LPG Carb options.

[amichie]

OK here is my dilema.

I have a impco 225 LPG carb on my 7mge. I have found that it is too restrictive and since the air flows through it regardless if its running on LPG or unleaded it affects the performance both on LPG and on unleaded.

The impco 225 is rated to 329cfm. This sounds like enough but if I remove it and put the put the plastic pipe back on I get a noticeable improvement in performance on unleaded above about 4500rpm.

So the question is what is the simplest upgrade option.? I am not considering gas injection as the cost would be too high.

See pic below

[celicapain]

its got to sit inline between the throttle body and air flow meter no?
id sat an 425 impco, proabbly a bit to big but a 300a would be a bugger to fit and GRA stuff is fairly pricey

[cambelt]

Impco 425 all the way , ive done it many times on a 7M but there are tricks to it , pm me
Dave

[amichie]

Impco 425 all the way , ive done it many times on a 7M but there are tricks to it , pm me
Dave

OK. So what about my converter. I have a model j that I think is only rated to 75kW.

What model converter would you recommend??

[mrshin]

Crusty old B2 should do it

[amichie]

Thanks. Somebody please rep these guys. For some reason I can't do it.

Cambelt Dave.

Can I give you a call?

I will PM you for a number.

[cambelt]

Your model L will be fine .
Dave

[stradlater]

i have a modified b 2 for sale. Get gra would be my recommendation.

[amichie]

Your model L will be fine .
Dave

I have a model J, not a model L.

I found a link on some US site that said it was for up tp 75kW.

[amichie]

This is how restrictive these LPG carbs can be.

http://www.youtube.com/watch?v=Pwgj6tAXDJw

[cambelt]

Sorry i am blind , whoever fitted that to a 140 KW motor should know better . So yeah L or OHG , B2 whatever you get off ebay will do but to buy a 425 and a L it will cost $700 for the pair . $150 of that is adapters for it to work on a 7M . GRA is better but more work to keep in tune and about $900 for both bits . GRA is still a restriction to the intake ( all except injection is) The best part of impco stuff being variable feed mixers is better economy than GRA ans set it up and forget it . the power increase over a 225 is about 10 % . If you just put a L on your car that may be all your looking for.
Dave

[amichie]

Sorry i am blind , whoever fitted that to a 140 KW motor should know better . So yeah L or OHG , B2 whatever you get off ebay will do but to buy a 425 and a L it will cost $700 for the pair . $150 of that is adapters for it to work on a 7M . GRA is better but more work to keep in tune and about $900 for both bits . GRA is still a restriction to the intake ( all except injection is) The best part of impco stuff being variable feed mixers is better economy than GRA ans set it up and forget it . the power increase over a 225 is about 10 % . If you just put a L on your car that may be all your looking for.
Dave

OK. I think my performance on LPG is mostly limited by the converter. On the dyno it got very lean when revved out. Even with the little rich lean bolt thing turned around to max.

Dave, can you recommend an IMPCO dealer for the parts and adpaters or should I just go to ebay.

[cambelt]

Just get a standard B2 not a modified one or a standard L off ebay , new B2,s are $220 and i think L,s are $260
Dave

[amichie]

Hi Dave or any body else.

I have a question about closed loop controllers.
I know they regulate the vapour fuel supply pressure to the carb by bleeding atmos pressure into the converter through a solenoid valve called an FCV.

Does anybody know what frequency the IMPCO commander drives the FCV valve at?

I know it regulates by controlling the duty cycle but at what frequency does it open and shut the valve?

Seems like it would be pretty simply to make one based on the oxygen sensor output.

[cambelt]

They allready hook into the oxy sensor . I havent seen one that doesnt . The best gas fuel control is the Global LBL as it bleeds gas vapour into the motor instead of the normal way of trying to pull the diaphram leaner .
Dave