Kit recommendation - Supercharged Jaguar X308 (V8 98-03)

[markocosic]

Hi all,


I have an X308 with AJ27S 4.0 supercharged engine that I'd like to convert. The kit will need to deliver 370 bhp over 8 cylinders. OEM injection is sequential, the rev limit is 7k, and this is a coil on plug engine.

This will be a DIY conversion. (quality and cost reasons)

I'm after a multipoint kit. Ideally one that largely "tunes itself" by looking at the injector pulses from the OEM ECU and re-creating the equivalent injector pulses on the gas side - leaving the OEM ECU to calculate any trims required. Fuel blending (petrol top-up at high outputs) and starting on petrol are perfectly acceptable, but I would not want a kit that switches completely to petrol at high loads. (momentary lean conditions are bad news in forced induction engines)

Any pointers as to which kits those in the know would recommend/supply? Kits that those in the know would not recommend?

(I'm familiar with the go-lpg/lpginfo saga but wouldn't hold this against the romano kits necessarily - they could be suitable if correctly installed)

Is a pdf of CoP 11 available for less than £32 anywhere? (marko@cosic.org.uk)
http://www.uklpg.org/shop/codes-of-practice/

Thanks,

--
Marko


This is the vehicle:
http://www.ebay.co.uk/itm/270971837769

I'm fairly familiar with the X308s; just not LPG at the minute. Here's the sister car:

[Gilbertd]

Ideally one that largely "tunes itself" by looking at the injector pulses from the OEM ECU and re-creating the equivalent injector pulses on the gas side - leaving the OEM ECU to calculate any trims required.

All modern multipoint systems work like that, the better ones connect to the CANbus at the OBD socket and use that to fine tune even further.

Fuel blending (petrol top-up at high outputs) and starting on petrol are perfectly acceptable, but I would not want a kit that switches completely to petrol at high loads. (momentary lean conditions are bad news in forced induction engines)

Starting on petrol is a must except when the engine is hot and switch over to petrol at the top end is a sign that an inadequate system has been fitted. 370 bhp over 8 cylinders is less than 50 bhp per pot, not a big ask really.

Any pointers as to which kits those in the know would recommend/supply? Kits that those in the know would not recommend?

Any of the AEB based systems (Bigas, Romano, OMVL, Zavoli, etc) will do the job as long as the injectors and vaporiser are rated for the power output. Other than the budget King ECU, they all support OBD connection too

[markocosic]

Gilbertd - thanks!

...the better ones connect to the CANbus at the OBD socket and use that to fine tune even further.

I'd assumed that you'd input the minimum open time/minimum fuel delivery and the flowrate for the OE injectors then the gas ECU would recreate the same flowrate in LPG in a completely open-loop/dumb fashion. This would leave the OEM ECU to "trim" the fuelling whilst totally oblivious to the fuel type - could cause issues if the gas trim isn't the same as the petrol trim.

I'm guessing that the newer gas kits are "polling" the fuel trims over the OBD, then using that to establish the open time/minimum fuel delivery and flowrate for the OE injectors. OEM ECU is still oblivious/trims the fuelling but over time the OEM trim on gas falls to whatever the OEM trim on petrol is. Uber-cunning!

...switch over to petrol at the top end is a sign that an inadequate system has been fitted. 370 bhp over 8 cylinders is less than 50 bhp per pot, not a big ask really.

Ok.

Any of the AEB based systems (Bigas, Romano, OMVL, Zavoli, etc) will do the job as long as the injectors and vaporiser are rated for the power output. Other than the budget King ECU, they all support OBD connection too

Excellent - reading through the AEB material now.

Are there material differences in injectors/vapourisers from the various manufacturers in terms of quality and performance or are they much of a muchness? Two vapourisers, two manifolds, balance pipe - bad plan?

Thanks,

--
Marko

[markocosic]

Revisiting this question:

Starting on petrol is a must except when the engine is hot and switch over to petrol at the top end is a sign that an inadequate system has been fitted. 370 bhp over 8 cylinders is less than 50 bhp per pot, not a big ask really.

Is there anything *wrong* with purposefully switching back to petrol at full chat?

