"Volumetric Efficiency" of an engine.

[penguin45]

1/ Somebody please explain what this is!
2/ Would anybody know what the VE of a 2227cc E series 6 cylinder engine might be?

Thanks,
P45.

[Battles]

This came up on a Facebook group I'm in a few months ago, a guy in the group who builds dragster engines posted this link:
hpwizard.com/volumetric-efficiency.html
The easiest part to digest is this table:


Why do you ask?

[penguin45]

Thank you, Battles. I had figured out that it was to do with the possible volume of air being sucked into an engine, but no context.

For my sins, I'm the Technical Director of The Wolseley Owners Club. Normally, we manage to get people workinga again (sometime miraculously) with some pretty ancient machinery, but I do have a request from a chap at the moment who would like to get 150bhp out of a six pot "E" series in a Wolseley Six. That's fine, but the "E" appears to be an evolutionary dead end, apart from the Aussies with the P76. Downton apparently (briefly) did a tuning kit to take it up to 135bhp, but I can't find any information on that at all.

Cheers,
Chris,
P45.

[MrOtter]

This seems like a good excuse to copy'n'paste a section out of my dissertation on turbocharging... hopefully some of this is useful/makes sense!

"The term volumetric efficiency, or VE, is very important term to understand. Maximising an engine’s VE raises its potential for horsepower and RPM. With the exception of fuel and ignition modifications, most of the traditional aftermarket high-performance engine parts are essentially for raising the engine’s VE. Forced-air induction is all about increasing VE; but what is Volumetric Efficiency exactly?

An engine’s VE is a comparison of an engine’s calculated, or theoretical, volumetric flow rate of air, versus its actual flow capability. An engine has a fixed displacement, for example, 300 cubic inches, and that displacement will theoretically flow 300ci every two engine revolutions (a four stroke engine must rotate twice for all cylinders to complete all four cycles). In theory, there would be a linear relation to airflow and engine RPM where doubling the revolutions per minute would double the air displaced by the engine during a certain time period. If an engine were able to flow exactly as much air during operation as the theoretical calculation says is possible, that engine would have a VE of 100 percent.

In reality, 100 percent VE is difficult to achieve, but not impossible – in fact, many forced induction applications can exceed it. There are many factors that impede the engine’s ability to meet 100 percent VE, some intentional, some unavoidable. For example, an air filter and its housing will typically impede intake airflow, but an engine wouldn’t be operated without air filtration for fear of major internal damage.

The common methods used to increase VE in naturally aspirated engines are things like larger valves, more valves per cylinder, improved intake manifold designs, enhanced valve timing using different camshafts, free flowing exhaust systems and more. But perhaps the most limiting factor to VE is time.

The critical factor here is simply how long the intake valve can be held open. The calculation for 100 percent VE assumes a full cylinder charge of air without regard to time, but during actual engine operation the intake valve is only opened for a short time. The higher the RPM, the less time the intake valve is off its seat; therefore actual VE is not a constant. It’s typically an efficiency ratio at one spot in the engine’s operating range.

If a simple calculation was done to express, in real time, just how long an intake valve is opened, it places the challenges to make horsepower into perspective. Assume an engine was operating at 3,000RPM, and it had a camshaft designed with 230 degrees of intake valve duration, measured at the crankshaft. The intake valve would only be opened for 0.0255 second. The reduction in valve open time is inversely proportional to engine speed. This same engine now operating at 6,000RPM would only have the intake valve opened for half as long, or 0.0127 second. As can be seen, volumetric efficiency will limit the upper engine RPM potential of any engine design as it simply can’t breathe well enough in the short period of time dictated by the mechanical events.

The reason turbocharging has such a dramatic impact to engine performance can be better understood using this concept of volumetric efficiency. In a turbocharged engine, time still limits how long the intake valve is open, but if the intake pressure is greater than atmospheric pressure (boosted), then more total air mass can be forced in during the valve opening. The quality of that air is improved for combustion purposes because its density has also been increased. The combination of boost pressure and increased air density compensate for the time-limiting aspect of the valve events and allow some boosted engines to achieve well over 100 percent VE. However, when maximising total horsepower output, even turbocharged engines will benefit from many of the very same design improvements done to enhance VE in naturally aspirated engines.

As mentioned above, a given engine will have better or worse VE over the RPM band. Every engine will have its sweet spot, which is the point in an engine’s design where, at full throttle, the volumetric efficiency is at its highest. This is typically the point where peak torque will be found on the torque curve. Since VE will be at its highest point, maximum fuel efficiency, or minimum BSFC (Brake Specific Fuel Consumption), will also be at its peak. When calculating the proper turbo match, VE is a crucial element to consider, as it is an important contributor to determining the airflow demand of a given engine."

[TurboDieselWeasel]

In short: it's the amount of air the engine can draw. In percentage of it's cubic capacity. The more air, the more fuel can be burned. And the more "bang" can be made.

A n/a engine with 100% or more VE is VERY bl00dy insanely good! And probably needs some wild tune! It's a huge subject, ram-charging, intake/exhaust stream pulsation & valve overlap etc. - it all adds up. A turbocharger is obviously an "easy" way to get 100%+ VE. But has other disadvantages, of course. In the end a charged engine will always make the most "bang". Just not as spontaneous as a "uncorked" n/a engine. See the tractor-pulling example. Watch some videos and count the time it takes them to spool the massive turbochargers...! But then a n/a race engine will hardy make any power below a few thousand revs.

The table above is good! I woul have assumed an E-Series engine to be somwhere between 60-70% in std. tune.

I sugest to read a good book on the subject of engine tuning - there's so much aspects to it (and to improve VE) - it's impossible to cover here. And very interessting!! Max. power and power that's usable on public roads are two very different matters, p.e.

[hfstuart]

The bad news is that the 6 pot E Series wasn't developed much but the good news is it already makes 130lbft in a very low state of tune, you have plenty of ccs to play with and all engines respond to old school modification.

I'm guessing the head is pretty much a lengthened version of the 4 pot e-series one. At least some people have tuned 1750 Marinas and what works for them should work for the 6 pot too. An increased compression ratio, ported head, Custom reground cams, 6 branch exhaust and different carbs (Pair of 2" Jag SUs perhaps?) should be more than enough to do the trick. Mappable ignition would help make the most of the rest of it. You shouldn't need much more than 6000 rpm so the much of the engine can remain standard

Sadly these mods would not be cheap - maybe £1500 so he might be better off going forced induction with a supercharger. Failing that what chance of getting a 2.6 Crank from Oz or RSA ?

[penguin45]

Sorry for the delay, away over the weekend. Fantastic information, thank you all very much.

P45.