Running on petrol

[Lpgbm]

Hi

I have a 4.8 e53 on brc genius max

When on lpg my petrol is still going down at roughly 15% of lpg usage

Is this setup to rum on both

Still waiting for my cable to arrive to check

Or cluld i have a leaky petrol injector issue

Car runs fine

[Gilbertd]

It may be set up to inject some petrol under acceleration or at higher revs or, it could be that the gauge is being driven by the trip computer. Is it actually using petrol or is the gauge dropping showing you it is using it? On some cars the gauge doesn't read from the float in the tank. It will take a reading when you fill up and then use the data from the trip computer to calculate how much it thinks you have left and the gauge shows that and only reset when you open the flap and fill up again. It wouldn't surprise me at all if a BMW uses something like that rather than keeping it simple.

[Lpgbm]

Definitely reading the tank

Have checked with diagnostics too and got the litres it was before and after

I think it must be using fuel under acceleration although this was driving it very gently

Didnt feel any switchover if it did at a certain rpm

[LPGC]

BRC Genius Max tells us the type of pressure reducer, what is the model of BRC ECU? When was it converted?

Have you been checking the switch to see if it's indicating that it's switched to gas?

The 4.8 BMW engine features Valvetronic, which means it can run in a mode in which there is no manifold vacuum (instead throttling is done by engine valves). Some BRC (and other system) ECUs are by default setup not to switch to gas below a certain amount of manifold vacuum (the idea being not to switch to gas during periods of full throttle on a normal engine), so if yours is setup not to switch to gas unless there is manifold vacuum it might not switch if the engine soon switches to Valvetronic mode after being started. There are other settings (depending on model of ECU) that an installer could play with to see that the engine won't run on gas (will instead run on petrol, even if the switch shows running on gas) in one mode (Valvetronic) or the other (throttled)... And some installers have particular issues getting an engine to run properly in both modes. Further reading on the following link on the latter aspect, though not directly related to your problems but does describe Valvetronic issues viewtopic.php?p=110027#p110027

[Lpgbm]

Im not sure of the ecu yet i need to remove the cover as its well hidden

Install was done 4 years ago or so

I dknt even think this has a map sensor i dont see any vacuum hoses going other than the reducer one into the intake pipe after maf sensor (does this make any difference that its not directly screwed into the manifold)

The system i believe is rated at a max of 280 bhp from research on the reducer but car is 360

Does this indicate that it must have some sort of petrol addition as car feels fine on power

Yes it indicates switchover to gas and stays that way

[LPGC]

No map sensor, so as you correctly imply the LPG system has no way of detecting manifold pressure anyway, so couldn't be refusing to switch to LPG (or switching back to petrol) when manifold pressure is at atmospheric pressure. This also gives a bit of insight on which ECU's could be fitted. There could still be other things (settings etc) going on though that in effect mean in switches back to petrol in throttled mode (since the reducer and gas pressure are vacuum referenced, gas pressure will be lower much of the time in throttled mode than it would be in Valvetronic mode).

The Genius Max reducers are under-rated at 280bhp... But in normal driving you probably wouldn't use more than 280bhp often anyway?

Most ECU's can be set to switch fully back to petrol above certain engine loads (bit like petrol injector duration x rpm, find the peak, engine load is then calculated as a percentage of peak), some can be set to do petrol addition to become active above/below such calculated engine load, rpm, petrol injector duration, etc.

Like you've already said, you best bet will be to wait until you've got the interface cable and software setup, then watch readings to see what is going on.

Good call by Gilbert, though as memory serves X5's (and BMW's in general) use real time measurements from the petrol tank for the petrol gauge... but my memory could be wrong!

[Lpgbm]

Okay that clarifies that the setup must be done correctly so far.

I guess i mean if powering on then you would be using the cars full power in which case i assume the correct way you would set it up is to switch to petrol or have a petrol addition as the reducer is unable to supply full power from lpg?

I have some timw to wait for the cable so will be interesting to see the setup

[LPGC]

I meant the reducer itself is under-rated at 280bhp, I expect it will be capable of flowing more gas than 280bhp's worth.