The 50 bhp/pot isn't an issue. I can't find a vapouriser with enough headroom to deliver 370 bhp though - which means doubling up if you'd like to run at full chat on LPG. There's also the issue of exhaust valve seats on these engines* which would be largely eliminated if one switched back to petrol at full load. It wouldn't be switching often either: Almost never when it rains (deploying warp-drive in the wet just sets fire to the rear tyres) and rarely in the dry (the odd overtake, pulling away from a short slip, or dispatching hot hatches). The cost of the fuel used shouldn't be outrageous under these circumstances.

Yes, you could double up and run 100% on gas, but if a "300 bhp" or "350 bhp" vapouriser were fitted and the LPG kit set to revert to petrol at 250 bhp (long before pressure drops) would this cause any problems as such?

*Allegedly - how much of the burning is due to lean mixtures from badly set up systems I don't know.

Any of the AEB based systems (Bigas, Romano, OMVL, Zavoli, etc) will do the job as long as the injectors and vaporiser are rated for the power output. Other than the budget King ECU, they all support OBD connection too

What's the general consensus on the AC AutoGaz / STAG controllers and injectors?

They appear to tick all the boxes functionality wise and the instructions are massively better than those from the AEB based manufacturers.

[rossko]

What's the general consensus on the AC AutoGaz / STAG controllers and injectors?

They're cheap (which is why you are looking at them). They work just the same, but the cheapness encourages resellers to package them with cheap injectors, cheap reducers, etc. If you want to put inadequate kit on, you can, as you've pointed out. Just as you can fit cheap tyres. i wouldn't see either as a good option on a 155mph car £50k car, but it is yours to do with as you wish

I should point out that 50bhp per cyl is not a ridiculous ask, but is an above average task at 7000rpm.
You're probably not going to find an off the shelf kit truly suited to this car, but if you work with a knowledgable supplier they can easily put the right selection together. That would indeed almost certainly include twin reducers.

[Gilbertd]

Is there anything *wrong* with purposefully switching back to petrol at full chat?

Depends who you ask. Some will say it's a perfectly acceptable way of running an LPG system on a performance car, others, me included, would say it's a bodge, a cop out that the system isn't actually suitable for the car. You want a car that runs on LPG, not one that runs on LPG but only at times when it is favourable. It's a bit like saying that you can surf the net using wifi on your laptop but if you want to watch videos on Youtube, you have to plug a network cable in as the wifi isn't fast enough.

What's the general consensus on the AC AutoGaz / STAG controllers and injectors?

They work, and as Ross says they are cheap. I've heard that Stag do make injectors but they aren't imported into the UK so all you get with a Stag kit is a Stag controller and any old vaporiser and injectors that the supplier chooses to bundle with it.

[LPGC]

Done a lot of these supercharged engines in Jags / RangeRovers, kit cars, etc.

Nobody has yet pointed out... You may also need 2 x AEB124's and / or a petrol fuel return - You do need an electronic valve lube system - These bits are on top of any LPG system.

Would fit an AEB based system, then you have the option of petrol addition if required. Most other systems don't allow petrol addition. Someone mentioned Stag. Stag allows full change back to petrol after a certain calculated engine load (which it crudely calculates itself), and it's not a smooth change back to petrol like it is with AEB. AEB allows RPM correction, as does Stag, but it is cruder on Stag. Stag does have the advantage of being truly sequential, AEB only measures injection time from blue wires (first petrol injector on each bank), which means better following of petrol strategy for Stag, but this advantage of Stag is more than offset by AEB petrol addition advantage for this application. Repaired both types of ECU. Stag would need a major re-design to do petrol addition because it uses relays to turn petrol injectors on/off. AEB uses transistors which can switch fast enough to cut petrol injection after a programmable duration of petrol injection.

By the way, someone said King doesn't support OBD connection. It does, you just need to connect the wires to the loom at the ECU connector end. But don't use OBD connection anyway - there's no need if you map it correctly. Many installers use OBD connection as a bodge instead of doing a good job of mapping. This might stop engine warning light from coming on but the mixture can be well out for long periods after adjusting the throttle. To map this application correctly, especially if a petrol return needs to be fitted, involves driving whilst reading fuel trims from a separate OBD scanner. Petrol times may stay the same when you switch between LPG / petrol but fuel trims can shift a lot. OBD connection is usually a cop-out by the installer.

