lpg feed pipe size on 500 bhp engine.

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robertXX · #41 Post by **robertXX** » Fri Jul 17, 2015 9:31 am

haha funny you should say that , i was just showing v there was no pressure on the gauge , then looked away and stopped cranking ,and as i did so she tapped me on the shoulder and said the needles moving , so then i cranked it again , and it got to 40 psi and the plug shot out .

Gilbertd · #42 Post by **Gilbertd** » Fri Jul 17, 2015 9:39 am

That's fair enough then, 40psi on the starter is pretty good for one of those engines at the best of times. In fact, thinking about it from my experience with Jag motors, sometimes you're pushed to get 40psi at 2,000rpm! I've got to remember everything I've learnt over the years about Jags this weekend as I've just picked up another twin engined one. Only this time the two motors are side by side on a common crank, I've got a V12 XJS to play with......

robertXX · #43 Post by **robertXX** » Fri Jul 17, 2015 9:54 am

mmmm yummy , lucas ignition ....

Gilbertd · #44 Post by **Gilbertd** » Fri Jul 17, 2015 10:28 am

and geriatric Lucas bodged fuel injection as it's a '77 car.....

robertXX · #45 Post by **robertXX** » Fri Jul 17, 2015 10:32 am

rip it all out ,and go lpg only on a couple of venturis !!

Gilbertd · #46 Post by **Gilbertd** » Fri Jul 17, 2015 11:25 am

I would if I intended keeping it but as it's a barn find '77 XJS with negligible rust, only 49,000 from new and a wad of paperwork with it, it'll be a tidy it up and flog it on job. Just got to get the electrics working as they should.....

LPGC · #47 Post by **LPGC** » Fri Jul 17, 2015 2:14 pm

Always fancied an XJS. How do you drop on barn finds and such Gilbert?

Gilbertd · #48 Post by **Gilbertd** » Fri Jul 17, 2015 3:20 pm

www.carandclassic.co.uk, click on search and put 'barn' in the keyword box leaving all the others at the default. Currently showing 284 listings.......

robertXX · #49 Post by **robertXX** » Mon Jul 20, 2015 8:11 am

here's a good question , on 4 inch stubs , how flamey will lpg be compared to petrol?

rossko · #50 Post by **rossko** » Mon Jul 20, 2015 10:06 am

You'll have to find out ; there's huge amounts of "all depends" for your unique set up, and I can't imagine anyone else has ever looked. I expect you can tune for flame to an extent, but my guess is they'd be inherently less luminous/dramatic.

Gilbertd · #51 Post by **Gilbertd** » Mon Jul 20, 2015 10:44 am

I also suspect they'll be disappointing. Having tried to set up a set of triple DCOE 45's on an E Type that had been left with the standard jets rather than the ones needed to suit the engine, you can get some pretty impressive flames out of the intakes when it's lean.....

robertXX · #52 Post by **robertXX** » Wed Jul 29, 2015 8:18 am

well after a bit of last minute advice from simon on my pathetic inability to work out what terminal was pos on one of my valves,

we had a bit of a go starting the behemoth..

https://youtu.be/euFDZmGUUCQ

regards
robert.

Gilbertd · #53 Post by **Gilbertd** » Wed Jul 29, 2015 8:20 am

With apologies to Robert for posting this before he does, it lives........

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

However, I would suggest a radiator and some coolant, along with a bigger battery, before it's run for much longer.......

Edited to add that you beat me to it by a few seconds. Nice one!

robertXX · #54 Post by **robertXX** » Wed Jul 29, 2015 3:16 pm

yes gilbert i agree , the rads ,and battery stuff are already in the design , just need to get on with it .

new data from the run up ,is that the engine's,with the sensitiviy screws and flow screws right out , will not take any throttle without dropping down to lower rpm . i am contemplating the idea that the venturi's are to big ,at 32mm , and ,that according to the 7 to 10mm2 per bhp , and 40 bhp per cylinder , i need around 19 to 23mm venturis.

this seems almighty small and limp !!!

i wonder if it would help if i turned up some 22 mm rings on the lathe ,and just pop them in front of my mixers ? bit like those plastic inserts omvl used to do .

it behaved just like a car does on twin webbers when the chokes are way too big .

whatjafink?

i suppose i could do classic swedes idea and connect both top and bottom outlets of the vap ?

any other ways to get more reaction from the vaps ?

robert

Gilbertd · #55 Post by **Gilbertd** » Wed Jul 29, 2015 5:14 pm

I suspect you are probably right. The mixer sold for a standard 4.0 litre Rover V8, at around 25 bhp per cylinder (your 40 per pot sounds a bit optimistic, 240 bhp per engine?) is 34mm and that's feeding all 8 cylinders through the one mixer, so 32mm per cylinder is going to be way too big. You've not got enough suck per pot to get any gas in.

You definitely need more restriction through each venturi to accelerate the airflow and give you more suck.

robertXX · #56 Post by **robertXX** » Wed Jul 29, 2015 5:24 pm

i reckoned it this way gilbert ,

stock power 225bhp for the 3.6 ,and 240bhp for the 4.0.

then researched what happen to the aj6 engine if you stick a tubular exhaust and open inlet on it , and it appears to gain around 50 bhp , so that gave me 275 and 290 for a total of 565 ,then knocked 10 % off for lpg ness.=

508 bhp./ 12 =42.37 bhp/pot ,

so gauging this to be the optimistic high , i rounded down to 40 bhp /pot.

scottyf · #57 Post by **scottyf** » Thu Jul 30, 2015 9:45 am

Just watched the video's. Great work!
Really is a beast.

Whats the end result going to be though?

Gilbertd · #58 Post by **Gilbertd** » Thu Jul 30, 2015 6:21 pm

Read the whole thread http://www.rodsnsods.co.uk/forum/garage/medusa-206057 and you'll find out. Set yourself a bit of time though as it's up to 71 pages now.....

robertXX · #59 Post by **robertXX** » Fri Jul 31, 2015 5:33 pm

it has become a bit of a saga .

Gilbertd · #60 Post by **Gilbertd** » Sat Aug 01, 2015 9:23 am

But well worth a read......

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lpg feed pipe size on 500 bhp engine.

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