Hi all, I am relatively new to Evo tuning. I have done 2 byte mod on my Rom and everything work s correctly. when I log both Load calc and 2 byte load, I get similar graphs.

I don't understand why my load decreases as my RPM goes up. I have a manual boost controller that is set at 20psi and is relatively constant throughout the pull. it goes from 207 to 185. Shouldn't the Load be the same throughout pull?

-Nate

 

You are seeing boost taper, with a manual boost controller it is normal.

 

Why is it tapering? In all the other turbo cars I have owned, there was no taper (regardless of boost control). Is there some sort of mechanical restriction on the evo, and makes it taper off like that?

Thanks

 

Reducing VE after peak torque.

 

That's the answer I was looking for. So Load is not actually load (ie boost) but rather an assumption of airflow and Volumetric efficiency.

Thanks

Also, any reasons why my boost tapers off?

 

In lay sense, even though mathematically incorrect, think of load as MAF hz/RPM.

The higher the ratio, the greater the load.

The stock turbo, esp VIII, seems to kick out the most air near peak torque which is why 30+ psi is relatively easy with such a small turbo. But as RPM increases the turbo just quits producing.

Taper really hurts HP #'s

 

So load value is just an arbitrary number that describes airflow/rev. I guess what i'm trying to figure out is what these numbers are, and how they relate to airflow. I understand that it's not a true measure of load (in the speed density sense). I'm just trying to relate the number to something tangible.

For now i'll jsut assume that these numbers correlate to airflow/rev (that would describe why it's tapering off).

Thanks

 

The load can be thought of as a percentage of normally aspirated VE.

Speed density load is arguably less "true" in the sense that it ignores the exhaust manifold pressure.

VE can be thought of as the ratio between the absolute inlet and exhaust manifold pressures.