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What is it about the direct injection plus turbo setup that causes the intake to carbon up?
Why do DI motors carbon up?
- Thread starter LoneRanger
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Originally Posted By: LoneRanger
What is it about the direct injection plus turbo setup that causes the intake to carbon up?
I feel like this has been beaten to death on BITOG, but the gist is that the valves are not being washed over by fuel in a DI engine, so they accumulate deposits. There are various mitigation techniques out there that vary from one mfg to another to help address this, some more effective than others. And BTW, it's a DI issue, not a DI turbo issue.
What is it about the direct injection plus turbo setup that causes the intake to carbon up?
I feel like this has been beaten to death on BITOG, but the gist is that the valves are not being washed over by fuel in a DI engine, so they accumulate deposits. There are various mitigation techniques out there that vary from one mfg to another to help address this, some more effective than others. And BTW, it's a DI issue, not a DI turbo issue.
In most, even multiport injected engines, the intake gets carbon buildup anyways. It's because the crank case ventilation and EGR gases are passed through the intake port. That is also why the throttle body needs cleaning every once in a while.
The reason it's not an issue with multi port injected engines is because the injectors spray fuel on the intake valves as they open, so the valves are actively being washed by gasoline.
DI setups spray fuel directly into the combustion chamber, fuel never touches the intake valves.
The reason it's not an issue with multi port injected engines is because the injectors spray fuel on the intake valves as they open, so the valves are actively being washed by gasoline.
DI setups spray fuel directly into the combustion chamber, fuel never touches the intake valves.
Originally Posted By: LoneRanger
What is it about the direct injection plus turbo setup that causes the intake to carbon up?
I think it is somewhat simple (to me anyway). With DI, you never get the cleaning effect of PFI on the intake valves surfaces that are outside the combustion chamber in the intake ports. When you add in the PCV oily mess that (due to EPA) gets sucked back into the intake track and can coat these same surfaces, you get carbon build up over time. Some makes are much worse at this than others.
I find it interesting that some car makers are using both DI and PFI systems that are designed to work both separately and together at different engine load points. You get the best of both worlds in this case as far as power/mileage/emissions are concerned and keeps the intake valve surfaces cleaner. The downside is a more complex system with more component cost incurred. But the benefits can (and for some automakers do) outweigh the downside of this. This method also allow fuel treatments (like BG44K, Redline SI-1, etc.) to actually DO something about what remains on the valves. I would like that a lot!
Keep in mind that the benefits of DI for turbo engines is quite significant due to the cooling effect the fuel injection charge has and allows more power to be made with the same fuel volume.
What is it about the direct injection plus turbo setup that causes the intake to carbon up?
I think it is somewhat simple (to me anyway). With DI, you never get the cleaning effect of PFI on the intake valves surfaces that are outside the combustion chamber in the intake ports. When you add in the PCV oily mess that (due to EPA) gets sucked back into the intake track and can coat these same surfaces, you get carbon build up over time. Some makes are much worse at this than others.
I find it interesting that some car makers are using both DI and PFI systems that are designed to work both separately and together at different engine load points. You get the best of both worlds in this case as far as power/mileage/emissions are concerned and keeps the intake valve surfaces cleaner. The downside is a more complex system with more component cost incurred. But the benefits can (and for some automakers do) outweigh the downside of this. This method also allow fuel treatments (like BG44K, Redline SI-1, etc.) to actually DO something about what remains on the valves. I would like that a lot!
Keep in mind that the benefits of DI for turbo engines is quite significant due to the cooling effect the fuel injection charge has and allows more power to be made with the same fuel volume.
Originally Posted By: WhizkidTN
I find it interesting that some car makers are using both DI and PFI systems that are designed to work both separately and together at different engine load points. You get the best of both worlds in this case as far as power/mileage/emissions are concerned and keeps the intake valve surfaces cleaner. The downside is a more complex system with more component cost incurred. But the benefits can (and for some automakers do) outweigh the downside of this. This method also allow fuel treatments (like BG44K, Redline SI-1, etc.) to actually DO something about what remains on the valves. I would like that a lot!
Lexus/Toyota has been using dual injection since 2006. Pretty sure on the recent dual injected engines, they are using a cleaning cycle that runs periodically. Not sure how that cleaning cycle works.
