EvilEvolution8 Posted February 13, 2019 Report Share Posted February 13, 2019 Hello Guys, i have a evo 8 with thunder ecu, bosch wideband knock sensor, gsc s2 cams, stock evo injector i attached map and log. i have two questions: 1) around 6700 rpm injector duty cycle going from 97% to 128% and afr goes very lean...why? 2) the knock level of cyl3 goes very high (i try to remove 2* but same situation)..why cyl3 is so different from others? i noticed that knock sensor is so close to cyl3...this can create that difference in knock level from cyl3 and others? thanks for support guys ss2.pclr ss2.llg Quote Link to comment Share on other sites More sharing options...
Ducie54 Posted February 13, 2019 Report Share Posted February 13, 2019 From what i can see your differential fuel pressure drops and your running out of injector flow because of it. I would check your fuel pump flow and voltage to the pump. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 13, 2019 Author Report Share Posted February 13, 2019 Yes Ducie I noticed... I have a walbro 450lt/h fuel pump... I'll going to check voltage at fuel pump! Quote Link to comment Share on other sites More sharing options...
Richard Hill Posted February 13, 2019 Report Share Posted February 13, 2019 Also, your fuel pressure does not appear to be properly MAP referenced as the Diff. Fuel Pressure does not stay constant, it drops non linearly with increasing boost... but as above, the fuel pressure is dropping way below acceptable values towards the end of the log. (167kPa). HTH, Richard. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 13, 2019 Author Report Share Posted February 13, 2019 I dont understand how differential pressure is calculated.. At idle and at 0 mgp the fuel pressure is around 290-300kpa.. At 130mgp the fuel pressure is around 430kpa... I think fuel pressure increased proportionally with boost... right? Quote Link to comment Share on other sites More sharing options...
Richard Hill Posted February 13, 2019 Report Share Posted February 13, 2019 19 hours ago, EvilEvolution8 said: I dont understand how differential pressure is calculated.. At idle and at 0 mgp the fuel pressure is around 290-300kpa.. At 130mgp the fuel pressure is around 430kpa... I think fuel pressure increased proportionally with boost... right? Differential fuel pressure should stay constant. static fuel pressure - MGP = diff. fuel press. (Edited for correction, thanks Adam) This is a log from one of our customers cars whilst under load. It shows the differential fuel pressure remaining roughly constant while the Manifold pressure varies. Just an example of a referenced fuel pressure. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 13, 2019 Author Report Share Posted February 13, 2019 My static fuel pressure is set to FP Sensor because i have a fuel pressure sensor on fuel pressure regulator... So...how ecu can know the static fuel pressure? Quote Link to comment Share on other sites More sharing options...
cj Posted February 13, 2019 Report Share Posted February 13, 2019 I think what @Richard Hill is pointing out is that where you go from off boost to on boost, your differential pressure drops (first circled bit in red). To me its seems like there is a 1 way valve somewhere in the boost reference to the regulator because once it hits positive boost, it holds differentials pressure correctly. However when it changes from boost to vacuum though, that manifold pressure change is not reflected in the fuel pressure. It looks like vacuum doesnt make it to the regulator but boost does. Because Fuel system type is set to FP sensor the ECU will compensate for this and it shouldnt have a real impact, but its a bit different. Normally the fuel regulator should allow more fuel pressure as the manifold pressure goes up - so it wants to maintain say 300kpa relative pressure. at 100kpa MAP (0kpa MGP) it allows 300kpa fuel pressure. Once you have 100kpa MGP (1 bar boost), your fuel pressure is actually 400kpa, but the relative pressure is still 300 (400 actual - 100 boost). This is because if you didnt do this and your fuel pressure was static 300kpa when your boost hit 301kpa, boost pressure would actually push air back down your fuel lines when the injector opened! Those closer you get to this point, the less fuel would flow too. Fuel pump voltage is easy to check as everyone else says, but it could be a couple other things too if that looks normal. Reason being that he doesnt back off the gas when it drops fuel, and 400rpm later it has recovered itself. If you look at the ECU estimate fuel consumption values, its ~2025cc when pressure starts to drop, is showing ~2060cc with the pressure dropped, but its doing fine holding 2080-2090cc consumption once it recovers. This means its not just a "more fuel during peak torque" thing - its supplying more fuel after that pressure dip that during it. Its also running 95%+ injector duty cycle so its quite possible that one or more of the injectors (maybe cyl 3?) sticks open for a bit or otherwise plays up due to the duty cycle, and drops pressure. I'd expect to see it go rich rather than lean though if that happened. I'm also reminded of a problem where the pressure reference hose from the manifold to the fuel regulator has resonance issues which can cause the regulator to think you have way less boost than you really do and supply the wrong amount of fuel. If you drop the boost level and fuel flow by say 20% across the board, do you still see a similar problem at the same RPM? This will isolate if its a resonance/rpm related problem or a fuel flow issue. You might need bigger injectors too but thats a decent cost so rule out the cheap stuff first. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 13, 2019 Author Report Share Posted February 13, 2019 Ok cj...i have full blown fuel pump hanger in my evo 8..fuel lines new (an10 /an6) and fuelab pressure regulator (fp sensor Is in regulator)...its all ready for IDs 1300x. I dont have any 1 way valve in my fuel circuit. Unfortunately i have a 1.2bar wg...i cant go under that. In my log mgp = -44 kPa , fuel p =310kpa , differential = 355 kPa...this is wrong...seems that the ecu add 44 to 310...but 44 is negative...not positive...the calc is wrong!! Quote Link to comment Share on other sites More sharing options...
