C7 Direct Injection Carbon Fouling?
10-24-2013, 12:55 PM
#1
Le Mans Master
Thread Starter
C7 Direct Injection Carbon Fouling?
My son had a Mazdaspeed 3 with direct injection and the intake valves carboned up. This has been a recurring problem with most Direct Injection engines because they don't have the washing effect of the fuel over the intake valves.
Has Chevy done anything in particular to keep this from happening to the new C7 engine?
Has Chevy done anything in particular to keep this from happening to the new C7 engine?
10-24-2013, 01:05 PM
#2
Team Owner
Wait and see.
10-24-2013, 01:38 PM
#4
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10-24-2013, 01:40 PM
#5
Burning Brakes
This has been a hot button subject for the Camaro community with their direct injected V-6's. PCV oil catch cans seem to be the solution.
10-24-2013, 02:57 PM
#6
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10-24-2013, 04:08 PM
#7
Mercedes just switched to DI recently so it remains to be seen what they are about. I think GM is better at controlling DI side effects than BMW and Audi though. They specially designed the valve covers and PCV systems on the GenV motors to prevent the oil buildup from happening.
We'll just have to wait and see but I seriously doubt the LT1 will have the same problems as the MS3, BMW N54, or VW/Audi 2.0T/V6.
We'll just have to wait and see but I seriously doubt the LT1 will have the same problems as the MS3, BMW N54, or VW/Audi 2.0T/V6.
10-24-2013, 04:39 PM
#8
Team Owner
=Kappa;1585257599They specially designed the valve covers and PCV systems on the GenV motors to prevent the oil buildup from happening.
We'll just have to wait and see but I seriously doubt the LT1 will have the same problems as the MS3, BMW N54, or VW/Audi 2.0T/V6.
We'll just have to wait and see but I seriously doubt the LT1 will have the same problems as the MS3, BMW N54, or VW/Audi 2.0T/V6.
And hope it's true.Here's what has been posted before:
From the BASH:
Z51 car with MR has launch control
Dual mass flywheel actually is smaller and has less total mass than c6 flywheel
There was no validity to the claims of the unhackable ecu...they said like anything...it'll be hacked....probably
Can run on 87 octane but premium rec....same as usual
Like. I said earlier...they specifically said NO ethanol beyond 10% mixes
They said they DO have final power numbers and its more than 450...as we know
Rev match paddles on the wheel both do same thing...shut system on and off...thats it. Just a way to share steering wheel with auto cars
Residual build up from direct injection on intake valves is a non issue with lt1. Pcv system is two sided, and there are aggressive measures taken to relieve block pressure and handle oil vapor
Dual mass flywheel actually is smaller and has less total mass than c6 flywheel
There was no validity to the claims of the unhackable ecu...they said like anything...it'll be hacked....probably
Can run on 87 octane but premium rec....same as usual
Like. I said earlier...they specifically said NO ethanol beyond 10% mixes
They said they DO have final power numbers and its more than 450...as we know
Rev match paddles on the wheel both do same thing...shut system on and off...thats it. Just a way to share steering wheel with auto cars
Residual build up from direct injection on intake valves is a non issue with lt1. Pcv system is two sided, and there are aggressive measures taken to relieve block pressure and handle oil vapor
Earlier Gen 5 News Release:
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.
10-24-2013, 08:48 PM
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I've posted about this in the Advanced section of a certain popular forum for LSx engines, but I'll repost some of that here with some additional detail.
To simplify, without port injectors washing and cooling the valves, the two things that cause the valve deposits are PCV-system crankcase vapors (from suspended oil droplets) and hot intake valves due to cam phasing. The newest generation DI engines have pretty elaborate air-oil separators from the factory that go through two or three stages of impactor plates, cyclonic separators, etc. So that helps a lot with PCV-related contributions to the buildup.
The other issue, which is often not fully understand, is EGR gases. It's obvious that gases from an external EGR valve can contribute to the problem. A lot of current production models don't have external EGR valves because they can get enough internal EGR for fuel economy and emissions by using cam phasing.
