Not sure how that would necessarily result in the motor overheating, but it may be a reason. Is the ESC itself hot after a run?

Drag brake generates a huge amount of heat in the motor, ideally run it at zero and brake manually, 10% as a maximum setting if you can't get along with that.

Apart from that, the most likely mechanical issue is drivetrain drag. If you are not experienced with the cars it may be hard to know how free it should be so put it in some experienced hands. With the pinion off, the car should roll freely along the kitchen floor with little more than the inertia of the wheels and tyres to overcome.

I don't know the SX intimately, but as an example, my Yokomo B-MAX4 suffered from bad mouldings in the centre transmision that pressed on the bearings and made the transmission very tight. It took me a cooked motor and some thought to realise this, and a less experienced builder would probably never notice it. Another common example with some other cars is that it is possible to over-tighten the wheels and lock up the bearings.

It's possible that just one axle, shim or bearing in the drivetrain is tight and that is all it takes to overheat motors (and affect the handling too).

[Cardnim]

@Daz - good point chum. I think that confirms that they are on right.

@Sosidge - thanks for that excellent info. As you say, my inexperience may be missing some important points.
Re: the ESC. Its rated at a 5.5t limit and I have all the timing switched off. No drag brake. The ESC is never hot after a run, but its got the heatsink and fan on it, so maybe this is giving me a false impression of coolness.

The 205MOD software you mention - you also said that it shouldnt have any problems running on max timing an dpunch, but I have timing and punch off - so would that 205MOD still be what Im after?

Thanks so much guys - this is awesome help.

[bigred5765]

the main thing i can see is how small the track really is 6.5 i would say is just to hot for that size of track,and if you have to run it gear it as low as possible there isn't anything on there i would call a straight,83 and the smallest pinion you can find 15 -16 and turn punch down or it will wheelie everywere

[Cardnim]

Balls. I think you are right mate....
anyone want to swap a (nearly) brand new 6.5 for a 10.5??

*sigh* one of these days Im going to make a good decision.

Cheers for the advice Carl!

[mdb_75]

I always used to have trouble with my motors getting too hot when using my SP Lpf speedo, one even burnt out when we upped our finals from five to seven minutes! I was using the preinstalled software (not sure what it was, something .Mod though) and had all of the settings turned right down. I updated the software to a newer .Mod version and the problem went away.

I've updated again since to the turbo software and it's still fine.