Fuel, pumps, and injectors

[shnazzle]

No the fpr is there to maintain the same fuel pressure throughout. I.e. compensate for the reduced flow of the injectors caused by pressure in the cylinders (load over 100% due to forced induction)

[lamcote]

See my previous comment. I'm thinking you would still need to adjust every map cell for fueling whether your fuel pressure is static or not. If so, where's the benefit? Does it allow some sort of automation of the mapping?

I've never done it, but I want to at some point, so the more I can pick up the better. But I don't want to be buying stuff I don't need.

[shnazzle]

Comes back to, why deal with X parameters during tuning when  you can deal with X-n.

You already have to deal with SO many parameters as it is. A lot less on a piggyback but still.

Air temp, altitude, moisture, wear/aging of components, tip-in enrichment per rpm range, deceleration fueling, octane, load, rpm, etc etc. Why make variable fuel pressure another one?

The stock system does adjust pressure via the pump, but it's not referenced. So Toyota has put all sorts of effort into making sure the duty is changed in large load  changes such as idle and WOT where there's either a lot of vacuum or none at all (effective fuel pressure difference of about 10psi) and the rest is in the fuel maps.

On boost, you're adding a new dimension, instead of an increase of effective fuel pressure with vacuum, you're reducing it. So the range of change goes from too much fuel at idle to too little at full boost.

Yeah you can sit there and map for fueling across the load/rpm range and extrapolate, but you can only adjust pulse so far before the injectors go static. When really pushing for performance, your injectors won't be able to flow enough fuel for what you demand in the time you have to demand it as the pressure isn't there.

At high rpm and high boost your window for fuel pulse is tiiiiny. A tiny window + low pressure = dangerous lean condition.

Alternatively, get massive injectors and cut the pulses down to shrew farts for the majority of load

[lamcote]

What fuel pump pressure adjustment is there in the stock system? Most people seem to say it is just 43.5psi but I certainly have seen occasional reference to standard fuel pressure being 43-50psi, is that it?  If so, do you know how this works?

[shnazzle]

Yeah the fuel pump itself pumps harder/slower via an ecu trigger, particularly in vacuum conditions.

I get the impression it's quite crude though and the "magic" happens in the mental sci-fi grade multidimensional maps Toyota uses.

[lamcote]

Will that be by some variance in the voltage supplied to the pump? If so do you think it could be measured?

[shnazzle]

I think that's exactly it. I suspect the components on the fuel pump housing are nothing more than a voltage regulator. But I could be doing a discredit to the manufacturer.

Easy to tap into positive feed to the pump and earth point on car I guess.

[lamcote]

Does the car report fuel pressure to the Torque app? I'm intrigued now.

Presumably the standard FPR in the tank must be set to physically limit pressure to 50psi and the pump is able to be turned down to deliver the lower pressure. If the standard FPR limited to 43.5psi there would be no way to increase the pressure beyond that figure no matter how hard the pump was run?

[shnazzle]

Torque does read fuel pressure but I think it's a calculated value and utter utter bogus.  s:) s:)

I don't think there's a hard limit and someone told me that you can make it function like a RRFPR by attaching a manifold reference instead of atmosphere referencr which it has.

[lamcote]

All very interesting.