Anyone have any thoughts on this solution, and whether I need an oil catch can fitted? There seem to be mixed opionions on whether this is necessary for N/A cars, but as I have fed the tube so close to the intake manifold I’m concerned about significant amounts of oil getting in.
I notice the stock air intake has this box where the crankcase tube originally fitted. Was this serving as some sort of oil catch system?
An NA car [arguably] doesn’t need one as the intake is always below/at atmospheric pressure, so the crankcase can’t be pressurised via a vent to the intake (this isn’t the case with forced induction). Note, however, that most of the time, your crankcase will be drawing air in through the tube near the oil filler cap and venting directly into the intake plenum through the short ‘L’ shaped tube from the PCV on the cam cover. It will only vent through the long tube under WOT.
I think some people like to fit a catch tank in the small line to keep the intake tract cleaner.
I believe that is an empty air chamber to tailor the resonance in the stock intake tract which improves mid-range engine response. Removing this reportedly reduces mid range power without any benefit elsewhere. (Much has been written about it on various forums.)
I’ve since added a hose clamp so the tubes connect tightly to reduce risk of unmetered air.
Slightly off-topic question, do you know what the tubes between the intake manifold and strut are? Wondering if i can relocate them in an attempt to clean up the engine bay.
Catch tanks can be of use in an na car, don’t know about the mx5 but my mustang was na and that would regularly half fill the catch can every 500 miles or so with oil that would otherwise have ended up in the intake… It did this from new and was/is a known characteristic. A different beast I know but in that application it was worth fitting one.
Not sure. Your fuel flow & return lines will pop up about there, but it looks like someone has removed the evaporative emissions charcoal canister and possibly the EGR solenoid from your car, so possibly hoses that should connect to one of those - I think the fuel tank vent will be one of them.
Greg Young,
You don’t need to worry about the cam cover breather location as long as it is in more or less the same place as the amount of oil vapour should be minimal if the camshaft bearings are in good condition - oil flow from the cam bearings is mainly back into the sump.
Someone definitely has removed the evap canister and pipes. I would check which garage did the last MoT and use them next time, as technically removal of the evap. system is a major fail on an MoT test, it is part of the emissions system. I’m a bit surprised that your MIL isn’t on as the OBD-II system ought to register a fault, and that there aren’t any oil leaks as if all the hoses are connected to each other, the crankcase breather should be pressurised !
Here’s the workshop manual page. Apparently if you use an OBDII reader you can erase the code that causes the MIL to come on, but in my experience if you have a fault the MIL will keep coming back.
There does seem to a degree of correspondence on various sites about removing the evap. emissions pipes and catch tank ( which is what the thing with 3 pipes under the bonnet officially is, the charcoal canister is adjacent to the fuel tank), but mainly in US states where they don’t do emissions checks.
Personally I think that the emissions from the fuel feed system are minimal, and the MoT Test regulation is open to interpretation, but if a tester interprets “emissions system” as including the evaporative loss system, then Greg Young’s car would fail.
From what I understand, the MIL light is triggered if the purge solenoid is unplugged - On Greg’s car, it’s still there and plugged in, but the outlet and inlet are looped to each other.
I’m not sufficiently expert , but on an OBDII car the system is monitored all the time, the link below is a US state government explanation of evaporative emissions systems in general. As far as I know UK systems are the same, however you could be right in that as long as there is no vapour leak, presumably measured by a pressure sensor, then the MIL isn’t triggered. It may just be fortunate that the pressure is within the normal range…or maybe the MIL isn’t working!
OP says the car is a MK2.5, which is 2001 onwards and definitely has OBD II with a port under the dash near the steering column. NA did not have OBDII, not sure about NB as the the intro date was driven by US legal requirements .
