The LPG Knowledge + MS - Thoughts & Ideas Thread

[Hybrid_From_Hell]

OK

Starting this thread - bourne out of the discussion regarding LPG conversions generally, and also in regards to Megasquirt

I'll state now I've not really much knowledge on LPGing V8s it is low,...... other than the LPG needs a hugely differing Advance curve to give performance,

but other than that virtually not much to add

But I have always wanted to know more

so, This is hopefully the thread that will grow

So, for starters.

Can some who know add info to kick off on all any of the following :

What are the "options" regarding LPGing say a V8 and say with the standard Factory system ?

What are the advantages of each system over the others ?

And what are the downsides of both LPG and Lucas LPG'd systems ?

Who has got what system wuith standard Lucas

And what is good bad overall ?

What's an issue(s) ? anyone got round these and if so how ?

Typical costs ? are some system better economy / power both wise than others if so why ?

Who has got LPG with MS ?

Which LPG system and good bad pouints

Whats good with the MS LPG system vs say same with Lucas ?

What are the key issues / failings on LPG conversions ?

Are these the same on say Lucas V MS ?

What would be the perfect set up, and what the issues ?

........Yeah, you get the drift - go for it..

WARNING - Verical learning curve for me and others ahead

Nige

[Ivan]

Nige

Don't know if this will help but I have just had my D3 V8 LPG'd. It has sequential LPG injection (i.e. I have another 8 injectors in the engine.). It starts on Petrol and switches to gas once the engine reaches a certain temp (no idea what it is). The Gas system has it's own ECU and the Engine Management System thinks it's running on petrol. I am assuming the LPG ECU takes over from the Petrol ECU and fools the EMS into thinking it's still running the petrol ECU.

HTH

Ivan

[garrycol]

My 101 is a carbied 3.5 V8 on petrol and LPG - the sweet spot for timing is about 9 degrees BTDC - at this setting there are no issues on either fuel and power does seem similar. Fuel consumption is much worse on LPG but that is to be expected (15mpg on 91 RON petrol vs 11-12mpg on gas). So if you can dual map for gas and petrol that is great but certainly with carbies is not such an issue.

Garry

[zoltan]

This is what I run and have for the last four years:

A 3.5 EFi V8 with MS1 and EDIS and the excellent BLOS propane carb. With map switching I pretty much cannot detect any significant difference in performance between the two fuels.

My vehicle is a factory 110 V8 CSW and I have the RPI Engineering 80 litre do-nut tank in place of the standard petrol tank with a 90 petrol tank under the drivers seat with a home-made filler neck a-la-Series 1.

I get about 62 litres in the LPG tank which provides between 160 and 190 miles range depending on the time of year. Gas seems to go much further in the summer, whether this is the higher butane content or it is happier at higher temperature I'm not sure.

Most of the year I start on gas, it is only when it is seriously cold I will warm up on petrol

[Bowie69]

A second for BLOS for simplicity and reliability, I have fitted one to a mates V8 90, and since then I haven't seen him again, it's running so well he is out having fun in it all the time

Previously it was running a ~34mm mixer ring, which is pretty restrictive on what was supposed to be a pretty well tuned up quad carb ex-RPI (I know I know....) lump, the BLOS is equivalent to around a 48mm choke I think... the difference is very marked, he's convinced it has never run so well. I tuned via a WB lambda dropped into the tail pipe, and it was job done. As efficient as a closed loop mixer setup, but way more drivability. Starts and drives from cold even in sub-zero temperatures.

For sequential LPG, it is as above another 8 injectors fitted to the inlet manifold, bit of a pain to fit, but once done if you don't like it, you can just plug them with small bolts I am sure you can drive the LPG injectors directly with MS, you will need a different output driver I think, as they are low impedance generally, but each one differs... pick the injector carefully!

The difficulty with LPG and MS is that there is a different requirement for LPG warm up enrichment (i.e. it needs NONE, as it is already a gas), and MS only has one WUE table, and it's not switchable between fuels. Yes you can switch the fuel and spark tables easily enough, so that's no issue at all. The only way around this I have worked out is that when you switch to LPG, it fires a relay which interrupts the engine temp sender and replaces the impedance with a fixed value resistor which basically tells MS that the engine is up to temperature, even though it is not. Then, it should be OK....

I have a MJ LPG map which seems to work very nicely... if you wanted it

[Quagmire]

Bowie- your idea on lpg warmup with the resistor is excellent! I was going to just rely on petrol start and warmup with ms switching over at a defined coolant temp.

Am at work at the mo where forums are locked down so will post details of my current lpg setup as well as injection findings/plan when I get home. Posting from a phone is tedious!

[mikec]

Those with the blos system, have you tried a back to back test on petrol with and without the blos? In my experience it wasn't a difference so much between LPG and petrol but the difference in petrol with and without the mixer which was noticeable, obviously with the mixer in the restrictions still there whatever fuel. This was noticed most on my 2.25 that I had lpg'd

[Bowie69]

I have run the V8 with an open plenum, and found little difference to be honest, and I doubt a low revving 2.25 in comparison would be maxing out the BLOS, the carb is a 32mm choke on a Zenith isn't it? In which case if the mixer ring was smaller maybe you would have noticed it, but using a BLOS would have made it unnoticeable IMHO.

[Quagmire]

My setup is currently as follows:

ECU details:

MS1extra (v3 board) running the 11_d hires code and driving Ford EDIS based ignition. Usual trigger wheel setup. Innovate LC1 wideband is installed to monitor oxygen in the exhaust.

Why hires code? You’ll see later.

Engine details:

Engine is a standard 3.5 running at 9.35:1 compression. 10 bolt heads and 3.9 cast manifolds. 3.5 efi cam fitted,

Engine has run on LPG for 99% of its life since I rebuilt it in 2008, doing my daily commute of 65 miles a day- here is what it looked like inside a couple of months ago- clean huh?

Petrol injection & air:

Fuelling is provided by a Flapper style top end with resistors .(Prior to efi it had SU’s.)

Fuel is fed from the standard 90 side tank with an extended metal top Range Rover fuel pump.

Cold start idle control is done via the simple flapper style air valve (currently unpowered and relying on engine temp alone to close). This works well, as I have a 1200rpm idle at cold, dropping to 850rpm when warm. I do have a bosch PWM valve, but have never fitted it.

Air filter is a Range Rover one, mounted on top of the engine, similar to how a 50^th anniversary 90 is setup. My IAT sensor is in the inlet end of the air filter box and although temp does rise when stationary, it soon drops off again when moving.

LPG details:

I first fitted LPG when I still had the original 2.25 engine in the car. I opted to fit it way back when petrol prices first hit £1.20 a litre and the refineries were blockaded. Seems that the nation has now resigned itself to getting done over every time we fill up now…. But that’s another topic altogether.

Currently I have a 60 litre tank in the rear. This feeds a Bigas M84 vapouriser through 8mm plastic pipe. The vap is tee’d into the heater hoses for its coolant supply. Gas is fed into the engine via a 34mm mixer ring on the Plenum throat. This is the restriction I want to get rid of!

I used to have closed loop control on the gas via lambda feedback controlling a stepper power/economy valve – but this system died a while ago and I haven’t bothered to replace, opting instead to tune manually with the wideband and leave as is. This is a compromise at best as if I tune for correct mixture at WOT, I end up to rich on cruise, and if I tune for lean cruise I end up lean on WOT etc.

Economy- I get around 14-15 mpg at the moment on gas. This was previously higher with the closed loop control.

I do notice a drop in performance on gas, and put this down to my being unable to get the fuelling exactly how I want it – I can only get down to around 13.1:1 at WOT if I want to keep the fuelling reasonable the rest of the time. This may be my vapouriser though – it is 6 years old!

Also, it is *much* quicker with the flapper setup than it ever was with carbs, so I think the difference between fuels is more pronounced than it was before.

When I switch between fuels using the LPG switch the MS swaps fuel and spark maps automagically. The ve table when running on LPG is for now simply a table full of zeroes.

So what do we need to think about with LPG injection?

