The V8 Owners Forum -

Can FSE/Malpassi type Rising Rate Fuel Pressure Regulators successfully work in providing the extra fueling needed when going from 3.9 to 4.6 whilst retaining the 14CUX Hotwire system?

Triumph Rover Spares here in Adelaide, and Rover Parts in Ballarat, both use these PRVs in their 4.6 conversions in preference to "pricey hit or miss chipping options".

I was under the impression rising rate valves running off manifold vacuum pressure were only applicable to the analogue Flapper type efi. With digital systems like Hotwire by increasing the pressure under load you are getting more fuel in than the standard ECU expects which may throw it into Limp Home mode.

Then again I understand a lot of turbo car installations use rising rate valves.

Robrover wrote:
Triumph Rover Spares here in Adelaide, and Rover Parts in Ballarat, both use these PRVs in their 4.6 conversions in preference to "pricey hit or miss chipping options".

I find the 'pricey hit or miss' chipping options comment amazing!!! Having the ECU remapped to suit the new engine configurations is the correct way to do it!. Fitting a modified fuel pressure regulator is a bodge. How many car manufacturers use a common ECU and different PRV for different engines???

Just my humble!

Chris.

I also read you should not run rising rate on digital systems such as Hotwire, ok on flapper system.

Seems where ever you turn there is always conflicting information.

wont work unless you happen to need the same amount of fueling that it happens to give all the way through the rev range. Rising rate can be used if say your injectors are marginally too small to increase pressure and flow but to get the fueling right you still need to re-map either with chip or a mappable ECU. Assuming you run a lambda sensor the ECU will figure something is wrong and go into limp if you don't run a lambda then too much fuel will get thrown in giving bad running.