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). .
You can get hydraulic pipes (including PAS pipes) made up by firms such as Pirtek. I've had a few PAS pipes made up by them. Take your old pipe in complete with end fittings, they have a vast range of end fittings on the shelf and 99% of the time will have an end fitting that matches your old ones so have no trouble matching your old pipe.
Most such firms can even come up with pipes to replace sections of AC pipe.
It's a bit alarming to hear about P&O, I don't know all the ins and outs but on first consideration it doesn't seem legal re UK employment law what they're doing. I also see this as likely the end of P&O. Not that it's really relevant or an important factor but I have to wonder if this could also have minor impact on my business, because if people wonder about being able to get their LPG converted vehicle abroad in future (and since they can't take their LPG vehicles through the Chunnel) there's the possibility a minority of customers could be put off LPG conversion.
Gilbertd wrote:
A wet compression test can be inconclusive on a Vee. Ordinarily the oil will seal the rings so if the compression goes up, it's ring, if it doesn't, it's valves. But with a Vee engine the oil will sit at the bottom of the bore so not seal the rings anything like as much. If you put a lot of oil in then the compression will go up anyway as the oil will partially fill the combustion chamber and reduce the chamber volume. I'd say your suspicion of a problem with the stretch bolts is the most likely and the gasket is starting to leak around where one of the bolts is. You'll soon know as it will come undone far easier than the others.
Agreed. Though with a RangeRover you could park it on a banking so the whole vehicle is leaning to one side thus making the cylinder bank to be tested more vertical lol.
I'm not a P38 expert but some general advice...
A poor fit on the intake manifold shouldn't effect compression readings.... You ran the compression check at full throttle anyway.
The compression problem could be valve leakage as opposed to ring leakage, have you tried a wet compression test? If only valve leakage were causing the compression problem and if only a HG problem were causing coolant pressurisation you could fix the problem yourself (whip the heads off etc).
The general advice wouldn't leave you with a top-hatted engine though.
mad-as wrote:
and where are you going to get gas from when Russia turn it off or do you get it else ware? how much of Europe and England get fuels from Russia?
As Gilbert implied, that's natural gas (methane, CNG, LNG) though... As opposed to the LPG we run on.
Been said on LPGforum that recent LPG shortages at forecourts have been due to home heating customers having their home heating bulk storage tanks filled early before price rises, the delivery drivers have been busy filling home heating tanks, suppliers prioritise filling home heating tanks over filling forecourt tanks. But if so many home heating customers filled early then since we are heading into summer when people won't be using as much gas for home heating then home heating customers won't need to refill their tanks again anytime soon so there should be plenty of LPG for forecourts... hopefully!
I filled 3 vehicles with LPG this week so far, had to fill 2 of them at Shell Redbeck near Wakefield because it was later than 8pm and Morrisons kiosk closes at 8pm. Recent price rises at Redbeck for LPG from iIrc 72.9 to 74,9 in a couple of steps. But petrol also went up and is now around £1.65, I also saw a guy taking a pic of the price on the pump when he filled with super diesel, had a look at the price when he'd gone... it was over £1.81 per litre.
Just a bit! 53P per litre would be great these days, I've got used to the new normal of LPG in the mid 70's pence per litre.
I was already booked until September before 'recent events'... Now I'm completely inundated with phone calls, emails, forum messages, etc, people whom are suddenly interested in converting to LPG asap.
Thanks Leolito :-)
leolito wrote:
Hi Dave, welcome to the den of P38s.
A little hijack - Simon very very nice website! I will dig into it when time allows, is packed with lots of info!
Thanks, it's been so long since I've looked at it myself that I've forgotten what I've put on there! I know it looks amateurish and has some dodgy formatting and broken links but I leave it as it is because a lot of people say there's good info on there and because I haven't got time to do anything with it. I regularly get firms emailing me to say they've reviewed it and could bring it up to date or optimise it for Google searches but unless I sat down with them I expect I'd end up with a cut down site that looked like every other LPG firms website. It used to work better with less dodgy formatting but I let someone I know have a go at changing it without changing any of the wording or sections etc, and I think they made it worse than it was before...
Thanks Richard (Gilbertd),
A problem may be that I am fully booked until September at the moment. Been a while since I did a P38 now, would like to do another.
Cheers, Simon
Only kidding with this...