as some of u may know, i converted my 1.3 to a 1.8 16v in december. the car& has been running fine since, apart from the recent head gasket failure and im currently putting it back together. once thing i didn't fit during the conversion was the small vacuum pipes that run the MPG from the ecu and such. i've got a session booked at stealth for the 29th april and wanted to know if these missing pipes would affect my performance or power output. i want my car running as sweetly as possible. thanx people. Edited by: Davs
The MPG figure doesn't come from the ECU, it comes from the dash computer. If you don't have a vacuum line hooked up to your ECU then your timing will be all over the shop - and if you've left any of the lines/stub connections open to the air, you'll have unmetered intake air and be running lean......
but my MPG is not working,and i can ear it sucking from the dash!maybe i sould plug it!? if its not pluged it will ruin the timing!?why!?
It's not that pipe that will ruin the timing, it's the one that goes to the ECU. But plug it or fix it anyway, it's a vacuum leak.
so i could get away with just plugging the vaccum pipe coming out of the ecu?? im sure i read here before that it only calculates the MPG?? really best to get a 2nd opinion on things like this then!! thanx TSC
The sucking you can hear from the dash could be the vacumn pipe which connects to the MFA. Is that connected/split?
The ecu vacuum pipe is needed to allow the ecu to alter the timing advance under load (20 degrees under wot), you need it connected as tsc said. If all the vacuum lines are connected to the same takeoff, the mfa air leak will also affect how much vacuum gets to the ecu, so it`ll also affect the timing under load as well as running lean.
No, no. These are two separate vacuum pipes being talked about. The one Hidro is talking about runs to the instrument cluster, and is used to calculate the MPG. The one you're talking about runs to the ECU and is used to control the timing.
right, so can anybody tell me where the feed comes from for the ecu vacuum?? there is a pipe coming from the top of my airbox that isnt connected to anything, could this be it?
There is a connection to the brake servo from the back right of the inlet manifold, follow that and you get to a one way valve and then onto the brake servo. There will be some smaller vacuum lines coming off at the one way valve and one of those goes to the ECU. Joe
wicked mate! so wot about this "spare" one coming from the airbox? think its from that thing that looks like a horn...
the sucking i hear from the cluster is a ?? cause its well pluged!but anyway,sometimes it reads 0.0l and some other times it reads normally(which is like 30l/100km ) plug it then!?
There is a vacuum line which goes towards the airbox and is connected to the overrun cutoff valve (grey plastic thing with elctrical connection) and the diaphragm pressure switch (metal disc with a 2 pin electrical connection, should be bolted to the airbox itself). Diaphragm pressure switch detects low vacuum when cold (i.e high load) and then injects extra squirt of fuel as part of the cold acceleration enrichment system. It's not really that important and is only used when the engine is cold. Same goes for the overrun cut off valve, it should connect two air pipes between the airbox and the plastic inlet pipe, it opens on overuun equalising the pressure each side of the airflow flap and so shutting off the fuel, it's only there to help MPG a little bit. I'd just block it off for now, get the engine running right and then worry about it later. Without the vacuum feed to the ECU, you'll be losing a lot of high load advance and therefore your engine will run very flat and unresponsive, tho compared to a 1.3 it'll probably still feel quick. Joe
