VE of an A Series
Turbo Mini Forums

Has anyone measured / worked it out?

If not what do you guys assume?

AlexF

I always assume 82%.

It seems to check out reasonably consistantly when we get reliable dyno results.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

that low :oO

AlexF

VE?

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

Volumetric Efficiency


from WPidia

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 correctly, volumetric efficiency is a ratio (or percentage) of what volume 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 RPM, and thus power, settings as they will lose less power to moving air in and out of the engine.

There are several standard ways to improve volumetric efficiency. A common approach for manufacturers is to use a larger number of valves, see multi-valve, which cover a greater area of the cylinder head. Carefully streamlining the ports increases flow capability. This is referred to as Porting and is done with the aid of an air flow bench for testing. Today, automobile engines typically have four valves per cylinder for this reason. Many high performance cars in the 1970s used carefully arranged air intakes and "tuned" exhaust systems to "push" air into and out of the cylinders through the intrinsic resonance of the system. Two-stroke engines take this concept even further with expansion chambers that returns the escaping air-fuel mixture back to the cylinder. A more modern technique, variable valve timing, attempts to address changes in volumetric efficiency with changes in RPM of the engine -- at higher RPM the engine needs the valves open for a greater percentage of the cycle time to move the charge in and out of the engine.

More "radical" solutions include the sleeve valve design, in which the valves are replaced outright with a rotating sleeve around the piston, or alternately a rotating sleeve under the cylinder head. In this system the ports can be as large as necessary, up to that of the entire cylinder wall. However there is a practical upper limit due to the strength of the sleeve, at larger sizes the pressure inside the cylinder can "pop" the sleeve if the port is too large.

AlexF

When looking at compressor maps - I also use 82%, but review 80-84% to check if this takes anything to the edge. It is all pretty much pie in the sky anyways - as the valve sizes, CR, cam timing, etc are variables. It's deffo not over 84% though LOL

Reason for asking was exactly as TD says.... looking at Compressor Maps...

Not alot of matches for 200 bhp plus with hitting the surge line... but people are managing it

Either I'm missing something or its a case of theory vs reality not being equal!

Alex

AlexF

Calculation of the air flow is down to the engine capacity and revs, plus three efficiencies: VE, compressor and intercooler.

The most indeterminate variable that affects air flow is the Intercooler efficiency.

Agree with TD but VE can be reasonably well approximated.

The compressor efficiency can be read off the map.

But we have to guess the intercooler efficiency. Plus use an ambient air temp to calculate a temperature drop and thus air flow.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

running 9.5 psi and 150 bhp squirrel software,stepping up ve till i get to my bhp/psi level. crude software ,but interesting
--------------------------------------------------------------------------------

Engine RPM: 1000 1500 2250 3000 4800 6600 6750 6900
Vol Efficency: 88 89 89 89 93 96 92 87
Intake Temp: 64 65 73 80 92 104 104 104
Expected Boost (psi): 0 1 5.4 9.8 9.8 9.8 9.8 9.8
Pressure Ratio: 1 1.1 1.4 1.7 1.7 1.7 1.7 1.7
Airflow (lb/min): 1.5 2.5 4.7 7.5 12.2 16.5 16.5 16.1
Airflow (cfm): 22 36 68 108 176 239 240 233
Airflow (m^3/min): 0.63 1.01 1.91 3.07 4.99 6.77 6.79 6.6
Airflow (m^3/sec): 0.01 0.017 0.032 0.051 0.083 0.113 0.113 0.11
Airflow (kg/sec): 0.012 0.019 0.035 0.056 0.092 0.125 0.125

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

This is a print of my spreadsheet. I just change the numbers in red.

Attachments:

9.57kb

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

96% VE

and an intake of 104 degrees?!?!?

yikes!

Alex

AlexF

Attachments:

9.64kb

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

what would you make of a someone running more like 250bhp on a 1293cc?

Alex

AlexF

I would assume that they have managed to find an efficient turbo at 3:1 PR.

The GT1752 will do it (in theory).

Edited by Paul S on 19th Jul, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

indeed, i've been wondering what the VE will be on a K1100 lump, or a 7 port for that matter,

doesn't make choosing compressors easy!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Edited by robert on 19th Jul, 2007.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Thats a damn efficient intercooler...it wouldn't be Nics by any chance.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

AlexF

Degrees F?

Must be an Age thing?

Think my Gran still works in F...

Edited by Paul S on 19th Jul, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I bet Tom works in Kelvin :p

Alex

AlexF

Just a quick novice question..What kind of accuracy do you get with these formulaes + or - how many BHP?

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi