Percentage of port injection and carbon build up
 

Most of the known and accredited professional mappers for our platform reduce the amount of port injection below 20-30% and this available only at high rpms, and I wonder, why no-one complains for carbon build up on valves and injectors while most refuse to use fuel/injector cleaners?
When I changed my intake hose with a silicone one I saw carbon deposits after the throttle butterfly, and as I think my millage went up slightly, I'll use before my next oil change some intake cleaner along with a good polyetheramine fuel/injector cleaner (35.000km car)
But it seems I am the exception, not the rule, have I miss something?

Correct most tuners especiaply on petrol and lower octane petrol will run less port injection than standard tune especially at high loads high rpm.


It likely not a big problem for deposits if you still running 30 or 40% port at lower rpm lower load where most driving is done and most deposits form.


Cars driven at high speeds and loads likely get less deposits anyway.




The 2017 and later cars ran avout 30% port at high spped/loads where the earlier cars ran zero to 20%. So there may have been a reason for that change but may have been emissions related.



The depisits or carbon you see in the throttke body are more likely due to OCV carankcase gasses or the EGR done via the strange values in the stock intake cam tables round 2000 rpm.



For that yoy likly need upper cylinder engine cleaner sprayed into intake as per subaru recomendation every 6 months.


Fuel additives might help with injectors in places where fuel quality is low.


I use the upper cylinder cleaner but i never get any noticable smoke out exhaust


however i do ise 30% port at high rpm and loads in my tune and im on ethanol E85 fuel which burns very clean (. 7 years no issues)

First time I've heard of that. Is this in the recommended services table? Do you have a reference for this?

For american fuel (both 93oct and E85) which are very good, i like to keep higher port% at high rpm too
because the engine will take higher ignition timing anyway because of the better fuel

For shittier euro fuel, for example our italian E5 100ron fuel which is much worse than 93oct us fuel i like to use a lot less port% and more DI

i also think like steve the soot you see it s mainly caused by EGR and intake reversion
it happens also to centrifugal supercharged car, if you keep high overlap on vacuum zones like it was NA

Wouldn’t a good catch can system eliminate all of this?

it s intake reversion, it comes back from the intake valves to manifold to intake hose when there is overlap and vacuum on intake

https://youtu.be/nof8DiSx0y8?t=2

My manual states clearly "Add injector cleaner every 15.000kms" and I am using "Mannol intake valve cleaner" which has similar composition with Subaru upper engine / top engine cleaner, and HKS DDR which is 100% hyper polyetheramine like (Japanese) "Subaru PEA carbon cleaner":


https://i.ibb.co/yRDFQVQ/test.jpg


https://cdn.snsimg.carview.co.jp/min...t=3710adf91c8b

I had my engine out at 70+ thousand miles and noticed no more intake buildup then any other engine :iono:

The throttle body is nowhere near the valves. the only way to get buildup is backfire or dirty oil back through the system.

see JIM s post above


here is the subaru product


https://parts.citysubaru.com.au/prod...-cleaner-sa459