aggri1 wrote:Dude, guess what I just spent a lot of time reading about yesterday! Haha, I now really want to try it (FI that is), because it doesn't sound that complicated really.
Hehehe, I too decided to look at EFI when I got tired of fiddling with carbies which just were not able to do the job. EFI really isn’t all that complex once you have a basic understanding of how an EFI system works
aggri1 wrote:I will start hunting down the stuff I need... including an FI fuel tank, which is the biggest thing yeah?
An EFI fuel tank would be the best and neatest way to install EFI – and you have the advantage of owning a vehicle that came out on the Australian market with EFI fitted from factory (I did my conversion to a Beetle so had to sort out my own tank), so the parts do exist. The other option is to run a separate surge tank, but this will then require mounting somewhere under the vehicle, and the existing fuel tank still has to be modified to accept a return line… Stick with search for a factory EFI tank!
aggri1 wrote:Busses used L-jet didn't they?
As far as I know – perhaps someone else can confirm this for us…?
My EFI system is made up of bits from the good old Holden Camira, but the principal of operation is still the same. My Brother has an EFI Bay window Kombi that he is currently cleaning up after an engine fire (he purchased it in this condition) – he will be rebuilding the EFI system from parts that he has collected over the years and refitting it – perhaps, if I get enough time I can cover this in another post or on my website….
aggri1 wrote:One thing I wasn't clear on was this; in K-jet and L-jet, all injectors squirt simultaneously right (continuously in K-jet!)? (Did I understand that wrong?) But, of course only one cylinder is sucking in air at any given moment, so presumably the squirted fuel just sits behind the inlet valves in the other three, until it's their turns to ingest air.
Yep, yep and yep. Mechanical Injection systems (like the type fitted to the early Porsche, and Audis) squirt continuously, the fuel pressure changes, which (obviously) changes the amount of fuel that is delivered.
Early EFI systems, such as the ones fitted to the Kombis and Type III’s (and most production cars up until the mid-to-late 80’s and even some cheap 90’s cars too) are “Batch fire” systems. They fire all the injectors simultaneously, and the fuel just sits behind the valves until they open. These systems require the injector to be fired 4 times (on a 4 cylinder) for each cylinder to receive the correct amount of fuel (six injector fires for a six cylinder, etc)
Late model EFI systems use a cam angle sensor to tell the ECU which cylinder is about to fire and the ECU will only open the corresponding injector (although rumour has it that this is only the case at low revs). This style of injection is known as “Sequential” injection.
There is much argument about the benefit of sequential injection versus the hassles of installing and wiring a cam angle sensor. Some argue that Sequential is smoother and more economical at low revs, whilst other say that this can only be seen on a Dyno and most people would never notice the difference on the road… the argument still rages…. I personally find that batch injection works just fine for me!
aggri1 wrote:Now I don't know if that's quite how it works, maybe I sound like a dumbass, but I've never had an FI car of any kind - I need to have a look at some FI injectors & manifolds & heads & stuff I think, to see exactly how it should function (I like to know how stuff works, being an unjineer and all). They're not direct injection into the combusion chamber are they?
Are FI TypeIV heads different to carbies ones? I wouldn't have thought so, perhaps with the exception of some drilling for the cyl head temp sensor.
No they don’t inject directly into the head, it all goes into the manifold, just above the intake port (in most cases – as certainly in the case of the factory systems).
There should not be any differences between the heads on an EFI engine and a carb’d engine – as far as I know all the type IV heads have the fitting beside the intake ports for the Temp sensor (referred to as Temp Sensor II in the factory manuals). All the other sensors are mounted on the manifold. I know that some of the twin port Type I heads even had the mounting point for the temp sensor. It would be wise to have a quick look at yours just in case – if it were me, I would have the only set in existence that do not have the temp sensor mounting point!
Good luck with this – it will be a steep learning curve initially, but I can honestly say that it is very unlikely that I will ever own another Carb’d car – EFI is just SOOO much better.
Cheers,
R
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