alchresearch Posted November 12, 2012 Share Posted November 12, 2012 I think this is going to be one of those technologies that is nice now, but a very costly burden for the second hand owner in a few years time, like the diesel particulate filter in diesel engines. Link to comment Share on other sites More sharing options...
PeteMorris Posted November 12, 2012 Author Share Posted November 12, 2012 I think this is going to be one of those technologies that is nice now, but a very costly burden for the second hand owner in a few years time, like the diesel particulate filter in diesel engines. Yes I fear you are almost certainly right. Link to comment Share on other sites More sharing options...
Obelix Posted November 12, 2012 Share Posted November 12, 2012 So you're saying that the 'old' advice was wrong? I hold my hands up, I don't know! I always thought that the problem with oil pressure was more to do with cold starting, rather than when the engine is hot? No the old advice was right. Car engines, or rather bearings have gotten better since then, so that in normal use the increase in bearing wear is still acceptable. However if you are planning on keeping the car a long time this bearing wear is not acceptable, so I don't let mine stop/start. When starting a cold engine, the journals are probably the wrong fit in the bearing, due to differential expansion, and the oil is thick and doesnt lubricate well as it has a low flow rate. Once heated it is better, and gets to the bearings faster on a hot start, but there is always wear on an a hydrodynamic bearing when the shaft starts from a stationary condition. Some figures, which are about 20 years old now showed the problem - something like 90% of all engine wear occured in the first couple of minutes of a running session (the sessions simulated a 30 minutes drive) and of that 90% of wear, 65% of it occured in the first ten seconds before the oil arrived. That's well over half of all total wear occuring in the ten seconds from turning the key. Link to comment Share on other sites More sharing options...
Obelix Posted November 12, 2012 Share Posted November 12, 2012 I think this is going to be one of those technologies that is nice now, but a very costly burden for the second hand owner in a few years time, like the diesel particulate filter in diesel engines. Depends on the DPF - the self regenerating ones seem to be fine. It's the ones that use the additive tank that seem to have issues with gunking up, and they can't easily be cleared by blowtorching them until they submit either.... That and the short run syndrome which seems to make it even worse. If you are going to buy a DPF equipped diesel secondhand get one that's done lots of motorway miles I think.... Link to comment Share on other sites More sharing options...
frededwards Posted November 12, 2012 Share Posted November 12, 2012 It's always been the case that stopping a car from idling will save fuel, even allowing for the restart. However doing this is rather bad for the engine, as almost all engine wear occurs at startup as there is no oil pressure to the bearings. This problem has been alleviated somewhat with better bearing materials but it's still there, and I wouldnt run the risk of constant stop-starting, I'll pay the small amount extra for the fuel costs and save on engine wear myself. You are quite correct. If will also knock hell out of the batteries, leading to an increased cost of ownership and a load of lead and acid that has to be dumped/recycled. But the pious, feta-munching, cheesecloth clad harbingers of eco-cobblers are too busy being outraged at anyone who has the temerity to drive a car to be bothering with this sort of sophisticated, joined-up thinking. I also suspect that the stop-start technology has a lot more to do with marketing that it does with saving a few puffins. Link to comment Share on other sites More sharing options...
PeteMorris Posted November 12, 2012 Author Share Posted November 12, 2012 well, new engines are a lot more efficient. but the biggest change that has allowed this fairly old technology to work is the car batteries. cars with stop start will have a gel battery which is designed to operate the starter motor repeatedly without going flat and wearing out the battery. they also have different starter motors, to handle the hugely increased usage. start stop is inhibited when the engine is too cold, you need air conditioning, or heating, or the electrical load is high, heated seats, windows etc. so, dont do it in your normal car. It says here that: Start-stop systems are heavily reliant on the battery. Testing indicates that AGM batteries diminish in their ability to support start-stop functionality over time. [1]. While alternatives exist (NiZn, Lithium-Ion, Ultracapacitors, PbC), virtually all automakers continue to use conventional AGM lead acid batteries. They 'virtually all' continue to use conventional Lead Acid batteries? or can you have a lead acid gel?...eeeek! Link to comment Share on other sites More sharing options...
