Scott33

I think I know the purpose of the charge temp approx table; I have read the help and other threads on the subject multiple times. I'm not sure what in my question gave you the impression otherwise. The point of the table is that both IAT and ECT contribute to the actual air temperature and thus density of air entering the combustion chamber. My question was just whether one can hold IAT constant and vary ECT (and monitor lambda) in order to tune the charge approx table instead of holding ECT constant and varying IAT. On the surface it seems that either method should be valid. As you point out, at idle (low load/RPM) the ECT contribution is higher, thus varying the ECT should show a large change in lambda if the charge temp approx table is set to 0. As the value is increased (and the corresponding values in the fuel table adjusted) then lambda shouldn't change as the ECT varies. My question is really just if changing the ECT would have other effects on how efficient the engine that wouldn't (or shouldn't) be captured by the charge temp approx table (but instead by ... ? what? a general ECT compensation table?)

My car has a controllable thermostat that can vary from 80C to 110C. Will I get reasonable results tuning the table by varying ECT instead of IAT? Or does ECT have other effects on volumetric efficiency that would yield poor results? I do have a separate oil thermostat and oil cooler so I expect the oil temperature to be fairly constant. I use case is road racing, so warmup really isn't that important. OTOH correct performance when ECT is varying (maybe I'm in a draft, maybe it's just hot outside and the radiator can't keep up) is important. I have gotten by for the last year with just warm up enrichment by ECT at 70C and below, and charge temp and IAT comp tables filled with 0.

Currently traction control allows for 1 or 2 tables. It'd be nice if it could be extended to support: 1. One table 2. Two tables, chosen by switch 3. Two tables, interpolated by third 2D table 4. Two tables, interpolated by third 3D table 5. Two tables, added. For example, if table 1 calculates to 5% slip and table 2 calculates -2% slip, then the actual target is 3%. 6. Two tables, multiplied. For example, if table 1 calculates to 5% slip and table 2 calculates 80% multiplier, then the actual target is 4% (0.05 * 0.80 = 0.04). Note this seems very similar to #4; but would actually support percentages greater than 100%. The first three are the standard for boost control. The last two would provide some interesting ways of allowing multiple variables, such as combining lateral G, speed, throttle position, and a driver operated traction dial (not just a switch). I would like this for G4+ (since there is no G4x Force GDI)

I see G4x already has this feature, but it'd be great to add it to G4+, and I don't think it'd take much (if any) CPU resource to make it happen (unlike math channels). Basically, if we could use the duty cycle of a GP PWM output of any aux output, then it'd allow for more complex logic when deciding boost, or accelerator position, or traction control slip target, or ... As a corollary, it'd be nice if Virtual Aux had GP PWM capability too so the output of those tables could be used as well without having to dedicate an Aux output to this purpose.

I have a RWD car with a limited slip. All four wheelspeeds are plumbed to digital inputs. I race on road courses with fairly low power (200rwhp with a 2500lbs/1130kg car+driver+fuel). I would like to tune traction control to help with mid-corner to corner exit. What should I use for the non-driven and driven axle speeds? Average or max? I started with average, but I do notice that on initial throttle, the inside wheel speeds up a bit before the LSD. I'm wondering if I should be using max, or maybe ideally I should be using "outside wheels". I know I can't set that up in Link, but I have another ECU that can process CAN messages and spit out whatever I want, so I could add inside/outside detection to the other ECU and just send back outside wheel speeds back to the Link ECU. Any ideas/tips? Thanks!

You can set Knock Control->Knock Setup->Ign Retard Limit to 0.

I emailed that along with a 6k rpm run to tech support. Hopefully it reaches you. I can really only test this on a dyno or race track, and I don't easily have access to either right now. I think the VVT is a red herring. I have tried lobe angles at -10 and +10 relative to what is in that tune (which is how far the exhaust VVT moves at 3k RPM), and it still drops off at the same point. Also, the 6k rpm run has VVT movement and works fine. I'll repeat what I said before - the GDI Pump Control is actually DECREASING while the pump pressure is dropping. It's almost like it's being forced down by some clamp. Thank you for the description on Spill Valve On Angle. I didn't realize the pressure keeps is closed until it isn't needed.

