New Gen 5 GM V8

[Gaz64]

I'll take my Holden hat off that I've worn all my mechanic working life, now 34 years.

AFM (formally known as DOD - displacement on demand) is a great theory and does work well UNTIL an AFM lifter rotates in the poorly designed lifter guide.

And it will happen, seen a few failures.

Then it is heads off and camshaft change.

Each to their own about petrol direct injection, but the new Gen 5 is the next step forward (or back in some eyes) for emissions.
The hard fact is proof in pudding. The inlet valves are more prone to carbon buildup with no fuel sprayed at them.
To have high flowing cylinder heads ex factory that carbon up and lower potential airflow into the cylinder is backwards step.
Current port EFI engines can stay almost as new on high quality PULP.

[Aussie Mike]

Originally Posted by Gaz64

The inlet valves are more prone to carbon buildup no fuel sprayed at them.

Is this what you have seen from the SIDI V6 motor?

How does the carbon build up on the valve? Is it blown back out of the chamber as the inlet valve opens?

I wonder if a water injection system would help. It's a side effect I've seen turbo motors with water injection that they have clean combustion chambers when pulled down.

Carbon buildup is a problem on direct injection diesels more because of the EGR systems used which recirculate exhaust gasses into the intake for a 2nd burn. I pulled the whole setup off my land rover diesel when I did a VNT turbo conversion. It was really gunked up in there.

Cheers

[Gaz64]

Originally Posted by Aussie Mike

Is this what you have seen from the SIDI V6 motor?

How does the carbon build up on the valve? Is it blown back out of the chamber as the inlet valve opens?

I wonder if a water injection system would help. It's a side effect I've seen turbo motors with water injection that they have clean combustion chambers when pulled down.

Carbon buildup is a problem on direct injection diesels more because of the EGR systems used which recirculate exhaust gasses into the intake for a 2nd burn. I pulled the whole setup off my land rover diesel when I did a VNT turbo conversion. It was really gunked up in there.

Cheers

Mike,


Of the SIDI motors I've had the intake off, the reason is to ascertain the cause of pinging and oil consumption.

The majority of these have the buildup, I've yet to see a "good one", certainly haven't seen anything as good as my own cars.

The carbon on the back of the inlet valves is blowby engine oil from the rocker cover/inlet manifold combo.
Poor ventilation system design. Could also be valve guide lubrication past the guide seal.

One of my cars runs AEM water injection and 98 PULP. The inlet manifold and inlet ports are spotless.