Flapper engines and backfires

[bee utey]

OK this is the pics of a major refit I did last week to an '88 RRC with a 3.9 and flapper EFI.


http://www.aulro.com/afvb/attachment.php?attachmentid=41584&stc=1&d=1324035804

Pic shows 25mm angle cut to air cleaner can, in stock position to clear a dual battery. A "sandwich" plate mixer goes before the AFM. A backfire valve goes after the AFM. Intake hoses are shortened to get everything to fit.

http://www.aulro.com/afvb/attachment.php?attachmentid=41585&stc=1&d=1324035804

Another view of the cut off air cleaner can and the shifted power steering reservoir. Bosch MEC723 coil and 024 amp next to air cleaner. Vac reservoir shifted from battery tray.

http://www.aulro.com/afvb/attachment.php?attachmentid=41586&stc=1&d=1324035804

View of Zavoli converter and Gastec FP50-TOW LPG processor.

http://www.aulro.com/afvb/attachment.php?attachmentid=41587&stc=1&d=1324035804

New Bosch ignition leads, dissy cap and Bosch amp conversion connected.

http://www.aulro.com/afvb/attachment.php?attachmentid=41588&stc=1&d=1324035804

Ford oxygen sensor fitted to Y junction before the muffler, best access with the drill without removing the exhaust.

[bee utey]

http://www.aulro.com/afvb/attachment.php?attachmentid=41589&stc=1&d=1324036869

Close up of the intake assembly

http://www.aulro.com/afvb/attachment.php?attachmentid=41591&stc=1&d=1324036869

Pop riveted new tag for 1 clip to suit 25mm off.

http://www.aulro.com/afvb/attachment.php?attachmentid=41592&stc=1&d=1324036869

The upright donut tank I was saving for that special customer, holds 65 litres of LPG.

http://www.aulro.com/afvb/attachment.php?attachmentid=41593&stc=1&d=1324036869

The whacking great cargo area blocking monster of a gas tank that came out.

http://www.aulro.com/afvb/attachment.php?attachmentid=41594&stc=1&d=1324036869

The fried and damaged dissy cap that was part of the blame for the original backfiring, not spotted on a major service by his mechanic. Garbage leads had very loose boots allowing moisture to seep in and destroy the terminals.

[rpo83]

As you can see bee utey, i have been trawling old threads, this morning i pulled everything off before my mixer, what a mess, pipes with unmatched diameters cobbled together to form an inlet path!

134196

I'd like to neaten this whole mess out, and when i saw this refit, i really liked the idea of the sandwich plate mixer...

Would this still be your preferred LPG install on a 3.5 flapper?? or would sequential or vapour injection be worth doing?

I'm happy to change over any components you recommend...

[bee utey]

As you can see bee utey, i have been trawling old threads, this morning i pulled everything off before my mixer, what a mess, pipes with unmatched diameters cobbled together to form an inlet path!

134196

I'd like to neaten this whole mess out, and when i saw this refit, i really liked the idea of the sandwich plate mixer...

Would this still be your preferred LPG install on a 3.5 flapper?? or would sequential or vapour injection be worth doing?

I'm happy to change over any components you recommend...

To install a sandwich plate mixer you also need a matching converter, your Impco one isn't compatible with simple mixers. They do restrict flow a bit but are pretty easy to fit.


I've not fitted sequential vapour injection to a vehicle as old as that, although it should in theory be possible. It would require your petrol system to be running very well first as the gas computer reads the petrol injector settings and translates them to LPG. Given how old and primitive the flapper system is I would be thinking about updating it to a later hotwire injection system first, as fitted to 1991 onwards 3.9 engines. Then you have modern easy to source petrol injectors instead of those horrible hose fed things that leak at the drop of a hat. Once it's all together find yourself a suitable injection kit and fit it. Mind you it would be far cheaper to just rip off the LPG and go back to straight petrol, not sure you'll ever save much money any more on LPG.

[rpo83]

I have searched for sandwich plate mixers and couldn't find anything, is this similar??

LPG Propane Autogas STREAM MIXER - MORE POWER! LOOK! | eBay (http://www.ebay.com.au/itm/LPG-Propane-Autogas-STREAM-MIXER-MORE-POWER-LOOK/320979216695'ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649)

I'm thinking if i can clean this mess up and get it running for not much $$ it will be worth doing to get her running whilst i plan a long term solution.. Could you recommend or even supply a sandwich plate mixer and matching convertor??.. i trust your judgement over most of the people i have spoken to.

[bee utey]

Send me a PM and I'll look into the spares box in the morning.

[DoubleChevron]

THat's a nifty setup. Does it work well in the cold ? I have the OMVL R90 with mixer ring .... It drives me bloody nuts. The thing freezes over when towing through mountainous areas (ie: all of the victorian high country this year). Every long climb we would start leaning out part way up.

it also never flows enough for full load. Wide open throttle from 4200rpm ... will lean out and die after about 3seconds. I could probably just keep cranking the power valve open, but it appears the converter just doesn't flow enough LPG.

