how to install lambda on 1998 4.6 hotwire

[pibby]

Hi all,

I have a 1998 discovery v8 petrol efi which has had the 3.9 motor replaced by a 4.6. it is still using the standard 14cux and 5am afm and is dual fuel but I use lpg 99.9% of the time. on my to do list it is to invoke a feedback loop by installing lambda sensors. I am hoping this will improve fuel economy and general engine performance.

I have summised what i believe needs to be done but am hoping someone out there has already been down this path and can confirm/correct me.

What tune resistor? From what I have researched so far about this, the 14cux has about 5 fuel maps in it and the enabled map is determined by the tune resistor under the dash which varied according to the market the vehicle went to. To get the catalyst map the resistor should be 3.9k ohms

What oxygen sensors? Haven’t seen it definitively written but I am guessing the sensors are narrow band and that generic three wire sensors will do. What would happen if wideband sensors are installed – will the ecu keep properly adjusting fuel using the lambda feedback and simply log an error?

Where to install the oxygen sensors? Where the exhaust pipes each side of the vehicle reduce from 2 to one and mounted from the top to avoid condensation issues.

How to install oxygen sensors? From what I’ve read the land rover sensors are 12mm thread whereas most other sensors are 18mm thread. Drill a hole at the appropriate place in the exhaust and weld on the appropriate thread size nut which the sensor will screw on to.

What wiring has to be done? The car has no wiring loom in place for lambda operation. from what I have read there is a wire to heat the sensor which goes from the sensor to the fuel pump relay. There is the signal wire from the sensor which go to pins 23 and 24 (one for each sensor) on the ecu and should be run in a screened wire to minimize any electrical noise. There is an earth from the sensors which goes to the chassis nearby I guess. There is also a screened earth from pins 23 and 24 but I’m really lost here how this is wired in.

Without trying to confuse this any further, I have also read that the appropriate air/fuel ratio for petrol is 14.7:1 and the appropriate air/fuel ratio for lpg is 15.5:1. however, “Lambda is a ratio of ratios and is 1.0 exactly at the stoichiometric point for any given fuel” and at this point will always be 2.5volts. is this just another way of saying that it doesn’t matter what fuel I am driving on ie lpg or petrol, the ecu will be adjusting fuel correctly to aim for lambda 1.0?


Look forward to any help here.

Ps I live in Hobart and spoke to JC who thought philipA had already been down this path.

Thanks,
brett.

[bee utey]

Hi all,

I have a 1998 discovery v8 petrol efi which has had the 3.9 motor replaced by a 4.6. it is still using the standard 14cux and 5am afm and is dual fuel but I use lpg 99.9% of the time. on my to do list it is to invoke a feedback loop by installing lambda sensors. I am hoping this will improve fuel economy and general engine performance.

I have summised what i believe needs to be done but am hoping someone out there has already been down this path and can confirm/correct me.

What tune resistor? From what I have researched so far about this, the 14cux has about 5 fuel maps in it and the enabled map is determined by the tune resistor under the dash which varied according to the market the vehicle went to. To get the catalyst map the resistor should be 3.9k ohms

What oxygen sensors? Haven’t seen it definitively written but I am guessing the sensors are narrow band and that generic three wire sensors will do. What would happen if wideband sensors are installed – will the ecu keep properly adjusting fuel using the lambda feedback and simply log an error?

Where to install the oxygen sensors? Where the exhaust pipes each side of the vehicle reduce from 2 to one and mounted from the top to avoid condensation issues.

How to install oxygen sensors? From what I’ve read the land rover sensors are 12mm thread whereas most other sensors are 18mm thread. Drill a hole at the appropriate place in the exhaust and weld on the appropriate thread size nut which the sensor will screw on to.

What wiring has to be done? The car has no wiring loom in place for lambda operation. from what I have read there is a wire to heat the sensor which goes from the sensor to the fuel pump relay. There is the signal wire from the sensor which go to pins 23 and 24 (one for each sensor) on the ecu and should be run in a screened wire to minimize any electrical noise. There is an earth from the sensors which goes to the chassis nearby I guess. There is also a screened earth from pins 23 and 24 but I’m really lost here how this is wired in.

Without trying to confuse this any further, I have also read that the appropriate air/fuel ratio for petrol is 14.7:1 and the appropriate air/fuel ratio for lpg is 15.5:1. however, “Lambda is a ratio of ratios and is 1.0 exactly at the stoichiometric point for any given fuel” and at this point will always be 2.5volts. is this just another way of saying that it doesn’t matter what fuel I am driving on ie lpg or petrol, the ecu will be adjusting fuel correctly to aim for lambda 1.0?


Look forward to any help here.

Ps I live in Hobart and spoke to JC who thought philipA had already been down this path.

Thanks,
brett.
OK I can help you with fitting an oxygen sensor to the LPG side, that is straight forward and I have done it plenty of times. The petrol side is a complete mystery to me!

