Direction Injection & Engine Longevity, take 2.

[mareakin]

Disclaimer: Just because something is printed in a 'respectable' online publication does not make it true. It also doesn't necessarily make it false either.

http://www.thetruthaboutcars.com/2012/05/ask-an-engineer-gdi-problems-in-a-nutshell/

Some excerpts:

1. 'If you want to keep your car for a long period of time, the long-term reliability of a GDI engine is an important factor.'

2. 'GDI requires significantly higher fuel inlet pressures than port injection. This puts a great deal of strain on every piece of the fuel delivery chain. This is not a problem on a new engine. 50,000 miles down the road, and it may be.'

3. 'The reason these issues have slipped through to production is that they won’t show up in a 500,000 mile torture test.'

---------------------------------

Does this man know what he's talking about? Maybe! We'll have to wait for many hundreds of thousands of Hyundai Sonatas to put many 10's and 100's of thousands of miles before we'll have some real data.


---------------------------------------

A comment-er writes: "This is fear-mongering. You make it sound like these failure are common to all DI engines. In fact, the majority of DI engines are very reliable. We’ve been doing ethanol and DI diesels for years, and these effects are well-known. Any new engine, DI or not, will have growing pains. Being an engineer with a little more knowledge than the average observer does not mean you can make unsubstantiated generalizations about this technology."

Some real anecdotal 'data': "I have or have had a total of five direct injecton motors in my driveway, all are or were made by VW. The 2.0T in my wife’s 2006 A3 needed the valves cleaned at 80k miles after a fair but constant 5 years of service. The valve cleaning cost $600, and the car has been reliable since. the other three cars are driven by what I would call more ‘spirited’ drivers and have about 100k miles between them with no injector issues. The last one, the 2.0 TDI diesel motor had multiple problems after only 8k miles. I’d say that my experiences support the article, it’s not fear mongering, but it’s not a deal breaker, either. Just another hassle on a newer car, which is inevitable. I’d buy another VW 2.0T car, but I would never buy a TDI again."

 

[JHZR2]

What are the highest mileage problem free DI gas engines out there right now?

 

[A_Harman]

So if this writer were discussing diesel fuel injection, would he be telling us there would be no way one of those systems would last long enough to even get out of the driveway?

 

[cchase]

"as we approach the efficiency limits of internal combustion engines"

I wonder how he defines what those limits are. Certainly we are nowhere near a theoretical efficiency limit.

 

[BMWTurboDzl]

BMW had a major problem with HPFP on the N54. Excess ethanol was to blame. IIRC it was a North American prob.

 

[SteveSRT8]

Originally Posted By: cchase
"as we approach the efficiency limits of internal combustion engines"

I wonder how he defines what those limits are. Certainly we are nowhere near a theoretical efficiency limit.


But we are well into the area of diminishing returns where each additional advancement costs a lot more and delivers only incremental improvement.

I am a firm believer in the manufacturers putting tech on the roads for us to do 'real world' testing on for them. So I have never been an early adopter.

 

[Trav]

Originally Posted By: JHZR2
What are the highest mileage problem free DI gas engines out there right now?

Mitsubish introduced GDI in Europe in the late 90's.
Lots of problems until the sulphur limit was reduced in Germany and other first Euro countries to 10 PPM.
The lean burn cats (GDI can operate under fuel / air ratio of 1 : 40) could then be implemented without being destroyed by NOx. Now the engines are reliable as any other.

From an article..
Quote:
One of the few drawbacks of GDI engine is the higher NOx pollutant level. Luckily, a newly developed catalytic convertor deal comfortably with it. Nevertheless, USA and many developing countries cannot be benefited by it because their high-sulphur petrol will damage the catalyst.



This is from Sept 09. I believe now the limit for the US is under 20PPM from what i have been reading.

http://www.acfa.org.sg/pdf/ACFANewsVol7No5.pdf

IMO GDI will be fine and all the bugs worked out in a few years.
I can see some sort of small TBI injector coming back to perform the fuel delivery duties at idle to cure the valve deposit and fuel dilution issues.
I can also see this being combined with a additional chemical being injected over long periods like some manufacturers use on diesels today.

 

[mechtech2]

Any upstream injector attenuates or nullifies any DI advantages.

 

[Shannow]

Rubbish...it depends on when the additional injector is used in the cycle...If it is used every single revolution of the engine, I agree.

