Hi my friend has a 2016 Citigo and when he accelerates quite quickly he gets a horrible rattle type of noise from the engine/gearbox

If you drive really gently you don't really notice it. We have checked for loose heat shields and anything rattling under the car and there is nothing there.

I was wondering if anybody else has experienced this and if so what did you find wrong with the car please?

Hard to guess at, unless you can post a sound file (or a video with a sound track) of the actual noise. 

 

Having said that, a "tinny rattle" could be pinking, which can be load-related.

 

As said many times, it can be hard to out exactly where a noise originates from. Can you hear the noise when revving the engine statically?

 

I have a weird rattle type noise the occurs at about 2,500 revs and is much more noticeable when i accelerate hard.. it happens in all gears and it's been happening for about 60,000 miles.!! 

never got to the bottom of what the problem is and its been serviced, MOT'd and checked over....mines a 2015 

I did wonder if there was a valve or something that moves/opens at 2,000>2,500 revs as when i rev it with the bonnet opens it seems to hesitate very briefly at about that range...

so sorry not much help in knowing what's wrong with your car.. but that i have a similar rattle type noise on mine.. (and have had for a long time)