You know all those early Audi direct injected engines with valve deposit problems? Notice how they mostly had a single cam phaser on the intake side? The big issue is spitback of hot gases during valve overlap at part throttle. The solution to it is to stop opening the intake valve at the end of the exhaust stroke, while the piston is still rising. Newer DI engines are already doing this.
Here's some crappy MS Paint pics I made. First look at a sort of "textbook" valve timing diagram with made-up cam profiles having no overlap.
360 is TDC Intake, where the gas exchange occurs. Before 360 (looking to the left), the piston is rising at the end of the exhaust stroke. After 360 (looking to the right), the piston is moving downward on the intake stroke. Valve deposit-causing timing is below:
At cruising load, when pressure from exhaust gases in the chamber is higher than intake pressure, the hot gases spit out the intake valve. So now you have deposits of junk, especially soot (common on DI engines), and heat promoting adhesion of valve deposits. But what if I have an exhaust cam phaser and I want to try and avoid this spitback, like current Ford Ecoboost and Hyundai DI engines do?
We retard (or just park) the intake cam so that the intake valve opens after TDC, when the piston is falling. Then we retard the exhaust valve for internal EGR to improve fuel economy and emissions. Here's a published map of valve overlap position vs speed and load on a Ford Ecoboost 2.0 :
So how does this relate to the Gen V small block? I don't know the baseline cam specs off the top of my head, but with its simple cam phaser it can't dial in additional overlap like on a dual overhead cam engine. All the LT1 cam phaser can do is retard the intake valve opening and exhaust valve closing in equal increments, so the piston can't push hot exhaust gases back into the port. See below:
So in conclusion, if GM has the crankcase oil separation under control, and the valvetrain doesn't allow overlap before TDC intake, they've probably taken the proper precautions to limit valve deposits normally associated with DI engines.
To simplify, without port injectors washing and cooling the valves, the two things that cause the valve deposits are PCV-system crankcase vapors (from suspended oil droplets) and hot intake valves due to cam phasing. The newest generation DI engines have pretty elaborate air-oil separators from the factory that go through two or three stages of impactor plates, cyclonic separators, etc. So that helps a lot with PCV-related contributions to the buildup.
The other issue, which is often not fully understand, is EGR gases. It's obvious that gases from an external EGR valve can contribute to the problem. A lot of current production models don't have external EGR valves because they can get enough internal EGR for fuel economy and emissions by using cam phasing.
You know all those early Audi direct injected engines with valve deposit problems? Notice how they mostly had a single cam phaser on the intake side? The big issue is spitback of hot gases during valve overlap at part throttle. The solution to it is to stop opening the intake valve at the end of the exhaust stroke, while the piston is still rising. Newer DI engines are already doing this.
Here's some crappy MS Paint pics I made. First look at a sort of "textbook" valve timing diagram with made-up cam profiles having no overlap.
360 is TDC Intake, where the gas exchange occurs. Before 360 (looking to the left), the piston is rising at the end of the exhaust stroke. After 360 (looking to the right), the piston is moving downward on the intake stroke. Valve deposit-causing timing is below:
At cruising load, when pressure from exhaust gases in the chamber is higher than intake pressure, the hot gases spit out the intake valve. So now you have deposits of junk, especially soot (common on DI engines), and heat promoting adhesion of valve deposits. But what if I have an exhaust cam phaser and I want to try and avoid this spitback, like current Ford Ecoboost and Hyundai DI engines do?
We retard (or just park) the intake cam so that the intake valve opens after TDC, when the piston is falling. Then we retard the exhaust valve for internal EGR to improve fuel economy and emissions. Here's a published map of valve overlap position vs speed and load on a Ford Ecoboost 2.0 :
So how does this relate to the Gen V small block? I don't know the baseline cam specs off the top of my head, but with its simple cam phaser it can't dial in additional overlap like on a dual overhead cam engine. All the LT1 cam phaser can do is retard the intake valve opening and exhaust valve closing in equal increments, so the piston can't push hot exhaust gases back into the port. See below:
So in conclusion, if GM has the crankcase oil separation under control, and the valvetrain doesn't allow overlap before TDC intake, they've probably taken the proper precautions to limit valve deposits normally associated with DI engines.
