silver_tt

Thank you very much for the response. You work on engines every day and I only read white papers about them so I always appreciate the opinion of experience (the best way to learn engines is to work on them). But talking Nikisil and excess fuel, I would think DFI engines would be even more vulnerable to this since a bad injector or leaky injector is spraying it directly onto the cylinder wall vs a pre-DFI engine where it's further upstream.... leaking injector is bad news in either type of injection, port injected or direct injected, not disputing that, just seems especially bad with DFI and those injectors shoot at much higher pressures. I hypothesize this is why with a port injected Mezger that has Nikasil cylinders you will never see a case of bore scoring under normal circumstances (you can correct me if that's not accurate, I used to own one and bore scoring is pretty much completely unheard of on a 996/7 Mezger that I have ever seen).

I would be infinitely grateful if you could share your SUMEbore results in the future.

pdxmotorhead

Nearly every marque out there with DI ,,, is/has/or will have problems..
1. Carbon buildup on the valves
2. Cylinder wall damage when the DI injector fails, remember some of these put 2000 psi on the fuel when they trigger, so they fail much harder than the old ones.
3. on almost all the small displacement high power motors you need a intake off valve and runner clean about every 60K.. ) Eco Tec, Eco-boost, VW's motors, audi..

silver_tt

Agree that DI has issues/considerations as a technology that are not brand specific and owners should be cognizant of all the things you stated. IMHO the thing most people in the turbocharged DI market are going to need to be paying attention to is soot formation which includes damage of timing chains/tensioners, etc. You can help yourself out here by running a "good" oil. I use Driven DI line because it has a low volatization and I make it a top priority to monitor and maintain AOS/PCV/crankcase vacuum with a manometer and preemptive replacement.

The reason I'm thinking about this is because after the market calms down I will buy another car at some point but only one with Nikasil or SUMEbore cylinders and want to be informed. SUMEbore is probably the most exciting technology I have seen in this space in recent memory.

This may be a stupid question but has Nikasil been used with a GDI engine? Nickies started out as air cooled and obviously made it to water cooled engines before it was phased out. If I am not mistaken Porsche implemented direct injection in the 997.2 but the last Mezger TT, for example, died at 997.1 -- as the 997.2 TT is a drastically different engine including the switch to Alusil. I believe the last Mezger was the 2011-2012 997 Porsche 911 GT3 RS 4.0 but I'm assuming it's still not direct injected? What I'm landing on is it seems like a 997.1 Mezger, which is not GDI, is still the most bulletproof engine you can buy even today over 10 years later. Someone can correct me if I'm wrong or have missed anything, only looking for the best/most accurate information. Thank you.

turkis_tii

@Quaz (OP): Hartech (Baz) has documents in detail how (he hypothesises) bore scoring occurs, I.e., it’s not related to fuel injectors but to the geometry of the pistons and piston skirts relative to the crank. He provides a lot of data, as opposed to anecdote, so it makes a lot of sense. Easiest solution would be to send injectors to an injector shop such as Witchdoctor and ask them to run the leak-down test “hot”. They would be able to validate Jake’s theory with real data. FWIW, I’ve had injectors cleaned and blueprinted from a 150K-mile BMW and a 100K-mile Spec Miata with only very slight improvement in flow rates (I.e., not significantly dirty), and no (cold?) leak-down; they do look for that.

Flat6 Innovations

I have over 300 sets of "real data" from injectors that were tested/ cleaned. Over and over again the cylinders that were scored had injectors that were leaking down, or had poor spray patterns, or both.
I have seen people build engines after bore scoring, and not change injectors, only to have the replacement engine suffer immediate cylinder issues during or just after break in. In 3 cases the new factory engine consumed oil immediately and did so on the exact same cylinder that the old engine previously scored. The installers swapped ancillaries and never even removed the injectors, so this was an absolute conclusive set of data that proved my theory better than anything.

No single thing causes bore scoring, it is a sum of many things that play into the scenario. Cylinder surface finish is one of those things, but if you have solvent (fuel) washing the protective layer of oil from the bores it will always be a catalyst.

The reason you didn't see any big differences after injector servicing is because the injectors had mechanical wear, and will never be as good as a replacement with a new injector. "Rebuilding" injectors means cleaning, and changing external O rings. Due to the methods that injectors are manufactured you can't disassemble them to replace the items that see mechanical wear. You throw them away.
The issue has never been injectors being dirty, in fact the trait is the modern fuels lack lubricity that help to reduce the mechanical wear.

All my engines get new injectors, not rebuilt, and not cleaned. It's not even an option.

dougn

So the injector leaks after you shut the engine off and fuel dribbles down and makes its way into the cylinder? How much fuel do you think or what would it take?

Flat6 Innovations

Yes.. That's one way they create issues. This is responsible for a lot of the "blue smoke" at start up, since the fuel wicks oil from thew ring pack into the cylinder, and appears to "burn oil" at start up.

Fuel has the same effect on oil, as paint thinner has on paint.

I have caught fuel puddling inside intake ports from this exact issue, and also found that fuel pressure was not being held at engine shutdown. This has been creating hot re- start issues with these cars in summer months for years.

Long story short, you never want liquid fuel in your cylinders/ intake ports.

dougn

Will good injectors hold fuel pressure till the next start up? Seems like a gauge on the fuel pressure may be a good idea so one may be alerted early

dougn

On another note, I have always noticed all my Porsches have had "slow" throttle response. It bugs me when I'm trying to rev match on downshifts. Why don't these cars have a quick rev pick up off idle?

Flat6 Innovations

The fuel pump (and pressure regulator on mk1 996s) will determine some of this as well. Fuel pressure should be maintained for a hot re- start.

Put simply, if you have a 996, the car has seen enough time in service to require new injectors.
Not rebuilt.
Not cleaned.
Time in service dictates this, not mileage. This is based on my empirical data, and replacement of fuel pumps, and the corrugated tubing inside the fuel tank isn't far behind the injectors. You can ask @dporto about that experience.

Flat6 Innovations

Sounds like you have "e-gas" cars with electronic throttles.

silver_tt

When the fuel is injected into the system it has to be atomized/vaporized to combust. There are different modes of injector failure that can all have the same end result -- eg. If it doesn't leak after the engine is shutoff it can also spray improperly such that the result is the fuel not being completely atomized and all the things Jake says about the effects of fuel on oil. This is one of the reasons I pay attention to my fuel dilution and also periodically measure my fuel trims.

Flat6 Innovations

I pay attention to the color of the oil when draining. Aside from the data from a UOA, I can tell everything I need to know from how the oil feels on my fingers, how it smells, and the color.

silver_tt

Agree on all accounts. I pay attention to basically everything about the oil both when it goes in and comes out.....and I take notes (consumption measurement, etc). On several occasions when mentioning this over the years on forums (one the reasons I had to take a break) I have been mocked by people saying literally I'm a complete fool and I think I can do real science by just looking at oil. I never said all oils were the same or that I was going to try to send a rocket ship to the moon on the back of using that data....but these people that laughed at me and think I'm stupid for saying that clearly are the type that have never changed their own oil otherwise they would have some clue what I'm talking about if they had any sense.

dougn

I had a 964 that I incredibly stupidly sold.....that I installed a RS flywheel on to try and improve the throttle response. I monkey ed with the barn door and a few eproms from a well known mostly 3.2 tuner (you're probably cringing LOL). nothing helped. otherwise, the car ran great I thought. It put out 248 HP on a dynojet 248. There's was a delay between a blip and a reaction It was stock internally. . also has a 2000 boxster s and a 06 cayman s that had delays