What does FSI mean
Discussion
trashbat said:
EGR was really introduced as an eco/emissions measure though, right? I know it came along with early DI engines like the Renault one, but it always seemed to me that it was usually there for compliance - it appeared on later Alfas for this reason. There is a vapour recovery system but I don't know anything about it.
Well pretty much any car since 1995ish (before my time anyway 
) will have tank vapour pipe into inlet and crank breather pipe into inlet. The crank breather is necessary to relieve pressure buildup in the crank due to blowby. not only does blowby contain exhaust type gasses it can also carry oil from the crank case so potentially far worse for carbon build up than EGR.I guess various factors affect whether the fuel vapour purge system has any effect.
Regularly using an engine at the higher end of it's intended operating envelope might well forever fix the problem. Stratified engines tend to only do lean burn at low-load and as I understand lean burn is where the soot happens so if you drive it harder you'll get less soot as well as increased temperature and possibly even more fuel vapour coming through the purge system (purge systems usually don't operate below 40C-50C coolant temp for a start).
scarble said:
I stand corrected. Or educated at least
So do we know for certains that all current production DI engines don't use any kind of breather/EGR filtration to prevent this?
Is it like DPF issues where it will only ever happen if you only take short trips (i.e. does it burn off)?
Well its probably worse with long trips as that's when EGR is used more. Trouble is while EGR is used primarily as an emissions reducer it also improves MPG so it won't go away any time soon.So do we know for certains that all current production DI engines don't use any kind of breather/EGR filtration to prevent this?
Is it like DPF issues where it will only ever happen if you only take short trips (i.e. does it burn off)?
scarble said:
I guess if you use more or less EGR you will get more/less buildup and crank case pressure vs. intake pressure is going to be a big factor so maybe if they had some kind of wibbly crank breather with an oil leak back or something..
That's pretty much the user fix, external catch tank. Except would have to vent to inlet rather than the air.scarble said:
Anyway.. even DI engines do have petrol going over the valves because they all have some kind of vapour purge system which often links in with the crank breather pipes to relieve vapour pressure in the fuel tank but then I guess some cars do this more than others.
Not a significant amount, hardly like an injector blasting petrol at the valve!Incidentally having looked at a 90k port injection motor its very clear where the injector fires as the inlet manifold down to the port in the head is filled with black gunk yet the area opposite the injector and the valve is clean and almost new looking with a distinct line where the spray pattern stops. If I can be bothered to wander down to the garage I'll take a picture later.
scarble said:
and how have diseasels coped all these years? They still have crank breathers right?
Not sure. I'd think not as a very good chance of a runaway.scarble said:
and how have diseasels coped all these years? They still have crank breathers right?
I'd have a guess that they don't burn hot enough to bake the crud onto the valves, as I can't imagine diesel offers much cleaning benefit, even with a port injection system.Also worth pointing out that direct injection still has benefits even whilst not running in stratified/lean burn mode in that compression ratio can be raised due to better knock resistance
Fastdruid said:
scarble said:
and how have diseasels coped all these years? They still have crank breathers right?
Not sure. I'd think not as a very good chance of a runaway.Krikkit said:
Fastdruid said:
scarble said:
and how have diseasels coped all these years? They still have crank breathers right?
Not sure. I'd think not as a very good chance of a runaway.
scarble said:
I.. thought diesels ran hotter..? Or am I being dozy?
They've definitely got lower exhaust gas temperatures, and they take longer to warm up in the winter although that's probably partly down to bigger/heavier/iron engine blocks. And they have better thermodynamic efficiency which would imply lower operating temps.
k all difference to any fuel economy.I had the 3.2fsi on an A6 Quattro auto estate, sorry Avant, and have to say that was pretty damned good economy wise, in winter the 10 mile commute was 1mpg better than the 3.0tdi version of the same car. Maybe Audi diesels are just bad?
I used to average around 27mpg, long runs would see 35mpg sat at 85 and 38mpg sat at 70mpg.
I used to average around 27mpg, long runs would see 35mpg sat at 85 and 38mpg sat at 70mpg.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff