LPG Conversions

[mattf]

All,

Before I launch into this one, I should point-out that I'm not Russian, and I don't like M3s. So here goes....

Has anyone looked into LPG conversions for Audis in general and RS4s in particular?

I understand that this will be anathema to most if not all of you/us, and that you/we bought the cars we did because of the performance they offer - but I had a bit of an epiphany when I filled my car with V-power on the M6 yesterday and it cost over £78!

I have done a little research, and the headline news appears to be:

Pros:
Conversion costs: from £1.2k - £2k
LPG costs: Approx 50% of unleaded, so 40ish% of super unleaded
LPG RON: 108
Efficiency: LPG less energy density than unleaded, so efficiency is approx 80% of unleaded

Cons:
Availability: 25% of UK filling stations are LPG equipped
Performance: Apocryphal evidence suggests a drop in performance, but I can't find any details?
Warantees: Potential to invalidate manufacturers warantees

Fair amount of main stream manufacturers now offer dual-fuel options from new, Volvo, Ford, Vauxhall etc - but seemingly not Audi....

I await your derision with interest

[dom888]

I asked APS about it and they said that some engine components wouldn't last very long and would need frequent replacement. Plus I suspect the resale value would be hurt quite considerably.

[mattf]

The resale value depreciation point is a good one, been looking at that from 2 perspectives:

1. We're on the cusp of a step change with regards to fuel prices and fossil fuels in general, and alternative fuels/technologies are very much in the ascendant, so resale prices on cars like ours are only going to go one way....

2. The UK, (and actually the developed world in general) is way too committed to traditional fuel technologies to support anything but the most gradual, gentle shift across to greener fuels, so there will be a niche market for performance cars for some time to come. But even then I suspect it'll be a buyers' market - which doesn't bode well for resale values.

Would be interested to know which engine components are likely to suffer premature failure and why however ?

[tartan_rob]

I knew a guy once that ran a 400+ bhp B5 S4 on LPG. He had no issues.

[SR71]

IMHO, people are talking themselves into a frenzy over this oil price issue....

We've already discussed how the difference is still only responsible for an extra ~£500/year if you drive about 10K miles per year.

I just don't think potential owners who are going to spend £50K on a car are going to be swayed by the rise in prices at the fore-court. I am not going to stop coveting a new GTR because super is £1.25/litre.

Flip side is, assuming your LPG conversion doesn't appreciably affect the internals, surely having a conversion on a car like a RS4 isn't going to put anyone off?

But being able to convince someone that thats the case is the tricky bit...

I understand that cars tend to run hotter with the conversion, and with a big V8 stuffed in a small space, I'm not sure thats a good idea...but that doesn't help you one bit does it?

[PetrolDave]

I await your derision with interest

I have to admit to thinking about an LPG conversion too...

The much lower cost of the fuel is VERY appealing, but what's put me off (I intend to own my RS4 for the long term so residuals isn't my top priority) is where would the LPG tank go? I've got an Avant and I often use the longer load space and wouldn't want to lose that (we only just got all our suitcases in when we went on holiday recently, and I need plenty of space for our upcoming wine trip to the Loire region).

[ARSEY4]

IMHO, people are talking themselves into a frenzy over this oil price issue....

We've already discussed how the difference is still only responsible for an extra ~£500/year if you drive about 10K miles per year.

I just don't think potential owners who are going to spend £50K on a car are going to be swayed by the rise in prices at the fore-court. I am not going to stop coveting a new GTR because super is £1.25/litre.

Im not so sure its a case of people being able to afford it more of a case of not being prepared to pay it. With two cars doing sub 25 mpg we decided that enough was enough. The thought of repaying the mortgage earlier was an additional incentive. I dont think I would of sold if petrol and deisel had been below £1 a litre. It was more of a case of what else we could do with the money really.

[mattf]

Don't mean to appear frenzied ref oil prices, just considering the options.

Ref placement of the LPG tank, that was a cause for concern for me also, I bought an Avant for a reason (well, 2 reasons really, firstly because I needed the space and secondly because real RSs are all Avants - but everybody knows that?)

What has been suggested is a tank in the spare-wheel space....although, presumably if one is prepared to spend the money on a bespoke system, perhaps 2 smaller tanks could be worked into the vehicle in other locations, although impact protection would be an issue.

Biggest issue I have come across so far would appear to be at a corporate level, thats to say Audi's lack of enthusiasm for LPG. Not sure how far I'm gonna take this, but I don't want to be deterred from scoping it just because it hasn't been done before.

[SR71]

There is a thread on Pistonheads about fitting a B7 with LPG but it kinda died a death...http://www.pistonheads.co.uk/gassing/to ... 0&t=488698

By all accounts the guy considering it is minted (I mean how many people have two Lambo's, a Ferrari, a Porsche etc etc with a RS4 for a runabout eh?) so blowing up his V8 might be a price he was willing to pay?

I do understand the "not prepared to pay" sentiment though....

I don't need one cos the A3 gets us 55+mpg although I'd still run it on cooking oil from Costco if it wasn't PD!

[PetrolDave]

What has been suggested is a tank in the spare-wheel space.

Nice idea ... which would work on every B7 Avant EXCEPT the RS4 .... because that's where the battery is on the RS4!!!

[reevesroadster]

Personally, I'd swap the RS4 for something else -an S-line maybe - and then do the conversion.

Or a Rangey a couple of years old and convert that - loads of space, luxury, comfort etc, etc. and they'll be cheaper to buy than an RS4.

[baza]

I dont know much about engines but l read somewhere that FSI engines cannt be converted.

[UKS4APR1]

I dont know much about engines but l read somewhere that FSI engines cannt be converted.

That's right - The FSI engine has injectors directly into the cylinder. When these stop discharging fuel (i.e. when the LPG system is running) they become overheated and damaged. So I was led to believe anyway.
"Normal" injection occurs before the inlet valve, FSI injects alongside the spark plug, the Inlet valves only let air in to the cyjinder (or air and LPG in the case of LPG conversion)