Time to do some tuning

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rodstares
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Time to do some tuning

#1 Post by rodstares » Fri May 29, 2020 10:32 pm

Hi guys, I'm back from my work trip and it's time to try and tune my gas set up. I got about 430 km out of a tank of gas which is an improvement of around 100 km, pretty impressive, noticeably more power as well. More power on petrol as well which must be down to removing the old mixer from the air intake. I had trouble with the system switching back to petrol on any sort of hill unless I let it slow right down, not go over about 2100 rpm and the known issue where it switches back to petrol under hard acceleration at about 3000 rpm. It occurred to me that before I start fiddling around with the tune I should ensure the system is getting a good free flowing supply of gas and this system being second hand who knows how old the filters are? So I changed out the liquid filter in the solenoid valve and the gas filter before the injectors. The liquid filter did seem to be somewhat difficult to blow air through. There was a bit of resistance anyway. End result has been that the system is running perfectly apart from the high load switching to petrol above 3000 rpm. So that was a good find. Now I think I am ready to play with the mapping. So... where do I start? I assume I want to tell it to provide more gas at the higher rpm, do I just change the setting at that rev range and see what happens?

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Re: Time to do some tuning

#2 Post by Brian_H » Fri May 29, 2020 11:07 pm

If its switching back due to either low pressure or injector times too long, then changing settings isn't going to fix it, first thing you need to see is what's happening when it switches back, gas times and petrol times, see also what trims are showing if you have access on both fuels under same conditions.

Might be worth posting some screenshots of the current settings up as well.

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Re: Time to do some tuning

#3 Post by rodstares » Sat May 30, 2020 12:51 am

So that would involve hooking the laptop up and someone driving it while observing the display when it switches back? Or is it possible to record and play back the run after? That would be a handy feature.

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Re: Time to do some tuning

#4 Post by Brian_H » Sat May 30, 2020 9:15 am

Don't know your specific ECU, some have better capture features than others. But screenshots of the settings are an easy point to start from if you don't have a second person to assist at this point.

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Re: Time to do some tuning

#5 Post by rodstares » Mon Jun 01, 2020 5:56 am

Cheers Brian,
Here are some shots of the Map and display screens. It is running quite well, not switching back to petrol under any but the very hardest acceleration, uphill second gear from 3500 rpm flat to the boards is the only time it does it. I noticed on the map when revving it hard from idle the green dot will jump way down towards 15ms injector time for a brief moment before recovering and if I hold the RPM at 3500 then give it a sharp kick up to 5000 it will also dive towards that end of the chart. Does this indicate the opening times are likely exceeding 15ms and that will cause the ECU to change back to petrol? When accelerating hard like that the gas pressure also drops from around 1.2 bar to around .95 bar, that could be the problem also? If so that would suggest I need to upgrade my reducer or if I want to keep it for now set the petrol to come on at maybe 3000 rpm and 12ms possibly? I am slowly getting my thick head around how this thing works but it's taking some time.
Map Petrol.jpg
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Map Gas.jpg
Map Gas.jpg (338.64 KiB) Viewed 439 times
Display Petrol.jpg
Display Petrol.jpg (165.13 KiB) Viewed 439 times

rodstares
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Re: Time to do some tuning

#6 Post by rodstares » Mon Jun 01, 2020 5:57 am

and one more, I can only load 3 pics it seems...
Display Gas.jpg
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Gilbertd
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Re: Time to do some tuning

#7 Post by Gilbertd » Mon Jun 01, 2020 8:50 am

No doubt Brian or Simon will give you more detail but the difference between the petrol and gas injector times is too great, gas should be between 1.2 and 1.5x the petrol times, yours are at almost 2x. You either need slightly larger injector nozzles or higher gas pressure.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


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Brian_H
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Re: Time to do some tuning

#8 Post by Brian_H » Mon Jun 01, 2020 9:13 am

It looks to me like your hitting the limits of your reducer - Simon did say it was marginal in terms of flow for your setup in the other post (impossible to connect) assuming this to be the same car?

