jvp

Original question is here.

vettman96

Sir:

I thank you very much for the concise reply, and also for engineering "one kick a** automobile".

FYREANT

So, it does seem that they are actually aware of the concern, but feel that it is of no consequence in relation to power degradation. I'm inclined to not agree with that, but, I'm not the engineer of this car now am I lol.

The part where he says "Of course, appreciation of that characteristic is limited to those who disassemble their engines. Most customers are unaware."

And also where he says "we did extensive testing to make sure there were no customer-observable penalties is GM basically saying "you got no business looking in there anyway"

lt4obsesses

Well, anyone that knows anything about engines knows that at some point, this carbon build up will affect performance. At some point the build up would have to hinder valve function. Which of course would lead to wearing of valve seals. There would also be a loss of, or at least disruption in the designed airflow into the chamber. Then, if this carbon flakes off, it gets into the chamber, into the oiling system and all that goes with that. The question is, at what point, and how can it be minimized without disassembling the engine?

Crossed Flags Fan

"At what point, and how can it be minimized without disassembling the engine?"

"the 200,000 mile in-vehicle long term testing. We have not seen anything unusual and zero performance degradation".

Taking Tadge at his word (and at this point not having any reason not to) I think we're good for 200K.... When the first owner surpasses that, or if problems are reported by owners before that, we'll know better by then.

Nithros

I'm not an engineer either but, based on what he said, I would answer your question as "No". I don't think you can take those two quotes out of context and make 1 + 1 = 3. On your first quote, he is saying most customers will never know nor appreciate how clean the valves are because they will never take their engines apart and see them. On your second quote, he is saying that you as a customer should not experience (observe) any decrease in performance.

FYREANT

I dont think those quotes are really out of context honestly. But even taking everything that was said at face value, let's face it, this is a known problem in the industry for all DI motors and they know it. The answer was simply put as the benefits of DI outweigh the shortfalls.

Bill Dearborn

I don't see where that conclusion fits with what he was saying. No customer observable penalties applies equally to people who disassemble the heads and see some build up. Just because there is a visible buildup doesn't mean there are any penalties due to that buildup.

Bill

FYREANT

There are other auto mfg's out there who are dealing with this same thing, and are have massive problems with it. I believe BMW was one of them. This is a known concern across all DI platforms. I am not certain what type of performance testing may have been done for this though. I think it would be prudent testing to take one of these cars that has not had a catch can installed, and run it on the dyno every 10-20K (assuming same conditions) and see if the power diminishes. "Customer observable" is the key term here. If the car does indeed lose horse power due to the build up on the valves, and its only a small percentage, then the typical "customer" may not "observe" a difference or problem. because the car would be gradually losing power over a measurable period of time, it's safe to say to the customer would not see a performance degradation as they drive the car on a regular basis and the diminished power is happening at a slow enough rate they won't notice. Take that same customer at 100k or 200k miles, clean their valves to make them like new, and I assure you they will confirm the car feels noticeably different.

Millenium 04

With direct injected engines there is no fuel coming across the intake valves to wash the carbon away. At 40-75K miles you will need a media blast on the intake valves to remove the buildup.

Some people use Seafoam to try to keep the coking under control.

lt4obsesses

Which was kind of my point. Why not GM make using a liquid top end cleaner part of the the regular maintenance schedule, say as part of the oil change procedure? Seems like it would be a lot better than waiting for it to get bad enough to require walnut blasting. However, he did say they did a 200k mile test, What we don't know is what the valves looked like.

jcthorne

Seafoam and other additives have absolutely no effect on the valve carbon build up problem as they never get near the valves.

lt4obsesses

Used as a top end cleaner, it is sprayed, poured via vacuum tube, or otherwise injected into the air intake manifold. It follows the same path the air does, thus reaching the back of the valves.

FYREANT

Correct. This is spot on. Essentially works the same way spraying Meth does, which also cleans the valves.

bluestinger66

Did someone say "meth"?

froggy47

Millenium 04

Bingo

///ADMAN

Eh. I'm not liking the answer(s) either.

It's less about "Yes, there is a problem and it is happening."
And, more a "Don't worry about it. You won't notice it." approach.

In other words:

You can smoke and still do the things you like. If you never get a chest xray, you'll never see any buildup.
Sure, maybe at some point, the build up will cause a problem and eventually diminish your performance.
But, that's unlikely. The smokers we tested said they felt fine. Year after year. Mile after mile. No problems at all.

Clairvoyantwolf

No, it's more like, "Continue smoking, you won't have any problems till you're 80 years old. We have not tested after that."

whl3

Catch cans are not some new and innovative technological miracle! I installed them on two previous supercharged DI engines some years ago. If they seem to be the remedy to what the manufacturers recognize as being an issue, why don't they put them on as standard equipment as a relatively simple and cost effective solution?