Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series & 4 Series > E90/E91/E92/E93 (2006 - 2013)

E90/E91/E92/E93 (2006 - 2013)
The E9X is the 4th evolution of the BMW 3 series including a highly tuned twin turbo 335i variant pushing out 300hp and 300 ft. lbs. of torque. BMW continues to show that it sets the bar for true driving performance! -- View the E9X Wiki

Thread Tools Display Modes
Old 05-16-2014, 04:44 AM
Vic_LeChic Vic_LeChic is offline
Registered User
Location: Spain
Join Date: Jan 2013
Posts: 62
Mein Auto: E92 330i Coupe N52B30
LPG conversion: valve damage?

Hi everyone

Whilst reading avout LPG conversion I came across an article about valve damage. Has anyone experienced this problem?



Due to the ever increasing cost of LPG and the unsuitability of most modern petrol engines from around 2006 onwards most now suffer from severe exhaust valve and valve seat recession when converted to run on LPG. This is caused by cheap and poor quality materials being used in the manufacture of the exhaust valves and seats, and also the discontinuation of Manually Adjustable Tappets, Self Adjusting Hydraulic Tappets and engines with VVT Variable Valve Timing.

In most modern multi-valve engines in a bid to reduce prices and ease of manufacture, the makers have opted for fixed clearance or solid tappets which cannot be adjusted without extensive work and often the removal of the cylinder head. These components and materials are fine when running on petrol only, I will explain in more detail below.

This is where the problems with valve seat recession starts, LPG once vaporised is a pure vapour and has no lubricating properties at all, this then passes through the inlet valves and into the cylinder where it is ignited by the spark plugs, combustion takes place and the hot spent gasses exit through the exhaust valves.

Because these gasses are very hot and contain no lubricants or additives they very slowly start to burn the valve face and valve seat of the exhaust valve away, this process (called recession) over time eventually causes the valve to recede in to its seat eventually reducing the valve or tappet clearance to zero. Once this has happened it is only a matter of a few miles before the valve head starts to disintegrate causing loss of compression and misfire. This will also lead to catalytic converter failure if the vehicle continues to be driven with misfires by way off unburnt fuel passing through the exhaust system to the catalytic convertor.


If it feels good, go for it. If in doubt, there's no doubt.

my cars:
- BMW 330i Coupe E92 N52 (272 bhp) 2007
Montego blue - beige leather - piano black - M3 18" rims- Aero M sport front bumper - M3 rear spoiler - Sport seats

- SEAT Leon Cupra R mk1 (210 bhp) 2003
Ebony black - 18" rims - Brembo breaks - Recaro seats - Turbo charged twin intercooler

Last edited by Vic_LeChic; 05-16-2014 at 04:46 AM.
Reply With Quote

See More Related BMW Stories

Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series & 4 Series > E90/E91/E92/E93 (2006 - 2013)
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

All times are GMT -7. The time now is 10:46 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
© 2001-2015 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms