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Thread: Volumetric Efficiency

  1. #1
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    Default Volumetric Efficiency

    I recently programmed car PC to calculate volumetric efficiency (VE) using RPM, MAF, IAT to calculate the air volume / min, and comparing the result to a theoretical 100% efficient engine (swallows 2260cc of air every four strokes).

    VE = calculated value / theoretical value

    Obviously being a turbo, the VE for the MZR is > 100%. I've so far seen a peak of 208%, basically meaning it's pushing 4701cc of air into the 2260cc of combustion chamber.

    I am calculating all this the same way one would for an naturally aspirated engine. I am wondering if there is another way of calculating VE for turbocharged engines, a coefficient or additional calculation that accounts for the presence of a turbo, so for example that 208% might in fact be 80% when one accounts for the turbo in the VE calculations.
    Last edited by Nexus; 24-06-2010 at 10:49 PM.
    "Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.

    "Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.

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    2261cc of air every four strokes.... Minus fuel volume

    1) Since the Stoichiometric Ratio/AFR is constantly changing, be it only a little; this means calculating how much of that volume is actually fuel might be a little bit difficult.
    2) If you use the MAP in conjunction with what you have now, you should be able to calculate the difference between NA and FI. With the FI setup the intake volumetric flow is much higher in order for the turbo's compressor to generate that pressure difference from compressor inlet and compressor discharge. With a few more numbers and a little maths you can work out what you want to. We see ~16.5PSI or 1.22Bar where as the NA will see just under 0psi/0Bar at best.... It's always vacuum. That number is probably going to be useful to you. Low Load, Medium Load and WOT figures for both engines; this way at least you can extrapolate something meaningful and build yourself a semi-accurate model of what the hell is happening.


    What you'll find is that the MAP pressure is ultimately why the Volumetric Flow Efficiency can be well above 100% for FI and is usually below 100% For NA. Some NA engines are able to achieve efficiencies slightly over 100%, but this requires some fairly skilled design and black engine magic trickery.
    Last edited by Jeev; 24-06-2010 at 11:22 PM.

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    Fuel rate is known (l/h), that can be converted to volume (hang on it is! convert to cc/min to fit the realtime calc)....then calculate the volume going into four strokes (divide cc/min fuel flow by half the rpm : four strokes = 2 rev per lungful)
    and finally in the realtime calculations subtract the volume of fuel per four strokes from the engine displacement.

    even at 90L/hr (!!), that's 1500cc/min, at (say) 4000rpm, that's 0.75cc; 0.1875ml per chamber.

    AFR and lambda are available in realtime. using AFR and lambda is working backwards isn't it?

    It would be an interesting brain tease to audit the system by working backwards from lambda and AFR. Hard basket. Might be possible to get useful result.

    I can take a baseline VE peak and plug it into the software and it from that can generate predictive readings. I'm skeptical of how accurate the predictive results are likely to be, I'm tempted to cite the patented predictive seal pressure test apparently utilised by BP on the Deepwater Horizon.

    But I digress. Building a map of norms and accurate predictive readings, in theory, one can then program the system to inspect data in realtime, and deviations outside expectations can be flagged.

    (a) good for early warning
    (b) good for knowing a mod achieves a goal.

    Most common modding - intake/exhaust, generally could be measured (standalone) by VE deltas : rpm, ala dyno.
    Last edited by Nexus; 24-06-2010 at 11:40 PM.
    "Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.

    "Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.

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    I did some editing, as trying to post and work at the same time means what I post barely resembles English... Anyway. I overlooked the instantaneous fuel flow rate measurement, which will work without resorting to calculating it yourself though AFR/Stoch methods. The VE is an extremely useful tool for analysing an engine, or it's potential and I can see why you'd be interested in getting an accurate value.



    Don't get me started on the Deepwater Horizon. Transocean's modelling of pressures and reservoir conditions was accurate, but under the instruction of BP they did something extremely dangerous and needlessly risky to save a little time and money. It didn't work.


    I see you did some editing too The best (worst?) I've seen from my ScanguageII is 125L/h WOT.
    Last edited by Jeev; 25-06-2010 at 12:01 AM.

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    I digress....

    Quote Originally Posted by Jeev View Post
    Don't get me started on the Deepwater Horizon. Transocean's modelling of pressures and reservoir conditions was accurate, but under the instruction of BP they did something extremely dangerous and needlessly risky to save a little time and money. It didn't work.
    I'd call it sabotage. It's seeming to be one of those faction one LIHOP (let it happen on purpose) type things. Or MIHOP (make it) BP seems to be something of a sacrificial lamb compromised from the inside to me. That's certainly true of the workers working the well. I am suspecting it's been working well at it's intended purpose; geopolitical pressure. 160,000 PSI on the geo side of it, I've read. That's 100x our fuel pumps.

    I have a better idea than most people what they were subjected to. "Nightmare well" quoting one worker. Because the work environment was a covert op, I would bet.

    The real problem now seems to be that we can't cap it or the whole formation might blow out. BP say it isn't happening, but the video's are out there for anyone with a brain to see. Oil squirting up from cracks in sea floor. It's gotta be eroding; I think that might be much of the discolouration (yes I know different oils/gases/methane slush etc). then they do braindread shit like knock the top hat off the well. Seriously. <edit> One way to unblock it - in a hurry? </edit>

    I think it could be fixed, but it's still going in order to apply political pressure. There's talk of nuking the well. Hope they don't split the plate open, there's a line of wells....

    ---------- Post added at 12:05 AM ---------- Previous post was at 12:04 AM ----------

    Oh man you got me started.

    Back to VE
    Last edited by Nexus; 25-06-2010 at 12:12 AM.
    "Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.

    "Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.

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    Agreed, but it went wrong long before the primary explosion. The decision that I feel sparked this whole series of events was made on the BP's behalf, to begin removing drilling mud and replacing it with seawater. The only reason for doing this is to avoid drilling mud contaminating the reservoir and skirting the need for a fracing process to reverse that contamination (Tens of millions of dollars. Big deal the lease was $544M/year and contractor costs were >$5M/day). This doesn't change the fact that the casing and BOP were not up to the task, but it was directly responsible for the blow-out of methane which caused the primary explosion. Sigh.

    The Deepwater Horizon has had what seems to be a rather negligent history dating back well over a year, covert or not. I could talk for an hour and still not scratch the surface of how poorly that operation was managed and run, however I think I should be getting back to my work and leaving your thread on topic. Just one point for my own curiosity. Deepwater Horizon's Blow-Out Preventer had a safe working rating of 15,000 psi; where did you get the reservoir pressure figure of 160,000 psi from?

    Also, in my opinion instead of wasting the last month giving false hope through the continual use of band-aid solutions and trying to recover their global image, BP and Transocean should also have started drilling a relief well to try and solve this issue the correct way. It may have taken 3 months until the completion of such a project, but it would have at least provided the means to plug and cap the crippled bore/well head they've left sitting there.

    In short Anadarko gone; BP gone or mighty close to if not bought out; the likes of Halliburton and Transocean left with huge holes in their pockets and the Environment inevitably raped.


    Last edited by Jeev; 25-06-2010 at 12:49 AM.

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    Quote Originally Posted by Jeev View Post
    Agreed, but it went wrong long before the primary explosion.
    In short Anadarko gone; BP gone or mighty close to if not bought out; the likes of Halliburton and Transocean left with huge holes in their pockets and the Environment inevitably raped.
    Indeed. I think most of the we didn't do this or didn't do that to "save money" is just bullshit. I've heard that one used for plausible denial before. Doesn't wash. Not on a deepwater rig like that. That's not just stupidity, that's willful stupidity. Controlled folly.

    It wasn't done to save money. It was done in order to stack the odds in favour of an "accident". Done so well that goldman sachs knew enough to sell their stocks and shortsell BP before the rig went down.

    Raped indeed. Why aren't the people with prior knowledge in custody?
    "Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.

    "Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.

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    My best guess is that no one above the level of Director or below the level of Manager will ever see legal proceedings from any aspect other than that of a witness or to give a professional opinion. The head washes it hands of direct responsibility; the tail did not have responsibility to begin with and the torso goes through the grinder... And as usual those capable will spin their web of bullshit and sneak away into the night.

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