truman Posted November 12, 2012 Share Posted November 12, 2012 No the old advice was right. Car engines, or rather bearings have gotten better since then, so that in normal use the increase in bearing wear is still acceptable. However if you are planning on keeping the car a long time this bearing wear is not acceptable, so I don't let mine stop/start. When starting a cold engine, the journals are probably the wrong fit in the bearing, due to differential expansion, and the oil is thick and doesnt lubricate well as it has a low flow rate. Once heated it is better, and gets to the bearings faster on a hot start, but there is always wear on an a hydrodynamic bearing when the shaft starts from a stationary condition. Some figures, which are about 20 years old now showed the problem - something like 90% of all engine wear occured in the first couple of minutes of a running session (the sessions simulated a 30 minutes drive) and of that 90% of wear, 65% of it occured in the first ten seconds before the oil arrived. That's well over half of all total wear occuring in the ten seconds from turning the key. I don't know what difference it makes but my car starts the instant the clutch is depressed..there's no churning...it comes on like a light bulb..it doesn't stop the engine when it's cold..so the oil will always be warm... Link to comment Share on other sites More sharing options...
L00b Posted November 12, 2012 Share Posted November 12, 2012 I think this is going to be one of those technologies that is nice now, but a very costly burden for the second hand owner in a few years time, like the diesel particulate filter in diesel engines.Agreed. I believe they are actually related, as are a number of further 'green' vehicle tech developments.: stop/start is there to reduce emissions as a whole (as measured for official/unofficial figures, particularly 'urban' ones). It's one of these engineering solutions (DPF for diesels, stop/start for all, etc.) for 'needs must' (reduce emissions - not so much marketing as suggested by frededwards, as EU/Gvt legislation ), rather than improving essential vehicle charcteristics (driving/braking/handling/reliability). I have had a really bad experience with DPF. So that's all diesels with DPFs out (as much as legacy tech allows in years to come) so far as I'm concerned. And I wouldn't ever "trust" stop/start completely (i.e. don't trust the car to start again, probably at the most cumbersome possible place - so says Murphy's Law). Tried a Subaru XV the other day, which had it fitted - it was making me feel rather uncomfortable waiting at roundabouts, and eventually really 'doing my head in' after 20 mins! So that's another tech which is out (as much as legacy tech allows in years to come) so far as I'm concerned. Link to comment Share on other sites More sharing options...
Obelix Posted November 12, 2012 Share Posted November 12, 2012 It says here that: They 'virtually all' continue to use conventional Lead Acid batteries? or can you have a lead acid gel?...eeeek! Yup - almost all sealed lead acids are a gelled cell - these are the ones used n wheelchairs, childrens toys like powered buggies, security alarms, emergency ligths etc. The other one you get is an AGM where there is no liquid acid, it's soaked into a mat of fibreglass instead. All these are still lead-acid though, just different ways of making the battery basically. Link to comment Share on other sites More sharing options...
truman Posted November 12, 2012 Share Posted November 12, 2012 Agreed. I believe they are actually related, as are a number of further 'green' vehicle tech developments.: stop/start is there to reduce emissions as a whole (as measured for official/unofficial figures, particularly 'urban' ones). It's one of these engineering solutions (DPF for diesels, stop/start for all, etc.) for 'needs must' (reduce emissions - not so much marketing as suggested by frededwards, as EU/Gvt legislation ), rather than improving essential vehicle charcteristics (driving/braking/handling/reliability). I have had a really bad experience with DPF. So that's all diesels with DPFs out (as much as legacy tech allows in years to come) so far as I'm concerned. And I wouldn't ever "trust" stop/start completely (i.e. don't trust the car to start again, probably at the most cumbersome possible place - so says Murphy's Law). Tried a Subaru XV the other day, which had it fitted - it was making me feel rather uncomfortable waiting at roundabouts, and eventually really 'doing my head in' after 20 mins! So that's another tech which is out (as much as legacy tech allows in years to come) so far as I'm concerned. I've had the car for about a year now and done 34,000 miles..so far the stop start hasn't hiccup'd once..time will tell I suppose.. Link to comment Share on other sites More sharing options...
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