Oh, those "high performance" silicon leads. I've just had one of them fail at less than 10,000kms ... maybe 8months age. The boots are nice and tight though. So much so, they are mongrel things to get off without destroying the lead.

I'd be tempted to upgrade and copy what you have done. The biggest issue is the cost of LPG anywhere north of Victoria. It simply makes no economic sense to spend money on the LPG system :(

Another dumb question :) What on earth is the tiny coil that is fitted to that ? is sure does help with the relocation of the air filter house!

seeya,
Shane L.
PS: Should the backfire plate go before the AFM so it doesn't get damaged. Won't the AFM flap be shut ... so it will still blow off the intake hoses ?

[DoubleChevron]

I have searched for sandwich plate mixers and couldn't find anything, is this similar??

LPG Propane Autogas STREAM MIXER - MORE POWER! LOOK! | eBay (http://www.ebay.com.au/itm/LPG-Propane-Autogas-STREAM-MIXER-MORE-POWER-LOOK/320979216695'ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649)

I'm thinking if i can clean this mess up and get it running for not much $$ it will be worth doing to get her running whilst i plan a long term solution.. Could you recommend or even supply a sandwich plate mixer and matching convertor??.. i trust your judgement over most of the people i have spoken to.

Gee's look at the stuff that guy sells. How is he doing so cheaply with free postage ? ( it would cost me more than a lot of his hose fittings are just to send the fitting across town locally). I'm going to see if he has the converter/rebuild kit for my brothers Pajero. It has vapor injection, but it's converter has started to leak. He also has those BLOS carbies. I've always wondered what they would be like.

seeya,
Shane L.

[bee utey]

THat's a nifty setup. Does it work well in the cold ? I have the OMVL R90 with mixer ring .... It drives me bloody nuts. The thing freezes over when towing through mountainous areas (ie: all of the victorian high country this year). Every long climb we would start leaning out part way up.

Freezing up means your water supply is insufficient. Best supply is in series with the heater core, no tee pieces or throttle body hoses.


it also never flows enough for full load. Wide open throttle from 4200rpm ... will lean out and die after about 3seconds. I could probably just keep cranking the power valve open, but it appears the converter just doesn't flow enough LPG.

OMVL converters are a bit variable in quality but should do for a 5 litre V8. There used to be plenty on ebay, just find a clean one and swap it out.


Oh, those "high performance" silicon leads. I've just had one of them fail at less than 10,000kms ... maybe 8months age. The boots are nice and tight though. So much so, they are mongrel things to get off without destroying the lead.

I only fit Bosch or OEM leads if given a choice. Most of what's for sale these days is pretty poor quality.


I'd be tempted to upgrade and copy what you have done. The biggest issue is the cost of LPG anywhere north of Victoria. It simply makes no economic sense to spend money on the LPG system :(

In 2017 I've been pulling off more LPG kits than I've been fitting, way it goes.


Another dumb question :) What on earth is the tiny coil that is fitted to that ? is sure does help with the relocation of the air filter house!

Bosch MEC723 transformer coil, no longer available in that size. OEM Bosch oil filled coil is better quality anyway.


PS: Should the backfire plate go before the AFM so it doesn't get damaged. Won't the AFM flap be shut ... so it will still blow off the intake hoses ?

The backfire protection device is there to protect the MAF from damage, not the other way round. A flapper MAF will twist and jam after a single backfire, sometimes you can unjam them but mostly its a bin job.


He also has those BLOS carbies. I've always wondered what they would be like.

Like a SU or CD Stromberg carby, nothing special about them. They don't address the major cause of backfiring, which is electrical interference between adjacent leads.

[DoubleChevron]

Oh .... Gee's I'm dumb. I was assuming the mixer ring was getting iced up (like my old carby cars do .... all the time ... it would drive you nuts. a lot of the mountains across victoria has that mist hovering off them. my old carby cars used to always ice under those conditions. Usually because mechanics always tore the hot air inlet hoses and ducts off and chucked them away when the cars were new).

It hadn't occurred to me that the converter would be icing up with all the power and heat being generated under the bonnet. I'll need to verify, it's tee'd off from the hoses across the left hand bank of the motor. If that is the case, I bet the converter is icing up under full load as well.

Sorry for the million and one questions. But I always learn lots of stuff when I hijack other peoples threads here [bigsmile1]

Up around Maryborough I was paying 99cent/L for LPG. If my petrol tank wasn't so little, I would have run petrol only through most of NSW and QLD. I also think the tiny tank up in the rear inner guard is killing the fuel pumps (they must run really hot at times). I've had the 2nd one die in the car now (die as in not generate enough pressure to run the car above 3000rpm or with any sort of load applied).

seeya,
Shane L.

[bee utey]

A carburettor ices up because liquid petrol is being vapourised via the venturi, and the latent heat of vaporisation is being drawn from the air passing through it or the heated manifold base under the carby. LPG is vapourised in the thingy with the water hoses, and radiant heat does very little to a device designed to draw heat from the coolant passing through the unit.