Jump to content


  • Content count

  • Joined

  • Last visited

  • Days Won


Davidv last won the day on November 4

Davidv had the most liked content!

1 Follower

About Davidv

  • Rank
    Advanced Member

Recent Profile Visitors

1,224 profile views
  1. Closed Loop fuel trims

    That's really interesting Mapper, I've been meaning to have a play with that CLL gain table but havent yet. I think you've just piqued my interest however! I'll try those other numbers for a starter and see how it differs.
  2. I've got an injector timing table set to 240deg BTDC end of injection all the way through rev range. With some changes to cam timing I decided to test 400deg btdc above 2200rpm / redo some testing at different angles. And as soon as I make this change, when my car gets to that rpm where the injector timing advances a lot the car bucks and lurches and stutters. If from here, I set all of the timing to either 240 degrees or 400 degrees, its fine again. But when it's on that transition point, things get weird. It seems more prominent at low load, I'm guessing because its an issue if start of injection is beyond a certain point? I suspect that an injector event gets skipped, the car hesitates and rpm drops and same thing happens again. (It's a really aggressive lurching of the car, and definitely not just caused by the effect of different timing) If I set the table to all 400 deg or all 240 deg the car drives smooth and fine. I can supply logs and a basefile as an example if needed. Thanks David
  3. Modelled fuel + MAF questions

    Thanks for the detatiled answer Adam! Appreciate that you took the time to test this, thanks.
  4. It doesnt seem to, but it may be that the change is so small that it isnt able to be seen with a map sensor of this scale. And possibly because my copper line is too smaller diameter as well. I've parked this idea for now, I'll revisit it later on when I can redesign the pipes a bit better. But I'm just about there with my MAF based tune, might need a test driver at some point while I tinker if you're keen!
  5. Modelled fuel + MAF questions

