lpg feed pipe size on 500 bhp engine.

[robertXX]

i am certain you could be right simon , not to mention the airflow running down the side of the car changing the pressure ratio across the venturi's .it may end up having to be a megasquirt and injectors , but hey , i'll give it a try .

theoretically at speed , the front cylinders will run lean , and the rears rich ...now i can put fittings on the diaphragm side of the vaps ,and run a signal pipe to the right area for best homogeneity(made up word?)

[Oldskool]

That's a mental build Robert, I saw it before on R'n'S (I'm LazySteve on there) - do you go to the Hot Rod Drags?

[robertXX]

That's a mental build Robert, I saw it before on R'n'S (I'm LazySteve on there) - do you go to the Hot Rod Drags?

hi steve , i would be off to the drags if i was not stuck slumming it in vancouver doing family stuff. life eh!

[Oldskool]

Yeah life, but I imagine Vancouver's not bad at all - a bloke I know got persuaded to buy a time share, main problem is that it clashes with Mopar Nats every single year. Really bad planning !!

I'll be at the Drags - real nice atmosphere at that one I reckon.

[robertXX]

roighty ho , a bit of progress!!

WHAT!!! i hear you shout .?


yes its true , i finally got back to work on what i SHOULD be working on .:tup:



as you may remember , when i ran the engines up , they were not pulling enough lpg through to rev well . i have a couple of things i can do , one is to make smaller venturi for the throttle bodies , this will increase the air speed and create a stronger draw on the lpg rings .

another thing i can try is to connect another feed pipe from the vapourisers to the globes .this makes the vap more sensitive .and flow more gas for a given vacuum .

i decided to do the 2nd feed idea first .




extracting the globe was fun ,




i marked it up before removal so just had to drill and tap for the fitting







then re installed it with its new rear entry feature activated !







tomorrow i will get the other globe done and see if it runs with a bit more pepnosity .


regards
robert

[classicswede]

Normally you would fit an adjuster in both lines but with how it was I think you will be just fine the way that is

[robertXX]

well that was a bit of a damp squib !


i set too, fitting the front globe , and reconnecting the copper pipes , which was a bit of a barstard to do ,had to disconnect one venturi/bellmouth ,and various other dodges to get the things in their holes but after a bit of a struggle got it all in , then made a copper pipe for the new feed ,and it was all systems go .


i tried to fire it up , with no adjustments made to the vapourisers , and it was a stuttering smoky rich thing on cranking , so in a way that's a good sign that i have made a difference .


i adjusted it leaner ,and got it catching but not keeping running ,then noticed a slight difference between the two vapourisers ...














yup , we had a internal gas leak , and it was freezing up .

so tomorrow i take all the front one apart to fix ,oh joy !!:shake:




regards
robert.

[Gilbertd]

Hmm, that's why it was a bit rich then.....

[robertXX]

well on my smooth steady trip to things going from bad to worse , i fitted the other vapouriser i had spare , and went for a quick turn over , got a fair bit of brown smoke ,but that was it .


then has a listen to the front vap , and heard a hiss , it was leaking from the big brass fitting on the side opposite the flow adjusters .so i got that off and put the o ring from the other vap on it ,and that was fine ,then tried again , and this time , heard it leaking again inside and it got a little frosty too!!
bum!


so it seems as if both of the front vaps i have tried leak . what are the odds , i then wondered , because there is no water in the vaps , could they be getting so cold as to seize one of the internal valves , so that it leaks ?



anyrdup , i took it off the car , put both of them side by side and took them apart ...


first thing i saw was this












the flat plate vap i took off my old courier van , so know its history , the one with the humungously deformed plate i got of ebay for 30 quid , i am guessing that is some sort of huge backfire damage ??




internally they look pretty much as you would expect ,minw was bottom feed ,and im guessing the ebay one top feed hence the gook in it .

i found a couple of o rings i can look at , but apart from that nothing horrible .









all diaphragms appear complete and split free .


one thing i did notice was , my old vap had no springs , the ebay one had on spring on the post pressing on the diaphgam plate , i wonder what's going on there ,and whether i should leave it out ?


its going to be a right pain if i have to have the coolant system assembled to try it all , god knows how many gallons of anti freeze that will be !


regards robert.

