StrangeRover wrote:

Removed this.

And added this.

Helps having a spare in the right place, the first time its been there since 2003.

The opposite of what most people are thinking of doing.. But because you think LPG is done for because of MFG? If you wanted me to convert it back to LPG again, I'm fully booked until January ;-)

20mpg at 60mph... At £2 per litre that's 45p per minute and 45p per mile, 1p every 1.3 seconds. Even if there are no LPG forecourts in your area you might be able to get gas delivered to your door, at least in bottles. Bottled gas was very expensive compared to forecourt gas but in the bigger bottles these days not so much expensive at around £1 per litre - and compared to £2 per litre and when delivered to your door... Then decide whether to pump it into your vehicle tank or run directly from the bottle.

Just having a flick through some forums I regularly visit including this one this evening... Too many points I'd like to reply to and not enough time.

So I'll just say that I can easily add several hundred miles range to most LPG vehicles for a few hundred quid by fitting a second LPG tank. Which can make having to drive a bit out of the way to refuel with LPG at decent prices instead of petrol even more worth it.

There will come a time when the only vehicles on the road run on batteries (electric), LPG, CNG or (maybe) hydogen when petrol and diesel are not available. Perhaps too late for most here to care.. But I will be among the last to run a vehicle with an internal combustion engine.

LPG is a product of oil and methane extraction 60% and oil refinery 40%. Oil is needed to produce plastic. While we make plastic or extract natural gas we make LPG. If every forecourt that sells petrol and diesel closes I can still buy bottled LPG. Whilever gas is piped to homes I can run a car on CNG (I can buy or make a compressor and refuel at home). It is possible to make carbon neutral and synthetic LPG, they are available at forecourts already.

I don't mind spending 5 or 10 minutes at forecourts but I would never pretend that a necessary forecourt visit is in any way productive or enjoyable. I would not enjoy spending 30minutes recharging an EV anywhere except at home and a necessary stop for a charge could be no more productive than making a phone call or replying to emails from a layby.

Gilbertd wrote:

Two person job though as it is a nice tight fit through the grommet in the bulkhead so you need one person inside and one outside to help it through.

I have to thread wires through tight bulkhead grommets often, usually by taping to something stiff like a long 5mm drill bit, bit of 6mm copper pipe or brake pipe. Just had a ball-ache doing it on a Porsche Cayenne turbo, mostly because I'd forgotten where the bulkhead grommets were.

Bit of an aside...

When BP, Shell, MFG pull LPG pumps and tanks from their sites what happens to that equipment? Might expect some to appear on Ebay etc but haven't seen any for sale.

Would be nice to have the option of buying some to set up adhoc LPG stations in areas where there'd be demand.

A fella on another forum asked other forum members (all in the NorthEast) if they'd like to club together to set up an LPG site for their own private use so they could all enjoy LPG at cost price. I suggested they'd do better making the site for public use, maybe buy for a lower price if buying in greater quantities, charge a markup price even for investors, run it like a business so investors share the profits... If you have the chance to save £10 on a tank of LPG by not paying a markup, or pay full price at the pump but the pump puts £20 back in your pocket, you're better off doing the latter. The latter also has the advantage of potentially expanding to 2 sites putting £40 back in your pocket.

It didn't happen though, no-one showed interest. That said he was thinking of a site in an area already not too badly served by LPG stations and asked the wrong people whom he showed figures quoted by Calor for setting up new equipment. Stark contrast to the pop-up adhoc LPG stations I've seen in the past in areas like Rotherham, where a few fellas would rent an old bit of land, install second hand equipment and buy-in gas from the supplier that charged the lowest price.

Reminded me about Sweden, my son and his American wife are flying to Sweden on Sunday, must remember to feed their cats while they're away lol.

