Polishing and porting diesel engines

As the basics are the same I fail to see why there would not be similar benefits as HDI said it depends on how well it was designed in the first place .
Last edited:
I think that in the case of forced induction (as is the case cos naturally aspirated diesels are pretty much defunct) there's no need to be porting and polishing because there's always positive pressure in the intake tracts.

And given that diesel engines have no throttles too I cant see too many benefits.
i agree HDI,boost can overcome some/most restrictions in the inlet tract.

but lately some hi-output/ race diesels are getting more power from larger and straighter inlet systems along with larger ports and valves.

those engines are extreme tho.

but realisticly , probably not needed with most of the guys on this site!

if i want more torque i just up the manifold pressure #s. and add fuel till it smokes then back off fuel a tad.

also another way is add alcohol injection just when boost is high, not when cruising. dont want anything getting into the crankcase!
It's an interesting argument actually, take the ford 2.5 turbo diesel for example. Standard 93Kw and 329nm, after flowing the entire intake side it went up to 104Kw and 361nm. After doing all that we changed the boost pipes to 72mm, fitted a larger intercooler, upped the boost to 1.0 bar from the standard 0.8 and fitted a 63 mm exhaust. It went to 132Kw and 445 nm on the wheels. There are gains when polishing and porting any engine, the gains just differ.
We saw an increase of between 4% and 5% by porting and polishing on the standard system before we did the other work. What i can say is that the response on the diesel was better but not world changing.

Similar threads

Please watch this on my YouTube channel & Subscribe.