M20B27 on LPG - Developments

[StuBeeDoo]

StuBeeDoo you are getting 75% of your petrol economy on LPG. I don't think you are going to get much better. The "problem" with LPG is the energy per unit volume of the fuel it a lot less.

You are not going to get the LPG fuel economy to with in 10% of the petrol economy. I don't think its possible.

It's well known that as LPG has much higher RON than pump petrol it needs more ignition advance (typically 4-6degs) to be as efficient as possible. See here

Watch this space.

[eta]

I am aware of the higher RON but increasing the ignition advance does magic more enrgy from the fuel burnt.

All fuels release a fixed ammount of energy per kg or litre. For LPG this is 25.3 MJ/l for petrol it is 34.2 MJ/l. To get the same ammount of energy release from combustion from LPG as from petrol you need around 35% more fuel by volume.

Changing the ignition advance will not elimate that "problem". Changing the ignition advance will simply change the ammount of energy that can be transfered into useful mechanical energy. This will have an effect of power output and fuel efficency. To achieve the same power output on LPG as on petrol, you will need nearly a 35% more LPG to be injected into the engine than petrol. That is the physics of the situation.


All LPG vehicles have a fuel economy of around 75% what the same engine does on petrol from my previous experiance and reseach which I did before forking out for the system. LPG vehicles do not make more power as the petrol engine are never optimised to run on LPG To get the best from LPG you would need to run CR of 12:1 or higher. High octane petrol will run in an engine with a CR of 12:1 if it built and tuned corecctley. The CR of 10.2 -10.5:1 that you have is what 95RON comfortably runs on so not optimal for LPG.

The solution is get a bigger LPG tank. A 90l torpedo will do nicely, then you will have a decent range. You are chasing an impossible goal but some gains in power and fuel economy may be possible.

Gunni the cost per mile is the issue that I am trying to explain. I am trying to explain why he will never get petrol economy figures from LPG.

[StuBeeDoo]

The solution is get a bigger LPG tank. A 90l torpedo will do nicely, then you will have a decent range. You are chasing an impossible goal but some gains in power and fuel economy may be possible.

You're missing the point.

I haven't got a problem with range. Fitting a bigger tank in a touring is not an option, I need all the boot space I can get.

I accept that I may not get any gains. Have you read the thread properly?? For one thing, I haven't stated any hard-and-fast "goal", everything I've posted on this thread has revolved around conjecture.

Hopefully find a few more LPG mpg by getting the ignition timing right for the higher RON of LPG.

at the end of the day, if all I achieve is to improve the mpg by 10%, I'll be happy. Any power and torque increases will be a bonus.

If I am lucky enough to find another 10%, it'll still be only 80% of what I know it to be capable of on petrol.

Firstly, I need to get the engine running properly on petrol. It is well known that for an engine to run anywhere near properly on LPG, it has first to be running right on petrol - mine isn't. I've tried 4 different generic chips and none have been anywhere near 100%. Therefore I want to get a live remap. The chip I've chosen has multiple-map capability so if I'm doing it on petrol, I might as well get it done on LPG as well.
Secondly, there seems to be a lot of hot air spouted about eta/731 engines and what power they should make with very little proof to back-up the claims.
I have a theory that the only way to get a 2.7 running properly is to have it mapped. What I'm doing here is going public with the results because I'm not the only one on the forum that has running issues with a 2.7.


So if you think this is only about LPG consumption, you've got it wrong. Yes, I have a concern that I'm using too much, but I'm well aware of all the comparison figures. What it is about is getting the engine running as efficiently as possible on both fuels. So I'm buying a re-writable chip and I'll be getting it mapped on the dyno. My money, my time, my choice - good or bad. The results will be posted here for all to see. Whatever the outcome for me, it will help someone else to make informed decisions based on proven figures and facts rather than theories and "best guesses".

[eta]

Well I hope you achieve your goals and get your 2.7 running as effienctly as possible. Maybe I misread your ambitions? I am sure you will enjoy the process of tuning. Something I would like to have a go at my self. Maybe I should also buy a warchip and have a play.

I agree on the point a 2.7i needs a live mapping session. Mine was done by A-tech on the road. It works but I always wonder if there is anything to be gained by proper rolling raod remap.

Incidently how much did the warchip set you back in £ once it is posted and duty and VAT paid?

[StuBeeDoo]

Incidently how much did the warchip set you back in £ once it is posted and duty and VAT paid?

£265 for the chip etc and the postage. I'll let you know about the duty and VAT when it arrives.

[GeoffBob]

It works but I always wonder if there is anything to be gained by proper rolling road remap.

