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ModernAndy

1,114 posts

21 months

[news] 
Monday 8th April 2013 quote quote all
I had to sit down through a class on FSI when I worked for Audi. Would love to run an RS4 on race fuel to see how much of a difference the 'stratification' system actually makes.

ModernAndy

1,114 posts

21 months

[news] 
Monday 8th April 2013 quote quote all
Also, I should add; I think the fuel needs to be sulphur free for FSI to work although having a high RON may be part and parcel with that.

collateral

7,238 posts

104 months

[news] 
Monday 8th April 2013 quote quote all
Can someone smarter than me explain why FSI is so temperamental? Is it just VAG's version which is a problem or all direct injections?

It seems a little odd considering how long we've had direct dervs.

Some Gump

6,062 posts

72 months

[news] 
Monday 8th April 2013 quote quote all
ModernAndy said:
I had to sit down through a class on FSI when I worked for Audi. Would love to run an RS4 on race fuel to see how much of a difference the 'stratification' system actually makes.
I find 98 noticably better than 95. No idea what 105 would do, but that stuff was 1.05 a litre back when 80p was ripping the piss. I'd hate to visit silverstone garage there now!

bearman68

468 posts

18 months

[news] 
Monday 8th April 2013 quote quote all
FSI - stratified fuel injection. The main idea is to inject fuel directly into the piston in the immediate vicinity of the sparkplug. This allows the fuel immediately adjacent to the plug to burn at stoicometric (spelling sorry) volumes, while allowing the remainder of the capacity to be very lean. This results in a very lean combustion. When you accelerate or use lots of power, the injection pattern changes to allow the engine to operate normally. Because the engine runs very lean on cruise conditions, the O2 sensor is a wide band one (tricky to understand if it's working correctly or not), and it usually produces more NOx. I had a 2.0 A4 auto, and that was doing about 41 mpg, which I though very good for the car.
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Ozzie Osmond

16,221 posts

132 months

[news] 
Monday 8th April 2013 quote quote all
Yiliterate said:
I think Mike Brewer sold a car with FSI on the last series of Wheeler Dealers; Full Service 'Istory...
biggrin

scarble

4,390 posts

43 months

[news] 
Tuesday 9th April 2013 quote quote all
Some Gump said:
Are you sure you know what you're on about CJP? I specifically remember seeing a racing documentary where the tech bloke (who runs a VAG car himself) specifically thanks the lord himself for direct port injection....
What?
The only thing DPI can mean is a mix of direct and port (i.e. what CJP said)

So does anyone know of the top of their head if anyone else uses stratified injection? I should know this but.. I don't biggrin


ETA: Hi bearman68, belated welcome wavey
Sounds like you know this subject scratchchin

Edited by scarble on Tuesday 9th April 08:38

cptsideways

10,750 posts

138 months

[news] 
Tuesday 9th April 2013 quote quote all
So it enables lean partial burn?

I thought the early FSI were proper FSI, then Audi realised there were issues & changed the system so it was not stratified but still called it so. This info was from a VAG design engineer who worked in Germany, I'm not sure it was common knowledge.

Edited by cptsideways on Tuesday 9th April 09:03

mackie1

7,284 posts

119 months

[news] 
Tuesday 9th April 2013 quote quote all
My friend who used to work for a well known remapping company informed me that the true lean burn mode was rarely used on NA engines and pretty much never in turbo ones.

Some Gump

6,062 posts

72 months

[news] 
Tuesday 9th April 2013 quote quote all
scarble said:
Some Gump said:
Are you sure you know what you're on about CJP? I specifically remember seeing a racing documentary where the tech bloke (who runs a VAG car himself) specifically thanks the lord himself for direct port injection....
What?
The only thing DPI can mean is a mix of direct and port (i.e. what CJP said)

Sounds like you know this subject scratchchin
http://youtu.be/0116mkt7-Mo?t=55s

As I said, documentary.

talksthetalk

844 posts

21 months

[news] 
Tuesday 9th April 2013 quote quote all
Used to run my 1.6 company golf on 98RON as I had a fuel card.
Until my Finance Director found out....
Made him get a letter from the lease co though, just to be a PITA

Andy665

1,285 posts

114 months

[news] 
Wednesday 10th April 2013 quote quote all
Lexus have been using a combination of port and direct injection for years. Different systems work best under different operating conditions so being able to switch between the two or using both at the same time makes a lot of sense

Dr G

11,259 posts

128 months

[news] 
Wednesday 10th April 2013 quote quote all
FSI and all variants of it (FSI, TSI, TFSI) are used mostly as brand names for direct injection now. They're not specific acronyms/technologies anymore.

Fastdruid

2,381 posts

38 months

[news] 
Wednesday 10th April 2013 quote quote all
scarble said:
CJP80 said:
And Carbon Coking...
Audi is now using a mix of DFI and indirect (port injection).
That's more of an emissions thing as DI is good for some things but worse for others (or something like that), other than on PH I've never heard of coking being an issue and working in the industry you'd think I would have if it was as big a deal as PH makes out?

