Hey Outlaw....like I said, IMO the biggest thing is to find the right gearing. To me, what Novak tells you about the final drive ratio is OK, but I think it is really meant for people running rubber tires that have a pretty consistent diameter. For us northeners who run foam tires on carpet, there is a huge difference between when you slap the foam tires on the car at 62 mm, run them at race size at 58 mm, or run them all the way down to the rims at 55mm.
Because of this, the only way to accurately and consistently get proper gearing it to figure rollout. I have always done mine in MM, but you can do it in inches too. The formula is pinion x tire size in MM x 3.14 / spur gear size / final drive ratio of your car. I don't know what it is for an HPI so you will have to look in your manual.
I have had very good success with my TC3 rolling it out at roughly 27mm. It is plenty fast and easily makes run time in the unlimited mode with 390s 3300s.
For example, If you have a TC3 with 62mm foam tires, a 100 tooth spur and a 34 pinion, your rollout would be 26.48MM. As the tires wear down to, say 57mm and your don't change your pinion gear, you will now be rolled out at 24.34MM. It doesn't sound like much, but it can make a huge difference in speed on the track.
So to make a long story short, with foam tires on a TC3, I always run a 100 spur and between a 34-39 tooth pinion gear ......whatever is going to get me in that 26.5-27mm rollout area.
I have heard stories of people rolling the brushless out much higher like 30-33mm. I actually made that gearing mistake this weekend when I had a 39 on when I thought I had the 34 on, (30.37mm) and I hit the thermal shutdown on carpet at about the 3 minute mark. The car was crazy fast on the straight, but did seem to lack some punch through the infield, so I think the motor might be out of it's powerband anyway. I think the people who are rolling that high must be running on asphalt where the traction isn't as high and it doesn't put as much strain on the motors/speedo. On a 40'x70' indoor ozite track, I have never been able to make a full 5 minute mod race without hitting thermal shutdown when I rolled out over 28MM. NEVER! I'd like to hear Charlie's thoughts from Novak on this. And yes, I'm still running the vent hole in the window to get air to the speedo.
Keep the posts coming because this is one of the only spots on the net that I have found where there is some reasonable info on this system. There is just so much crap floating around out there about the brushless motors and a lot of it just isn't true. I still think it's one of the best RC purchases I have made. I have gotten some "wow, that's a brushless?" lately at the track and I think I may have even converted a few guys. They are way fun and if you like to be on the track driving instead of trying to figure out why your crappy brushed motor isn't drawing any amp and running slow, it might just be for you.
out.