MGZT v6 conversion, question for the experts

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minimutly
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MGZT v6 conversion, question for the experts

#1 Post by minimutly » Tue Oct 08, 2013 3:22 pm

Can someone tell me how to connect the injectors on a MGZT KV6? Can I connect (gas and loom together obviously), to the rear bank as 123, then front bank as 456? O do I need to follow 1front, 2 rear etc? Or, could it be that I need to follow the v6 firing order? The system is a brc sequent 56.
Changing cambelts now, fixed the coolant leak into the valley (there was a lot of antifreeze gunge, and a broken oring!
Finding isues all the time, I wonder how a pro converter would do with such a job, it's only 8 years old and 40k miles, but a simple job this isn't..
I'd appreciate some direction on the injecttor question though.
Thanks,
Huw

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Re: v6 conversion, question for the experts

#2 Post by classicswede » Tue Oct 08, 2013 8:39 pm

does not matter how you go about it as long as you match your cylinders. I usually go 1,2,3 on one bank 4,5,6 on the other
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minimutly
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Re: v6 conversion, question for the experts

#3 Post by minimutly » Fri Oct 11, 2013 10:29 am

Thanks for that, makes perfect sense.
I'm now into day 3 of this job, water leak fixed, oil and filter changed, found my reason for low speed misfire -water in petrol . There were traces in the fuel rails! Cambelts changed (forgot to replace dipstick tube , go back 3 steps and repeat). Fitted spuds, made bracket for vap, put in place and cut water pipes, teed them into vap.
Spent some time last night reading through brc plug and drive manual -engtalian, heavy going, but it looks to be good stuff.
Today will be fitting ecu and wiring, possibly get the liquid pipe run under the car.
Does anyone have any tips for tank mounting? It's designed for bolting through the base of the spare wheel well, I've heard mention of using some kind of pad under it, can I use a kingspan "ring"?
I have real doubts that the m12 bolts (supplied) alone will be sufficientfor 30G, so do I make up a reinforcing plate and bolt through that ?
Still not decided where to fit filler, need to finish with the front end first. Also a bit concerned over the water in petrol issue, if I run on gas the water will stay in the tank, causing havoc. Any suggestions anyone?
Also one other question, I hadn't realised the mgzt is a returnless system, will this cause me a problem? Do I need to fit a return?
Thanks again all,
Huw

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Re: v6 conversion, question for the experts

#4 Post by rossko » Fri Oct 11, 2013 8:34 pm

I don't know what a kingspan ring is. Builders insulation?
There is recommendation to use some kind of resilient mount between tank and body to prevent chafing - a rubber mat will do for a toroid. It needs to be damproof obviously, and non-porous unless you want to create a rust trap.

A single M12 HT bolt takes around 4 tons shear load, so don't worry about those. As you point out, reinforcement of the attachment is what's really needed. As a guide look at the thickness of the mounts the tank maker provides for t'other end of the bolts.

Returnless systems are not a problem of themselves. Feedback controlled types with pressure sensors have issues.
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Re: MGZT v6 conversion, question for the experts

#5 Post by minimutly » Sun Oct 13, 2013 9:34 pm

Rubber mat it'll be then! Just sucked out the water pools from the bottom of the tank -what a sh__ty job that was! Anyone here ever removed an mgzt fuel pump? And the less said about the fuel filter the better....
I've run the tank cables and indicator into the car, so I can put the interior trim back in place.
Tomorrow some cut and shut with the wiring, connect the ecu to the battery and test the comms -exciting times.
Thanks for the replies,
Huw

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Re: MGZT v6 conversion, question for the experts

#6 Post by minimutly » Thu Oct 17, 2013 8:28 pm

Some progress to report!
I fitted the vap, piped it up in parallel, ran the liquid feed pipe to the boot well, with the filter/valve between the subby and the floor. It's in a bit of a tight spot, but without moving it forward I couldn't see where else to put it.
The tank still needs some reinforcing plate under the floor to bolt through, and I may make up some straps to go over the top.
All along on this job I've been concious of "killing two birds" wherever possible - in reallity its more to do with being too lazy/busy to get down to get to know the foibles of my recent purchase. Anyway, the last week and a half has seen me trying to fit the gas kit, whilst also fixing other issues. Today it was the front track control bush - a bit of a bugger it was too. Also today, trying to check if the vis motors were working - that didn'go so well.
So after refitting the inlet plenum, starting the motor and running up to temp, found the only way to get the vap to heat up was to kink the heater hose - bugger! So it was off with the plenum again, and repipe in line with the heater (after checking there was flow even when aircon selected). Sounded easy enough, but getting the hoses off the heater stubs nearly caused me to loose my sense of humour...
Forgot to mention, connected up via the ebay comms lead, set up the ecu and it reads Ok. Need to mount the tank and get some gas asap so I can do some callibrating.
More news soon hopefully.
Regards,
Hug

