Whats the deal with the mk2 fuel injection systems?
What are they called? Whats the advantages of each one?
Whats the one you want? What determines which one you get?
:D Alot of questions i know, basically which one is the most reliable/cheep to maintain.
Nick
i hate air leaks....
From my knowledge (correct me if I'm wrong and you're right!):
K-Jet (16V & 8V pre '88) or Digifant II (8V '88 upward)
K-Jet is mechanical, and Digifant is computerised.
I have Digifant and I like it. Only ever had one problem, that was the Idle Stabilising Valve (ISV).
It is not easy to confuse K-Jet with Digifant, the engine compartment in each looks quite different...
Quote from: eight.valve on February 12, 2006, 09:31:51 PM
From my knowledge (correct me if I'm wrong and you're right!):
K-Jet (16V & 8V pre '88) or Digifant II (8V '88 upward)
K-Jet is mechanical, and Digifant is computerised.
I have Digifant and I like it. Only ever had one problem, that was the Idle Stabilising Valve (ISV).
It is not easy to confuse K-Jet with Digifant, the engine compartment in each looks quite different...
So K-jet is the older style more mechanical type system? I asume over time this would be more reliable, less things to go wrong?
Not so sure on that one, someone like Jem would be the one to ask.
I do know that K-Jet is prone to air leaks, (as NasTnaS pointed out) which causes a few problems...
mines done 350 000kms, has air leaks to show, but once it heats up, it goes... and goes well!
Kjet good, unless it leaks air
My Digi Mk2 has done 182,000km, been in the family since about 110. Have only maintained it and swapped the ISV for a spare we had.
My Brothers old Digi Mk2 had done 145,000km and in his ownership the gearbox went, the fuel pump died and the distributor needed replacing otherwise it was good!
I have a digifart in my mk2 Gti.
I havent had too many problems with the injection system, aprt from the broken dipstick causing an air leak and having to clean out the ISV periodically ( why I don't just buy a new one as that would be easier).
I have a digifant mk2. Due to its aggressive ignition map, the Digifant 1.8L has a torque hole at just off idle. This causes the infamous Digifant hesitation. I recently upgraded the ECU and this hesitation is now gone and it gave it a bit more grunt. Yes, vacuum leaks are a problem. I changed my rubber intake boot to an aluminum 3"pipe. I also replaced all the vacuum lines. It is also a good Idea to give the ISV and throttle body a good clean.
Check out this site. It has some good info on Digifant 2.
http://www.members.tripod.com/~fuelie/intro.htm (http://www.members.tripod.com/~fuelie/intro.htm)
GolfGeek, what exactly did you do to your ECU?
Cheers
Quote from: eight.valve on February 13, 2006, 02:36:51 PM
GolfGeek, what exactly did you do to your ECU?
Cheers
I upgraded one of the chips. It only takes about 20 mins to install. I bought it on ebay for US$43 including shipping. This guy is pretty good I got the chip in a week.
Link below:
http://cgi.ebay.com/ebaymotors/VW-Performance-Chip-Volkswagen-Digifant-2_W0QQitemZ8037963065QQcategoryZ33597QQrdZ1QQcmdZViewItem (http://cgi.ebay.com/ebaymotors/VW-Performance-Chip-Volkswagen-Digifant-2_W0QQitemZ8037963065QQcategoryZ33597QQrdZ1QQcmdZViewItem)
Digi was available on the 8V GTI from around 1989 (UK). VW then replaced Digifant with Simos fully sequential injection for the later MK3 8V's (engine code ADY)... but would you believe it, for the ABF super whizzy late 16V MK3, they went for... yup, Digifant. It think Digi is a variant of the Bosch system.
Digifant is fully electronic (i.e., it has a microcontroller), whereas K-Jet is mechanical.
I'm not sure why people assume that things with computers in them are less reliable than purely mechanical items. It's normally the ancillary devices that fail, and again normally due to mechanical wear, or dirt ingress (eg, ISV!!).
I'm a geek.
The electrical systems in the Golfs seem pretty reliable, well in mine anyway.
I honestly thought one day the ECU would have definetly been fried, when jump-starting another car I asked them to attach the leads to their battery thinking that hey were reasonably mechanically minded and would attach them to the proper terminals. I turned the key to their car and nothing happened, tried again and nothing. I get out and check things. There was a stink of plastic. What had happened was, they had attached them leads the wrong way around and they were slowly self destructing. Got a broom handle and whacked the leads off and slwly prpared myself for the idea of replacing the ECU at the least. No such luck, the ECU was fine, along with all the rest of the electrics.
