Max distance from vap to injectors

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ln69bt
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Max distance from vap to injectors

#1 Post by ln69bt » Tue Jan 01, 2019 8:08 pm

Can anyone tell me would It be a problem if I have say 1.5 meters of pipe inbetween my vap and injectors some for vac lines would this cause a problem

Gilbertd
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Re: Max distance from vap to injectors

#2 Post by Gilbertd » Tue Jan 01, 2019 10:23 pm

I would think it would only become a problem when the injectors get a bit worn and start to leak slightly. They'd slowly lose the gas pressure in the hose so it might make for a rough changeover.
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Re: Max distance from vap to injectors

#3 Post by keith » Thu Jan 03, 2019 1:26 pm

Use mostly solid (copper?) hose for the vacuum connection from inlet manifold to vap.

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Re: Max distance from vap to injectors

#4 Post by LPGC » Thu Jan 03, 2019 1:32 pm

keith wrote:
Thu Jan 03, 2019 1:26 pm
Use mostly solid (copper?) hose for the vacuum connection from inlet manifold to vap.
No, use flexible hose for all pipe connections between the engine and other (none engine) parts of the vehicle. The engine moves and vibrates.
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Re: Max distance from vap to injectors

#5 Post by keith » Thu Jan 03, 2019 1:43 pm

MOSTLY - solid. Yes the engine does move. You'd find it very hard to join copper directly both ends.
Mostly solid, a little flex will likely be required both ends and possibly a little joint in the middle.

But you have my interest Rich - what solid hose do you know that will not compress or crack over 1.5m unsupported? Are you imagining tank to pump fuel hose?

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Re: Max distance from vap to injectors

#6 Post by Gilbertd » Thu Jan 03, 2019 4:00 pm

We don't know what car he is talking about but I would imagine something where the engine bay is a bit crowded and the only space where the vap can be fitted is going to be behind a front bumper or inner wing panel. That could quite easily mean that the hose from the vap to the injectors (mounted on the inlet manifold), especially if run neatly and tied in place (so not unsupported), could get to 6 feet long. My only concern would be that the hose would have vapour sitting in it at 1.2-1.5 bar and could leak away very slowly when the engine is turned off. When it goes to change over, the gas would start to flow from the vap but with the injectors also opening how long would it take to fill a 6 foot length of 10mm ID hose and get it back up to pressure?
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

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Re: Max distance from vap to injectors

#7 Post by ln69bt » Sat Jan 05, 2019 11:48 pm

Sorry its a 2003 range rover 4.4 bmw engine seem someone put it there and he says his runs perfectly under front wheel arch so iv done the same but I'm getting mostly good running good tick over but if I use more than 80 percent throttle It looses all power like the fuels turned off let the throttle a bit and it pulls very well getting engine codes rich both banks and fuel trim-25 No diagnostic lead till Monday

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Re: Max distance from vap to injectors

#8 Post by ln69bt » Sun Jan 06, 2019 1:24 am

Also forgot to add kit I fitted is brc fly sf system black square brc vap it was removed from another same engine range rover

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Re: Max distance from vap to injectors

#9 Post by LPGC » Tue Jan 08, 2019 10:51 am

I expect it would take only around a fifth of a second to re-pressurise a 6 foot length of 10mm ID pipe (this is what I see in the real world and fag packet maths on reducer flow versus pipe volume agree), not that gas should seep away anyway if there are no leaks.. And since there will be a delay of maybe a couple of seconds from the solenoids opening to the system turning off petrol injection and switching to gas injection, gas injection doesn't effect the re-pressurising time.

However, if there was a leak then given enough time (*longer time than all the pressure escaping) the pipe might be just full of air before the solenoids open and then after solenoids have opened would have 1 atmosphere of air in the tank plus reducer pressure of gas above that... the pipe wouldn't just contain gas as it should, it would instead contain gas and air. Since the system only switches to gas when the engine is running (and usually at part load, manifold pressure less than atmospheric pressure) the proportions of air in the pipe versus gas in the pipe after re-pressurisation is higher than the reducer pressure setting would suggest.. 1 Atmosphere of air / versus reducer pressure setting less manifold vacuum of gas. So if the reducer was set to 1.5 bar, manifold pressure at 0.4 bar, after solenoids had opened and after re-pressurisation the pipe would at first contain 1 atmosphere of air plus only 0.9 atmosphere of gas by volume, 1.5 - (1 - 0.4) = 1.5 - 0.6 = 0.9). Since gas is 1.5 times heavier than air there is there is more gas versus air in the pipe by mass than by volume, the 0.9 atmosphere of gas by volume has as much mass as 1.35 atmospheres by volume, by mass the pipe would contain a ratio of 1air:1.35gas which would still make the engine run very lean for a brief moment when the system first switched to gas injection. So lean that the engine might stall if all cylinders were switched to gas at once but most systems these days stagger switching of cylinders to gas, when cylinder switching is staggered (and injector feed pipe starts off containing air) the first cylinders to switch get the leanest mixture and last cylinders to switch get nearest correct mixture, perhaps even correct mixture. A 6 foot length of pipe doesn't contain enough volume to feed the engine for long and the quicker the transition/staggering to gas the quicker the pipe will be bled of air provided the engine doesn't stall. if the engine begins to stall the manifold pressure increases so reducer output pressure increases which then also lifts the ratio of gas:air in the pipe. edit> even to some extent even if no gas is drawn from the pipe.

*longer time than all the pressure escaping - because when the pressure has gone the pipe will at first contain gas at atmospheric pressure, and without a pressure difference between the pipe and atmosphere and only a small leak there isn't much to drive gas coming out of the pipe or air going in to the pipe, with such a small 'seep' leak the replacement of gas in the pipe with air from the atmosphere would be a slow process.

Best not to have any leaks / seeps anyway regardless of rubber or metal pipes... But none of this has bearing on the OPs problem. On a BMW engine'd L322 the reducer siting and water plumbing should be OK if they're below the expansion tank water level and if plumbed to the correct water pipes (in parallel with heater water flow and not using pipes that run to heater matrix's from the water solenoids). The location the OP said should be OK, a lot of similar installs have the reducer mounted above nearside inner wing but below expansion tank level.
Last edited by LPGC on Fri Jan 11, 2019 9:50 am, edited 1 time in total.
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ln69bt
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Re: Max distance from vap to injectors

#10 Post by ln69bt » Thu Jan 10, 2019 10:57 pm

Thanks for the info got mine running well now fuel trim at 3 insted of -25 runs perfect in all revs ect switch over is still a bit ruff unsure why but perfect after iv checked and rechecked that the correct injector goes to the correct petrol injector very impressed with the brc self map system compared to the other kits iv had

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Re: Max distance from vap to injectors

#11 Post by LPGC » Fri Jan 11, 2019 1:31 pm

Glad you've got it sorted.
BRC mapping is very simple but sometimes simplicity is because there isn't a lot of control, they can be more of a pain than other systems if you need to address aspects such as extra injection filtering etc and they can be a bit trickier to calibrate for good trims at idle and good trims off idle if idle petrol injector pulse duration is unusually low or high, none of which will apply to your install.
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