Tuning with twin maximum flow adjuster
in [Aussie Drivers]
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From: Andy on 27 Nov 2007 15:31 Yvan wrote: > Nedavno Yvan(a)office piše: > >> If I find some time today, I'll try and make my own amos ring. First a >> mack up (model) one out of a cardboard (perhaps I can start the engine >> with it if it is rigid enough). And then some sheet metal work. Hope >> it works. > > > It does. I made my amos ring out of cardboard today: > > http://www.ptt.yu/korisnici/i/v/ivica/lpg/amos1.jpg > http://www.ptt.yu/korisnici/i/v/ivica/lpg/amos2.jpg Mate, that's awesome. Seriously :-) Cheers, Andy.
From: Yvan on 28 Nov 2007 02:10 Nedavno Andy pi�e: > Mate, that's awesome. Seriously :-) Thank you :-) And I started the engine this morning at ~0 degrees Celsius. I drove the car for a few kilometers, and, while the engine was warming up, for a couple of minutes of the drive I had to work with a throttle to prevent it from stalling, but, as the engine temperature raised it was fine again. So, much better than it was with a spud pipe. Now I have fabricate new amos ting out of metal :-) Apart from the method I mentioned in my post from last night I found that area at the gas entry point should be number of HP times 10 in mm2 So in my case 90x10=900 mm2, which is equals my result from yesterday that area at the gas entry point should be 35x30 mm. Any thoughts? -- ___ ____ /__/ / \ ** Registrovani korisnik Linuksa #291606 ** / / \/ /\ \ ** Registered Linux user #291606 ** /__/\____/--\__\ ** http://counter.li.org/ **
From: John McKenzie on 28 Nov 2007 04:13 Yvan wrote: > > Nedavno Yvan(a)office piše: > > > If I find some time today, I'll try and make my own amos ring. First a > > mack up (model) one out of a cardboard (perhaps I can start the engine > > with it if it is rigid enough). And then some sheet metal work. Hope > > it works. > > It does. I made my amos ring out of cardboard today: > > http://www.ptt.yu/korisnici/i/v/ivica/lpg/amos1.jpg > http://www.ptt.yu/korisnici/i/v/ivica/lpg/amos2.jpg > > For the gas entry point I used a pipe where engine breather hose is > connected to: > > http://www.ptt.yu/korisnici/i/v/ivica/lpg/amosLPGin.jpg > > I started the engine and - it runs :-) I then decided to try driving > with it. I did not step on the gas pedal enough to open second barrel, > as the cardboard flexes under vacuum, and peaces are connected with a > tape, so I was afraid it might collapse. > > I will check tomorrow morning if it will start on lpg when engine is > cold. If it started on the old single barrel carb and lpg system it should on the new one. If it doesn't - you'd have to look at why. I won't post more on that for now - as it's probably going to be more confusing to add more theory now - only worry about it if it doesn't start. Athol mentioned the use of a 195F thermostat as a necessity - let me expand on that. There's two big reasons for it. For some reason a lot of lpg fitters will go to a 180 or even 160F thermostat. My only thinking is that it helps get around the fact that it'll have too much advance at higher rpms with a factory distributor, either that, or just a lack of understanding. "mythology" seems to go a long way in the lpg world. So - the reasons - the first one is that the convertors are actually designed to work and deliver lpg accurately at 190-195F - any colder than that and they'll just run richer, and use more lpg - and unlike petrol a highly rich mixture doesn't provide any power boost, it typically just uses more lpg. Anything short of that and you'll have a compromise on fuel economy. The other reason is one that applies to you more than us in Australia - temperature. The 'hotter' the thermostat, the longer it waits till opening. You'll find a 180 thermostat will start to open before then to make the temperature it holds eventually at 180. The 195F thermostat will hold on longer. If the thermostat is closed, the coolant does a loop through the block, through the heater, and through the lpg convertor, but not the big radiator - the later it opens, the quicker the car warms up. The quicker it warms up the sooner it will run smoothly on lpg. Which is of course the goal. Another thing to consider is the possibility that the method they have used to route hot water to the convertor isn't great. It might involve T - shaped joins, and end up allowing water to circulate without much of it going through the convertor. TO fix that, you can look at small restrictors in the line going to the heater, so that it forces more through the convertor. The other thing you can do is instead of the T connections, you run 1 big loop - from water pump, into the convertor, out of the convertor to the heater core, then from the heater back to the head or return hose back to the engine, wherever it re-attaches. The one thing you need to be aware of is if something happens to the engine, and it overheats, you'll have less warning of the guage going higher, since it starts off higher. This