I find it interesting that some car makers are using both DI and PFI systems that are designed to work both separately and together at different engine load points. You get the best of both worlds in this case as far as power/mileage/emissions are concerned and keeps the intake valve surfaces cleaner. The downside is a more complex system with more component cost incurred. But the benefits can (and for some automakers do) outweigh the downside of this. This method also allow fuel treatments (like BG44K, Redline SI-1, etc.) to actually DO something about what remains on the valves. I would like that a lot!
Lexus/Toyota has been using dual injection since 2006. Pretty sure on the recent dual injected engines, they are using a cleaning cycle that runs periodically. Not sure how that cleaning cycle works.
It is not a DI + Turbo issue. Simply a DI issue with only some engines. The experience with a few early DI engines (I believe it is VW/Audi that comes to mind) indicated there were some potential issues. Later engines don't seem to be exhibiting nearly the issues seen with the early adopters, but the issues in the early adopters live on as "truth" for every engine that follows after.
The mechanism is exactly as indicated in posts above. Without fuel washing over the valves, carbon sometimes can deposit on the intake valves.
The introduction of a port injector into some of these systems is very much not solely due to concern with intake valve carbon. Read up on soot particle emissions on DI engines, and how a port injector can assist with that if you'd like to see whats driving the inclusion of the additional injector. The reality is many of these engines actually emit more small soot particles than diesel engines...
The mechanism is exactly as indicated in posts above. Without fuel washing over the valves, carbon sometimes can deposit on the intake valves.
The introduction of a port injector into some of these systems is very much not solely due to concern with intake valve carbon. Read up on soot particle emissions on DI engines, and how a port injector can assist with that if you'd like to see whats driving the inclusion of the additional injector. The reality is many of these engines actually emit more small soot particles than diesel engines...
My Coworkers Colorado V6 has a coal black tail pipe . I told him a couple week after he bought the truck I though he had a lambda sensor issue. Now we know. If the things are MORE efficient I don't see how uncombusted carbon is getting everywhere. That should be CO2 gas with some CO.
NOT soot.
Appears the learning cure is steeper than anticipated and we are but 1/2 way up the asymptote
NOT soot.
Appears the learning cure is steeper than anticipated and we are but 1/2 way up the asymptote
It is possible for a new technology to be more "efficient" at one thing while creating other issues.
Such is the case with DI engines. They are more efficient in terms of getting better fuel mileage (ie: being more fuel efficient), but it does it with the expense of some unintended consequences.
Such is the case with DI engines. They are more efficient in terms of getting better fuel mileage (ie: being more fuel efficient), but it does it with the expense of some unintended consequences.
I see this topic pop up in automotive forums all the time and wonder the same thing myself. Diesel motors never spray fuel on their intake valves, and I've never heard of any unusual or excessive service to clean carbon deposits from them... in the meantime I think these discussions have promoted the sale of lots of "catch cans" and a new recommended service of pulling the manifold to clean valves. I do suspect there is something here I don't understand because of the fact Toyota found it wise to keep the dual MP and DI systems on a few models. I keep reading these posts now that I own a DI Chevy truck with 37K miles on it just to see if there is a problem on the horizon - but I'm pretty confident so far they have engineered a better engine than the last generation.
DI benefits outweigh the negatives imo. Raising compression ratio, increase power and fuel efficiency, emissions...
My Camaro has DI and I guess we shall see how it goes, so I may have to pull the intake and clean the valves once every 100k miles not that big a deal imo.
My Camaro has DI and I guess we shall see how it goes, so I may have to pull the intake and clean the valves once every 100k miles not that big a deal imo.
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Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Car and Driver
I wish Subaru would've gone with Toyota's D4S system which is on the FRS/BRZ and utilizes direct and port injection. Those cars do not have a problem with intake valve deposits and the uoa's show little or no fuel dilution.
This VW patent is good reading and has been discussed in many threads here in the past (which you can find with a google search):
https://www.google.com/patents/US6866031
Some old discussions:
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3179370/1
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1325647
This VW patent is good reading and has been discussed in many threads here in the past (which you can find with a google search):
https://www.google.com/patents/US6866031
Some old discussions:
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3179370/1
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1325647
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Originally Posted By: MNgopher
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Trying to figure out which Audi 3.0 engine has both DI and PI. AFAIK, the one in wife's 2015 Q5 does not.
I know some of VAG's newer 1.8T and 2.0T engines utilize this though.