Use injectors that you can at least force fit 5mm injector pipe onto, because then the pipe will fit between the supercharger and rocker cover to reach the correct place to install the injectors. 6mm pipe won't fit through so you'd end up with injector pipes too long.

For this application, injectors must be capable of good flow rates. Injector choice should be considered at same time as reducer. If fitting a reducer that cannot be adjusted to give higher pressures then injector flow rates are even more critical. Engine bay is tight but engine makes over 350bhp and is a supercharged V8. The supercharger might use nearly 100bhp so that 350bhp is actually more like 450bhp at the crank before supercharger losses. In the tight engine bays of these vehicles I usually fit 2 x magic jet reducers - a reducer setup supposedly good for 700bhp (but really more like 600bhp) and these two reducers will fit in the space of a single reducer of most other types. These reducers are only good for 1.5bar so it is very critical injectors flow very well. In these engines I like MagicJet injectors even if they don't look that well made, because these injectors flow very well. If there was more space in the engine bay we might opt for a different reducer setup that would allow more pressure and hence open up a large range of injectors - I'm not giving MagicJet the hard sell! Have also done these engines with KME and OMVL parts for example.

I can supply the system as suggested above (or a different system if you prefer), will give free advice on how to fit, free tech support whilst you fit, free calibration when you've installed it.

Hope to hear

Regards,

Simon
www.Lpgc.co.uk

[markocosic]

Cheers guys.

My take on it is mostly economic. If for £X I can run 50% LPG and 50% petrol then it's worth spending £2X to run 100% LPG. If it's more like 90/10 for £X and 100% for £2X it's not necessarily worth it. Switching back at high rpm/load allows you to use the smaller/slower/cheaper injectors, then going further still and switching back at moderate power would allow a single vapouriser.

What might be a no-brainer on a £75k car that you're about to cover 150,000 miles in becomes marginal on a £3k smoker that you're going to cover perhaps 40,000 miles in before the government price LPG out of existence. (then again, when depreciation is >£7k a year who gives a monkeys about fuel cost and the inconveniences of the LPG kit)

As a bonus, switching back at high loads is "safe" both in terms of mapping (doesn't matter if you stall out lean, matters a lot if you're lean on full boost) and valves. (if they're going to burn, they'll burn when on full boost)


Keeping the butane in gas form must be fun too. Std enthalpy change of vaporization is ~22.4kJ/mol and it boils at -1C under atmo conditions. At 2 bar absolute (a naturally aspirated engine with the reducer set to 1 bar) it'll turn to liquid below 20C. The Jag engine boosts to 0.8 bar nominal so you're at 2.8 bar absolute if you reference the pressure to manifold pressure, so below 30C and it turns back to liquid. Calculator here:

http://www.trimen.pl/witek/calculators/wrzenie.html

Fine in the intake manifold where the air is scorching hot from the supercharger, but I'll bet on quite a few systems you end up with liquid butane in places on boost transitions. (FI needing further "oversized" vapourisers to keep the temp well over 30C at all times)


Back to the kit though:

ECU -

That stag kit is substantially cheaper for what on the face of it does everything that you need. The ECU has all the features, documentation is there, and the software runs well/isn't dongle-ed.

The 300 Premium is the one I had my eye on.
http://www.ac.com.pl/en/produkt/296/stag-300-premium

Wouldn't be buying from the UK distributor - less is lost in translation by Google-translating the factory support forum than if you ask the UK distributor to ask the factory tech on your behalf.

Waiting on a price for the 300 Premium. 300 Plus is £110 inc VAT (ex delivery) though, and there are 4-cyl front-end kits at £260 inc VAT so I should imagine it's around the £150 inc VAT mark.
http://www.autogaz-market.pl/dla-uklado ... onika.html
http://autogas-lpg.co.uk/conversion-kit ... -0355.html


Injectors -

7k rpm gives 17 msec to drop the fuel in if you're not to cheat. Factory injectors are about 440cc/minute and can stuff 15 MJ/minute each into the engine. I've not seen staged injection (two injectors per cyl to give precise load metering and plenty of fuel up top) but it's nothing new or unusual in the petrol world.


The Prins gear looks bespoke and is certainly touted as such:
http://www.prinsautogas.com/en/products ... ctors.html

"Linear flow from 2.5 msec" - implying open and closed in 2.5 msec? Rated to 290 million cycles and carry a 2yr warranty. At 1.25 ohm they're peak and hold affairs. No flowrates quoted (presumably this is "authorised installer only" info) but one would assume that they carry a suitable size.

