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Has anyone had a stock R32 RB26DETT tested on an air flow bench to find out what the volumetric efficiency is of the engine? I'm trying to go through some compressor maps of different turbos to find the right one for my needs. Right now, I'm just plugging in 90%. Hopefully someone will know the answer to my question. Thanks guys
 

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JasonGTR said:
Has anyone had a stock R32 RB26DETT tested on an air flow bench to find out what the volumetric efficiency is of the engine? I'm trying to go through some compressor maps of different turbos to find the right one for my needs. Right now, I'm just plugging in 90%. Hopefully someone will know the answer to my question. Thanks guys
That would be interesting to know..

But volumetric efficiency takes account of the cylinder filling and the entire inlet system aswell as the head, also the figures vary with RPM.
 

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JasonGTR said:
So I guess I'll just stick with my 90% calculations then
The RB26DETT makes peak torque at around 4800 rpm? That's an indication of where the best cylinder output is made, guestimate is around 95+ % @ 4800 rpm
 

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Jason use 75-85% it is more realistic, for turbo charged engines,, only N/A engines you would actually use 90% and in some cases 110%
 

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BBD said:
Jason use 75-85% it is more realistic, for turbo charged engines,, only N/A engines you would actually use 90% and in some cases 110%
Why makes you say VE is low as 75-85% ?

Modern DOHC engines peak past 90% easily - turbo charged or not.
 

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Why makes you say VE is low as 75-85% ?
Well I do my calcs using the worst case easier to make turbo choices and a smaller margin of error.

About performance Turbo engines and N/A, the flow of N/A will have a better VE because they run much higher compression ratios naturaly and a cooler combustion... with the Turbo engine the heat and low compression ratios are the main factor for lower VE.

Its great plotting in a theoretical VE of 95% plus as it looks great on the graph and when you try a 75% it doesnt look as impressive anymore.
 

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BBD said:
Well I do my calcs using the worst case easier to make turbo choices and a smaller margin of error.
A peak VE of 70-75% is a poor engine, even old single inlet valve engines do better than that.

About performance Turbo engines and N/A, the flow of N/A will have a better VE because they run much higher compression ratios naturaly and a cooler combustion... with the Turbo engine the heat and low compression ratios are the main factor for lower VE.

Its great plotting in a theoretical VE of 95% plus as it looks great on the graph and when you try a 75% it doesnt look as impressive anymore.

I think you have an incorrect defintion of Volumetric Efficiency.

The compression ratio will not affect the quantity of gas filling capability of the cylinder, which is what VE solely measures. It does *not* measure what you can do with the gas (such as compressing it and igniting it thus producing torque output)

The additional loss of theoretical power with a turbo engine vs a N/A has more to do with the combustion process, not the induction process.

That said, if you flow test a cylinder head - all you are doing is measuring the gas flow efficiency of the head - it does not represent the VE of the entire engine as the bore vs displacement, con rod length vs stroke has an effect on VE, also the entire inlet components such as manifold, plenum, t-bodies etc have their say.
 

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sorry to bring back a dead thread but here's my take on volumetric efficiency ...


first people have to take into account the energy content of the fuel they inject ... how much fuel are they injecting .... and the figure out how much hp are they making at the wheel ... its that simple .....


there is no other way of looking at it ......



higher compression ratio or higher turbo boost is doing what it does ... compressing gasses .... so that more could fit into a tiny space ..... once you ignite it all those hot gasses expand and thats the shockwave produced that pushes the piston down .... the more force the more power .....


but gasoline engine need to fight off detonation so thats why they are doomed to be low efficient engines ... until someone can come and find a way to cool the air comming in and allow 10x more air to be packed .... because more gasses compacted into a tiny area will produce more power ....


so its not about how much fuel and air you can get ... but its rather how much pressure you can create from the gas expansion that will result in higher VE ..... you could even run ultra lean without knocking if you cool the air to a more then decent level to achieve higher volumetric efficiency ... because less fuel and more energy extracted out of that cycle will result to higher volumetric efficiency .... more fuel injected lowers the efficiency usually .....
 

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I thought VE was a measure of how much airflow you got through an engine at speed... specifically at 1 bar of pressure, which is how some NA engines can score more than 100% (tunnel ram, anyone?), and why pressurised inlets have a higher resultant VE.

Theoretical power is easy - air +fuel.

Volumetric efficiency - Wikipedia, the free encyclopedia seems to agree (I should have started here, though)
 

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i do agree with the major part of that wiki article ....

Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio (or percentage) of what quantity of fuel and air actually enters the cylinder during induction to the actual capacity of the cylinder under static conditions. Therefore, those engines that can create higher induction manifold pressures - above ambient - will have efficiencies greater than 100%. Volumetric efficiencies can be improved in a number of ways, but most notably the size of the valve openings compared to the volume of the cylinder and streamlining the ports. Engines with higher volumetric efficiency will generally be able to run at higher speeds (commonly measured in RPM) and produce more overall power due to less parasitic power loss moving air in and out of the engine.

so many things in that article that i can agree with ... so here's how i see it .... higher pressure will help by alot ... and you dont need to inject tons of fuel in order to produce more energy ..... diesel proved it .... more compression and more pressure from the turbo's ... whats the result??? a more rapid expansion of gases .... that's what it is in short ... so drag turbo setup boosting 55psi have higher efficiency .. even if the turbo doesnt supply more air then it does at 30psi you are still compressing the air more to allow for a more brutal expansion of gasses ... now the thing is tuning your intake piping and exhaust system to promote faster exhaust removal is part of that equation .... there are still tons of things to discuss on such subject and i think people dont think about everything that is involved in the subject ..... heck i still dont grasp everything relating to that subject and its only a wild theory but then again lower fuel consumption and more power does sound like more efficient to me .....
 
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