Mazda, DI engines without PI, and carbon deposits...

[Ws6]

I've been very pleased with my cx5s perfomance, but one thing that Inhave wondered about, is has mazda actually engineered the issue of carbon in DI engines away? I have 54k miles on my turbo cx5 and it is as solid, quick, efficient, and maybe even more so than when it was new. Car and Driver recently completed their 40k mile turbo cx5 test, and the results are in. At least within 40k miles, performance only gets better. This, compared to many other DI turbo designs that get slower and have build up issues without walnut blasting, etc.

Similarly, the near identical engined cx9 also saw a performance bump by the 40k mile mark, providing another datapoint.

 

[Mr.cant-find-his-10.5-mm]

I remember seeing something about cylinder head been hotter compare to other engines to burn off/reduce the carbon deposit. I could be wrong.

 

[Ws6]

I remember seeing something about cylinder head been hotter compare to other engines to burn off/reduce the carbon deposit. I could be wrong.

This is correct. It's just nice to see theory being borne out in reality.

 

[Blinker]

Mazda claims to have solved the carbon buildup issue by designing engines that allow for the intake valves to run hotter. They studied the issue and they came to the conclusion that if the intake valves don’t get hot enough they can carbon up.

 

[drtyler]

Photos of the valves after 60k miles would be a real data point. Seen any?

 

[Ws6]

Photos of the valves after 60k miles would be a real data point. Seen any?

...would it though? Who cares how it looks, so long as the efficiency and power is unaffected? Two schools of thought, that. I approach it functionally. If it's filthy but is not impacting anything, then it can be filthy for all I care. My LS1 was like that. Intake full of oil, literally, ran like a scalded dog to 150K miles when I sold it.

 

[MCompact]

...would it though? Who cares how it looks, so long as the efficiency and power is unaffected? Two schools of thought, that. I approach it functionally. If it's filthy but is not impacting anything, then it can be filthy for all I care. My LS1 was like that. Intake full of oil, literally, ran like a scalded dog to 150K miles when I sold it.

The performance of my 2007 MS3 never degraded over the 158,000 miles and 8 years I owned it.

 

[MRC01]

Mazda claims to have solved the carbon buildup issue by designing engines that allow for the intake valves to run hotter. They studied the issue and they came to the conclusion that if the intake valves don’t get hot enough they can carbon up.

Yes, and the Skyactiv engines also have an oil/air separator in the PCV line, which can help reduce intake gunking up.

Because Mazda's approach is based on part on running the intake valves hotter, it seems one should actually drive in a way that lets them get hot. Avoid short runs with engine cold, once the engine reaches operating temp, rev it up, give it the Italian tune-up, a redline a day keeps the carbon away.

 

[Deamos]

Yes, and the Skyactiv engines also have an oil/air separator in the PCV line, which can help reduce intake gunking up.

Because Mazda's approach is based on part on running the intake valves hotter, it seems one should actually drive in a way that lets them get hot. Avoid short runs with engine cold, once the engine reaches operating temp, rev it up, give it the Italian tune-up, a redline a day keeps the carbon away.

Good thing Mazda seems to build engines that are rev happy. Or at least the 2.5 in my CX5 seems to be. Maybe that's my heavy right foot though and that spiffy "sport mode" switch.

 

[MRC01]

... Maybe that's my heavy right foot though and that spiffy "sport mode" switch.

The best "sport mode" switch is the manual stick shift

 

[buster]

They are great engines. So is the AT they make. Due for an update, but completely bulletproof.

 

[spasm3]

I like the 2.5, mine is not a turbo. But i have to wonder how the made the turbo engine and only got 50 more hp out of it.

The non turbo makes what, 189?

 

[RooflessVW]

I like the 2.5, mine is not a turbo. But i have to wonder how the made the turbo engine and only got 50 more hp out of it.

The non turbo makes what, 189?

Look at torque.

 

[spasm3]

Look at torque.

Gotcha, i do see the torque went from 190 to 310. Thats pretty good.

 

[buster]

320lb on premium I believe. Power delivery is linear with no noticeable turbo lag from what I've read. I'm going to test drive one soon.

 

[Ws6]

320lb on premium I believe. Power delivery is linear with no noticeable turbo lag from what I've read. I'm going to test drive one soon.

It feels like my old LT1 above about 1500rpm.

 

[PimTac]

Look at torque.

Yep and that torque kicks in at very low RPMs.

 

[dudemancool1904]

Can’t speak for the new turbo engines but this is a well documented and well photographed issue for the DISI engines (2.3 liter turbo in the Mazdaspeed 3, 6, and CX-7). I just had my valves cleaned at 150k and they were nasty. More importantly I had the injectors cleaned and flow benched which showed some serious clogging. The biggest issue by far with performance these engines faced is stuck oil rings.

 

[buster]

Can’t speak for the new turbo engines but this is a well documented and well photographed issue for the DISI engines (2.3 liter turbo in the Mazdaspeed 3, 6, and CX-7). I just had my valves cleaned at 150k and they were nasty. More importantly I had the injectors cleaned and flow benched which showed some serious clogging. The biggest issue by far with performance these engines faced is stuck oil rings.

The Skyactiv engines don't suffer from this issue.