On paper these look the nicest of all the brands. UK distributor won't sell them to DIYers, but the factory might. (can't buy a kit and blame prins when you fit it wrong, but no harm in fitting their injectors/vapouriser to another ECU as then it'd be somebody else's fault)

Shiniest I could find. Waiting on a price for these.


I didn't realise that nobody sold the AC injectors the UK.
http://www.ac.com.pl/en/produkt/368/ac-w01-bfc

~2.4 msec to open and ~1.7 sec to close - implying open and closed in 4.1 msec? Slow, no? No cycle ratings given but again carry a 2yr warranty. At 2 ohm these will be peak and hold affairs. These flow 120 litres/min with 1 bar across the injector.


OMVL's corporate website is worthless - no specs whatsoever.
http://www.omvlgas.it/eng/prodotti.php#

A 3rd party statement says that they "work down to 2.5 ms" but whether or not they remain linear at those openings isn't clear. I guess no LPG injector is "linear" in the same sense as a petrol injector as your density is all over the shop as the intake MAP goes up and down. (or your pressure drop across the injector is all over the shop as the intake MAP goes up and down - where it isn't manifold referenced.
http://www.lpgforum.co.uk/viewtopic.php?f=33&t=5717

@ £28 inc VAT (ex delivery) for four on a rail with jets/mounting hardware these are cheap as chips.
http://www.autogaz-market.pl/wtryskiwac ... waczy.html

£42 inc VAT (ex delivery) from the UK.
http://www.autogasshop.co.uk/omvl-injec ... -675-p.asp

Simon@LPGC seems to think that these are 'ok' and reading the handful of posts he's made they're all suitably chock full of info:
http://www.lpgforum.co.uk/viewtopic.php?f=33&t=10614


MagicJet gives some specs online:
http://www.europegas.pl/en/Products/Inj ... d,109.html
http://www.europegas.pl/documents/Magic ... h_spec.pdf

~2.2ms to open and ~1ms to close - implying open and closed in 3.2 msec. Something of a middle-of-the-road option at £55 inc VAT (ex delivery) from the UK

http://www.autogas-lpg.co.uk/injector-s ... -0040.html

They seem to have issues with them failing on lpg-forum.pl though.


Vapourisers/Reducers -

KME Turbo Gold "380 bhp" (nominal) @ £80 inc VAT (ex delivery)
http://www.autogaz-market.pl/2232-REDUK ... ALTEK.html

Or the same thing not marked up for turbos @ £64 inc VAT (ex delivery)
http://www.autogaz-market.pl/2232-REDUK ... ALTEK.html

The factory lists just the one and rates it at 320 bhp - hmmm...
http://www.kme.eu/category,sort,33.html

Simon seems to think that these "aren't bad" reducers but also not 380 bhp:
http://lpgforum.co.uk/viewtopic.php?f=33&t=10664

http://www.lpgforum.co.uk/viewtopic.php?f=33&t=10614
Who makes the Magic Jet vapourisers/reducers that Simon mentions in that post above?

Are BiGas Dual reducers actually rated anywhere near the 380 bhp claimed?
http://www.tinleytech.co.uk/acatalog/Re ... isers.html

[rossko]

As a bonus, switching back at high loads is "safe"

Agreed, it's safe if you have an underspecced system. If the system is specced for the job, then it's no odds.

Don't confuse 'valve burning' with valve seat recession? Late Jag V8s are a bit prone to this on LPG, especially the s/c, but I'm never too sure about the earlier ones. You might like to add a Flashlube type system to your shopping list.

Keeping the butane in gas form must be fun too.

There's not much butane in UK Autogas

The Prins gear ... No flowrates quoted

http://www.europegas.net/image/KEIHIN_CNG_INJ.pdf

UK distributor won't sell them to DIYers, but the factory might.

http://www.gasmotion.de/Prins-VSI-Injector
You'll need to offset the shiny against your desire for economy of purchase!
You may also be interested in Hana injectors, which appear to be licensed Keihin copies.

~2.4 msec to open and ~1.7 sec to close - implying open and closed in 4.1 msec? Slow, no?

