Thread: how to install lambda on 1998 4.6 hotwire

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) 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.

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!