LT1 "Direct Injection" documented concerns
02-28-2013, 08:44 AM
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LT1 "Direct Injection" documented concerns
Since Direct Injection seems to be the latest craze...
My wifes new SRX has a DI V6; and I was pleasantly surprised at the low RPM torque available. The torque curve is flat at about 2500rpm upwards. No longer need to get into the 3000's in order to have healthy pull. It's almost too good to be true.
I started doing some searches about DI; and read about it's Achilles' Heel... carbon deposits on the upwind side of the intake valve - which will start reducing power. There's one VW engine that is estimated to lose 1 hp per every 500 miles.
do your own Google search for direct injection carbon. Here's one of many:
http://www.edmunds.com/autoobserver-...-adopters.html
what are we in store for here?
My wifes new SRX has a DI V6; and I was pleasantly surprised at the low RPM torque available. The torque curve is flat at about 2500rpm upwards. No longer need to get into the 3000's in order to have healthy pull. It's almost too good to be true.
I started doing some searches about DI; and read about it's Achilles' Heel... carbon deposits on the upwind side of the intake valve - which will start reducing power. There's one VW engine that is estimated to lose 1 hp per every 500 miles.
Ameer Haider, GM’s assistant chief engineer for V6 engines, certainly knows the problem, telling AutoObserver, “DI engines are prone to forming oily deposits on the intake valves, unlike in port fuel-injected engines, where a constant spray of fuel into the port allows any deposits to wash away. With DI engines, the fuel gets injected directly into the combustion chamber, so there isn't a chance for the deposits to wash away. Typically, deposits form when soot – which is an end-product of combustion – adheres to the valve stem.”
The main purpose of VW’s patent application was to propose a fix for DI engine carbon deposits: specifically, applying “a catalytic surface” to the engine valves that “counteracts the formation of carbon deposits.” But nearly 10 years later, there’s ample evidence that this and other potential solutions have failed.
The main purpose of VW’s patent application was to propose a fix for DI engine carbon deposits: specifically, applying “a catalytic surface” to the engine valves that “counteracts the formation of carbon deposits.” But nearly 10 years later, there’s ample evidence that this and other potential solutions have failed.
http://www.edmunds.com/autoobserver-...-adopters.html
what are we in store for here?
Last edited by Mike Mercury; 02-28-2013 at 08:55 AM.
02-28-2013, 09:09 AM
#3
Le Mans Master
Very interesting Mike. Glad I was not planning on a move to the C7 right away. Although I would hope that the Corvette Engine design staff would have look at it and considered it when the started their initial design seeing it has been a known issue for some 10 years now. After all they did say that they have over 6,000 CPU hours in just the design of the combustion chamber.
I guess we just need to see what happens down the line.
I guess we just need to see what happens down the line.
02-28-2013, 09:23 AM
#4
Le Mans Master
I read in one of the many articles on the LT1, albeit some time ago, that they designed the PCV system to seperate the oil and carbon from the gasses recirculating to the intake. This is the major contributor to the carbon deposits on intake valves in DI engines. I'm not sure if some of that 6000 hrs cpu time on chamber design will help this as well or not.
This does leave the question of how these gasses and oil/carbon are seperated. They have to go somewhere.
This does leave the question of how these gasses and oil/carbon are seperated. They have to go somewhere.
02-28-2013, 09:39 AM
#5
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From the "Gen 5 Small Block Lubrication System" new release:
PCV-integrated rocker covers
One of the most distinctive features of the all-new Gen 5 engine is its domed rocker covers, which house a patent-pending integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption. It also contributes to low emissions for the Gen 5.
The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases – about three times the oil/air separation capability of previous engines. Each cover features an inlet and outlet path for the crankcase gases, with the separated oil dropping back onto the engine within the covers and the remaining air/gases circulated back into air intake stream for combustion. The system also prevents moisture from accumulating in the engine.
This integrated PCV system is an essential contributor of the Gen 5’s efficient performance and long-term durability – and the domes for it on the rocker covers make the Gen 5 engine instantly recognizable.
PCV-integrated rocker covers
One of the most distinctive features of the all-new Gen 5 engine is its domed rocker covers, which house a patent-pending integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption. It also contributes to low emissions for the Gen 5.
The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases – about three times the oil/air separation capability of previous engines. Each cover features an inlet and outlet path for the crankcase gases, with the separated oil dropping back onto the engine within the covers and the remaining air/gases circulated back into air intake stream for combustion. The system also prevents moisture from accumulating in the engine.
