jcthorne

Because they require emptying

SUB VETTE

I guess cost is the only reason. It seems pretty much a no brainer to me that the more oil that is kept out of the intake the less carbon problem you're going to have. Every time I empty my catch can I'm sure glad what I pour out didn't go through my intake.

grcor

For cars with dry sump oil systems, I would like to see the function of a catch can incorporate into the top part of the external oil tank. The captured oil could then simple drain into the bottom of the storage tank. No need to manually drain the captured oil.

FYREANT

Ford actually has some type of catch can built into the valve covers that drain back into the motor. Pretty smart actually..

lt4obsesses

I thought the LT1 has a similar set up.


http://gmauthority.com/blog/gm/gm-engines/lt1/

FYREANT

Yea I read that before too. Funny though that on my Mustang I didn't need a catch can. Perhaps Chevy needs to "borrow the design" lolz

wjnjr

Translation:

"We're not aware of increased carbon buildup on the intake valves due to DI causing a significant and/or noticeable decrease of performance during the (now shortened) warranty period"

Gary '09 C6

^ yeah, that's what I was thinking as well...not the best answer, IMO.

Gary '09 C6

USCG

Has anyone used a borescope or inspection camera to assess the valves, or is pulling the intake manifold the only option? Does the camera give an adequate view to see the coking?

lt4obsesses

Fyreant has some pics
https://www.corvetteforum.com/forums...his-out-2.html

See post #36. I would say from those pics that there is reasonable cause for concern.

rpmextra

I have no experience whatsoever with meth injection kits, but sounds like a little dose of it here and there could really benefit a DI engine.

FYREANT

yep. Spot on. I'll bet you can figure out why I am working on installing meth this week actually.. lol

rpmextra

great, a clean engine is a happy one. Amongst other benefits

jcthorne

Your mustang does not have a DI fuel system either.

FYREANT

Fuel system has nothing to do with PCV operation. Just the cleanup of what the PCV system leaves behind on the valves.

COSPEED

Easy enough to look at the valves up close and see first hand, then no PR BS to sort through. It only takes 10 minutes to remove the IM and see for yourself. I guess this set of dyno runs showing the power degradation over time (look close, this owner did a dyno starting at app 30k miles and every year for 3 years at app the same time and weather conditons, and then had a crushed walnut shell media cleaning performed...look at his last dyno after the coking was removed from his valves):



And We are all imagining this?



And this was also imagined? There is not a single automaker that admits the extent of how serious this issue is, yet every single one is bending over backwards for a OEM soultion:

https://www.google.com/search?q=Inta...w=1600&bih=775

And, this was staged? Look close at how the deposits are wearing the valve guides as they are cycled up in from the stem.

Here is a close up:



This is very real, and anyone that has a LT1 or LT4 w/out a proper air/oil separation system installed I urge to do a base line dyno, then every 6 months go back to same dyno, same correction factor, and document what you see and report back here. I know this will take time, but well worth it to sort through and see who is telling it straight.

COSPEED

The benefits of DI as he expressed are many, and allow greater power and efficiency form smaller displacement engines. a 11.3-11.5:1 CR is not uncommon, and the incidence of detonation has been greatly reduced as the fuel is only present for milliseconds as the fuel is not introduced until that final 10% or so of the compression stroke, so unlike a port inj engine that brings it in as soon as the intake stroke starts and detonation is far more common, so we are never going to see a backward move to PI again as the CAFE fuel economy standards can really only be met through DI. The issue with intake valve coking (and I will add, do NOT use a seafoam, BG, CRC solvent based upper induction cleaning as the damage to the catalytic converters when these big chunks come loose, and bent valves when it gets stuck between the valve and seat and PTV contact occurs as well as the best scenario where most gets expelled out the exhaust port and the smaller hard particles are forced between the piston and cylinder wall causing scouring (any engine rebuilders can verify this on DI engines). These are fine with older port injection engines where little to no valve coking occurs and it only loosens the small soft carbon deposits, but NOT for DI no matter what they advertise (imagine how THEY are panicking as the in gas tank additives are now worthless and their business is based upon these additives. Same with top tier gasoline brands. Was critical w/port injection and now has little to no effect over cheap brands now).

Any wanting ANY technical info on DI vs PI and the issues, down to injector PSI, etc., just ask. I am happy to share. This is my expertise as a career, I am not involved in sales, only tech support, so ask any tech questions to get a good understanding on all things DI and how to avoid the issues plaguing the industry and enjoy a long life with the most awesome car the big 3 has ever put out!

Nate@VanBortelChevy

I don't see anything wrong with Tadge's response. People need to remember he plays a very political role, read between the lines to find the truth. Tadge isn't hiding anything in his response, you have to give him credit for that. What I gathered is: Yes, with SIDI you will have carbon build up. However, the amount is much less than most other SIDI engines and it will not have an effect on how the engine performs during its expected life cycle.

Will some people have a problem with carbon build up? I am sure they will, but they will probably also use a low-quality fuel and are heavy on the throttle.

lt4obsesses

I understand exactly what you are describing in terms of the dangers of using a top end cleaner to remove carbon deposits. Makes perfect sense.

Now, and kind of what I was getting at in an earlier post, what about their use as a preventative measure? Wouldn't it be feasible to have this listed on regular maintenance protocol, say at regular oil change intervals? Assuming this done with every oil change from new, not after the actual coking has already happened? The key being "preventative" and not "Corrective".

It just seems that the manufacturer's need to address this reality as it is. That it is indeed a fact of life with the SIDI engine, which, with it's many benefits, is and should be here to stay. However, until a better method of oil separation is developed (as the EPA emission standards are not going away either), shouldn't the manufacturer's then help the owner's with a recommended plan to reduce this negative side effect? Not just simply say, "our testing showed no effect for the expected lifetime"? Thus increasing that "expected lifetime".