IMPCO start assist

Propane, Butane, LPG, GPL, C3H8, C4H10
BigBlockMopar
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Location: Netherlands
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Re: IMPCO start assist

Post by BigBlockMopar »

Some 15+ years ago, while still being young and... cheap, I rigged a "manual start-assist" on my '67 Chrysler.
With the vaporizer mounted flush to the firewall, I fabbed a wooden stick, mounted right in front of the vaporizer, that ran straight through the engine bay through an exisiting hole in the radiator frame.
Everyday on cold morning starts, I would turn on the ignition, get out and push on the tip of the stick for 2-3 seconds while listening to the propane filling the vapourhose, after which the engine started right up, everytime.

Of course these days I would use better solutions for this issue.
Like, an aluminium tube would be better then a silly wooden stick ofcourse :mrgreen: :mrgreen:
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: IMPCO start assist

Post by storm »

kikkegek wrote:
storm wrote:The injector mounted in the regulator has been around for a very long time. Here's a pic of one mounted in a B2 for a GRA setup.
g002.jpg
Cool. What part in the photo is the injector?
The injector is the part between the water inlet and outlet.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

kuchen
Posts: 79
Joined: Tue Oct 25, 2011 12:38 pm
Location: Stuttgart/Germany

Re: IMPCO start assist

Post by kuchen »

There are injectors and solenoid valves, I would refer to the one on that regulator as a solenoid valve. Injectors can dose fuel down to 3ms squirts, solenoid valves can't.
For a simple pushbutton primer, a solenoid valve is good enough.
I am currently working on a small electronic device that takes the ignition pulses and pulses a single injector say 20ms per ignition event while cranking. This is how my CNG Megasquirt starts and it works flawlessly without interaction like in a modern car. Unlike on petrol, the cranking pulsewidth is independent of the ambient temperature, as there is no wall condensation effect with gaseous fuels.
This unit is also designed to control the evaporator temperature using a NTC screwed into the Impco E and a Mercedes DuoValve to restrict the water flow. To assist the evaporation, an electric water pump is activated on very cold starts.
As the micro controller is almost idle with the tasks above, it also controls the valves of a two tank setup, computes the overall fill rate and generates a signal to drive the stock 0-90 Ohm GM Fuel Gage.
PCB is build up, program is written, needs testing - but my Cadillac was hit by a hailstorm so I have plenty of other things to do first.

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

wow, you are thinking up some cool stuff Kuchen.

curious about the results and end result
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

Sorry to bring up such an old thread, but I want to install the start assist on my 77 GMC Big Block now. Cold morning starts take about 10 seconds of cranking. The rest of the day its fine and will start before the first crank ends.

problem Im facing is that the EC-1 port on the IMPCO300 mixer will still be very far from the carb.

Thus I'm assuming it will still take a lot of cranking before the extra lpg will reach the cilinders.

So could I maybe connect the start assist at some other place?
LPG_ARM.jpg
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

OK, went ahead and installed the Start assist valve (SAV). Found a nice connection point at the carb for the feed line. The EC1 port of the 300 mixer is way to far from the carb on my setup, thus would help a but on cold cranking. The connection I now found is just above the vacuum secundairies on the back of the carb. It will be close on high vacuum, thus never causing a high vacuum load on the SAV.

I tried it yesterday and seemed to start after about 5 seconds of cold cranking in stead of 10. But Can only try once a day of course ;-)
carb_connection_impco_start_assist_valve.jpg
Reducer_connection_impco_start_assist_valve.jpg
also found out that the EC-1 port on my mixer wasnt closed of. so I threaded a bolt with some sealent in there.
EC-1_port_impco_start_assist_valve.jpg
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: IMPCO start assist

Post by storm »