If used at idle to "wash" the valves, that doesn't negate D.I. advantages...If used to deliver a small tank of high octane high additised fuel at W.O.T to wash the valves, it still doesn't negate the D.I. usefulness.

IMO, the blowby products of D.I. will be very different to a homogenous charge engine, and we may find that they need to go to a different place than back in the inlet.

The attached link, the "engineer" states that EGR is to "lean out combustion mixture". High injection pressures haven't seen diesel fuel lines rupturing all over the place either. "Nutshell" analyses with inaccuracies and half truths help perpetuate fear.

 

[PZR2874]

Originally Posted By: JHZR2
What are the highest mileage problem free DI gas engines out there right now?


I have one. And it's beaten on

I don't have valve issues. SeaFoam is my best friend, EGR is deleted, OCC is installed, specified tune is a must.

IMHO, they are a maintainence hoe.... For someone like me that enjoys cars.... It's not a problem, but a passion.

 

[SteveSRT8]

Originally Posted By: Shannow
Rubbish...it depends on when the additional injector is used in the cycle...If it is used every single revolution of the engine, I agree.

If used at idle to "wash" the valves, that doesn't negate D.I. advantages...If used to deliver a small tank of high octane high additised fuel at W.O.T to wash the valves, it still doesn't negate the D.I. usefulness.

IMO, the blowby products of D.I. will be very different to a homogenous charge engine, and we may find that they need to go to a different place than back in the inlet.

The attached link, the "engineer" states that EGR is to "lean out combustion mixture". High injection pressures haven't seen diesel fuel lines rupturing all over the place either. "Nutshell" analyses with inaccuracies and half truths help perpetuate fear.


Likewise here. An extra injector for part time duty will be transparent in operation.

Please explain how the blowby would be different as I'm interested in that comment. DI is merely an incremental improvement and should not make any difference. Higher compression but better efficiency.

And engineers know that EGR is for NOX reductions. It is a band aid and is going away on really well developed engines.

 

[rjundi]

My wife is liking the Kia Optima turbo. Maybe the 2.0L GDi with 274HP and full torque at 1750RPM coupled to 34MPG on regular fuel may not be a low maintenance like her Subaru Legacy turbo with 140k miles on it.

 

[PZR2874]

No forced induction car i've ever owned has been low maint. HAven't heard any problems on the Kia's as of yet.

 

[Nick R]

Originally Posted By: rjundi
My wife is liking the Kia Optima turbo. Maybe the 2.0L GDi with 274HP and full torque at 1750RPM coupled to 34MPG on regular fuel may not be a low maintenance like her Subaru Legacy turbo with 140k miles on it.


I wouldn't run that on regular. I would be running it on premium.

 

[Shannow]

Originally Posted By: SteveSRT8
Please explain how the blowby would be different as I'm interested in that comment. DI is merely an incremental improvement and should not make any difference. Higher compression but better efficiency.


One of the real advantages of D.I. in my opinion is in the crevice areas.

Crevices are the bit between the top ring and the piston crown, where there is a clearance between the piston and the wall...other ones are the gaps that exist when a head gasket is larger than the size of the bore, little angular differences in valve seats, that little space inside the sparkplug, where the insulator meets the outer metal shell.

During the compression stroke, in a traditional homogenous charge engine, the "crevice" fills up with hydrocarbon/air mix, and it stays there uncombusted (the small gaps down allow flame propogation, just like quench), and the hydrocarbons stay there until the exhaust valve cracks, and the cylinder blows down.

These have always been a major source of the HC in an engine's exhaust, which has pushed higher rings, tighter gaps between piston and cylinder to reduce the phenomenon.

D.I. should theoretically, and in the stratified charge engines we were taught at Uni, have the crevices full of air, as the fuel doesn't get introduced until later, and thus have way lower HC emissions.

While reading this thread the first time, it hit me that in order for blowby to exist, it's these crevices that have to be the first products to make it through the rings.

So in D.I., where the ring crevices are filled mostly with air, the blowby should have way way less fuel, less CO, and maybe a little more NOx than in a homogenous fueled engine.

Maybe the appropriate thing to do with the blowby in a D.I. engine is to get the entrained oil out of it, and put it through the cat, rather than the engine.

 

[demarpaint]

Originally Posted By: SteveSRT8
Originally Posted By: cchase
"as we approach the efficiency limits of internal combustion engines"

I wonder how he defines what those limits are. Certainly we are nowhere near a theoretical efficiency limit.


But we are well into the area of diminishing returns where each additional advancement costs a lot more and delivers only incremental improvement.

