More power from LPG

[simonrockman]

There is an article in this month's Practical Performance Car saying that as LPG has a higher octane rating, if you get the timing right you get more power from it than you do from petrol.

Simon

[TVR MAN]

Yeah, I read that aswell, if thats true why are performance car manufacturers not trying very hard to sway their fuel of choice to LPG

[PhillT]

I'm reliably assured that LPG is all but dead. There's very little Government incentives any more, and residual values are abysmal.

[ridds]

Octane rating may be higher but the calorific value is lower hence reduction in power in most cases.

[tuttle]

Read this article too, as I understood it upping the compression to around 13:1,iirc, was an important factor with getting the most out of lpg

[zevans]

As I understand it, the problem is cold starts. An LPG engine tuned for power has the same problems as you'd have trying to drive a Le Mans petrol number on public roads, ie no idle to speak of, and a bugger to get started. Hence dual-fuel rather than outright conversion.

I too sat reading that article thinking of trackday specials...

[tr7v8]

Yup interesting comments on the RPI V8 website, LPG is around 112RON so yup
mega amounts of advance. RPI do a Dual ignition kit which changes the advance for when running on LPG for exactly this reason.

Jim

[andytk]

PhillT said:

I'm reliably assured that LPG is all but dead. There's very little Government incentives any more, and residual values are abysmal.

The government incentives were always useless anyway. They were practically impossible to qualify for.

Plus you don't convert a vehicle to LPG to improve its residuals, you convert it as a cost saving measure if you do big milage.

LPG's biggest problem is that diesel technology has largely made it redundant.

As for cold start, as I understand it, its only an issue while you're coolant is cold, which is why you run it on petrol. Hence the dual fuel.

I'd love to build up a car with a big V8 and a sequential LPG setup, the idea of V8 power with diesel costs appeals to scrooge Scot in me.

Andy

[Pigeon]

It depends how good the fuel metering arrangements are. If they're not good it's very easy to either get not enough fuel or far too much. The little single-cylinder donkey engines with pull start which are made in Japan normally start first pull in the petrol case; you can get them in LPG versions as well, which would be useful for powering the fan in those gas space heaters that look like jet engines, except they're such a bastard to start that nobody buys them.

[worthidlj]

please dont slate me but i do read maxpower (and its not for the women...... muck )
a few months ago they had an lpg conversion (by p-i systems i tink), in their new products page, for diesel cars that made them more efficient; is this claim accurate or just a bit of sales spin?

[worthidlj]

just found the article, this is wot it says:
"POWERSHOT - Liquid petroleum gas's (LPG) arrival as an alternative fuel has barely registered on Planet Max. Suprising then, that LPG is at the core of Powershot, a power-boosting mod for diesel cars.
Diesel engines run on about 85% combustion efficiency, leaving 15% unburned to exit through the exhaust. Powershot injects the propane form of LPG into the cylinders to increase combustion efficiency to 100%.
This immediately provides more power and mpg. Extra propane is injected to further increase power.
Installation includes the fitting of Powershot, plus an LPG tank and filling system. Top up on propane at LPG-friendly filling stations."
so wot does everyone think. (i apologise if this breaks forum rules as a bit unsure )

[Pigeon]

Well, you could say the same thing about nitrous, but that remains popular enough. For a road car I reckon it makes a lot of sense. I find that the only time I really need a lot of power is for overtaking. The rest of the time, while not denying that to have more power would be nice, it is still possible to have fun with less. So a system that provides a temporary large increase in power is just the ticket. Then, compared to nitrous, propane on a diesel has the advantage that propane cylinders last a lot longer than nitrous bottles, are a lot cheaper to refill, and are much more widely available.

[tuttle]

Pigeon said:

Well, you could say the same thing about nitrous, but that remains popular enough. For a road car I reckon it makes a lot of sense. I find that the only time I really need a lot of power is for overtaking. The rest of the time, while not denying that to have more power would be nice, it is still possible to have fun with less. So a system that provides a temporary large increase in power is just the ticket. Then, compared to nitrous, propane on a diesel has the advantage that propane cylinders last a lot longer than nitrous bottles, are a lot cheaper to refill, and are much more widely available.

Agreed, whilst reading through this thread I kept thinking of the nitrous option, there are some pretty decent kits for diesels now.OTOH its not really going to save you any running expenses money.
I have a customer who has lpg converted his Nissan Skyline, the new ecu seems to control gas fine from cold starts with no probs. He reports an increase in torque, though it felt the same too me- he certainly hasn't lost power. The engine seems to idle smoothly & remains generally quiet & reliable.

[andytk]

Quinny said:

If you need more performance, just get it chipped or get a more powerful car.

Or don't buy a friggin, diesel to start with.

Andy

[andytk]

tuttle said:

I have a customer who has lpg converted his Nissan Skyline, the new ecu seems to control gas fine from cold starts with no probs.

Would this be a turbo charged skyline perchance?

I've only ever heard of one other turbo LPG setup and that was on a Scooby. I was under the impression that its a very hard thing to map the LPG injection to a turbo motor.

Andy

[EvoBarry]

The only reason I can recall for poor starting/cold running on LPG conversions is the gas/liquid needs heating up before it can be injected or mixed into the intake manifold - ergo coolant is run through the mixer device to warm it up beforehand, I never had an issue with my old Honda tbh, and my system switched over the first time revs passed 2500 or so, which meant more or less as soon as I set off tbh.

Main annoyance I had with the setup was it was an early kit so prone to going out of tune, and the 70 litre tank sitting in the boot.

[danhay]

My take on the article was that they were saying with LPG you could afford to run a car with a bigger engine, rather than it providing more power than petrol. You will lose power compared to petrol, but if it means you can reasonably run a V6 version instead of a 2 litre for instance, then it makes sense.

I've had a V6 Cavalier converted to run on LPG, and it was as cheap to run as a diesel...but much quicker. Plus it had traction control as a bonus.

[gavinl]

Pigeon said:

Well, you could say the same thing about nitrous, but that remains popular enough.

Nitrous is popular?

[R988]

andytk said:

tuttle said: I have a customer who has lpg converted his Nissan Skyline, the new ecu seems to control gas fine from cold starts with no probs. Would this be a turbo charged skyline perchance? I've only ever heard of one other turbo LPG setup and that was on a Scooby. I was under the impression that its a very hard thing to map the LPG injection to a turbo motor. Andy

There are some Rotary Turbos on LPG as well
www.autospeed.com/cms/article.html?src=suggestions&A=0406

I believe though, that in Australia at least, LPG has been derated down a bit from 100RON since that article, I can't remember the details but they mix some other gas or something, which is why it smells crap now as well.

[rolyrat]

R988 said:

andytk said: [quote=tuttle] I have a customer who has lpg converted his Nissan Skyline, the new ecu seems to control gas fine from cold starts with no probs. Would this be a turbo charged skyline perchance? I've only ever heard of one other turbo LPG setup and that was on a Scooby. I was under the impression that its a very hard thing to map the LPG injection to a turbo motor. Andy

I know a guy with a T5 volvo on gas, and that starts and drives very nicely.