K20 JDM LPG Stepwgn RG1 Tuning

Discussion in 'Honda K-Series' started by jd1959, Tuesday 8th Jan, 2019.

  1. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
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    @SpeedyGee

    Hi all I'm in a position of not having a lpg tuner near I have asked our local LPG guru if he would have a look at the tuning. Hopefully any other people with LPG conversions that are competent and know the dangers of working on gas will feel free to chip in.

    The car is an early RG1 Stepwgn k20a no EGR from factory, electronic throttle, 155hp 4 speed auto about 230k km. Running Honda 0w-20. Ruthenium NGK plugs, no errors found in HDS. In general wants for nothing mechanical. Valve adjustments regularly.

    Stag qbox basic, hana red injectors, AC STAG R01 reducer
    LPG filters recently done liquid and gas, low pressure hose to injectors rerouted and replaced due to abrasion.
    I run the gas up to 4500rpm then change to petrol to try and save the valves a bit, There has been some accelerated wear but there is still adjustment. The savings on fuel cost over the last 100k km by far covers a replacement head in the future.

    Now that the background is covered.

    I get an 'injectors open on full engine load check lambda' error.
    On the DB1 map I'm reading lean in areas.

    I would like to run about 5-10% petrol on the car to facilitate valve cooling if possible on this ECU.

    None of the other values on the ECU have been changed (RPM correction, reducer temp correction petrol portion etc.)

    Thanks for any input :happycrying:.

    Zack Advanced. D B1. Gas Controler. Multiplier.
     
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  2. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    Hi Zack, I can see one problem that maybe the cause your 'injectors open on full engine load check lambda' error.

    I'll post some info on it when I am home this evening.
     
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  3. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    upload_2019-1-9_22-10-15.

    @jd1959 you see the difference between petrol injection times and gas injection time is over 2ms?

    That's too much of a difference, it needs to be about 1ms.

    So at idle if petrol injectors are at 3.35ms then gas injectors should be about 4.35ms.

    What's happening at the moment is that, even at idle the gas injectors are already opening a fair bit. So when they get to higher revs they hit the limit of opening times and hence an error condition is raised.

    The reason they are opening so much is that nozzles are too small for the engine. This is a rookie mistake by the installer.

    Easiest fix is to increase the gas pressure and re run the auto calibration until you get the difference to about 1ms between the petrol and gas timings.

    There is an adjustment screw in the centre of the reducer that takes a 4mm Alan key. There should be markings on the reducer telling you which direction increases the pressure.

    Once you have the gap correct, you should delete/clear the current map and create a new one. If you are worried about doing this you can tune the existing map.
     
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  4. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
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    Thanks for having a look and spending your time replying.

    The reducer spec wise can put out a max of 1.3bar I'll whack it up to the max and see where we go if I can get the timing down. I'll have a look at the injectors to see if there is a nozzle installed I'll report back. I can remove or drill out on your advice if present. Then calibrate and remap the system

    In looking the Hana red can put out max right around 40hp/cylinder which is right up against the power of the engine. Same goes for the reducer the R01 seems to be max rated for 110kw the engine is about 115kw. It looks like the kit installed is just barely up to spec for the engine. I don't mind running a bit of petrol to avoid leaning the engine if need be, were far past the payback point and I'm now more concerned about keeping the head intact for a few more years before changing the car.

    Once I have the pressure turned up and the system calibrated best I can I'll stick up new images and we'll go from there.

    Thanks again for your help.

    Zack


    Edit: 11:00
    Right instead of looking at the gas pressure yet, I had a look at the injectors - the reducer already drop in pressure a good bit under high load. The injectors had the one stripe 39hp calibration insert in. I removed those and re-calibrated the system the injector timing is now about 1.1ms apart on a 650rpm idle. I'll recollect the gas map during the school runs this afternoon and see how well the reducer behaves on high loads and adjust from there.

    What are the max values (ms) I should be looking for on the gas injectors?

    Thanks again
     
    Last edited: Thursday 10th Jan, 2019
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  5. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    It depends on the injectors, every make and model is different. The LPG ECU will detect when they have maxed out.

    Correctly tuned they should be ok for the majority of the rev range.
    - - - Updated - - -
    This is perfect

    Good move, you have a better understanding of the LPG system than I'd assumed.

    Do you have an OBD reader? You will need one to check how well tuned the LPG system is by monitoring the STFT and LTFT values.
     
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  6. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
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    Thanks, this is due to necessity rather than desire, there are only a handful of LPG guys in the country, at this point any I would trust are a couple hours away. Unfortunately there aren't many resources on gas installation and tuning so my knowledge is a bit spotty. I appreciate your watchful eye so to speak.

    I have a clone HDS that I can use. I don't know what I'm looking for in regards to fuel trim. Hopefully I'll get the multiplier sorted this morning on the daily school runs. Then do a bit of reading about fuel trims and stick up what I find on the obd reader.
     
