I have read on here many years ago of IMPCO component sizing and that I think - running a 100 or 125 size mixer off an L converter is perfectly fine.
I have done this in prep for an engine conversion that will end up with my tried and tested 200 off the L converter, but at present it is a very difficult start. It is a case of forever cranking and holding starter while it sounds like it wants to fire, until it does fire. The mixer is actually a knock off 100, not IMPCO branded. When I test ran this mixer on a same sized 1800cc it went just great, beautiful stoich, with the exception of statioary idle mix about 16 , 17:1.
I am thinking the lean idle may be the starting issues cause, so may need a primer circuit added for cold start.
Have i committed a no no by running a small mixer off the L converter ?
I'm avoiding having to modify the brackets of the L to fit up a J or Cobra converter
thanks
IMPCO 100 sipping from L size converter
Re: IMPCO 100 sipping from L size converter
There should be no problem running a 100 off an L. We did many conversions on both stationary and over the road vehicles using 100's with L's or E's without any major issues. Based on your idle mixtures you just have a very lean mixer. Make sure there are no leaning rings installed under the diaphragm. Check the idle mixture screw is closed all the way. IMPCO has always had a problem with lean idles on 100 and 200 series but you say yours is a clone so I can't advise on that. You indicate it idles fine at these values so a primer would be the next best bet to solve the starting issue.
Re: IMPCO 100 sipping from L size converter
On cold start L with 425 mixer I run high 16 low 17s at idle and low cruise speed (25/ 30 mph)
once the engine starts to warm up these drop back to low to mid 16s.
I dont think that is your problem on hard start...
the issue of hard cold start on LPG has been discussed several times... and consencis of many (assuming what C8H8 says above is all ok) is the length of the pipe feed between them has influence...
If left over night or extended time the LPG 'bleeds out of the system. converter thru to the inlet manifold.. which requires a bit of turning over of the engine to get enough gas thru all that into the cylinder to fire..
If u say, give the engine a squirt of either /engine start , before turning over.. u wil find it fires damn near instant.. resulting in the engine turning over the same , or more than the number of times u do on the starter , very quick, therefore runs on the LPG without hesitation....
If u use a high torque starter, which also turns the engine over very fast, the fire up again is very quick.
In the impco manual tuning in the old 1980s obsolete EC1 converter lean addon , one sets the cold start up lean and it also richens up as the engine does...
the opposite to what we know when it comes to petrol...
once the engine starts to warm up these drop back to low to mid 16s.
I dont think that is your problem on hard start...
the issue of hard cold start on LPG has been discussed several times... and consencis of many (assuming what C8H8 says above is all ok) is the length of the pipe feed between them has influence...
If left over night or extended time the LPG 'bleeds out of the system. converter thru to the inlet manifold.. which requires a bit of turning over of the engine to get enough gas thru all that into the cylinder to fire..
If u say, give the engine a squirt of either /engine start , before turning over.. u wil find it fires damn near instant.. resulting in the engine turning over the same , or more than the number of times u do on the starter , very quick, therefore runs on the LPG without hesitation....
If u use a high torque starter, which also turns the engine over very fast, the fire up again is very quick.
In the impco manual tuning in the old 1980s obsolete EC1 converter lean addon , one sets the cold start up lean and it also richens up as the engine does...
the opposite to what we know when it comes to petrol...
My Spelling is Not Incorrect...It's 'Creative'
Re: IMPCO 100 sipping from L size converter
these impco systems are very fickle on the down low mixtures and in the L and the E it is all to do with the height of the lever from the lid
a slight bend on the arm and it will change the starting and idle mix but have less effect on the total mixtures
on the E ( not sure of L ) you also have different spring options to subtly change the vapour pressure ( on all the mixture range )
else you can use a solenoid off the top deck for enrichment and for cold start or you can use one of the plunger type solenoids that press on the primer button
a slight bend on the arm and it will change the starting and idle mix but have less effect on the total mixtures
on the E ( not sure of L ) you also have different spring options to subtly change the vapour pressure ( on all the mixture range )
else you can use a solenoid off the top deck for enrichment and for cold start or you can use one of the plunger type solenoids that press on the primer button
when the going is hard, don't retard, remember your lubrication
Re: IMPCO 100 sipping from L size converter
Yes, thanks, I must say I left out a few details,,,,
when I tested the 100 mixer copy that is brand new, was on same type engine group, replacing a 125 mixer for a testing moment. It started on a warm op temp engine with a Cobra J converter, so never had to do a cold start.
Must say I have never added a primer to any impco set ups - might be a first
idle adjust screw was screwed all the way in !.
Thought that newer copy - png tech ? might just be leaner for modern day applications such as fork lifts ...
the vaour hose from the known L converter is less than a foot and the plenum? volume is less than before- lessened by about 18" of 50mm metal tube between the mixer and top box on the twin carbs, which is a 2x4x10" closed off metal box.
Compression on the engine is 190 - 200 psi cranking speed, so should be good suction, oh , and given the vacuum safety locks now dearer than electronic safety switches not playing with needing correct vacuum to get it going.
Next trick is to try the 200 mixer that was working with the L before on same capacity turbo engine.
Oh, and comment on overnight bleed or dropping out of combustible mix ....once fiddling - I replaced carburettors as the throttle with an efi throttle body and used 2" pvc pipe - about 2' of it, silicone joiners/bends etc and only did one cold start on this dodgy experimental arrangement - that one start up on a below zero C morning - was instant! Unsure if it was the totally closed off TB or whether the plastic ducting insulated the mix better than metal or alloy ducting ?
Will never know
when I tested the 100 mixer copy that is brand new, was on same type engine group, replacing a 125 mixer for a testing moment. It started on a warm op temp engine with a Cobra J converter, so never had to do a cold start.
Must say I have never added a primer to any impco set ups - might be a first
idle adjust screw was screwed all the way in !.
Thought that newer copy - png tech ? might just be leaner for modern day applications such as fork lifts ...
the vaour hose from the known L converter is less than a foot and the plenum? volume is less than before- lessened by about 18" of 50mm metal tube between the mixer and top box on the twin carbs, which is a 2x4x10" closed off metal box.
Compression on the engine is 190 - 200 psi cranking speed, so should be good suction, oh , and given the vacuum safety locks now dearer than electronic safety switches not playing with needing correct vacuum to get it going.
Next trick is to try the 200 mixer that was working with the L before on same capacity turbo engine.
Oh, and comment on overnight bleed or dropping out of combustible mix ....once fiddling - I replaced carburettors as the throttle with an efi throttle body and used 2" pvc pipe - about 2' of it, silicone joiners/bends etc and only did one cold start on this dodgy experimental arrangement - that one start up on a below zero C morning - was instant! Unsure if it was the totally closed off TB or whether the plastic ducting insulated the mix better than metal or alloy ducting ?
Will never know