[rossko]

You could extend the runtime a little before freezing by adding a bit of thermal mass, loop some water hoses temporarily and fill the vaps.

Be sure to hook the diaphragm onto the valve lever, so that 'inflation' pulls the valve closed. The odd dinky spring is I think there to help that happen from rest, but isn't usually essential. However, because you've previously tried to richen everything up and also don't have much restriction on the outlet, it could be that the diaphragm never inflates enough to shut the valve. To put it another way, the target pressure for the regulation is well above atmospheric so it just keeps dumping...
Temporarily block the outlets completely; if pressure builds high, its a fault; if it maintains a light pressure, its just a setup issue.

[robertXX]

thats a good idea rossko,thank you .

i could also boil some water and fill them with that too . in fact , if i get it re assembled , and make it leak on the car , then fill with hot water if the leak stops then that will tell me its the freezing that;s doing it .

regards
robert

[LPGC]

Perhaps stating the obvious - Unless there's some other issue why not just connect them up to engine cooling system(s) as normal, just don't bother with antifreeze yet and you won't be wasting any antifreeze, bit of a flush for the engines too. Core plugs sorted yet?

Simon

[Gilbertd]

Perhaps stating the obvious - Unless there's some other issue why not just connect them up to engine cooling system(s) as normal

Try to keep up at the back, he doesn't have any engine cooling systems yet.......

[robertXX]

Perhaps stating the obvious - Unless there's some other issue why not just connect them up to engine cooling system(s) as normal

Try to keep up at the back, he doesn't have any engine cooling systems yet.......

this is the best clubhouse feel forum lol.

[LPGC]

Perhaps stating the obvious - Unless there's some other issue why not just connect them up to engine cooling system(s) as normal

Try to keep up at the back, he doesn't have any engine cooling systems yet.......

this is the best clubhouse feel forum lol.

Yeh I was behind there .. But it's one thing keeping up with all progress on someone else's project which we're updated on sometimes bi-monthly, another thing posting views and insights on specific aspects, like why the engine wouldn't run...

Simon

[robertXX]

i have been pathetic in getting on with this ...but hey i do now have a happy family in vancouver i spent september with , and a 72 tvr back on the rd after 9 years off , and the next 15 ft of the batcave has a roof on it !!! wooF !


i was wondering , since i was getting brown smoke ,and not a lot of firing , maybe my new feed is so effective , i need to turn the valves on the other feed way down ?

when i built this ..


https://youtu.be/97J-CIztvAk



i spent ages trying to get it to run on the forklift carb , until i realized it was way too rich and it then fired straight up .

my mind set was its a much bigger engine ,so must need everything set on max fueling ,

i wonder if ,because of the 32mm venturi suggesting a lack of vac/fuel flow , i am making the same mistake here ?

next plan is to bung my courier van vap back on there ,connect a hose to feed water through them ,try it ,and then shut down the power valves and see if that helps , if not ,then duct tap over the bellmouths 75% and see what that does .


robert

[robertXX]

i just read this bit again simon ,

(/quote simon megabrain oop nort )

''6 People each suck on a length of hosepipe, each hosepipe sealed to a tin can... Put an airflow restriction on another hosepipe to the tin can and there will be a slight vacuum in the tincan (enough maybe to suck gas out of a reducer). But if only one person sucks on their hosepipe at a time and all the others let the pipe fall out their mouth between sucks, no vacuum in the tin can. With a manifold, engine valves are at one end of each pipe and the tin can at the other while the people are not sucking... there is still a vacuum in the tin can all the time. Without a manifold, there is a really wide whole (mixer venturi) at one end of the other 5 pipes... Not much vacuum in the tin can (pipe between reducer and venturis).''



and i had not seen your point before , each cylinder ,can suck on the its copper pipe , but if the other cylinders are not sucking as well then it can suck on all the openings in the globe , only two of which have gas flowing out of them .

but then ,thinking about it ,what happens with a twin 40 webber or delllorto setup , hould not the same be true there ?


eg




which doesn't seem to have all that small a venturi


or this ..



interestingly the one above ,from brc , has inserts to speed up the air and give a stronger draw ..



or this ..






i suppose a drastic reduction in globe volume might help ,and that would be easy to do with some resin.

on the other hand , having it running on what i assumed was the bypass tickover bleed flow in summer ,would suggest that interracial cross sucking was not happening sufficiently ........and that was at a very very low engine rpm and gas average draw .

hmmmm.

