sequential injection

[crimsonchim]

Hi,

I've been told that a 1994 RV8 (in a range rover) is not "sequential petrol injection".

I'm unsure of this information. On the one hand the guy represents a well known authority on fuelling systems, but on the other he's trying to sell me a non-sequential LPG system.

Surely any injection system with one (or more) injectors per cylinder, has got to be in sequence with the firing order? Or am I misinterpreting "sequential injection"?


Cheers,

Andy

[Mikey G]

Not sure on the RV8 but i'll take Peugeot for instance. Their earlier Bosch Jetronic systems were non sequential and fired all injectors at the same time, later Motronic systems run sequential and so only fire the injector for that cylinder that needs it at the time, both systems have individual injectors for each cylinder.
So just because each cylinder has an injector does not necessarily mean its sequential.

HTH

Mike

[GreenV8S]

As I understand it, pre-serpentine RV8 powered Range Rovers used the same Lucas 14 CUX hotwire system used in TVRs of that era. This system is bank fired, not sequential. When Range Rover went to the serpentine engine they also changed to the GEMS engine management system, which supports sequential injection. The GEMS system is reputedly about as good as you can get for any money. The 14CUX is more primitive but still provides better metering than almost all of the aftermarket systems. What is this new system supposed to give you that the existing one doesn't?

[bor]

I'm pretty sure that a '94 LRV8 will not be sequential. In fact, I'd be surprised if ANY of the LRV8s were ever sequential as it would be difficult to locate a cam sensor.

Anybody ?

[GreenV8S]

Serpentine RV8 production engines are sequential. The cam sensor is built into the serpentine front cover.

[stevieturbo]

The main benefit from sequential injection is for emissions, and I guess fuel economy.. Apparently throttle response is improved too, but whether it is noticeable, is another matter.

It will make no difference to outright power.

[crimsonchim]

GreenV8S said:

As I understand it, pre-serpentine RV8 powered Range Rovers used the same Lucas 14 CUX hotwire system used in TVRs of that era. This system is bank fired, not sequential. When Range Rover went to the serpentine engine they also changed to the GEMS engine management system, which supports sequential injection. The GEMS system is reputedly about as good as you can get for any money. The 14CUX is more primitive but still provides better metering than almost all of the aftermarket systems. What is this new system supposed to give you that the existing one doesn't?

It's a 1994 Classic, looks like the serpentine belt arrangement, but according to the factory manual it uses the 14CUX system. That said the manual shows no representation of a Serp belt arrangement either.

When you say "bank fired" do you mean that 3 out of 4 injectors just squirt fuel against a closed valve?

My question was prompted as I'm looking for a multipoint sequential LPG installation for the RR. Backfires on single point systems scare me and distributed non sequential is almost a expensive as sequential.
One shop (who coincidentally didn't do sequential LPG systems) insisted that "we do not recommend sequential systems for these vehicles" as the petrol engines were not sequential. I sort of assumed that with 8 injectors and engine management, it would be sequential, and I doubted his motives too!

So I thought I'd ask the oracle(s). Kind of expected a yes or no tho!

[GreenV8S]

crimsonchim said:

It's a 1994 Classic, looks like the serpentine belt arrangement, but according to the factory manual it uses the 14CUX system. That said the manual shows no representation of a Serp belt arrangement either. When you say "bank fired" do you mean that 3 out of 4 injectors just squirt fuel against a closed valve? My question was prompted as I'm looking for a multipoint sequential LPG installation for the RR. Backfires on single point systems scare me and distributed non sequential is almost a expensive as sequential. One shop (who coincidentally didn't do sequential LPG systems) insisted that "we do not recommend sequential systems for these vehicles" as the petrol engines were not sequential. I sort of assumed that with 8 injectors and engine management, it would be sequential, and I doubted his motives too! So I thought I'd ask the oracle(s). Kind of expected a yes or no tho!

I don't think you can run a serpentine RV8 on a 14CUX ECU, because the serpentine RV8 uses wasted spark ignition instead of a distributor, and the 14CUX isn't capable of driving it. It is possible that what you have is an intermediate front end (i.e. the sort used on 'serpentine' TVRs, with a poly-V belt but retaining the dizzy). I wasn't aware that this was used on Range Rovers, but that doesn't mean it wasn't!

Yes bank fired means all four injectors on one bank fire at the same time, then the four on the other side fire, and so on. This means that fuel delivery is not synchronised with air being drawn into the cylinders. Intuitively you might think it would be better to run sequential injection so fuel and air go in together, but in fact this isn't as good under power because cold fuel on a hot valve cools the valve nicely and starts the fuel evaporating too. Sequential seems to be better for part load economy and emissions but that is all. Certainly nothing to get excited about for most of us.

[crimsonchim]

GreenV8S said:

I don't think you can run a serpentine RV8 on a 14CUX ECU, because the serpentine RV8 uses wasted spark ignition instead of a distributor, and the 14CUX isn't capable of driving it. It is possible that what you have is an intermediate front end (i.e. the sort used on 'serpentine' TVRs, with a poly-V belt but retaining the dizzy). I wasn't aware that this was used on Range Rovers, but that doesn't mean it wasn't! Yes bank fired means all four injectors on one bank fire at the same time, then the four on the other side fire, and so on. This means that fuel delivery is not synchronised with air being drawn into the cylinders. Intuitively you might think it would be better to run sequential injection so fuel and air go in together, but in fact this isn't as good under power because cold fuel on a hot valve cools the valve nicely and starts the fuel evaporating too. Sequential seems to be better for part load economy and emissions but that is all. Certainly nothing to get excited about for most of us.

Never straight forward is it?

So it's probably a part serpentine with non sequential injection. Learn something new everyday.
At least it doesn't seem to matter much!

I think I'll stick with sequential for LPG though, as the single point means having a plenum chamber full of gas/air mixture with a tendancy to destroy air meters every now and again.

It is a late Classic, first I've seen that has the infamous (on a TVR anyway) stepper motor. Cleaned it once out of interest, but it wasn't dirty!

Thanks for the info guys.

Cheers,

Andy

[bor]

Thanx, Green,

Crimson, you have no choice if your front end is minus the cam sensor and sensor disc. You need a signal telling the ecu when the cylinder is on a firing stroke. Possibly retro-fittable, but probably more trouble than it's worth.