[Tuner Boost]

Some tech info for the C7 Stingray owners. Most vette owners that have had a C5 or C6 know well the oil ingestion issues, but since GM has now gone DI with all it's engines, this becomes pretty serious as far as the care and feeding of the new C7.

The detonation and carbon deposits most probably already know about, so we will focus on the brand new issue of Direct injection.

Most can remember seeing the placards on a Shell/Mobil/Chevron fuel pump with the dirty and clean intake valves, well these are accurate and not just marketing. In the past, the detergent additives of the top tier fuels kept deposits from forming on intake valves as with the port injection engines the injectors kept a constant spray of fuel showering the valves so we never had to wory aoubt intake valve coking:

Direct injection has a ton of technical improvements over port injection such as allowing greater power to made from a higher compression ratio (11.5:1 vs 10.2:1 port injection) as the fuel is only introduced into the combustion chamber during the final 20-30% of the compression stroke, we no longer have as high of a probability of detonation (pre-ignition) from a hot spot like carbed or port injection. Also, since the pressure the fuel is delivered to the injector is 2,000-3,000 PSI atomization is far better and now fuel injectors never have a chance to build up deposits. This also results in better fuel economy, and more.

The one downside the industry did not anticipate is now since the fuel never touches the intake valves, the oil present in the PCV vapors bakes on to, or "Cokes" the intake valves resulting in a degradation in power and MPG in as little as 10-15k miles since no fuel ever touches the intake valves:

This results in buildup on the intake valves as shown here:

This is NOT a GM only issue, it affects every make/model of DI 4 stroke engine including motorcycles, outboards, and snowmobiles. Some more than others as you can see in this link of photos from techs all over the world:

https://www.google.com/search?q=int...oCA&ved=0CAcQ_AUoAQ&biw=1684&bih=816&dpr=0.95

GM has made great strides in the much improved baffles in both the valve covers and the valley cover where the crankcase dirty side is evacuated through, but there is still a ton of oil entering the intake air charge from 2 points.

One is the dirty side (foul) that is common in the past, the valley cover so a good catchcan will stop that, but the other is the same as the earlier C6 Z06 dry sump tank vent that burps oil into the intake air bridge before on the c6, and now into the baffles on the OEM air box with the C7.

Many may have seen the pictures Ron at Vengence posted elsewhere of the bag full of oil they found on the fiorst C7 in, and here is what we found on this brand new one (after the first 3 from Ron):

Here is a step by step pictorial of what we see, and how it is cured:

First, we are using the dual valve can with integrated flow controlling checkvalves mounted inline and the RX cleanside separator at the oil sump:

Lets look at where the oil ingests, and how the C7 engine 's PCV system works.

First, the filtered, MAF measured fresh air enters the drivers side valve cover via this main line from the airbox baffles:

Since this we will be correcting with a secondary suction/evac source preventing reversion, or back flow through this into the air box, we are leaving this line intact.

Then the passenger side valve cover has two fittings that join and vent through the drysump tank and also connect to the airbox. Then a line runs from the tank to the airbox. This is the problem one as it allows a path for any oil from the tank to "burp" directly into the airbox. So this is removed (note it has insulation on it):

We then replace the oil fill cap on the sump tank with the RX cleanside oil separator, and connect the enclosed line from the separator to the air box barb left open from removing the OEM line:

This now will trap the oil that does "burp" and hold it in the separator during the moments when the oil would exit (during hard cornering, braking, acceleration) and holds it from ingestion until the flow pulls it back in when in full vacuum mode (idle, deceleration, or cruising). So now we have the clean, or fresh side addressed, lets get to the real culprit of steady oil ingestion. This is the U shaped convoluted line that runs from the Intake manifold vacuum barb down to the valley cover barb just below. This is all new for 2014 and has a much improved baffle under the valley cover in an attempt to slow oil ingestion, and the exit barb it'self is now a one-way checkvalve VS the restrictive fixed orifice of the L99 and LS3 versions (that were too restrictive to allow proper evacuation). So props to GM for addressing part of this issue (we have used the checkvalves for 12 years now back with the C5 to correct this issue). So this helps reduce the backflow, or reversion during WOT, but does not eliminate it, and we will get to how we correct that as well.