It does look like the pressure is a bit low, but it also looks like it just isn't very stable at its current setup either going by the variation seen in the above screenshots. Best bet to prove that is to see what pressure its showing when the switchback occours if at all possible. If its still the EMER BAT one your using, then unless you can fiddle any further with the pressure to increase it a bit (your previous posts suggests you pretty much exhausted that possibility) then I'd suspect your stuck looking at a new reducer thats more suited to the install. Simon might have another option if you can hold on for him to answer though first.

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Re: Time to do some tuning

#9 Post by LPGC » Mon Jun 01, 2020 9:25 am

Read this whole post before making any adjustments, I've made a summary at the bottom of the post.

MAP (manifold absolute pressure) reading is showing a constant 0.98 bar even when engine load is low, meaning either you haven't connected the MAP sensor vacuum port to manifold vacuum or the MAP sensor is broken, most likely you haven't connected the MAP sensor to manifold vacuum. Since the pressure reading seems constant (and the pressure reading reads gas pressure minus manifold pressure) it seems you haven't connected vacuum to either the map sensor or to the reducer (if you'd only connected the reducer to manifold vacuum the gas pressure reading would be very low at low loads increasing with engine load until the point was reached that the reducer couldn't flow enough gas to meet demand). Both the pressure sensor and the reducer need to be connected to manifold vacuum.

On a 6 cylinder install you need to make 7 holes in the manifold, one hole for each of the gas inlets (one per cylinder in port runners, which I know you've done) plus one hole into the plenum as a vacuum take-off. The pipe connected to the vacuum take-off splits into 2 (using a vacuum T), one of the vac connections connects to the reducer's vacuum reference, the other connects to the map sensor.

You'll need those vacuum connections to get good results but when you've made the vacuum connections you'll have to re-calibrate. You'll especially need to re-calibrate the low load range of the map, less so the high load range of the map because at high loads there won't be much manifold vacuum anyway. But the shape of your map tells me you've only done autocal (because without the vac pipes connected the correct shape for the map would start with low numbers increasing to high numbers as engine load increases), so you won't have manually adjusted the high load area of the map, so your whole map will be wrong at this point.

Only when the numbers in the map are correct will we know if pressure and nozzles are correct, so first we need to make those vacuum connections...

What reference pressure is set in software (vehicle configuration > changeover > reducer)? This should be set to the actual pressure (low load pressure reading) which at the moment is 1.2 bar so for now set 'reducer' to 1.2. Changing this setting and/or making the vacuum connections will mean calibration has to be re-done. Only when calibration is roughly correct can we know for sure if actual pressure should be re-adjusted (which again would mean having to change the pressure setting and redoing calibration).

We know that the system switches back to petrol when you put your foot down... but at high engine loads if mixture is correct with the current map and if 'pressure' is already set to 1.2 it is likely you'll have to increase pressure and/or nozzle size. I haven't re-capped on all threads/posts about this install (I can't remember the spec of the reducer... is this the Emer/Bat?), if possible on this reducer increase pressure to 1.7 bar and leave nozzle size as it is, then change the 'pressure' setting to 1.7 and re-calibrate.

A positive side effect of increasing actual reducer pressure is that most reducers are capable of flowing a bit more gas at higher pressure than they are at lower pressure but the main reason for increasing pressure in this case is to bring gas injector pulse duration closer to petrol injector pulse duration.

In summary then...

Fit the vacuum connections

Re-calibrate

We know the system switches back to petrol when you boot it but check mixture at high engine load low rpm and note ginj (gas injector duration) versus pinj (petrol injector duration). When you have the vacuum pipes connected up high engine load will be when engine vacuum rises to near atmospheric pressure (near 1 bar, probably shown as near 0.97 bar on your install) when running on gas at around 2000rpm. If the vehicle is automatic there are a couple of ways of getting near full engine load at around 2000rpm, either hold the car still with left foot on the brake pedal while giving it quite a bootfull of throttle (not for long so as not to overheat the gearbox or damage the torque converter etc) or drive at around 60mph and slowly feed in throttle but not to the point the gearbox kicks down. Check mixture under these conditions by reading lambda voltage. Adjust the map until lambda voltage on gas is around 0.7 volts. Compare ginj and pinj again (I expect pinj will be around 16ms and ginj to be higher) - but what readings do you see)?
Adjust gas pressure by around the same percentage difference as the percentage difference between pinj and ginj. So for example if you currently have 1.2 bar gas pressure, pinj of 16ms and ginj of 22ms (ginj is 37% greater than pinj) you'd want to increase gas pressure by 37% to 1.64 bar.

