Exhaust Manifold.

[Mr Whippy]

Ive rush readed that...but did notice a post regarding not upgrading nozzles..

Tbh, i honestly cant believe that not upgrading them is a good idea....the nozzles and turbo is nie on the most important two things of any DI derv motor, the stock ones a f*cking TINY.... who cares about 10 million bar injection, we dont need that much pressure, i can make mine clean on boost at 200hp with just 200bar injection and nozzles the size of hose pipes...

Yes you can make 200 hp on a stock hdi, but i bet to god it would make it easier with bigger nozzles / better turbo...id have thought the rail pressure / hp pumps would be raping making 200+ on stock parts...it just makes no sence to me....why try to tune a derv with such limited components just because it "can" work...to be it should be chronic nozzles, big vnt / compound setup, basic exhaust / inlet work and a chronic remap....sadly its always the latter which seems to be the issue..

Once aftermarket diesel management systems start getting more and more affordable, i think we will see a huge change in HDI tuning, as finally the TUNERS will be able to TUNE there diesel.....

The nozzles are good to 200bhp on an appropriate pump.

Yes RP is high, but that is irrelevant.

RP is a function of how much flow you want to get into the engine and how big the nozzle is.

You could run huge nozzles and low RP, or high RP and small nozzles.

But you can't get BOTH without a BIG pump... and that is the problem, the pump.


The standard HDi pump is good to maybe 180bhp assuming all else is good, at about 4000rpm.

Big injectors, small ones, twice as many, it won't make any difference. No combo of rail pressure and tip size will get around the fact the pump just can't flow enough fuel for more power, no matter how it's injected.


So injectors, yes upgrade them, but only when you have a better pump too.


The old XUD pump is different. They can flow LOADS of fuel. The issue is they probably have higher parasitic losses due to being over-specced a lot of the time.
To a certain extent bigger nozzles are less precise, so over-sizing won't give exact injections at low IQ's, so idle and cold-starting and precise emissions control are less feasible.

Not saying that is bad, if power is what you want great, I personally live the XUD9 when tuned up!

But the HDi is different in a lot of ways, and beyond the small turbine on the stock turbos causing torque curves like mountains and peak power at ~ 3500rpm or below, the next problem is the HP pump!

Dave