Bored out Throttle Body, not just ported and polished...

I've just ebayed a spare Throttle Body for 8.50. Most people port and polish them, but I know that the 8 valve crossflow responds VERY well to a big bore TB.
One of the mods to my friends 150bhp 1800 mk2 with mk4 head (2l 8v), is a VR6 obd1 throttle body, but that required a custom plenum chamber, which I want to avoid.

Has anyone bored one out?
Did you use a custom butterfly? Did you find a bigger one in the VAG parts pin?

Am I barking up the wrong tree, is there a parts bin TB that will bolt on and work?

 

This is the mk2 effort.

 

So you know that a larger throttle body will help? As surprisingly that is not always the case. The larger the diameter, the sloslower the air will pass through it. Air speed is a very important factor. The same as with exhausts, you want the smallest diameter that is big enough (so not restrictive but only just). If you know that is the case then go for it but make sure, it wwould be a lot of hassle if there's no advantage.

 

Yes it definately helps.

 

My mistake tho, it was a 2litre not an 1800.
So anyone know an engineer that Has experience doing the TB work?

 

...and that isn't even the best run. First one was standard manifold. Second run (below) was with a cheapo stainless 4-2-1.

 

What was the baseline test on that engine with stock parts, then with the custom intake manifold with the stock 54mm throttle? Pierburg VR6 throttle is 65mm - the same as an ABF throttle.

back to back like that will indicate what difference the throttle by itself makes.

Of the two tests shown, there is very little change to torque and the 3bhp difference will make almost no difference to drive experience. It does suggest the 4-2-1 ex manifold may point to some high rpm improvement though.

 

The only difference between those two prints is the exhaust manifold, I just posted the wrong pic up first.

I only posted it to show it IS worth tuning an 8v and a much larger TB certainly isn't Detrimental. Because the first thing people keep saying is 'don't bother', which isn't helping.

So, is the ABF an easier swap? Because that could be a more cost effective option.

 

What he said

 

Like I said, it is worth it:
a 65mm vr6 TB + piper285 cam and adjustable pulley, up the compression with adjustable Fuel pressure gets you 150+ bhp,
Add a lightened fly and a DIY head port and polish that's 160+, before you even think about big valve heads.

So does anyone have any useful info about boring out TB's or fitting parts bin alternatives?

 

I've bored out throttle bodies but, there's a limit that can be taken out or you'll be machining into the butterfly bearing. It also needs to be pretty accurate and 'true' to the original bore or the butterfly won't sit properly.
I've not used a std butterfly either on the ones I've done.
It maybe cheaper and easier just to buy a new throttle body depending on application.

 

Yep, that makes sense. So the 54mm is probably only gonna go to 58mm at best Anyway.
I think I'll port and polish the spare 54mm one. Then have a play with a vr6 one, they seem easier to get hold of than ABF ones.

Anyone know what cars other than golf gti's had an ABF engine?

 

So the above engine is heavily modified then?

 

Vehicles with the later 16v single throttle are:

Ibiza (6K) 1.8 16v ADL
Ibiza (6K) 2.0 16v ABF
Passat (3A) 2.0 16v ABF
Cordoba (6K) 2.0 16v ABF
Toledo (1L) 2.0 16v ABF
Golf (1H) 2.0 16v ABF

 

Thanks.

I don't plan to emulate that spec. Just a lightened single flywheel, and later a bigger throttle body and a cam. (Possible port and polish the head) probably adjust fuel pressure, then rolling road it and see where we are at. I don't think I'll break 150 without cc'ing the head And raising the compression. But we'll see what it does do.

 

Is that 1995 on or later?

 

Back in the good old days of Garage Streamline Club work, set ups below and above what describe above, were tested and compared with other configurations on the same day same dyno.

This is what was achieved.



The ABF engine in that exercise, was stock but with a road mapped standalone for maximum response. More torque (peak 160lbft) than any of the 8v motors everywhere
The 2.0 8v was an ex TSR engine, with a road tuned standalone, head work and a Piper 285 cam. Very strong pulling engine I recall. Stock ABF motors in the same shell would have a problem with the 149lbft it could rack up.
The other 2.0 8v was a stock 2E engine with a 272 camshaft running on the OE Digifant. That was later converted to a SEM and achieved 140bhp and 145lbft with tuning.

I got no idea what these numbers mean elsewhere, which is irrelevant if you look at the delta in torque for the changes. G60KGs car pulled harder than most stock fettled KR valvers when the work was complete, especially in the midrange.

 

All looks quite promising.

 

Will the mk3 16v ABF Throttle body fit the mk4 2.0 8v heads inlet manifold...
Yes. Although this is an inlet off an ABA (Canadian import) head, but it looks identical to my uk AQY one.
Just looks like I'll have to 'slot' the bolt holes slightly. However. The TPS plugs don't look compatible, but That'll be simpler to fix than bore-ing out a throttle body.