Last edited by arghx7; 10-24-2013 at 08:51 PM.
10-25-2013, 02:49 AM
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10-25-2013, 10:03 AM
#12
edit: Most other DI motors are subjected to being tuned more aggressively and increased boost.
now that this DI technology is in our arena it will take about five years to have the data to drive our community away from increasing cam size and overlap, but to add forced induction as the OEMs are doing...
Last edited by genv6.2gm; 10-25-2013 at 10:15 AM.
10-25-2013, 11:16 AM
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We will be pushing new data and prospective solutions here. I don't see any current DI motors that will have as many cam swaps like this one will.
edit: Most other DI motors are subjected to being tuned more aggressively and increased boost.
now that this DI technology is in our arena it will take about five years to have the data to drive our community away from increasing cam size and overlap, but to add forced induction as the OEMs are doing...
edit: Most other DI motors are subjected to being tuned more aggressively and increased boost.
now that this DI technology is in our arena it will take about five years to have the data to drive our community away from increasing cam size and overlap, but to add forced induction as the OEMs are doing...
10-25-2013, 02:21 PM
#14
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10-25-2013, 02:26 PM
#15
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I've posted about this in the Advanced section of a certain popular forum for LSx engines, but I'll repost some of that here with some additional detail.
To simplify, without port injectors washing and cooling the valves, the two things that cause the valve deposits are PCV-system crankcase vapors (from suspended oil droplets) and hot intake valves due to cam phasing. The newest generation DI engines have pretty elaborate air-oil separators from the factory that go through two or three stages of impactor plates, cyclonic separators, etc. So that helps a lot with PCV-related contributions to the buildup.
The other issue, which is often not fully understand, is EGR gases. It's obvious that gases from an external EGR valve can contribute to the problem. A lot of current production models don't have external EGR valves because they can get enough internal EGR for fuel economy and emissions by using cam phasing.
You know all those early Audi direct injected engines with valve deposit problems? Notice how they mostly had a single cam phaser on the intake side? The big issue is spitback of hot gases during valve overlap at part throttle. The solution to it is to stop opening the intake valve at the end of the exhaust stroke, while the piston is still rising. Newer DI engines are already doing this.
Here's some crappy MS Paint pics I made. First look at a sort of "textbook" valve timing diagram with made-up cam profiles having no overlap.
360 is TDC Intake, where the gas exchange occurs. Before 360 (looking to the left), the piston is rising at the end of the exhaust stroke. After 360 (looking to the right), the piston is moving downward on the intake stroke. Valve deposit-causing timing is below:
At cruising load, when pressure from exhaust gases in the chamber is higher than intake pressure, the hot gases spit out the intake valve. So now you have deposits of junk, especially soot (common on DI engines), and heat promoting adhesion of valve deposits. But what if I have an exhaust cam phaser and I want to try and avoid this spitback, like current Ford Ecoboost and Hyundai DI engines do?
We retard (or just park) the intake cam so that the intake valve opens after TDC, when the piston is falling. Then we retard the exhaust valve for internal EGR to improve fuel economy and emissions. Here's a published map of valve overlap position vs speed and load on a Ford Ecoboost 2.0 :
So how does this relate to the Gen V small block? I don't know the baseline cam specs off the top of my head, but with its simple cam phaser it can't dial in additional overlap like on a dual overhead cam engine. All the LT1 cam phaser can do is retard the intake valve opening and exhaust valve closing in equal increments, so the piston can't push hot exhaust gases back into the port. See below:
So in conclusion, if GM has the crankcase oil separation under control, and the valvetrain doesn't allow overlap before TDC intake, they've probably taken the proper precautions to limit valve deposits normally associated with DI engines.
To simplify, without port injectors washing and cooling the valves, the two things that cause the valve deposits are PCV-system crankcase vapors (from suspended oil droplets) and hot intake valves due to cam phasing. The newest generation DI engines have pretty elaborate air-oil separators from the factory that go through two or three stages of impactor plates, cyclonic separators, etc. So that helps a lot with PCV-related contributions to the buildup.
