lpg feed pipe size on 500 bhp engine.

[robertXX]

oh that's good gilbert they are the odd sized screws. yup re the bleed , i have only had to use it on a engine with a lot of cam overlap and the natural low tickover vacuum .

[rossko]

Are your multiple mixers fed from a gas rail common to the two vaps? You might get more idle stability by deliberately setting up a mismatch, so that only one vap is doing the low demand work.

How you plumb that lot together bears some thought, and probably experimentation. I have a feeling an oversize rail (to act as a gas plenum) might be beneficial.

[robertXX]

yes rossko , i thought that too , , 15mm down from the mixers to a 22mm rail or even a 28. this makes the idea of a bronze head being used as the reservoir more viable . i now have a 15mm pipe bender ,and a load of snaky copper twisting out of a head seems just basically JUST RIGHT !



re the vap feeds, i was going to make 2 separate 6 cylinder feeds in parallel., and see how that works, i do like your idea of a two staged system , it would be worth a try if a simpler system won't work.

[classicswede]

Sounds like you have the right version of R90's for the job.

I would suggest using both outlets of the R90's as this doubles the pull on the diaphram.

I would go with the copper pipe manifold and put your inline adjusters between the reducer and teh manifold. 2 x 6 cyl manifolds would be the way to go. Tight bends restrict the flow a lot so I would suggest at least a 22mm rail if not a a little bigger.

The other option that would flow a little better would be a small bulb with 6 outlets almost in line with your 2x19mm inlets. OML.srl do produce somethig like this for use with webber carbs

[robertXX]

cleaned up the vaps a bit ..







the next q is , is a reservoir this big going to ruin all hope of a decent response?

the idea is to cut the top off and fit a fitting in the bottom from the vap , then 6 fittings in the crown snaking out ...






what do you reckon ?

robert.

[LPGC]

I still haven't read the link, my thoughts on the last few posts...

Already been said that rail volume may affect response etc, to maybe help visualise that simple maths can be used to calculate pipe/rail volumes from length and cross sectional area and then to put these in terms that we're more used to... Say you use a 22mm rail that's 500mm long with gas outlets to mixers for cyls 1 & 6 at each end and other gas outlets for the other mixers at points along the rail.. in terms of volume the furthest mixer from the inlet would be the equivalent of 750mm of 19mm vapour pipe further from the inlet than the nearest mixer / with a 28mm rail the furthest mixer would be the equivalent of 2178mm of 19mm vapour pipe further away than the nearest mixer. If someone on the forum asked for thoughts about their install having a pipe length of over 2metres between reducer and mixer, the overlong pipe length would be pointed out as less than ideal for response (and other) reasons, but it would work and perhaps to the driver might not seem any different to a much shorter more normal length. If the gas inlet were in the middle of the 28mm rail, the effective difference in pipe length between edge mixers and middle most mixers would only be around 1 metre. Total pipe length would be any of the above plus the pipe between reducer and rail, the thinner rail of course giving a figure closer to what we'd usually expect on a mixer setup. Might have already been thought about, I dunno!

Any piping/rail arrangement will be a compromise between response time for individual cylinders, response times for cylinders as a group and for each cylinder getting equal mixture. Seems to already have been implied that a wider rail could give more equal per cylinder mixture but with slower response and vice/versa. I think any of the ideas could work but each will have it's own set of compromises. To me it would seem the bomb method, if done well, might work out better in terms of per cylinder balance (with equal 'normalised' pipe lengths to each mixer) and would expect combined bomb and smaller diameter mixer branches volume to be less that that of the big rail, probably less than the smaller diameter rail, so combined / average response times would also be quicker.

What the above doesn't address is gas flow at the very small pressures and hence high gas speeds involved,
the bomb or either rail method could be better in terms of cylinder balance in this respect. Have read enough on head porting etc in the past to know about at least air moving un-intuitively at high speeds taking on some 'sticky' characteristics... I'm not sure if that would be relevant here but if it is it could even mean some of the further cylinders from a gas inlet on a rail could un-intuitively get the most gas and run richer. These days supercomputers can give insights into gas flow of a cylinder head even before it is produced but not long ago head development was all done by experimentation (ported a few heads myself with good results but I let such as David Vizard put in the leg work regards the experimentation)...

Not sure what such as David Vizard would make of this, but given the 'oh yes' factor to the bomb with snaking shiny pipe method and the nature of the overall project, you might choose to try that first! Sorry for previously mentioning injection... even if at a stroke it might involve neater piping, equal cylinder response and mixture, have none of the doubts now being discussed and be turbo ready it wouldn't look as good as what you've said!

Simon

[robertXX]

thanks simon, nicely put !

globes now stripped and polished , fittings made for feeds , now to mount the snakes ....er .. if you know what i mean .

[classicswede]

This is pretty much what you want

http://www.lpgshop.co.uk/magic-6-output ... mp-sensor/

[LPGC]

thanks simon, nicely put !

globes now stripped and polished , fittings made for feeds , now to mount the snakes ....er .. if you know what i mean .

Sounds great Rob! I keep telling the girlfriend to strip, polish bombs and mount the snake

Simon

[robertXX]

Hahaha oh Simon !

[robertXX]

only went and got my vapourisers and globes in place.....:yes:






and got a rough bit of piping sorted .....







bit rough and unpolished/smoothed... but i can do that later ...tell you what ,short bits of copper pipe are hard to bend by hand without kinking them .


robert.

[robertXX]

hi chaps ,

i got the engine A's pipes done , a little more flamboyant this time,








then polished up the engine B set ..



and beaded the pipe ends ..





then mounted my door knocker ..er simon , just NO ok !










i am trying to decide whether to paint the globes satin black or leave them silver.


i now have the 60 l full toroidal ,unfortunately its a 6mm fitting .and has gas in it ...so i will run to my 6/8mm converter ,then 8mm all the way up ...and split to the two 6mm. if its a prob , i can buy a new multivalve then ,when the tank can be empty .


i wonder if there's a calc for bhp limit ... all the valves appear to have a Nm3/min flow rating .

... the rate of flow must vary depending on line pressure .eg the pressure differential of using a mixer ,and so the gas going from , say 165 psi tank , to 15 psia ish at the mixer ,as opposed to 30 psia + on a injected system , will have different line pressures and so different flow at the valve ?


hmmmmm!

[Gilbertd]

It's not so much pressure as volume. Pressure out of the tank will remain reasonably constant except at extremes of temperature but it then goes into the reducer/vaporiser. Whether that drops it down to near atmospheric in a mixer system or twice that on an injected system is irrelevant, it's how much vapour is required by the engine. A tiny feed pipe wouldn't have any affect at small throttle openings when not much flow is required, it's only when the volume of gas being consumed by the engine exceeds the amount that can flow through the multivalve/feed pipe that it would cause a problem.

[robertXX]

It's not so much pressure as volume. Pressure out of the tank will remain reasonably constant except at extremes of temperature but it then goes into the reducer/vaporiser. Whether that drops it down to near atmospheric in a mixer system or twice that on an injected system is irrelevant, it's how much vapour is required by the engine. A tiny feed pipe wouldn't have any affect at small throttle openings when not much flow is required, it's only when the volume of gas being consumed by the engine exceeds the amount that can flow through the multivalve/feed pipe that it would cause a problem.

gilbert , reading this ,the thing i'm trying to get at is , if the vap is giving the gas to the engine
at approximately atmos,then the pressure differential across the vap is tank pressure on one side , and atmos on the other .

if its supplying a inj system , then its tank pressure on one side ,and inj pressure on the other .

both of these situations are going to affect the line pressure once at maximum tank flow rate ,and hence flow rate of the tank valve ?

[LPGC]

True that you get more of a pressure differential with a mixer system (reasons you said), and the greater differential allows more flow to the reducer, so effectively you can get away with more flow restriction with a mixer (sometimes able to run a smaller diameter pipe feed)... If the tank was at 7 bar and a sequential system ran at 6.9 bar you would need a much better feed to the engine bay, wouldn't work at all in freezing conditions...

Love the medusa heads! Have you checked the engine runs OK with the setup? Might be an idea before doing much more trimming and polishing mate...

Simon

[robertXX]

simon , thank you ,no i have not run the engines yet , i'm putting it off by polishing everything ..

[robertXX]

bit of progress..


















and tried a pokeyer battery ...seems to be much better ...


https://www.youtube.com/watch?v=kIEIFm2nz7M




now wiring and a blast suit , and i'm ready to make flames (or not run at all)



robert.

[Gilbertd]

Robert, been following the progress on the rods n sods forum, it's just a shame you weren't videoing things when the oil gallery plug shot out......

[robertXX]

i know ,your right gilbert , but , on the other hand , it was a true test of love that my vancouverite girlfriend veronica , immediately stuck her manicured hand over the hole in the block to stop the oil gushing out .GOOD GIRL!!

[Gilbertd]

You've definitely got a keeper there but it does beg the question. How come you got so much pressure in the gallery that it blew the plug out but didn't show anything on the gauge? sounds to me like there's a blockage somewhere.....