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 Post subject: Jag S Type - O2 Sensors?
PostPosted: Tue Mar 31, 2015 6:53 pm 
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Hi all,

Does anyone know the volts working range of the exhausts 02 sensors on a 2005 3.0 S-Type jag?

Thanks.

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PostPosted: Tue Mar 31, 2015 7:27 pm 
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Some Jags of this era have Denso current-mode wideband sensors, showing no appreciable voltage changes. I do not know if that includes this model, but I expect so.

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PostPosted: Wed Apr 01, 2015 6:11 am 
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So is this why no matter what setting I have them in settings on my software they both reading 3.78 v and don't change at idle and then driving just change from 3.78 to 3.76?

Thanks.

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PostPosted: Wed Apr 01, 2015 11:26 am 
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Like Rosko says, and that does include this model.

Only way to see the current (and hence mixture) is by reading live data from the vehicle OBD port using an OBD reader (or LPG OBD connection); live data will usually give a calculated lambda ratio. Connecting the lambda connection wires from your LPG ECU won't work. In fact, even if you could read current (instead of voltage) it wouldn't help... the current isn't actually produced by the probe itself, it is produced by the petrol ECU to power what amounts to a tiny oxygen pump inside the probe.

Thought you'd got this car all done and calibrated well? Did you monitor fuel trims during calibration? This method is fairly necessary on vehicles with petrol pressure sensors - the petrol ECU compensates for fuel pressure, there will be a difference in fuel pressures between running on petrol (fuel bleed via petrol injectors) and running on LPG (fuel bleed via fuel return). It is easier to calibrate the system properly if petrol pressure while running on LPG isn't too far different from petrol pressure running on petrol. Vehicles with petrol pressure sensors usually render any LPG system's autotune functions even more useless than it would be on a vehicle without petrol pressure sensor.

Simon

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PostPosted: Wed Apr 01, 2015 4:56 pm 
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LPGC wrote:
Like Rosko says, and that does include this model.

Only way to see the current (and hence mixture) is by reading live data from the vehicle OBD port using an OBD reader (or LPG OBD connection); live data will usually give a calculated lambda ratio. Connecting the lambda connection wires from your LPG ECU won't work. In fact, even if you could read current (instead of voltage) it wouldn't help... the current isn't actually produced by the probe itself, it is produced by the petrol ECU to power what amounts to a tiny oxygen pump inside the probe.

Thought you'd got this car all done and calibrated well? Did you monitor fuel trims during calibration? This method is fairly necessary on vehicles with petrol pressure sensors - the petrol ECU compensates for fuel pressure, there will be a difference in fuel pressures between running on petrol (fuel bleed via petrol injectors) and running on LPG (fuel bleed via fuel return). It is easier to calibrate the system properly if petrol pressure while running on LPG isn't too far different from petrol pressure running on petrol. Vehicles with petrol pressure sensors usually render any LPG system's autotune functions even more useless than it would be on a vehicle without petrol pressure sensor.

Simon


Hi Simon,

Thanks for explaining how the 02 sensors work, it's true what they say 'you learn something new everyday'.

And after reading the above and I had the RP come up on the dash due to fuel trims, I thought so too!
So it's time to put my hand up and say 'I don't know what I'm doing'!

So after Easter I will give you a call Simon and arrange coming up to get you to set it up properly.
Will it be a good idea if I buy some new nozzles for the injectors before I come up?
Also should I connect up the wires to the OBD port?

Thanks.

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PostPosted: Wed Apr 01, 2015 8:49 pm 
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Good luck with connecting the wires to the obd port ! What ecu are you using ?


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PostPosted: Wed Apr 01, 2015 9:24 pm 
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Tubbs wrote:
Good luck with connecting the wires to the obd port ! What ecu are you using ?


It's a Europegas Oscar sas obd can ecu.

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PostPosted: Wed Apr 01, 2015 10:36 pm 
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give it a go. Dai should know how successful you will be. Mind I've not seen him about much recently. Or me for that matter ;(


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PostPosted: Thu Apr 02, 2015 12:17 pm 
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Tubbs wrote:
Good luck with connecting the wires to the obd port ! What ecu are you using ?

