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Why timing chains stretch, part 2

how it works, stretched timing chains

In part 1 we discussed the difference between a timing belt and timing chain. This week we’re touching on why timing chains stretch.

Fuel injection modernization

A modern development in engines on how gasoline gets into the engine- Direct Injection, or Gasoline direct injection (GDI).

Cars, since the dawn of time have been inducing the fuel into the engine from wherever the air came in- whether that is a carburetor or fuel injection- the air and fuel mixed and landed on top of the intake valve.

A carburetor or fuel injected engine (the term fuel injection which fuel is injected into the intake manifold vs being essentially sucked out of a carburetor) has what’s called a “wet intake” meaning; fuel goes through the intake manifold on its way down to the intake valve.

GDI has the fuel injector inside the engine’s combustion area and fuel is directly injected inside the cylinder. These engines have “dry intakes”- only air goes through them.

GDI has great benefits- More power, better fuel efficiency, and less emissions.

GDI downfalls

So again, what’s this got to do with timing chains?

In my opinion- it’s got a lot to do with them. Direct injection has been used in some way or another since as early as 1925. It became mainstream in the late 90’s and early 2000’s.

My first experience with it was in 2003 with BMW’s 760 V12, which was their first engine with this technology. One of the issues we ran into were misfires (check engine lights) because of carbon deposits being formed on the intake valves.

And here we are with one of the issues with GDI.

Do you recall the last time you were filling up with gas at the gas station, and looked at the ads they have? Brand X gasoline vs (insert whatever gasoline station you’re at) “our” gasoline- usually it was a dirty valve vs a clean valve, like this:

dirty valve vs clean valve

Unintended Issues

Abrasive soot formed from the GDI design.

GDI soot is a phenomenon that was discovered after cars were produced, and millions of miles had been logged on vehicles…. complaints and issues started to show up.

And now we’re at the stage of “what does GDI have to do with timing chains?”

This soot is abrasive, and not something that happens in port injected or carbureted engines. The soot gets into the engine from the combustion process + blowby, and starts mixing with the engine oil.

One of the jobs of engine oil is lubrication, but also takes contaminants to the oil filter to be cleaned out- and as a result gets into the timing chain. The soot wears the metal links in the timing chain and causes it to get longer- and that’s how we get to “how fuel injection makes my timing chain longer”

We’ll keep going on future articles because there are a few other things related to timing chain stretch!

Alex Noll

CEO – ABR Houston
832-797-9114 8498 Miller Road, The Woodlands Texas 77354

Welcome to ABR Houston, the leading European auto repair shop in The Woodlands. With over a decade of experience and a proven history of serving over 10,000 satisfied customers, we have recently relocated our shop to The Woodlands to better serve our valued clients. Our commitment to exceptional service and expertise remains our priority. From routine maintenance to intricate repairs, our dedicated team is determined to keep you confidently on the road. Trust in the experience and reliability of ABR Houston, where customer satisfaction drives our passion for excellence. Your Local Experts for AudiBMWMiniRolls-Royce & Volkswagen Service In The Woodlands.

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