Kjet Vs Digifant

Hi im sure this is an on going debate, but what advantages, differnces there are between the two engines? im looking to get a mk2 gti and just want to know what will be the better engine to go for?

Cheers

 

Aside from whether 16 valves are better than the 8v argument that will go on forever and ever, I think, and anyone please correct me, that the 8v digi is a bit more reliable? I've noticed a lot of threads about 16v k-jet misfire, cutting out, starting, starting when hot, rubbish idle etc but i haven't noticed the same volume of 8v problems.

my 16v k-jet is a proper mare at the moment, but second hand and new parts are quite availiable and have been fairly cheap touch wood.

 

i have a mk2 8v Kjet its an easy engine to work on, very reliable no problems although my car only had 100k on it which is pretty low for an 86, i think its widely agreed that the digi is far easy to tune and get performance parts for. But then again no ECU on the Kjet so i guess less to go wrong???

 

The main advantage of the Digifant is that it can keep lambda in the range 0.98-1.02, where on a mechanical fuel injection system, it ranges 0.8-1.4. This is not so critical for driving the car, but is critical for the longevity of a catalytic converter.

 

i had heard that the 8v engine was the most reliable engine vw have ever made!! duno how much truth there is in that? im guessin it was the digifant?

 

so does the digifant have a cat? and the kjet non cat?

 

Depends on the plate pre 92 neither have cats much like all other cars

 

Kjet cars are nice and simple, but they do tend to come with the age problem, theyre geting on a bit now and parts are getting scarce. The injection system in these cars was first introduced in the 70s, so not exactly cutting edge stuff. But all things aside they are easy to work on and can be kept running with the simplest of tool boxes.

The kjet system in the 16v is the same in the fueling side, exept the wur can be fitted to 8vs, and is also very simple to work on with basic tools. The let down is the electrical side of life, but then again a well maintained car will ave bags of power and go on forever.

The digi system is a vw/bosch adaptation of the bosch motronic injection system. It is the stepping stone in the way towards electronic injection and can pick up many problems becaus of this. It is reliable and robust if maintained, (good earths).

In terms of which is best it does come under personal preference and experience, i ve had them both and would go for the digi system over the kjet simply for more modern and precise running and its an updated, and younger system. Then again i do prefer the kjet 16v but lets not get into that......

 

8olf-blu

The digi is certainly not more reliable!

Look through the engine threads on this forum and of all the VWs covered, about 35% of the posts will be my digi wont start, my digi won't idle, my digi hesitates, my digi is slow, my digi drinks petrol, my digi had a bad earth and blew its ECU, I jump started my didgi and it blew its ECU.....

The GTi reputation was built on the original cars - the Kjets

You seem to be under the impresion that newer is better, unfortunately its not the case. In theory the digi has the potential for better fuel economy but in practice they are all at least fifteen years old and depend upon electrical connections, sensors and earths. How well do you think your computer would work if it had been left out in a damp garage for 15 years now? Well if it actually switched on you would be amazed, even though it kept switching itself off and didn't respond to half the keys on the keyboard! Well a digi is like a computer that has been left in a damp garage for 15 years. The only reason that there are less threads complaining about digis nowadays is that so many are getting scrapped.....

Why do you think VW stuck with Kjet so long on the peformance orientated 16valve where driveabilty and throttle response were essential to the nature of the car?

I once thought I would 'upgrade to digi' twelve years ago when they were still fairly recent. Even at that time Tim Stiles himself advised me against it - and I found out why!

I still own my '86 Mk2 Kjet despite having had a string of progressively more modern and 'advanced' cars over the years, but insane as it might seem I have never found anything else that I wanted to keep apart from 16 valvers and my Kjet Gti Cabriolet although nowadays I'm fortunate thats a summer use only car

Kjets are not foolproof. Put dirty water into them and they will as good as fallover and die but thats usually only a problem with Mk1s and Sciroccos with rusting fuel tanks and filler necks, the robot bulit Mk2s are plastic....

The Gti name and reputation really was built on Kjets. Find the best Kjet you can. Don't make allowances for them being old cars. Find the best that you can, one that still responds better than any more modern car and pulls like a train and you will know you have made the right choice

Valvers are great if you can cope with bit higher fuel consumption and they havn't had an amateur engine rebuild with mistimed camshafts

Good luck

 

I personally prefer the digi in my golfs, true they can be more problematic if they are poorly maintained / setup. but if you get it setup correctly or can do it yourself then they are reliable and problem free.

