VR6 2.8 vs 2.9 - stroke or bore???

[___Dubstar___ 0]

Hi,

 

my searches have brought up alot of interesting information but couldnt find a definitive answer. Is the 100cc difference between the golf 2.8 and Corrado 2.9 achieved through stroke or bore?

I have destroyed my 2.9 block and need to find an economic replacement. As the 2.9's seem to be rarer this appears to drive up the price. Could I simply bore out a 2.8 or plonk my crank into a new head?

 

answers on a postcard please.

 

thanks

 

Ian

[tandino 0]

Its bore increase that gives the extra capacity.

Personally my opinion is dont bother with an ABV, in my experience the AAA is a stronger bottom end..

[___Dubstar___ 0]

Thanks tandino (michael?)

Mine is ABV, were all 2.9's? which models were AAA and how are they stronger? Would you reccomend boring them out?

 

thanks

 

Ian

[tandino 0]

Thanks tandino (michael?)

Mine is ABV, were all 2.9's? which models were AAA and how are they stronger? Would you reccomend boring them out?

 

thanks

 

Ian

 

Ian, its Pete :lol:

 

All ABV were 2.9,

AAA were all 2.8 models, they were 81mm bore, ABV were 82.5mm bore.

From my experience ABV are more prone to suffer with ovalised bores and as a result you get varying degree's of smoke after a lengthy overun session when you place your foot back hard on the throttle, ive had 4 ABV's and theyve all done this, my present one is the best in terms of it doesnt use any oil but you will still get a small puff after a long downhill 5th gear overun.

No AAA's ive had have done this and the sweetest VR ive had was a 2.8, it seems that the ABV overbore is less tolerant of abuse in terms of the engine being overheated and the bores due to their thinner walls distort easier compared to the thicker walled 2.8.

As for an overbore, personally dont bother, the capacity increase is something like 69cc difference, the rest of the power was made up by the different inlet manifold, throttle body and the cams are different part number.

I reckon the capacity difference was about 3bhp!!.

Most cost effective way is to buy a cheap complete rusty (plenty of them about!!!) Mk3 Golf VR and take the lump out and sell the rest!!.

 

Hope this helps

 

Cheers Pete

[andy 0]

Most cost effective way is to buy a cheap complete rusty (plenty of them about!!!) Mk3 Golf VR and take the lump out and sell the rest!!.

 

I think I'll be doing that, really good advice all round :) No point faffing with a 2.9 bottom end. I assume everything else from an existing 2.9 can be used including ECU. Just the 2.8 bottom end that is required?

[tandino 0]

Most cost effective way is to buy a cheap complete rusty (plenty of them about!!!) Mk3 Golf VR and take the lump out and sell the rest!!.

 

I think I'll be doing that, really good advice all round :) No point faffing with a 2.9 bottom end. I assume everything else from an existing 2.9 can be used including ECU. Just the 2.8 bottom end that is required?

 

 

Yip,

 

Stick the 2.9 inlet mani and throttle body on from yours and jobs a good un,

Alternatively buy a later OBD2 Golf Vr and kill 2 birds with 1 stone :lol:

[Kevin Bacon 5]

Minor correction (before someone else does it), ABV is 82mm bore. It's the Mahle 2.9 overbore pistons that are 82.5mm (2897cc).

 

Agreed on the ABV, it does seem to be less robust than the AAA. There are a few theories as to why:-

 

1) The ABV had a higher rev limit and was thrashed more since the Corrado was the sports car and the Golf was the more relaxed cruiser

 

2) The Corrado engine bay is more cramped than the MK3, so the motor runs hotter. This can be backed up by the fact MK3 VR6s run at

 

3) Over heating. Both AAA and ABV are completely intolerant of it. Overheating in a past life can easily lead to accelerated bore wear.

 

Plus the fact bores 1 and 6 have much smaller coolant jackets. And maybe the VR6 was designed to be a 2.8 all along in terms of bore thickness etc, so the albeit factory sanctioned 2.9 modifications tipped it over the edge? Although having said that, I've done 50K on my 83mm over bore and it's super sweet and smoke free still :D

 

What you could do for fun is throw an R32 crank in your block for a funky capacity increase. Some shaved or custom pistons will be required but a 3.2 12V will be a rare thing of beauty :D

[Guest]

i love threads like this some worth while info

 

kev seems like youve got your self a little project with that one haha

also i was just having a browse through the difin 24v thread the other day (well the first 9 pages up to now) and i was wondering back in 03 you seemed keen to up grade and well 8 years on youve still not gone r32 or 24v is there a reason for this? other than having vrt :luvlove: :lol:

 

perksy

[___Dubstar___ 0]

lots of information, thanks for that, unfortunately it just leaves me with more questions.

 

in the short term i think i will just buy an old 2.9 VR6 lump and drop it in and run it for now whilst i build a bit of a frankenstein out of the old lump. It had just had the chains and tensioners done when it went bang and was a mint 120k full VWSH one owner from new motor so want to re use as much of the original bits as possible.

 

Alternatively could i just drop in a AAA 2.8 and connect it all up, swap the ECU'S and would that work? Whats this OBD2 stuff?

 

For the rebuild of my old engine could I acquire a AAA 2.8 bottom end/block and use standard 81mm pistons. Put my reskimmed ABV head (been told I will probably need a few valves reseated as well – what the hell does that mean? How is it done? And is it expensive?) on with a R32 crank? Put all the ancillary parts back on, schrick manifold? 268 cams? Do I use my old 2.9 mapped ABV ECU? and “drop” it back in …………… would that work or would it just go bang in a more spectacular way than the last one??

 

and whats the most effective way of running the engine cooler to stop wear? I have read the definitive VR6 cooling guide but it didnt see it mention fitting an oil cooler? Bigger/uprated fans? De clutter the engine bay?

 

thanks again

[dannyboy 0]

OBD2

On Board Diagnostic- generation 2

 

Cars from 1996 had to have it

 

OBD1-car manufactures made there own version of on board diagnostics,their own codes readers could only read.

OBD2-homogenised the on board diagnostics so that nearly any code reader could read any car

 

hope that helps :wave: :wave:

[Kevin Bacon 5]

kev seems like youve got your self a little project with that one haha

also i was just having a browse through the difin 24v thread the other day (well the first 9 pages up to now) and i was wondering back in 03 you seemed keen to up grade and well 8 years on youve still not gone r32 or 24v is there a reason for this? other than having vrt :luvlove: :lol:

 

At that time I think my 12V was standard and I was never particularly bowled over by it's performance. I always wondered where the 190hp was hiding. But after many years of successive mods, I've grown to love it :D I think for me, getting rid of the standard management, shortening the gearing and of course, forced induction, has totally transformed the engine.

 

I do have a 24V engine in my garage though, which has sat there for 18 months or so, waiting for the 12V to let go. My plan was to use the strength of the 2.8 block with an R32 crank and custom pistons to make a super strong 3.0 engine for forced induction, then stick an R32 head on top for good measure, as it has bigger valves and ports..... but the 12V is proving to be a strong old thing and not showing any signs of throwing the towel in :lol:

 

lots of information, thanks for that, unfortunately it just leaves me with more questions.

 

in the short term i think i will just buy an old 2.9 VR6 lump and drop it in and run it for now

 

Yeah that's what I would do tbh, or get a late AAA engine.

 

The other goodies are expensive and need a fair bit of work!