Carbon - why in some areas, and not in others (wink)

[oldeskewltoy]

What has happened here?

Why are some areas not carboned over??


The red arrows are pointing to areas in the head that have not built up carbon. The blue arrows are pointing to areas where the carbon has been laid down.

Here is a more uniform view of where the carbon is... and isn't


The red arrows are pointing to the areas where no carbon has been laid down, the blue arrows are pointing to similar areas - yet carbon is wholey evident


Why???

The original build thread for OST-007 - OST-007 - build thread

[allencr]

Head is soft.

[Toy77]

it looks like where the cooling galleries are is the no carbon spots....
so perhaps the other areas are slightly hotter, and that is the difference?

im just guessing... that just looks like the pattern on the bottom pic.

Cheers
Stew

[Rens]

Looks like that's where the fuel mist flows after coming out of the valve. That whole side of the chamber is lighter than the exhaust side. Either from the cooling effect of the fuel or it just washes away the carbon.
( i'm guessing though)

[Billzilla]

Seems a bit random in places so I'm not really sure sorry.
The camber is usually clear(ish) of carbon build-up where the squish areas are just right, that's why you get clean patches on the squish areas on the head and piston - Though it can also mean that the turbulence in the chamber isn't getting into those areas for some reason.

[Celica RA45]

i would say some cyl are lean and some are rich put 4 lambda bungs on your pipes 100 mm away from ports and retune each cylinder if you can .providing you have a after market ecu

[oldeskewltoy]

i would say some cyl are lean and some are rich put 4 lambda bungs on your pipes 100 mm away from ports and retune each cylinder if you can .providing you have a after market ecu

actually... the reason this engine came out was a failed crankshaft timing sprocket/crank key... it was running on stock AFM type management, but with wild timing swings... all sorts of conditions can exist









an unusually view.... each intake port has been photographed from directly in front, and with a particular view down the injector port, and then cobbled together. Note the injector holes favor one side of the splitter - this is nothing new... its why a largeport fuel rail and a smallport fuel rail are not interchangeable. Now this TVIS engine had been in an AE86 with stock management, so add in batch injection.



Now here is one more cobbled together photo.....




The majority of the fuel sits on the favored valve(follow the "RED" from the injector hole to the combustion chamber), and washes the chamber when the valves open...

[oldeskewltoy]

Taking the above photo to the next persepctive.... Is TVIS suppose to add tumble???





note where the injectors are placed, and where the TVIS plates are placed - the same valve per port.

Is low speed air flow "suppose" to tumble because of both? a) TVIS plate, b) majority of fuel sitting on one valve

[old_mr2]

Was this motor pinging/knocking at all? Perhaps these spots are where an unwanted ignition event was occuring.

[thechuckster]

did you have matching or similar patterns on the piston tops?

edit:

Is low speed air flow "suppose" to tumble because of both? a) TVIS plate, b) majority of fuel sitting on one valve

the TVIS should somewhat alleviate low-airspeed by closing off that runner at engine revs when you expect low air speeds.

did the engine have correct fuel pressure in the rail? or correct injectors?

[oldeskewltoy]

there was no pre-ignition that I know of.... There are no similar marks on the pistons. The engine fuel pressure I can't determine(no gauge, but it is the same pump in it now as then, now with a completely stock TVIS engine. The injectors were a mild upgrade... Honda injectors from the mid/late 1980s low ohm, and 240cc @ 3 bar(Accord/Prelude 2.0)

[mattysshop]

those injectors seem to be a little bit larger than most 4AGE injectors.. not by much.. though..

factory suggests that the cream/white and pink 'bigport' injectors are 195cc @ 2.9bar.. and the green smallport ones are 210cc @ 2.9 bar..

i've had a set of the pink bigports cleaned and tested, they all came up at 215cc +/- 3cc @ 3 bar..

[oldeskewltoy]

those injectors seem to be a little bit larger than most 4AGE injectors.. not by much.. though..

factory suggests that the cream/white and pink 'bigport' injectors are 195cc @ 2.9bar.. and the green smallport ones are 210cc @ 2.9 bar..

i've had a set of the pink bigports cleaned and tested, they all came up at 215cc +/- 3cc @ 3 bar..

This engine was/is running a mild cam update - Kamikaze Kams KK294, which is VERY similar to the Web 294. Duration is 218@ .050" cam lift is 8.18mm. We decided to go with the slight fuel bump because of the cam bump