Auto electrics, Cars → Smoothing out a rough running V8

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Auto electrics, Cars → Smoothing out a rough running V8

August 1st, 2010 by Andrew

Holden 5L V8 engine conversions are pretty popular - this time in a 1985 Nissan Navara.

It’s been done pretty well, and drives nicely - except that it has a bit of a rough spot in the tune just above idle, which makes it hard to drive in slow traffic.

The engine runs a MAP (Manifold Absolute Pressure) sensor rather than a MAF (Mass Air Flow) sensor, and the chip in the ECU is an off the shelf one for a commodore (to match the aftermarket cam)

What this means is that any difference in the exhaust or intake plumbing vs the original commodore setup will have an effect on the tune.

Remapping the ECU on a dyno would be the best way to fix it, but since it’s only slightly out I decided to try an interceptor type tuning device on it.

This one is a Field SFC, which just takes the signal from the MAP sensor and adjusts it according to user settings for different rpm ranges.

It’s not the most accurate way to tune an engine, but it does let you adjust things in real time very easily.

The rough spot was able to be ironed out quite well with a few minutes playing around with the SFC, and it then functions as a handy LED tacho (since the car’s original tacho doesn’t work very well with the V8)