I have seen Japanese cars that seem to crap themselves if you go within 1 ft of putting the leads on the wrong terminals
That is because Germans know what they are doing. And they build robust systems out of industrial standard electronics. Do yourself a favour and open up the ECU box and have a nosy. Well designed! ;D
Quote from: GolfGeek on February 14, 2006, 08:37:49 AM
That is because Germans know what they are doing. And they build robust systems out of industrial standard electronics. Do yourself a favour and open up the ECU box and have a nosy. Well designed! ;D
indeed! Read my post about GPS navigators built in NZ vs those made in China...
Im sure you could fry your ecu on a golf, I think its sparking they dont like so much.
K-jet is good but its old now and not that fuel efficient.
Thanks for pointing out the broken dip stick tube as a air leak i hadnt thought of that.
I think Digifant is a VW version of Bosch L-Jetronic ??
Quote from: orggti on February 14, 2006, 09:34:25 AM
Im sure you could fry your ecu on a golf, I think its sparking they dont like so much.
K-jet is good but its old now and not that fuel efficient.
Thanks for pointing out the broken dip stick tube as a air leak i hadnt thought of that.
Not that fuel efficient compaired to what?
Compared to modern electronic fuel injection and even digifant. K-jet is supposedly more fuel efficient than carbs but then VW did use solex carbs which nobody has ever raved about and my 1.6 gti k-jet uses way more fuel than my girls 1.5 carby model. The problem with K-jet is it runs richer and richer as it wears out, also a problem is its age now, its never been 20 years old before, but now it is. Thats the thing with cars like audis, everyone used to own one and thinks they know what goes wrong but these cars have never been 20 - 30 years old before and nobody knows what goes wrong after that time. Except for everything.
K-jet WAS very good but now COMPARED to new fuel rail systems its old gas guzzling worn out and difficult unless it just works well.
True, but K-jet appears easy to adjust with the correct equipment.
My Digifant Mk2 will do 600-700km to a tank round town driving if you're driving efficiently.
If im being nice the Kjet KR will return around 7.5 to 8.4L per 100km.
Quote from: Neil on February 14, 2006, 09:08:07 PM
True, but K-jet appears easy to adjust with the correct equipment.
Appears easy to adjust with the right equipment? what do you mean?
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted. None of which can be done with modern systems. K jet is great in the fact that it is a 'simple' system.
Well I hadnt heard of you being able to shim the regulator and ive never heard of anybody actually doing this, I dont think this is nessisarily an adjustment but a way to get the correct fuel pressure. I dont think you can shim the pressure up to make it go faster?
And yea you can adjust the mixture by turning a screw that raises or lowers the air flap but once again its just a matter of getting it right if its been knocked or moved or worn slightly.
The System is simple sort of (tho it seems very few acctually really understand it) but you can get some very tricky faults with it and unless you want to replace everything at a cost of about twice what any old K-jet car is worth you can have a hell of a time with it.
How bout i bring you a 90 quattro over thats been giving me some probs and you show me how simple and easy it is to fix and get running right ;D
Ive got a performance book at home that tells you how to set up k-jet's base settings.
If you shim the pressure reg by 2mm you get a pressure increase of 10psi.
Quote from: Neil on February 15, 2006, 09:16:48 AM
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted. None of which can be done with modern systems. K jet is great in the fact that it is a 'simple' system.
Mixture is adjusted automatically by the ecu in new systems even digifant and manual adjustment is not required. The ecu ensures optimal mixture so why do you want to fiddle with it?
Quote from: GolfGeek on February 15, 2006, 02:59:43 PM
Mixture is adjusted automatically by the ecu in new systems even digifant and manual adjustment is not required. The ecu ensures optimal mixture so why do you want to fiddle with it?
Don't forget that Digifant-II as used in Mk2 Golf was open-loop (for non California/US models) and as such had no feedback. Mixture adjustments on that system were just based on mapping of various sensor inputs against VW's known fueling under those particular conditions. Wear couldn't be taken into consideration.
Later models had exhaust sensors (lambda, for those who don't know) which measured the oxygen content in the exhaust and trimmed fuel to suit the engine load conditions. This system could compensate for wear.
Hope that helps!
The Admiral
It helps me admiral not so sure bout the others :)
we could all shim up our K-jet systems and watch our old injectors leak ;D
I suppose my audi 200s computerised dizzy is all pretty much closed loop as you say as well. When did they start to react or open loop?
Quote from: Neil on February 15, 2006, 09:16:48 AM
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted..
