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
    537
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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
    537
    314
    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

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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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  14. Whisker Version Club Member ★ ☆ ☆ ☆ ☆

    United Kingdom Bristol
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    Don't understand much of this, but the nozzle is an inherent part of each injector, so there is nothing that can be swapped out without changing the injectors (would this be so hard for you to do though, especially since you have the software to recal them?) As mentioned, cranking up the pressure regulator in the vaporizer would help get more mass flow through the nozzle throat by increasing the vapour density; mine needed quite a few turns to make much difference when I watched the installer do it. Liquid LPG sits above 10bar at usual ambient temperatures, so there should be no shortage of extra pressure available.
    Are the exhaust valves known to burn out? Do you have no faith in Flashlube-type systems? As far as I can see, most hydrocarbons pyrolise when they get very hot and convert to lighter hydrocarbons, and some left-over solid carbon, I therefore suspect almost any cheap cooking oil would do as a valve lubricant, and the ridiculous price of upper cylinder head lubricants for LPG systems is unjustified. An advantage of cooking oils is that they would be unlikely to have any impurities in like metals or sulphur that would poison a catalytic converter, and because they are pennies per litre, the oil could be run through at a higher rate.
     
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  15. SpeedyGee Club Manager Club Staff

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    That's not true for LPG injectors, the end part of the injector nozzle is usually removable.

    You are limited by how much the vapouriser can control.
     
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  16. jd1959 Top Contributor ★ ★ ★ ★ ☆

    Ireland Zack Kilkenny
    537
    314
    Unfortunately the exhaust valves can have a shorter life span in many engines. Honda is on that list, the B20B was particularly bad I've been told.

    I run flash lube and do the valve adjustments far more frequently than suggested - around 20,000km and find the exhaust in particular have tightened a good bit every time, usually around .004 or so, the intakes are usually fine. So they are receding more than I'm used to on petrol but it's not like they just fell through the head as soon as the car was on gas. I am hoping that by adjusting the petrol addition side of the mapping to add a few ms to high load areas it will slow down the recession as well. I'll only know in time.

    In saying that if you keep on top of it so they don't get too tight and burn, in my case I've had many miles of use out of the engine. At the moment over 100k km on gas and over 220k km on the engine and it still runs like a clock. The savings on fuel would easily cover the cost of a reconditioned head, gaskets and other bits, labor and timing chain - with several thousand still in my pocket.

    In terms of cooking oil no idea, but from a life time of working in the food production side of the hospitality industry, cooking oils when subject to high heat go sticky - I would be concerned about building up sludge and jelly like residue around the intake port, and the potential effects of running too much un-burnt or partly burnt oil through the cat.

    I found while playing with the pressure in the vaporizer the pressure would get very unstable under a high load if turned up too high. Unfortunately the one I have is barely rated enough for the HP of the engine. A larger vaporizer would solve this but being stingy I sorted the problem out with a combination of larger injector orifice and adding petrol to the map to keep the fuel trims happy at high RPM and loads where the ECU would get upset that the lpg injectors couldn't keep up with demand.

    The calibration nozzles in the injectors are essentially a threaded tube of various internal diameters to restrict flow they just screw into the end of the injectors- smaller pipe less gas.

    -Zack
     
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