| Author | Message | ||
     Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 291 Registered: 8-2007 |
Hello everybody, Fatherhood and this build here ( http://www.16vminiclub.com/forums/showthread.php?t=31851 a 16V Classic Mini block adapted to run a K1200RS head, running close to 150hp on 600Kg...) have kept me away from my Bentley for a while. The car has been used and maintained by Brabo, but now with my big daughter helping me in the garage and the little one born and home, I can start to do some serious work again. my apologies for silence. I plan to correct and improve little niggles during the Christmas holiday, in particular finalise what I started with the boost system several moons ago and eliminate an oil leak (boost related) in the front of the engine. To do all this, I will bite the bullet and dismantle the whole of the front engine, change the front cover gaskets (I am confident that the oil leak comes from there) and improve the crank case ventilation system. I am running a 0.6 bar maximum boost (modified signal), the fact that there is a vacuum leak in the crankcase certainly means that the PCV is not working properly and I am putting boost in the crankcase, hence the leak. QUESTION 1) Is there anybody who can advise on possible sources of vacuum leaks in the front of the engine (other than the foam gasket). My feeling is that the leakage comes from the area between the water pump pulley and the crankshaft pulley. A second smoke test can clarify that... QUESTION 2) The crankcase ventilation system in #52020is not the best... under boost oil vapours from the crankcase are circulated to the front of the turbo, and the intercooler is effectively an oil separator... I plan to use a catch tank between the oil filler intake and the PCV. Anybody against this solution? QUESTION 3) Should the PCV block totally both vacuum sources when flow is reversed? The throttle bodies vacuum source blocs fully when flow is reversed, but the vacuum source from the turbo intake (recirculation valve bell) only holds a very limited amount of back-pressure, and believe it or not, under recirculation there is significant pressure from the recirculation valve body flowing to the PCV... As usual thanks for any input and I hope to be a lot more active... Best regards, Lluís | ||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 119 Registered: 10-2008 |
LLuis, I didnt know a BMW head could be fitted to an A series, are there any articles or books on this conversion as a friend of mine is considering modifications to an MG midget 1275 engine at the moment. Mark | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 292 Registered: 8-2007 |
Hi, He... www.twinkam.co.uk I must say it's a fantastic engine. The head is motorbike with ITB. Noisy noisy. Lluís | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 293 Registered: 8-2007 |
http://twincammini.com/ | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2957 Registered: 4-2003 |
Llu�s,
At all times the crankcase depression is limited to around 15cm H20 by the diaphragm in the breather assembly. This is part number UE70715 and is cheap to replace. The diaphragms are usually split or brittle and hence inoperative. Mechanics usually forget to replace them every 5 years. A brittle diaphragm leads to the loss of crankcase ventilation. The breather chest on Turbo cars has two non-return valves. One is in the manifold-afterplenum path and the other in the feed path sourced from before the turbocharger. These valves ensure that there is always a crankcase depression. The breather valves effectively select the source of greater depression for crankcase ventilation, and at no time should those two sources be under pressure simultaneously. On light throttle, indeed the turbo air return can be under slight pressure as the dump valve is open. Under that condition the one-way valve of that air path in the breather blocks the pressure. At that time the afterplenums are under vacuum so the one-way valve in that path is open. On high throttle settings, the afterplenums are under boost pressure so the one-way valve in that path is closed. The air resistance caused by the air filter causes a depression overcoming any air flow from returned air from the turbocharger at the feed before the turbo so the one-way valve in that path opens. For those clever people who fit low-resistance or washable air filters, beware. This applies especially to naturally-aspirated motors but to turbocharged motors too. In any case, a turbocharger compensates completely for air filter resistance so there is no gain in power output. Fitting a low-resistance air filter can cause oil leaks from the crankcase. On carburettor cars it messes up the fuel-air mixture too, so a visit to a dynotuner with a range of new needles and jets is on the cards if changing the type of air filter on those motors. RT. | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 294 Registered: 8-2007 |
Hi Richard, It's nice to talk to you again. And what do you think about the catch tank? There is a significant amount of oil condensation in the inlet and I think a catch tank would be beneficial. By the way low restriction filters and a Bosch ceramic plate AFM (as in post 1993) is a bloody killer, air restriction would be a detail next to the oil mess from the new filters on the hot ceramic plate... I guess you have changed the sausage foam gasket of the front covers, which is most probably the culprit of my leak. Any advice on how to proceed? Do I need to remove the radiator and grill? Lluís | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 295 Registered: 8-2007 |
Dear all, happy new 2014. I am fearing the worst for by leak. I can actually blow into the crankcase through the PCV and I hear a hissing sound from the crankshaft front oil seal. So I am thinking that it may have popped out. The PCV system is clean and the diaphragm supple, I have ordered one for safety though. What do you think? is it normal that afront oil seal does not hold pressure? Or is the meaning that the crank case is always under vacuum so my hissing sound when blowing in the cralk case is normal? Best regards and thanks for any help. Lluís | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2982 Registered: 4-2003 |
