Bit of background first, because what would one of my posts be without a bit of rambling?
Some of you may know that I'm the proud (crazy?) owner of a 1993 Lada Riva. Being a car from 1993 this if course is fitted with a catalytic converter. Nothing too strange there. The strange bit is when you lift the bonnet and discover that Lada decided that rather than develop, buy, copy or steal an injection system, they modified (bodged) their existing carb setup to accept a limited amount of electronic control to work with the cat.
The system uses two solenoids in the carb linked to a custom ECU (referred to in Lada speak as the AFR - air/fuel ratio - module) that lives under the passenger seat to meter fuel, and the peripheral bits of the system consist of a handful of waxstat thermovalves, a couple of switches, the most over-complicated automatic choke mechanism ever invented, and about half a mile of vacuum hoses.
When it's all working properly the system actually works okay. I'm not going to say "well" as they always tend to hunt a bit at idle I've found, but acceptably given the nature of the car. However the whole lot gets thrown out of whack by even the slightest vacuum leak, and even if you know what you're doing trying to adjust things is like herding cats as every adjustment has an effect on about an additional five variables. If you don't know what you're doing I'm just going to say "May the odds be ever in your favour..." and run away in the opposite direction.
My particular example arrived with a third of the vacuum hoses leaking, a third connected to the wrong places and the other third connected only to themselves. Also virtually every adjustment (including those clearly labelled DO NOT ADJUST, or capped with little anti-tamper covers) on my carb had been fiddled with, and the wiring to the carb solenoids had been fiddled with. Quite how the poor thing was running at all to be honest I'm not entirely certain!
I've managed to improve things rather a lot now, so the car actually runs fine under load, and I'm just faced with a poor idle to sort out, though I'm 90% certain that this is now being caused by a sluggish lambda sensor - though the question will remain to be answered of whether it died and caused the system to be hacked about, or was there another as yet undiscovered fault that resulted in the hackery which then killed the lambda sensor? Guess only time will tell!
Now, the later model Lada Nivas (photo below for those of you who don't know it from name - the little four wheel drives that are more than capable of embarrassing many a Land Rover owner) were fitted with a slightly bored out version of the same engine but fitted with an off-the-shelf throttle body injection system. Despite being a very simple (one might even say crude) system, it actually worked very well and has proven to be very reliable.
The crazy idea popped into my head one afternoon of getting hold of the system and grafting it onto my Riva. There are relatively few challenges really involved in this as while it was done at the factory, the injection system on the Niva was very much an add-on. As such the wiring loom is entirely separate to the one for the vehicle itself, and Lada's approach of "why stock three parts when one will do?" means that the vast majority of things will just bolt on. The biggest challenges are finding the crankshaft position pulse (the Niva has a notch in the flywheel for that), but that's easy enough to do with a toothed disc on the crankshaft pulley if necessary, and that I'll probably need to alter the length of the pickup tube for the fuel pump. The whole injection system runs at a relatively safe to handle 30psi as well rather the downright terrifying pressures that many multipoint systems seem to, so pipework isn't too hard to deal with.
I have however been warned off using the Lada system now by several folks in the know on account of several key components now apparently having become very hard to source and that situation only going to get worse as time goes on.
Not to be put off an idea though as the principle still seemed sound I got to thinking...There were a heap of cars in the 90s which used broadly similar monopoint injection systems. They might generally be a bit more heavily integrated into the car than the Lada system, but while that might make a bit more work it shouldn't be insurmountable...So the idea lives on.
The fact that you've got closed loop control via the lambda sensor means that you've got a bit of leeway with regards to an exact match of engine size (especially as I'm not discounting the idea of using an after market ECU at this point if that turns out to be a major headache) provided that there's a bit of wriggle room in the fuelling map. Got a bit of breathing room here as well as we're not going for a performance conversion here where it's necessary to get every possible bhp out of the engine...I'd rather not drop power, but I'm not looking for real world power gains. I know that the 1.7i Niva is actually down on power slightly compared to the carb 1.6, though it does have nearly 25% more torque...If I could have a similar result that would be a real bonus! I've driven both versions of the Niva, and the 1.7i *feels* a heck of a lot more capable due to the extra torque.
