Cam timing adjustments without dyno

[arghx7]

There's no standard calculation of volumetric efficiency. It's a term that's thrown around all the time and it's hard to compare one set of numbers to another. Generally speaking, it's the amount of air entering the engine relative to some reference condition. Put another way: it's how much air is entering the engine now, compared to how much engine "should" enter the engine based on its displacement.

The sticking point is usually the reference temperature and pressure. Is it referenced to intake manifold conditions, ambient conditions, or SAE standard conditions? Even in an n/a engine, manifold pressure actually drops as rpm increases due to restriction.

[banane63]

Originally Posted by Kodename47

Some smart arse gave me this formula to use to calculate VE:
[MAF in g/s] / (([MAP in kPa] x 1000)/(287.05 x ([IAT in C] + 273.15))x1000))/(121.9254 x [RPM]/3456x0.0283/60)x100


MAP can easily be converted from bar to kPa by multiplying by 100 if that's all you've logged.

And the result is... More than I've calculated with my complex formula !
123.18 instead of 122.99...
My formula :
[MAF in g/s] / (([MAP in bar] x 1000) / (287.058 x ([IAT in C] + 273.15)) x ( 1000 x [RPM] / 60 )) * 1000

My measures with Ecutek :
Mass Airflow (g/s) = 99.63
Manifold Absolute Pressure (Bar) = 0.97
Intake Air Temperature (°C) = 11
Engine Speed (RPM) = 4087

It shouldn't be grater than 110% according to HP Wizard :

http://hpwizard.com/volumetric-efficiency.html

A view of my calculated VRE :

[Kodename47]

I'd just look at it as a comparison rather than being 100% accurate. As you have the constants, the variables should give you a picture at what's going on so you can see whether things are improving or getting worse.

[SirBrass]

I know that @nelsmar had some cam timing optimization already. I'm just not sure that when he loaded it onto my ecu it was from a dyno baseline or from road tuning. Either way, it's been done.

Folks have commented already how my stock exhaust already has a different note to it. All readings have been good, so it looks like cam timing was nearly spot on.