Stage 2+ back to standard

[iainalpine]

Morning guys. I am in the process of of fitting a Forge FMIC to the car and the only missing part will be to go for the HPFP next. My question is this, when running stage 2+ settings and you go back to the standard map will the car not be running really really rich due to the new fuel pump or when you go back will the duty cycle on the injectors cut rite back to allow for the extra pressure that is sitting behind them.
The reason for asking is that her indoors uses the car from time to time so i normally switch back to standard settings so she doesnt kill herself or the car. I dont want to be doing this if the car is not going to be running totally standard and maybe the fueling is not great.

cheers

Iain

[Hedge]

It should bemoe the  fine. The fuel pump raises the rail pressure so when the map requests more pressure it is there ready and waiting. In your case on standard it should never request the higher pressures so should be fine.

[iainalpine]

Hedge, is the fuel pressure on the fsi engine regulated in the normal way of using a vacuum pipe down to the regulator?
If it is then when switching back to standard map while running a HPFP the pressure will still be high. Injectors at idle will spray for roughly 2.5ms. With standard pressure behind them then all is good but with additional pressure behind them your going to get more fuel being pushed through in that 2.5ms. I was wondering that when switching back to standard map when using the HPFP, does the ecu reduce the duty cycle to say 1.5ms to compensate for additional pressure.

cheers

Iain

[Hedge]

With an uprated pump the rail pressure is around 140bar so no vacuum pipes going there.

The ECU should only provide as much fuel as the engine needs depending on the map used. If there is too much it should trim it.

If you look at the Illyun lean running thread you will see the effects of it going the other way beyond what the ECU can cope with on its own.

[four!]

Hi,

Often wondered how this works. like you say on a regular system when you maxed the injectors you could squeeze a little extra from increasing the base fuel pressure.

Why do people favour the High pressure pump over larger injectors? especially if its just the flow rate which is inadequate?

Im sure someone can explain how it works

Cheers

[Hurdy]

Hi,

Often wondered how this works. like you say on a regular system when you maxed the injectors you could squeeze a little extra from increasing the base fuel pressure.

Why do people favour the High pressure pump over larger injectors? especially if its just the flow rate which is inadequate?

Im sure someone can explain how it works

Cheers

In the case of the GTI the OEM fuel pump is linked into the camshaft via a cam lobe and so is RPM dependant. An aftermarket HPFP overcomes the lean issue by being able to deliver more fuel at the rpm you need it. Simply putting larger injectors on would probably make matters worse if you had an OEM pump as the pump wouldn't be able to deliver the fuel to the injectors at the right pressure and with having larger injectors the spray pattern would be compromised even more! The OEM injectors for stage 2+ are more than capable of supplying enough fuel. When Custom-Code developed their stage 2+ map on my car, they tried larger injectors and they made absolutely no difference whatsoever to the output levels.

HTH

[four!]

That's cleared that up then, its the pump that cannot maintain or reach the required pressure rather than maxing the injectors.

Cheers