That's fine for ordinary cars. A great many LPG injectors perform in this league, they are by nature bigger/clonkier/slower than petrol injectors as they handle bigger volumes.

OMVL's corporate website is worthless - no specs whatsoever.

They don't market to end users

I guess no LPG injector is "linear" in the same sense as a petrol injector

Very few; here we're back at the Keihins really.
Doesn't matter much if the software compensates for the known curve. Implication; you really ought to use an injector model supported explicitly by the system software. Mix'n'match parts shopping can go wrong here.
relevant post
http://www.lpgforum.co.uk/viewtopic.php?f=33&t=11088

as your density is all over the shop as the intake MAP goes up and down. (or your pressure drop across the injector is all over the shop as the intake MAP goes up and down - where it isn't manifold referenced.

On a supercharged, it will be essential to MAP reference the regulator. On ordinary cars it is quite normal as well, with only the odd exception (Prins again) where the rail pressure is much higher than more common systems.

Density also varies with temperature (it's a gas) so systems are equipped with gas temperature sensing, rail pressure sensing, and MAP sensing to allow compensation for density and differential pressure variations - you could just about get away without the last, although it's very desirable for transient response.

[billynoband]

It's getting technical now. So speaking as someone who does'nt know very much it would be interesting to see just how good the Stag Premium ecu is. AC certainly boast/seem proud about it.
Has anyone mentioned Matrix injectors yet or the Valtec fast? and does the car really put out that much power but then again do the reducers really handle as much bhp as claimed?

I recon you should go with a UK supplier who is offering support to be honest. Good luck.

[markocosic]

Wow, missed Simon's post - was writing in response to rossko/gilbertd at the time - thanks for all those details.

Switchover with relays is crude - one assumes that the engine will stumble on the changeover so you really don't want to be doing this under load. (that's implemented as an emergency feature not a daily use feature)

I'd use the OBD and laptop to "learn the OEM map" and get the LTFT for the gas reading the same as the LTFT for the petrol then disable the auto-correction on the gas ECU and leave just the OEM ECU to do the auto-correction. (It has +/- 20% authority which ought to be more than good enough) That way there's no danger of the two fighting with each other, or the gas ECU driving the LTFT to zero whereas the petrol injectors actually need a LTFT of 10% for example. Have mapped MegaSquirts from scratch and have rolling road access, just haven't touched LPG before.

The AJ27S has a conventional fuel system (not returnless) so the ECU won't be any the wiser. Injector emulators will be needed. Flashlube - noted; thanks Ford.

5mm vs 6 mm noted. Any harm, other than installation inconvenience, of using solid pipe to the 'nozzle' with a short hose between pipe and injector?

Engine bay space is horrific on the XK but isn't too bad on the XJ. The PAS reservoir flips over forward of the fusebox and there's room for twin vapourisers in that space. Heater circuit and the aux coolant circulation pump are right next door.

Fair bit of room under the central "scuttle cover" too (plastic part with the coolant header tank filler poking through) though that'd be best used to house your ECU and wiring, tapping into the engine harness in the vicinity of the giant multiplug.

http://www.invisibletouchdetailing.co.u ... s/jag5.jpg
http://bringatrailer.com/wp-content/plu ... resize.jpg
http://home.mchsi.com/~jroal/cars/xjr1.jpg

Very valid point on output. The supercharger does eat a substantial amount of the power that the engine makes, and it's fuelled as rich as sin on boost (in the region of 12:1) too so probably drawing what a well setup 500 bhp naturally asthmatic engine would in terms of fuel.

Have dropped you an email but in all honesty, starting to price the additional bits up I'm not sure I'll go ahead. (tax break expires in 2015 and it'll not get that much use before then)

[markocosic]

rossko - thanks for those links!

Proper datasheets but at a cost that's simply prohibitive - I'll cross the PRINS gear off the list...

I realise that OMVL don't market to end users, but I'd have expected to see datasheets on their site. Saves the installer asking the distributor, the distributor scratching their backside and asking the manufacturer, then relaying a garbled message days/weeks later.

Regards linearity, I can't see a "known curve" in any of the software - they're all fudging it with the "multiplier" maps, or offset + multiplier. Provided the ECU will let you choose between Sat and P&H; choose the min open/close times; choose minimum fuel delivery they should be able to run any injector.