Only if the roling-road has a built in retarder (an eddy-current brake) that can hold the car at a constant engine load while the tuner sits inside with his laptop and tunes that particular spot on the ignition and fuel maps. Tuning on the open road or on a simple inertia type dyno (rolling-road) is difficult due to the fact that the load point shifts around. I've done my fair share of tuning on the open road and it's a mugs game (imo).

[StuBeeDoo]

It works but I always wonder if there is anything to be gained by proper rolling road remap.

Only if the roling-road has a built in retarder

The one I'll be using does.

[Jon_Bmw]

Geoff has adopted my retarder expression.

I have made it.

[Simon13]

would cruise control help?! for on the road and rollers for part load stuff.

[GeoffBob]

Geoff has adopted my retarder expression.

I have made it.

I learn only from the best Jon

[Jon_Bmw]

would cruise control help?! for on the road and rollers for part load stuff.

In what respect did you mean Simon, for tuning/mapping?

With the rollers and retarder in action it is very easy to get (and see - on the mapping software) all the different load points with your right foot.

Cruise crontol would mean you could go a set speed, but it would not alter the load site. It would settle at the load site that the gear determined that would acheive the cruise control set speed. I.E in forth you might need load site 4 to maintain 70mph.

You can map on the road and some people only do it that way, but I think it would take a lot longer and there is so so so much risk involved in doing it. One of the older lads from work knew someone who was killed mapping on the road.

You have to have a data logger and do numerous runs of differing throttle positions and then see how much out your current map for that load site is. Then you have to make estimated changes to fuel and spark maps and start all over again. Someone who maps only single make engines, i.e 4g63 out of an evo can get quite quick at it I guess, but it is never going to be as good a map as one done on the rollers and then checked on the road.

With rollers held at 2000rpm you can do every single load site in around 5 minutes (typically 15 sites) - the best bit is that as you are optimising both fuel and ignition maps you can watch the power increase, something you can't see on the road.

Generally the actual mapping of a car isn't hugly time consuming, sorting out the issues with the car/management software takes the time. Also giving the car a breather every now and then costs time.

For the keen DIY'er who likes to keep money in his pocket and doesn't mind spending a bit on some assets you can do quite well with an Ostrich emulator and an AFR logger system. All that can be bought and built for around £250 I seem to remember. You can then live map your car with the aide of tunerpro. You'll certainly have some fun with it and learn some stuff and still have the asset value of the gear at the end of it. Biggest problem is you need two people in the car and some nice flat roads with no coppers or other people on them!

Enough off topic now, sorry to those that I have put to sleep...

[GeoffBob]

One of the older lads from work knew someone who was killed mapping on the road.

Similar story I'm afraid, I knew someone who was killed napping on the road.

[Jon_Bmw]

They didn't just read my above long post on an I-phone whilst driving did they?

[Brianmoooore]

at the end of the day, if all I achieve is to improve the mpg by 10%, I'll be happy. Any power and torque increases will be a bonus.

If you can get a LPG system to be only 10% less MPG than petrol, then there is something wrong with the petrol system, or the car is only used for very short journeys.
A well set up LPG system should return a MPG of around 15% -20% less than on petrol, which is what I found in over 100,000 miles of LPG motoring with my red touring.
A litre of LPG may contain only 74% of the energy of a litre of petrol, but the combustion efficiency of LPG is considerably greater in an internal combustion engine than for petrol, even if that engine is far from optimised for LPG.

[StuBeeDoo]

If you can get a LPG system to be only 10% less MPG than petrol, then there is something wrong with the petrol system, or the car is only used for very short journeys.

If I am lucky enough to find another 10%, it'll still be only 80% of what I know it to be capable of on petrol.

Firstly, I need to get the engine running properly on petrol.

I've used 5 different chips with my 2.7s. 4 generic 2.7-specific ones and a factory-fit 325i one.
Of all of them the engines ran smoothest on the 325i chip. They started from cold best on this chip. All the generic 2.7 chips were, at best, definite compromises. Either the fuelling was wrong at some point in the rev-range, or the engine pinked, or both.
My conclusion?.............
Strokers really need live-mapping to get them running right.

[Simon13]

yeah was just a silly thought i had, that cruise could help in someway mapping on the road or on the rollers thats all!

[StuBeeDoo]

Incidently how much did the warchip set you back in £ once it is posted and duty and VAT paid?

£265 for the chip etc and the postage. I'll let you know about the duty and VAT when it arrives.

The chip arrived today and I didn't have to pay any duty or VAT.