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  7. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    You are looking for the sum of STFT (Short Term Fuel Trim) and LTFT (Long Term Fuel Trim) to be close to 0 as possible across the rev range under all load conditions.

    Lets say you start off looking at the idle load, if the STFT is +10 and long term is +5, sum of these is +15, so this tells us that the main ECU is wanting to add a fair bit of fuel, so we change the map value at this point to add more LPG, when you do this the STFT will come down, wait and let the LTFT to settle too and then see what the new sum is. So that the fuel trims at idle is now sorted.

    Now you take the car for a drive (ideally someone else driving) and you monitor the fuels trims under different load conditions and you adjust the map to keep the trims in low figures close to zero (so like in the range -5 to +5).

    You now need to take the car for a drive and look at low/light load, medium load and heavy load. You tell the driver what load you are working with and the driver can try and put the car in that load range whilst you monitor and adjust the map values. When you covered the three load areas, smooth out the rest of the graph (you won't have adjusted all the points on the graph right, only certain ones), change the values so they transition to the next range gradually. So let's say you have mid ramge load point of +10 and you have a high load point where you had to add more gas say +25, fill in the other values from mid to high load so they gradually get upto +25.

    Once you think you are done tweaking the map, carry on driving around for a while longer whilst you look for spots on the map where STFT falls out of the desired range.

    Drive the car for a week and then recheck the fuel trims.

    This process takes a fair bit of time but most installers that I know skip it out and only throw on a basic map and hope the customer doesn't notice. As long as the check engine light doesn't come on (due to fuel trim being out of range, too lean or too rich) they get away with it.
     
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  8. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
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    Ok, I think I understand. Are these corrections inputted in the' MAP corr B1' screen?
     
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  9. SpeedyGee Club Manager Club Staff

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    I missed out a step sorry. This process is going to be tricky to describe via text. Let me have a think about how best to do this.
     
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  10. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
    523
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    Back after messing about a good bit and a normal hectic weekend, I'll put up screen shots hopefully this evening.

    It went as follows:
    Reset PGMFI, relearned idle, deleted petrol and gas maps on lpg controller, calibrated nozzles on a hot stable engine, took the car for a good long drive on petrol and got a pretty detailed petrol map, drove on gas up o 4500 it was fine, on running gas the whole RPM band I was still getting an injector open on full error. I gradually added up to 30% petrol addition to upper area of injector time and RPM band also about 3-7% for 2500-4500rpm band to hopefully facilitate a bit of cooling on the exhaust valve. Adjusted gas multiplier curve to match collected petrol map, checked STFT and LTFT to make sure they were reasonably close to 1.00 plus or minus about .05 on several different conditions.

    Overall pretty happy on a hot engine.

    One thing I have noticed

    Temperature this morning lpg kicked in at 30c reducer, engine at 54c (HDS), 1.09 pressure, fuel trims all over the place.
    Left and did 8 miles of 60mph driving and a school drop off (pressure climbed up to 1.32, engine trims .8's STFT and 1.01 LTFT , 2500rmp)
    Final stable reading Reducer 50c engine 83c, 1.13 (about injector calibration pressure), 1.01STFT and 1.01LTFT at idle and reasonable close together during driving on hot engine.

    Is that normal behavior for the reducer pressure, temp or temp sender? Is this adjustable on gas temp, reducer temp, or gas pressure corrections?

    Thanks for any input.

    Zack
     
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  11. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    Yes don't worry about pressure at different temps etc, the LPG ECU has algorithms to cope with that.

    Sounds like you've got a good map there, good job Zack!

    How long did all this take you?
     
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  12. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
    523
    306
    On and off about 300km of driving and about an 1hr of idling, many hold on let me just change these two points on the map, plus a fair bit of reading. It's not a quick process.

    At this point I'd like see the stock map. I'm curious about the the i-VTEC engagement point given injector opening times take a huge jump around 4000rpm to 17ms up from about 12ms all in the MAP of .8 to 1 bar. If I can switch to petrol at that point and run 2-7% petrol the rest of the map bar idling I think I'd be thrilled.

    Thanks for your help - its much appreciated.

    Just to add I do wish the installer had gotten an OBD based ECU, the Optima Alex is far easier to use as it keeps track of the fuel trims itself and with a bit of time really dials in on a good map with almost no input. The Stag is stuck relying on injector pulse comparison and a separate diagnostic with human input. I'll have learned for next time.
     
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  13. SpeedyGee Club Manager Club Staff

    England Speedy Birmingham
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    See that's what you won't get going to LPG installation place. They just slap on a basic map and skip out the lengthy on the road mapping.

    Sounds great in theory huh. Not always that great in practice though. As I mentioned before I still create maps by manual tuning.

    You did really well :Thumbup:
     
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