Thread: Sequential gas on a DI V8 ???

PhilipA has a great write up about fitting O2 sensors to the 3.9 V8. Was for a Rangie Classic so the computer etc is in a different spot but the rest should be the same.

It's in this forum somewhere.

You do have to drill holes in the exhaust and weld nuts on as there is no unused mounting spot for them.

This mob do them, at least the drive home will be cheaper

series1

Regards,
David

My P38A has sequential gas injection but no O2 sensors.

Having said that, I have fitted a boss into the exhaust down pipe ready to fit a sensor and I have bought a sensor. I'll fit it real soon now!

I do not know what ECU power is required for sequential injection, but fitting an o2 sensor should be the least of the worries. A Zirconia can be fitted just after where the 2 pipes join with a boss easily obtainable from any exhaust place. It is astounding that a gas fitting place would not know this.
AFAIK, the vapour injection has its own ECU , but tranlates the injector from the car ECU pulse into one which gives the equivalent amount of vapour. Maybe this needs the factory ECU to trim the gas to stoichometric in closed loop.
I suspect the problem is simply that these installers get a kit with instruction on how to fit to say a GEMS 38A or Disco11 or Motronic, but no one makes a kit for a 14CUX. ( maybe because LPG is not popular in the USA, and V8s are very small volume in the UK, and 14CUX cars have probably rusted away by now)
I think its technically solvable but I bet no installers know how to fit up the o2 sensors, as I have described, and it would cost a lot buying them retail etc anyway.
I would be interested to now the outcome of your enquiries.
Another problem of course is finding room for the vapour injectors on the inlet manifold runners under the plenum box.
Regards Philip A

Originally Posted by PhilipA

I think its technically solvable but I bet no installers know how to fit up the o2 sensors, as I have described, and it would cost a lot buying them retail etc anyway.
I would be interested to now the outcome of your enquiries.
Another problem of course is finding room for the vapour injectors on the inlet manifold runners under the plenum box.
Regards Philip A

The O2 sensors are relatively cheap. I got my 4-wire sensor at trade price and it was very cheap - even cheaper if you buy a 2-wire unit. Repco (and probably Bursons) sell the Australian ACA brand.

The sensor is only going to be used for the LPG system, not the GEMS ECU.

My injectors are on the inlet manifold runners under the plenum box.

Mine was intalled by KLR Automotive here in Sydney using the KME system

Range-Rov automotive in Melbourne do the gas injection system too. Give them a call for a second opinion, I know the system has its own ecu.

It would pay to have your radiator checked and recored if necessary.

Radiators tend to clog up over time, and if the one in your vehicle has been there since new, it's quite likely that it may be very marginal. Any thermal load increases (e.g. LPG) will put your cooling system into overload and that is very bad for the 3.9 block.

The block may slip a liner if thermally stressed. This could become a very expensive fix down the track.....

I drive a '99 DII V8 which I had converted to LPG some 7-8 months ago. Just recently, it experienced a slipped liner. Bad news because the block had to go, since it's not possible just to replace a head gasket to stop the coolant loss.

I'm now waiting for my vehicle to come back from the workshop with a fully rebuilt motor. Except that this time, the block will have cylinder liners that are "top hatted", i.e. they will not slip down the bores.


Lawrance Lee
Melbourne, VIC

Replies in record time, cheers,

Thanks for the link Dave, a little far but I might pick their brains anyway, they may even send equipment over here. With regards to the ECU side of things I'm guessing the O2 sensor would be completely seperate to the engines "normal ECU" ( GEMS, Bosch or Lucas?) and would link directly to the LPG ECU as for petrol operation, the engine does not require it.
If I understand PhillipA correctly, the LPG ECU uses the original ECU's signals for firing/timing the injectors but fine tunes the mixture using info from the O2 sensor fitted in the exhaust pipe.
Do most cars with split banks (V8, V6) run a sensor in each downpipe or just the one?
Also Ron, do you have a rough idea on what the O2 sensors are worth (normal price of course, although I know a couple of people that work for Repco...)
As far as the cooling system goes, all is fine. The Disco has a great service history and recently had a cooling system service (hoses, flush, good coolant etc) and I think the radiator is almost new. It shows to, 38 Deg day, air con maxed and it stayed in the bottom quarter of the gauge . I think your right with the advice on the alloy V8 though, I normally flush the Rangie every year for peace of mind, will fit a low coolant alarm to the Disco I think.

Thanks again and I will let you know how it goes - Cheers - Will