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Re: MGZT v6 conversion, question for the experts

#7 Post by minimutly » Mon Dec 21, 2015 9:28 pm

Update on this conversion two and a bit years later.
The conversion wasnt easy, fitted a new brc kit, with vaporiser just next to the vis motor on the inlet manifold, the filter and solenoid directly below it, in the line for all kinds of @!## from the road, but its been fine so far.
60,000 miles covered, not missed a beat. I havent serviced it, or changed the plugs. In fact the plugs were the ones fitted when i bought the car, and may even be original, i just gapped them down.
Come the spring i'll need to fit a set of filters, change the plugs etc, anything else I need to do?
As for my first gas conversion, why didnt I do this before?
If the car does another 2, maybe 3 years it will have served its purpose well, covered 150,000 miles, and will be fit for the scrapheap (maybe).
Then i will look at the available options, MG6 turbo, Saab, Subaru perhaps? We'll see.
I heartilly recomend the BRC kit, if you can get someone to sell it to you.
Huw

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Re: MGZT v6 conversion, question for the experts

#8 Post by LairdScooby » Tue Dec 22, 2015 12:24 am

Hi Huw,

little tip for getting rid of the water in the petrol tank - add 500ml to a litre of methylated spirits depending how much water is in there. Although it won't make the water burn, it will "mix" with the water (the scientific word is miscible, i don't fully understand that but basically as i see it it creates an emulsion of water and meths) and allow the water to be "burned off" with the meths. I usually put 500ml into my petrol tanks once a year, just to get rid of the condensation build up. Try and use as much of the "treated" petrol as soon as possible as prolonged exposure to the methanol/meths can cause problems with certain seals although i don't know if those types of seals are present on the ZT/75 - that said in that low concentration i am fairly sure it won't do any harm anyway.
Cheers,
Dave


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Re: MGZT v6 conversion, question for the experts

#9 Post by LPGC » Thu Dec 31, 2015 6:27 pm

The ZT V6 can be a bit of a pain to fit injector nozzles in good locations, site injectors and run piping between nozzles and injectors.. fitting big injectors won't have helped?

Another thing about ZT's is that coil pack ID's A-F don't follow sync with cylinder numbers 1-6 ! So for example, disconnecting harness from coil C doesn't result in cylinder 3 misfire but a different cylinder misfire (I believe coil pack ID's follow firing order but petrol injector ID's follow cylinder number usual fashion). Seems this was enough to throw a few installers (and the supplier of the system) off the scent. One of them had even fitted a new coil pack and new injector on a cylinder where very likely all coil packs and injectors were OK (because they were looking for faults on wrong cylinder). I found that the original installer had trapped an injector pipe, so it would run well at low loads, only misfire at high loads, until I found the real issue and got it running perfectly (for first time since system was fitted which was several years previous) :roll: .

Pleased to read you're happy with results and seem to be a convert. Out of interest, why BRC?

Reading between the lines, maybe you're ready to sell the car now (noted you said 30 months ago your intention to sell in 2 to 3 years)? :P

Any pics?

Scooby, did you just suggest he set fire to his car? Another way to get water out of carpets, seats, trim engine, etc... splash some petrol around the car and throw a match at it :roll: :lol: Another way of getting water out of spare wheel well is drill a hole through bottom of wheel well, perhaps hole could later be be used with a bolt to secure the tank... :roll: Drill, drain, sweep, wipe, dry, wipe, paint, install tank usually works well!

Years ago a customer brought a Jeep in for repair with fabricated petrol tank. 'Just bought it, it runs well on gas once it's changed over but doesn't run very well on petrol' he told me. Later I told him 'That will have been because someone had tried to flush the tank with cellulose thinners, definitely had thinners in there, don't know the ratio of petrol to celly that was in but I drained it and it runs well on petrol now!'.

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Re: MGZT v6 conversion, question for the experts

#10 Post by minimutly » Sun Dec 01, 2019 9:58 pm

Six year update. Car has covered 170k! But I now have an issue to sort. The cold start on petrol is a problem, it cranks and cranks, maybe 20 seconds before firing. This issue started intermittently, so took me a while to check anything. First check was petrol pump pressure - no issues, everything as it should be. Then I noticed, as it got progressively worse, that if I was out of gas the problem wasn't there. Ah, I thought, leaky injector allowing gas into the engine. So I changed all the injectors for new - they had done over 100k at that point anyway. Did this make a difference? No!
So now I'm wondering, could there be a vapouriser issue? But surely the injectors shouldn't let any gas in, nomatter what is happening at the vaporiser? The front solenoid has failed once - could this not be closing? I have just started having flashing lights on the interface under full load - like it's not getting enough gas.
What do you all think?

