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Post by dave1800 on Jul 16, 2011 4:06:21 GMT
Maybe this would help? www.123ignition.nl/id/53.htmlHave you looked at the 123 "Tune" ignition. That's the one I meant - sadly not available for A+ engines... Alexander |
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Post by threelitre on Jul 17, 2011 13:19:55 GMT
I've seen that - but that's of no help. Using a wideband O2-sensor I have the mixture on LPG setup spot on - ranging from slightly weak on cruise to rich on full throttle at low to medium rpm and slightly rich above. This 123/LPG is (just) another closed loop device for Venturi installations - a fairly expensive one at that. I am considering a programmable ignition with switchable maps, as the car pulls way better on LPG in the low-medium range when I run it with an additional advance of 6-8 degrees. At rpm above 3500 it starts to run out of steam with these settings... I could reprofile the standard distributor, as I don't use petrol at all unless I need a 'get-me-home' when run out of LPG - last time 2 years ago...
Regards,
Alexander
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Post by dave1800 on Jul 18, 2011 3:39:53 GMT
This company modifies 123 ignitions, although they don't list A+ as an option, maybe worth a call if you've not found them already? www.123ignition-conversions.com/As an aside, and getting back to Landcrabs, have you tried your wideband oxygen sensor on your 1800 to see how good or otherwise the needle profile is for your car? I've seen some reports suggesting the needles can be hit or miss with both weak and rich areas. Some worthwhile improvements have apparently been made by changing to another stock needle or by reprofiling. There are some useful SU needle sites that enable you to find a more suitable profile by comparing the measurements along the length which you can use with your wideband sensor readings. Maybe you could safely improve your fuel consumption! regards David I've seen that - but that's of no help. Using a wideband O2-sensor I have the mixture on LPG setup spot on - ranging from slightly weak on cruise to rich on full throttle at low to medium rpm and slightly rich above. This 123/LPG is (just) another closed loop device for Venturi installations - a fairly expensive one at that. I am considering a programmable ignition with switchable maps, as the car pulls way better on LPG in the low-medium range when I run it with an additional advance of 6-8 degrees. At rpm above 3500 it starts to run out of steam with these settings... I could reprofile the standard distributor, as I don't use petrol at all unless I need a 'get-me-home' when run out of LPG - last time 2 years ago... Regards, Alexander |
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Post by threelitre on Jul 18, 2011 11:37:00 GMT
I have not had it on the 1800 yet, but the old family bus (an S) is running very well. I've used it with an probe to fit the tailpipe on a VP 1300 (with lots of modifications). My initial adjustment was not bad - but dipping to 0.8 on acceleration seems a bit heavy. It does not really replace a pair of colourtunes on a mulit-carb car though...
Having a 123 tune built to spec sounds good - but also serious money just for some small perfectionism...
Alexander
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Post by dave1800 on Jul 18, 2011 12:57:10 GMT
You are right the 123 tune is not cheap - if you needed to replace a distributor maybe worth considering. I am sure you are way ahead of me with your thinking and information, but others here may find this site useful. www.jcna.com/library/tech/tech0015.htmlI think it describes very clearly how the Lucas distributor works, and how to check for faults and how it can be modified. I do wonder how many people skip over this without realising how much of an impact correct timing across the range can have on performance, economy and engine life. So I guess you may be getting out the grinding wheel to address your timing issue with LPG for free? I have not had it on the 1800 yet, but the old family bus (an S) is running very well. I've used it with an probe to fit the tailpipe on a VP 1300 (with lots of modifications). My initial adjustment was not bad - but dipping to 0.8 on acceleration seems a bit heavy. It does not really replace a pair of colourtunes on a mulit-carb car though... Having a 123 tune built to spec sounds good - but also serious money just for some small perfectionism... Alexander |
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Post by threelitre on Jul 18, 2011 13:18:48 GMT
Nice link that!
I have indeed considered modifying the dizzy, in particular as I have 2 more of them here as spares. As the Maestro's distributor is already an electronic one, the difference to a 123 just replicating the original curve would not be big. The 123\tune offers a good package, again not cheap, but easy to install. A MegaJolt would offer even a little more (i.e. I'd be able to program a fuel shut off on overrun for LPG on this), but the installation is quite a bit more involved.
First thing would be to find out a good (or even optimal) ignition curve! Without a rolling road I tried already to look for alternatives: In the old days a stop watch would have been the choice of weapon (plus a vac gauge). I looked into using a GPS and derive acceleration from the positional data. As the updates are slow, it would not work with a supercar, but given the (very, very) modest performance of a 1.3 Maestro on LPG, I think, that full acceleration on a flat piece of road in 3rd will give useful results with the possibility to find out performance changes in relation to rpm (and current distributor setting obviously). Repeating the road at given speeds on part throttle with the vac gauge should give the vacuum advance... So far I have not yet found the time, but the plan is to do a set of runs with the distributor turned 2 degrees a time and later compare graphs at home.
With these tools recurving a distributor to a good custom set should be more or less free - apart from a bit of fuel and some spare time. It would obviously work on other cars too...
