If outright speed is what you bought them for, then I agree with Singer, install Slot.it chips.
Your other options are:
1) get scalextric chips upgraded with better diodes and mosfets. User Gmyers offers this as a service, or if you're good at fine soldering you can follow RichG's guide buried in the forum to do it yourself
2) downgrade the motors to lower RPM motors. Stock 18k Scalextric motors would be a good choice, if they are a drop in fit in those cars (not sure if they are, or not). Since the cars will still be way beyond scale speed with Scalextric motors, it's not a big problem unless your desire is for blurry-fast magnet-stuck cars.
What motors are in them - I can't seem to find any specs. If they are the yellow endurance type I wouldn't be too worried; red, or orange would be a different story. Did you buy them already or are you only considering them?
We might be meeting on Suday, if I'm not mistaken, if so, we could take a look. By the way I have a few Schotky diodes to spare if you are keen on trying the upgrade mentioned by MrFlippant.
The Avant motors are very hot. I have tried to chips a couple of them using the double chip trick ......... the thinking behind it goes that with two chips wired in parallel half of the surge goes through each chip.
This is the only make of car that has so far blown both chips instantly! I have chipped cars from fifteen different manufacturers now so do not be surprised if they also blow a Slot.It chip. Do let us know how you get on.
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