So here is the foul side line (Note the vacuum barb now is on the drivers side of the IM snout VS the passenger side on the gen 3 &4 versions of the LS engine):

And the one way checkvalve valley cover barb where all the crankcase vapors along with the oil most and damaging combustion byproducts are evacuated:

By simply pressing the tabs, these lines will quick disconnect, and the barbs are 3/8" so the included lines with the RX system slide snugly on all.

Now we simply connect the center of the RX can to the valley barb (and since it already is a checkvalve, no additional valve need be installed here):

And the primary outlet of the RX can will now connect to the vacuum barb left open after removing the U shaped OEM tube, WITH a checkvalve flowing away from the can (this is to ensure no mixing and reversion)

And finally, the secondary outlet with checkvalve flowing away from the can will run to a hole drilled into the coupler just in from of the throttle body. This is going to provide suction for evacuation while in WOT operating mode when vacuum inside the IM is non existent from he reversion pulses present. This will now ensure the flow is always traveling in the right direction, and the checkvalve prevents any backflow.

The RX can will separate the oil and other compounds from the vapors and only cleansed vapors are entering the intake air charge preventing the intake valve coking as well as the other oil caused issues most are aware of.

Here is the entire system.

as it is finished:

 

[akpancake]

run a puke tank just like racecars do, only tie it into the pcv system. good idea.

 

[robertf97]

I want to buy this if it works with a supercharger, what is the deal? Give me a link. Thanks, Robert

 

[greggshere]

Does the valve deposit issue also affect standard oil pan cars or is it unique to the dry sump engines? I might have misunderstood, but I kept seeing reference to dry sump.

 

[mybluecorvette]

Does the valve deposit issue also affect standard oil pan cars or is it unique to the dry sump engines? I might have misunderstood, but I kept seeing reference to dry sump.

I would like to know also. If so where would it be connected on a standard car. Thanks


Sent from my iPad using Corvette Stingray Forum

 

[mjw930]

It's a problem with all DI engines but to what extent within the LT1 is an unknown simply because there aren't that many miles on them yet. My guess is it's less a problem with the none dry sump cars only by virtue of the lack of splash back or "burp" opportunity but we really don't know. Obviously they developed this using a Z51 with dry sump so it will be interesting to see if they develop a kit for non dry sump cars.

"Tuner Boost" needs to get back on line and participate in this thread. The longer he waits the more this looks like vendor SPAM.

 

[Crawler]

run a puke tank just like racecars do, only tie it into the pcv system. good idea.

You need to run a system that maintains the loop and includes check valves.

I want to buy this if it works with a supercharger, what is the deal? Give me a link. Thanks, Robert

You will need a different catch can for a forced induction setup. I'll gather some links and post them.

Does the valve deposit issue also affect standard oil pan cars or is it unique to the dry sump engines? I might have misunderstood, but I kept seeing reference to dry sump.

The valve deposit issue is on all Direct Injection engines that have proceeded the LT1. We haven't seen these engines running long enough. To know how they will act.

The issue is not in the oiling system of the car. Rather it has to do with the fact that modern engines run PCV systems that reroute gaseous oil back into the intake tract to be consumed by the engine. On a port fuel injected engine, the gasoline passing over the intake valve will help to keep them clean. Help, not cure. In a Direct Injection system there is no gasoline(hence no detergents) passing over the valves to aid in cleaning and cooling of the valve. This sludge forms as oil hits the valve and is coked on by the immense heat the valve sees.

It's a problem with all DI engines but to what extent within the LT1 is an unknown simply because there aren't that many miles on them yet. My guess is it's less a problem with the none dry sump cars only by virtue of the lack of splash back or "burp" opportunity but we really don't know. Obviously they developed this using a Z51 with dry sump so it will be interesting to see if they develop a kit for non dry sump cars.

"Tuner Boost" needs to get back on line and participate in this thread. The longer he waits the more this looks like vendor SPAM.

