CamB Posted October 3, 2016 Report Share Posted October 3, 2016 As part of my endless stuffing around / learning... G4 Storm, 4 cylinder sequential, 8 valve BMW M10 adding a turbo, and still some time away from running.1. I have older Bosch "363" injectors - a very low impedance (0.7ohm) ~650cc injector - with the recommended 2R2 ballast resistors. I want to estimate dead times and have the data from Motec base files. Presumably this data is for the injectors operating peak and hold, and my expectation (and a bit of googling) suggests this would change if operating as saturated with a resistor. Is anyone aware of any rule of thumb for adjusting the dead times for the addition of ballast resistors?My alternative plan is to establish a baseline deadtime at typical running voltage using a method explained on the internet (deadtime should be accurate if you can - at low pulse widths) switch injector rate from once per cycle to twice per cycle without AFR changing, or if you can add a trim (eg in AFR overlay table) which is accurate). Then drop voltage and adjust deadtimes for lower voltage to maintain AFR... lots of stuffing around. Any reason to think the alternative wouldn't work fine?2. I have been thinking about the traditional fuel map and how it relates to VE, and just wanted to check I understand:- modelled fuel (on a G4+) takes the VE, MAP, [engine size, injector characteristics, fuel type and pressure] and for an AFR target works out the required injector pulse (taking into account some other adjustments)- traditional fuel has a ms for master fuel that effectively bundles the items in "[ ]" (other than dead time and non-existent minimum effective pulse width), and if you use the AFR target table it then adjusts this for target AFR, plus adds the other adjustments. As a result, would I be right in saying if I have accurate injector characteristics and compensations (especially for IAT) in a G4 that:- I could look at the fuel table as a VE table times say 50% (ie you would see 50% where you would ordinarily expect 100% VE). There's no magic in "50%" either - it could be 75%.- a good rough idea for the master fuel would be the calculated ms from around the internet (which references pulse width for a given engine size, injector size and VE) divided by 50% (or 75%, if that's what was chosen). Eg I work out ~4.5ms, so should try 9ms if my 100% ve area of the fuel map has 50 (or 6ms if its 75). Thanks for assistanceCam Quote Link to comment Share on other sites More sharing options...
Scott Posted October 4, 2016 Report Share Posted October 4, 2016 Hi Cam,I'm not aware of any rule of thumb for adjusting deadtime when adding ballast resistors. I think your alternative plan sounds sound. Others who have done this may add their comments. Your idea for the fuel table also sounds like it would work. However it may be just quicker to go to an approx mid VE point, set the table value to 50, and then adjust the master fuel value to achieve the target AFR.Scott Quote Link to comment Share on other sites More sharing options...
CamB Posted October 4, 2016 Author Report Share Posted October 4, 2016 Thanks.I expect you are right on the fuel table - I was always planning on having to adjust master fuel as per the instructions but was ever hopeful it would get me in the ballpark. Quote Link to comment Share on other sites More sharing options...
CamB Posted October 10, 2016 Author Report Share Posted October 10, 2016 So as an update I may be updating to an G4+ Xtreme and repurposing the Storm to another car.Is the G4+ Xtreme ok with 6A peak and 1.5A hold (what Motec seems to think those injectors want)? Quote Link to comment Share on other sites More sharing options...
Simon Posted October 10, 2016 Report Share Posted October 10, 2016 Yep the Xtreme will go up to 10 peak and 3 hold. Anything under that is mint. CamB 1 Quote Link to comment Share on other sites More sharing options...
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