Hey I have been wondering...
To get more power past stage 1 sometimes it is suggested to install larger injectors.
Is it not possible just to program them to stay open longer and burn more fuel to create extra power. Or is that essencially part of what a remap does?
With some choice parts and upgrades can you not just aggresivly map the car to increase power untill you are physically limted to how much power it can produce?
From what I have heard an AGU can make 250bhp pretty easy but as said it can start getting expensive.
A chip/remap will change the injection pulse / flow rate, 80% duty cycle is safe on most stock injectors and rail pressure setups. 80% fuel duty at 6000rpm+ would mean each injector would open for around 10ms per crank rotation, so every 100ms = 10 crank rotations which = 10 injection pulses, A bloody lot of work going on there in a short space of time. So going over 80% duty would bring the pulse time down to around 8ms per rotation which is barely enough time for the injectors to close before the have to open again. To keep the duty cycle low you can always add more rail pressure which will allow more fuel to be injected per pulse, keeping at the 80% duty. The down side of higher rail pressure on stock injectors can be poor fuel spray which will cancause the potential fuel efficiency to be very low. (This is based on the C20LET Vauxhall engines we have spent 10 years tuning, on OEM they used Motronic ECUs which is linked to the birth line of the Bosch ME7.5 ECU found in the DBW 1.8T engines, so fuel mapping is on similar lines to what I have wrote above))
The best way around this is greater flow injectors with matched rail pressure which will optimise the fuel quantity per pulses at 80% of the work rate which will keep the desired spray pattern to an optimum for greater efficiency. Plus keeping the injection duty cycle low will allow the closed loop side of the ECU to work to its full potential, such as if the lambda reading starts to tell the ECU that the engines is running leaner than requested, the closed loop function of the ecu would automatically add more fuel to get the desired lambda reading which the ECU is requesting to allow safe running, If the injectors are already on there limit the lambda reading cannot be brought back to a safe level, the engine will continue to run lean which can result in engine melt down.. bad times. It’s always good to have a window for safety. I melted my first Calibra turbo engine on a rolling road when the injection duty was mapped to 100%, now I would only ever use injectors at 80% max, I am well over 305bhp at 22psi and touch wood I have not had any fuelling issues due to the safe window I now have.
I good way for the AUM to gain power is to upgrade the injectors with a set from a 225 TT, and match the fuel pressure to the stock TT rail pressure. This injector and rail pressure combination is known to work really well up to 270bhp+ on stock BAM engines.
IMO go for a tried and tested combination straight from a higher BHP application.
Nick
