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SR20DET Volumetric Efficiency Table Dips

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Running ECUMaster ECU.

Garrett G25-550 .49AR Turbo with 0,8bar internal wastegaste, stock cams, 700cc injectors @ 400 Kpa on walbro 255lph HP version, fuel pressure differential is pretty stable across the board, sometimes minor drops of about 7kpa at high rpm.

Tuned on street at spring pressure (180kpa). Lambda values follow lambda targets on full power runs at spring pressure 180kpa, what i´m trying to understand is why so many dips in the VE table specially at 180kpa around 3500 rpm thats exacly when i hit full boost. That dip is noticeble on my butt Dyno :) the the car pulls great.

Can this be a restriction of the stock intake plenum and throttle body ?

I attached an image with my lambda targets and VE table, any advice ?

Attached Files

It is possibly due to slight inefficiencies at that particular load and rpm - things like plenum size, runner lengths and diameters, exhaust runner lengths could be the cause.

Something else could be if the engine has some sort of variable camshaft/valve arrangement, if it was slightly out of phase with what the engine is actually requiring for airflow at that point.

What is the vehicle and engine?

I feel like it's a common thing with SR20s. VE falls and jump back up again around that RPM and load level, from my experience.

thanks for the replies

The engine is a SR20DET Blacktop, internals are forged but the plenum and TB are completly stock. The VTC was deleted because of the well know rattle :( , maybe its because of this since no longer as the 20* advance on the intake cam from 1050 to 5700rpm.

I will try to add some degrees of ignition timing on that load to see if it improves a little

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