isn't a major problem (hell - all modern cars run higher temperatures to help emissions ) but I might as well mention it. > Next step is to make it out of metal, and to get it in a way that the > narrowest part is at the gas entry point (not easy with a easy flexing > cardboard). The design you made looks good. The only slight change I might suggest is making it a bit wider at the open end, and a little shorter, so that it can draw air from more of the air filter easily. This would only need to be a difference of about 10mm on your current design. > > I have a question about that. My previous carburetor had a 26 mm venturi > (the are of 530 mm2) and mixer plate ring inner diameter was 28 mm. > This new carburetor has 22 mm primary barrel venturi, and 24 mm at the > second barrel (combined area of 830 mm2). I was thinking of creating > 35x30 mm area at the gas entry point. That gives 1050 - ~200 (gas entry > pipe) = ~850 mm2. > > Is this correct? Should I do it in differrent size? How is it > calculated? This will sound very 'rough' - but beyond the basics I've mentioned, the 'hole' size is more 'test and revise' than it is pure science (at least in the ones I've seen).. For one of my own cars - they ran a carter bbd 2 barrel carb from the factory. Much like Noddy's ford pre efi carburettor, the biggest problem was that it didn't flow enough for such a large engine. Even though that is the case, I've had a few cars with the same engine (4-4.3 litre 6cyl - the australian made 'hemi 6' ) on lpg. Most of the stuff I've done is to get that as a starting point and improve. Two amos rings in particular have been common on this car. I'll get a couple of pictures. One of them isn't a huge restriction - and it works well (despite being a very subtle venturi). The other one was a huge restriction. It was great up to about 2500 (better than the bigger one) but above 2500rpm, it was well down on power - because it restricted airflow way too much. At a time when I had more free-time, I actually opened up the big one a little, and removed the venturi section, and all carburettor parts in teh main body, and even opened up the throttle plates - instead of 2 circles, it's now one big oval. It was about a 40% increase in flow over the original carb, and probably close to double the flow of the original carb with the more restrictive amos ring. But those amos rings are still common enough. You are much luckier - the size engine you have would not have any problems finding sufficient airflow through the setup you describe. Generally speaking if i was in your situation right now, I'd make the amos ring/ carb hat (whatever it's called) mostly as you have designed it (that small change I discussed maybe) and try it out. I'd only alter it if it lost either too much low rpm response, or died at higher rpms, and even then, I'd only go about 1mm at a time. Perhaps to make it easier - design and build it from steel, or whatever is convenient, but fill in the venturi section with braze welding, because that would be easier to build up and to grind to whatever shape and size you want if it needs it. -- John McKenzie tosspam(a)aol.com abuse(a)yahoo.com abuse(a)hotmail.com abuse(a)earthlink.com abuse(a)aol.com vice.president(a)whitehouse.gov president(a)whitehouse.gov sweep.day(a)accc.gov.au uce(a)ftc.gov admin(a)loopback abuse(a)iprimus.com.au $LOGIN(a)localhost world's #1 sardine whisperer root(a)mailloop.com $USER@$HOST $LOGNAME(a)localhost -h1024(a)localhost abuse(a)msn.com abuse(a)federalpolice.gov.au fraudinfo(a)psinet.com abuse(a)asio.gov.au $USER(a)localhost abuse(a)sprint.com abuse(a)fbi.gov abuse(a)cia.gov
From: Yvan on 28 Nov 2007 07:00 Nedavno John McKenzie pi�e: >> I will check tomorrow morning if it will start on lpg when engine is >> cold. > > If it started on the old single barrel carb and lpg system it should > on the new one. If it doesn't - you'd have to look at why. I won't > post more on that for now - as it's probably going to be more > confusing to add more theory now - only worry about it if it doesn't > start. I tried this morning, and it starts OK with paper amos ring. > Athol mentioned the use of a 195F thermostat as a necessity - let me > expand on that. > > There's two big reasons for it. > > For some reason a lot of lpg fitters will go to a 180 or even 160F > thermostat. What thermostat are we talking about here? The one factory fitted to the engine, that opens/closes coolant flow to the radiator? This is the only one I have. Do lpg fitters in Australia change this thermostat as a part of lpg conversion? Over here they do not. > If the thermostat is closed, the > coolant does a loop through the block, through the heater, and through > the lpg convertor, but not the big radiator - the later it opens, the > quicker the car warms up. The quicker it warms up the sooner it will > run smoothly on lpg. Which is of course the goal. My problems with engine stalling during warm-up are over before thermostat opens. I checked that by