Stop/Start engines and turbocharger life 1

[SomptingGuy]

Just wondering...

My turbo gets a good minute or so of idle running after any trip, just because of parking and other natural driving conditions. What about the new breed of stop/start engines. Do they have controls to look after their turbochargers? My commute comprises several places where a banzai stop at traffic lights could mean shutting off rapidly from full load.


- Steve

 

[ivymike]

hmm... interesting question. I know a lot of large turbos that'd be really pissed off by that. Perhaps these little cars have electric oil circulating pumps to benefit the turbos?

 

[patprimmer]

I think with car type turbos with ball bearing and water cooled centres, it's not to much of a problem.

Regards
Pat
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[dgallup]

Some of these are getting electric water pumps which could keep running during the shutdown. Presumably the manufacture will test these extensively but still have to question whether these highly boosted little engines (with or with out start/stop) will last the 250,000 miles that is expected from today's naturally aspirated engines.

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[JayMaechtlen]

how about a small electric motor/pump (with check valves) for the turbo lube oil?
Let it run a few sec prior to startup and 30 sec or more after shutoff.


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[MikeHalloran]

I'd hold off buying a start/stop car until some of these issues are settled in production.



Mike Halloran
Pembroke Pines, FL, USA

 

[SomptingGuy]

My thoughts too. VW (maybe all of VAG?) are advertising stop/start on all vehicles quite heavily at the moment. Must put strain on the starter motor too, unless it's a monster.

- Steve

 

[patprimmer]

I wonder how much fuel is used to recharge after a restart vs used for say 10sec idle. There must be a time equal to break even on average for each engine/starter/temperature/oil grade situation.

That does not consider the environmental impact on starter/generator/battery extra capacity/shorter life.

Regards
Pat
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[SomptingGuy]

Full vehicle simulations are used to quantify energy flows and optimum times to switch things on and off (not just the engine), normally requiring a 42V system to make it viable.

The stop/start thing has quite an effect on fuel economy (CO2 output in political language) and since CO2 is the only thing currently on the political agenda (at least for personal transport), it gets the focus. OEMs want that headline figure (for a new vehicle) to be good.

One thing that I can't quite get my head around though is starter/alternator technology. I used to work (as a student) for Lucas (the "Prince of Darkness"). I never once saw or even heard of any durability testing on these products. We just cut the metal and shipped to the customer, hoping that the tolerances (e.g. number of teeth) were ok.

- Steve

 

[WGJ]

You naughty boy Steve, I can't believe that The Prince was that cavalier about testing and durability...or was he?

One of my last bits of work for a certain manufacturer was an investigation into battery warranty, with a view to how stop/start was going to affect the status quo.
Knowing nothing of the systems was a good place to start.
The existing warranty situation was, in my view, appalling. Partly down to long vehicle storage times off the end-of-line, but partly due to too much development work being done on the assumption of high state of charge batteries. I don't think a realistic enough analysis of customer usage cycles had been done. Ever.
My colleague and I also found that there was a disconnect in terms of the cranking capabilities of modern pre-engaged starters and the cut-off voltages of various OEM ECUs. A 1.6L gasoline system could carry on cranking at voltages so low that the ECU would either shut down or cease to be able to keep relays and driver stages functioning.
So, a customer could key-on and crank, and expect the engine speed to support a start, which would not happen.
Automatic manual transmissions are also a potential cause of problems. I saw one system where, once the battery voltage fell to a certain level, the control system for the gearbox started shuffling actuators about to re-register actuator positions and the consequent 40A(!!) current draw was pulling the battery even lover and, as above, still allowing the engine to crank but with no obvious ECU activity and no start.

I think that, if the vehicle has a belt drive 12v integrated starter/generator, or a flywheel starter generator, start-stop has better prospects than systems based on a beefed up pre-engaged starter system.

This still doesn't get away from the fact that vehicle OEMs want to spend less on stuff like batteries and save weight for emissions and economy, the result (for some OEMs) being a battery with about 18 months lifespan in stop/start+autobox systems.


Bill

 

[drwebb]

Speaking of Prince of Darkness, are these dead or undead batteries zombies or vampires? Perhaps Li-ion will prove a 'silver bullet'?

 

[dgallup]

I worked for Lucas CAV in the early 80's (the diesel division of the Prince of Darkness) and I will say we did a lot of testing. If you were not in the Engineering department you would not have seen much testing. That being said, the electrical systems were designed for the home market, not too hot, not too cold, no long distance driving, etc. They were never redesigned or qualified for ocean shipping, Death Valley highs, Arctic Circle lows or 3000 mile transcontinental trips.

The Powers That Be within Lucas never acknowledged that they had any quality or durability problems, real or perceived. The internal communications were full of rosy little stories about how great the newest widget was, not about all the horror stories in the popular press about smoke leaking out at the most inopportune moments. The company is long gone but the stories will live long after the last Lucas 3 position switch has flickered it's last.

The Prince is dead, long live the Prince!

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[SomptingGuy]

dgallup,

I worked at Acton, Larden Road. Did a spell at SGRD too.

Loads and loads of diesel testing, including regular cells, cold cells and the rest (fantastic experience).

It seems that floor 2, Larden Road did all the design work for the electrical machines and the expansive shop floor next door made them.

I also traversed the country one summer doing industrial noise tests. I saw many test and production facilities, but never one doing electrical equipment durability testing.

- Steve

 

[SomptingGuy]

dgallup,

Out of genuine (kind of anorak) interest, where (what site) did Lucas CAV test their electric machines?


- Steve

 

[dgallup]

I don't know where they did the electrical testing since I was in CAV. Probably in a shed out back or perhaps the pub.

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[SomptingGuy]

"the pub"?

The one on Uxbridge Roag , where it met Larden Road (forget the name of it), that had a "special" menu on Fridays, perhaps?



- Steve

 

[rmw]

This thread has gotten a little silly - back to the OP and Steve's question. I remember some time in the past someone selling some kind of after market bladder accumulator kind of device somewhere about pint or quart size that the oil gallery charged up when running and then it bled down over time after the engine was off providing lubrication to the turbo bearings for the time that it took to bleed down. How about something like that? In theory the oil accumulated in it cooled to the atmospheric temperature at which it was located, so the oil was cooler than engine oil.

I hadn't thought about it much but I've owned and paid the maintenance on heavy duty turck turbo diesels and have driven some as personal transportation. I always baby-ied the turbo in my vehicles by being sure to idle down for a bit especially when coming off the road from a hard pull. I just bought a twin turbo BMW and hadn't even given the turbo(s) a thought, but now I have. Thanks Steve for the OP. Now you got me worried.

rmw

 

[braddles90]

Turbo oil accumulators are pretty much a standard on the engines going underground we work on (~6L Cat engines) - basically because no one underground will leave the machine idling before they turn it off.

http://www.turbosaviour.com.au

It was mentioned in a course I did recently that these accumulators were becoming more prevalent in on-road diesel engines (maybe petrol as well?) - sounds like that isn't the case. Maybe an after-market thing.

 

[patprimmer]

A popular brand with hot rodders was called Accusump. It was from Milodon or Morroso (spelling?) or the like.

Regards
Pat
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[JayMaechtlen]

I think the original purpose and configuration of the Accusump was to store oil at pressure and pre-lube the engine at startup.
It would recharge during run and stay charged for the next startup.
In that config, it would protect the turbo from a dry start, but wouldn't help spindown or cooldown.


Jay Maechtlen

http://www.laserpubs.com/techcomm