This integrated PCV system is an essential contributor of the Gen 5’s efficient performance and long-term durability – and the domes for it on the rocker covers make the Gen 5 engine instantly recognizable.
02-28-2013, 10:14 AM
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From the "Gen 5 Small Block Lubrication System" new release:
PCV-integrated rocker covers
One of the most distinctive features of the all-new Gen 5 engine is its domed rocker covers, which house a patent-pending integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption. It also contributes to low emissions for the Gen 5.
The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases – about three times the oil/air separation capability of previous engines. Each cover features an inlet and outlet path for the crankcase gases, with the separated oil dropping back onto the engine within the covers and the remaining air/gases circulated back into air intake stream for combustion. The system also prevents moisture from accumulating in the engine.
This integrated PCV system is an essential contributor of the Gen 5’s efficient performance and long-term durability – and the domes for it on the rocker covers make the Gen 5 engine instantly recognizable.
PCV-integrated rocker covers
One of the most distinctive features of the all-new Gen 5 engine is its domed rocker covers, which house a patent-pending integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption. It also contributes to low emissions for the Gen 5.
The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases – about three times the oil/air separation capability of previous engines. Each cover features an inlet and outlet path for the crankcase gases, with the separated oil dropping back onto the engine within the covers and the remaining air/gases circulated back into air intake stream for combustion. The system also prevents moisture from accumulating in the engine.
This integrated PCV system is an essential contributor of the Gen 5’s efficient performance and long-term durability – and the domes for it on the rocker covers make the Gen 5 engine instantly recognizable.
02-28-2013, 10:37 AM
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Originally Posted by from article
The reason these issues have slipped through is that they won’t show up in a 500,000 mile torture test. These types of issues will appear after years of short trips; developing as early as 40k miles
the back of the intake valve on a DI engine can get much hotter than an equivalent port injected engine mostly because there is not a steady stream of fuel cooling it off every cycle. Whatever gets deposited on the back of the valve gets baked on as a result. And without any fuel or cleaning additives being flowed in the intake runners - there's nothing to clean/wash-away any forming deposits.
From what I have read on the VW & Audi forums a catch can doesn't solve the problem. Its been said that the deposits are also from the accumulation of oil that slips past the valve guide seals.
a catch can will not work. it will help a little but it will not solve the problem. the carbon buildup is caused by blow-by and nothing really cleaning the valves. one thing i did see in the Q5 3.2 engine that was different than the A6 engine was a small injector up top. it sprays some gas from up top to address this issue.
the additional "small injector" mentioned above has been called "dual DI"... as there's two injectors; one directly in the cylijder... a secone smaller one in the intave valve runner.
also:
Engineers with some of these car companies say it boils down to cam phasing based on airflow, temperature, and throttle demand. Once you have the magic, the buildup will be small.
Last edited by Mike Mercury; 02-28-2013 at 10:47 AM.
02-28-2013, 10:38 AM
#8
For some reason GM and Ford engines haven't been nearly as bad as the Germans with DI and carbon buildup. I've seen some eviednece of it on the Camaro V6's but they are nowhere close to the Audi/VW engines and the BMW N54 engine that I have in my car.
BMW had to come up with system to blast the intake ports clean with ground up walnut shells. I even had it covered under warranty. Just a poor design.
Here's what it looks like on the Bimmers.
BMW had to come up with system to blast the intake ports clean with ground up walnut shells. I even had it covered under warranty. Just a poor design.
Here's what it looks like on the Bimmers.
02-28-2013, 10:45 AM
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most of the major automakers are still having issues with implementation of DI technology. VW/Audi FSI engines have major carbon/sludging issues, BMW has gone through 6 evisions of ttheir N54 engines. Toyota seems to have the better system, using a combination of both port and direct injection "dual".