The use of wide band sensors requires the ECU to be programmed for it, they can't be read by a simple voltage measurement.

First you will need an oxygen sensor, I use a narrow band heated (3 wire) one as fitted to EA to EL Falcons. You will need a harness plug off such a Falcon, I usually cut one off at a wreckers, easy to get at as it just below the brake booster. Solder and heatshrink a 3 wire harness to the connector long enough to get from the exhaust "Y" junction to the spot for your LPG processor. Drill a 19mm hole and weld a sensor mount to the pipe just after the Y. You will be able to drill across under the transfer case for a reasonably protected position. It is the same thread as old spark plugs, namely 18 x 1.5mm. You could cut a mount off a donor pipe, many cars use this thread.

Fit a LPG processor to suit your system, most use TPS input (0 to 5 volt approx) and oxy sensor (0 to 1 volt) output. The sensor black wire will be green/blue (?) in the harness plug, you must earth the processor to the engine block. The other 2 sensor wires are the heater, they are not polarity sensitive. I connect them to a 12V ignition supply and a suitable earth.

I can't say which processor I recommend unless I know what LPG system you are running.

[350RRC]

PhilipA has done it. Have a look at this thread:

http://www.aulro.com/afvb/technical-chatter/46260-fuel-economy-3-9-o2-sensors.html

You may have to PM him for the details as a PDF. Can't recall seeing it posted.

cheers, DL

[pibby]

hi bee utey - the gas system ecu is one of those sequential vapour injection thingys (elko brand) which is a slave to the 14cux. all the gas ecu does is take the injector opening time (as determined by the 14 cux) and does a calc on that to either increase/decrease or leave the injector opening time as is. that's why i am trying to run the lambda install through the 14 cux as the gas ecu has no lambda function.

thanks for the tip on the falcon sensors and install. never used lambda sensors but read they have a limited life km wise so better off buying new ones? $?

brett.

[bee utey]

hi bee utey - the gas system ecu is one of those sequential vapour injection thingys (elko brand) which is a slave to the 14cux. all the gas ecu does is take the injector opening time (as determined by the 14 cux) and does a calc on that to either increase/decrease or leave the injector opening time as is. that's why i am trying to run the lambda install through the 14 cux as the gas ecu has no lambda function.

thanks for the tip on the falcon sensors and install. never used lambda sensors but read they have a limited life km wise so better off buying new ones? $?

brett.

Gas injection! I should have guessed. Yes, its all up to the petrol ECU so I leave that to the experts.

However you can use an oxygen sensor and a Jaycar kit to read mixtures, then the results of any other method you have of tuning the ECU's output can be seen easily.

Lambda sensors can run for 150 000km happily in a new car, I tried used ones for a while but now I use only new ones. Mainly they respond faster when new, they can get sluggish with age and cause embarrasing lean out just after starting, until they dry out. Never had a problem with new sensors fitted horizontally, I suppose the heater helps.

Suggested part number for the NTK sensor: 0ZA23-D2. Last one cost me $77 trade. It's cheaper than a universal sensor, and being able to unplug it helps installation a lot.:)

I wanted to post this stuff as a thread, when I do another one I might take a few pics.

[PhilipA]

thanks for the tip on the falcon sensors and install. never used lambda sensors but read they have a limited life km wise so better off buying new ones? $?

You cannot use Falcon O2 sensors with a 14CUX.
Falcon sensors are Zirconia sensors and Rover sensors are Titania sensors.
They work completely differently. FYI they are also a different size thread 17MM Zirconia and 12MM Titania.

Zirconia generates a voltage , but Titania changes output voltage from an applied voltage by changing resistance.

Rover uses Titania as they are not susceptable to errors from being immersed etc.
Regards Philip A

[350RRC]

Some more info on closed loop and the 14 CUX:

http://www.aulro.com/afvb/technical-chatter/43421-closed-loop-14cux-rrc-3-9-a.html

Closed loop was standard spec on US vehicles back then, so it's not like inventing the wheel. Should work controlling your injectors.

Will probably look at getting bee utey to update the gas system on my 350 later in the year, sounds like he knows his shiz.

cheers, DL

[bee utey]

You cannot use Falcon O2 sensors with a 14CUX.
Falcon sensors are Zirconia sensors and Rover sensors are Titania sensors.
They work completely differently. FYI they are also a different size thread 17MM Zirconia and 12MM Titania.

Zirconia generates a voltage , but Titania changes output voltage from an applied voltage by changing resistance.

Rover uses Titania as they are not susceptable to errors from being immersed etc.
Regards Philip A
I have met then on a P38A, I know what you mean. Where I fit LPG injection that's fine. When I fit a mixer type LPG system I fit a zirconia sensor to run a LPG processor. I must say that immersion doesn't happen to most of my customers but its something I need to be aware of.