    Hey guys, I've recently gone back to using a MAF sensor, and I notice that with modelled fuel there is the option to have as a load axis "Air per Cylinder Measured" Which is awesome. Since this figure comes directly from the MAF sensor I am assuming that a lot of the calcs for modelled fuel get bypassed. I also notice there's a seperate category for "MAF IAT" Rather than regular IAT, I assume this does the IAT calculation differently too. However I have a few questions. 1. Options for load axis in the fuel calculation are either MAP, BAP, or Off. I've set this to Off. Would that be best option? 2. Which of the modelled fuel settings now get ignored, since you're measuring air directly? I get the feeling that it air per cyl measured is used as part of the calc which then still generates "air per cyl estimated" which is what the fuel calc runs from? I realise that MAF isnt the suggested option but it offers some benefits while I'm doing some experimenting with cam timing, so I'd just like to get it setup to "best practice". So any advice/info on how it calculates would be appreciated. Thanks David It's pretty cool having grams/cyl as a load axis because the values are quite linear... This was the MAF basemap that I put together based on observation of my MAP based tune, and car ran awesomely on it! It's now changed shape a little after the first iteration of tweaking it but it's still very linear.
  6. One thing that I've been curious about lately is advancing cam timing at part throttle for better fuel economy. So I did some tests, where I set the timing all to 0 degrees, then 10 degrees, etc, and then went for a drive at a set rpm on the same stretch of road with cruise control and closed loop lambda turned on. Interestingly, 0 degrees advance clearly gave the best results. At first I felt satisfied with this, but then the nagging problem in the back of my mind... Toyota documentation says that advancing the cam "about half way" yields best economy. So I took a closer look at the logs. When the cam advances, at same throttle angle, the MAP sensor reading goes up! In one case, up 60% higher. So the ECU is of course trying to dump fuel in, and pulls the ignition timing back which is why the economy was notably worse even though Closed Loop Lambda was trying its best to salvage the situation. Why does the map sensor value jump up? Because of internal EGR, when you introduce cam overlap, the low pressure in the intake manifold and high pressure in exhaust pulls exhaust gas back into the inlet manifold which raises its pressure. So this is obviously why the factory ECU uses a MAF sensor rather than MAP - A map sensor is including some "dirty" air in its readings (which has no oxygen left in it) where as a MAF only reads fresh air coming in. Since the factory ECU only has a narrowband sensor, using the internal EGR method allows it to run a greater airmass to reduce pumping losses while still operating at 14.7:1 as the recycled air has little or no oxygen left in it. Pretty clever. So I thought I'd wire a MAF sensor back into the car. But this presents the next problem, how do you get the 0-5v signal of the MAF into a grams/sec that the ECU needs for a calibration curve. So for starters I was just logging raw MAF voltage output, so depending on airflow it spits out somewhere between 0-5v to ECU My ECU currently has load source as MAP sensor, and one of the values it logs as part of the modelled fuel calculation is "Grams of fuel per cylinder Estimated" So we need to turn this into a grams per second, so some maths to create a custom field in Megalog viewer and now I've got Grams per second which I can compare to voltage: Which I can then use as an axis on a scatter plot, which shows me a very rough outline of a MAF curve starting to form... So I rough out a voltage vs grams per second to put in the calibration in Link And then go for another drive and do same thing again in megalog viewer... Starting to look better! (It would be cool if PClink allowed Maths functions like this... Just saying) Then from here have updated the MAF curve again to suit the trend seen there. I think another 1 or 2 iterations of this and I'll have that low airflow area cleaned up. If not, I will just switch to map or alpha N based tune around the areas where it sucks. But from here, once the MAF sensor data is accurate I'll build secondary ignition and fuel tables which have MAF as the load axis. Then I can start experimenting with cam timing at part throttle some more, without my load axis going bananas (map sensor value changing a lot) In order to find the sweet spot for economy though I really need to play with a few variables at once. As when you're introducing EGR gas, you might start getting misfires at 16:1 where as this is most economical if you are running no overlap. And when you introduce EGR gas you need more ignition timing as it slows the burn. So I think I'm gonna make a little box that communicates over the CAN network that has a few potentiometers which log as virutal 0-5v which I can use as trim tables for ignition table, cam angle, goal AFR, and maybe a little display that shows fuel economy. So I can very quickly go through a lot of combinations while someone else drives with cruise control turned on. It's a lot of effort to make only a small iterative improvement to the car's economy, as it's already getting 7-8L per 100km if driven nicely. But it's always bothered me that I've had no way to quantify how to best set the part throttle cam timing so I'm thinking there's something to learn here yet. I'll post the results once I've got my MAF curve dialled in nicely and I've put together a CAN box. Also, at the same time as wiring in a MAF I thought I'd wire in an exhaust pressure sensor. I wasnt sure what sort of pressures I would see on an NA car, so I bought a 30psi sensor. I drilled a hole in a spare wideband bung, which then goes to a line of copper tube to cool the gas, then to a rubber line, then to the pressure sensor. Results are interesting! At high RPM (Or high mass airflow more specifically) the measured pressure actually drops. Down to 91kpa which was quite literally the last thing I was expecting hahaha. Thoughts as to why? I think the airspeed past the hole in the wideband bung is creating a venturi effect and pulling the air out of the hose, rather than telling me what the pressure is. So I am thinking that having an angled bit of pipe internally that either faces towards or against the flow will prevent this from happening. Or maybe upsizing the diameter of the tube that I am using as it's very small. (maybe 2mm ID) The resolution isnt very good with a 30psi sensor so I'll perhaps switch it out for one from an NA car instead. I've got a spare Toyota one here somewhere. It doesnt really show any results that I was expecting though, so I might just ditch it from here. Was worth it just for curiosity's sake though! More useful on a turbo car though of course.
  7. 3uzfe e throttle

