I wonder diffas how much you spent/”invested” in your car to get it at the power level you are ? I know I spent tens of thousands…
To be honest I have been tested and errored some but mostly been able to have always more power and performance over the years. My budget has been really small and that usually causes delays on the build. Luckily I have managed to sell my old / tested parts to buy new one so that increases costs of the new build...and also learning to fabricate stuff myself keeps costs down too. But yeah some thousands are spent for sure over the years.
What I've learned over the years is that you really need to start off with the top condition engine. So that been said, you really want to use base engine like bau, bdg, bdh. Those have new roller type of lifters and have little better valve control due just a bit tougher valve spring pressures. And also stronger bottom end atleast compared to akn and afb. That harder springs translates better valve control with higher boost / emp numbers. And not to mention worn out cams with early engines. Also must to do is to clean heads from the egr soot. With just that 300hp numbers with pretty clean output is no joke. Next step is for sure make heads done; some porting and upgraded valve springs.
For fueling. That is the most weirdest thing of these engines. I think somewhat around 2009 or so I was told repeately that these engines cant deliver fuel over 200hp. I had B5 with 150hp AKN engine back then. Ordered Finturbo bolt on hybrid back then, that I believa was build from the gt2056v or so. Few mm bigger wheels both side. Combined with (I believe was called "iveco" nozzles back then) upgraded nozzles it delivered 225hp or so. With some tweaking on the software and I think I ordered new bigger hybrid turbo (basically 2260) from finturbo and it delivered around 250 and stock clutch started to slip. That was agains said max level power these support and i should be lucky with that power.
After that I think I upgraded the the heads for mildly ported BDG heads, same ones I use today. On that time I believe I changed nozzles to OE cummins bosch dsla143p970. Power inreased to ~280hp with around 1.8bar . I was pretty happy with that setup. Good responsive turbo and decent power. That wasn't enought after some time so I decided to go over to WG turbos instead and target was 300+. I believe it was 2013 when I installed old good gt3071r (nowdays called gt2971r) and made vp44 upgrade (stock akn pump with ake 3plunger pumphead). Not so responsive turbo but delivered good power 300hp with 2bar and AFR 17.5 - 18.5 on full power. So proved everyone said its not possible wrong again.
And really that was with the cummins oe nozzles. I think I drove around half a year with that turbo and then garrett came out new gtx series and I switched over to GTX2863R and bigger CPC nozzles. Heh I remember I had a case with CPC and probably are banned from their facebook ever since.
Nozzles had atomization problem on test bench but cpc told I should use better equipment. Well yes but harder to find better than top notch bosch diesel service.
Diesel service said you can use them they are adjusted but might cause excessive smoke because not that quality atomization. Car went faster and delivered more power. I belive it was now around 330-340hp and from now on it wasnt giving more power, only more smoke. There started to occur weird advance problems with the pump so it was time to install external lift pump I have had on shelf waiting for install. Immediately on the first pull out of the garage it felt stronger waay less smoke. Went dyno and it gained 40hp with the same ecu mapping and AFR went from 14:1 to 16:1. Made an smoke test video
about it. I think it was most powerful 2.5tdi back then in finland. My ourcome was that the vp44 internal lift pump wasnt able to keep up the pressure in the pump case so high pressure dropped and gave really only smoke. So when going past 300 i really recommend to have lift pump, its not a bad thing to have even lower power levels. Something like 100gph/350lph @ 1.2 - 1.5bar
The lift pump didn't solve the advance problem. It was caused by the broken flywheel. And I belive the flywheel also caused the engine crank to vibrate so much it broke the low end. Some pics of it https://evvk.1g.fi/kuvat/Diudi/remppa/vauhtis/
My current build is stage 3 so it has also upgraded cams, and my stage 3 compound three-turbo kit installed and slightly reduced compression.
Funny thing is that I have now stock 2plunger AKN pump and +90% over stock nozzles it gave more power and even cleaner with exactly the same ecu tune that had 380hp years ago. Now 394hp/290kw. I used that ecu maping just for breaking in the engine and have it dynoed and make it all street legal. Surprised me big time.
dang long post