If some vehicles have both a P0175 (bank 2 too rich) code and a P0172 (bank 1 too rich) code then they may also be likely to flag a P0103 (MAF voltage too high) code. The reason for this is that the MAF gives higher signal voltage the higher the airflow and the ECU should provide more fuelling the higher the airflow. Both banks seeming to have too rich mixture (or both bank1 and bank2 lambda sensors being wrong) is a less likely fault (more than one component gone wrong) than a single component fault of an over-reading (in voltage terms) MAF sensor. That would make sense... But you don't have P0103 you have P0102 which points to under-reading MAF... which makes the combination of your 3 error codes curious - An under-reading MAF usually leads to high positive fuel trims (and lean mixture or under-reading lambda sensor codes). The curious part is why would an ECU give error codes for both under-reading MAF voltage (low airflow) and too rich mixture (from lambda sensor readings) at the same time. I.e. Why would it read low airflow but then supply the engine with what it thinks is correct fuelling for high airflow (more air requires more fuel and vice/versa).

Air intake rates / MAF voltage figures can vary by quite a lot for the same engine power (or idle rpm) if mixture varies. These days we normally assume mixture is correct when comparing MAF readings (and it goes without saying that the engine is fully warmed up).... If mixture is a bit rich the engine will usually need less air than usual to average to maintain idle speed, if a bit lean (or especially a lot lean) or a lot rich it will usually need more airflow than usual to maintain idle speed. Idling with correct mixture on LPG the engine may need slightly less air than idling with correct mixture on petrol and the MAF reading can be a bit lower than it would be on petrol, that's because of a few things such as the better atomisation of the fuel and the vapour LPG taking up volume in the inlet manifold that would otherwise be vacuum when vacuum is a factor in pumping losses, both are real efficiency gains in the relevant respects.

Got to wonder if some aspect of resetting adaptions, or (on the other hand) 'false' learned values during time with failing head gaskets contributed to the combination of error codes.

If in doubt about the LPG setup would advise getting it running properly on petrol before seeing what happens when it's run on LPG.

I see what you mean David @dhallworth.

That's a good advert you've done on LPGForum ;-)

Does the lube system inject lube into the gas feed between reducer and injectors (most of that design/make do but some of the more recent ones are capable of injecting lube into the inlet manifold, where-as the old type couldn't feed into a vacuum)? I would never fit a type that injects lube into the feed between reducer and injectors because you tend to find that the lube fluid all goes out of the first (or lowest) injector it gets to, so you end up with one or two cylinders getting most of the fluid and others getting little fluid. Lube fluid also clogs injectors leading to early injector failures and inconsistent fuelling even before failures (imagine a load of fluid that had pooled in pipes suddenly reaching an injector). I say all this in case it sways you to keep the system and switch to a different type of lube system, though I know that's not likely ;-)

Or.. before fitting the heads could fit some tougher valves?

Simon

BrianH wrote:

It might be worth seeing if Simon (LPGC) shows any interest though I'd guess he would have already been in touch if it was.

Could say I've got a 'nodding interest' but I'm watching the thread more out of general interest than out of interest in buying myself.

I wouldn't normally go much out of my way to buy second hand bits but if the tank is a 720x270 4 hole(?) I'd be interested in that if you were closer... and interest in that might make me more interested in the job lot in case you didn't want to sell parts separately. A long shot for me though, probably wouldn't be up for meeting North of Manchester anytime soon.

Would advise advertising the parts on Ebay and LPGforum, as Gilbert said if the ad is seen by the right buyer they'll pay a much better price than someone like me.

Seems to be turning out great with the smoothly curved response readings etc. Well done :-)

Most OBD systems report airflow in grams per second rather than kg per hour but of course it's simple to convert between the two.

I doubt that in practice readings of less than around 4 grams per second (15kg per hour) need be accurate because below that kind of level the engine would be in over-run no fuel mode, so probably won't need to worry much about matching response accurately for voltage below around 1.1v

Also interesting that from the maf readings we can work out how many bhp or kw worth of fuel an engine uses just to idle.

Gilbertd wrote:

As you installed it, that's a relief for you then Simon......

Haha yes!