feeling with my hand hose from the engine block to the radiator - it was cold, and the engine was running OK on lpg at that time. >> Next step is to make it out of metal, and to get it in a way that the >> narrowest part is at the gas entry point (not easy with a easy >> flexing cardboard). > > The design you made looks good. The only slight change I might suggest > is making it a bit wider at the open end, and a little shorter, so > that it can draw air from more of the air filter easily. This would > only need to be a difference of about 10mm on your current design. Yes, I noticed that it is a bit too long when I placed air filter back in the air box, but that made no change to the engine (it was running at the time, I originally just wanted to test it in garage, but than I changed my mind and decided to go for a drive - so I placed air filter back in it's place), so I decided not to change anything. I will make it shorter and wider at the entry when I build it from steel. I am thinking about sheet metal (not sure I got material name right - sheet of metal 0.8 - 1 mm thick, that I will cut and bend into shape I want). >> I was thinking of >> creating 35x30 mm area at the gas entry point. That gives 1050 - ~200 >> (gas entry pipe) = ~850 mm2. >> >> Is this correct? Should I do it in differrent size? How is it >> calculated? > > This will sound very 'rough' - but beyond the basics I've mentioned, > the 'hole' size is more 'test and revise' than it is pure science (at > least in the ones I've seen).. OK. Than I will make it slightly larger than 35x30 mm, and narrow it with some "liquid metal" (two component mixture that can be used in high temperatures for seeling block cracks, tank leaks...) > Generally speaking if i was in your situation right now, I'd make the > amos ring/ carb hat (whatever it's called) mostly as you have designed > it (that small change I discussed maybe) and try it out. I'd only > alter it if it lost either too much low rpm response, or died at > higher rpms, and even then, I'd only go about 1mm at a time. Bad low rpm response -> gas entry opening needs to be larger, and, bad at high rpm -> gas entry opening needs to be smaller. Right? > Perhaps to make it easier - design and build it from steel, or > whatever is convenient, but fill in the venturi section with braze > welding, because that would be easier to build up and to grind to > whatever shape and size you want if it needs it. I was thinking to do something like that. -- ___ ____ /__/ / \ ** Registrovani korisnik Linuksa #291606 ** / / \/ /\ \ ** Registered Linux user #291606 ** /__/\____/--\__\ ** http://counter.li.org/ **
From: Yvan on 28 Nov 2007 10:13
Nedavno Athol piše: >> For some reason a lot of lpg fitters will go to a 180 or even 160F >> thermostat. My only thinking is that it helps get around the fact >> that it'll have too much advance at higher rpms with a factory >> distributor, either that, or just a lack of understanding. >> "mythology" seems to go a long way in the lpg world. > > Part of the "reasoning" expounded in one book on the subject was to > make the engine cooler under the inlet runners of a V8 to reduce > intake temp and hence increase intake density... I have somewhat specific thermostat. It's in it's own housing and I think that I can not find another "hotter" one. It's part number 7 here and it's 80CEL (180F): http://www.realoem.com/bmw/showparts.do?model=1051&mospid=47249&btnr=11_0744&hg=11&fg=35 >> Another thing to consider is the possibility that the method they >> have used to route hot water to the convertor isn't great. It might >> involve T - shaped joins, and end up allowing water to circulate >> without much of it going through the convertor. > > Almost every engine has some form of coolant "bypass". This is either > an internal connection or an external hose that feeds coolant from the > engine (hot) side of the thermostat to the input to the water pump > without going through the thermostat or the radiator. Its function is > to ensure some coolant circulation when the thermostat is closed. > > If the engine has an external bypass hose, this should be replaced > with a pair of hoses to the convertor and back. That way, the > guaranteed coolant flow for bypass heats the convertor. If there is a > heater circuit alongside the bypass hose, the convertor should still > be put in the bypass circuit, independant of the heater. This avoids > the type of T-pieces that John is talking about above. Do you think that it would be a good idea to connect a heater coolant into vaporizer at the part 14 (smaller diameter hose connected here is for carburetor autochoke heater) and output at the end of the hose 15 (it is connected to the cabin heater). Currently I have two T-connectors at the cabin heater hoses, and vaporizer hoses are connected there. Any benefit from that? -- ___ ____ /__/ / \ ** Registrovani korisnik Linuksa #291606 ** / / \/ /\ \ ** Registered Linux user #291606 ** /__/\____/--\__\ ** http://counter.li.org/ ** |