paddlenbike
11-08-2012, 09:25 AM
I posted in another thread about our hunt for a new car and I described the significant number of problems people are having with carbon build up on these new direct injection engines. The car forums are literally lighting up with problems from virtually every manufacturer. The problem is so widespread that we decided to buy a car that uses port injection rather than direct injection so we don't have to deal with having the valves walnut shell blasted every 30,000 miles.
Here is what the valves on a new Audi look like at 19,000 miles.
http://i390.photobucket.com/albums/oo344/rAudiguy/DSCN3439.jpg
http://i390.photobucket.com/albums/oo344/rAudiguy/DSCN3441.jpg
The Audis and BMWs have the biggest problems on their hands, but probably because they started using DI a year or two before everyone else. It's interesting to note that the 2.5L V6 in the Lexus IS250 (a direct injection engine) is experiencing severe carbon build-ups like everyone else. (Lexus extended the warranty on these cars and is offering free top engine cleans to address the problem.) However the same car is also available with a 3.5L V6 (the IS350) that uses two injectors per cylinder--one is direct injection and the other is standard port injection. These cars are *not* experiencing the typical direct injected carbon build up and all the forums keep pointing at the Lexus 2GR-FSE engine design as the solution to the problem.
"The 2GR-FSE employs what may be described as "hybrid direct-injection, port-injection strategy," the only known such system among volume production engines in the "emission control zone," according to Shizuo Abe, Toyota's product General Manager. He cites a sample operating condition at 1200 rpm with a 60% load ratio: with direct-injection alone, fuel tends to form in lumps due to heavier fuel volume and slow piston speed, lengthening combustion duration, and thus limiting torque output. On the other hand, port-injection alone would not necessarily be better. Adding 30 to 40% direct-injection to port-injection accelerates gas flow, significantly improves torque output. Injection ratio between the two injectors is continuously varied?for example 30 to 40% in a specific parameter, and increased to 50 to 60% in another zone?optimizing the mix and distribution. Ultimately in high-rpm zone, 100-percent direct-injection is used to obtain higher torque." Toyota has 300 patents on this system.
It appears that fuel flowing around the valves is necessary to prevent the carbon build up. I'm really happy we found a new car without direct injection, but it looks like Toyota was the first to implement a way to prevent the problem. It will be interesting to see if the other auto manufacturers do the same.
Here is what the valves on a new Audi look like at 19,000 miles.
http://i390.photobucket.com/albums/oo344/rAudiguy/DSCN3439.jpg
http://i390.photobucket.com/albums/oo344/rAudiguy/DSCN3441.jpg
The Audis and BMWs have the biggest problems on their hands, but probably because they started using DI a year or two before everyone else. It's interesting to note that the 2.5L V6 in the Lexus IS250 (a direct injection engine) is experiencing severe carbon build-ups like everyone else. (Lexus extended the warranty on these cars and is offering free top engine cleans to address the problem.) However the same car is also available with a 3.5L V6 (the IS350) that uses two injectors per cylinder--one is direct injection and the other is standard port injection. These cars are *not* experiencing the typical direct injected carbon build up and all the forums keep pointing at the Lexus 2GR-FSE engine design as the solution to the problem.
"The 2GR-FSE employs what may be described as "hybrid direct-injection, port-injection strategy," the only known such system among volume production engines in the "emission control zone," according to Shizuo Abe, Toyota's product General Manager. He cites a sample operating condition at 1200 rpm with a 60% load ratio: with direct-injection alone, fuel tends to form in lumps due to heavier fuel volume and slow piston speed, lengthening combustion duration, and thus limiting torque output. On the other hand, port-injection alone would not necessarily be better. Adding 30 to 40% direct-injection to port-injection accelerates gas flow, significantly improves torque output. Injection ratio between the two injectors is continuously varied?for example 30 to 40% in a specific parameter, and increased to 50 to 60% in another zone?optimizing the mix and distribution. Ultimately in high-rpm zone, 100-percent direct-injection is used to obtain higher torque." Toyota has 300 patents on this system.
It appears that fuel flowing around the valves is necessary to prevent the carbon build up. I'm really happy we found a new car without direct injection, but it looks like Toyota was the first to implement a way to prevent the problem. It will be interesting to see if the other auto manufacturers do the same.