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EF pings on petrol, fine on LPG. 

 

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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Sun Nov 04, 2012 11:14 am 
Tyre Shredder
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I usually put only 98 in my car so when I have to run on petrol the timing isn't too far over-advanced.

Does your wife's car still have pulsing? I used to get pulsing under load on LPG that wouldn't go away. Eventually the idle went really ragged and uneven. A quick spray of WD40 around the intake gasket revealed a leak in the gasket. After changing the gasket - Voila! - no more pulsing.

A leak in the balance line can also cause pulsing, on a boosted car anyway. Maybe the same on na?

Maybe check your vacuum hoses and balance line for leaks?

 

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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Sun Nov 04, 2012 11:53 am 
Getting Side Ways
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Hi Sly,

I had my el intake and mixer on the wife's car and while it was on her car the pulsing stopped.

She still has my old el intake, but now with her old mixer and the pulsing is back.

I will definitely check the intake, but its been doing it since I got the LPG working and it had a head gasket change which required the intake manifold gasket be changed too. I drowned it them in hylomar at the time too. Most of the hoses vacuum and otherwise were changed at the same time.

Not sure why her mixer causes or exacerbates it, but hers is one of the most restrictive mixers I've ever seen on a 4lt. I am putting the BLOS in my car for now so she can ave my mixer soon.

Cheers

Frank
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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Sun Nov 04, 2012 12:34 pm 
Tyre Shredder
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That's odd Frank. I'd expect a more restrictive mixer would need the sensitivity on the converter reduced so as not to run rich. But in my (albeit limited) experience, pulsing has eventually been traced to a leak somewhere. Maybe the mixer is faulty?

Nonetheless, your plan sounds like a good one.

 

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AU1.5 Wagon, Raptor ProStreet kit, Pacemaker 4499's with 3" collector, 3" metal cat, 3" pipe, Pex BSO660 & BSO439, BA brakes, Sprintgas mixer LPG system, Airod variable-venturi mixer... stealth FTW Sniper tuned!

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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Tue Nov 06, 2012 9:41 pm 
Getting Side Ways
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sly wrote:
That's odd Frank. I'd expect a more restrictive mixer would need the sensitivity on the converter reduced so as not to run rich. But in my (albeit limited) experience, pulsing has eventually been traced to a leak somewhere. Maybe the mixer is faulty?

Nonetheless, your plan sounds like a good one.



There is more to it then just being restrictive.
It's about the pressure drop in the vapour hose back to the converter and the size of the discharge tube in the mixer.


The first misconception is that the mixer needs to be restrictive to work.
This is completely untrue.
The mixer needs to create a suitable pressure drop. There is a difference between creating a pressure drop and being restrictive and creating a negative pressure on the engine side of the mixer.

At higher RPM they are all restrictive due to the size dictated by having a good venturi effect at low air flow. Some are just worse then others, orifice type mixers are the worst offenders at being restrictive because they need to be small to get enough pressure drop at low airflow.

The next problem is the relationship between the size of the venturi in the mixer and the size of the pipe that the mixer is in. If the mixer ID is to close the pipe ID the venturi effect is lowered.

The next problem (with some mixers) is the vapour tube ID is too small to feed the engine, so the mixer become smaller to draw harder on the converter. In some cases in order to keep costs down the manufacturers will use the same mixer across a few engine. The biggest problem case is the 4.5L EFI land cruiser The AFM has the same bolt pattern as the same age 4cyl Camry. So guess what happened... That's right the camry mixer was supplied in the Land Cruiser kit.
It's to small to start with and the ID of the vapour tube is only 12mm. They ALL run lean no matter how you adjust the converter. I had a few that just would not accelerate cold and the owners had been putting up with it for years.

I drill and tap a second vapour fitting into the mixer from the other side and make a few other small changes with the mixer setup, then 'T' off the vapour hose to the second gas feed.
It's a %100 cure (mixer is still under sized) but at least you can tune the things properly after that.

There is a bunch of other 'problems' created by the need to be cheap too, but those are the main factors that effect how the mixer will behave.

 

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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Wed Nov 07, 2012 2:17 pm 
Getting Side Ways
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hmmm.. my vapour hose is all 18mm.. That is sufficient yes?


The BLOS carbs have 18mm intakes anyway, so can't do much about that.

Perhaps to run two of them... I should find a converter with a bigger outlet like a 25mm and when I can split it down to two 18mm outlets.
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 Post subject: Re: EF pings on petrol, fine on LPG.
Posted: Thu Nov 08, 2012 12:16 pm 
Getting Side Ways
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18mm is fine up to a point. By the time 18mm becomes to small you would need a second converter anyway. But it also depends on the ID of any fittings in the system.


LPG parts/kits are made to be cheap, very little thought went into making them efficient.

 

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