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Re: MGZT v6 conversion, question for the experts

#11 Post by Gilbertd » Sun Dec 01, 2019 10:43 pm

Leaky reducer diaphragm? If you pull the vacuum line from the reducer off from where it connects to the manifold and put the end in a cup of water, you'll likely see gas bubbling out of it.
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Re: MGZT v6 conversion, question for the experts

#12 Post by minimutly » Wed Dec 04, 2019 5:46 pm

Thanks @Gilbertd, why didn't I think of that. New vaporiser ordered, I'll have the old one apart to check. If it's rebuildable maybe get a new diaphragm for it.

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Re: MGZT v6 conversion, question for the experts

#13 Post by minimutly » Tue Dec 10, 2019 7:20 pm

Tried fitting the new vaporiser on Sunday - I'd forgotten how much of a pig it was to fit. The water and lpg pipes were too short to allow me to get at them. I unbolted the lpg solenoid, but because the kit came with poly pipe and crimp fittings it was impossible to remove without making a new one.
Long and short of it - I pulled it as high as I could and pulled the thing apart - knacked diaphragm and gunged up. So I cleaned the inside with carb cleaner and fitted the diaphragm from the new vap.
To replace the top of the vap I backed off the adjustment, so two problems - what setting to set the pressure to? Second, where the heck is my BRC comms lead.
Update, been driving around a couple of days, it goes OK, but MIL light back on today.

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Re: MGZT v6 conversion, question for the experts

#14 Post by LPGC » Tue Dec 10, 2019 8:48 pm

Set pressure to whatever it was set to before you backed off the adjuster and replaced the seals. You'll need the interface cable anyway to see what actual pressure you're getting now (unless you have a separate / discrete pressure sensor) and will need the cable to see the expected (reference) pressure in software. Usually BRC reducers come preset to either 1.2 bar or 1.5 bar and there'll be a sticker to denote pressure or the clue will be in the reducer model name (such as 1200mb meaning 1.2 bar etc). If you didn't adjust pressure (sometimes involves removing a rubber blank over the adjuster on a BRC reducer) when you fitted the system you can expect original pressure to have been whatever the sticker / model number/name implied. Don't forget that if you're reading pressure using a separate/discrete gauge that the reducer output pressure (when running on gas) will be this pressure less manifold vacuum (so e.g. if you have a 1200mb reducer and at idle the engine has 0.3 bar manifold pressure so 0.7 bar vacuum an external gauge will read 1.2 - 0.7 so 0.5 bar with the engine idling).

On the MIL light (if it didn't come on before) - The LPG ECU will compensate for pressure but if pressure is too low it will mean LPG injectors run out of duty cycle for high load fuelling and/or switch back to petrol when you boot it. By default BRC systems switch back to petrol for dc's approaching 100% but this can be over-ridden in settings. If pressure is set too high it can cause problems due to to gas injectors pulsing below the minimum duration at which they'll meter fuel accurately at low loads (particularly idle) and can be a cause of inaccurate fuelling at around idle and during acceleration and/or changing throttle position, can also cause a problem with cold gas such as just after changeover to LPG. Just having the wrong pressure in itself can cause problems particularly at low loads even if injectors are working well within capabilities, this is because while the ECU's pressure compensation works well at medium/high loads it doesn't account for the difference pressure makes to performance of injectors - injectors are slower to open and close at higher pressures (and vice/versa) and this effect of altering injector performance can offset the need for ECU pressure compensation at low loads, whilst the ECU still applies the full pressure compensation (so too much pressure compensation at near idle). The effects of pressure compensation at near idle conditions depends on how close to the injectors minimum pulse duration they're usually working. BRC's own brand injectors are decent performers but sometimes BRC systems are fitted with GFI injectors which are poor performers.

Also worth pointing out - You should have actual reducer pressure set close to ECU reference pressure (and vice/versa), but if previously you had the 2 figures very different (which you shouldn't) then if you now set actual pressure to ECU reference pressure you could cause the reverse of some of the effects I described above but the outcomes (MIL light etc) would be much the same.

Did the MIL come on before you changed reducer bits? Have you read OBD codes to find why the MIL comes on?

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Re: MGZT v6 conversion, question for the experts

#15 Post by minimutly » Fri Jan 24, 2020 8:39 pm

Simon, thanks for that in-depth explanation, I never got around to measuring the pressure or connecting to the ecu. I bought a 2008 jag xf!
So i have loads of questions on converting this, which I'll start a new thread for.

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