World's first FT86 Anti-Reversion,(A/R) Header

[burdickjp]

Originally Posted by wparsons

And how do you know when you've made an improvement or made something worse?

Volumetric efficiency goes up or goes down.

[Andrew025]

Originally Posted by bur****jp

Volumetric efficiency goes up or goes down.

How is that measured?

[burdickjp]

Originally Posted by Andrew025

How is that measured?

PV=nRT

[Andrew025]

Originally Posted by bur****jp

PV=nRT

What I should have said, how can Kool measure that directly?

[zooki]

Originally Posted by Andrew025

What I should have said, how can Kool measure that directly?

Maybe if he gets better gas mileage pulling a trailer full of brush?
😊

[burdickjp]

Originally Posted by zooki

Maybe if he gets better gas mileage pulling a trailer full of brush?
😊

Can we be constructive? We've all beet wrong before, and we'll all be wrong again. Ridicule is not the most effective way to help people. The guy wants to play and is willing to share. Let's encourage him in the right way and provide positive suggestions rather than just calling his ideas stupid.

[steve99]

Originally Posted by Andrew025

How is that measured?

http://www.romraider.com/forum/viewt...hp?f=15&t=6258

[burdickjp]

Originally Posted by steve99

http://www.romraider.com/forum/viewt...hp?f=15&t=6258

That thread makes the common mistake of saying that volumetric efficiency is a ratio of volumes. It's not. VE, as defined by SAE J604 is actually calculated as the mass of air delivered through the intake valve with respect to a mass of air equivalent to the swept volume (not total volume) at ideal density.
I'm sure there are some people here who see problems with that in practice. For instance we were just discussing how charge can be delivered through the intake valve and then out the exhaust port. It would contribute to the VE calculation, but not combustion.
This is why I prefer using the ratio of the mass of charge in the cylinder when the intake valve closes over the mass of the swept volume at ambient temperature and pressure. That all may be unneccessary, though.

Here's an intriguing thought about MAF cars, which is new territory to me. I've previously only tuned with MAP and TPS based load (speed density and alpha-n for those who really care). The MAF is actually measuring the mass of air going in. It inverts the axes you'd otherwise use as load to say "at this load and RPM you have this VE." It would be saying "at this mass flow and RPM you have this mass flow".

So what we really need is something independent of the mass flow to use as an axis for the sake of comparison. You could use MAP, which would emulate speed density, or TPS, which would emulate alpha-n.
In this way you would log MAP, TPS, RPM, and load. You'd make a table with MAP as one axis, RPM as the other, and load as the interior values. You'd do that before and after changes and subtract one from the other. The difference is where you're getting better or worse VE.
You'd do the same for TPS for the sake of correlation.
You could invert that if you wanted to, and instead of maximizing mass at a given MAP or TPS, you could minimize MAP or TPS for a given load.

This is conjecture. I haven't done it yet, but it should give you something akin to VE comparison.

[Ultramaroon]

Originally Posted by bur****jp

That thread makes the common mistake of saying that volumetric efficiency is a ratio of volumes. It's not. VE, as defined by SAE J604 is actually calculated as the mass of air delivered through the intake valve with respect to a mass of air equivalent to the swept volume (not total volume) at ideal density. ...

I went down that rabbit hole earlier today but realized in the end absolute accuracy is irrelevant in this exercise. The before-after delta is still quite useful.

[burdickjp]

Originally Posted by Ultramaroon

I went down that rabbit hole earlier today but realized in the end absolute accuracy is irrelevant in this exercise. The before-after delta is still quite useful.

For the sake of cam timing tuning, all we want is something we can use to get a delta.
I was thinking about it more last night, and I think calculating the mass of the swept volume for a given manifold pressure and intake temp and comparing it to load is probably the most correct. I believe that the romraider thread had discussed that at one point.

[Koa]

There is life after a forest fire. Love the info here guys thank you

[KoolBRZ]

Started a new thread in the software tuning section, since this has come so far from the original thread. http://www.ft86club.com/forums/showthread.php?t=86569