[PhilipA]

For those of you now interested the project write up was posted 26/4/2008 in projects and tutorials.

Its name is "Finally the V8 3.9 O2 project"

Regards Philip A

[PhilipA]

BTW if my interpretation of the tech stuff is correct , if you have a 4.6 running gas injection via interpretation of a 14CUX injector bandwidth, you will have very soft high rev performance.

14CUX has a built in injector duty cycle limit of about AFAIR 75% , enough for say 10-15% extra power but probably not enough to run a 4.6.

This can be altered by fitting a custom chip such as a Tornado which removes the limitation.

There are some other posts about 38A Tornados and Rpi recommend o2 sensors with them.

Also the 5AM Hitachi MAF may limit top end power on a 4.6. This can be changed to a 38A MAF with a bit of fiddling. Again see the Rpi site.
Regards Philip A
PS the new Syntek plug and play ECUs from Brisbane would probably be a similar price and also overcome the problem.

[pibby]

Hi Philip,
A few weeks back I had the lpg ecu mapped and I told the guys who did it to stick the a/f ratio probe in the exhaust and tune only the gas ie don’t worry about how the petrol goes. This immediately gave me a 15% improvement in fuel economy and the car was “lighter on its feet”. Previously, the car felt a bit weak at mid throttle and I put it down to the larger engine sucking more air through the afm at low revs and then it ends up leaning out through the mid range. I can’t really say I was too worried about top end coz I hardly ever go there and the car does weigh over two tonne. I had also read that once you go over 3000 rpm or ¾ throttle the ecu changes where it looks in the fuel map matrix and starts throwing in more fuel without as much finesse. The guy who mapped it said at the low end it was running around 13:1 afr then leaning through the mid range and he was able to sort most of that out with say ½ hour on the road. So I’m not sure if this still means the lpg fuel mapping will be subject to the 14cux duty cycle limit you mention.

Unfortunately my TPS needed replacing shortly afterwards and I’ve since put new springs in the dissy and closed the gap in the dissy as it was too wide. All this means the lpg mapping is a bit off the boil. I am getting the cable and software for the lpg ecu hopefully next week so I shall have a go at redoing the mapping myself. Once the lambda probes are in and the 14cux is in charge of the closed loop I can also use the lpg software to look at the lambda readings whilst driving.

Have looked at your pdf on your installation of lambda and it answers all of my questions. Thanks, very helpful. It would be hard to imagine there’s many new paths left to go down with these older land rovers that haven’t been traversed before.

Once I’ve got the lambda in and things bedded down I am looking at putting in an ecu to replace the 14cux. Though I’ve not written to him yet, I like what extraefi.com has to say about megasquirt especially as he is familiar with land rover motors. He says he was one of the codecutters and wrote the user manuals and is listed on the official site as being a registered supplier of the product. It can run both or one only of ignition and fuel with multiple maps. The ecu with loom etc is around 350 quid and he can put some base maps in for your engine and setup the sensor parameters for landrover sensors to allow you either to get to a dyno or play with it yourself. I’m sure there’s plenty around who can do that and more like syntec you mention. Megasquirt can also accept knock sensor input and JustinC down here showed me just the other day where the mounting points already are on my 4.6. I haven’t looked much further than that with offerings from other replacement ecu manufacturers. This guy at extraefi also has used kits for 95 quid which include coil packs, ht leads, trigger wheel (suitable for land rover), crank sensor etc to allow you to run a wasted spark setup if you so wish. It would also be nice to think I might be able to get rid of the afm and run off MAP which megasquirt lists as being able to do. Anyway, there’s more research to do before I get to the stage of handing over the $.

As an aside, I’ve also got a ‘98 tdi which goes like the day it came off the production line. I drive it around with none of my tools in it – I have 100% confidence it will just go forever and not break down. This 4.6 is a completely different story, I don’t leave home without my tools. I’ve never had an efi engine before and have spent heaps of time just trying to get up to speed on it eg going to the library in town to read the workshop manuals, scanning the internet to find out who’s who in the land rover world and reading what they have to say etc. I would have to say the place that has heaps of spot on info for me is the pistonheads site under the gassing TVR forum. Anyway, after reading forums and especially the aulro site I’m getting the feeling I’m not the only idiot (I speak only for myself here:eek:) with a land rover who might be thinking about their motor during the middle of the night then as soon as the feet hit the ground in the morning go over to the car to see if what you were thinking during the night actually made any sense.

[bee utey]

Once you have your petrol ECU responding to oxygen sensors it will adjust LPG injection times during cruise. Therefore it will be helpful to get the "petrol injector on-time while on gas" (TPonG) to closely match the petrol on time during idle and cruise. This makes the changeover smoother. You will undoubtedly enjoy learning how to drive the software, after 10 installs I am still learning more every time!