am i right in thinking that the 9a puts out 136 bhp and the abf puts out 150bhp? why the big difference,is it down to the heads/cams? and is it true that the abf was originally built to produce around 170 horses? Edited by: riley
6A/9A uses KE jet injection (mechanical constant injection) ABF uses a fully mappable EFI system, ABF also has a hotter inlet cam. In reality there is nothing between them if you use the KR inlet cam in the 6A/9A with the appropriate tweaks to the fuelling. 6A/9A was VW's first attempt at a catalysed 16v and was effectively de-tuned for emissions and strangled by the CAT they fitted. My bored/stroked KR (1984cc) gave the same power and torque as modded ABF's seem to, around 165-170bhp and 150lb/ft on standard K-jet injection. David.
cheers m8,so basically both can produce roughly same power if they have the right cam? which block would be best to 2.1? as in clearance etc would using diesel crank(95.5mm) and 83mm pistons give a true 2.1? cheers again.
I wouldn't bother with the 2.1 route, just keep the standard crank and rebore it if it's worn. The increase in capacity compared to the size of the engine is very small so not worth it IMO. Even a diesel crank only gives an extra 60cc over stock. Joe
If so, how come both 9a/6A and ABF engines use 82.5mm pistons then? The 9A is as bullet proof as anything else, it was used for 8,500 rpm slick 50 championship cars! David.
cheers 4 replies,keep the opinions/advice coming. i havent found a lump yet,but i want to rebuild one from scratch,with everything lightened and balanced,will be a slow process but id like a real animalistic n/a motor for when i rebuild the mk1.
Only difference on the bottom end between the 9A and the ABF is the height of the block and con rods. Both have 82.5mm Bore, 92.8mm Stroke giving 1984cc but the rods in the ABF are 17mm longer. Joe
I thinks it's just a matter of what u can get a hold of and at what cost. In a Mk1, a short block is the best thing really, as the sump on my car (tall block) is quite close to the floor and the suspension is'nt even low. With the ABF you can run digifant, but I'm not sure if that is supposed to be better than K-jet performance wise. Edited by: ViCk
cheers guys gonna be running on carbs or maybe t/bodies. can anyone tell me which model/year diesel crank i need? or am i best off getting it from a tuning company and having it knife edged etc at the same time? cheers vick,are the clearance problems (abf) because of the inlet manifold?
There's a few differences with the cyl. head between the 9a and ABF. There was a really good thread on vortex a while back with comparisons of all the heads and the ABF was noticeably different in the combustion chambers, which apparently aided it in the top end - can't remember why though. If you're going all out and working the head, this won't matter anyway, I guess...
If you are going to tune it, then I believe there are few differences worth mentioning. The ABF weighs more - 16mm more of block (236mm cf. 220mm) and 15mm more rod (159mm cf. 144mm). Sumps will be in same place in both engines I believe - difference is top height of engine. 9a's are getting hard to find. Plenty KR's out there. Probably easy-ish to get an ABF. Get what you can, as best you can, for reasonable price Cheers Rob
a lot of people here seem to assume that the only "benefit" of a 2.1 is the increased capacity. well no. the simple fact is that for any given capacity a longer stroke engine *should* produce more torque - through the simple matter of leverage.
If you're using the car for daily use then don't lighten the crank, they're prone to stalling when lightened, ideal for race.track use though. best to get the whole lot balanced, lighten the flywheel, fit the flywheel & clutch and balance the whole lot.
Lightening the diesel crank will be fine as it is heavier than the original KR. So just by taking the weight down to that of te KR will help benefit without compromising drivability/stalling. Then as said get the whole lot balanced up as one unit.
This is what I used to think also - after all it makes sense - but apparantly its largely irrelevant - the torque is down to the amount of fuel that can be burned completely per cycle - larger cylinder (either by bore or stroke) equals more torque - clever head work and resonance tuning can actually stuff more air/fuel in than the volume of the cylinder and this also helps more torque. If you can do all this at high revs then you have lots of power - a longer stroke is going to give up revving sooner. Big balancing act to match all this to gearing / what the car will be used for etc Rob Edited by: RobT
that will be because although you may have more leverage, you still have to apply a force to that lever - and if the lever is longer then you have to apply the force over a greater distance (and for a greater length of time). you should be able see how this translates to the fuel burn in the cylinder and the revs obtained.
