Graham Rudd Posted March 13, 2002 Author Share Posted March 13, 2002 Ok, so its likely that I'll have to do something about my fueling. So what exactly would I need? I already have an uprated fuel pump. Obviously I will need 6 UK spec injectors and a suitable resistor pack. Anything else? Fuel regulator? Injector rail? I'm guessing no to these, but you're the experts! What is/does an AFC do? Would it be a sensible addition? What if I decide to upgrade to a big single at some point, would it be wise to forego the 550cc route and go bigger? Any advice will be much appreciated, and I promise to stop talking about injectors if someone helps! Thanks, Graham Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted March 13, 2002 Share Posted March 13, 2002 >My AFC was cranked up to +50% fuelling, but it made no difference, That's becasue the AFC (Air Fuel Controller) only modifies the air flow signal to make te ECU use a different part of it's fuel map and it can only increase the air flow signal to the maximum the ECU can accept. i.e. Say the air flow reading from the MAP sensor is at 5V (maxed out at 19psi) the just because the AFC says there's 50% more air by increasing the voltage level to 7.5V going into the ECU the ECU still only see 5V thus no difference. Even if it could see the larger voltage level it's unlikely to have internal maps for fuel that relate to the 7.5V level of pressure (air flow) so again it would limit to the end of it's fueling table. So the AFC and all other simple fuel controllers can only EVER help at below WOT. IF you aint got enough fuel at WOT it's going to make NO difference what you set the AFC to, to try to increase it. >What is/does an AFC do? Hope the above helped out on that one. Pete Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted March 13, 2002 Share Posted March 13, 2002 >can only EVER help at below WOT I should clarify that I also mean at lower RPMs At high RPMs and wide open throttle it won't help you. They are normally used to help sort out little fueling problem lower down in the rev range (to smooth out transition of turbos etc) They are of use if you upgrade the injector size as then you really can get more fuel in and you need the AFC to actually attenuate the fueling at lower RPMs. Sort of the reverse to what most people think they are for. Pete Quote Link to comment Share on other sites More sharing options...
GavinL Posted March 14, 2002 Share Posted March 14, 2002 Quote: from TRL Performance on 3:28 pm on Mar. 13, 2002[br]I've built a prototype injector duty cycle monitor and combined AFR (monitors the stock O2 sensor so therefore has the limitations of the stock sensor) Anyway It shows you in a range of 16 LED's how hard the injectors are working 0->100% Now on my modded car running at 18psi, H20 and hybrids on 440cc injectors I see that the duty cycle is pretty much maxed out at WOT. Whilst crusing at 80mph it's at a steady 12% (shows just how much fuel you need when flooring it!) Anyway the intention was that with the combined AFR you could simultaneously monitor the O2 sensor and the injector duty cycle. If you saw the AFR begin to lean off and the injectors were maxed out then you know it time (sharpish!) to take your foot off the pedal and get some better fueling sorted. >Could it be possible that the ECU is running the injectors at a duty >cycle it believes is correct for the current conditions based on the >information its been fed, It will always do this, yes. It only knows what you (it's sensors) tell it. >but it turns out that the duty cycle is too low despite the fact that >there is a lot more 'slack' available to the injectors If this happens then you've modded something you shouldn't. If it senses more air flow or more load it will increase the duty on the injectors. Now with a FCD you've clamped one avenue open to the ECU as it still thinks you're at 15psi but other systems are telling it it needs more fuel. They are just not as accurate. This is why 18psi is the recommended absolute max (and even then only on cold days with good high octane fuel inside) Do this on a hot day with the same car and no extra charge cooling and start to worry.... In the end the ECU will increase the duty to maximum on WOT but the question is.... is the maximum it can deliver enough? Pete Pete, Have you re-run this test with 550cc injectors? Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted March 14, 2002 Share Posted March 14, 2002 No, as it wasn't my car that we modded to 550cc. Darrell has recently sold his Jap Spec MkIV and got a UK spec. Sorry. Pete Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 14, 2002 Share Posted March 14, 2002 The AFC does indeed work arse-backwards to what most people think - they are for leaning out the mixture You install bigger injectors, and you run rich throughout the rev range. Then you trim the fuelling down with the AFC to make it run correctly throughout the rev range. Pete, I agree that once the injectors are running flat out, cranking up the AFC will do bog all. The ECU can only make them run to 100% - if they are too small to deliver enough fuel at 100%, then that's that -Ian Quote Link to comment Share on other sites More sharing options...
Graham Rudd Posted March 14, 2002 Author Share Posted March 14, 2002 Pete, what voltage range does the O2 sensor output? I'd like to knock something together myself to monitor whats happening with mine. [OT] BTW Pete, I've managed to get hold of an ICD. Don't suppose you could recommend a good place for PC data acquisition cards? Preferably for a laptop. Thanks, Graham Quote Link to comment Share on other sites More sharing options...
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