While data logging, I notice a phenomenon I hope someone on here can explain.

I've noticed that a difference exists between 100kpa fueling at 50% tps vs 100kpa fueling at 90% tps (both tps values in PE). At both tps values all other values are equal (rpm, cts, gear, etc).

For example, let's say I'm cruising along in third gear (MT) and I ease into the throttle bringing the tps value to 50%. PE is entered (threshold set to 35%), Map is maxxed out at 100, WB afr will read approximately 12.0 and egt will begin rising slowly to about 1200degF. Now I increase the tps to 90%. ECM remains in PE, Map is still maxxed at 100, afr jumps to 12.5, and egt immediately shoots through the roof.

It is my understanding that when you reach 100kpa (depending on elevation) your engine will not to flow anymore air (based on rpm of course). If that is the case, engine load should not change with the tps% as long as kpa equals 100 (or max for your elevation). Obviously something is changing because my afr and egt are showing more load at the higher tps% value.

Would someone care to straighten me out?

355 vortec
$61 mask
6MT

 

Where is the thermocouple for the EGTs mounted? It could be a fuel distribution issue that your seeing.

 

CYL #5 - 2" from exhaust port (1-5/8" SLP shorty headers)

If I stay on it too long I can feel the motor start to miss and loose power. Haven't logged any significant knock counts in those areas either.