Walnuts GDI

I personally believe that the only reason to buy a new car and take the big hit is if I plan to keep the car a very long time and want a clean history. My newest car is a 2007. Here is my question: is the direct injection problem big enough so that I should avoid this in all cars?


Seafoam has a product formulated for cleaning the valves on GDI engines.


Agree with @Tester No, proper maintenance with the correct product can pretty much eliminate any issues with GDI. The benefits are pretty big.

However, if you still have concerns, look for vehicles that use TWO injectors per cylinder…one intake manifold injector and one direct, to eliminate the problem. Toyota and Ford do this on some engines. Not sure who else.


1 application of top end cleaner will remove 90% of carbon deposits on Valves? Why is intake removal required to clean valves? When chemical does same job?

What benefits, exactly? I seem to recall that cars from the 1990s-2000s were much more reliable, lasted for many more years than newer models are capable of, and were much more forgiving in terms of maintenance requirements. How often do we get posts from people experiencing VVT problems, carboned-up intake valves, premature timing chain/guide failure, high oil consumption, and a plethora of other problems which simply did not happen on older cars–even at much higher miles?

I am not sure where you would be getting your data that says newer cars need more maintenance. This website would give a very biased view. Consumer Reports might have data for the comparison. I personally do not want that comparison. I want the comparison between only well-maintained cars. I do know that CR says the annual maintenance costs of a 10 year-old car are surprisingly low…on average.

I agree. Toyota and Honda quality was so much better than other brands that they forced the other manufacturers to improve their quality or continue to lose market share. The leader’s quality got event better over time as other caught up, and the moving target forced even better quality from all manufacturers. About 10 years ago, CR said that their much worse than average category had 4% or worse defect rate among all vehicles in their subscriber fleet. That is worlds better that 1970s British Leyland automobiles with quality so bad that owners routinely did a top end job at 5000 miles from new. Better designs and tighter manufacturing tolerances are a never ending cycle for car builders.

My 1985 Accord got 100hp from it’s 1.9L engine.
It had fuel injection, but no VVT.
My 2017 Tucson gets 164hp from its 2.0L engine.
It has GDI, VVT, and gets equal gas mileage in spite of weighing 800lb more.


Why is the title of your post “Wanuts GDI” . . . ?

Did you read that walnut shells are used to clean the carbon buildup off of the valves

Funny you have walnuts in the title but apparently didn’t actually mention them


That can be used without removing the head?

Walnut shells won’t harm the engine, BMW has been using walnut shell blasting for more than 20 years. Below is the vacuum adaptor, there is a hole in the middle to insert the blaster.


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Engines are more efficient the higher the compression ratio they have. Back in the old days, 11:1 to 12:1 compression ratios required high octane leaded fuel. Higher octane than available today with our unleaded gas.

Direct injection allows compression ratios on the order of 13:1 even with regular fuel. That allows the engine to produce more power and better MPGs at the same time because the direct injection of the fuel cools the mixture thus preventing knock.

Because the injector is so quick and operates at such high pressure, it can open and close several times each intake cycle creating what is known as a stratified charge. An initial injection right before the plug ignites the mix and a second or 3rd burst of fuel to end up with a leaner air/fuel mix than would normally be optimal. That can control emissions and further improve fuel economy.

Direct injection isn’t new. Diesels have always been direct injected with mechanical systems. Mercedes directed injected a gas engine in their 300 SL Gullwing in 1955. Electronics just allows so much more capability.

I think you recall incorrectly. They weren’t. Just looking at the average age of cars on the road during that time compared to today disproves that.

In some sense they were more forgiving. They didn’t have tiny oil passages to clog for the VVT controls. But people still believed you needed 3000 mile oil changes and it was in their normal routine to change every 4 months. If they forgot, 5-6000 miles was still OK.

A LOT… because people are treating cars more like refrigerators. If it starts, it must be OK. They can’t remember to change their oil because 10,000 miles is too long to remember for today’s short-attention-span car owner even if the dealer will do it for FREE!

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While emitting only a tiny fraction of pollutants.

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… and requiring less maintenance.

No timing belt every 60,000 miles.
Plugs 100k vs 30k.
No valve clearance every 30k (I kinda miss doing that :disappointed:).
Coolant every 5yr instead of 2-3.

And I could say the same thing about my 85 Accord vs my 76 Chevy Nova.

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Generational improvement in engines and other automotive systems has been ongoing–despite some folks saying that they crave the cars from 20, or 30, or 40 years ago.

add safety improvement to the list too

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