After a few problems with my inlet tract (detailed in other threads) everything looks fine again but I've had to vent out my breathers through a catch tank. The last mapping (Power FC) was done with the system fully recirculating, although through a catch tank.

I had assumed that fixing the leaking inlet pipe and venting out the breathers would put everything back to normal, but it seems that my injector duty cycles are noticeably up, by around 10% on full load. Fuel pressure is fine, lambda voltage looks fine etc, the only change is that now the breathers are open instead of recirculating.

Any thoughts on why this IDC % might be up, and whether it needs a map tweak to account for it?

CHeers!

 

so does the apexi run closed loop on full load ? I'll answer my own question and say no. You are probably just running a bit further up the map, is the afr correct ? If so there is nothing wrong as long as the ignition map is also suitably scaled.

bob

 

Thanks Bob. I think your assumption is correct, although I can't be certain. It's mapped for 1.45 bar and the AFR looks right to me from the lambda voltage, although really I need to get it back on some rollers and do a power run. Can you explain what it is about venting the breathers out that would make it do this? I've been trying to work it out but I'm not sure if I'm thinking straight.

Previously, it was working totally standard; rocker cover breathers drawing in fresh air from the inlet pipe (through an extra PCV valve that I put in), crankcase still connected to the normal PCV on the manifold and the other line blowing through a catch tank and back to the inlet. It never gave me any problems whatsoever. This is how it was mapped and IIRC, injector duties maxed out at around 70%.

Then, because I managed to snap off the connector for the breather return into the inlet pipe, I was forced to just vent the whole lot out through the catch tank to atmosphere. Since fixing up the inlet pipe and rearranging the breathers, the engine's running fine again, but hitting up to 82% IDC on full load pretty regularly.

I can't see what's changed. Before, some of the metered air would have bypassed the inlet tract through the crankcase but still eventually have been consumed. It might have picked up some oil vapour but the oxygen can't have gone anywhere can it?

 

that is a considerable increase in duty.. are you sure there was not an inlet pipe leak when mapped?

have you changed the inlet pipe to a different type to fix the leak?

Simon

 

Well that's something that I was wondering. It could have been leaking slightly and I wouldn't have known about it, which would definitely account for the difference I suppose. It was the standard black plastic pipe, all I did to fix the leak (at the turbo end) was to cut off the whole of that flexible rubbery section back the first bend, sleeve it over with a silicone coupler, job done. Went to push the catch tank return back onto the connector on the top of the pipe and it just came straight off in my hand! So now it's bunged up. I had a big Autobahn pipe before which fitted up pretty good but caused terrible surge so I went back to an OE pipe. What I really want is a Prodrive pipe but with a connector in the side to take the dump valve return.

 

think what you might of done is, when you cut off the flexible section and replaced it with a smooth bit, it has increased the aur flow.

when i replaced my standard inlet pipe with a samco one, i needed a little bit of a tweek, as it was coming on boost earlyer on in the map, and getting abitmore lean. i think that what was ahppening anyway lol

 

Different thing though as increasing airflow would indeed make it run lean,but to increase idc's would not i think happen in that case.... removing the dirty air that the breathers re introduce to the intake would have an affect on running,but again not sure why injector duty would alter........strange

 

consuming more air, increasing maf voltage and therefore idc

 

Simon... thanks for that,makes sence now.

 

I admit you may have something re: the inlet pipe may have had an unnoticed slight leak when it was mapped, meaning that the MAF would be reading lower than it should for a given airflow into the engine. But if that wasn't the case, and if this HAS been caused by the breather mod, I still can't see how replacing a small percentage of 'dirty' air out of the metered airflow with 100% clean would make any difference? Surely the MAF will read the same at the opposite end of the intake when you open the throttle and pull the air through? Therefore IDC should be the same?

Or is the dirty vs clean just a red herring and it's all down to less overall restriction in the inlet i.e. beforehand you had the main inlet flow with some of it being bypassed through the crankcase and back in, whereas now it's all going down the main route with no take offs at all? Kind of like making a certain volume of road traffic go along a single carriageway road and a cycle lane rather than a dual carriageway? Bad analogy I know but I can't think of anything else?