on a constant radius turn if I accelerate the car tightens up and vice versa if I back off, is this normal
What do you mean tighten up.
If I accelerate in to a constant radius, I can feel the car turning tighter in to the radius if that’s what you mean.
And if I back off, I can feel the car moving back in the opposite direction.
If so, then I asked the same question a while back.
The answer came back along the lines of the car shifting load on to a different corner, which in effect has more grip, or less grip on the opposite corner.
I’ve never once felt that I’m losing traction, heck, I don’t even drive that fast, but the feeling is a little odd.
Thanks , that is exactly what I meant, no loss of grip but most of my motoring has been with front wheel driven cars, which tends to be the opposite
cheers
Peter
There can be many factors to this and it also depends very much on how close the the untimate limit of tyre grip you are. The simplest answer to this, and the most likely, assuming you don’t actually have the car on the door handles is the steering geometry. MK3 and 4 cars have a multi link rear suspension and can impart some passive rear steering, so changing toe angles as the suspension moves. In your constant radius corner with the car on a balanced throttle the weight is neutral. When you accelerate you shift weight to the rear of the car and the car will squat more and induce some rear steering helping the rear around the corner. The opposite is true for decelerating. It is a question of limits though. We’re you to keep accelerating you would arrive at a point where the front tyres are starting to be overwhelmed and the nose will start to push wider and wider. Equally at that point, lifting will again affect the weight distribution and load will go onto the front tyres increasing their grip, tightening the line. In balance with this, weight also comes off the rear tyres reducing their grip meaning they can slide wide. It is all about limits.
I have the same feeling as HarveyP. Accelerating through a full lock turn does turn the car in tighter.
Coming from having nearly 30 years driving FWD cars to driving the 5, RWD, I think the sensation is more from being pushed around the corner by RWD rather than being pulled around a corner by FWD.
Although NickD’s answer is probably the correct and technical answer 
Thanks for this detailed response, I felt it was due to some weight shifting to the rear of the car as it leaned further into the corner. It doesnt cause me a problem as I doubt that I will push it to the point where I loose grip, it was just that i was curious as to the reason, and you have confirmed my diagnosis as to the cause.
cheers Peter
I’m relieved that it’s not just me or my car to be honest.
I took mine for a 4 wheel alignment 2 years ago considering there was something wrong.
It’s a very odd feeling.