 

[Chip]

I've read that there is an issue with the dry sump motor, but mainly as a result of overfilling the oil system. I have also read that the info. in early owners manuals contained incorrect info. regarding proper oil levels.

 

[Tuner Boost]

Tracy is that you?

Yes...scotty? Looks like one of the TX supercar guys...

run a puke tank just like racecars do, only tie it into the pcv system. good idea.

Race engines we run belt driven vacuum pumps to not only evacuate constantly, but to also provide a bit more power as we run a low tension ring set and we try to maintain 14-15" of vacuum at all times. Some racers on a budget may run header collector evac systems that also work (if no mufflers are run) but if you just vent to a puke tank, then you every time the engine shuts down all the damaging combustion byproducts present condense and mix with the oil (water, unburnt fuel, abrasive carbon particles, sulfuric acid, etc.) and that greatly increases wear on the internal parts...when tearing down an engine that is just vented, we see the effects on the bearings and journals as the acid is attacking their surfaces (look like "worm tracks" or splotches, and fine pitting).

Here is a example of a LS race only engine that just had a breather cap on one side, and vented to a puke tank on the other. Note the corrosion already attacking the rocker arms, and the needle bearing retaining cup on the fulcrum is thin stamped steel and when it fails, these hardened bearings drop into the engine:

Most that do just a puke tank/breathers are only aware of the obvious, pressure and oil mist and not the rest of the compounds that it is critical they are evacuated while still in a suspended state. After they cool and condense, only part of the water and unburnt fuel is able to "flash off" again. Most becomes mixed/emulsified with the oil. Ont he street, most will want their investment to last long and care for it the best they can.

I want to buy this if it works with a supercharger, what is the deal? Give me a link. Thanks, Robert

Yes. The routing is slightly different with a top mount PD type blower, or a turbo/centrifugal blower it requires different routing as well. NA wet sump, NA dry sump, and different FI all have a flow and evacuation process that is slightly different. If anyone needs tech info on specifics, just ask and I can go into more detail.

NickJ just got me onto this site and were signing up as a supporting vendor now, so I can give links to purchase later. Going to ty and recruit some of our dealer network that are Corvette specific to join as well. Not sure if Colorado Speed is a vendor here, but they carry the systems.

Does the valve deposit issue also affect standard oil pan cars or is it unique to the dry sump engines? I might have misunderstood, but I kept seeing reference to dry sump.

It's a problem with all DI engines but to what extent within the LT1 is an unknown simply because there aren't that many miles on them yet. My guess is it's less a problem with the none dry sump cars only by virtue of the lack of splash back or "burp" opportunity but we really don't know. Obviously they developed this using a Z51 with dry sump so it will be interesting to see if they develop a kit for non dry sump cars.

"Tuner Boost" needs to get back on line and participate in this thread. The longer he waits the more this looks like vendor SPAM.

I would say your on the right track Mark, the dry sump has been an issue since the C6 Z06 was first released, then, and now, GM has issued a TSB on filling with less oil than the engineers designed the dry sump systems to hold to try and reduce the "burping". But, what we are seeing is (the one in yesterday as an example) had near zero in the airbox unlike most others we see. Now he had "drove it like he stole it" from day one and I would expect his rings seated far better than those that baby it the first 1000 or so mile (this is critical for proper ring seating as these come prefilled with synthetic oil and the friction protection makes ring seating in that critical short window of 400-500 miles before the cylinder walls glaze over very difficult). The ones we see that followed the break-in procedure in the owners manual seem to always have some oil consumption issues.

So, all of the oil in this one came from the standard place, the valley cover.

As for the coking, there have not been many miles on the LT1 engine yet, but years and millions of miles on DI engines as a group, and other than Audi and the turbo V8 that added small port injectors back in to help reduce the coking, but it has little effect. The ones we see the least coking on are the Turbo application that are experiencing a good amount of water ingestion during the cold weather (it condenses in the intercooler and then is pulled in as a liquid, not steam) so this seems to reduce the coking. But the downside is these same engines are occasionally experiencing hydrolock if a big "gulp" is ingested at once and then we all know what the pistons and rods look like.