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Trying to figure out which Audi 3.0 engine has both DI and PI. AFAIK, the one in wife's 2015 Q5 does not.
I know some of VAG's newer 1.8T and 2.0T engines utilize this though.
One of our techs had the intake manifold off on a brand new, not even delivered to a customer, 2017 F150 with a 3.5L EB that has both port and direct injection. There was a faulty rail pressure sensor. Ford mounts both the high and low pressure rail pressure sensors next to eachother. Anyway the tech found out that if you start the truck without the intake manifold on it will run. He thought it was kinda cool actually. Obviously you can't rev it, but it was one of those "o wow that's cool" moments.
Originally Posted By: Quattro Pete
Originally Posted By: MNgopher
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Trying to figure out which Audi 3.0 engine has both DI and PI. AFAIK, the one in wife's 2015 Q5 does not.
I know some of VAG's newer 1.8T and 2.0T engines utilize this though.
I don't think the newer 2.0T TSI engines do.
I know the new Audi 3.0 TFSI engines do have dual injection. I'm looking at the 2017 A6 3.0T and it has it. I'm wondering if the A8 does as well...eyeing both cars.
Can you confirm or deny the 2.0 TFSI now has both too?
Originally Posted By: MNgopher
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Trying to figure out which Audi 3.0 engine has both DI and PI. AFAIK, the one in wife's 2015 Q5 does not.
I know some of VAG's newer 1.8T and 2.0T engines utilize this though.
I don't think the newer 2.0T TSI engines do.
I know the new Audi 3.0 TFSI engines do have dual injection. I'm looking at the 2017 A6 3.0T and it has it. I'm wondering if the A8 does as well...eyeing both cars.
Can you confirm or deny the 2.0 TFSI now has both too?
Quote:
Can you confirm or deny the 2.0 TFSI now has both too?
I've read somewhere that it does in some markets, but I don't think North America is one of these markets.
As far as the 3.0 engine, check out this list of vehicles using the same part number which is a low pressure injector valve...
http://www.realoem.me/search/tvn/06E906031
Can you confirm or deny the 2.0 TFSI now has both too?
I've read somewhere that it does in some markets, but I don't think North America is one of these markets.
As far as the 3.0 engine, check out this list of vehicles using the same part number which is a low pressure injector valve...
http://www.realoem.me/search/tvn/06E906031
Originally Posted By: MNgopher
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Very nice article, despite its brevity...thanks very much for sharing!
I was so excited when I read an article in a Subaru mag that mentioned that the 2.0l in the BRZ had the combined injection system, as I assumed that the 2.0l turbo in my FXT would use the same technology. I really wish it did...
Conveniently enough, Car and Driver just published a quick article on the new trend for both DI and PI.
Car and Driver
Very nice article, despite its brevity...thanks very much for sharing!
I was so excited when I read an article in a Subaru mag that mentioned that the 2.0l in the BRZ had the combined injection system, as I assumed that the 2.0l turbo in my FXT would use the same technology. I really wish it did...
Originally Posted By: Quattro Pete
Quote:
Can you confirm or deny the 2.0 TFSI now has both too?
I've read somewhere that it does in some markets, but I don't think North America is one of these markets.
As far as the 3.0 engine, check out this list of vehicles using the same part number which is a low pressure injector valve...
http://www.realoem.me/search/tvn/06E906031
Wow, thanks! Based on this then, I guess an Audi A8 is in fact something I can buy
Money notwithstanding of course LOL.
Quote:
Can you confirm or deny the 2.0 TFSI now has both too?
I've read somewhere that it does in some markets, but I don't think North America is one of these markets.
As far as the 3.0 engine, check out this list of vehicles using the same part number which is a low pressure injector valve...
http://www.realoem.me/search/tvn/06E906031
Wow, thanks! Based on this then, I guess an Audi A8 is in fact something I can buy
Money notwithstanding of course LOL.
Originally Posted By: superangrypenguin
Can you confirm or deny the 2.0 TFSI now has both too?
Based on what I was able to find out on audi forums, current version of 2.0 tfsi in North America has one single port injector for the whole engine, not one injector per cylinder like the 3.0T.
Can you confirm or deny the 2.0 TFSI now has both too?
Based on what I was able to find out on audi forums, current version of 2.0 tfsi in North America has one single port injector for the whole engine, not one injector per cylinder like the 3.0T.
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