Or at least in a way... It would be an easy fix if it were the LPG system causing it, since it isn't the LPG causing it it could be any of dodgy fuel pump, fuel pressure reg, leaky petrol injector, MAF, TPS, etc etc?

@Morat It'll be reet without an LPG service mate, or since the LPG seems to be working OK you could easily change filters yourself?

For a very basic/latent fuel pressure test you don't necessarily need a fuel pressure gauge... Just depress the schraeder valve when it's been stood and see if any fuel squirts out?

It won't be LPG related then :-)

Does is still struggle to start on a morning if you run it on petrol for a while before turning the engine off? If gas leaks into the inlet manifold when the engine is off then when you come to start it the engine gets petrol and LPG instead of petrol and air, such leak is sometimes caused by a leaking LPG pressure reducer diaphragm or LPG injector.

Interesting stuff! I'll be watching this.

In the past I've used pull-up / pull-down resistors to get failing MAF signal voltages something like as they would be for a good MAF.

I've previously suggested (though a while ago and maybe on a different forum) using electronics/micro-controller with AD and DA convertors to make signal from one model MAF match signal from another model MAF.

I know the 0.3125v intervals were just for testing purposes and you'll know that in application you'll need more resolution than 0.3125v intervals... on some vehicles a difference of 0.01v can make a difference to trims at idle and low load airflows. Lots of reference points and then interpolation for in-between points?

Not sure exactly how different intake air temps (and to lesser extents barometric pressure and humidity) will affect things.. In theory both MAFs should be self compensating for those aspects because they measure mass directly but I'm not sure if that's always absolutely true with different MAFs? Would in any case get the IAT reading close to actual (and charge the battery lol) before getting deep into matching the signal voltages.

Expect the lag between voltage reading and KG/hour reading will just be due to update speed of the Nanocom, the ECU itself will immediately react with fuelling changes to voltage changes?

Wonder what the ECU's internal sampling speed is for MAF readings? What will the Arduino input sampling / output voltage refresh speed be? Wonder if there's any difference in voltage ramp times between the 2 MAF's?

I remember tuning firms experimenting with water injection to prevent knock on high boost turbo'd engines again in the early 90's, lots of articles in car mags of the time, kids had it fitted on their modified Escort RS Turbo's lol. I think the general conclusions were no more power to be had but could run a bit more boost without knock. The problem was that if they'd changed other aspects such as lowering the compression or retarding the ignition a bit they could get the same power with less fuel use... and with that in mind most of the setups (on-board water tanks etc) were re-purposed to provide a cooling spray of water externally over the intercooler.

Look at the heat rating for hydrocarbon fuels and there's 2 ratings (a high rating and a low rating). The high rating is the total heat that could be gained if the steam that is produced (steam from combining the hydro bits of the hydro carbon with oxygen from the air to make H2O) is recovered because the steam has re-condensed.. But burning fuel in an engine the steam doesn't have conditions/time to condense before it exits the exhaust so the heat used to evaporate the water isn't recovered because the steam isn't condensed. So engine power is related closer to the low rating of the fuel that is burned (high rating minus the heat that is lost due to turning the water to steam)... but we do get a small portion of that lost power back because the expansion of the steam itself will cause some extra pressure in the cylinder.

My understanding is that the power recovered from steam pressure doesn't outweigh the power lost due to producing the steam... And if we intentionally add extra water to a cylinder (water injection etc) we get bigger losses from producing steam (evaporation has a cooling effect) versus bigger gains from steam pressure in the cylinder but the losses always outweigh the gains.... Unless the boost/compression/rpm/ignition timing condition would usually see the engine knock and the the water injection prevents knock but in that case the engine could probably be re-designed/mapped to prevent knock and still make the same power with less fuel use.

Thermodynamics was invented to make steam engines more efficient but even with today's modern design abilities, insulation and materials it's unlikely they could make a steam engine that runs on petrol as fuel efficient as a modern engine? It takes a lot of energy to produce steam, much of which is lost when the steam engine exhaust ports open, the lost steam then warms wherever it condenses like the opposite of sweating.