Ayup Tubbs! :D
I don't think I've ever connected the ECU to OBD on a normally aspirated Jag, can't remember the connection type, Europgas works with 11 different OBD comms protocols so might talk if others don't?

57Jam89 (Jamie rings a bell but I'm not sure if that's your name mate?), No probs if you want to arrange to come in for it setting up, though Tubbs might be closer to you. We'll both have spare MJ nozzles on the shelf for if needed. If you have an OBD scanner that shows live data you may be able to map the system correctly yourself. If you do try, would recommend you first turn off all the LPG autotuning functions, reset any rpm correction and set the system up to get between petrol and zero trims. Since your Jag's Mil light has been on, would recommend you first reset error codes and drive on petrol for a bit with a few engine starts before trying to calibrate the LPG system.. In some cases it can takes some V6 Jags a bit of time to settle down and even attempt to learn idle fuel trims after resetting certain Mil errors.

There are various types of auto-tuning system on different ECUs..
1. The majority of systems start with a basic/default map shape, note Pinj (either at idle or medium low rpm with no load), switch to gas, monitor Pinj again and then pull the whole map up or down by a figure, %, or some function. By doing this a few times they can get Pinj on gas to equal Pinj on petrol under autocal conditions. This can be a useful way of getting a rough idea of what the multiplier should look like with given injectors, nozzle size and pressure but the map will very likely still need a fair bit of tweeking by the installer - That's OK because manufacturers who leave it at step 1 advise that the map will need some tweeking afterwards.
2. After 1, On a multiplier graph, while driving the vehicle some systems plot manifold pressure against Pinj while running on petrol, then do the same while running on LPG - you're supposed to be able to map the system accurately by adjusting the multiplier to get the plotted points to match up.
3. After 2, some systems will automatically make further adjustments in an 'rpm correction' table - by at various rpm/load points momentarily swapping some or all cylinders back to petrol and entering numbers in the rpm table according to any changes in Pinj.

Then there are systems that can do step 2 automatically, some that skip step 2 and go straight to step 3. Some use fancy looking 'wizards' which ask you questions about the vehicle, bhp, extra injection and all sorts of things, they try to do the full setup for you.. Some are decent systems beneath all the gimmickry, some are still gimmciky systems even beneath. But they all still rely very much on the installer getting the basics correct (reducer / pressure / injectors / nozzle placement / piping) and even when this is correct they all still usually do a c**p job of calibration compared to a skilled installer. Nevertheless, many of the 'done in a day' installers rely on these kinds of auto-tuning facilities, and many of them don't even get the basics anything like before leaving the auto-tuning to do it's thing. Those are a few reasons why some of us are kept busy putting right done in a day installs and why some people have lower expecations of LPG compared to petrol..

Nearly all installers are familiar with step 1 (except those that have only fitted certain systems like older AG SGI etc), this 'autocal' can be useful to get a map into the ballpark but these days some of us (myself included) don't even bother with step 1 except on systems that require it like ESGI. After step 1, we're getting beyond what is usually considered autocal and more into what I think of as auto tuning. I find systems tend to get auto tuning wrong and for various reasons.. One of the least techy reasons that applies to all steps is that while the engine is running on petrol the gas temp sensor may be heated or cooled by under bonnet temps but readings are compared as soon as the system switches between fuels.. Even with correct gas temp correction, the gas temp sensor takes time to get to the same temp as the gas flowing past it, so the comparison and changes are made with the system not properly compensating for actual gas temp. Particularly with decent injectors, even if other steps have been done properly, I usually find step 3 has the system automatically entering numbers in the rpm correction table that are more a pointer of delay in gas temp sensor response than making for what would be accurate mapping if a steady throttle was held and gas temps had a chance to reflect actual gas temp. Even if step 3 makes changes that nod in the correct direction, the changes between adjacent boxes are usually 'blocky' so the system would probably give more accurate fueling without such changes.