As others have pointed out the key things to remember with LPG are:

1. On cold startup you do not need to enrich- the LPG is a dry gas already. In fact you may need to do the opposite and lean off as a cold vaporiser will generate much richer mixtures than a hot one. The leads onto the next point…
   
2. LPG mixture is apparently much more sensitive to temperature changes than other fuels. If your coolant temp is going up and down, so will the temp of your vap- and hence your mixtures will see-saw to some degree.
   
3. LPG mixture will change as pressure in the tank drops off.
   
4. LPG injectors are generally low impedance. – good if you have flapper injectors, a little more work needed if you have modern injectors (generally high impedance).
   
5. LPG injectors do not generally react as quickly as petrol injectors – they take longer to open and close.
   

So what do I think can be done about these things?

1. Use Bowies excellent idea of switching the temp sensor feed for a substitute resistor of a certain value until the car is actually warm.
   
2. Use o2 correction to keep mixtures in check.
   
3. Again, use o2 correction to control this for the most part – and use a pressure sensor connected to enable MS to switch back to petrol when pressures are deemed too low. Getting this threshold value may be a bit trial and error. I need to find out whether it is safe to use a standard MAP sensor as already fitted to the MS to measure pressure in the LPG fuel rail. Pressure is apparently either 120 or 180kPa normally depending on the kit used.
   
4. Use Jean Belangers “Peak and hold” boards to allow a single MS to drive both high and low impedance injectors without the need for PWM. See jbperf.com.
   
5. Research your choice of injectors fully to get the best spec you can – I will also be using the hires code to try and tighten up on open and close times, helping maintain more accurate fuelling. With the Peak and hold boards, I am not bothered by the loss of PWM control on injectors when using this code variant.
   

So where have I got to?

Hires code is installed and running.

LPG injectors purchased and sitting on the shelf....

I have a later manifold to fit so I can use a wider selection of petrol injectors.

The plan is to drill and tap this for the lpg nozzles (dont want any swarf in my engine), blank them off for now and fit it to the vehicle. I will keep the current LPG setup and retune the petrol side of things with the new petrol injectors.

When I am happy that this is running well I will then swap the LPG mixer ring for LPG injection and see what happens!

[Bowie69]

Excellent post, just wanted to pick you up on a couple of things in this bit:

So what do we need to think about with LPG injection?

As others have pointed out the key things to remember with LPG are:

1. On cold startup you do not need to enrich- the LPG is a dry gas already. In fact you may need to do the opposite and lean off as a cold vaporiser will generate much richer mixtures than a hot one. The leads onto the next point…
   
2. LPG mixture is apparently much more sensitive to temperature changes than other fuels. If your coolant temp is going up and down, so will the temp of your vap- and hence your mixtures will see-saw to some degree.
   
3. LPG mixture will change as pressure in the tank drops off.
   
4. LPG injectors are generally low impedance. – good if you have flapper injectors, a little more work needed if you have modern injectors (generally high impedance).
   
5. LPG injectors do not generally react as quickly as petrol injectors – they take longer to open and close.
   

1. Correct to my understanding

2. I don't think the engine temp is what effects the variation in mixtures, more the gas temperature, which is why on injection systems they have a small temp sender in the injector rail, the ECU then compensates for this

3. LPG pressure shouldn't drop off as tank empties, as this is what the vaporiser/reducer is for, to maintain a semi-constant gas pressure, otherwise you would run rich on a full tank, and lean on a nearly empty one, I've not experienced that at all.

4. Agree fully.

5. Have also read the same, you may need to adjust the 'dead time' in MS (I think that's what it is called on the fuelling page) to a happy medium between the two injectors, or just let MS get on with it when you tune using a lambda, maybe some more thought needed here....

Oh and yes that is a lovely clean inside to an engine

[Quagmire]

Just to explain my thinking on a couple of points further (posting from phone again so apologies for any cock ups- its keeps changing "coolant" to "violent"

2- was thinking coolant temp effects vap temp and so may affect gas temp?

3- I was thinking more of the point reached as the tank literally runs dry, not so much over the whole tank. On my mixer ring setup this comes on quickly being fine one minute and then perhaps having to switch over 2-3 mins later. I want to catch this condition and change back to liquid gold without flicking a switch.