Here are some pictures of GM engines with low miles on them and the intake valve buildup (yes, the LT1 seems to build this up as quickly as the 3.6" DI v6'S GM has in several platforms:

We can get into the intake ports with a boroscope or by removing the intake manifold to look at them, and anyone with 10-15k miles on one that is near, let me know and we will (at no cost) remove the IM and you can see on your car personally as well as take pictures to post here.

And after a manual cleaning (seafoam, etc only seem to loosen and remove some of the deposits):

Here is an example of what is caught in the cold weather (below 45* F):

And after a few days of letting it settle (winter cold will result in a good amount of water is always present)

So from the bottom up here is what was caught (the visible layers at least):

The first layer is water and sulfuric acid. Next is unburnt fuel and water mixed (still emulsified..let sit a week and it separates far better). Then we have a water/oil mix (emulsified) and last the oil alone that has settled to the top.

Other than a small amount of water, none of this is good entering the intake air charge.

Mark, sorry it took me overnight to get back on here...I don't have a computer at home.



And what a intercooler from a Maggie equipped car looks like at 15k miles as this oil bakes onto the intercooler insulating it and reducing it's ability to transfer heat as well as clooging the air flow through it as the fins become obstructed:

 

[2nd Stingray]

So are the fixes detailed below available from a supporting vendor on the forum?

 

[Tuner Boost]

We are as soon as Nick gets us up....give it a day and we should be listed.

I see Lashway and twentieth Century, both are on our dealer list, but show as inactive.

If you want to order today PM Nick to see if it is OK.

 

[Tuner Boost]

Cool. Your corral of cars is impressive.

What do you do for GM?

 

[Tuner Boost]

Never ran the TX mile, but have been in Professional drag racing for ages. Both NHRA & IHRA. Divisional, National, & World Championships (my drivers and myself) in multiple classes. GM implemented my PCV mod to the 3.6L DI engines mid-late 2013 increasing the fixed orifice size to prevent clogging and allow proper CFM of flow. Took app. 4 years for them to make the change, but corrected the issues.

 

[C7Driver]

Very interesting post. Lots to think about when my Stingray arrives. Thanks for posting.

 

[smajicek]

Posts like this scare the crap outta people that will be doing nothing but driving back and forth to work. I've see it all over the camaro boards for the v8. The question that never seems to get answered is , is it necessary for the DD driver that does not race, track or hover over our engines and look for every little nuance?

I had a drip can in my hands for my camaro and returned it to Apex after I thought long and hard about the DD questions above. I'll take my chances that GM has not made engines that will not work well for the warranty period and beyond.

I am with you Glen,
I am purchasing the 7/70k GM major guard for my DD when it arrives

 

[Tuner Boost]

This is necessary with every DI engine daily driver or hard driven. And it affects every manufacturer.

Do some search on industry discussions, SAE papers, and the pictures hundreds of techs that work on every make/model in the world.

GM,Ford, etc. will not halt sales and manufacturing for an issue like this....it would put any automaker out of business. They are all working on solutions, but to date there is none that can be maintenance free and still provide proper evacaution of the crankcases damaging combustion by-products. And all manufacturers deny it is an issue to date, but one only has to look for themselves to see. Here are some good reads:

What is Direct Injection and what are the advantages/disadvantages? | Car Match Blog

This includes the supercars:

COKING IN DIRECT INJECTION ENGINES? - FerrariChat.com

And DD's:

Direct Injection in Four Cylinder Engine - Drive Accord Honda Forums

The gooey truth about direct injection - Chicago Tribune

Direct injection and intake valves fouling? [Archive] - Bimmerfest - BMW Forums

Audi FSI Engine Carbon Build-up Megathread

Possible Mitigation Measures to Combat DI Intake Valve Deposits - Page 4

All have this issue, it is part of direct injection. And since GM dealers are among the biggest customers of these (Nickey Chev, etc.) never have we seen a warranty voided from the RX can...and that is over 12 years and over 14,000 in use.

