Joined: May 3rd, 2009, 11:40 am Posts: 816 Location: Melbourne, Australia.
LPG (O!) Vapour injection
This ones for Geo On another forum a concern came up about DIY vapour injected lpg, how do aftermarket ecu's (kdfi, megasquirt) deal with pulse width modulation of lpg injecters in realtion to the changing pressure coming from the converter?
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I'd be interested to know how they handle the fuel pressure compensation on a standalone install.The piggy back LPG systems have a pressure sensor so they can calculate the injector pulse based on the converter output pressure.Most of the newer aftermarket ecus have several configurable analog inputs which I suppose could be connected to a pressure sensor and then mapped to achieve the same result?
I assumed the converter could set a constant pressure, like a fuel regulator, but then it is suggested that with boost applications it could not keep up...
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The other option I had considered when I was considering the vapour injection route was just to disconnect the vacuum signal to the converter or reverse the spring so it would just run at max pressure all the time.The problem with that was that the output pressure (on the converters I could get info on) would've been very marginal once boost was taken into consideration and even with the biggest injector size, the duty cycle would've maxed out at lowish boost. I have since found there are boost suitable converters available with higher vapour output pressures, but tbh the advantage of vapour injection on a dedicated lpg car (especially a turbocharged one) is minute compared to using a liquid injection system.
Harley
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samfieldhouse wrote:
It is M9 for the shocks yes, the rest I'll check when next i'm underneath her. Ironically, this will be valentines day.
May 16th, 2013, 11:10 am
lpgo
Firing on 1-2 Spark
Joined: November 8th, 2009, 5:42 pm Posts: 2847 Location: NL
Re: LPG (O!) Vapour injection
Oh Harley it is so simple............
The lpg converter keeps the lpg pressure at about +1 bar, so the gas is injected with 1 bar of pressure.... Now for a turbocar you can connect a hose from the inletmanifold to the converter at the backside of the membran, so when boost increases in the inletmanifold the gas pressure will also rise in the converter at the same level so the pressure of the lpg gas will still be + 1 relative to the inletmanifold
Clever hey and simple......
Look at the yellow arrow in the pic this is the hose running from the inletmanifold to the LPG converter
Attachment:
lpg.jpg
Attachment:
lpg.JPG
It is from this video
So the VE table is relatively flat because the injection is regulated by the gas pressure and less to the opening time of the injector.....
Hope you understand once again what I'm trying to say....
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Russell wrote:
Hi Geo, you've been one of the sites biggest attractions in recent years. Russ
May 16th, 2013, 10:32 pm
Harley
Firing on two.
Joined: May 3rd, 2009, 11:40 am Posts: 816 Location: Melbourne, Australia.
Re: LPG (O!) Vapour injection
Thats great Lpgo, thank you.
Here is some info I received you may find helpful, or already know:
Quote:
I've been running LPG for approx 25 years now on various vehicles. The major point many get wrong is the advance curve for LPG. There's three key points: 1. Ease of starting - you still need 5-10 deg. BTDC 2. Rate of advance - needs to come in very quickly, like 15-20 deg @ 1250 rpm 3. Max advance - far less than petrol, 21-22 max
Harley
_________________
samfieldhouse wrote:
It is M9 for the shocks yes, the rest I'll check when next i'm underneath her. Ironically, this will be valentines day.
May 17th, 2013, 4:37 pm
lpgo
Firing on 1-2 Spark
Joined: November 8th, 2009, 5:42 pm Posts: 2847 Location: NL
Re: LPG (O!) Vapour injection
Harley wrote:
Thats great Lpgo, thank you.
Here is some info I received you may find helpful, or already know:
Quote:
I've been running LPG for approx 25 years now on various vehicles. The major point many get wrong is the advance curve for LPG. There's three key points: 1. Ease of starting - you still need 5-10 deg. BTDC 2. Rate of advance - needs to come in very quickly, like 15-20 deg @ 1250 rpm 3. Max advance - far less than petrol, 21-22 max
Harley
I notice no diffrence between LPG and petrol, lpg can take slightly more advance over petrol in all ranges, so I dissagree with point 3.
My turbo runs at 22 degrees when doing around 1 bar of boost without pinking.......
p.s. point 2. Rate of advance can always come in quickly this has nothing to do with petrol or lpg. The point is on points you can't do 15 to 20 degrees at all 1200 rpm but with 1-2-Spark you can......
Theres already an increase of torque with 1-2-spark at low rpm...... over normal ignition and even 123......
Attachment:
ADVANCE.jpg
My normal advance table...
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Russell wrote:
Hi Geo, you've been one of the sites biggest attractions in recent years. Russ
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