The engine is governed by the Modular Engine Management System Version 3 (MEMS 3)....it is a sequential, multipoint fuel injection system controlled by the Engine Control Module (ECM) yatter yatter yatter.......
The ECM uses numerous sensors to control the operation of the:
- Fuel system
- Ignition system
- Variable Valve Control (VVC) system (where applicable)
- Evaporative Emissions (EVAP) system
- Engine cooling fan(s)
- Air Conditioning (A/C) (where applicable)
- Steptronic Electro Mechanical Constantly Variable Transmission (EM-CVT) (where applicable)
The ECM uses the speed/density method of air flow measurement to calculate fuel delivery. This method calculates the density of intake air by measuring its pressure and temperature. The density signal, combined with the engine speed signal, allows the ECM to make a calculation of the air volume being inducted and determine the quantity of fuel to be injected to give the correct air/fuel ratio.
Fuel quantity control.....
The precise quantity of fuel delivered is controlled by the ECM adjusting the duration of the injector open time. To achieve optimum performance the ECM is able to "learn" the individual characteristics of an engine and adapt the fuelling strategy to suit.
(Theres also a sensor (cant remember its damn name!)that alters the fuelling to maintain the correct mixture of exhaust gases).
Theres a whole barrel of **** that mems and the ECM moniter and alter to suit but theyre the main "suspects".
I think that might help to answer the question as to "lean fuel delivery".The other types of MEMS are similar in operation to mems3 but only vary in number/types/position of sensors...but its all basically the same.
IMO just the usually throttle/induction kit/exhaust/fuel pressure regulator upgrade isnt goint to affect the ability of the injectors to provide enough fuel as they can just open for longer.My experiance is with fords though,and only when a 1.6i was modded up to a 2.0i/phase3/with massive turbo/intercooler/water injection etc etc etc ....did it require larger injectors...when it was just upgraded to the 2litre half engine+phase3 head the RR report showed fuelling wasnt a problem at all......only with the turbo did we need a new fuel pump/regulator/filter/injectors PLUS another injector in the manifold!!!!lol
So to sum up....minor upgrades-dont bother.With massive overbores/forced induction then probably.
The first time I read the ad it seemed a bit misleading,but when I read the other time I could see what he was on about.
Any thoughts anyone???
I have been known on occasion to be wrong!
Just wanted to add......no offence to the "F" owners...its just Ive only started reading up on the TF....so I have NO IDEA about anything "F" related so I thought it best not to guess!
But I think its N1ck who has a 197??bhp F......so he should be able to advise on whether you need larger injectors or not,as 197bhp is certainly getting into the realms of needing larger injectors due to the extensive mods required for such an increase!
I agree Spike, the MEMS deals with this. The MEMS does make a couple of assumptions though, for instance the pressure of the fuel in the fuel rail. I seem to recall that the MEMS assumes it is 3.2 bar, but the fuel pressure regulators (FPR) are a bit hit and miss and the actual pressure can vary down to 2.8 bar. There was talk of uprated FPRs (which were simply crimped OE spec ones - not very scientific!) I have one of these in my garage, and Rob Bell had one fitted until a RR day showed that his car was running too rich. You can also get adjustable FPRs (aka Power Boost Valve) - these seem to be better, but do require a RR to set them up properly (this is what the seller on eBay is hinting at i think). Another assumption is the capacity of the fuel injectors.
This is how i understand it:
Sensors tell the MEMS the air speed and density, MEMS uses this data (and others, like composition of exhuast gases) as well as the assumed 3.2 bar pressure in the fuel rail to calculate when and for how long to activate the fuel injectors. The process then repeats for the next cycle etc etc. MEMS is adaptive, but only within it's original programmed perameters, so doing something outside these perameters could result in MEMS getting very confused. We have seen this happen with the uprated FPRs on Rob Bell's F - he was loosing bhp because the FPR was over pressurising the fuel and MEMS could only back off the fuel:air ratio so much. MEMS knew there was an issue as the exhaust gases were showing unburned fuel, but couldn't compensate enough for the mechanical change in the system (it was still using the assumed 3.2 bar figure as changing this was outside it's perameters).
I suspect that the same could happen with these injectors - if they are a larger capacity, then they will deliver more fuel in a given time period, enrichening the mixture. MEMS will detect the richer mixture (from the composition of the exhaist gases) and back off the 'on' duration of the injectors - up to a point. Beyond which it won't cope and the car could end up running rich and loosing power (+ fuel economy).
Sounds on the money to me Andy.You are correct on the ecm backing off the fuel to maintain the gas ratio in the exhaust...as far as it can!Same as on the Fords.
Thank for checking it through as I still have the L plates well and truly on!