ABF 2.0 woohoo!

[Simeon]

Running it on K-jet will be fine. Cheapest way to lighten balance a flywheel is through 'hotgolf' on clubgti forum I believe.

Dunno where you're based, but a guy in Leeds called John Langdale is very good at setting up K-jet

[Diamond Hell]

Running it on K-jet will be fine.

Unless you actually rev it, because K-jet tends to lean out at the top of the rev range and adding another 200cc of capacity will antagonise that.

Look for NigeP's Golf Project on CGTI.

See his honeycomb pistons.  Feel his pain.

[fishnchipsx2]

What gearbox are you using?  I'm using an 020 on mine with 210mm mk1 diesel flywheel, which according to my bathroom scales (I know, not the most accurate equipment) weighs just under 5kg - which is already a LOT lighter than an 02A flywheel, which is apparently 9.5kg. 

I doubt there's much difference between pressure plate+clutch assembly weights, which is why I haven't bothered lightening.  Would still be nice tho...

K-Jet ABFs are such a common conversion because it works, and if you already have K-Jet in your mk2, it's easy.  WUR mod is recommended. 

People like Digifant 3.x because it has nice things like knock control, and is supposedly low-maintenance compared to a rusty K-Jet system.

If I were in your situation, I'd bang it in on K-Jet, then get thinking about Megasquirt and ITBs (there's a-whole-nother topic for discussion!)

[Wayne]

DH is spot on, K jet tends to run lean at the top end.

[VeeDubGTI16v]

if you are too stupid to know how to set it up then yes, it will indeed run lean at the top end

[Diamond Hell]

Or if you have a duff batch of fuel.....

Or it's funny weather......

Or if the metering head gets clouted.....

Or if the dizzi moves......

Hell, why not just run a set of carbs and be done with it, eh? 

[Khare]

Swapping Digi for K-jet is a big step backwards. Why don't you want to run Digi?

[Wayne]

Swapping Digi for K-jet is a big step backwards. Why don't you want to run Digi?

Because he never got ecu / loom 

[danny_p]

think i'd prefer carbs to KJet on a toy.

just seen and heard of to meany ABF's that have been running on Kjet all die of the same cause and when you lift the head you see the same thing every time.    and the same pre fail symptoms over and over again.

driver will allways say that "it din't feel as keen as usual."  then the next line is,,,,   "i was comeing down the straight and it just went flat and then i saw blue smoke"

at that point you just know when you lift the head your going to see the top ring on the piston exposed.   to be fair to the motors they take it quite well and often it hasent actualy done to much damage to the bore and with  a quick hone and a new set of rings you can drop anther piston in and it'll go again.   as usual with vw I4 motors it's normaly number 3 that goes first

also the ABF is a bit more vunerable to death by k jet than the 9a or kr.

Kjet was desinged for the 1.8   but the ABF is 2.0   and as it pulls more air it needs more fuel.kjet lovers will say that bolloks because it can supply enough Fuel and the 9A is fine,  this is true but it is working on it's upper limutes.

the exact diffrences in CR between the 9A and ABF have been debated a lot but the genral outcome seems to be that the ABF has a slightly higher compression ratio so the engine will be slight more likely to suffer detonation than a simaler engine with a slightly lower cr running the same spark advance and AFR.

the ABF is a tall block,  meaning it has longer rods 159mm as oposed to 144mm this gives a better rod/stroke  meaning the piston experiances lower rates of accseloration and deceloration as it aproches TDC and BDC for any given RPM and less force thrusting it into the side of the bore.   this also means the pistons stays close for TDC for longer compared to an enigne with shorter rods giveing a larger time window for detonation to occur.

my theory is that this gives the 9A an advantage over the ABF when it comes to K jet.   that is that at a given load and spark advance you can run the 9A leaner before detonation occurs so your more likely to get away with it where and ABF is runnign closer to the line so a less developed gremlin in the fuel system can do quite a lot more damage

rigth there you go i botherd to type out my argument and why... discuss

[fishnchipsx2]

Well if you wanna go into 9A vs ABF territory... 




A fairly recent CGTi thread got me thinking on the rod lengths of 9As and ABFs, so I knocked up a simulation in Matlab to produce these graphs:

In the first three, the blue lines represent a 144 rod and the red lines represent a 159 rod, both with a stroke of 92.8.

   

The displacement is the vertical distance from the top of the rod to the centreline of the crank.  However, I have shifted the curve for the long-rod down the graph by the difference between the 2 rod lengths.  (Sorry if I'm being confusing, but I did it to focus on how long the piston takes to travel over TDC, rather than height of block.)

These next three graphs still have a stroke of 92.8, but rod lengths of 100 (blue) and 300 (red), just to exaggerate (massively) the differences in vertical motion of the piston.

   

So as Danny said, ABF pistons have slower accelerations, and spend more time at TDC.