BMW 325i 2007 converted to LPG

[Ader1]

Hi (First post)

I have a BMW 325i 2007 which I converted to LPG September 2020. A few weeks ago the engine started to misfire. I've taken it to the garage and apparently the issue is a burnt valve. I have spoken to a couple of mechanics about it and they say it's a very rare thing to happen these days. I've also spoke to a guy who used to do LPG conversion and he's surprised as it's a fairly modern engine. Anyway, I've decided to have it fixed and it won't be that cheap. A few garages weren't interested so it's been a bit of a hassle and the guy who is doing the repair warned be it would take a while as he's so busy with other work doing mot's etc.

I'm wondering if you people here could help me regarding clarifying if I have been unlucky or is this an issue with LPG fuel on these BMW's. Also, how can I minimise the chances of this happening again? Thank you for reading and I hope I do receive some replies.

[georgeyboy12345]

How many miles has it done?

[The spinner of plates]

It’s what puts my off LPG conversions - they’re often only as good as the installer.

[Fiedka]

If it’s 2007 does it not mean it’s an N53 with direct injection hence not suitable for LPG?

[Smint]

Did the converter fit a decent quality (not a simple vacuum fed) flashlube system, and did the system use fluid at a reasonable rate and did you replenish the fluid.

Are you sure the valve or its seat is actually burned out, it might be a case of VSR (valve seat recession) again mainly associated with LPG conversions without a decent flashlube system, and if the valves are adjustable, ie via shims, then getting some valve clearance back inplace might be a cure for now.

The only cases of valve/seat damage or vsr i've known of personally have been on cars not fitted with a flashlube system, had vsr on a Mitsi Outlander 1 sold converted new by the maker without flashlube, adjusting the manually adjutable valve clearances and fitting a good flashlube system saw that car give many more years of good service.

[Ader1]

Fiedka said:

If it’s 2007 does it not mean it’s an N53 with direct injection hence not suitable for LPG?

I've never heard this before. How do I find out if it's an N53 or not?

[Ader1]

Smint said:

Did the converter fit a decent quality (not a simple vacuum fed) flashlube system, and did the system use fluid at a reasonable rate and did you replenish the fluid.

Are you sure the valve or its seat is actually burned out, it might be a case of VSR (valve seat recession) again mainly associated with LPG conversions without a decent flashlube system, and if the valves are adjustable, ie via shims, then getting some valve clearance back inplace might be a cure for now.

The only cases of valve/seat damage or vsr i've known of personally have been on cars not fitted with a flashlube system, had vsr on a Mitsi Outlander 1 sold converted new by the maker without flashlube, adjusting the manually adjutable valve clearances and fitting a good flashlube system saw that car give many more years of good service.

No there's not flashlube system. Could you link to one I could maybe install? Is that a big job to install it?

[Smint]

Ader1 said:

No there's not flashlube system. Could you link to one I could maybe install? Is that a big job to install it?

That's almost certainly why you have issues, especially on such a recent conversion, though if the above poster is right about the engine being direct injection then most reputable installers wouldn't have fitted LPG at all because it can and does destroy petrol injectors when running on LPG.
As explained to me by two reputable installers when i nearly bought a SWB petrol Shogun 3.5 for the good lady.

You can buy a cheap flashlube kit that works off intake manifold vaccum from ebay and yes you could DIY it, but are maybe better off getting a pro LPG converter to fit a suitable electronic dispenser with multiple feeds into the intake just ahead of each inlet valve, or a pressurised system that injects straight into the gas flow (if your LPG system is compatible), both of which may need programming to suit the make of LPG system.

I have each of the better flashlube systems fitted to 2 of our cars, the electronic pumped type would probably be fine for your car, ours is better injected into the gas flow due to boxer engine intake design, but even the humble vacuum kit is better than none.

Why on earth didn't the original installer recommend a flashlube kit? he spoiled the ship for a ha'porth of tar.
Did the intaller have you back after a few weeks or a thousand miles or so for fine tuning of the system? you might have bad fuelling anyway if it hasn't been fine cailbrated or serviced correctly since.

Edited by Smint on Saturday 25th June 11:31

[Fiedka]

Ader1 said:

Fiedka said:

If it’s 2007 does it not mean it’s an N53 with direct injection hence not suitable for LPG?

I've never heard this before. How do I find out if it's an N53 or not?

2007 was a changeover year for e90. You can tell by the road tax rate - it is lower for N53. Probably easiest to by decoding VIN - Google BMW vin decoder.
If I recall correctly engine cover might be a giveaway - black on N53, silver on N52 but not 100% sure on that one.

[Ader1]

Fiedka said:

2007 was a changeover year for e90. You can tell by the road tax rate - it is lower for N53. Probably easiest to by decoding VIN - Google BMW vin decoder.
If I recall correctly engine cover might be a giveaway - black on N53, silver on N52 but not 100% sure on that one.

ok I have done that and apparently it's an N52. So that would be fine I guess?

[bmwmike]

All n53 had black covers and no bulge for the valvetronic motor. They are also 12:1 compression so I doubt they could be LPG on that reason alone?

Sounds like OP has n52 anyway..

[Fiedka]

Ader1 said:

Fiedka said:

2007 was a changeover year for e90. You can tell by the road tax rate - it is lower for N53. Probably easiest to by decoding VIN - Google BMW vin decoder.
If I recall correctly engine cover might be a giveaway - black on N53, silver on N52 but not 100% sure on that one.

ok I have done that and apparently it's an N52. So that would be fine I guess?

Looks like it. It would have been really bad if someone even attempted LPG on N53.

[Ader1]

So I understand that my issues lie with the fact that no flashlube system was installed? And I need to rectify this?

[Smint]

Ader1 said:

So I understand that my issues lie with the fact that no flashlube system was installed? And I need to rectify this?

I suspect this is at the root of your problem, but if the system was never recalibrated after an initial run in period and has not been serviced and recalibrated since then, any resulting poor fueling could have a detrimental effect.

Refitting a flashlube system won't fix the present issues, but should help prevent the same happening again once it's the problems have been fixed, however i would advise getting the system serviced and recalibrated by someone with the correct software.

Other issues could be poor mapping, the LPG system is supposed to run off the car's own map, but if detonation (pinking) is present then no amount of flashlube will prevent valve seat burn, and if the original LPG injectors weren't up to scratch then again there could be issues.

As alluded to on an above post, all LPG installers (and systems) are not equal.

[Ader1]

Hi,

Someone on another forum sent me this information. It doesn't make much sense to me. Maybe my lpg system wasn't correctly installed?


https://www.lpgforum.co.uk/viewtopic.php?p=122362

[stevieturbo]

Ader1 said:

So I understand that my issues lie with the fact that no flashlube system was installed? And I need to rectify this?

Or it could be a bad install, poor tuning of the system or there could be a different underlying cause.

Until the head/valves are inspected to see if the damage is one cylinder, all cylinders, all valves etc etc.....you will not know.

And then once repaired, the system would need checked to ensure fueling whilst on LPG is tuned correctly.

But the flashlube, or lack thereof might also be a factor