Thanks for the response Aragorn, just read it, I've been away (Brighton) for a couple of days.

Tend to find most engines have a bit less oil pressure at idle rpm than just above idle rpm anyway?
Also engines that use an electric fan usually have more of a temperature rise/fluctuation sat idling than those with a thermoviscous fan?

Can see why yours could have the feedback loop.

On said forum people are now talking little end knock. Personally I'm not convinced it's even bottom end related, could still be top end. On other forums for vehicles with a very similar engine (VQ35 but in a different state of tune) they talk of valve clearance issues and valve train noise, I reckon there's a chance it could still be something like that.

Thanks, Simon

I don't want to hijack this thread, seems the concussions have already been made?

On another forum, different make/model vehicle (sorry!).. a guy I know seemingly has a big end knock but this came to be at around about the same time as an overheat situation. So a leading question is, did the big end problem cause the overheat or did the overheat cause the big end problem. Thoughts on this? As some as you will probably expect from knowing me, this is a Nissan VQ35 engine. It isn't as though the big ends are effected by anything much besides oil eh?

Edit - (heh!) and while I'm at it... I've got 2 same model vehicles (Nissan Elgrands) with the same engine. I've already had to swap the engine in one of them (long story but I wrote about it in detail on this forum a few years ago). The same one I did the engine swap in started occasionally overheating, it was loosing coolant and the rad seemed to have a slight leak at the bottom so I changed the rad and thought 'job done' but the same overheating and coolant loss has occurred since... I drove 350 miles towing my caravan last year but had to stop every 50 miles to let it cool down enough to add fresh water. I've not used it much since, when I have it's been fine except for hard top hose. I did a sniff test which as expected proved positive. I now (when I get time) intend on pulling the inlet manifold to make access to plug hole areas easy then pressure (drop) test the cooling system and check to see if I can find which cylinder(s) have a tract to the cooling system. Maybe then if the problem is just on one head I might change the HG on only the problem head.

Years ago a P38 owner I did some LPG work for told me that he bought a 'power increase and drive-ability improving module' from Ebay for his P38 which wired to the maf sensor. It turned out to be just a 5watt resistor and he knew it wouldn't do much. But that didn't stop him buying a few dozen 5watt resistors and listing them on Ebay as P38 power increase and drive-ability improving modules himself, he sold the lot, made a quick tidy profit and had no complaints.

Some of us have already seen this link posted on LPGforum by Avensist https://www.glasgowtimes.co.uk/news/scottish-news/20055908.glasgow-taxi-drivers-forced-off-road-amid-lpg-fuel-shortage/

Whatever the issues are the suppliers are not doing themselves any favours by not keeping forecourts stocked. Situation is a bit like selling air to the crew of a space-station but not supplying them for a few months then wondering why they've got no customers left, they will undermine their own current customer base and potential future customer base... I doubt many more city councils will now be considering allowing LPG converted taxis to enter emissions zones and that will have a knock on effect for the rest of us.

Edit - Not that taxi drivers would want to go for an LPG conversion after the Glasgow situation anyway.

Gilbert, in case you're online but haven't noticed I've PM'd you about a different matter.

Good write up and interesting Gilbert.

If you don't mind me saying - Fuel trims and fuel computer mpg readings can both be effected by the stochiometric ratio and calorific value of different fuels. Exhaust temp from the engine itself can be effected by the type of fuel, the mixture and ignition timing but the cat can generate extra heat itself doing it's job of cleaning up emissions... On vehicles fitted with a cat temp sensor you can see that although exhaust temp may go down with rich mixture (so the input to the cat is cooler) the cat temp can still increase with rich mixture (the cat has more HC's to clean up so the cat can get hotter than with lean mixture). The cat can get hotter anyway if it's got more exhaust gas to deal with because the engine is running under higher load (again more work to do). .