The other issue, which is often not fully understand, is EGR gases. It's obvious that gases from an external EGR valve can contribute to the problem. A lot of current production models don't have external EGR valves because they can get enough internal EGR for fuel economy and emissions by using cam phasing.
You know all those early Audi direct injected engines with valve deposit problems? Notice how they mostly had a single cam phaser on the intake side? The big issue is spitback of hot gases during valve overlap at part throttle. The solution to it is to stop opening the intake valve at the end of the exhaust stroke, while the piston is still rising. Newer DI engines are already doing this.
Here's some crappy MS Paint pics I made. First look at a sort of "textbook" valve timing diagram with made-up cam profiles having no overlap.
360 is TDC Intake, where the gas exchange occurs. Before 360 (looking to the left), the piston is rising at the end of the exhaust stroke. After 360 (looking to the right), the piston is moving downward on the intake stroke. Valve deposit-causing timing is below:
At cruising load, when pressure from exhaust gases in the chamber is higher than intake pressure, the hot gases spit out the intake valve. So now you have deposits of junk, especially soot (common on DI engines), and heat promoting adhesion of valve deposits. But what if I have an exhaust cam phaser and I want to try and avoid this spitback, like current Ford Ecoboost and Hyundai DI engines do?
We retard (or just park) the intake cam so that the intake valve opens after TDC, when the piston is falling. Then we retard the exhaust valve for internal EGR to improve fuel economy and emissions. Here's a published map of valve overlap position vs speed and load on a Ford Ecoboost 2.0 :
So how does this relate to the Gen V small block? I don't know the baseline cam specs off the top of my head, but with its simple cam phaser it can't dial in additional overlap like on a dual overhead cam engine. All the LT1 cam phaser can do is retard the intake valve opening and exhaust valve closing in equal increments, so the piston can't push hot exhaust gases back into the port. See below:
So in conclusion, if GM has the crankcase oil separation under control, and the valvetrain doesn't allow overlap before TDC intake, they've probably taken the proper precautions to limit valve deposits normally associated with DI engines.
Great Point! I guess only time will tell though.
10-25-2013, 03:30 PM
#16
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I saw a presentation from one of the powertrain engineers who claimed that in all of their durability studies they never ran into any carbon accumulation issues.
10-25-2013, 03:34 PM
#17
so with DI a singe solid cam is an advantage. then look for performance from displacement and lighter engine weight.
After personally moving from LSx platform to a smaller higher revving DOHC I will say its a great engine but it's not the cat's meow like everyone thinks DOHC is. and the mpgs are NOT better and off idle torque is not there. midrange torque and high end smoothness is better i will say.
After personally moving from LSx platform to a smaller higher revving DOHC I will say its a great engine but it's not the cat's meow like everyone thinks DOHC is. and the mpgs are NOT better and off idle torque is not there. midrange torque and high end smoothness is better i will say.
10-25-2013, 03:36 PM
#18
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so with DI a singe solid cam is an advantage. then look for performance from displacement and lighter engine weight.
After personally moving from LSx platform to a smaller higher revving DOHC I will say its a great engine but it's not the cat's meow like everyone thinks DOHC is. and the mpgs are NOT better and off idle torque is not there. midrange torque and high end smoothness is better i will say.
After personally moving from LSx platform to a smaller higher revving DOHC I will say its a great engine but it's not the cat's meow like everyone thinks DOHC is. and the mpgs are NOT better and off idle torque is not there. midrange torque and high end smoothness is better i will say.
10-25-2013, 03:41 PM
#19
im saying that after all the hoopla for the last 15 years from ppl about how the LSx is like a dinosaur not having DOHC, i moved to a 2014 performance DOHC V8 from a LSX and didn't see what all the fuss what about. i noticed NO improved MPGs.
This was incomparison to a larger LS engine. I think think the larger displacement pushrod isn't at a disadvantage, especially when cam phasing results in coking.
This was incomparison to a larger LS engine. I think think the larger displacement pushrod isn't at a disadvantage, especially when cam phasing results in coking.
10-25-2013, 03:44 PM
#20