BRC Self mapping issue

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blinkinink
Posts: 4
Joined: Fri Aug 11, 2017 11:22 am
LPG System: BRC Sequent
Car: Saab 9000 turbo

BRC Self mapping issue

Postby blinkinink » Fri Aug 11, 2017 11:28 am

Hi All,

sorry to just intrude and ask questions like this off the bat, but i'm having trouble with my BRC mapping.
My Saab 9000 2.3 turbo runs ok in general on LPG, but recently had an additional petrol ecu remap for some top end power (260bhp > 275bhp)
Car was originally set up on gas at 260bhp, so it's not much out but i wanted to do a fresh tune on the LPG to make sure it was running sweet and not too lean up top.

Anyway, using the BRC Sequent software, I am able to do all functions as usual, but when I go to self map, it goes through the 6 step mapping cycle, but gets stuck on the 4th or 5th one and won't go any further. It usually cites the MAP sensor reading as not being within the required numbers in order to proceed. These are out of my control and all other elements (engine speed, loads and whether its on petrol/LPG are all I can control).

So i can only assume that something is up with the Map sensor readings? or that it's looking for the wrong data set based on another setting.
Has anyone got any experience of overcoming an issue like this and where to start, as it's all a bit foreign to me now and I've reached the limitations of my lpg system knowledge.

thanks in advance for your help

blinkinink
Posts: 4
Joined: Fri Aug 11, 2017 11:22 am
LPG System: BRC Sequent
Car: Saab 9000 turbo

Re: BRC Self mapping issue

Postby blinkinink » Fri Aug 11, 2017 11:32 am

Also, not to confuse issues,

but I had the option/availability to fit a newer Plug and Drive Sequent ECU to the system, as this has the better mapping refinement software.
it's the same ECU connections etc, but when i plugged it in, in place of the Sequent ECU, it was just dead with no response on the system at all.
Is it the case that these are not swappable as there is another hardware limitation that prevents this?
Or is it likely that the ECU itself may have been dead?

I don't have another to try instead sadly.

RussellBell
Posts: 1
Joined: Wed Oct 04, 2017 4:49 pm
LPG System: Ayrshire
Car: Audi RS5

Re: BRC Self mapping issue

Postby RussellBell » Thu Oct 12, 2017 4:16 pm

I've never heard anything like this happening. I'd be interested to hear an explanation as well.

blinkinink
Posts: 4
Joined: Fri Aug 11, 2017 11:22 am
LPG System: BRC Sequent
Car: Saab 9000 turbo

Re: BRC Self mapping issue

Postby blinkinink » Fri Jan 19, 2018 2:01 pm

Holy thread resurrection batman!

Just by way of update and a new question.
I did manage to get 1 good self learning cycle out of the ECU eventually so i left it at that and went about my day.
It works, and for the most part it's ok, but there's a serious amount of power lacking from the top end on it.
How do I go about adjusting the higher rpm injection, or should I be using petrol enrichment to supplement during high load/power pulls.
Also, on a modernish engine like that in my saab, should I be looking to use Spark Advance in any way at all or will that all be controlled by the Petrol ECU which is reading O2 and knock etc?

blinkinink
Posts: 4
Joined: Fri Aug 11, 2017 11:22 am
LPG System: BRC Sequent
Car: Saab 9000 turbo

Re: BRC Self mapping issue

Postby blinkinink » Fri Jan 19, 2018 2:03 pm

Also,

what's all this about LPG having an octane rating of 100, and yet people talk of LPG conversions expecting a reduction in power or at best matching the original power output. Surely with that octane, you should be able to map for more power?
is it a heat issue? or a mechanical limit of the hardware in terms of flow rates etc?

Lpgc
Posts: 7
Joined: Tue Jan 07, 2014 6:18 pm
LPG System: I'm an installer!
Car: All-Vehicles

Re: BRC Self mapping issue

Postby Lpgc » Thu May 24, 2018 9:24 am

You've said you have BRC Sequent... Is that correct or is it Sequent24 / 24MY07 / Sequent 56 / 56 MY07 / Sequent Fast / Fastness / etc ?

Various versions don't use a runtime map sensor but need a map sensor to be connected during calibration. The error message you're getting during auto-calibration is likely because you don't have the calibration time map sensor connected (and probably don't own one).

The different spec ECUs are not pinout compatible, a PlugNDrive ECU won't work with the loom for most other BRC systems.

Simon

Lpgc
Posts: 7
Joined: Tue Jan 07, 2014 6:18 pm
LPG System: I'm an installer!
Car: All-Vehicles

Re: BRC Self mapping issue

Postby Lpgc » Thu May 24, 2018 9:34 am

LPG does have a higher octane rating than even super unleaded. Don't confuse octane with power though.
Octane rating points to the anti-knock properties of the fuel, which generally dictates the compression ratio you can build an engine to have to run on the fuel. A higher octane rating doesn't mean higher power unless the engine can take advantage of the better anti-knock properties of the fuel.

Some engine management systems do automatically take advantage of higher octane fuel because they have knock sensors and advance ignition timing to the point just before knock occurs, more ignition advance can make more power.
Some turbo'd engine management systems allow turbo boost pressure to reach a level just before knock occurs, these engines can make a lot more power running on LPG than on super unleaded because the higher octane of LPG will mean the engine runs at a higher boost pressure.

If the 2 points above are not relevant to the engine in question it might make a little less power on LPG because LPG produces less heat when mixed with air at the correct chemical ratio compared to petrol mixed with air at the correct chemical ratio. The correct ratio for a chemical reaction which sees none of the original chemicals remain is called the stochiometric ratio, this is air/petrol 14.7:1 for petrol or 15.4:1 for propane. From the ratios we can see that not only do you get less heat from a given amount of LPG than petrol but also for a given air intake the engine won't be able to bur as much LPG as it would petrol.


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