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Over on the Book of Face, Chris Riley has bought a box of Pi bits, that include an interesting, but puzzling mod.  The work has been expertly done, but what is it for?

The plenum tube has a parallel secondary tube attached, that feeds smaller pipes each entering an intake trumpet.    Clearly something was to be flowed into the charge air.     The extra system is too low pressure and too wide to be fuel, and 'extra air' would be ridiculous, but might be for nitrous, in the 'dry' variety.   No one on Fb has seen anything like it and can't be definite about what it's for.   Can the Sideways Common Room provide an explanation?

See Chris' post at https://www.facebook.com/groups/2709781932574725

Here are his pics, starting with the modified plenum

120970606_787703738458445_3395642807358259599_n.jpg?_nc_cat=107&_nc_sid=b9115d&_nc_ohc=rKQROMHRWBYAX-LPHMQ&_nc_ht=scontent.flhr4-1.fna&oh=853fa30a2ce2d2034ed5cc378bff2168&oe=5FAB8B79

 

Here's a view down the OE plenum:

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And from the point of view of the throttle bodies.

120913902_787703851791767_944781918197473416_n.jpg?_nc_cat=106&_nc_sid=b9115d&_nc_ohc=OmTeKKg0t0wAX-YReUj&_nc_ht=scontent.flhr4-1.fna&oh=0a539c1910f6e7083a677f8d1803d0ae&oe=5FA83512

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Can't see his post if we are not members of the group on this one John. Although I have just requested membership........

I saw this on another group, it was suggested it might be something related to a gas (LPG??) conversion? I never saw anything after that, so lost track.

Phil

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Ah!  Good thing I posted the pics, then!

Yes, LPG a possibility, dual-fuel.   The original car mght have given the clue - tanks and so on - but it was not to be seen, so Chris can't say.    I've no experience of either LPG or Nitrous, so neither can I.

John

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LPG/petrol would need some way of adjusting the timing on the fly, else each fuel change would require a sojourn under t.he bonnet.   Chris has the dizzie  - I've asked if thre isd  any evidence of electronics of other mods.     Of course the project may not have got that far!

AND, a Google search led to the CT site, where one Cliftyhangar, Clive Senior, posted about his Pi LPG project.   No mention of progress, but Clive has posted here before.    You there, Clive?

JOhn

Edited by JohnD
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A lot of the more primitive LPG installs make no provision for timing changes. LPG will take more timing, so if planning to run on mostly LPG, you’d probably just bump the timing up a few degrees and hope you didn’t have to drop back to petrol on a hot day....

 

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Hi John,

It's a long time since I did an installation of what Nick refers to as a 'primitive' system but it seems my old supplier is still in business!  The correct term for what I was describing is a Mixer because that's what it is designed to do - mix the gas and air.

They are all essentially the same design, the difference being the diameter of the ring.  

https://tinleytech.co.uk/product-category/lpg-parts/mixersetc-for-induction-systems/

The picture quality isn't great so I posted the link

Cheers

Chris

 

 

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2 hours ago, Chris W said:

Hi John,

It's a long time since I did an installation of what Nick refers to as a 'primitive' system but it seems my old supplier is still in business!  The correct term for what I was describing is a Mixer because that's what it is designed to do - mix the gas and air.

They are all essentially the same design, the difference being the diameter of the ring.  

https://tinleytech.co.uk/product-category/lpg-parts/mixersetc-for-induction-systems/

The picture quality isn't great so I posted the link

Cheers

Chris

 

 

Mixer rings work well enough when done right.  Not sure many, if any, of those installations catered for timing changes dependent on the fuel in use at the time.  Not sure even all the LPG injection systems do that.  Do you think the "nozzles" would see sufficient vacuum to draw the lpg through Chris?  Not alot of velocity at idle and low speeds.  Maybe nitrous is more likely.....

The more I look at the original pics, the more confused I am about the purpose.  Fairly convinced whatever was going in was gaseous, so candidates remain (most likely) lpg or nitrous.  No sign of any actual metering arrangements for either...... just two blanked off entry points.  Of course, although someone has clearly put some significant skilled effort into it, we don't actually know whether it worked as intended.  Though oily deposits on the tubes do suggest that the engine did run for a reasonably long time while they were present (albeit not necessarily doing anything useful)

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On 10/15/2020 at 10:31 PM, Nick Jones said:

Mixer rings work well enough when done right.  Not sure many, if any, of those installations catered for timing changes dependent on the fuel in use at the time.  Not sure even all the LPG injection systems do that.  Do you think the "nozzles" would see sufficient vacuum to draw the lpg through Chris?  Not alot of velocity at idle and low speeds.  Maybe nitrous is more likely.....

My experience was exclusively with Rover V8s in either Classic Range Rovers or Disco 1s.  You are correct that none of the systems I encountered did anything on variable timing but the logic was to set the timing to be optimised for LPG.  Petrol was only used to warm up the engine (or if you ran out of gas).  In fact with my carbed off roader, I realised that actually the reason for running on petrol at all, was simply to get enough heat into the coolant to stop the Vaporiser freezing so I re-plumbed it in series with the heater, removed the thermostat and then only ran on gas.

Regarding the manifold vacuum, the mixer on the RR carb version was a sandwich plate between the carb an the manifold so similar to John's example in terms of inlet tract length, I guess. The EFI RR had the mixer on the mouth of the plenum.  It did run better and had better MPG but I put that down to being a much lower mileage engine and electronic ignition.

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This is educating me (not difficult, my previous was less than stamp sized) but I read of "dry" Nitrous that uses gas, and "Wet" that uses the liquid, staight from the can.     If(and I am very willing to believe it  - you could tell that a cylinder of Nitrous was nearly empty by the frost on it) that a heated Vapouriser  is needed, then how does the wet system work?  Heated intake manifold?

 

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