Daan Posted March 12, 2008 Share Posted March 12, 2008 a few things have long confused me about this. i must be missing some fundamental principles of how my engine functions.since it has no throttle body to control airflow, the control is within the pump and controls the amount of fuel, the air is consumed as required for the correct burn? when on boost, the pressure moves the diaphragm and increases the amount of fuel to compensate for the now increased amount of forcibly inducted air? so if i were to increase the boost to 1bar, will the fuel pump add fuel to suit or will it burn lean? can it burn lean? likewise increasing the fueling, will that make it overfuel? can it overfuel? and by what method is this best done? does rotating the diaphragm to increase the ramp only affect fueling on boost? ive been privvy to so many seemingly conflicting or confusing pieces of advice regarding gaining increased power from my engine, i would love for someone to give a definitive answer as to 'doing this will increase this, but you do or dont need to do this also' type advice. im looking your way Ian jim A diesel can run lean, very lean in fact, which is one of the reasons why it is also more efficient. The speed is , as you say, controlled by changing the mixture fuel to air ratio. Basically, the more air the engine has, the better it runs, hence the turbo and intercooler. More fuel added to this will increase the power, but decrease efficiency, to the point were you have a trail of black smoke behind you, which is unburnt fuel. Problem with increasing turbopressure is that the temperature of the intake air will also increase, similar to pumping up your bicycle tyre resulting in a hot airpump in the end. So higher pressure does not neccesarely mean more air. Also, when you do this, it will only delay or reduce the moment the wastegate opens. This means it only works flat chat, and does nothing at low RPM. my personal opinion is bigger intercoolers are wasted in challange trucks as the rely on the flow of cold air through them to cool the inlet charge (its actually an air-air heat exchanger) as there is no fan to drag air through the intercooler its doing nothing while you are bogged down in mud or crawling on rocks at 2mph.for challenge trucks it might be worth putting a fan on the intercooler (i think escourt RS turbos might have had this arrangement, if not its a common mod) to drag air through it. the other way to go might be a charge cooler (water-air) which uses water as a medium to dump heat from the inlet charge... Eh, every TDI has a fan working on both the radiator and the intercooler. Most people replace this for an electric fan, stating that it is only works when you need it. But you always need a low temperature intercooler so thats why I still run the standard fan, currently even locked solid. My 2p anyway. Daan Quote Link to comment Share on other sites More sharing options...
JST Posted March 12, 2008 Author Share Posted March 12, 2008 Eh, every TDI has a fan working on both the radiator and the intercooler. Most people replace this for an electric fan, stating that it is only works when you need it. But you always need a low temperature intercooler so thats why I still run the standard fan, currently even locked solid.My 2p anyway. Daan Agreed but there are problems running a viscous the whole time, ie when the engine bay is full of mud it wont work and you dont really want a fan on in water either if you can avoid it, that the reason i went to electric (and the viscous was knackered) So how do you check the turbo pressure/adjust it then? i am now thinking to check that to see if the guy also played around with it before i got the truck Quote Link to comment Share on other sites More sharing options...
discojmz Posted March 12, 2008 Share Posted March 12, 2008 thanks Daan! youve basically illustrated my dilemma brilliantly. i wish to keep the standard intercooler, and thus half of me thinks upping the boost to 1bar will gain nothing and increasing the fueling will drink fuel disproportionately to any actual performance gain, and i'll watch it all blow out the back... or will that .2bar not increase charge temperature noticably and that diaphragm rotation mean i can get the same economy through lighter-right-footedness. or with an increase in boost pressure, perhaps it would not be too smokey im starting to guess that there is no easy answer, and it'll be a bit suck it and see? we've been talking about restrictions in the inlet side... how much difference will replacing the mid box with a straight bit of pipe make? obviously both sides need to flow as well as possible Quote Link to comment Share on other sites More sharing options...
JST Posted March 12, 2008 Author Share Posted March 12, 2008 we've been talking about restrictions in the inlet side... how much difference will replacing the mid box with a straight bit of pipe make? obviously both sides need to flow as well as possible from my experience a straight through pipe on a std tune vehicle makes it louder and thats it, on a tunned vehicle it makes the turbo pickup slightly quicker and is louder! Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted March 12, 2008 Share Posted March 12, 2008 Here you go Jim - have a read through this: Diesel theory In short, increasing the boost will give you more oomph. The pump will add more fuel for the extra boost. You then start getting into how the engine will respond to the changes with increased torque etc. My bet is that you can end up with better economy, however it may be only over a very small rev range - and unless you cruise within this you won't see much benefit. Try it! See how it goes... Quote Link to comment Share on other sites More sharing options...
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