Lluís, If it's any consolation, the front of my Continental R hisses too but does not leak. I did widen the aperture in the breather housing a little to compensate, but the crankcase depression is still a bit low. By contrast, my Turbo R has 15cm H2O depression and does not hiss. The hissing may be caused by the front crankshaft seal, but is more likely caused by the foam strip between the front cover halves, UE5608, leaking. I'll come around to replacing the seal, gasket and foam strip sometime. The job looks and sounds much harder than it really is. The only snag is to have the correct puller to remove the crankcase pulley. RT. | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 296 Registered: 8-2007 |
Hi and thanks, My crankcase depression (at least without boost) is huge, certainly more than 15 cm water column. I ordered a new UE70715 diaphragm from introcar, just to make sure the PCV is working properly, but I have no means to test depression under boost. The system is very nicely engineered but prone to sticky one way valves, as lots of oil ends up there in the PCV valve body. My worry is that by increasing boost (which I plan to to more seriously now that I am done with my Mini) I may have blown the seal due to a faulty PCV. I wonder whether there can be enough clearance made to push the seal back in case it's just a "pop out" issue. PS I am almost certain that my hissing is from the seal, as I have a smoke machine and saw smoke coming from behind the pulley. Ll. | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 297 Registered: 8-2007 |
PS, How did you widen the aperture, there is not much to adjust there? Lluís | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2983 Registered: 4-2003 |
There is a 1cm-or-so welch plug in the breather housing blanking the aperture drilling. Remove that and you will see the aperture between the manifold chamber and the breather. I bored it out a little with a drill, bearing in mind pi-r-squared is the flow parameter, and put a new welch plug back to seal off the affair. So long as the flow does not exceed that offered by the idle speed regulator motor-valve all is fine. It can be easily re-sleeved if you go too far. RT. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2984 Registered: 4-2003 |
ps: increasing the boost will not decrease the ventilation. Rather the reverse, as a high boost provides increased depression after the air filter to ventilate the crankcase.. Provided a suitable air filter element (i.e. a genuine or proper pattern one, not a reuseable or low air-resistance device) is fitted, then the ventilation is highest at low throttle and high boost alike. It is only at intermediate inlet flow demand that ventilation is at its lowest. RT. | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 298 Registered: 8-2007 |
But blow by increases and any fault with the non return valves will have a greater effect... That was my problem I think, despite a rather comprehensive maintenance, my breather was probably not is optimum shape... | ||
| Lluís Gimeno-Fabra Prolific User Username: lluís Post Number: 299 Registered: 8-2007 |
Hi all, Maybe it's too soon to sing victory hymns, but I was amazed to see no drops of oil under my car after a drive this morning... I think the PCV system in turbocars is marvellously engineered but incredibly sensitive to dirt and leaks. Following an old post of Richard, a cleaned the flame trap mesh with thinner and a blow torch. Furthermore I dismantled the housing, cleaning everything meticulously. I applied a very thin layer of sealant to the housing cover. Originally the car had a cardboard gasket, which I did not re-install after damaging it. I think that the control orifice of the diaphragm is not tiny that even minor leaks can knock the system out. Furthermore I applied some sealant around the metal pipe which applies intake vacuum where it enters the PCV valve because I did not trust that o-ring. Finally I tightened all hoses with real hose fasteners and bolted the PCV cleaning the contact surface with the block. I think this last bit is important, because unlike other PCV systems (Jaguar AJ-6, AJ-16) ours is not water heated and with the valve discs it must be very sensitive to condensation. The system is placed above the block on a polished surface because it relies on block heat to avoid condensation, so whilst this might be exaggerated, proper contact is certainly important to avoid non-closing one-way valves. The car went for a drive this morning and amazement, no oil drops. Cross fingers it will stay like this. My dilemma is now: should I add an oil separator or not? It's very easy and it will certainly reduce the inlet contamination. What are your thoughts? Some oil in the intake is however more than good as it lubricates the valves but it just does not look clean enough too me. Maybe I will drive a few hundred highway km's and check. Next week I am in any case changing the oil and going to Brussels and back. Whilst I hope for tightness now, the tightness of my friend's 1996 Continental R is almost total. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2985 Registered: 4-2003 |
Hi Lluis, It all sounds promising. I would pass on an oil separator personally if the system is indeed tight. There was not much wrong with the breathing systems when new, so like so many areas of the car I tend to leave all well alone unless there is a persistent or recurrent premature failure due to design. Give it a good run and enjoy it ! I have just done another 1,000km round trip in my Conti R over the past few days. When they behave they are great. Interesting about the gasket. I was not aware of one, so maybe a mechanic has tried hard to correct the breather in the past. None of the several I have done, including the ones on my Conti R and Turbo R, have one, and I don't see one in the the parts book. RT. |
