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TOV Forums > Strictly Technical > > Re: Why Carbon fouling may not be an issue for Honda DI engines

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silverf16
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Why Carbon fouling may not be an issue for Honda DI engines    (Score: 1, Normal) 08-12-2017 03:31
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This technical report states the use of split injection as a method to reduce carbon build up on intake valves.

Section 4.2.3 in the report below describes the process of split injections. The graphs in this section shows the injection events. I gathered that injection is occurring twice per engine cycle - First, injecting at 90 degrees after TDC, when the intake valves are open. It then injects again at BDC at 180 degrees during the beginning of the compression stroke. Honda doesn't spell it out exactly but study the graph.

By injecting when the intake valves are open, fuel is cleaning the backside of the valves. The injector is located between both intake valves hence it will hit both valves. Whether the spray pattern from the 6-port injector will hit the ENTIRE back surface of the intake valves is an unknown. But we know the first injection is effectively cleaning at least some portion of the valve hence reducing carbon build up.

Granted, the graph and text indicate that split injection increases fuel efficiency by 1% and reduces soot production because it has a more homogeneous mixture with a more stable air/fuel ratio.

This report is for the the 2.4 Naturally aspirated engine. Draw your own conclusion on how this strategy may also benefit Turbo engines.

I understand most of the report, but not all of it. If you are an engine person, you may uncover additional details that you can elaborate for us.

There you have it - One of Honda's strategy for reducing carbon build up.

https://hondakarma.com/data/attachment-files/2015/09/89991_Honda_2.4_L_Direct-Injection_Gasoline_Engine.pdf

notyper
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Re: Why Carbon fouling may not be an issue for Honda DI engines    (Score: 1, Normal) 08-12-2017 04:34
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Most DI engine makers use a split injection scheme, at least at lower rpms and loads (up to about 3000 rpm or so). Some use more than 2 injection events as well (although not as many as the diesel folk do).

At higher rpms and loads there really isn't the time for split injection.

SC

Nick GravesX
Profile for Nick GravesX
Re: Why Carbon fouling may not be an issue for Honda DI engines    (Score: 1, Normal) 08-12-2017 05:43
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I was aware of Inlet Gas Recirculation, but I'd forgotten about it!

 
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