Revamping the hemi lpg system

[Gazzawazzawoo]

Hi all ,bought a 300c 5.7 v8 last year and although ran well on lpg installed by a reputable place it seemed a bit of a hurry job to me (reducer in stupid place so was eck as over manifold , no clips on injector pipes and inlet wasn't even fully bolted down) anyway decided to sort it out and vaporizer was genius max so thought I'd price up seal kits for it then realised it it was only rated to 250bhp so that went out the window too . I've bought and installed an ac stag R03 rated to 450bhp and rerouted everything so just need to recalibrate the Brc plug n drive ecu and wondered if anyone had any advice that may be useful as know it has auto calibration tool in the software , just wanted advice on injection times or gas pressure as r03 is adjustable from 0.8 to 1.6 bar .
Sorry for long post and appreciate any help
Thanks
Gary

[LPGC]

The Genius Max reducer would likely have been preset at 1500mBar (1.5 bar) by the factory and BRC installers don't usually adjust reducer pressure output... So on that basis assuming the injectors fitted are a suitable flow rate we'd expect 1.5 bar to be a good setting for the replacement reducer.

You didn't mention what injectors are fitted but we might assume BRC injectors since it has a P&D ECU and had a Genius Max reducer, still we don't know flow rate (is there a coloured band on the injectors?).

The Stag R03 reducer is a resprayed HL Propan MagicJet Extra reducer lol. They're a good reducer (or at least the proper HL Propan version is) but the 450hp rating is a bit exaggerated where-as the 250hp rating for the Genius Max is a little under-rated. The Stag R03 temp sensor like the HL Propan temp sensor (common LPG system spec 4.7K NTC) might not be compatible with the BRC reducer temp sensor. Some HL Propan MagicJet reducers have pressure adjustable between 0.8 and 1.3 bar, some have pressure adjustable between 0.8 and 1.6 bar, some might go up to 1.8 bar.

Don't try to recalibrate it until you've checked it needs it by monitoring fuel trims. Do the usual checks comparing pinj to ginj to see if pressure and injector flow rates (nozzles) seem OK. Even if you adjust calibration don't reset the ECU or you might lose some obscure settings related to e.g. handling the 5.7 Hemi's cylinder deactivation and cause yourself some problems if you're not familiar with the software.

[Gazzawazzawoo]

Thank you ,yeah I assumed same as magic reducer,genius max seals had gone and removing studs was a nightmare just too soft and kept rounding off so rather than bugger about just replaces it and fits better in relocated spot. Injectors are brc orange and at stock setting pinj was 3.08 ginj was 9.6 , I've adjusted valve and now ginj is 4.2 can't seem to get closer, I should have said that genius was single output to y peice although new reducer does have option of twin feed ,not sure if that would get closer to pinj times or not . Most setting in software calibration seem to be auto apart from map refinement n driveability , not too familiar with orc as last setup I did was on my Chevy and was a millennium ecu , I have backed up current tune too just in case I buggered anything lol
,thanks again
Gary

[LPGC]

The idea is not to try to get ginj to equal pinj, don't make that mistake. The idea is to have ginj bigger than pinj but not by much at idle loads whilst fuel trims are correct. If you have a pinj reading at idle of 3.08 and pinj is 4.2 that's not bad as long as fuel trims are correct. You need to connect a live data scan tool to check fuel trims.

You could fit 5 outlets to an MJ reducer but connecting a 2nd outlet to the reducer won't make any difference at idle, the only difference it will make is when at full load on a powerful engine the pressure at the injectors might be 0.15 bar higher than if using just 1 outlet. I don't like to see installs that use 2 outlets from a reducer each outlet having it's own filter, though I don't mind seeing them using 2 outlets from the same reducer if an H filter is fitted instead of a separate inline filter for each cylinder bank.

Not that it matters but if you originally had pressure set to 0.9 bar (usual preset on the MJ reducers) and the system does need 1.5 bar I would have expected ginj to be closer to 6ms at 0.9 bar not 9.6ms.

Have you checked what you set reducer pressure to and fuel trims?

[Gazzawazzawoo]

Ah right that's my mistake then completely as was told a long while ago to get ginj and pinj as close as possible at idle Thanks ill link the obd tool and check fuel trims and adjust accordingly at present its wide open which I believe is 1.6 bar , I also forgot to add the ecu is basically piggybacking pinj as no lamda connected or obd so only basic data available in brc software .so guessing its relying on stock ecu for all refinement , whereas when I installed on my modified small block chevy I connected everything as ran a custom tune on petrol ecu and was able to refine much easier too.Thanks for all your advice its very much appreciated
Gary

[LPGC]

Your ECU works similarly to most other piggyback / slave system ECUs - Ginj is calculated from Pinj x data from a cell in a look-up table. The table has rpm on one axis and pinj on another axis, the numbers in the table cells are the multipliers, there is a different multiplier for every combination of pinj and rpm and the table (of multipliers) can be modified by autocal and/or by the user. In addition to this table there are also settings for enrichment during tip-in (acceleration) etc and probably some settings relevant to the LPG ECU not seeing an error condition when the petrol ECU turns off fuelling to some engine cylinders (giving Pinj = 0 on those cylinders) which the ECU might normally interpret as a wiring problem or interpret as the petrol ECU turning off fuelling to some cylinders having detected a misfire on those cylinders.

There is no need to guess pressures, pinj or ginj, they can all be seen on screen in data monitoring (which also plots a graph with pinj and ginj on it). There's P1 pressure which is absolute gas pressure, manifold pressure, and delta pressure (which is P1 minus manifold pressure). Delta pressure is the one to look at.

Autocal tends to work a bit better on BRC stuff than on most other stuff but still if you run autocal you might need to get hands on with manual calibration afterwards, especially if you reset the ECU. Since I've just told you about how the system works it seems you're not familiar with tuning LPG systems so it might be better to leave calibration as it is if fuel trims seem OK.

[Gazzawazzawoo]

Thanks and apologies for the delay its been a crazy few weeks. I do understand the concept of the tuning variables and is no different to remapping in other software ive used such as tuner pro to modify other american v6 and v8s ive owned , I was just surprised the installer hadn't utilised the obd but its working so never mind. Ive spent a bit of time fine tuning and refining the map after resetting the petrol ecu and driving for a while to establish new base readings and short and long term trims. I,ve also done the same with the lpg and pleased to say the vap is now at 1.4bar and pinj is 3.08 and ginj is 4.5 - 4.8 and fuel trims are exactly the same on either gas or petrol and overall drivability is night and day difference to the previous setup and tune.
On genius max and previous tune mixed driving on a 50ltr tank max was 165 , I've just ran out yesterday and since new vap and map refinement I had done 241 same driving conditions give or take. the car is so much smoother on both and very responsive on lpg now along with engine temps been lower too.

So just wanted to say thanks again for all help and advice its much apreciated by myself and the hemi lol
Gary

[LPGC]

Great, thanks for letting us know Gary.

Simon