I wouldn't fit a system that didn't explicitly calculate the fuel delivered (temp, pressure, and delta pressure across the injector). Fine on an old RV8 where you were just trying to better the performance of a pair of knackered strombergs and LPG was so cheap you couldn't care less about overfuelling, but not so these days. Google translate gas a little on the Polish LPG forums, but as far as I can gather the response of the AC Autogaz/Stag temperature sensor could be better: 15 secs to respond vs 1 sec for their homebrew solutions. Can cause problems when there's a step-change in gas demand; particularly on forced induction engines.

[Gilbertd]

I assume you also like make love standing up in a hammock? You are making this so complicated when it actually isn't and you are making far too many assumptions.

Autogas sold in the UK is normally 100% propane but may have a little butane added in the summer, in other European countries the percentage varies from 90/10 Propane/Butane to 50/50 but it also varies with the time of year. No good having a tank with a large proportion of Butane in it when it's the middle of winter and the temperature is minus 10C!

Switching with relays isn't a problem, it isn't a simple changeover relay. There are options in the LPG ECU software to set a changeover delay so one fuel isn't shut off until the other fuel is being supplied so you don't get a stumble as it changes over. This has been standard since the days of closed loop single point controllers going back to the early 90's.

The petrol ECU does do all the tuning, it has no idea it isn't firing petrol injectors. Let's say for arguments sake that at a certain load and revs the petrol injectors need to be open for 4mS and, with the given LPG pressure, temperature and injector nozzle sizes, the LPG injectors need to be open for 6mS, then the gas ECU intercepts the petrol injector pulses, adds 2mS and fires the gas injectors for that long. That is the function of the map stored in the LPG ECU. If the map has been set correctly, the petrol ECU does not have to alter the long and shot term fuel trims when running on gas, they stay exactly the same. With the OBD capable LPG controllers, IF the STFT starts to wander (due to a different gas mix, wildly varying temperature or whatever), it adjusts the map in the LPG ECU so it brings the petrol ECU STFT back to where it should be. Trying to set it and then turning the auto correction off will just result in a car with LTFT miles out so it runs like a dog when you switch back to petrol.

As Ross mentioned, whatever ECU you buy must be compatible with whatever injectors you buy. The ECU firmware will have a map of the injector characteristics so that it applies the correct durations at different opening times to keep the performance linear. If, as in the thread Ross pointed you at, you are using injectors that your ECU doesn't specifically support, then you probably never will get it to work right.

One you haven't mentioned is BRC. I only bring it up because a friend has the 4.2 litre supercharged XJ8 running a BRC system right up to the red line without petrol addition......

[sijones]

By the way, someone said King doesn't support OBD connection. It does, you just need to connect the wires to the loom at the ECU connector end.

slightly wrong as well, the 4 cylinder version doesn't support OBD, the 6 and above does. (I know, I have the 4 cylinder plastic version)

[rossko]

Regards linearity, I can't see a "known curve" in any of the software

You wouldn't ; in most cases you tell the software what model injectors are fitted, it takes care of them behind the scenes.

Hence the potential difficulties attempting to get Brand X ECU to run Brand Y injectors. Or temperature sensors, pressure sensor, etc. Some software is more flexible in this regard than others. But most systems are sold as integrated solutions and don't need any flexibility outside their own offerings. These are commercial offerings, not Megasquirt.

..before the government price LPG out of existence...

Yah, the nay-sayers have been saying that since at least 1990. The price difference between petrol and LPG is greater now than it ever was, and there is no reason to expect all that to end in a couple of years.
But if you are not doing the miles in the car to make it pay you back within a couple of years, then yes conversion is pretty pointless.

[billynoband]

rossko - thanks for those links!

Proper datasheets but at a cost that's simply prohibitive - I'll cross the PRINS gear off the list...

I realise that OMVL don't market to end users, but I'd have expected to see datasheets on their site. Saves the installer asking the distributor, the distributor scratching their backside and asking the manufacturer, then relaying a garbled message days/weeks later.

Regards linearity, I can't see a "known curve" in any of the software - they're all fudging it with the "multiplier" maps, or offset + multiplier. Provided the ECU will let you choose between Sat and P&H; choose the min open/close times; choose minimum fuel delivery they should be able to run any injector.

