I have no idea with LPG, so just tell me if I'm making no sense, or sound like a d**k

Anyway, on my car, dual fuel setup, the gas feeds directly into the airbox.
This has always seemed weird to me.
Shouldn't there be some sort of mixer or something in the intake piping that it feeds into?

It runs s**t on gas, idles like a dog, takes ages to start, and at idle, gas can be strongly smelt from the exhaust(is that normal?)
Because of thse problems, I always avoid using gas.
only use it when I'm poor, or running dangerously low on petrol.

So what I'm wondering is, would a better system of feeding the gas into the intake help with these problems?
I'll grab some pics in a tick and post 'em up...

i HIGHLY doubt it feeds into the air box.
there is usually a pipe between the airbox and converter called a balance pipe, but thats it.

never heard/seen a system where it feeds into the airbox...I don't know much about Gas myself, but on my car the mixer is a part of the intake piping. The Gas smell is just the exhaust fumes and is normal. Stand behind a taxi and see what i mean. It shouldn't run rough or take ages to start as well. I'd say thats a tuning problem

or is it called a converter? i dunno

If you can smell the gas strongly you most likely have a tunning issue. LPG does need readjustment perodically to account for the wear of the diaphrams in the convertor, this varies dependant on many factors. You don't need to have a discharge ring to run on LPG but it definitely runs better. I find it easier to get the mixtures spot on when I work on forklifts which have the discharge ring as opposed to a pipe mounted into the carby bonnet.

Yes EFFalcon, you're correct, after closer inspection (I really detest the LPG system on my car, so I just kinda pretend it's not there) it's not the LPG line.
It's some other f**k thing.
It literally just threads into the box with a brass fitting.

Also, has anyone ever heard of LPG fitting requiring the complete removal of any form of CAI?
Originally, it had not only an aluminium plate riveted in blocking the snorkel, but also a big a** holedrilled into the snorkel to suck hot engine bay air...
Plate was easy, just drilled out the rivets.
For the hole, I orignally tried bending a piece of plast and siliconing it in, but after multiple accidents with the heatgun, and the realisation that silicon really doesn't work sticking plastic to plastic, I grabbed the good old electrical tape and gave it a good wrapping

Anyway, heres some pics...

 

 

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File comment: Brass fitting into airbox jareds gas 001.jpg [ 45.31 KiB | Viewed 249 times ]

Also should mention, it goes over the TB, then under the manifold runners somewhere.
Don't know where it GOES to...

The hose going to the air box is a balance line. It goes to the converter and has something to do with measureing the air pressure and adjusting the LPG accordingly.

when i bought my Ef there was no snorkel, fitted an AU XR8 one, and the car just stalled. Had to have the system retuned to run with it!

The line to your air box is a balance line - it's part of the LPG, tells it the air pressure or amount or air or something along those lines. The picture looks like a crude version, usually there is a brass thingo mounted on the side and it usually hooks in to help catch the air, but same thing i guess.

At currentl petrol prices you might want to consider getting your system running well. And by the way, when they do run well you'll love em.

As for your exhaust gas, it might be running rich hence the extra stong LPG smell. But you will find the exhaust out of an engine running on gas will smell very different to one running on petty, so don't worry about it too much.

Starting on gas, don't bother, if your cars duel fuel, try to start on petrol, your car will start better, and it'll help to keep your injectors clean/unblocked.

Speaking of looking after the injectors - an interesting thing that I found out my LPG controller unit can do is that you can set it to automatically switch back to petrol (for just 2 minutes) every 15 minutes of running on LPG - to help maintain your petrol system. Personally I wouldn't bother, but was interested to find that out...

The tube to the air box is a balance tube - it prodides a reference for the pressure regulator (near 0 PSI).

The actual LPG is fed into the aluminium thingo (mixer) on your car. There should be an electronics box someplace controlling the LPG via a valve in the LPG line from the mixer to the regulator.

There is no reason that you should have those problems or more than a marginal loss of performance with the LPG system. I actually have MORE power with LPG than petrol - 2.5kw more, but more.

Get the car to somebody who knows LPG and performance. My local GAS Research (Hoppers Crossing) outlet is doing a TT 6.6 LPG powered street car. They have been very helpful (but busy).

Dave
Happy GAS Research customer

Cheers guys!
Yeah, I need to look at getting it tuned properly.
Actually, when I fixed the CAI it seemed to improve idle slightly.
Got an XH snorkel coming, so I'll whack that on, then head to somewhere to get it tuned.
Out of pure curiosity, I don't intend on trying it, but how hard are gas systems to tune, and how is it done?
Are there adjusting screws in the converter, or can that solenoid thing in the gas line be adjusted or what?

Most non electronci LPG systems have an idle mixture (same as carby), and a max gas flow adjustment (think main jet in carby terms). From there the options are limited to the type of system.

As a result it can be experimental getting the right mixture under varying load conditions. A dyno operator with good LPG expereince on your system is a big plus.

Electronically controlled LPG mixer systems CAN be more accurate, but the main advantage is the loss of the restriction in the induction system. This is the reason my wastegate senses AFTER the IMPCO LPG mixer (and intercooler) but prior to the throttle body.


Dave

Yeah, I've read somewhere before that for accurate LPG tuning a dyno and four-gas analyzer are pretty much necessary.

Where would the idle mixture adjustment be lc_80?
I can post some more pics of the system when I get home, atm I'm at work.
It's the idle that is really the main problem.
I can live with a slight reduction in low-down torque (which is what it suffers from on gas, it actually isn't that bad towards the top end)
It's just when you have to left foot brake at traffic lights and give it some throttle to keep it running that s**t me up the wall.

Righto all you LPG wiz's, is it within the realm of possibility for LPG hating me to adjust the idle mixture on this convertor so as to achieve an acceptable idle?

 

 

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What you have a pic of appears to be the convertor/regulator, not the mixer (thats the first pic yesterday at 18:58).

I have attached a pic of the IMPCO 225 mixer. The idle screw is the one on top.

For those with forced induction, I have included a pic of the balance tube connecting to the regulator. You DO need the metal top plate for the convertor, otherwise the pressure (boost) will cause it to leak & eventually crack. Thats a 1/2" balance hose I've used. This keeps the mixture consistant across most of the rev / load / boost range (low boost for continous duty use).


Dave
ENG-TEK

 

 

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File comment: IMPCO 225 Idle screw IMPCO-225-Idle.jpg [ 92.67 KiB | Viewed 240 times ]