[TouringTash]

Happy days fella I would have thought any thing coming into the uk over the last day or so would have been help up for 20%

[kevo]

is there any benefit in retarding or advancing the timing using a vernier pulley with lpg? just a thought?

[StuBeeDoo]

is there any benefit in retarding or advancing the timing using a vernier pulley with lpg? just a thought?

TBH Kev, I don't know. Having said that, if you did something like that you'd be stuck with it all the time and it wouldn't run right on petrol.

[StuBeeDoo]

One of the older lads from work knew someone who was killed mapping on the road.

Similar story I'm afraid, I knew someone who was killed napping on the road.

The instruction manual for the W.A.R chip specifically warns against mapping on the road.

[gareth]

is there any benefit in retarding or advancing the timing using a vernier pulley with lpg? just a thought?

That'll affect the cam timing, not the ignition timing. Ideally LPG needs more ignition advance but changes to cam timing will affect the engine's characteristics too, but not a great deal with a standard lazy cam.

[StuBeeDoo]

Right! Back on topic....

The W.A.R chip is installed in a spare ECU and the base maps are loaded. I've booked-in at Motoscope and a week after that I'm away on a 800-odd mile jaunt so I'll report back after.

[Ant]

All the best with this dude

[StuBeeDoo]

^^^^ Cheers Ant.

Right! The engine is now running on the W.A.R chip, but the car hasn't been on the rollers yet. I've downloaded a base map from Miller's website and tweeked the ignition maps a bit. OK, so it's all guess-work until the car gets on the rollers, but on the road it feels like I've found a fair bit more bottom-end.
There's definitely a fuelling issue with the base map on petrol because it's hunting badly, but I'm not too bothered about that at the moment.

[e301988325i]

Cool up and running that easily!

[StuBeeDoo]

Cool up and running that easily!

Yep, it was pretty straightforward. The hardest bit was working-out my favoured position for the map changeover switch. Obviously I need the dyno figures to back-up my gut feeling Alex, but I think this is going to be a must-have for anyone running LPG.

Now, I wish I'd done it a couple of years ago instead of frakking around thinking that getting the Motronic remapped was the only answer because it's OEM+.
And the beauty of it is that not only can I have an LPG-specific ignition map, but I can have another map for 99 octane (my petrol of choice), and a third one for 95 octane for when I'm touring 'round the far north of Scotland, for example, where they have neither LPG or 99.

....... And you can share maps with others who have similar engine spec's. The base map I'm using is one from a dude in North America somewhere with an eta/885 spec. I had it e-mailed to me from Miller's.

[eta]

Millar MAF sounds easy then.

[StuBeeDoo]

Millar MAF sounds easy then.

Dunno. I don't need a MAF, I run on LPG 99% of the time and my LPG system holds the AFM wide open.

Daimlerman's got a Miller MAF, IIRC.

[StuBeeDoo]

It's interesting (well, to me at least) that all 4 engines produce very similar-shaped plots.

That will be the only common denominator, then.
The camshaft.

[e301988325i]

I've downloaded a base map from Miller's website and tweeked the ignition maps a bit. OK, so it's all guess-work until the car gets on the rollers, but on the road it feels like I've found a fair bit more bottom-end.
There's definitely a fuelling issue with the base map on petrol because it's hunting badly, but I'm not too bothered about that at the moment.

That sounds very promising, and similar to the feeling I get of lost torque between 1-2K RPM, if you could spare the time , I'd be interested to see a print screen of the ignition table/software.

[StuBeeDoo]

That sounds very promising, and similar to the feeling I get of lost torque between 1-2K RPM, if you could spare the time , I'd be interested to see a print screen of the ignition table/software.

For some reason I can't get a screen shot Alex.
If you just want to see what the software looks like, there's a shot on Miller's website.

[e301988325i]

That's really interesting, can you adjust the idle timing as well to be optimised for LPG then?

With your AFM stuck open on LPG, I take it you only have two ignition points to map for each RPM point, part throttle and WOT?

Do you know if the software output the AFM/MAP voltage when live mapping?

[eta]

If the AFM is jammed open on LPG why not increase the spring tension a bit? You may have to remap but surely wide open AFM is not a good thing if it does it too soon.

[StuBeeDoo]

If the AFM is jammed open on LPG why not increase the spring tension a bit? You may have to remap but surely wide open AFM is not a good thing if it does it too soon.

The AFM is held wide open for a very good reason - to protect it from (possible) backfires. It isn't needed when running on LPG as it's only function is to tell the ECU how much air is going into the engine. The function isn't needed with closed-loop LPG as there is an O2 sensor in the exhaust. When running on LPG the only function of Motronic is ignition.