02-28-2013, 10:53 AM
#10
Safety Car
GM has been acutely aware of documented direct injection carbon build up problems for years and specifically designed many features into the LT1 to not have the problems that BMW, Audi and others have been, and are still encountering.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
02-28-2013, 11:25 AM
#11
Le Mans Master
GM has been acutely aware of documented direct injection carbon build up problems for years and specifically designed many features into the LT1 to not have the problems that BMW, Audi and others have been, and are still encountering.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
02-28-2013, 11:32 AM
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GM has been acutely aware of documented direct injection carbon build up problems for years and specifically designed many features into the LT1 to not have the problems that BMW, Audi and others have been, and are still encountering.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
02-28-2013, 12:06 PM
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http://www.asphaltandrubber.com/news...uel-injection/
"“We want the MST’s to be accessible, understandable, fun to work on, and easy to modify, so we are removing barriers for dealers and regular riders that like to wrench and tune their bikes. "
Hmmm
"“We want the MST’s to be accessible, understandable, fun to work on, and easy to modify, so we are removing barriers for dealers and regular riders that like to wrench and tune their bikes. "
Hmmm
02-28-2013, 12:06 PM
#14
Race Director
An interesting issue Mike and thanks for sharing. I have a 2010 CTS Wagon with the 3.6L engine the same as the Camaro V6 with 42k miles so far and no issues that I am aware.
02-28-2013, 12:08 PM
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GM has been acutely aware of documented direct injection carbon build up problems for years and specifically designed many features into the LT1 to not have the problems that BMW, Audi and others have been, and are still encountering.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
I have faith that with that advance knowledge, with 10,000,000 hours of computer modeling and tens of thousands of miles of real world driving experience, that GM will not have the Di carbon build up problems.
Tired of constant doom and gloom predictions about GM is going to fail at this and fail at that.
carbon buildup - on the back side of the intake valve on GDI engines - is a real-world documented concern. It's not hype. Burying ones head in the sand will not necessarily keep the problem away.
Accepting a promise that a mfgr has cured the ailement - is also foolish... as the newer VW design (that they patented) ended up not making any improvement.
02-28-2013, 12:35 PM
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On the Cobalt forums I never really heard a problem, looks like some on that forum have some major problems with build up.
02-28-2013, 12:42 PM
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Hmm - negativity over potential C7 mechanical issues, as opposed to design and styling. Does this then qualify as a "hater" thread and "raining on the C7 parade"?
Have those expressing concern actually driven one to see if their concerns are valid?...................of course not, just as those expressing dislike for the styling have not seen it in person.
So, why is this thread any more pertinent - especially coming from one who aggressively trashed anyone who expressed dislike for the C7 rear styling - or less negative than those styling questions?
The styling questions made comparisons to the Camaro tail lights; this thread makes comparisons to VW DI systems. At least the style questions stayed in the GM family.
Could the question possibly be any more .........uh, "inconsistent", to be polite about it?
Where is the outrage over this premature and unsubstantiated criticism of the new C7?
Have those expressing concern actually driven one to see if their concerns are valid?...................of course not, just as those expressing dislike for the styling have not seen it in person.
So, why is this thread any more pertinent - especially coming from one who aggressively trashed anyone who expressed dislike for the C7 rear styling - or less negative than those styling questions?
The styling questions made comparisons to the Camaro tail lights; this thread makes comparisons to VW DI systems. At least the style questions stayed in the GM family.
Could the question possibly be any more .........uh, "inconsistent", to be polite about it?
Where is the outrage over this premature and unsubstantiated criticism of the new C7?
Last edited by tuxnharley; 02-28-2013 at 12:51 PM.
02-28-2013, 12:59 PM
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Hmm - negativity over potential C7 mechanical issues, as opposed to design and styling. Does this then qualify as a "hater" thread and "raining on the C7 parade"?
Have those expressing concern actually driven one to see if their concerns are valid?...................of course not, just as those expressing dislike for the styling have not seen it in person.
So, why is this thread any more pertinent - especially coming from one who aggressively trashed anyone who expressed dislike for the C7 rear styling - or less negative than those styling questions?
The styling questions made comparisons to the Camaro tail lights; this thread makes comparisons to VW DI systems. At least the style questions stayed in the GM family.
Could the question possibly be any more .........uh, "inconsistent", to be polite about it?
Where is the outrage over this premature and unsubstantiated criticism of the new C7?
Have those expressing concern actually driven one to see if their concerns are valid?...................of course not, just as those expressing dislike for the styling have not seen it in person.
So, why is this thread any more pertinent - especially coming from one who aggressively trashed anyone who expressed dislike for the C7 rear styling - or less negative than those styling questions?
The styling questions made comparisons to the Camaro tail lights; this thread makes comparisons to VW DI systems. At least the style questions stayed in the GM family.
Could the question possibly be any more .........uh, "inconsistent", to be polite about it?
Where is the outrage over this premature and unsubstantiated criticism of the new C7?
