HPI RS4 Sport 3 Flux - help with next steps (3s speed run car)

[El Dougo]

My current set up is a Hobbywing 120Amp SCT ESC with a 4000kv Flux motor, 52t spur and a 47t pinion, so far I have managed 77mph dead with the stock Porsche body.  I switched to a BMW M3 body and it took off at about 60 so I added weights to the front and it hit 70, thinking the wing was the limiting factor I removed it and managed 72 although it was very, very loose at speed!

 

So where I am today is I’m going back to the stock body and I have a dilemma as to motor choice.  I have a few on the shelf a 540 sized 5200kv, two 550’s one 4T 4700kv and a 4.5T 4200kv the 550’s have a 5mm shaft and the biggest pinion I could get was a 45 so I would be dropping a couple of teeth if switching to a 550. I also have a slightly smaller spur (think 49T) and I purchased a Porsche Carrera GT body that should be much more aero efficient so that will be going on in the near future!

 

Any hints and tips on getting more out of it and what motor to go for would be gratefully appreciated.  At the moment  I’m tempted to go with the 5200kv and down the gearing a little.

 

Taking off

 

 

77mph run

 

 

 

[bunnie]

What tyres where you using with the m3 body? I've got same setup apart from gearing and the back end wants to kick out all the time. I've added adjustable turnbuckles which helped a bit but the problem is still there. 

[ajlovering]

You need a bigger ESC and taller gearing.

 

Cheers

[twisty]

On 8/5/2016 at 13:59, El Dougo said:

I switched to a BMW M3 body and it took off at about 60

 

lol ,keep at it

[NuttyProfessor]

Team Epic/Trinity 540 motors are tested to 4s, I had a 6000kv 7.5t running 4s on a HK150a esc, shame I never clocked it. Also had 7900kv on 2s with a 120a Turnigy Trackstar Turbo esc on full timing and a 15000rpm boost, that was too evil to drive.