Regards,
Alexander
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Post by dave1800 on Jul 19, 2011 1:23:01 GMT
An interesting idea using GPS; it would be good to test the idea against a stop watch on a section of road. The biggest problem in setting up timing curves without a rolling road is detecting knock, I'm not sure how much of an issue this is as it is claimed LPG engines sufffer less, but some report using LPG can cause valve seat regression. There are a number of cheapish knock indicators on the market (as well was those that automatically retard the ignition if knock is detected), but I don't know how well these work with all the valve gear noise - certainly on a 1800 B series engine - maybe the A+ is a lot quieter. regards David First thing would be to find out a good (or even optimal) ignition curve! Without a rolling road I tried already to look for alternatives: In the old days a stop watch would have been the choice of weapon (plus a vac gauge). I looked into using a GPS and derive acceleration from the positional data. As the updates are slow, it would not work with a supercar, but given the (very, very) modest performance of a 1.3 Maestro on LPG, I think, that full acceleration on a flat piece of road in 3rd will give useful results with the possibility to find out performance changes in relation to rpm (and current distributor setting obviously). Repeating the road at given speeds on part throttle with the vac gauge should give the vacuum advance... So far I have not yet found the time, but the plan is to do a set of runs with the distributor turned 2 degrees a time and later compare graphs at home. With these tools recurving a distributor to a good custom set should be more or less free - apart from a bit of fuel and some spare time. It would obviously work on other cars too... Regards, Alexander |
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Post by threelitre on Jul 20, 2011 9:26:32 GMT
The valve seat recession is a problem with LPG, a little more so than with unleaded but due to the same reasons. I run my Maestro with an unleaded head since about 100k kms not using leaded fuel or lead substitutes. Of these the last 60k kms have been on LPG only. At first I ran it with the standard ignition timing and checked valve clearance every 5k kms. At first the recession was hardly noticable, but then it started to appear so much so, that the exhaust valves (only these of course!) were tight every 5k kms. Then I advanced the ignition timing a lot (6 or 8 degrees, I forgot how much) and immediatly found the engine pulling much better on LPG at low to medium revs. If needed it still does run on petrol, but I just used that in emergencies two or three times since. The slower burn of LPG compared to petrol does indeed allow more advance, but this also reduces the heat seen by the exhaust valves - recession slowed down quite a lot. I assume that with the petrol timing setup the exhaust valves are exposed to unburned or just burned mixture. Right now the exhaust valves sit about 1mm higher than the inlet valves, but they still do seal well. For the case of a burned valve eventually I have a head set aside with factory fitted unleaded-spec valve seats.
When resetting the ignition I am not too worried about not detecting pinking. I think it can be heard quite well when fully established. The point is to get to the point were it actually is pinking and then back up quite a bit (2 or 3 degrees should do), the onset of pinking might indeed go unnoticed. The A+ in the Maestro is much more refined, since it uses a VW gearbox end on. But on my father's 1800 S it was always easy to find it pinking when filled with the wrong fuel (in the 70s and early 80s it did usually not like Shell fuel, Aral was always fine!).
Regards,
Alexander
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Post by dave1800 on Jul 21, 2011 0:04:30 GMT
I have found an article which suggests that you are right to advance the ignition to run on LPG at low to medium engine speeds, but that the LPG burns faster than petrol at higher engine speeds, so you need to retard it again higher up the range. www.acl.com.au/web/acl00056.nsf/0/359683e8a538a3e64a2566c0007bb33e?OpenDocumentThis article is clearly promoting what now appears to be an obsolete product known as "dual curves"; but if it is accurate then you could be damaging the engine. There maybe products still available to correct the ignition for LPG and petrol that could be a (cheaper?) alternative to 123 Ignition. regards David The valve seat recession is a problem with LPG, a little more so than with unleaded but due to the same reasons. I run my Maestro with an unleaded head since about 100k kms not using leaded fuel or lead substitutes. Of these the last 60k kms have been on LPG only. At first I ran it with the standard ignition timing and checked valve clearance every 5k kms. At first the recession was hardly noticable, but then it started to appear so much so, that the exhaust valves (only these of course!) were tight every 5k kms. Then I advanced the ignition timing a lot (6 or 8 degrees, I forgot how much) and immediatly found the engine pulling much better on LPG at low to medium revs. If needed it still does run on petrol, but I just used that in emergencies two or three times since. The slower burn of LPG compared to petrol does indeed allow more advance, but this also reduces the heat seen by the exhaust valves - recession slowed down quite a lot. I assume that with the petrol timing setup the exhaust valves are exposed to unburned or just burned mixture. Right now the exhaust valves sit about 1mm higher than the inlet valves, but they still do seal well. For the case of a burned valve eventually I have a head set aside with factory fitted unleaded-spec valve seats. When resetting the ignition I am not too worried about not detecting pinking. I think it can be heard quite well when fully established. The point is to get to the point were it actually is pinking and then back up quite a bit (2 or 3 degrees should do), the onset of pinking might indeed go unnoticed. The A+ in the Maestro is much more refined, since it uses a VW gearbox end on. But on my father's 1800 S it was always easy to find it pinking when filled with the wrong fuel (in the 70s and early 80s it did usually not like Shell fuel, Aral was always fine!). Regards, Alexander |
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Post by Keef on Jul 21, 2011 5:18:13 GMT
Wow - that stuff looks interesting!! Used to be :  |
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Have you looked at the 123 "Tune" ignition. 
