Sometimes that which may perceived as a step forward in design may lead to unforeseen problems and indeed be a step , or two , backwards . Many petrol fueled vehicles available now use a GDI engine (Gasoline Direct Injection ) This has been adopted by auto mobile manufacturers replacing the more familiar MPI (Multipoint Fuel injection ) system .
Older drivers may remember the expression "valve grind or head and valve de-coaking " The adoption of fuel injection and better quality fuel and lubricants virtually made these procedures a thing of the past .
Most vehicles 20 -25 years ago required a service interval of 12,0000K or 12 months . Honda at on stage went to 15,000K and 18 months . Proved a disaster as some motorists never dipped their oil and seized their motors .
Around 2004-5 various manufacturers started looking at if the common rail diesel injection system could be adapted for petrol motors .The diesel common rail injector system divided truck operators at the time . I remember the controversy and arguments between the pro and con factions regarding it . The jury is still out in some quarters . That’s another story .
Ok enough of the preamble . The GDI motor has one inherent fault . It injects the atomised fuel underneath the intake valves whereas the MPI motors injector is mounted above the intake valve .
In a nutshell then the MPI motor cleans your intake valves on every induction stroke . Petrol dissolves any oil or carbon deposits on the back of the valve . The GDI motor on the other hand injects the atomised petrol beneath the intake valve thereby negating any cleaning properties the petrol may have and leading to carbon and other build ups on the back of the valve .
This is where more regular servicing comes in . The car manufacturers found that changing the oil more frequently , every 6 months , helped retard but not eliminate the build up . They were relying on the cleaning properties of , especially , synthetic oil .
I have a car with a GDI Turbo Engine . It is a Suzuki Baleno GLX . The servicing schedule runs as follows . 6 month services capped at $175 for three services then the fourth service costs $475 .
When I had the fourth or $475 service done I asked two things . Why so dear ? Why did you have to have the car all day . The car had done 14,000 K’s . I was told they had to adjust the valves on the fourth service . At 14,000 K’s a valve adjustment . I know them very well at the dealership and started to laugh .
It was an intake valve clean . They probably needed the car all day as once the the valve cleaner , there are quite a few on the market ,CRC GDI is a popular one . the car has to wait a given period of time for the cleaner to work on the carbon deposits and other grunge . Unless you know what you are doing do not attempt to use any off the shelf cleaners yourself as you will void your warranty . Some mechanics will offer , at a price , to fit a bleed off can to the engine which virtually eliminates the build up on the valves and also keeps your Turbo charger clean if fitted . Be careful as the manufacturer will most likely void your warranty .
It is no surprise that the correlation of shorter service intervals goes hand in hand with the adoption of the GDI motor by various motor vehicle manufacturers . My dealer will still not openly admit that GDI motor is basically a flawed design but they also sell Toyotas at the dealership .
It is strange Toyota have developed and are fitting a new engine to some of their Lexus line up with a second injector added on each cylinder . You guessed it . Above the intake valves . They acknowledged the problem with GDI motors .Daimler- Benz have developed a similar engine .
Why was the GDI motor so widely accepted by the motor industry . Economics . It is cheaper to produce than the MPI equivalents
I’ll put a c ouple of links below to a Suzuki Dual Jet MPI motor and a Suzuki Booster jet GDI motor animation .Look carefully at the induction stroke and you will see that GDI intake valves are not cleaned by the fuel on on induction as the injector is below them…
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