LPG with forced induction

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sowen
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LPG with forced induction

Post by sowen » Fri Oct 10, 2014 9:25 am

Having a chat with some friends has got me thinking about supercharging my SD1, I already have a spare supercharger and enough parts to fit one

Image

What I'm wondering about is how well they work with lpg, and whats the best or alternative lpg systems that can handle forced induction?

I've got a complete single point system for efi, I don't want to use it as I was ideally planning on sourcing a multi-point system with no intake restrictions.


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Post by ChrisJC » Fri Oct 10, 2014 6:07 pm

I would go for an OMVL Dream XXI multi-point system. It's the dogs dangly bits. And I think it will run just fine on a blown engine (just check though). It does rely on the underlying petrol injection system being capable of running on a blown engine.

If not, a single-point 'mixer' type LPG system will be fine if connected appropriately.

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Post by sowen » Sun Oct 12, 2014 11:37 am

Yeah, everything I've found so far indicates the lpg copies the petrol system, and explains the single point system I have which has a loom which fits between the efi harness and injectors. I do wonder if with lpg I can within reason pick and choose the parts and only buy what I need to get it up and running, rather than trying to find a suitable donor car/removed system or buy a brand new system which is a long way off my current budget.

I've just blown more money and bought a 4.0 V8 from a P38 Range Rover, and am looking into the options on Megasquirt and how much work is needed to get it to run on the hotwire loom with minimal modifications.
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Post by DaveEFI » Sun Oct 12, 2014 2:34 pm

Remember you'll soon be into problems with a SD1 gearbox if you increase the torque above standard. A bog standard 3.9 is about the limit.

It's fairly straightforward to modify an SD1 loom for Megasquirt. And the MS can go where the original ECU lives - with room left over for a wide band O2 electronics or whatever. I can give you my wiring diagram, which uses the original Lucas wire colours.

You do need to do a mod to the pump relay circuit as it is switched by +12v on the Lucas, ground on the MS. I left mine as per the Lucas way and just added a (small) relay. Only really because of my immobiliser. :D
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Post by sowen » Sun Oct 12, 2014 10:46 pm

DaveEFI wrote:Remember you'll soon be into problems with a SD1 gearbox if you increase the torque above standard. A bog standard 3.9 is about the limit.

It's fairly straightforward to modify an SD1 loom for Megasquirt. And the MS can go where the original ECU lives - with room left over for a wide band O2 electronics or whatever. I can give you my wiring diagram, which uses the original Lucas wire colours.

You do need to do a mod to the pump relay circuit as it is switched by +12v on the Lucas, ground on the MS. I left mine as per the Lucas way and just added a (small) relay. Only really because of my immobiliser. :D
I've got a few spare R380's, when I shorten my spare gear selector I'll swap one over and that should handle the rise in power.

I've got hotwire efi and a spare ecu which I'm thinking of cannibalising to hold the megasquirt ecu inside, and wiring isn't a problem, the cabin side of the loom is still sat on the passenger footwell carpet waiting to be finished!

The lpg side of things still confuses me, I'm getting a lot of conflicting advice and opinions, I think I need to get back to basics to learn exactly how the individual parts work and go from there.
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Post by DaveEFI » Mon Oct 13, 2014 8:45 am

Unless you are desperate to keep things looking original :D there's really no point in fitting MS guts to a hotwire case. Since it comes with its own case anyway. I've done it a few times for others to a flapper case, and it's actually quite a bit of work - far more then changing the connector on the loom. Also means you can't use a Stim easily for testing, and if you decide to upgrade at some later point won't be so easy to sell on.
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Post by ChrisJC » Mon Oct 13, 2014 3:21 pm

There are two types of LPG system, 'fuel injection' and 'carburettor' style.

The fuel injection ones basically sense the signals going to the petrol injectors, and translate them into signals going to the LPG injectors. These are the best, but require a petrol engine management system to be operational all the time.

The carburettor style ones are basically a mixer ring in the inlet tract, and a vapouriser which meters in a certain amount of lpg depending on the air flowing past the mixer ring. These can be fitted to a fuel injected engine, all you do is shut down the petrol system when running on LPG. They are a bit crude, and need to be reasonably well matched (to get the mixture in range). But if you feed the atmosphere side of the vapouriser with the boosted air pressure from the supercharger, it will work just like a blow through carburettor.