All above steps fall down when the vehicle's petrol system uses fuel pressure as an input when calculating Pinj, because the fuel pressure will never be quite the same running on gas with a fuel return active as running on petrol with petrol injectors active. Scenario: If the engine idles with Pinj of say 2.7ms at a petrol pressure of 300kpa, then if (when switched to gas and the fuel return bleeds fuel instead of the petrol injectors) the petrol pressure is 270kpa (10% less than the 300kpa), the petrol ECU will increase Pinj by somewhere near 10% to compensate for what it believes is it's fuel system getting the lower pressure... So, the 2.7ms Pinj might give an ideal fuel trim on petrol, but on LPG the same Pinj might give high positive idle fuel trim. Autocal systems nearly always use Pinj as the basis for mapping, but this won't work well on vehicles with a petrol pressure sensor.. We still want Ginj to be a little above Pinj but we're more concerned with fuel trims and accurate fueling on acceleration etc than with matching Pinjs. An LPG OBD connection would probably help keep trims in check, but is too slow to adapt to give great results and won't help much with accurate fueling during acceleration etc. I usually consider OBD connection as just another gimmick and only connect them on a small minority of vehicles, Jag V6s not included. A further complication at idle with low Pinj's can be injector linearity - shouldn't be much of a problem with Mj injectors but with some injectors if a low multiplier is used, a slight change to multiplier can give drastic changes to fueling.. you can think you've got it set up well (maybe with warm gas temps) but when you have other (maybe colder) gas temp readings the calibration can be way out.. particularly if there are delays in readings / temp compensation isn't accurate. The LPG ECU's OBD connection, if you do connect it, won't show you the petrol pressure read - would advise you compare petrol pressure on petrol/on LPG as a first job.

Simon

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PostPosted: Thu Apr 02, 2015 6:45 pm 
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Ay up simon !!
100% agree. They are a right PITA if the fuel pressure is wrong. You can get it definitely close enough. And they do run very well on gas. I generally tune them up on the trims coming back out the scanner. They don't really need the obd connecting. Maybe it's just me. I find them pretty straightforward tuning wise.


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PostPosted: Thu Apr 02, 2015 7:17 pm 
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Hi Simon,

My name is Simon, not Jamie but I can understand why you thought it was because of my username.

After reading your last post Simon it just highlights the fact that I don't know anything about how to set up a system like you boys do!
So I'm not going to touch it any more and then I know I have a free day book one of you up to calibrate it.

Thanks.

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PostPosted: Thu Apr 02, 2015 7:55 pm 
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Have you run a fuel return ?


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PostPosted: Thu Apr 02, 2015 9:21 pm 
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Tubbs wrote:
Have you run a fuel return ?


Yes I fitted a fuel return.
Where are you Based?

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PostPosted: Fri Apr 03, 2015 8:57 am 
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Worcestershire ?


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PostPosted: Fri Apr 03, 2015 7:56 pm 
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Tubbs wrote:
Worcestershire ?


ok, so your about 90 minutes nearer that Simon, so could you set my system up?

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PostPosted: Fri Apr 03, 2015 7:57 pm 
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Tubbs wrote:
Worcestershire ?


ok, so your about 90 minutes nearer that Simon, so could you set my system up?

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PostPosted: Tue Apr 07, 2015 12:19 pm 
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Was anything arranged, private messages etc?

Simon

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PostPosted: Tue Apr 07, 2015 1:42 pm 
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LPGC wrote:
Was anything arranged, private messages etc?

Simon


Hi Simon,

No arrangements and/or private massages done/made.
Still don't know then me and car will be free.

Can't leave it too long cause I noticed a slight misfire under light load then on gas.

Why?

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PostPosted: Sat Apr 11, 2015 5:35 pm 
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57jam89 wrote:
Tubbs wrote:
Worcestershire ?


ok, so your about 90 minutes nearer that Simon, so could you set my system up?


I take it that's a no then?

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PostPosted: Sat Apr 11, 2015 10:46 pm 
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Tubbs mate,

Would swear blind your post at 745 on 2nd April hasn't appeared any other time I've looked at this thread.

Other Simon, have you tried phoning / mailing Tubbs?

Simon

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