red mk2 'zestorer' thing .. not sure but think i saw that in the c & r yard not long ago so .. if it's mr. crashers car then he still has it
Any ideas why it drank oil? The size of the bore if the pistons fit properly shouldn't matter, or am I missing something...?
A bit... Very big bores on any engine that leave the bore walls thin run the risk of distortion, which breaks the seal of the rings against the bore, which causes blow by, power loss, and when the oil control rings break their seal... high oil consumption. Combine the above with a long stroke crank that increases the rod angle and gives you yet more load on the already weak bore. The longer throw of the crank will no doubt need some clearance grinding inside the block to clear the rods when turning, potentially further weakening the rigidity of the block that already has thin bore walls. Big bores and long strokes are ok to a point, but over do it and you'll take a backward step.
mine is a standerd 2lt 16v mk3 with a powerflow system and piperx induction it got 168.64bhp at awesome rollers the other day, well happy lol
my 2.1 8v used to use a bit of extra oil during it's 1st build run, was told it might have been the semi-synthetic getting past the rings at the time?
There's many reasons for high oil comsumption Mike. Probably not so bad on yours if you dont rev it that high (mid to high 6's ?) but on a high rpm engine (mid 7's and more) with thin bore walls and a very long stroke crank (did'nt that C&R engine have a 99mm crank ?) the bores probably wobble like jelly. There "is" a limit with any given combination, when you cross it, you'll know it. What's gained in capacity is sometimes lost in friction, reduced ring seal, octane reduction due to oil contamination, and the basic cylinder heads inability to supply the bigger lungs etc. It's not (just) a VW thing, it happens to any engine you push past the practical limit.
Point taken regarding the potential distortion when the walls are too thin causing the poor sealing of the rings. Could this be prevented / reduced by using a steel girdle on the bottom of the block to reduce flexing like this? http://www.eurospecsport.com/block-accessories.htm
I would say certainly a good chance of reduction. As for total prevention, difficult to tell really. I have considered one of those myself as my block has suffered the same fate I've seen on a few engines now... cracking of the block in the lower corner next to the gearbox. I'd imagine eurosport have seen the same problem too, hence the girdle. The girdle will help stiffen the lower part of the block, but wont help with distortion of thin bore walls. 83.5mm appears to be ok, though I'd be inclined to look to the side of caution at 83mm when used with a long stroke crank. The 24-25cc difference is'nt going to be worth any extra power to worry about, but the strength in the bores will be.
I would say certainly a good chance of reduction. As for total prevention, difficult to tell really. I have considered one of those myself as my block has suffered the same fate I've seen on a few engines now... cracking of the block in the lower corner next to the gearbox. I'd imagine eurosport have seen the same problem too, hence the girdle. The girdle will help stiffen the lower part of the block, but wont help with distortion of thin bore walls. 83.5mm appears to be ok, though I'd be inclined to look to the side of caution at 83mm when used with a long stroke crank. The 24-25cc difference is'nt going to be worth any extra power to worry about, but the strength in the bores will be.[/QUOTE] Point taken regarding the losses from poor sealing etc. Will the bores distort on boring or during use? My thinking behind taking the bore out as far as possible was to be able to put larger valves in the head and reduce the amount of shrouding around them to improve gas flow. That said, it is a long time since I last had a KR head off and I don't recal the exact dimensions of the valves and their clearance from the fire ring and from themselves internally. I have read that it is not common (to say it mildly) to put larger valves in a KR head. Does this come down to space, 1. inside the combustion chamber, 2. the outer edges of the cylinder 3. the positioning of water / oilways inside the head or 4. cost. I'm very curious to see if anyone has any facts regarding this before I start some trial and error work... Regarding the block, I guess the same applies from old BMW F1 turbo engines, the older and higher mileage the source block the better (less unresolved forces in the metal).
I read a story about the old BMW turbo engines, the BMW motorsport boss used to get the guys to pi$$ on the blocks when they were left outside so they went even more rusty.
Quick google found this http://www.f1technical.net/forum/vi...&start=0&sid=3857b70320c05dfaac02bf8349f9a3c8
i read somewhere that the cnr zestrorer or what ever its called had a 99 mm crankshaft, so that wouldn't help with it drinking oil i'm sure.
as a newbie to this forum i havent read the full 8 pages of this but are we talking wheels or flywheel for the 180bhp? stew
Omega pistons? I was thinking some custom designed forged ones with around a 12:1 cr. Any thoughts on the valves / head info I mentioned earlier in this thread? Thanks guys...
