Replacing the part fan causes stringing and artifacts?

I'm currently printing lots of "benchys" in PLA. It's always the same file, but different effectors and extruders.
Lately I've replaced the axial 40x10 part fan with a radi(c)al 50x15 blower. The fan duct has the same size ( a little bigger now )
I see lots of strings now, regardless of filament temperature changes. I sliced the benchy again with the part fan reduced to 50%. A bit better, but not as before.

Can too much part cooling ruin a print?

I remember vaguely, that I bought the 1.8mm ID PTFE tube from E3D and I seem to have used it here for the first time. My retractions (4mm@80mm/s) don't seem to work as expected.
Has anyone made the same experience?

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o_lampe

Can too much part cooling ruin a print?

Only if you go to the extreme.

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o_lampe
1.8mm ID PTFE tube from E3D

I always use 2mm ID no problem.
1.8mm is to narrow to allow 1.75mm filament to pass fluently.

...but it's from E3D, they should know...
I wanted to replace the narrow tube and found the real reason: The PTFE tube that goes through the hotend should end in the heatbrake, but it didn't.
Instead the tube was bent a bit, which caused the retratcion issues.
So It's user fault, not E3D or radial fan.

Still, 1.8mm ID is not a good idea at all.

Saying 'E3D should know...' Is a bit short-sighted imo. (no offence meant here..!)
In another thread I told about that silicone socks failure, I've even sent E3D a letter about it, how I changed these socks my way. It was only a minor correction but resulting in good results. The only reply from them was 'Good for you it worked out '. Months later they sell these socks including the correction proposed by me(I've even sent them a photograph). Still got that mail, I'll send it to you if you want me to. (I was probably not the only one with that complaint)
Point is, they too have to find out one way or another how to improve their products. They do not know it all, far from...
Do not misunderstand me, it IS a good product E3D is selling, but like many other companies they make mistakes too. E3D would be the first not to.
And another of my complaints E3D's products are FAR from cheap...!