BINGO!Originally Posted by Giamanut
As mentioned, that hose from the evap canister is for the purge line. It not only purges the vapors collected whilst the vehicle is parked, but it also prevents excess vapor pressures from building up while the vehicle is running. But that is an entirely different topic there...
I *believe* the reason the oil cap connects to the cold start tube is to facilitate air flow so that the evap system and the cold start valve can both feed their respective vapors down into the intake manifold. Part of the crank case vapors are drawn down that tube to provide an airflow that can push the evap & cold start payloads down into the intake manifold.
It's like if you were sucking on a straw that was in a milk bottle, but the bottle was perfectly sealed at the top around the straw. Without a vent hole to replace the displaced fluid inside of the container, the vacuum you create inside the bottle would pull the fluid up and prevent you from sucking out the milk. Thus you've eliminated the flow of the liquid and can't suck anymore out. BUT, poke a hole in the top to allow for airflow, then suddenly the air rushing in will allow you to suck the rest of the milk out because it will push down on the liquid and force it up the straw.
Thus the small diverted flow of crank case gasses from the oil cap helps carry the gasoline mist from the cold start valve and the carbon canister down into the intake manifold. And of course the reason you wouldn't straight pipe that is so that you don't apply full vacuum directly to the cold start valve or the carbon canisters. Just in case you're also wondering about the gasoline vapors being introduced into the manifold as unmetered fuel, never fear, LAMBDA will tweak the AFR accordingly to fine-tune things so that the engine is unaffected.
P.S. If that oil cap gets too restricted, the crank case pressures will build up enough to purge engine oil through the front main seal. Been there, done that. Overall, if someone else can correct me on any of this, please do. But I can assure you from past experience that you want to leave those hoses in place as intended.
No need to reinvent the wheel. All fuel metering is already done by the air flow meter in the mixture chamber, Any and all additional minuscule introductions of un-metered air from the crank case vent have already been accounted for by BOSCH. The fuel map which the engine uses was already predetermined at the factory, and the vacuum lines, vacuum delays, hoses sizes, vacuum curves, fuel flow rates, etc. have all been pre-calculated by BOSCH and are executed mechanically by K-Jetronic. It has all been accounted for, which is why there are so many different part numbers unique to the vehicles which received this fuel injection system. No need to reinvent it.
As for deleting the cold start valve and having the injectors take over it's duties, that can't be done. The mechanical system was never designed to have such a flow rate. Now, EFI injectors are, which is why modern cars don't use choke flaps or cold start valves. They're designed for those massive flow rates during cold starts. In order to accomplish such a task, you've have to graft in a second frequency valve, and then wire it to the CSV's old circuit. Then you'd need hoses, injectors, a fuel distributor, and then a new fuel pump. Because remember, this is mechanical fuel injection which requires hydraulic line pressure to activate the injectors. The wider the injectors open, the more line pressure you need to accomplish that. But even then you cannot know what parts to use until you calculate what the necessary line pressures would be, and then adjust the primary pressure regulator accordingly. Then you'd need to ensure that the warm up regulator's flow rates were acceptable, and have to then also calculate the vacuum activation pressures and delays to get that to work in harmony as well. If you were going down this kind of road, it would honestly be much easier to convert the whole engine to EFI than try and reinvent/reassign the functions of K-Jetronic.
Also, please do not think that I am trying to flame you or anything like that. By all means, please do not hesitate to ask questions. It's how I learned.
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