Stock internals guestion

[zx_volcane]

Yup get the grinder out, although you want to be as accurate as you can so you keep balance between all the cylinders - bit of a grey area though tbh, and I think practically all these idi engine designs are from a time before CAD was used in any meaningful sense to help design anything, shame manufactures dropped idi.

Spray pattern, precup and piston cutout are all designed to work together, so altering one can affect the other, bigger may not always be better.

Hence why using (for example) merc injector tips designed for a totally different precup design that relies on a ball to atomise the fuel might not be such a good idea in the long run.

Most bigger / more powerful idi have larger precups, and those that have been revised has been revised with larger precups - although this might not always be with power in mind, most things seem to be economy or emission driven, like the difference between the XUD 299 and the 299A nozzle tips.

I think once you get to this point you're on your own, on the bench, with a grinder and lots of ??? - go big or go home I guess

But we're talking pushing the limits of the xud head here, right on the edge of space so to speak. Not going to make a difference for bellow 250bhp I wouldn't have thought. Much better gains to be had elsewhere.

I would consider ceramic coating as a good bet to keep heat where it belongs - but you're talking proper money vs some quality time with the grinder.

[Dave]

Got big love for the XUD right now, and just wanting to plunge my head into an engine bay and get to work. Tom you're making me want to come home early just to work on my 300 quid dturbo