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I am in the car purchasing mode but not happy with the changes in engine technology. I'm not happy about the turbo trend but I could live with that. What I really dont like is the direct injection. From what I've read, the engines tend to develop carbon build up on the intake valves and there is no way to remove it. Then the owner is stuck replacing the heads. Have I got the story about right?
Stupid question here, but I have a good audience. Is direct-injection, by design, NECESSARILY an interference engine?
I feel like we're nearing the peak of efficiency for gas engines already, having managed tighter tolerances and adding computer-managed emissions systems. I think that a lot of proposed (and already-implemented) designs have some sort of Achilles' heel or another, requiring additional regular maintenance, whether to clean or replace some item or another. An air filter is no problem. Something requiring the valve cover (or head, don't get me started) to be removed means $$$ at a shop.
I might stand alone in this thread, but you won't be able to convince me to buy a vehicle with a timing belt over a tested design with a timing chain. $900-1000 every 70,000 miles may not amortize to much, but it's $900-1000 more than required from a timing chain, a design that can run 500k+ between replacements.
Any time a car's reliability comes into question, there's a guy who says "with REGULAR and PROPER maintenance..." no. Full stop. Some schedules are ridiculous in their scope and ridiculously expensive. My new metric for reliability is time between service intervals and ability to withstand neglected maintenance. What most consumers will inevitably do at some point or another.
- With synthetic oil, there's no reason any vehicle cannot go 10k between changes, across the board
- There is no reason that brakes, let alone rotors, need to be changed at 30k (ahem, Land Rover)
- After an initial, early transmission fluid change, the next one should be about 100k out.
I am in the car purchasing mode but not happy with the changes in engine technology. I'm not happy about the turbo trend but I could live with that. What I really dont like is the direct injection. From what I've read, the engines tend to develop carbon build up on the intake valves and there is no way to remove it. Then the owner is stuck replacing the heads. Have I got the story about right?
For a direct injection engine you can install a catch can (oil separator).
They catch all the stuff from the blowby hose and stop it from going into the intake, which builds up carbon on the valves.
I havent installed one on my hemi yet, because Im still trying to find out if it is dual ported, or direct injection. I dont want to install one, but I cant find the cons to catch cans besides emptying it.
If youre buying a car with DI new and youre worried about buildup on the valves, you should definitely consider it. Just dont cheap out on it. Good ones cost at least $100.
Stupid question here, but I have a good audience. Is direct-injection, by design, NECESSARILY an interference engine?
I am not certain, but I don't see any reason you could not build a direct-injection engine that is not interference.
That said many, maybe most new cars anymore are interference designs, to hit the power and mileage goals that customers are asking for. What I am getting at is maybe there is little point in building a non-interference engine with direct injection.
As an aside, I have several cars with timing belts, but all of them are older, non-interference designs. So they are quite tolerant of me not changing the TB on a strict schedule. A broken timing belt out on the road means AAA is going to tow me home, where I can replace the belt with little more trouble than if I had done it "on time".
I am in the car purchasing mode but not happy with the changes in engine technology. I'm not happy about the turbo trend but I could live with that. What I really dont like is the direct injection. From what I've read, the engines tend to develop carbon build up on the intake valves and there is no way to remove it. Then the owner is stuck replacing the heads. Have I got the story about right?
I had a 2015 CX5. Put 106K miles on it and traded it for a 2019 turbo CX5. It never had any engine troubles at all of any nature. Timing chain only. Never owned a car with a belt. Screw that.
*I rarely if ever ran top tier gas in it, did run 87 from small stations or wherever was cheapest, and never did any engine/oil/cleaning type mess.
Stupid question here, but I have a good audience. Is direct-injection, by design, NECESSARILY an interference engine?
Its not required that DI have an interference design.
It's just injecting a controlled quantity of gas into the cylinder rather than inducting a mix through the intake valve.
That's about the only thing different (of course the whole system leads to high pressure fuel pumps, fuel rails, and one ot more injector per cylinder).
Imho, cars are just getting too complicated, and overly expensive to fix. The govt claims they are saving the environment, but the improvements are miniscule. They are making it too hard for young folks and poor to get by.
Any new engine design is going to consider the DI carbon problem from 10 to 12 years ago. No automobile manufacturer is going to let a new design that turns into a block of carbon out into the field. This is like CVT where a round of early bad designs headlined by JAYCO made the technology suspect. My car has a CVT. I wouldn’t worry a lot about a new DI turbo engine design since it’s going to undergo massive scrutiny to make sure it doesn’t have the problem. “Common wisdom” tends to point at problems from 10 to 15 years ago that have been resolved. Any car where the fleet doesn’t reliably go 125,000 to 150,000 miles without expensive problems is going to crush sales for years and launch expensive class action suits.
Any new engine design is going to consider the DI carbon problem from 10 to 12 years ago. No automobile manufacturer is going to let a new design that turns into a block of carbon out into the field. This is like CVT where a round of early bad designs headlined by JAYCO made the technology suspect. My car has a CVT. I wouldn’t worry a lot about a new DI turbo engine design since it’s going to undergo massive scrutiny to make sure it doesn’t have the problem. “Common wisdom” tends to point at problems from 10 to 15 years ago that have been resolved. Any car where the fleet doesn’t reliably go 125,000 to 150,000 miles without expensive problems is going to crush sales for years and launch expensive class action suits.
There are plenty of current DI vehicles that will need walnut blasting to remove carbon deposits every 40k or so. Especially those with short commutes. Just not because of a breakdown/reliability. Just because the owners will notice decreased mpg and performance.
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