    I had a similar problem when initially trying to get my Toyota e-throttle calibrated, with it initially not calibrating and then when it did, I'd get the fluctuations. In my case it was solved by replacing the TPS, since then has been perfect. I am thinking that on a normal car the TPS only moves as often as the persons foot does, but with e-throttle where its controlling idle speed and other similar situations. It's swiping over the same part of the resistor back and forth almost constantly so "wears out" quicker but the problem only becomes apparent at certain throttle angles. I'm using Altezza e-throttle and apparently it's common for the TPS to need replacing.
  8. Interpolation "OFF" option

    Interesting, I could see this helping to make mixture map work a bit better. As sometimes you get massive see-sawing between cells due to interpolation.
  9. Using DI9 and DI10 as canbus

    Hi, I see in the documentation that the pins for DI9 and DI10 can alternatively be used as canbus on the Xtreme. I've been redoing some of my loom / reorganising some things so I've set aside these two wires for an upcoming can project. But I would have thought I'd need to specify them as being allocated to can in the DI list? It doesnt show up any option to allocate them to anything can related, do I just leave them "off" and then from there, configure in the CAN screen? Thanks David
  10. Pot Tuning Box

    I've been thinking about making something like this using arduino / canbus. As I've got an interesting situation when trying to tune intake cam angle on a VVTI engine for best fuel economy. When using MAP as a load source, when in steady state, when I advance the cam. The map sensor reading goes up. Because when there is cam overlap the exhaust gas pulls back through to the inlet and raises pressure. So in response, the ECU pulls timing and adds fuel. So I have to readjust these with every adjustment to cam timing so its very finnicky to try find best setting. Also since EGR gas is being internally introduced, indicated AFR may need to change as there is some non oxygenated air present and you'll misfire if you've got a goal AFR already on the lean side of stoich. (Which this leaner setting may be best when no EGR gas is involved with low overlap) Also when there's EGR you need to add more ignition timing. Having a box of trim pots would help speed up optimizing this immensely as I've got 3-4 variables that I need to adjust at once. Tuning for best economy is a lot more challenging than just for max power in each cell! If there was an off the shelf option I'd be keen on it.
  11. EWP is an advantage because you can disassociate your water pump speed from engine speed. So you dont get cavitation/pumping losses at high rpm or insufficient circulation at low rpm... Think about what happens in a normal engine when your thermostat is shut. Coolant still circulates around the block, its just partitioned the engine coolant circuit from the radiator one. when you use an EWP as a thermostat, you have no choice but to introduce new cool coolant every time you want to circulate coolant around the engine. Depending on where your coolant temp sensor is, this can lead to see-sawing of the EWP turning off and on when the temp sensor sees this coolant change. In my opinion, best way to use EWP is to set it to pretty much constantly circulate engine block coolant and then just keep a thermostat in place to do the job of a thermostat. Which is to introduce cold coolant when necessary.
  12. Fuel Trim table 4 missing

    Either way it doesnt matter though - because your main fuel map represents that one cylinder, and then the other 3 represent variations away from it.
  13. Fuel Trim table 4 missing

    Are you talking about monitoring how much the engine is adding or removing fuel to reach lambda target? If you have closed loop lambda turned on, then you can monitor "CL Lambda Fuel Corr. (%)" You dont need to setup tables for this, it's a value you can just look at in a time plot etc. You only need to setup those trim tables if you are wanting one cylinder or another to receive more or less fuel than the rest, which doesnt sound like what you're wanting to acheive here.
  14. How does CAN logging / refresh rate interact?

    Ahhh cool thanks! Yes that's what I was meaning, if via CAN the ECU could output the data at a greater rate than 100hz to an external item. Rather than CAN info coming into ECU. 200hz would be cool for some situations, so I think I'll give it a try.
  15. Hey, I've not played with can bus stuff before, but looking to set something up for sake of interest. One thing - ECU is limited to log at 100hz internally, or 40hz when streaming to a connected PC via the cable. How does this work with CAN, when logging at maximum data rate? If you were only logging a few values, would it potentially go higher than 100hz? I'm not sure how the rate of transmitting / receiving the frames relates to the data rate, and whether that potentially means higher than 100hz sending/receiving of frames. Thanks