I wouldn't fit a system that didn't explicitly calculate the fuel delivered (temp, pressure, and delta pressure across the injector). Fine on an old RV8 where you were just trying to better the performance of a pair of knackered strombergs and LPG was so cheap you couldn't care less about overfuelling, but not so these days. Google translate gas a little on the Polish LPG forums, but as far as I can gather the response of the AC Autogaz/Stag temperature sensor could be better: 15 secs to respond vs 1 sec for their homebrew solutions. Can cause problems when there's a step-change in gas demand; particularly on forced induction engines.

You can buy OMVL from gasit.co.uk.

The new Romano kit is rated at 500hp Don't know where you would get it though.

[markocosic]

Not "love making in hammocks" - more just trying to understand these systems.

Thanks for the advice from all though. I've taken it onboard and ordered up a system, details at the bottom. A couple of notes for others though.

OBD Correction
OBD connection/correction is a setup aid only. It is convenient having all the tables read into the LPG "mapping" software. You turn it off when the system is mapped though. Why?

The OEM petrol ECU is designed to respond SLOWLY to changes in mechanical engine behaviour/performance, but QUICKLY to changes in fuel properties. If you chuck a tank of petrol in that's 5% less dense than normal petrol (a cheap imported blend, or an "eco-fuel" with ethanol or other such impurities in it) then the OEM petrol ECU quickly sees that the fuel trim is off by 5% ACROSS THE BOARD and adjusts the maps accordingly. The same will happen between batches of gas.

If you leave the OBD connected permanently, then the GAS ECU will be changing the mapping on the fly at the same time as the OEM petrol ECU is trying to work out what changed all of a sudden. The fuel trim won't consistently be off by 5% across the board. In fact, the trim will be all over the show depending on which bit of the map you're in and whether or not the gas ECU has already corrected. The poor OEM petrol ECU will be confused as heck and the system will take a long time to settle down.

So I'm with Simon on that one - The OBD connection is useful for setup but not something that should be happening on the fly when in service. You'll get the same answer from Jaguar powertrain guys.


Injector Support
Neither the AEB based kit nor the Stag based kit care which injectors are fitted. Topen and Tclose, fuel delivered, and whether they're driven saturated or peak and hold are all that matter - everything else is fudge factor for your particular setup, and no pre-programmed. Very megaSquirt style.

Other systems may well differ, but the AEB/Stag kit can run anything unless they've deliberately crippled the programming software.


The Kit
I added 30% to my budget to come up with the following:

ECU
The "KING" AEB based system is the cheapest available. I didn't buy it because I didn't like the software or the manuals. Ok if you're doing this regularly and know your way around it, but I'll pay more for a system with well written software and manuals. So I bought the Stag 300 Premium as the next cheapest option. This is crippled in that it can't do petrol blending - so it is imperative that the system can supply enough gas at full chat.

I've gone with plug-and-play Bosch style connectors on the main ECU harness and the injector emulators to avoid making electrical connections on the engine itself.

Injectors
I went with the HANA injectors, as purpose-designed affairs. The only ones to come with a proper spec sheet, they appear both quick and precise. I've gone with remote manifolds, so that I can mount the injectors close to the intakes with short discharge tubes, then longer runners to the manifold.

Discounted the MagicJet kit. Possibly due to being unforgiving of clumsy installs, but I came across far too many tales of broken MagicJet injectors on the Czech/Polish sites for my tastesto go with those.

Discounted the OMVL/Valtek type kit as I don't want to be pratting about with drill bits trying to make a pneumatic valve with LPG-rated seats work as an injector.

440cc petrol injectors work out at 125 litres/minute on LPG by the way - for a naturally aspirated engine. With the supercharging they work out as 90 litres/minute, as the higher intake pressures/reducer pressures increase the density of the gas being injected. These would hit 15 msec injection time (injection time, not opening time) at full chat and sit around 2.4 msec injection time at idle.

I've gone with bigger - 175 litre/minute or "A Green" HANA injectors. These are going to be down at 1.2 msec or so injection time (injection time, excl opening time) at idle which is a little low, but they're absolutely guaranteed to provide plenty of gas at high load/rpms without silly rail pressures.