[Bowie69]

2. Possibly... hmm perhaps rather than monitoring the coolant temp monitor the gas temp as this will have more effect on the LPG injector opening times?

3. See what you mean, it is very quick I agree. Sequential systems automatically switch when gas pressure is lost due to an empty tank, and it is a good safety feature -if anything is wrong, it switches back to petrol, you will need to duplicate this safety somehow... Not sure how you will do this with MS, unless it can take two MAP sensors? I confess modifying MS is something I haven't really played with even the thought of doing it, so would probably require input from some of the MS gurus on here.

[Quagmire]

Was planning on having map sensor external to ms, and just feeding an input from it to the ms (through the appropriate circuit). Will post up more details tonight if I can .

[Laptom]

I just turned my RRC 3.5 into a MS beast. Fully liking it, also on lpg with mixer ring (60mm). Only no want more, and that is lpg injecting.

My thoughts were a bit simpler. Why not using high impedant injectors and using the normal petrol circuit? Only need to fool the temperature input like descriped above and then changing the 2nd VE table accordinally (longer open times, tuned on the lambda).

What am I missing on this?

[Bowie69]

Gas pressure variations due to temperature mainly, and the safety aspect of it all.

[Quagmire]

Sorry for the delay in updating. Right, so using the below circuit you *should* be able to add another input for MS to read (usually used for things like oil pressure, fuel pressure etc):

http://www.msextra.com/doc/ms1extra/MS_Extra_Datalog_Manual.htm#addgauge

So if I have a MAP sensor monitoring the LPG injector rail I can feed the output of that into the MS using the circuit above.

Then the MS can trigger one of its outputs based on the readings seen from that sensor - so at the point that the tank is about to run out and pressure falls away.

Then all I need to do is build a circuit to act as a series of AND gates - probably with a bunch of transistors so that the LPG is only armed when:

1- Coolant is up to a given temp (or alternatively this could be forgotten if a resistor is used in its place and therefore bypasses the warmup problems described in point (1) above.

2 - Pressure in the LPG rail is high enough (solenoids would have to have been opened to allow pressure into the rail before the injectors are triggered).

and finally:

3- The fuel changeover switch is set to the LPG position.

Then when all these conditions are met the following needs to happen:

The positive feed to each set of injectors needs to change across.

The map switching pin needs to be earthed so that the MS begins using the LPG spark and fuel tables.

Simples!

[Quagmire]

Oh yes - need to find out if I can use a standard pressure sensor to monitor the LPG or if I am likely to create a large smoking crater by doing so.

Thoughts anyone?

Thanks!

[Bowie69]

I'd look for an LPG one if I could TBH.... EXTERNAL to the ECU

[Laptom]

Gas pressure variations due to temperature mainly, and the safety aspect of it all.

Why?

Gas presure should be solved by the lpg system itself. Safety is still in the regular lpg system (not running = no lpg).

MS is still only needed for ve and ignition mapping. I strongly suggest to keep the safety part outside MS.

[Quagmire]

EXTERNAL to the ECU

Definitely!

[Bowie69]

Why?

Gas presure should be solved by the lpg system itself. Safety is still in the regular lpg system (not running = no lpg).

MS is still only needed for ve and ignition mapping. I strongly suggest to keep the safety part outside MS.

I think the whole point of this is to remove a very expensive component of a sequential LPG system -the ECU, which are hundreds of pounds to buy new, when you have a moddable open source ECU already attached to the truck, why fit a second one? The safety aspect is pretty simple actually, as outlined by Quagmire above.

[Quagmire]

Laptom- I will be keeping the fuel change over switch that is part of my current installation (as it is also the lpg fuel gauge). This switch already shuts off the lpg when the engine isnt running. Everything else *should* be as described... time will tell!

[Laptom]

Quag, that is exactly my point. The fuel switch with safety relay is for the safety part. Everything else (ve+ignition) MS will sort out.

Ignition is the existing part.

Fuel needs some tweaking (cold setup), but with high impedence injectors this should be easy imho.

I will follow this thread, I'm really interested in everybody solutions!

[Bowie69]

The other safety aspect I was talking about is when the tank runs out, rather than having no power and scrabbling for the hidden LPG switch it ought to be done automatically....