I am a firm believer in the manufacturers putting tech on the roads for us to do 'real world' testing on for them. So I have never been an early adopter.


Agreed, the public does the major testing at their expense. Give it time, the technology will be perfected like every other new technology was, or dropped for hopefully something better.

 

[SteveSRT8]

Originally Posted By: Shannow
Originally Posted By: SteveSRT8
Please explain how the blowby would be different as I'm interested in that comment. DI is merely an incremental improvement and should not make any difference. Higher compression but better efficiency.


One of the real advantages of D.I. in my opinion is in the crevice areas.

Crevices are the bit between the top ring and the piston crown, where there is a clearance between the piston and the wall...other ones are the gaps that exist when a head gasket is larger than the size of the bore, little angular differences in valve seats, that little space inside the sparkplug, where the insulator meets the outer metal shell.

During the compression stroke, in a traditional homogenous charge engine, the "crevice" fills up with hydrocarbon/air mix, and it stays there uncombusted (the small gaps down allow flame propogation, just like quench), and the hydrocarbons stay there until the exhaust valve cracks, and the cylinder blows down.

These have always been a major source of the HC in an engine's exhaust, which has pushed higher rings, tighter gaps between piston and cylinder to reduce the phenomenon.

D.I. should theoretically, and in the stratified charge engines we were taught at Uni, have the crevices full of air, as the fuel doesn't get introduced until later, and thus have way lower HC emissions.

While reading this thread the first time, it hit me that in order for blowby to exist, it's these crevices that have to be the first products to make it through the rings.

So in D.I., where the ring crevices are filled mostly with air, the blowby should have way way less fuel, less CO, and maybe a little more NOx than in a homogenous fueled engine.

Maybe the appropriate thing to do with the blowby in a D.I. engine is to get the entrained oil out of it, and put it through the cat, rather than the engine.


Thank you for that. I suppose that until combustion pressures build to force the ring out against the cylinder wall there would be fuel/air mix getting past them in a port injected setup.

I'm already seeing much more elaborate PCV plumbing, as in "factory catch cans", on newer cars. Most newer cars that we get the intake off of have tons of oil in it. My car can hold about a pint!

 

[SteveSRT8]

Originally Posted By: demarpaint
Originally Posted By: SteveSRT8
Originally Posted By: cchase
"as we approach the efficiency limits of internal combustion engines"

I wonder how he defines what those limits are. Certainly we are nowhere near a theoretical efficiency limit.


But we are well into the area of diminishing returns where each additional advancement costs a lot more and delivers only incremental improvement.

I am a firm believer in the manufacturers putting tech on the roads for us to do 'real world' testing on for them. So I have never been an early adopter.


Agreed, the public does the major testing at their expense. Give it time, the technology will be perfected like every other new technology was, or dropped for hopefully something better.


While there may be something better I think DI is here to stay. Not everyone is having problems and the HP and economy gains are fairly significant and getting better as the tech is developed.

But the early adopters are the developers!

 

[demarpaint]

Originally Posted By: SteveSRT8
Originally Posted By: demarpaint
Originally Posted By: SteveSRT8
Originally Posted By: cchase
"as we approach the efficiency limits of internal combustion engines"

I wonder how he defines what those limits are. Certainly we are nowhere near a theoretical efficiency limit.


But we are well into the area of diminishing returns where each additional advancement costs a lot more and delivers only incremental improvement.

I am a firm believer in the manufacturers putting tech on the roads for us to do 'real world' testing on for them. So I have never been an early adopter.


Agreed, the public does the major testing at their expense. Give it time, the technology will be perfected like every other new technology was, or dropped for hopefully something better.


While there may be something better I think DI is here to stay. Not everyone is having problems and the HP and economy gains are fairly significant and getting better as the tech is developed.

But the early adopters are the developers!


They've spent too much money on DI to can it, that's for sure. They've taken the plunge, and will perfect it right up until they feel there is a better technology, then it starts all over again. Right now they have to get their ROI, one way or another.

 

[PZR2874]

Originally Posted By: Nick R
Originally Posted By: rjundi
My wife is liking the Kia Optima turbo. Maybe the 2.0L GDi with 274HP and full torque at 1750RPM coupled to 34MPG on regular fuel may not be a low maintenance like her Subaru Legacy turbo with 140k miles on it.


I wouldn't run that on regular. I would be running it on premium.


This has been debated, without a retune it does nothing. I myself was dumbfounded when I learned you can use 87octane