First Issues - Alfa 147 1.8 TS

[scottyf]

Hello All,
After completing over 20k with the LPG install. I've come across my first issue.
Having serviced my car (Normal not LPG) I changed my air filter to a more free flowing BMC CDA.

Anyway. I've noticed as the temperture has dropped in the UK over the past week or so If I open the throttle to wide open The car rev's up to about 4500rpm and then struggles to go above.

Now I do use the full range of rev's on my car daily. So not having that limit of 7k is a bit annoying.
Weirdly enough my mid range has improved in power (So below 4500rpm).

My thoughts are that my new piping for the air intake before the MAF sensor is now getting quite a bit extra oxygen than it was before.
So when I give it the boot I don't get a warning light becasue I believe the ECU ignores Lambda read's and switches to open loop.

However what I did notice is if I let it go past the 4500rpm limit on lower throttle opening, almost fully open it'll rev like normal.


So I am thinking I need to re-tune my system to allow more lpg to be flowed in to get it to give full power at WOT.
Would I be correct in thinking this or could there be other issues?
I guess there could be several issues but given the rest of the car performs normal on lpg and petrol this doesn't happen makes me think its running lean in WOT.

[LPGC]

Usually I don't think replacement air filters would make all that much difference... But would tend to agree with your thoughts on needing more gas to go with extra air in this case - but that might imply your engine was already running lean near WOT on gas before you fitted the new air filter.

If it's made that much difference, would also get me looking at where I'd fitted the manifold pressure take-off / if I'd disturbed or changed anything else whilst fitting the air filter.. Change of plug type or introducing kinks in injector pipes could both cause your symptoms.

Maybe a bit more of a point in your case because I seem to remember you saying you set the car to switch to LPG at very low temp... Would first drive it gently and far enough to get the reducer and gas temps well up, and then see if the same issues exist... Could just be down to temp correction in software. A second point regards temp correction is that it is possible to select pressure and nozzle size that work well for warm (summer) gas.. this implying LPG injector duration is above petrol injector duration... but then when (maybe correct) temp correction is factored in for colder temps gas injector duration goes below petrol injector duration - this can cause issues that are mostly evident during increasing engine load. Exacerbating this issue, at some pressure settings some types of reducer seem to give different (higher) pressure at cold temps - would think due to stiffer diagphram or tiny drops of liquid gas spray into vapour pipes (latter could be interpreted from seeing very low vapour temp). Even possible with low vapour temp for vapour to change back to liquid in injector nozzles (as it goes from relatively high pressure in piping to lower manifold pressure - some injectors far better than others in this respect).

Simon

[scottyf]

Seems your thoughts are correct simon as its worse during warm up.
so your diagnosis would be correct.

Have returned to the gas maps to help whilst very cold and it seems to have sorted it.

Although does show how fine the setup is and that at wot it was running lean.
Thanks for your help

[scottyf]

I think it just highlighted how clogged with leaves and other debris my old intake was and how gummed up the filter was from 10k of driving alone.
Still interesting to see.

Still gonig strong though and no real issues other than some minor tweaks. Have saved so far £1400. Well just under that but it's great. Really is no need to ever run a diesel.