They are basically the same engine (the head is slightly different in the way the injectors mount) so will respond to all the same mods in the same manner, they make the same power and in my experience are more economical.

the Kjet system is also a simple system that can be used to good effect. its true you don't see to many digi's making there way onto the track. a kjets seem to be more popular but either can be used to make 160bhp+. I have had audi's that use the kjet system. it is an easy system to use and setup.

Basically i would look for a car you like and see what engine it comes with. just make sure its not had a muppet maintain it, if your not that way inclined. ( i once bought a golf that was down on power and didnt run well, the guy had given up on it - did the deal and spent 2 hours checking and setting it up and 6 weeks later it made 116bhp which i thought was pretty good for a high mile digi).

 

Thanks for the advice guys. i Guess i will just have to find a gti i like, and see how it drives, pulls, idles, etc.

I understand what you mean mexicorich about the kjet. A simpler engine, meaning less things to go wrong. But if the digi has an ecu does that mean it can be chipped?? or is this just more problems?

jut wanted to get an overall view of each engine and what people thought. As im completly torn between the two!

Guess im just going to have to find one that feels right!

 

err, well its fairly obvious which one you own then!

have you ever owned a digi, or is this just assumption??

Sorry, its just whenever i've read an 8v VS 16v thread, the people bigging up the valver seem to have only ever owned valvers, whereas the 8v owners seem to have had both and can be a bit more informed about it..... thats my impression anyway, and believe me i've read alot of those threads! I'm beginning to wonder whether the same is true for the K-jet vs Digi argument?

i wouldn't describe owning a digifant car as being the same as owning a 15 year old computer thats been left in a wet garage! Sorry to have a go, but at the start of your thread you say that 35% of the threads on here are digi related problems, and in the same breath you say there aren't as many digi related threads these days because they're all being scrapped! Be honest mate, any golf that would be scrapped, k-jet or digi, would be more likely to be rust/ accident damage/ mot failures, not digi related problems!


I'll try and give this a balanced argument as i have owned 2 k-jet 8v's, 3 k-jet 16v's, and am currently owning my first Digi golf.

They both have their problems, ANY car this age does, but as far as pro's and con's go, i find my current Digi to be more reliable, better MPG etc than any of the k-jets i owned. It starts better, idles way better, and pulls cleaner than my k-jets. And yes, every single one of my k-jets was correctly set up.(after much hair-tearing!)

The upside of k-jet is that it is more responsive, can be tuned easier, and much easier to work on, hence track cars will usually be running k-jet.

The biggest downside of all is that k-jet cars are mapped to run on leaded petrol, and unless you get k-star or some other remapping system, they can run lean in areas of the rev range. I'm not sure how much of an issue this is with the 8v's, but i know with the 16v's they can get around this to a certain extent by carrying out the WUR mod, which prevents it leaning out high up the rev range.

Its true that digi's have more electronics, therefore more to go wrong, but thats true about any advancement in cars. I've had enough trouble out of k-jets in the past to tear my hair out! fuel pressure problems, leaky injectors, unstable idle, you name it. My digi seems ok at the mo, so it may be a one sided argument now, but i'm sure once this one plays up i'll probably change my tune!

follow drunkenalan's advice and find one you like. Of course if you want power steering, big bumpers, etc etc you'll prob have to opt for the Digi.

 

If anything, electronics are more reliable - they're solid state, meaning no moving parts. Anything mechanical will eventually wear out, over time. Of course thats just a theory and K-Jets inner bits wear out very slowly. Also the greater complexity and number of wiring connections is a weak area, corrosion forms on the terminals and causes poor running, strange effects, etc.

 

Digi can be made as-good-as-new, so long as all the sensors and actuators work as new, (and everyone can check them with basic tools and a haynes......)it will perform as new.

The biggest advantage of a Digi tho is that megasquirt is plugandplay. There was a guy on here that fitted megasquit to his digi in a weekend, drove the car straight to the ring, did a sub 10s lap, then drove it home. IIRC he averaged 40+ mpg on that trip too.

There's nothing inherently wrong with K-Jet, it's massively over engineered quality wise But it's still a mechanical system which is non-adjustable and subject to wear. The combination of a well used 16v engine, worn K-Jet, fixed MAP ignition system and a few less than optimal (but well known mod's) will find the weaknesses in the system as a whole V. quickly.

 

Thanks for all your advise, ive taken it all on board and its given me a much better idea of each engine and the benefits of them.

But as im looking to get a big bumper model, with power steering, windows, etc im going to be going one way. My Driver has its own problems so im used to them and didnt mind spending time doing things myself.