Now, back up north I know I'd head down to Persley Den scrap yard and have a rummage for a suitable car, then just get my spanners out and pull the bits I want off then pay for them...Sadly I've not found a scrappy like that down here yet...so I need to do my research first then hunt for parts. I'd rather not end up having to buy a whole car to strip the parts off, but that might yet work out easiest.
So...What do I start looking out for?
First one which sprang to mind was the Mk IV Ford Fiesta. Both the 1.1 and 1.3 versions if I remember rightly ran a Pierburg system which looked very similar to the Lada one. Not sure if the 1.3 version would be able to squeeze enough fuel through to feed a 1.5? Finding one shouldn't be too hard (especially as I don't care what shape the car itself is in!) as goodness knows enough were sold!
I know that a heap of Fiats used monopoint injection systems throughout the 90s. These would likely have the benefit that many bits would actually bolt straight on to the Lada thanks to the common parentage, which could be a bonus as it would save me having to faff around making adaptor plates to attach the throttle body to the inlet manifold etc. However there are two downsides here, firstly that I remember this mainly being used on the smaller engined cars like the Panda and Uno...If memory serves the larger engined Tipo, Tempra etc used a multipoint system didn't they? Also...They're about as hard to find as Ladas these days and I'd feel rotten stripping a good one for parts. Especially the Tempra with the Star Trek dashboard which is a model I confess to always having had a bit of a soft spot for for some reason.
Probably the best candidate that I've come up with so far though is from Vauxhall. If I remember rightly the 1.4 and 1.6 Astras used a monopoint system at some point in the 90s, as did the Corsa B on everything aside from the 1.6 I think. Entirely likely that the same setup was used on the Cavelier. 1.6 Astra setup would be an obvious target as that should work nicely with my 1.5 engine, giving me a bit of breathing room in terms of capacity. The potential headache there is that it's probably a modern enough car that the ECU will be crippled with immobiliser nonsense, plus would probably be looking for a lot of sensor pickups that I wouldn't be looking to implement, so is likely to at best leave the check engine light on forever, if not completely throw its toys out the pram and not work at all. These seem a good candidate though as there are still quite a few about out there and that the engine sizes are a pretty good match. A lot of the bits actually are quite possibly identical to those originally used on the Niva, just lacking the combined Lada & GM logo stamped on them!
I do have a throttle body and injector from a Skoda 135RiC (the injected version of the Rapid), though I haven't got any other bits for it, and those are both incredibly rare (there were six left back when I had mine five or six years ago), and I probably wouldn't want to use anything aside from potentially the injector with an aftermarket ECU as the standard one uses a non-standard lambda sensor which was completely and totally unobtainable back when I had the car - which was one of the reasons I sold the thing back then.
I've no particular wish to muck with the ignition system, by 1993 the Riva had already got a hall effect transistorised ignition system (still using a conventional distributor and rotor arm though) which is actually generally reliable. If I still had points to worry about then yes, I'd probably look to upgrade...as it is though I don't want to add further complexity for the sake of it - plus I've got a heap of spares for the ignition system on the shelf...
The fact that it's a new enough car that it requires the cat to be present and to pass the relevant emissions test to be honest is pretty much the only reason I'm considering something this elaborate (even though it's not that complicated really in the grand scheme of things!), as it means that I can't just throw a Weber DGW32 or similar carb on there and be done with it as it would probably never pass the emissions test. I don't know...it might! ...Lot of money to spend though for a case of "it might be okay." Weber carbs ain't cheap.
This is the point where I open the floor to you folks to see what ideas, tips, comments you might have. Probably the most useful bit of info for me just now though would be additional entries for my list of cars to look at as potential injection system donors.
Thoughts?