ClintBHP Posted February 13, 2019 Report Share Posted February 13, 2019 3 minutes ago, EvilEvolution8 said: In my log mgp = -44 kPa , fuel p =310kpa , differential = 355 kPa...this is wrong...seems that the ecu add 44 to 310...but 44 is negative...not positive...the calc is wrong!! Because your regulator is rising rate the math channel on the Differential fuel pressure will add negative manifold pressures (actual rail pressure 310 as the regulator is reducing the fuel pressure 1:1 to the vacuum.) It will also take away positive pressure, this way the DFP remains a straight line in the ideal world enabling you to spot issues easily, just like Richard did on your log. I can't see the timeframe on that picture and I cant open the log from my phone he size of your feed line may be too large, when the regulator tries to raise the line pressure the volume of fuel the pump needs to change is too much for it to keep up. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 13, 2019 Author Report Share Posted February 13, 2019 Ok Clint...so you think that the wrong values of DFP is because the AN10 is too big ? Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 14, 2019 Report Share Posted February 14, 2019 2 hours ago, EvilEvolution8 said: In my log mgp = -44 kPa , fuel p =310kpa , differential = 355 kPa...this is wrong...seems that the ecu add 44 to 310...but 44 is negative...not positive...the calc is wrong!! I think what has confused you is Richard has misquoted the formula above. Differential fuel pressure is the pressure difference across the injector. You have rail pressure on one end of the injector and manifold pressure on the other end. So, the correct calculation is; Differential Fuel pressure = Rail pressure - Manifold Gauge Pressure (MGP). In general your diff fuel pressure control isnt great but if we ignore that big dip at 6700 it is probably acceptable since you have set the ECU to compensate for it. However that big sudden dip at 6700 suggests some part of the fuel system is failing. Either the regulator is getting stuck open, the pump is seizing/sucking air/cavitating or there is an intermittent bad electrical connection. I dont believe it would be an injector sticking as they are already at 100%DC before that dip. Of course you need bigger injectors or more pressure to get that DC down into a safe range but that is secondary to the mechanical problem you have. Quote Link to comment Share on other sites More sharing options...
Ducie54 Posted February 14, 2019 Report Share Posted February 14, 2019 Since you are running a fuel pressure sensor i would be setting your base fuel pressure by looking at your differential fuel pressure at idle once every thing has come up to temp. This way you don't need to take the vacuum hose off the FPR. Also are you running the fuel pumps off the std wiring or a another relay closer to the fuel pump Other things to look at is the ID of the fittings and line going to the fuel pressure regulator. Some brands of fittings have a smaller ID even tho the OD is what your after. Here is a link to Injector dynamics fuel delivery PRI videos that may help, there is 9 to watch. https://www.youtube.com/user/InjectorDynamicsTV/search?query=Fuel+Delivery Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 14, 2019 Author Report Share Posted February 14, 2019 6 hours ago, Adamw said: I think what has confused you is Richard has misquoted the formula above. Differential fuel pressure is the pressure difference across the injector. You have rail pressure on one end of the injector and manifold pressure on the other end. So, the correct calculation is; Differential Fuel pressure = Rail pressure - Manifold Gauge Pressure (MGP). In general your diff fuel pressure control isnt great but if we ignore that big dip at 6700 it is probably acceptable since you have set the ECU to compensate for it. However that big sudden dip at 6700 suggests some part of the fuel system is failing. Either the regulator is getting stuck open, the pump is seizing/sucking air/cavitating or there is an intermittent bad electrical connection. I dont believe it would be an injector sticking as they are already at 100%DC before that dip. Of course you need bigger injectors or more pressure to get that DC down into a safe range but that is secondary to the mechanical problem you have. Thanks Adam, Thanks for explanation. Now i Will investigate about fuel system problem. Can you have some advice about the knock question? Thanks Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 14, 2019 Report Share Posted February 14, 2019 12 minutes ago, EvilEvolution8 said: Can you have some advice about the knock question? Temporarily put some more conservative timing in there so you know it is not knocking, do some runs and adjust the individual cylinder knock level gains until all cylinders knock levels are reading as equal as possible. Quote Link to comment Share on other sites More sharing options...
EvilEvolution8 Posted February 14, 2019 Author Report Share Posted February 14, 2019 Ok Adam...i cant use now knock headphones . Before link i used haltech with same engine configuration and the engine no knocking with same ign table...with 100oct fuel pump gas I Will test after fuel system problem will be solved. Quote Link to comment Share on other sites More sharing options...
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