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Post by sowen » Tue Oct 14, 2014 10:07 am

DaveEFI wrote:Unless you are desperate to keep things looking original :D there's really no point in fitting MS guts to a hotwire case. Since it comes with its own case anyway. I've done it a few times for others to a flapper case, and it's actually quite a bit of work - far more then changing the connector on the loom. Also means you can't use a Stim easily for testing, and if you decide to upgrade at some later point won't be so easy to sell on.
I was thinking there may be a way to get it to plug into the standard hotwire loom, I don't want to cut the plug off as it's a near 100% working setup apart from a few less than perfect multiplugs. The better option maybe to make a new loom based on the hotwire just for the megasquirt, all new wires and plugs then remove the hotwire once it's adequately running?
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Post by sowen » Tue Oct 14, 2014 10:12 am

ChrisJC wrote:There are two types of LPG system, 'fuel injection' and 'carburettor' style.

The fuel injection ones basically sense the signals going to the petrol injectors, and translate them into signals going to the LPG injectors. These are the best, but require a petrol engine management system to be operational all the time.

The carburettor style ones are basically a mixer ring in the inlet tract, and a vapouriser which meters in a certain amount of lpg depending on the air flowing past the mixer ring. These can be fitted to a fuel injected engine, all you do is shut down the petrol system when running on LPG. They are a bit crude, and need to be reasonably well matched (to get the mixture in range). But if you feed the atmosphere side of the vapouriser with the boosted air pressure from the supercharger, it will work just like a blow through carburettor.

Chris.
If I go to the expense of going Megasquirt then having an lpg system that would follow it would be the preferred solution, I see there are individual parts available to purchase seperately, but I don't know enough about the systems to make an informed decision yet? Is there anywhere on the internet that gives a good detailed description of how the different lpg systems are operated?
1972 Rover 2000TC M16 turbo
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Post by DaveEFI » Tue Oct 14, 2014 12:14 pm

sowen wrote:
DaveEFI wrote:Unless you are desperate to keep things looking original :D there's really no point in fitting MS guts to a hotwire case. Since it comes with its own case anyway. I've done it a few times for others to a flapper case, and it's actually quite a bit of work - far more then changing the connector on the loom. Also means you can't use a Stim easily for testing, and if you decide to upgrade at some later point won't be so easy to sell on.
I was thinking there may be a way to get it to plug into the standard hotwire loom, I don't want to cut the plug off as it's a near 100% working setup apart from a few less than perfect multiplugs. The better option maybe to make a new loom based on the hotwire just for the megasquirt, all new wires and plugs then remove the hotwire once it's adequately running?
I thought the same too when first going MS. To be able to swap back to the flapper if I had problems. But in practice never did.
So getting a spare hotwire loom and modifying that is IMHO the best way. Sure it will take longer to swap back - but if you take care with the installation you won't have to. Many of the problems people have with MS are down to a poor installation. Other thing it's nice to have is a spare inlet manifold etc complete. You can then check the loom fit etc and get it perfect before wrapping - much more easily on the bench than on the car.

Flapper looms are often in poor condition. Hotwire uses a different cable (thinwall) and better heat protection - as well as better injector etc connectors - so can make a very good basis for an MS loom. It's my preferred way.
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Post by sowen » Sat Oct 18, 2014 3:53 pm

I think I'll be starting off with a new loom to suit the megasquirt with RV8 multiplug kit, I already have a few broken multiplugs, so the chances of finding another hotwire loom to cannibalise in good enough condition would be more tricky. That way I leave the entire hotwire efi system as a lump that can be kept on the shelf as a ready to run spare just in case.
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Post by Steven 90 » Wed Mar 22, 2017 3:58 am

ChrisJC wrote:There are two types of LPG system, 'fuel injection' and 'carburettor' style.

The fuel injection ones basically sense the signals going to the petrol injectors, and translate them into signals going to the LPG injectors. These are the best, but require a petrol engine management system to be operational all the time.

The carburettor style ones are basically a mixer ring in the inlet tract, and a vapouriser which meters in a certain amount of lpg depending on the air flowing past the mixer ring. These can be fitted to a fuel injected engine, all you do is shut down the petrol system when running on LPG. They are a bit crude, and need to be reasonably well matched (to get the mixture in range). But if you feed the atmosphere side of the vapouriser with the boosted air pressure from the supercharger, it will work just like a blow through carburettor.

Chris.
I have a omvl vapouriser, can I also give the atmosphere side boost from the blower ? I can only find that this can be done with impco to a max of about 0.5 bar.
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