[LPGC]

it's one thing keeping up with all progress on someone else's project which we're updated on sometimes bi-monthly

Wasn't criticising you Rob!

but then ,thinking about it ,what happens with a twin 40 webber or delllorto setup , hould not the same be true there ?

Good point, agreed the same would seem to be true. Have never personally seen these mixers fitted on engines without a manifold though, bit vague on this but I seem to remember years ago somebody mentioning they could be a pain on engines without a manifold (eg twin 40 side draughts on a Pinto engine), might have been Dai...

I do think there'll be some validity/effects from the 'sucking on straws' point. Another way of visualising the effect, maybe over simplifying - Get one vehicle with mixer system running in the yard, T from the reducer/mixer pipe to a mixer fitted on an identical vehicle parked alongside. While both engines are running this should work (particularly where both engines are running at same load) but turning one engine off, the running engine's mixer would now part suck gas from the reducer and part suck air from the stalled engine's mixer.

Just thought of something that does seem weird and does seem in contradiction to the above point though - If you pull the blanking plug off an R90 outlet that isn't being used, this only seems to have the effect of lowering the reducer sensitivity (and obviously making the install unsafe as gas can come out the unplugged pipe connection). The engine will still run just as it did with the blanking plug on after only a minor adjustment to reducer settings! Remembering this has made me think Dai's suggestion of running both reducer outlets to globes might be more effective than I previously thought.

Regards petrol carbs, some of the type referred to here are in effect discrete carbs per cylinder when fitted to an engine without a manifold. If they functioned as one carb feeding two cylinders then the effect on petrol still wouldn't be as pronounced as for a similar LPG mixer setup - petrol venturi effect is a bit different to the process which has LPG vapour flowing into a slight vacuum (half covering a petrol carb air inlet won't effect mixture nearly as much as half covering an LPG mixer) and there's no chance of air flowing backwards up a petrol jet to equalise pressure to the other venturi.

Even on petrol carbs without manifold, achieving smooth engine idle has traditionally been more problematic than with a conventional manifold carb setup. Thinking back 25 years, usual issues for mates fitting side-draughts were fitting too large a carb in the first place ("look at this Sime, twin 48's on this Pinto with fast road cam, goes great at high rpm, just won't idle well and uses loads of fuel" - "Swap the carbs to 45's or better still 40's, lose 2bhp at 6000rpm but regain low rpm tractability and economy"), too large carb jets, too wide inlet trumpets. Large jets were often fitted to get around the real issue, sometimes low air flow not providing good enough venturi effect at the jets due to oversized carb, got to be a 'suck' signal on petrol or LPG.

Simon

[robertXX]

so in the hunt for a engine that would drag itself higher than 800 rpm .....


i refitted the vapouriser i had taken off , and rigged up a pump and a bucket of hot water , the pump pushed hot water into the bottom of the 1st vap , then out of the top of that to the bottom of the 2nd ,then out of the top of that to the bucket .this worked well , and i had no signs of freezing or leaking from then on .

then i decided to get a bit more methodical with the fuelling .

i made a grid on a bit of paper , with vertical columns for tickover bypass /sensitivity screw/main flow valve,comments . down the side i had test number .

this made it much easier to remember where i was in the tuning process .

i fixed the idle bypass at 1 turn open ,then tried different settings on the sensitivity screw .all done with the main flow valve shut . i then opened the flow valve 10 turns ,and tried it with 3 turns on the sens screw. this seemed a little bit better , and so i leant down from my seat and wound the rear engine sensitivity screw out 9 flats , so 1 and a half turns , so it was now at 4.5 turns , the front was still on 3 turns ..

this was what happened next ..


https://youtu.be/yQO53pQUIXI


regards

robert

[Gilbertd]

That sounds effing gorgeous!! I'll be home sometime tomorrow night so will get that R90E in the post to you on Wednesday so you'll have two decent ones.