Short blocks, then tall blocks, then short blocks - what was that all about then VW?

There's a thread up at the moment about crossflow blocks and alloy blocks. The point has come up about what height these blocks are. It then prompted a bit of thinking about other blocks, eg the 20v alloy ALT and then this tripped across to the gutless 1.8 iron 20v in the n/a Mk4 GTI. All shortblocks. Ditto the AEB 20v from the Passat / A4.

So the question is why-oh-why have VW gone short block, tall and back to short? 220mm from crank centreline to deck, up to 236mm and back. Rods initially 136mm in the 1600cc EG Mk1 GTI engine, up to 144mm in the 1.8 DX 8v & KR 16v, same with the 6A/9A/ACE and then 159mm in the ABF.

All the arguments about the now-legendary ABF being a taller block for more torque, and less piston sidewall friction + less crank rod angle disappear clean out of the window so fast as soon as the short 20v is mentioned. VW busted by their own backtracking?

Then again, all of the recent dyno work we've seen tends to suggest the ABF is the more favoured motor, more willing to give power, from a non-identical data bank of increasing size so therefore increasingly persuasive evidence, nothwithstanding the 16v 051 casting and ABF cam profile.

Edit: But this isn't another 16v thread. EV to PB 8v Mk2 evolution saw the tall Mk3 8v 2E, AGG & ADY - but what replaced them in the Mk4? (was there a 1.8 Mk4 non-20v?). The crossflow AKL appears to be short.

So what were VW/Audi trying to do? Bring out your tallblock theories!

 

At 159mm VW were using a very long rod in comparison to a lot of other manufactures. But the VW engines were under square in bore to stroke ratio.

Lower slippery bonnet lines for aerodynamics and safety forcing the reduced height of the engine perhaps?

 

Another great thread for the long nights next yr

 

Aye, it'll all be about packaging. Lower bonnet lines, coupe looks, still no RWD. I might have to buy a proper Beetle once the Audi dies.

 

On the packaging angle, the 20v lost the extra height of the 16v up-&-over inlet manifold (easily 7cm-worth), so towards the back of the bonnet, that's not it.

On the 20v inlet inlet behind the grille, I'm thinking of a type approval argument for pedestrian safety (positioning hard objects sufficiently far away from the bonnet underside to allow some impact deflection), but I can't help feeling 16mm of block reduction has nothing to do with it, when they could have reconfigured the inlet further down to compensate if they were so mad keen on the extra block height?

 

They work towards a Lego concept, less parts for more engines ( the same on chassis )
159 mm rods, is pretty long with extra weight
Just kept high blocks for TDI
Engines will become smaller anyway

 

Ah, I guess there's two aspects to this:

1) why did they go tall block in the first place?
2) why did they go short again?

 

1) Better stronger engine / but heavier last forever .

2) Lighter more compact engine / cheaper to manufacture .

thats my theory

 

C'mon! Technical babble on the former pls!

What's stronger about a 2E/AGG/ADY/ABF relative to a 6A/9A/ACE or even AEB?

 

I think the 2.0 8v torque would kill the short block without the better rod angle that the tall block and 159mm rod gives. That is why the 16 and 20v went back to short blocks.

 

2E/AGG/ADY/ABF - main caps are wider /stronger than KR/6A/9A/ACE

 

Ah ha! What but happened with the crossflow 8v block heights?

 

By the time the lardy mk4 Golfs came out, going fast appears to have dropped from the GTI equation. With either 2.0 8v or 1.8 20v NA.

 

White hanky being waved ^^

Good stuff, must have a nosey into the parts dept

But this is more like block evolution, rather than block height theory?

 

Which market would be projected to used used the most engine blocks, market requirements and certification, performance, fuel economy and environment challenges, lessons learnt from older engines etc.

Lessons learnt from "tall" engine, new materials and manufacturing techniques, global environmental challenges, global powertrain sharing, CO2 reduction, engine down sizing, engine technology, 5v/cly, Motronic-Egas, FSI, crash lines.

Those are just some I can think of generally.

 

Rod length ratio (rod length/stroke) -> shorter (lower ratio) is better for drivability.
The shorter rod gives more dwell time at the upper and lower dead points, the speed (travel time) of the piston between upper and lower dead points creates greater suction and also makes valve timing less critical. With a shorter rod the engine will also seem to run smoother.

The longer (1,7:1) rod will produce more horsepower in the upper rev range and a peakier torque curve.
The shorter (1,6:1) rod will produce lower end torque with a flatter curve.

Short and long I mean the ratio's used by VW

159/92,8=1,7:1 ratio
144/86,4=1,6:1 ratio

Doesn't seem much but if you also calculate the saving of material (smaller block, shorter rods) over how many million (???) engines.
Some substantial gaines made I think.

Other than that.... maybe a new manager somewhere within the engine development department????

I once heard a story that the ABF engine was developed to produce 170hp in production state, but was de-tuned to 150hp because it came to close to the 2.8VR6 (174hp) and would have cost sales, my point being... management compared to development.

 

Longer piston dwell time means longer possible time for detonation also.

 

^^Internet rumor first seen on vortex or scirroco 16v. org.
'Tuned' VR6 MK3, stage one emission capable 180PS and 189lbft, 'Tuned' ABF MK3 160PS and 150lbft same level of european emission compliance. So both engines could be tuned using the bog std components and fitted to a new product with warrenties, even though I admit the improvments the VR6 peak engine performance do step in smaller increments, compared to the ABF engine.

 

Has anybody got anymore information of the Oil Injectors sizes on the

2E/AGG/ADY/ABF - Larger Oil Injectors









KR/6A/9A/ACE - Smaller Oil Injectors

pix please !

 

Just to throw this one back in, in case not seen before: