Graze Posted February 9, 2015 Report Share Posted February 9, 2015 I have used the search function but couldnt find the answer to this I have been told that the diagrams in the Bently manual re the metering unit setup are incorrect is this the case? I cant attach the page from the manual but it says the "Note" section is confusing as it appears to describe something completely the opposite what is says the shaded area represents "black shading represents rotor" "A shows sleeve port almost covered by rotor" - which is not how i interpret the drawing please set me straight Graze Quote Link to post Share on other sites
snowric Posted February 9, 2015 Report Share Posted February 9, 2015 I have found this site which has a scan of all the original factory set up and diagnostic card useful - sorry I cant check Bentley as don't have a copy. You can see on the blue card the correct and incorrect view from port no.6 when set up correctly. https://plus.google.com/photos/115471290043093657458/albums/5297755374081314625?banner=pwa Snowy Quote Link to post Share on other sites
HarveyCoppock Posted February 9, 2015 Report Share Posted February 9, 2015 This is what the Triumph manual and Haynes show also - the port on the rotor is the darker circle within the circle of the holein the MU for the pipe union. Think there is a comment in an old Technicalities that if you get it wrong you won't notice anyway... Quote Link to post Share on other sites
TriumphV8 Posted February 9, 2015 Report Share Posted February 9, 2015 They made a lot of noise in those days, because it was one of the first fuel injected cars. Some years later with the start of electronics and continous injection from BOSCH that topic was nearly lost. Todays EFIs like my cheap one do not advertise timed injection and by the way they are set up that under full load/high revs the valves are nearly full open all the time. It is not necessary to pay as much attention on that timing like on ignition and valve timing. Fact is that the timing of injection gives a very, very small amount of max. power increase. It has a noticeable effect on emissions that are mainly measured at idle and idle quality a bit. The reason is simple: If you fire the injector when inlet opens you spray the fuel into a quickly moving airstream get good atomisation but also may run into trouble that when both valves are open at TDC a little bit is directly blown into exhaust what is bad for pollution. Care must be taken to avoid. If you fire the injector after inlet was open there is some time for the fuel to condense at the walls of manifold and than walk with the airstream as a film to the inlet valve. On the other hand at high revs it has some time to atomize and cool the airstream. So the setting has mainly some influence on idle quality and air pollution. As far as I remember a lot of the confusion came from the different setups which first follow the idea to spray into the opening valve airstream and later watch idle quality what gives a different setup. Quote Link to post Share on other sites
Graze Posted February 9, 2015 Author Report Share Posted February 9, 2015 Snowy brilliant thanks - it differs from the Bentley in the description - all now clear thanks Harvey & Andreas Garze Quote Link to post Share on other sites
snowric Posted February 9, 2015 Report Share Posted February 9, 2015 Graze, One thing i discovered - PMI and Neil both mark the casing and the coupling between the rotor and dizzy drive so as long as you set you the distributor on 1st cylinder firing, the metering unit is rotated to the right place when you mount it and therefore you do not have to remove the no 6 port when re-fitting. Have you checked your MU to see if these marks are on there ? Snowy Quote Link to post Share on other sites
Graze Posted February 9, 2015 Author Report Share Posted February 9, 2015 Snowy It wasn't actually for my car I fitted mine 180deg out a year ago -since rectified and lesson learnt I looked at a car today, drove it in fact, and it drove like mine did when 180deg out so suggested same to the mechanic who has been working on it and told him that the Bentley manual (which he had downloaded some info from) had an error - promised to find out what the error was as I couldn't remember. Your link clarified it Cheers Graze Quote Link to post Share on other sites
Peter Cobbold Posted February 9, 2015 Report Share Posted February 9, 2015 (edited) It was the Haynes manual that printed the diagram rotated through 180deg. As Andreas says, timing the injection ensures the fuel squirt coincides with air moving fast through the manifold and reduces the amount that hits the wall. If the squirt is mistimed and comes when the inlet valve is shut the air velocity is slow, or near zero at lower rpm, and some of the spray impinges on the walls. That fuel film will, after a lag, evaporate off the walls or off the hot inlet valve, so the engine runs 'OK' but it wont respond to transients quite so well. If an engine pinks badly when the throttle is suddenly opened fully then timing the MU might help. Mis-timing will make the lean spike worse: https://supertrarged.wordpress.com/2013/06/12/the-lucas-pi-lean-spike/ Peter Edited February 9, 2015 by Peter Cobbold Quote Link to post Share on other sites
JohnC Posted February 16, 2015 Report Share Posted February 16, 2015 Peter, I think we ought to nickname you "Spike" BTW I've just fitted a wideband UEGO sensor and data logger recording AFR, vacuum, rpm and acceleration. Once it's all working properly I'll see if I can spot the lean spike while driving on the road. I don't feel any hesitation, but perhaps my MU is set rich enough that it doesn't lean out enough to affect power. May be different once I start tweaking the max fuel setting. Cheers, John Quote Link to post Share on other sites
Peter Cobbold Posted February 17, 2015 Report Share Posted February 17, 2015 (edited) Peter, I think we ought to nickname you "Spike" BTW I've just fitted a wideband UEGO sensor and data logger recording AFR, vacuum, rpm and acceleration. Once it's all working properly I'll see if I can spot the lean spike while driving on the road. I don't feel any hesitation, but perhaps my MU is set rich enough that it doesn't lean out enough to affect power. May be different once I start tweaking the max fuel setting. Cheers, John John, There can only be one Spike, who told us he was ill: http://news.bbc.co.uk/1/hi/england/southern_counties/3742443.stm Nothing like measurements to diagnose issues, or to confirm its running right! Peter Peter Edited February 17, 2015 by Peter Cobbold Quote Link to post Share on other sites
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