XRAY - Model racing cars

Hello I have a t2 009 EU and when using a 17.5 motor with boost the car is hooked up. But when I use a modified motor / a 7.5 or 5.5 motor that car gets really sloppy in the rear. I guess some people call it power sliding. I have to be very careful on throttle exit or else it just goes crazy. Curious if anyone has any suggestions..

Sounds like your tranferring too much weight to the rear on power, there is going to be a huge difference between 17.5 and Mod.

The quickest way to prove it might be to quickly change the rear springs for the next rating up and see how that goes.

If you need more detailed info the guys on here really need you to fill out an online setup sheet and post the link to it here so we can see exactly what you've done.
Give as much detail as possible on the sheet.

Skiddins

Little information to go on and as Skiddins says you need to give more. I suspect though it could be setup or driving style or both. You have a heap more power there and you may be applying too much too early. Good drivers can handle mod because they have the capability to apply the thottle sensitively and proportionately - which doesn't mean you cannot but maybe you just need to practice. Equally a good setup with a 17.5 does not necessarily mean you have optimum setup for mod., in fact probably not. I would be inclined to jump the other way to Skiddens and think you do not have enough rear grip, or too much front grip. Perhaps try some more droop on the front to increase the weight transfer to the rear. Alternatively if you are going around the corner a lot faster you may be rolling too much which will reduce the total grip your tyres will give you and stiffening the car could be the way to go (covering my bets there Skiddins )But without some more info on setup and what is happening it is difficult to diagnose & recommend.