So the issue is not GM related, it is Direct Injection related and the only way to prevent this to date, is a proper system retrofitted and then the can must be emptied every 5k or so miles to maintain the protection.

As with most any issues, out of sight, out of mind applies to this.

 

[glen e]

And again, if GM does not put it on thir cars std, I refuse to believe they would jeopardize
their WARRANY costs by forgoing it.

I know it is talked about it a lot, and I realize it is real. But how much is it a problem? Is it enuf to send newbies into hysterics here, IMO, ....NO....I was with BMW corporate for 24 years. But I have yet to see a mfr mount a catch can as std eqipmment. Is every mfr putting their head in the sand? I doubt it.

When they do, I will mount one.

 

[Tuner Boost]

And again, if GM does not put it on thir cars std, I refuse to believe they would jeopardize
their WARRANY costs by forgoing it.

I know it is talked about it a lot, and I realize it is real. But how much is it a problem? Is it enuf to send newbies into hysterics here, IMO, ....NO....I was with BMW corporate for 24 years. But I have yet to see a mfr mount a catch can as std eqipmment. Is every mfr putting their head in the sand? I doubt it.


They cannot implement any now without requiring the owner to do an additional maintenance step every 4-5k miles, and the conditioning of the market to a buyer that expects to put fuel in and never open the hood for 10k miles this wont work. The caught oil cannot be returned to the crankcase w/out also returning the concentrate of damaging combustion byproducts the PCV needs to constantly remove, and to make the current integrated baffles new for 2014 any better, they would also be trapping and retaining the damaging compounds.

If you were with BMW Corporate that long I would assume you have some engineering contacts still? Call one and ask. BMW has been battling this longer than most as they were pioneers in implementing DI.

In fact, a quick search on "BMW DI intake valve deposits" to find all the TSB's, etc. on how big of an issue it is.

And as far as from the factory, Maserati had them since the late 50's early 60's, but that was for eliminating detonation for power...DI has only been around for the last 10 years or so and the US is relatively new with 2014 being the first year for GM as far as the V8's. On the V6's and ecotech 4L's, we see the results up close and personal daily.

Your not far Glen, stop in and see all the engines/cylinder heads to see the progression of coking at different mileage, and take a few minutes to remove your airbox and TB and see how much oil is in yours.

Here is some reading on BMW for you. Many are referencing TSB's and factory service procedures for cleaning these deposits:

REVIEW: Cleaning of intake valves with BMW walnut shell blasting tool

Direct injection and intake valves fouling? [Archive] - Bimmerfest - BMW Forums

Mini Cooper Repair Services at MiniWorx

MISSFIRE from Carbon build-up around valves (PICTURES) - MINI Cooper Forum

When they do, I will mount one.

And as the car owner, you should only do what you are comfortable with. You made the investment, and you are the one that should decide. This is only for information for those that do want to avoid these issues. Just as the piston slap of the C5 and C6 vettes and the oil consumption issues were acceptable for many, this should be as well. (GM still released years of cars with those issues while knowing in great detail how wide spread it was).

This thread is not to convince anyone that is satisfied with the cars as they come. Same as with CAI systems, exhaust, headers, tunes, etc. adding any modification should only be considered by those that believe there are ways to improve and enhance performance, not those that believe the cars come the best they could possibly be when they arrive from the factory.

 

[glen e]

First, let me say I am not trying to portray you as spreading bad info. As I said, the problem is real, I warrantied a few when I was with them. Just not one that I think should be presented as a major problem that will have newbies scurrying for the lifeboats, like usually happens. Many talks with Chase at Apex about this.

I still teach for BMW and we mention the DI situation in every class. Dealers report seeing it, but not on such a widespread basis that the occasional warranty claim does not clear it up. It usually seen on cars driven low mileage, never above 3500 rpm...as in the "little old lady syndrome".

 

[greggshere]

This is necessary with every DI engine daily driver or hard driven. And it affects every manufacturer.

So do you have or are you going to market a similar kit for the standard (non dry sump) engines?