BMW 330i "Sport" mode

[turtle4288]

Hi LPG-lovers

I have a BRC converted BMW 330i which runs fantastically well on LPG and has a very discrete and high quality conversion but occasionally I'd like to have petrol mode available in a quick and slick way...

So my idea is to have the car switch to petrol when I flick the auto gearbox across to "S".

I've found that one of the wires connected to the gear lever is grounded when in "S", so I can use this as my control signal ...

What I'd like to know is, what are the 4 wires to the BRC button? I'm guessing 2 wires are for the button (12V and return?) and 2 wires are for the LED fuel level display, but can anyone confirm this, and help me with which wires do what? Its the circular fuel display with a momentary push button in the centre...

Can anyone think of a nice way of making a switch to petrol? What happens if I disconnect the 12V feed to the LPG ecu? I don't mind how long it takes to switch back, but I'd like a fast switch to petrol.

I'm doing this because it's fun and I like a challenge


Many thanks

Mike

[classicswede]

The last I would want when driving hard is for the system to switch back to petrol. The fact you are asking to do this suggests that the mapping is not right and you have more power on petrol. You would be best getting it running right so you can have fun on the cheap stuff.

[Gilbertd]

Why on earth would you want to? I use Sport mode in my Range Rover regularly because it may be down to almost single figure mpg but when I'm only paying 70p a litre who cares? Why run on the expensive stuff at a time when you are using the most?

[Tubbs]

There should be NO noticeable difference in sport or normal modes on LPG or petrol with a 330 BMW.

[rossko]

Apart from 'me too' for why - what's wrong? ...
I believe the BRC switch/ECU is a serial communications interface and not easy to break into. But that could be one-way for beeps and lights, with the switch part being a simple wire.

[turtle4288]

Thanks Rossko, I'll have to interrogate the switch wires and see what signal they are sending...

A colleague today suggested I mount a micro switch to the lever instead of tapping into the gearbox wiring and risk damage to the gearbox ecu, which is a wise idea. The I can customise the microswitch output to basically press the button for me electronically.

As for something being wrong with my LPG, well I expected that response, and to be honest your fooling yourself if you think some bolted on gas injectors can out-class the 230bhp BMW engineered fuel delivery that arcives 0-60 in 7 seconds in a 1.75 tonne vehicle... (it's a touring)

Don't get me wrong - it only adds about a second to that time but its enough to notice

Besides, why carry around a perfectly good petrol tank and a higher performance fuel system without using it?

Cheers for replys

[Gilbertd]

your fooling yourself if you think some bolted on gas injectors can out-class the 230bhp BMW engineered fuel delivery that archives 0-60 in 7 seconds in a 1.75 tonne vehicle... (it's a touring)

Sorry you're fooling yourself if you think a fairly modest 230bhp needs anything special. The gas injectors won't outclass the petrol ones (although due to the 113 RON Octane rating of LPG, if the engine was remapped and tuned for running solely on LPG, they could) but they should be easily capable of matching them. Isn't the 330i a 6 cylinder engine? That's less than 60 bhp per pot.

Don't get me wrong - it only adds about a second to that time but its enough to notice ;-)

If it's enough to notice the gas system isn't set up right. There should be no noticeable difference between fuels, if there is, it needs looking at and sorting out. Fix the underlying problem rather than trying to bodge your way around it.

Besides, why carry around a perfectly good petrol tank and a higher performance fuel system without using it?

Why carry around a perfectly good wheel and tyre in the boot without using it? For the odd emergency when you need to use it. The petrol is just the same, it's there for the emergency when you run out of gas and the filling station you stop at has a broken pump.

[Tubbs]

Erm, well yes I do actually. As long as it's tuned correctly. And the inlets to the bolted on injectors are correctly positioned.
All highly advanced fuel systems are hoping to achieve is a fine vapour of fuel and air. Unfortunately all it can manage is droplets of fuel and air.
LPG is inherently a proper vapour. And 115 Ron as compared to 95-98 if you run on the expensive stuff.

[classicswede]

A correctly tuned and adjusted system will give close to exactly the same results as petrol. On a 1/4 mile run you will not notice any difference but on the dyno you might see that you have lost 2 or 3 HP.

Turbo engines are a different story as they can make use of the high octane of LPG and a lot of turbo's will make more power on LPG than pump unleaded. The Subaru is one of the best examples of this and the difference is noticeable.

230BHP is a very modest power output tbh and not demanding at all on any half decent LPG system

[rossko]

Before you go to any great lengths, press the button and observe what actually happens in response. A liesurely phased changover doesn't seem to be what you want.

[Morat]

I can't tell the difference between LPG and petrol on my 330i touring. I've tried back to back "runs" switching over during acceleration - but there's no difference.

Get your LPG installation sorted out!

[baz57]

hello I own a bmw 330i on lpg abrc system I do drive the car hard at times and see no need to switch to petrol people are surprised that "its on gas" as I boot it my advice if its not broke don't fix it
Baz

[LPGC]

I will add my two pennies worth!