It strikes me that that would be a rather broad-stroke method of adjustment - Wouldn't shimming it would adjust the pressure across the board, so it would perhaps improve system pressure in the range where the mixture is a little lean, but potentially would leave it too rich in the part of the rev-range that's already fairly rich? I understood that the variation of mixture with RPM (ie airflow) handled by the shape of the cone in the airflow meter, and thus rather difficult to change.
Please correct me if I'm wrong, because my opinion above is the basis for my link computer retro-fit project, and it would save a whole lot of work...
If you're running K-Jet, and you're a DIY-er, it helps to have something like this:
http://www.mytoolstore.com/toolaid/diagn02.html
Just don't lend it to your 'mates' as I have found to my cost and intense frustration!
Quote from: typ53 on February 15, 2006, 09:09:08 PM
It strikes me that that would be a rather broad-stroke method of adjustment - Wouldn't shimming it would adjust the pressure across the board, so it would perhaps improve system pressure in the range where the mixture is a little lean, but potentially would leave it too rich in the part of the rev-range that's already fairly rich? I understood that the variation of mixture with RPM (ie airflow) handled by the shape of the cone in the airflow meter, and thus rather difficult to change.
Please correct me if I'm wrong, because my opinion above is the basis for my link computer retro-fit project, and it would save a whole lot of work...
Yes your right, its an increase across the rev range.
Why are you changing the ECU? If you look at the metering head and injectors there is nothing electrical there at all. As far as i can tell for Kjet it does nothing with the actual fuel injection, its simply mechanical. The amount of fuel is controlled by the air sensor plate, the further up ward it moves (more air) the more fuel the metering head gives. No ECU input what so ever.
The ECU controls the cold start injector and warm up regulator but thats it, i think. (which is why you never see upgrade chips for Kjet!)
There are two type of 80mm cone, those with a 6.35mm lip and 3.2mm lip, the thick lip cone runs slightly richer than the thin. The European (which our KR's are) fuel distributor has different valving to richen the mixture at high RPM.
Yeah, that's all true to my somewhat limited knowledge. It's been a long time since I've been anywhere near a dyno, but I seem to recall that the mixture was rich down low, a bit lean in the mid-range and rich up at the top end again. I my rather vague memory is correct then I guess shimming would fix the mid-range issue, but what would it do to the performance elsewhere? Plug fouling from low-RPM cruising? Lessor fuel economy I guess, if that's important. Perhaps Jeremy might shed some light here?
I drove a jetta 16v a number of years ago that had an 'inject'? computer system (ie fully electronic injection), with no other mods and it really pulled, especially in the mid-range. Needless to say, i was impressed. Not impressed enough to spend $2k on the computer he was selling at the time, but it left an impression.
I know the conventional wisdom is that K-jet is good for 'x' horsepower, but I'm sure that with other mods like cams the ability to fine-tune fuel flow at various RPM/load settings would produce results. That airflow plate has got to be producing a reasonable pressure drop in the intake system too. I don't know if it's a limiting factor with a standard setup, but the potential is there.
A computerised system also has the advantage of an oxygen sensor and closed-loop mixture adjustment whilst cruising.
Those are all reasons for the change, and I know there are a myriad number of reasons against it too. The truth is: I've had the car 12 years now, I know the car reasonably well and I'm a little bored with the performance of the 16v as standard. I like to tinker and reckon it will be an interesting project. A number of guys on The Vortex seem to be changing to EFI with reasonable results if you believe their posts.
I'm a bit of a skeptic, but reckon it's worth a crack. End of the day, if I'm careful with the implementation of it and it doesn't work well I can always put the k-ket back in and go back to the way it was.
Mind you, it's not going to happen anytime soon: I bought the computer a couple of years ago and so far the loom is only partly installed. Still, the house renovations are nearly finished, so the excuses are starting to run out...
My that turned into rather a long rant. Oops. :-\
Sorry if it's hijacked the thread...
K-jet is all mechanical and adjusting shims is to get the pressure correct only. No benifit at all increasing it.
Some newer K-jet has a basic ecu that alters ignition timinmg only like my 200. The warm up valve at the front of the motor deals with cold running and a thermo sensor activates the cold start injector. Its best to just disconect the cold start injector.
If you have the time and money fitting electronic injectors and a link computer means that finally its worth going to a dyno shop and telling them how you want the car to run, ie flat out at top end or nice and smooth for round town.
K-jet is non adjustable and is now old tecnology and wearing out fast. Also, as is constantly made aware to me, nobody seems to understand it properly. Its completely basic and once worn it runs rich. And yes it is all in the shape of the cone that dictates how much fuel it gives at certain air speeds. They spent a long time getting it right.