Firmware 5.6.7.3631, software 5.6.7.3632, though I didn't see anything in the notes for 5.6.8.3671 about GDI changes. I have a weird issue where the fuel pressure tracks just fine at 6k RPM, up to 0.0696 g fuel/cyl with a 5.188ms injector duty cycle at 200 bar, but it won't track at 3k RPM, above 0.055 g fuel/cyl with a 4.070ms injector duty cycle. It's a Bosch HDP5. It seems that it should be able to handle the same fuel flow rate per cycle in either case. Interestingly, it looks like the GDI Pump Control makes no attempt to make up for the fact the fuel pressure is falling (see log). I will admit most of my GDI parameters are guesses, but it seems the GDI Pump Compensation table can (crudely) mask deadtime (at one voltage) and pump calibration. I have tried other lobe TDC angles to no avail (usually makes it worse). I also tried other maximum cc/lobe values (thinking perhaps I was exceeding a the upper limit on duty cycle) but it didn't help either. As it is, the cc/lobe * # of lobes * fuel g/cc is well above the required numbers above. If it matters, the pump is driven by the exhaust cam, which is trigger #2 and VVT. However there are VVT changes on the 6k RPM run and pump control is relatively steady there. Attached is a log where RPM was held at 3k RPM while throttle was progressively fed in. Also, what is "Spill valve on angle?" Is it a minimum amount of time to energize the pump? In which case why is it different than "Minimum pump angle?" losing_gdi_200ang_250cc.llg

What exactly is the "GDI Pump Control" logged parameter mean? I assume it is the PID correction applied to the GDI pump control model (after utilizing all the lookup tables), and not the actual duty cycle of the GDI pump itself. I haven't seen it list any values below -10% but I don't know if that means values <-10% simply aren't logged or whether the PID is clamped to -10%.

Can I use multipoint group on a direct injection engine? It seems like the 2nd firing would be at exactly the wrong time (and probably wouldn't work since I think only one of two injectors can fire at a time, given the needs of the high voltage driver for GDI injectors).

To answer my own question - 1. Measuring deadtime is about measuring actual lambdas and pulsewidths at two different settings (same RPM/load, but different fuel amounts), and seeing where that goes. 2. Measuring fuel charge cooling coefficient is about measuring target vs actual lambda and making sure those track each other. Of course you get to throw in charge temp approximation table too, but that involves changing air or water temp and observing changes in lambda. Luckily I have a lambda sensor!

I noticed the help on how to tune fuel charge cooling coefficient is similar to how I would tune injector deadtime - vary target lambda and observe actual lambda (well, more specifically measure fuel/air ratio at various injector pulse widths to determine what the pulse width would be for 0 fuel). Assuming I can't measure my injector deadtime properly, is there a suggested way to determine those two parameters? I was thinking of changing the target lambda and testing two different load points, under the assumption that deadtime would have a greater effect at lower loads while fuel charge cooling would have a greater effect at higher loads. I assume I'll have to go back and forth a couple times to iterate on what the answer is. Or maybe (since I'm doing this on a GDI motor) I can vary the target fuel pressure and use the same load point so I can either have the deadtime be either the major or minor factor in the injector's pulsewidth depending whether I'm trying to measure deadtime or fuel charge cooling. Also, is fuel charge cooling relevant to direct injection motors? Is the effect smaller or about the same as port injection?

Has anyone connected their Link ECU to a Dynapack OBD adapter? I was wondering if the dyno can log the ECU data stream or not. Might make it easier to see the effects of ignition or fuel changes as it relates to power output, esp as the air temp is increasing. I know Dynapack has a separate CAN adapter, but the shop I'm using doesn't have that. They only have the OBD adapter, and I'm not sure if it expects K/L-line or if it can read CAN too. Thanks!

In the documentation for the gear ratio table, it says "Gear Ratio = Engine Speed (RPM) / Speed sensor frequency (Hz)" and "Engine Speed/Speed Sensor Frequency". However, as far as I can tell it's actually Engine Speed (RPM) / Wheel speed (kph). This is what is actually displayed in the Runtime Values box under the Misc tab.

You can find BMW wiring diagrams here: https://www.newtis.info/tisv2/a/en/ If it's anything like the N20 sensor, it should be hall effect with the pull up resistor enabled. I think it's dealer's choice whether you choose rising or falling edge; at least with the N20 the pulses are just spikes, not related to the size of the tooth. Are you running port injection? I didn't think Link ECUs could run piezo GDI injectors, let alone 6 of them.