Edited by scarble on Monday 8th April 11:58
It's an issue not just with Audi/VAG but all (G)DI cars. Basically when you have a 'normal' port injection engine the petrol washes the valves (and inlet) clean. On a GDI (and especially in turbo'd motors) the blowby through the crankcases and out the vent combined with the EGR coats the inlet valves in sh*t.

http://www.thetruthaboutcars.com/2012/05/ask-an-en...

In the case of the Mazda MZR L3-VDT (ie the MPS engine) owners recommend to add a catch tank instead of the vent from the crankcases and to clean the valves with a spray cleaner, there is even options to inject cleaner regularly while driving.






Edited by Fastdruid on Wednesday 10th April 09:21

scarble

4,390 posts

43 months

[news] 
Wednesday 10th April 2013 quote quote all
Some Gump said:
http://youtu.be/0116mkt7-Mo?t=55s
As I said, documentary.
The "you know stuff" comment was aimed at the other bloke tongue out
stop selective quoting me!
So what is direct port injection, srs?

Fastdruid said:
It's an issue not just with Audi/VAG but all (G)DI cars. Basically when you have a 'normal' port injection engine the petrol washes the valves (and inlet) clean. On a GDI (and especially in turbo'd motors) the blowby through the crankcases and out the vent combined with the EGR coats the inlet valves in sh*t.
I understand why people say it, I understand the theory, I'm just not sure I've really heard of this actually causing issues. In the early days of EGR we sometimes had issues with idle valves on some engines gumming up but they're a smaller valve driven by a weak solenoid and not exhibited to considerable airflow or temperature as the intake valves are and it was never really that big an issue and sometimes even "fixes its self". I'm not saying the problem doesn't exist, just that I've not heard of any GDI engine being particularly unreliable but I'm receptive to being proven wrong smile
N.B. one article written by one guy is not conclusive. He makes some good arguments. But then it's the same as the DPF issue. Lrn2 Italian tuneup noobs.

Edited by scarble on Wednesday 10th April 10:45

Fastdruid

2,381 posts

38 months

[news] 
Wednesday 10th April 2013 quote quote all
scarble said:
Fastdruid said:
It's an issue not just with Audi/VAG but all (G)DI cars. Basically when you have a 'normal' port injection engine the petrol washes the valves (and inlet) clean. On a GDI (and especially in turbo'd motors) the blowby through the crankcases and out the vent combined with the EGR coats the inlet valves in sh*t.
I understand why people say it, I understand the theory, I'm just not sure I've really heard of this actually causing issues. In the early days of EGR we sometimes had issues with idle valves on some engines gumming up but they're a smaller valve driven by a weak solenoid and not exhibited to considerable airflow or temperature as the intake valves are and it was never really that big an issue and sometimes even "fixes its self". I'm not saying the problem doesn't exist, just that I've not heard of any GDI engine being particularly unreliable but I'm receptive to being proven wrong smile
N.B. one article written by one guy is not conclusive. He makes some good arguments. But then it's the same as the DPF issue. Lrn2 Italian tuneup noobs.

Edited by scarble on Wednesday 10th April 10:45
That was just one write up, a google on the subject will result in many more but you might like to see the pictures here and read the links from this one. http://forums.vwvortex.com/showthread.php?4397707

Fastdruid

2,381 posts

38 months

[news] 
Wednesday 10th April 2013 quote quote all
Also see a patent filed by VW both admitting the issue and suggesting a fix
http://www.google.com/patents?id=fLITAAAAEBAJ&...

trashbat

4,001 posts

39 months

[news] 
Wednesday 10th April 2013 quote quote all
scarble said:
I'm not saying the problem doesn't exist, just that I've not heard of any GDI engine being particularly unreliable but I'm receptive to being proven wrong smile
Edited by scarble on Wednesday 10th April 10:45
There's plenty. Alfa JTS (the 156/GT era) is a good example. Early direct injection; the injectors clog and, I think separately, carbon builds up in the engine due to the aforementioned lack of wash. There are also resultant issues (like failure to atomise the fuel properly means fuel in the oil, which acts as a thinner, so you get increased engine wear).

scarble

4,390 posts

43 months

[news] 
Wednesday 10th April 2013 quote quote all
I stand corrected. Or educated at least tongue out
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)?

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..

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.

and how have diseasels coped all these years? They still have crank breathers right?

ETA: I think I've come up with my own solution, probably even cheaper than any fancy catalytic coatings like that VAG patent which will wear out like a cat does instead just burn the deposits off:


Edited by scarble on Wednesday 10th April 11:32

trashbat

4,001 posts

39 months

[news] 
Wednesday 10th April 2013 quote quote all
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.

The answer to blocked injectors, which presumably clog with carbon rather than crud from anywhere else, is removal and ultrasonic cleaning. You would think that you could do something in-situ, like the vibration systems in cameras that remove dust.

I don't really know what the state of the art is now. My JTS is a 2002 design, with only a few mainstream cars using DI before, and it's fair to say that the engine is beset with a few more problems than its non-DI predecessor. You can expect these cars to have issues with it after maybe 50-70k miles, like mine did. I also know the engine has some carbon build up since we had the head off to address the injectors.

I don't know if e.g. an Italian tuneup will have a significant impact. Especially with stuff like VVT, it can't hurt to put the engine through its different profiles, but it's not going to do all that much to address the long term build up.
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