Are these PSI boxes bad for these engines I see their benefit but just seems like puts more strain than good?
You think about it, old engine, old transmission, is extra power a good idea? They also override the torque reduction needed on auto gear shifts so causing gearbox problems.
 
Most of the stuffed heads on here had a powerbox fitted. I can see a mechanism where excess fuel squirted in indescriminately might cause hot and cooler spots on the head leading over time to microfractures that eventually join up or, if there's an issue with the cooling system prime it to fail. However, I can also imagine not all boxes are the same and some may be better (or worse) than others.

Given decent heads are becoming rare, I think it isn't worth the risk for me. Mine's pretty sprightly with the manual box. The auto is sluggish, IMO and I would probably chip it if I had one of them. Again, it'd have to be someone who knows what they're doing so as not to lunch that HP22 box.
 
Most of the stuffed heads on here had a powerbox fitted. I can see a mechanism where excess fuel squirted in indescriminately might cause hot and cooler spots on the head leading over time to microfractures that eventually join up or, if there's an issue with the cooling system prime it to fail. However, I can also imagine not all boxes are the same and some may be better (or worse) than others.

Given decent heads are becoming rare, I think it isn't worth the risk for me. Mine's pretty sprightly with the manual box. The auto is sluggish, IMO and I would probably chip it if I had one of them. Again, it'd have to be someone who knows what they're doing so as not to lunch that HP22 box.
I have had four 4 x 4's before the P38, 3 manual and one auto, by comparison the standard P38 is pretty quick once you get used to the strange throttle response so I am quite happy to have removed the PSI Power box that started to knacker my gearbox.
If I were to consider a power upgrade, it would be a proper professional remap not a squirt more fuel power box.
 
Agreed that's why I removed mine just no point for a car that is not designed for speed and being 25 year old car with old engine and gear box, considering it probably aided in causing my head to crack, shame I didn't know much about these when I first got my P38 would have removed it.
 

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