Matt1436215419 Posted February 17, 2013 Report Share Posted February 17, 2013 Hi there, I'm running a 4AGE turbo with Link G3 and Link EBC solenoid. The MAP limit has started cutting in occasionally now - never used to. All I've adjusted recently was made up a stronger bracket for the actuator, as the old one was flexing and cracked. If it ever overboosted before it would reach about 18psi before cutting out. Searching the forums I found the following post - "If you are running a turbo or supercharger and were running upto 15psi boost (200kPa) you would set the limit just above that at 205kPa." ...but a search of Google is telling me 200kpa is 29 psi. May be a really stupid question, but am I missing something here? Need to find out which is correct as my boost gauge is reading 14psi (what it should be and always has been running) and MAP limit is set to 240KPA I think. The turbo is definitely not running 30+ PSI (only a t25g turbo), so is the ECU seeing a reading of 35psi or 18psi for the MAP limit to kick in at 240KPA? MAP limit is very sporadic, can kick in higher in the revs or sometimes lower around 4000rpm when boost is nowhere near 14psi (reading off my gauge), or sometimes every time I put my foot down (generally WOT) or have days like today where I drove it for an hour with the laptop hooked up and it ran perfectly the whole time. Any ideas on this?? Thanks -Matt Quote Link to comment Share on other sites More sharing options...
Simon Posted February 18, 2013 Report Share Posted February 18, 2013 The map limit in our ECU is an absolute reading so 100kpa is atmosphere 200kpa is one bar of boost (15psi) So if your limit is at 240 it should be well clear. I suspect there might be some other issue causing a miss fire. Fuel supply or ignition. Quote Link to comment Share on other sites More sharing options...
Matt1436215419 Posted February 18, 2013 Author Report Share Posted February 18, 2013 Ahh that makes more sense! Will fuel or ignition issues cause the MAP limit to kick in before 240kpa? It is definitely the Map limit as with PCLink running it had a very minor misfire at 14psi and the "MAP Limit Activated" window popped up. Does the map limit only ever activate when it hits 240kpa, or also as a safety feature if the ecu senses another error (ie fuel or ignition fault)? Quote Link to comment Share on other sites More sharing options...
Matt1436215419 Posted February 18, 2013 Author Report Share Posted February 18, 2013 Ignore the above - just managed to download all the datalog info... MAP limit is lowered due to the ECT rising, so it kicks in at 204kpa. ECT seems quite erratic once the throttle comes on. Off throttle (at any RPM) it will sit quite steady at 87º - 88º. As soon as the throttle comes on it will jump anywhere from 87º to 99º. Is this normal? I would imagine some difference would be normal but 10º seems a lot. This variance is over a 3 or 4 second period, not sustained revs or during a burnout Thanks -Matt Quote Link to comment Share on other sites More sharing options...
Simon Posted February 19, 2013 Report Share Posted February 19, 2013 I would expect it to be nice and stable. Might be an indication of some bad earths. Quote Link to comment Share on other sites More sharing options...
Matt1436215419 Posted February 19, 2013 Author Report Share Posted February 19, 2013 Awesome, thanks Simon, thought it seemed a bit odd. Gives me a good place to start. Pretty sure I put a new ECT sensor in when I built the engine as the factory ones crap out every so often, but I'll check that out too. Quote Link to comment Share on other sites More sharing options...
Matt1436215419 Posted April 14, 2013 Author Report Share Posted April 14, 2013 Finally got to the bottom of this after putting it off for so long - found a wire with a small split in the plastic insulation around it about 5" out from the ECU plug, checked which it was and sure enough it was the yellow wire going to the ECT sensor. Insulation had separated a bit and the wire itself must have been rubbing on something or just getting interference from something to effect the reading. This also fixed a stutter the engine has had for a long time, on very fine throttle (ie cruising at 50kmh) it would miss every 5 or 10 seconds or on idle it would miss and the revs would drop a couple of hundred rpm. Never bothered me enough to try and find the problem, but stoked both are fixed now and turned out to be something so simple! Quote Link to comment Share on other sites More sharing options...
Cameron Moore Posted April 25, 2013 Report Share Posted April 25, 2013 Excellent. Glad we could help you diagnose it. Small intermittent faults like that can be a real pain to find. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.