What sort of power figure do you want? Or is it the adjustability your after? Kjet with standard injectors will supply enough fuel for 400hp. Although in the US with turbo applications Callaway only used it up to around 230hp. Rossi's Corrado drives very well, thats got a 9A block with cams and standard injection.
I don't really have a power target in mind Neil, to be perfectly honest, it's more the exercise than anything else that's driving this - It's the Engineer in me coming out. It seems worthwhile and I'm curious to see what sort of difference it will make and whether or not I can do it.
It might be an expensive exercise for sure, but hey! everyone's got to have a hobby, right? :)
I have most of the parts that I need now, it's just a matter of finding replacement pins for the VW electrical connectors, someone to make up some fuel lines for me, and emptying my garage so that I can get in and start work. The latter is going to be the big hold up. At the moment I can't get much past the door. :-[
Oh ok. You can buy from VW the electrical terminals if required.
The terminals, without the rest of the plug? Any idea on price?
Yeah ;D depends on which piece you require. You can buy the terminal housing too. There is a whole catalogue on it.
::) Sounds like a long process.
Not really, they split it up into 2pin, 4pin, 6pin connectors and so on.
Quote from: typ53 on February 16, 2006, 09:55:39 AM
And Seriously Rough Paint.
Just outt interest why is the paint rough?
You will have a much improved car with modern electronic injection typ53, good on ya. Apart from being so much smoother and not as on off as k-jet is. Full electronics are so much more flexible to further improvements and mods. And the even better thing is you will get better fuel economy which if this car is a daily driver will pay for the whole thing in about a year or two.
K-jet was great. 20 years ago.
Quote from: orggti on February 16, 2006, 03:42:23 PM
You will have a much improved car with modern electronic injection typ53, good on ya.
Thanks for the encouragement. It sometimes seems a little daunting.
Quote from: HitmanGTI on February 16, 2006, 11:47:56 AM
Just outt interest why is the paint rough?
The best part of a dozen years sitting outside at airports hasn't been kind to the old girl, and the polishing required has worn away the clear coat in a number of places too. That should be changing soon though.
Hey Craig found this on the net
http://www.neutronics.com/bosch.html
Go to pickapart and get some injectors, a ECU and any other bits you might need for bugger all then fit them into a vw manifold and so on. Ask what would be the best car to get this stuff from but i would suggest a 1.6 corrolla AGE motor or a nissan pulsar/sentra 1.6 donk. You could even get the whole loom from the ecu forward.
Quote from: Neil on February 17, 2006, 09:04:37 AM
http://www.neutronics.com/bosch.html
Interesting idea. I guess it works similar to KE-jetronic. I wonder how much they want for their kit with the CAT included, and how tunable it is?
Orggti, thanks for the suggestion on parts, I have pretty much everything I need already (I hope). Sourcing an ECU from a wreck is a good idea, alas I've already shelled out for mine. Now it's down to time available.
The most difficult thing to source appears to be finding a fuel rail that will fit - you can get threaded plastic fuel injector inserts from VAG that will fit the injector holes in the 16v manifold, but you need a long branch off the fuel rail to reach down between the intake runners. Most likely one must be fabricated to fit.
I have a modified Subaru one that fits inside the runners, but I'm not sure yet how it will perform. I'm concerned that it's a little too close to the head and all that heat.
most rails are quite close to the inlet and therefore the head i dont think that should matter. Is the ECU your going to use tuneable thro a laptop? I dont really know to much about how much you can do with the average jap car ECU, maybe you will need to link it all up to a aftermarket one as you will need to adjust it to suit what your car is doing.
It's a Link, probably fairly basic when compared with OEM ECUs, but should do the job. I have a hand controller to tune it with, and there is also the ability to tune it through PC software.
http://www.link-electro.co.nz/home.html
well get into it then.
some help on k-jet...
http://www.auto-solve.com/mech_inj.htm (http://www.auto-solve.com/mech_inj.htm)
Thanks nigel, with that everybody who has K-jet never need ask a question again. Excellent.
Quote from: orggti on February 18, 2006, 04:45:43 PM
Thanks nigel, with that everybody who has K-jet never need ask a question again. Excellent.
Thanks nige you just put jeremy out of a job
Quote from: HitmanGTI on February 19, 2006, 07:29:04 PM
Thanks nige you just put jeremy out of a job
jem doesnt have a job, its more of a passion, passion to hate working on old school GOLFS!
I like working on mk1s its just the mk2s they started to get all silly with. But i dont hate them Nigel.
ok, ok, i was wrong!