Volumetric efficiency?

dan_b

dan_b

A2OC Donor
A quick question with probably a long answer, but does anyone have any knolwege about what the volumetric efficiency of the 75PS 1.4TDi diesel engine is? And what it is when you remap it to about 105PS?

Ie do we assume that the VE is >100% because of the forced induction?
 
Last edited:
dan_b said:
A quick question with probably a long answer, but does anyone have any knolwege about what the volumetric efficiency of the 75PS 1.4TDi diesel engine is? And what it is when you remap it to about 105PS?

Ie do we assume that the VE is >100% because of the forced induction?
Click to expand...

On a non turbo car the VE is easier to understand and for 100% effy the piston would be totally filled with air at atmospheric pressure. Due to friction and restriction losses within the ports etc this will never happen but improvements to gasflow, valve size, cam lift etc could raise the effy.

On a turbo engine running at 2 bar boost, my view is for 100% volumetric effy the cylinder would need to be filled with air at twice atmospheric pressure. In addition to the intake system of the n/a engine, combustion air needs to be pushed round the charge air pipework and through an aftercooler core. This is likely to make the volumetric effy worse, even though more air is entering the cylinder
With a remap, nothing is done to the induction system so I suspect the volumetric effy is not changed apart from a minor effect of the increased fuelling will make the turbo spin faster

Cheers Spike
 
Hmm. What peak BAR pressure does our 1.4TDi run at normally?
A remap does more than just up the fuelling, it should also change the boost parameters including higher peak boost. It shouldn't make the turbo over-spin though.

Maybe I'm not conceiving this right, but surely if you have a forced induction engine you're forcing air into the cylinder under positive pressure, so the cylinder will end up containing more air than it would otherwise be able to contain at atmospheric pressure, so the volumetric efficiency must be over 100%?
 
IIRC no car engine has 100% VE

Yes our cars our turbo charged but this is to increase the VE at higher revs, as the higher you rev the worse the VE gets as everything happens a lot quicker.

Turbo cars will have a better VE than those without.

Also on the remaps i dont think vince changes the amount of boost. I think he alters the map to make it maintained for longer so the car pulls past 3000rpm

John
 
Hmm, seems noone knows for sure then. I've read plenty of stuff that says forced induction engines are >100% VE, and that even NA engines that are extremely well designed (ie race engines) are in the 95% region.

As to remaps - well, I don't know precisely what's done to the TDi remap in our cars, but I know from observing previous remaps on petrol engines that you certainly do look to increase overall boost pressure using the ECU's electronic boost control, going closer to the absolute mechanical limit provided by the wastegate - and then of course you then need to alter (increase) fuelling (either by pressure, flow rate or timing, or a combination of all three depending on the engine parameters). I can't see how you can get 30% increases in torque and power without increasing boost.
 
Emissions compliance often limits fuelling and boost levels under certain load conditions.
Remaps generally allow the use of max design limit boost pressures over more of the rev range without consideration for emissions other than passing the very basic MOT test parameters.

Cheers Spike
 
there is a long and convoluted thread on the German forum talking about revs where the engine is at its most efficient and the energy required to keep it moving at specific speeds, if that was what you are after?

Bret
 
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