Dyno tuning TD42i - please educate me

[Cuppa]

I understand that there are 3 factors which the good tuner has to work with. Boost pressures, fuel delivery & EGT’s. The art is in getting the best power/torque output whilst keeping EGT’s at safe levels.

What I don’t understand is how, on a TD42i the tuner can alter fuel delivery as my understanding is that the factory intercooled models have an ‘electronically controlled’ fuel pump (whatever that really means), so presumably increasing the amount of fuel delivered is not as simple as turning a screw?

So how do they actually do it?

[nissannewby]

They are only partially electronic, max fuel and delivery rate can still be altered to a point. With your particular setup the tuner should not be touching the fuel screw but only making boost compensator adjustments (aneroid).

[Cuppa]

Thanks Matt. So is this boost compensator the ‘doodad’ on the side of the turbo, has what looks like a vacuum or pressure operated linkage (I suppose that’s what aneroid means in this context?) . I’m guessing the higher the boost pressure the higher the amount of fuel? What sort of adjustment does it have? (Don’t worry I’m not going to touch it myself, just be good to understand).

Also what do the electronics control in the pump? Fuel delivery timing?

[nissannewby]

The one attached to your turbo is the wastegate actuator, the small line is the one in which your manual boost controller will be tee'd into.

The boost compensator is on the top of your injector pump, it has a small line going to the top of it from the inlet of your intercooler. So basically as boost pressure increases fuel is increased. The boost pressure acts on a diaphragm which is connected to a pin (kind of like a assisted brake booster), this pin has a ramp machined into it, this pin then acts on another part of the pump which alters fueling accordingly.

The pin is machine in away that by rotating it will change the ramp angle and depth.

The electronics control timing as you said.