From experience the Jaguar V8s idle pretty well even when trashed (an engine with 9/9/7/7/7/7/5/5 bar compressions is about as smooth as your average 4-banger) and you can happily pull up to 4 injectors off at tickover without them stalling. Slight fuelling issues won't matter too much. Also as soon as the transmission is in "drive" the extra load pushes the injection times up anyway. Emissions won't be an issue with the cats there, and any economy hit will be irrelevant in use as the thing never sits idling.

The "B Red" type would probably work too, but I didn't want to order twice. We'll see what injection times are like in reality and I'll share those.

Reducers
The supplier had a good deal on the KME Turbo GOLD reducers. There's space for two of these and they have no upper pressure constrains so should work fine.

That little lot was £500 inc the VAT. All the sundries - acres of pipe and hoses and relays and fuses etc back to the tank, and a gallon of flashlube added £200, with delivery £40.

I'll add an electronic flashlube kit for an eye-watering £150 unless there are alternatives? It is an outrageous price compared with what the far more complex LPG injection system sells for. Know any modern EFi mopeds/bikes that have a suitable tank/pump/injector arrangement? Perhaps the 2-stroke dosing injector. It'd want to be about 4cc/minute to run a single one at the same pulsewidth as the petrol injectors, or proportionally more if it were pulsed less frequently. Almost tempting to grab a small tank, pump, regulator, and injector from a small car and hack together a driver for it...

Tank will be a used one. Plenty of ex RPi kit 720x270 Stako multihole filled donut tanks available used and they won't fit most things. If y'all could avoid bidding up the one ending on fleabay on Sunday that'd be great!


More Questions
I'll start a new thread in "tell us your story" with some more specific fitting questions etc. Exactly where the injector nozzles have been fitted successfully. What you've done about the X308's heating circuit to make it suitable for use with LPG etc.

[rossko]

OBD connection/correction is a setup aid only. It is convenient having all the tables read into the LPG "mapping" software.

I think you may be getting a bit hung up with 'tables' and 'maps'. No LPG system reads any kind of table across OBD, they just sniff at engine management trim values and optionally use them to run their own internal equivalent of long term trim.

I'm by nature deeply suspicious of the whole idea conflicting/competing independant trim mechanisms has to end in tears eventually. The car has a perfectly acceptable trim mechanism built in and all that's needed from an LPG installer is to setup right to begin with.

Neither the AEB based kit nor the Stag based kit care which injectors are fitted. Topen and Tclose, fuel delivered, and whether they're driven saturated or peak and hold are all that matter

Well okay, those are the values that define an injector. You don't get access to those parameters on most systems, just a collection of pre-set values to select from by the name of supported injector types.
Most makers only support their 'own brand' and perhaps Matrix, just as Ford ECUs don't have built in support for Subaru injectors even though there is no technical reason they shouldn't. You might well call that crippled, but its ordinary business. Eastern European products tend to be more flexible.
To generalise, if you cross-breed you might be lucky or might not. Many 'own brands' are very similar.

I don't know about Hana on Stag specically, only used those on Oscar.

...HANA injectors. These are going to be down at 1.2 msec or so injection time

I think you'll run into idle stability issues; most petrol injectors would struggle with that, but as you say, we'll see

[markocosic]

Err, attack of the fag packet typo there - that number starts out as 115 litres/min but becomes 175 litres/min further down the page.


I've tidied the injector sizing into a spreadsheet and it pops out as a far more reasonable 2 milliseconds with good idle vacuum/the vapour at sensible temperatures. 1.6 milliseconds if idle vacuum is only 0.5 bar and the vapour temp is -15 C:

http://www.cosic.org.uk/MarkoStuff/lpg/LPG-calc.xls

Note the difference between the correct sizing for the supercharged vs naturally aspirated engines. 440 cc injectors on a nat asp = 125 litre/min LPG injectors; on a moderately boosted engine = 90 litre/min LPG injectors.


HANA spec sheet I've mirrored here:

http://www.cosic.org.uk/MarkoStuff/lpg/ ... uction.pdf

I'm using the A-Type (Green) 115 litre/sec jobbies with 1.9 ohm (peak and hold) coils.



All the new questions are here from now on:

http://www.lpgforum.co.uk/viewtopic.php?f=32&t=11189

[325i]

The system that your fitting is very similar to the one im getting. Stag Premium, Hanna injectors and KME reducer.

Good luck on your installtion.