1.5 carbon build up?

[Marco1979]

Are you sure, Jocko? MPI has been used since 1990 or so and is not direct injection.
The picture you show is not the situation for Mk3 and Mk4 Jazzes. I believe it is like this:



More info here: https://learnmech.com/what-is-gasoline-direct-injection-gdi-working-operation/

[Jocko]

Honda'a MPI is stated as follows.

The PGM-FI system relies on a piezoelectric sensor to measure intake manifold air pressure, then combines that data with the crankshaft rpm and other info to compute the air quantity, and interprets the data using performance maps. Fuel is injected intermittently into the inlet ports. The PGM-FI also has a trailing throttle fuel cutoff and a self-diagnosis system.

These are Honda Jazz fuel injectors. As you can see they are low-pressure fittings for fitting into the inlet manifold. Injectors that fit into the cylinder are screw-fitting, like spark plugs.



Direct injection goes straight into the cylinder.

We are arguing different points here. DI is only on the 1.5 Jazz engine and the smaller engines use MPI.

[Jocko]

you are not going to clean anything with injector cleaner, its direct injection so in front of the intake valves and not behind cleaning them like on multi port injection

My apologies. I misunderstood this post. To me, in front of the intake valves means upstream, in the inlet manifold. In front, as in the direction of travel of the charge. I now realise monkeydave means in front as in the cylinder itself.
Please disregard my waffle in between these posts.

[Marco1979]

The mk3 has DI also for the 1.3 engine. Both 1.3 and 1.5 are Earth Dreams high compression (1:13.5) Atkinson-type engines that have direct injection. It has to be, otherwise Atkinson would not work properly (while the compression cycle starts, the intake valves remain open for a short while. Air is pushed back out, so less fuel can be added while having an optimal ratio between air and fuel. This is only done on low engine loads).

Mk1 and mk2 have have MPI on all versions.

Come to think of it: as 1.3 and 1.5 are very similar, but 1.3 is not sold in the US, the petrol type there as the cause for problems seems even more valid. If the US would have had the 1.3, it would have had similar problems.

PS: based on Wikipedia pages for Jazz / Fit and Honda engines

[jazzaro]

The mk3 has DI also for the 1.3 engine. Both 1.3 and 1.5 are Earth Dreams high compression (1:13.5) Atkinson-type engines that have direct injection. It has to be, otherwise Atkinson would not work properly (while the compression cycle starts, the intake valves remain open for a short while. Air is pushed back out, so less fuel can be added while having an optimal ratio between air and fuel. This is only done on low engine loads).


PS: based on Wikipedia pages for Jazz / Fit and Honda engines

Wiki is wrong.
1.3 Jazz (GK3) Earth dreams has port injection, 1.5 Jazz (GK5) has direct injection.
As far As I can remember, Honda has no 1.2 or 1.3 engines with Direct Injection.

[Marco1979]

Sorry Jocko for doubting your answer and thanks jazzaro for clarifying that Wikipedia is not always right!

[Bobcat]

So did we decide if injector cleaner on the 1.5 direct injection was useless or worth a bottle now and then? The conversation became a bit too technical for me!

[Jocko]

I would say yes. I used it about once a year, before my MOT, on my 2006 Jazz. It was multi-point injection.

[E27006]

I think the conclusion is the Honda DI engine has two sets fuel injectors, the primary system (DI) injects fuel into the cylinder and not through the inlet valve port,  the secondary  injection system is to the inlet port, the purpose is to spraywash and clean the inlet valve port of carbon build up.
Carbon build up, cheap fuel is to avoided!
Many years ago at a classic car show, I had a conversation with an owner of an old post war Morris, he  had rebuild his engine only to have to decoke severe carbon build up within a year of regular driving, he blamed  the carbon to discount grade supermarket fuel. He said no problems with premium fuel such as Texaco premium fuels.
Diesels cars, my brother had an Vauxhall Astra diesel, on supermarket discount fuel the vehicle struggled to pass the MoT smoke test,  if he used the vehicle on premium diesel fuel for several tanks before the MoT , the vehicle flew through the smoke test, I wish I had the Mot test printouts to give figures to my post.
Moral, you get what you pay for, cheap fuel is actually the expensive option, it causes problems

[jazzaro]

I think the conclusion is the Honda DI engine has two sets fuel injectors, the primary system (DI) injects fuel into the cylinder and not through the inlet valve port,  the secondary  injection system is to the inlet port, the purpose is to spraywash and clean the inlet valve port of carbon build up.

Some VW DI engines used this technical solution, both for valve cleaning and for better emission control. But this is an expensive way, good for a Ferrari engine, not for standard cars.
Motorists can also use a VVC (continuos valve phase variator) and proper fuel injection times to create a fuel spray backstream in inlet ports and wash the part where carbon buildups are more frequent.
More than low quality fuel, it's a low quality oil that can create buildups, especially oils with high NOACK and sulphates. Easily drivers who use to buy cheap fuel, use also to buy cheap oils and to not follow specified oil change intervals.

[TnTkr]

Honda Jazz GK5 (1,5 Dynamic, Sport or RS) has a direct injected L15B3 engine, which has one injector per cylinder located between the inlet valves and pointing downwards towards the pocket on the piston.

In the picture the injector itself is disassembled, but the hole is clearly visible.





It's been discussed previously in this forum, that good quality fuel or fuel injector cleaner of course helps keeping injectors clean, but it is also plausible that it helps keeping the intake valves clean because fuel mist may flush the intake valves when they are open.

[E27006]

Here is a link to a video by Diagnose Dan,  Dan is dealing with a VW Tsi DI petrol engine with a cold-start misfire problem. Dan is dealing with the issue of carbon build-up in the valve ports, good video for background knowledhe of DI engines:

this link is a shortcut to a camera probe and then follows a comparison of indirect / DI engines

[TnTkr]

Different engines have different problems. Honda L15B3 injector problems are typically not cold misfires. At least what can be found on user forums. Typical first symptom is the light show of various warning lights on dashboard.

[degzi]

Basically just do what it says in the handbook, change oil every 6 months and use a petrol additive / cleaner every year.

Can't go far wrong then.

[jazzaro]

6 MONTHS???