Answer your question with another question... When you think you've been using petrol do you reckon you've been booting it and using more than 280bhp's worth? Would the times you've been using more than 280bhp equate to running on around 1/3rd petrol as you thought? Would expect you to be booting it a lot for that to be the case. If the car is 360bhp and petrol addition were to cover the difference in 360-280bhp that's only 80bhp worth of petrol and only during booting it, or it could switch fully back to petrol and use 360bhp worth of petrol but only when booting it.

The interface and software should give more insight.

[Lpgbm]

So this is driving it very sensibly mostly and staying within speed limits hence why its surprising to see it drop

No way it would have used that much petrol for just cold starts

Need to change the spark plugs amd will run om petrol to see if economy improves amd then gas too

Will be cleaning petrol imjectors too in case they are leaking which im hoping is the case rather than having to see the fuel drop because of the setup

[Lpgbm]

Still waiting on cable

But having driven some more i dont believe it is using extra fuel when driving normally

I think it is actually just using that much petrol on each cold start pretty sure must be close to 0.6-0.8litres which if you average out a few times is pretty much 10 quids worth in recent prices. So the needle moves down noticeably after a few days

And if driving a bit spirited then its using petrol

[Brian_H]

Note that if the changeover temp is set higher that it should be, or if some of the other cold start settings are set to delay switchover, that you might use a fair bit of petrol then as well. Any idea how quickly it actally changes over/what temp is shown at that point?

Poor coolant flow to the vapouriser might also cause similar late switchover.

[Lpgbm]

The car warms up pretty quick

From a start let it idle say 30 seconds and drive off. Within a mile or so it switches over in current weather temps

Will see what the switchover temp is and would probably use 20-25 degrees as currwntly id imagime its 35-40 degrees

But with the engine being so large it must be using a fair chunk from cold regardless whilst its on "choke" as olden days cars would

[Lpgbm]

Got the cable and downloaded sequent 24

I can connect to the ecu but get some odd readings

Most things are blank once read

Switchover temp for example

If i enter any values it doesmt really save and crashes

Level sensors for eg are all 1000%

Any ideas

Tried sequent 56 and sequent pkug and drive but they say not compatible with this ecu

[Lpgbm]

Okay as i thought i think im using the wrong software

Checked the ecu and its a brc fly ecu

Downloaded brc fly and it diesnt connect on diagnoais page and doesnt actually look like it has any settings ti change anyway

Selected com port 1 still nothing

Anyone know whuch is the correct software to use for BRC Fly SF 8 cylinder Compact Ecu. Only one i can connect with is Sequent 24 but it diesnt oick uo the settings properly

Tried Sequent and it doesnt connect. It says communication ok but then disconnects when trying tk load anything

[Brian_H]

If it says fly on the ECU I'd expect the fly software to be the correct one to use. Are you sure the com port 1 is correct though? Have you checked device manger in windows be be sure that its been assigned com1?
Run Devmgmt.msc should tell you, expand the ports section and see whats there?

[Lpgbm]

The fly software is slightly odd it diesnt seem to have setting for anything like temo switchover or mao etc

Tried various settings and nothing

Onky one i can get it to connect to is sequent 24 which loads up when you click but doesnt look like the right one as the setting are all blank

I think sequent is the cirrect one but cant connect to it? Cable seems to be working otherwise it wouldnt load and read ecu setting from sequent 24

Baffled

[LPGC]

FLY is similar to PND but I think one of the ideas behind FLY was to have a database of maps that could be uploaded to save the general garage mechanics whom usually installed BRC systems from having to get involved with mapping (or even autocal).

Try all the BRC software you can. There will be at least one version of software that shows all the relevant settings. Be aware that BRC software by the same name can have different version numbers (or for example wording like 'MY07' can make all the difference. I believe that usually PND software works on FLY ECU's.

There's a lot of BRC software available from BRC's website but you need a login username and password to access it from the horse's mouth.

[Lpgbm]

I have tried sequent plug and drive and that seems to show it is connected but everything is bkanked out other than ecu version

Is this to do with licensing

[Lpgbm]

Played around with it cant get it to work. The plug and drive seems like it will work but all the options for selection are blanked out

Seems like licensing although doesnt ask for one

Cant seem to find software online that requirws a license either ither than the sequent 24

[LPGC]

Mick @Foxvehicles (or Google LPGautosupplies and speak to Mick) may give further insights into which software to try.

One version of BRC software that you do need a license for is 'BRC calibration tool' but I don't think that software would be the software to use for your ECU.