Turtle started out by telling us how powerful his car was. Everything is relative and many of us convert cars that are over twice as powerful as a 3L BMW on a regular basis. A 3 litre BMW may seem powerful to someone who is used to driving 1.6's around but will feel slow to someone who is used to driving a performance V8 around or maybe even a 2L turbo, and then there are the V8 supercharged vehicles etc.. After wanting more powerful cars etc as someone interested in cars growing up, and after driving many hundreds of different vehicles, there comes a point when you see every car as a compromise and a 3L BMW as somewhere in the middle power bracket, a run of the mill model, not really powerful and not very demanding in terms of LPG systems at all. Back in the day, me and a few mates have had 3 litre BMW cars but removed the engine and fitted in a 2L Cosworth for much better performance - nowhere near as smooth an engine but more powerful and was great in the nice handling BMW chassis!

Turtle also first said that the only reason he wanted to do this was 'because it is fun and he likes a challenge'. Ahh, so you'll have us believe the above isn't really relevant then Turtle, just a project to see if you can make this happen for the fun of it, no practical reason for wanting to do so? When asked where the logic was in wanting to do this Turtle says 'my car takes a second longer on 0-60 on LPG compared to petrol'... Ahh so there is a reason why you want to switch to petrol in sport mode - Why say just for the fun of it then? To be fair, nobody has mentioned the slightly lower calorific value of LPG compared to petrol, this will increase 0-60 times very slightly (a point or so) but not by a second. As others have said, if you can tell the difference in power / acceleration on LPG then your LPG system isn't setup correctly - So now we're getting to the real reason you want to do this and have told you that you're approaching this from the wrong angle... But if you still believe you will go a second faster on petrol than on LPG with a properly setup system then it is a pity you have the BRC system (that you say is 'high quality' etc)... Because with a different LPG system it would be very simple to set the system up so the car switches back to petrol, or any mix of petrol and LPG, instantaneously as soon as you put your foot down past a certain point when above certain rpm. That would be a much neater, easier and more effective way of switching back to petrol for high performance driving for those who stubbornly think LPG is slower than petrol and would also mean that at part throttle during performance driving you still wouldn't be using any expensive petrol. Better still, buy a faster car and have that run on LPG all the time...

Turtle, if you were at an art lesson and failing to paint a rainbow would you tell the art teacher you wanted to paint a set of different coloured lines for the fun of it - then mind if the art teacher tried to show you how to paint the rainbow?

Simon
www.Lpgc.co.uk

[e301988325i]

Our old 330i on BRC was also noticeably slower on LPG, I'd say 15bhp down on gas. Maybe the BRC system attempts to achieve stoich in all circumstances instead of allowing it to run rich?

Ps) For your 330i, the spark plugs are a hell of a job to change (comparatively), when I did the plugs on my car they clearly hadn't been changed as per the service history stamps indicate, but the car was running smoothly even though the plugs were in the worst condition I'd ever seen, excluding obvious destruction/melting. After I fitted new plugs the car was noticeably better to drive. I've also heard of sharks only changing the front 4 plugs as the back two are a PITA to get to. Just a thought.

[LPGC]

Our old 330i on BRC was also noticeably slower on LPG, I'd say 15bhp down on gas. Maybe the BRC system attempts to achieve stoich in all circumstances instead of allowing it to run rich?

Ps) For your 330i, the spark plugs are a hell of a job to change (comparatively), when I did the plugs on my car they clearly hadn't been changed as per the service history stamps indicate, but the car was running smoothly even though the plugs were in the worst condition I'd ever seen, excluding obvious destruction/melting. After I fitted new plugs the car was noticeably better to drive. I've also heard of sharks only changing the front 4 plugs as the back two are a PITA to get to. Just a thought.

Maybe the BRC system was set up rich or lean at the top end, stoch mixtures usually give decent power on gas, makes the most of the fuel whilst not reducing volumetric efficiency by replacing air with gas vapour. Not as much power increase from a rich mixture on gas as there is on petrol but still should go rich to protect valves.

Are the plugs really hard to change on a BMW330? Depending on the year, if the rear plugs are difficult to get to it might only be due to the plastic firewall extension being in the way, easy enough to remove that assembly to get to the rear plugs. I've had a few BMW750's - now some of the plugs really are a pain to get to on the V12's

Simon
www.Lpgc.co.uk

[e301988325i]

Took me 4hrs to do the plugs on the 330i first time. Compared to 20 mins on my M20 E30 they're a nightmare. You're correct the pollen filter housing does have to come off.

[325i]

4hrs... Really? Yes the pollen cover comes off but it's only a few screws. In total its an hour's job.

[e301988325i]

First time at home, LPG injectors bolted to the cover made it especially difficult. Shite build up on the old plugs made them extremely worrying during removal, tight and graunchy as though they were picking up, lots of time checking the head threads before reassembly. As I mentioned it looked as though the plugs had done the entire mileage of the car.