Think i just prefer the more modern engine, Sorry to affend kjet fans! dunno if i will be making a mistake, just got to find out.

I asked before but do all digi's have cats?? or is it only '90 spec models??

 

Yes I have had digis to anyone who doubts it? I too thought that new electronics would be progress but then I discovered Tim Stiles really did know his stuff and was right in the advice he gave me sixteen years ago

I have had many cars in that time inculding VR and currently PD TDi but have never parted with my '86 Kjet - its still the best to drive strange as it might sound

Even when digis were brand new they had complaints of poor response compared to Kjets. Repeating myself but VW stuck with Kjet for a reason on 16 valvers and the GTi reputation was built when only the Kjet cars existed

Admittedly my comment about digis all getting scrapped was a bit tongue in cheek......

Yes digis can be chipped and if you read the claims for them you will find that increasing the band of the fuel pulse is claimed to help improve the poor throttle response of digi engines....! But why bother chipping just to try to match the driveability of the genuine article?

And if you are looking for a big bumper car with all the late goodies then yes the Kjet valver is a lovely car :-) even better the day you decide to add a 2-litre bottom end

And if you can find one with aircon, you will have a truly lovely car

 

I dont ever remember hearing that reputation to be doubted until the mk3 came along!

VW built the 16v engine when using Kjet on the 8v, so it would seem that they stuck with a system that they knew worked to good effect.

However the mk3 GTI's didnt come with Kjet and used a electronic system much like the digi, whilst a similar age audi 80 using an ACE engine was still using Kjet and producing much less power than the modern system used on the GTI.

I agree the kjet system is a good system, as is the digifant, i just think that the kjet has mechanical parts that move and wear out gradually causing odd symptoms , at least with the digi system it works or it doesnt and faults IMO are easier to identify and replace, with a little knowledge or forum surfing.

 

The trouble with 16 year old advice is that advice is a product of its time. The change in technology to digifant was probably driven by changing emissions requirements, and the rise of unleaded fuel as much as anything. As enviro-consciousness increases, I wouldn't be surprised if there are more regulation changes in the future (e.g. tighter emissions) which make it ever harder to run a KJet car. I hope not, because I've got 3 of them.

I recently bought a Kjet Rocco Mk2, which is in standard trim, but feels more responsive and perky than my Mk2 Digi that I just got rid of. I'm also averaging over 35 mpg so far, but haven't been thrashing it till I find out where its little quirks and problems are.

The fact is that either system gets less reliable as it gets older, with dodgy sensors, WURs, leaky injectors and Cold Start Valves a problem on Kjets, as opposed to blue temp sender, vacuum lines, FPR's. The reason you see more problems reported on digis is at least partly because there are loads more of them left, with a lot of the early Mk2 8v's having died long ago, wiped out by the big car crime boom in the late 80s and 90s, or just the normal round of old age, rust, accidents, and neglect.

 

Hardly likely. Que the G60 16v in the Golf limited.

CIS-E is controlled by a digital motronic system system and includes o2 feedback and controlls emissions better than raw CIS even has OBD 1 level of monitoring. Digifant 1 and 2 in the USDM also includes O2 feed back. Euro emission stds vs the US were not as strict at that time so the K jet system for VAG was improved rather than junked. (save a bit on developement). The Corrado and Passat, and Audi 2.0 16vs were not as powerful as the revvy 1.8 16v but were much more torquey in the lower to middle rev range as these cars had more weight. The Euro emisson STDs were getting stricter and cats became required hence the trade off to CIS-E. The Golf lost some of its urge with CIS and went to EFI where the torque and power were developed lower and the emissons were less.

Remember the G60 16v. It could have been done if they wanted to. But it was not nesscessary for Europe at the time. ABF Fuel rail can use Nissan SR20/RB25 side feed injectors in place of the 0280 155 *** 205cc units or 1.8T fuel rail if you think you need for fuel for beyond 180bhp.
Digifant MK2s have more features than an older CIS car. Both can run trouble free if you are not to bothered about ulitmate power. But the CIS can be coaxed into being more cripsy quite easily. The lack of TPS does not make the digifant car the smoothest in the world but apart from this they are fine once looked after.
If digifant does not do it for you then with all the sensors on the engine for EFI its a good excuse to throw it into the bin an fit a megasquirt.
I have owned both K jet and Digifant cars.
I miss the response of my old K jet. But I love my P/S, C/L, E/W, E/M and big bumper look of my EFi 91' Mk2.