There may yet be problems with the reducer not capable of flowing enough gas for this engine. The above procedures are done during conditions when the reducer is capable of flowing/supplying the engine with enough gas, with the engine running at full load (full manifold pressure) but not producing max power because it isn't revving fast enough. Watch the pressure reading while running these procedures, if pressure falls much below 30% of the software 'pressure' setting then to get good results at higher rpm we'd either need to upgrade the reducer or need to dial in some petrol addition (make the engine run on part LPG, part petrol when you put your foot down).

Simon
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rodstares
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Re: Time to do some tuning

#10 Post by rodstares » Mon Jun 01, 2020 10:32 am

Thanks Simon. The MAP sensor reading .98 is a good pickup, it used to read 1.0 so something has changed. I set it up tee'd off an existing vacuum port, I'll check it in the morning, may be the hose is kinked or blocked or indeed the sensor is buggered. Maybe it needs it's own dedicated port as you say... I don't much fancy pulling that manifold off again :( The reducer is the Emer/bat. I have the reference pressure set at 1.2.
I'll check the vac line and go from there tomorrow.
Cheers gents

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Re: Time to do some tuning

#11 Post by LPGC » Mon Jun 01, 2020 11:27 am

The map sensor usually picks up vacuum signal from a tap in the plenum near the throttle body (vacuum side of throttle body) but you can use an existing vac line, or if there's a mechanical petrol pressure regulator you can T into the vacuum signal for petrol pressure regulator. Different schools of thought on this but with all ideal LPG system components the LPG vac signal would be connected to the petrol pressure regulator vacuum signal, you'd hardly ever go wrong connecting to the petrol pressure reg vac signal if a mechanical petrol reg is present.

The manifold pressure reading is an absolute pressure reading in bar, so 0 (bar) would be an absolute vacuum (an engine manifold will never get to absolute vacuum), would expect to see around 0.3(bar) at engine idle and near 1 bar when the throttle is open regardless of rpm. On a turbo / supercharged engine manifold pressure can get above atmospheric pressure under boost conditions, so with 1 bar of boost the map sensor would read 2 bar (1 bar of artmospheric pressure + 1 bar of boost).

It now reads a constant 0.98 and you've said it used to read 1 - so it seems likely the negligible difference between 0.98 and 1 is just a response quirk (temperature / voltage / etc) and it was never connected properly to vacuum. The pressure and temperature readings are never exactly correct, when the map sensor is open to atmospheric pressure it's reading may change between 0.97 and 1.02 depending on the weather etc (temperature and humidity rather than millibar on a barometer)! Since the sensor can read between 0 bar and around 3 bar it would be too much of a coincidence for it to have broken in a way that sends a constant 1 bar reading, more likely there's a problem with where the vacuum pipe is connected to the plenum or with a broken/disconnected vac pipe.
Last edited by LPGC on Mon Jun 01, 2020 11:33 am, edited 1 time in total.
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rodstares
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Re: Time to do some tuning

#12 Post by rodstares » Mon Jun 01, 2020 11:33 am

Ah ha, I see. It's showing atmospheric pressure when it should show vaccuum, do not right from the start. Awesome, I'll sort that out tomorrow

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Re: Time to do some tuning

#13 Post by LPGC » Mon Jun 01, 2020 11:33 am

That's right mate.

Don't forget that the reducer also needs the vacuum connection. The map sensor and reducer should pick up the vacuum signal from the same place on the plenum, so usually you'd have a vac pipe connected to the plenum with the sensor and reducer both T'd from that single vac pipe.

