This post looks at carbon build-up in petrol cars with a direct-injection (GDI) engine. If your car has started to idle roughly, hesitate when pulling away or feel down on power, carbon deposits on the intake valves are a common cause. A fuel additive poured into the tank cannot remove these deposits. A workshop service that cleans the air intake side of the engine can. In Singapore, we supply BG Products to our partner workshops that carry out this service.
What is a GDI engine?
In an older port-injection engine, petrol is sprayed just behind the intake valves, so it washes over them every time the engine runs. A gasoline direct-injection engine sprays fuel straight into the cylinder instead. This improves efficiency, which is why many modern petrol engines use it, particularly small turbocharged ones. Your owner’s manual or workshop can confirm whether your car has one.
Why do the intake valves get dirty?
As petrol no longer flows past the intake valves, nothing cleans them. Over time, fine dirt from the intake air and oily vapour from the crankcase ventilation system bake onto the backs of the valves. BG Products states this clearly: “once carbon accumulates on the backs of GDI intake valves, there is no pour-in-the-tank product that will remove these deposits” (BG Products).
Short trips and stop-start traffic give the engine fewer chances to run hot for long periods. As such, if you mostly do short urban journeys, it is important to look out for the symptoms below.
Signs of carbon build-up
- The engine idles roughly or shakes, especially when it is cold.
- The car hesitates or stumbles when you accelerate.
- The engine misfires, sometimes with a check-engine light.
- Power and response drop off gradually.
These symptoms can have other causes. The workshop should diagnose the car first before recommending any service.
How BG cleans it: the GDI Fuel/Air Induction Service
Based on BG Products’ information, the approach for GDI engines has two parts (source):
- Cleaning. The workshop uses BG’s injection equipment to feed BG GDI Air Intake and Valve Cleaner (PN 260) through the air intake, so it reaches the valves directly. BG Fuel Injection & Combustion Chamber Cleaner (PN 201) is used together with it for the fuel side.
- Prevention. After the cleaning, BG recommends products that slow down new deposits. These are BG Platinum 44K Fuel System Cleaner (PN 208), which BG formulates for both “lean-burn GDI and PFI” engines, as well as BG EPR (PN 109) engine flush and BG Advanced Formula MOA (PN 115) oil supplement at oil changes.
The service is carried out by a trained technician. It is not a DIY product.
How often?
We suggest you ask your workshop to inspect the engine at regular servicing and to follow BG’s recommended service intervals for your engine. Using 44K as a preventive treatment between services should help keep the fuel system clean.
Where to get it in Singapore
Oilmax is the exclusive distributor of BG Products for Singapore and Johor, and we supply partner workshops across the island. You can find a BG workshop near you. If you run a workshop and would like to offer BG services, please contact Oilmax.
FAQ
Can a fuel additive remove carbon from GDI intake valves?
No. In a GDI engine, fuel never reaches the backs of the intake valves. As such, the cleaner has to be fed through the air intake by a workshop.
Is my car a GDI engine?
Many recent petrol cars use GDI, particularly turbocharged ones. Please check the owner’s manual or ask your workshop.
Does BG 44K work in GDI engines?
Yes. BG states that Platinum 44K is designed for both GDI and port-injected petrol engines.
Where can I get a BG GDI service in Singapore?
At our partner workshops. Please see the locations page.
Sources: BG Products, “GDI Solved!”; BG Platinum 44K product page.