Also make sure the correct type of Map sensor is selected in software (in 'sensors'). You most likely have the AEB025 type sensor.

Why wait until tomorrow, it's almost mid-day and very sunny isn't it? ;-)
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Gilbertd
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Re: Time to do some tuning

#14 Post by Gilbertd » Mon Jun 01, 2020 11:56 am

LPGC wrote:
Mon Jun 01, 2020 11:33 am
Why wait until tomorrow, it's almost mid-day and very sunny isn't it? ;-)
Not where he is, it's almost the middle of the night......
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

rodstares
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Re: Time to do some tuning

#15 Post by rodstares » Mon Jun 01, 2020 12:03 pm

Ha ha, it's after dinner beer time here. This picture shows the way I have the vacuum lines set up currently
20200601_210301.jpg
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Re: Time to do some tuning

#16 Post by LPGC » Mon Jun 01, 2020 12:24 pm

Looks like it's connected just about directly over the axis of the throttle body shaft, probably a pipe for the evap purge or PCV system, this position probably isn't on the vacuum side of the throttle body and even if it is it will be affected by venturi type effects... No wonder you're not getting a proper vacuum signal! The LPG system vac connection will have to be moved to the plenum.
Gilbertd wrote:
Mon Jun 01, 2020 11:56 am
LPGC wrote:
Mon Jun 01, 2020 11:33 am
Why wait until tomorrow, it's almost mid-day and very sunny isn't it? ;-)
Not where he is, it's almost the middle of the night......
I know :roll: hehe.
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rodstares
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Re: Time to do some tuning

#17 Post by rodstares » Mon Jun 01, 2020 12:38 pm

How about sticking it in this unused port here?
20200601_213647.jpg
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Re: Time to do some tuning

#18 Post by LPGC » Mon Jun 01, 2020 12:46 pm

Yeh that'll do it
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Re: Time to do some tuning

#19 Post by LPGC » Mon Jun 01, 2020 2:26 pm

It is very likely you'll have to increase nozzle size though... As things stand you've got a gas pressure reading of 1.2 bar but that's 1.2 bar above atmospheric pressure not manifold pressure, we'd expect the engine to idle with around 0.3 bar of atmospheric pressure (0.7 bar below atmospheric pressure) so the real pressure difference between gas pressure and manifold pressure will be closer to 1.9 bar. If for correct mixture at idle the gas injectors have to pulse for almost twice as long as petrol injectors to deliver the correct mixture they'll have to pulse for even longer to deliver correct mixture when that 1.9 bar is reduced to 1.2 bar (or to the maximum that the reducer can provide which is probably around 1.6 bar which is still 0.3 bar below the pressure the injectors are currently seeing).

What size nozzles are fitted to your injectors? Most Emer systems use 'Emer 34' injectors which are an equivalent to Valtek type 34 injectors, the nozzles on these injectors unscrew... You should unscrew a nozzle from an injector and measure the approximate size of the hole (jet) through it (try pushing various known size drill bits through it). I expect your nozzles are only around 2mm, expect you'll need to drill all the nozzles to at least 2.5mm.

Nozzle size is critical so don't think 'bigger must be better'... With the components you have (the Bat reducer etc) it would probably be better to have injectors at the small end of the scale for the size of the engine cylinders and increase pressure (the amount the injectors will flow for a given pulse length depends on both the nozzle size and pressure). I expect 2.5mm to be a bit on the small side so might be OK or might still need increasing, the thing is if nozzle size were increased too much (say 3mm - which might normally make for a good install at normal pressure) you'd probably need to keep reducer pressure closer to 1.2 bar or even decrease pressure.
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rodstares
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Re: Time to do some tuning

#20 Post by rodstares » Mon Jun 01, 2020 8:45 pm

LPGC wrote:
Mon Jun 01, 2020 12:46 pm
Yeh that'll do it
Or if you look towards the bottom of the previous picture you can see the mechanical fuel reg, pretty close to the MAP sensor, that might be more convenient.

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