The port on the carb you have chosen is designed to be used with the choke. It lets the choke pull clean air to be heated in the exhaust and then sent to the choke to heat the bimetal strip to pull the choke off once it is warm. If you still use the carb you will in effect be slowing down your choke warm up and also have provided an unfiltered vacuum leak through the choke. You can convert to electric choke but you'll need to block off the vacuum port on the choke if you don't want a vacuum leak.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

storm wrote:
Sun Feb 02, 2020 1:27 pm
The port on the carb you have chosen is designed to be used with the choke. It lets the choke pull clean air to be heated in the exhaust and then sent to the choke to heat the bimetal strip to pull the choke off once it is warm. If you still use the carb you will in effect be slowing down your choke warm up and also have provided an unfiltered vacuum leak through the choke. You can convert to electric choke but you'll need to block off the vacuum port on the choke if you don't want a vacuum leak.
thanks for the heads up. But I already converted to electric choke and dont use the carb anymore. Its only a throttle body for now.
man you know your stuff well 8)
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: IMPCO start assist

Post by storm »

kikkegek wrote:
Sun Feb 02, 2020 3:08 pm
thanks for the heads up. But I already converted to electric choke and dont use the carb anymore. Its only a throttle body for now.
man you know your stuff well 8)
lol, I wrote unfiltered air when it is actually filtered which I already wrote before that.
I'm GMH (General Motors Holden) trained, I did my apprenticeship when Quadrajets were still around. I've rebuilt more quadrajets than I care to remember.
If you don't use the carb anymore you may as well, if you haven't already done so, wind the choke off to full lean or always open. That will provide much less restriction at start up and cold running so the LPG mixer can do its job better.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

storm wrote:
Sun Feb 02, 2020 4:32 pm
kikkegek wrote:
Sun Feb 02, 2020 3:08 pm
thanks for the heads up. But I already converted to electric choke and dont use the carb anymore. Its only a throttle body for now.
man you know your stuff well 8)
lol, I wrote unfiltered air when it is actually filtered which I already wrote before that.
I'm GMH (General Motors Holden) trained, I did my apprenticeship when Quadrajets were still around. I've rebuilt more quadrajets than I care to remember.
If you don't use the carb anymore you may as well, if you haven't already done so, wind the choke off to full lean or always open. That will provide much less restriction at start up and cold running so the LPG mixer can do its job better.
Good point. I thought about that just today, when I checked if the electric choke was still working. I should disconnect that and tie the choke to full open.

I'm replacing the Quadrajet with a TBI throttle body without injectors from a 454 when I get the chance. It has IAC valve and TPS that I want to use for my transmission control and later the vapor injection Im going to add. But that TBI throttle body will be much less restrictive and will make me get rid of that long arm and fit it normally under the hood again and use the stock air filter house again
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: IMPCO start assist

Post by storm »

kikkegek wrote:
Sun Feb 02, 2020 5:59 pm
Good point. I thought about that just today, when I checked if the electric choke was still working. I should disconnect that and tie the choke to full open.
I would.
kikkegek wrote:
Sun Feb 02, 2020 5:59 pm
I'm replacing the Quadrajet with a TBI throttle body without injectors from a 454 when I get the chance. It has IAC valve and TPS that I want to use for my transmission control and later the vapor injection Im going to add. But that TBI throttle body will be much less restrictive and will make me get rid of that long arm and fit it normally under the hood again and use the stock air filter house again
Personally I'd be going for something like this with this on top and then a 425. Apart from the horrendous appearance of a tower of adaptors etc. the taller stack coupled with a streamlined throttle body would possibly increase torque due to much straighter air and gas flow. When you swap over to LPG injection you'll have a throttle body that is much better designed for good flow.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

kikkegek
Posts: 416
Joined: Thu Nov 17, 2011 2:12 pm
Location: Netherlands, The Hague

Re: IMPCO start assist

Post by kikkegek »

yeah that looks like a really nice throttle body. But those are usually 500-800 USD a piece and I bought two complete ones with injectors, IAC and TPS for $200 ;-)
Air-Gap_intake_with_GM_TBI_throttle_body.jpg
I'm building thjis on a budget, since its only for fun and some summer trips and not a daily. For my setup the TBI throttle body should flow just fine I assume. I took the injectors out, since I'm planning single fuel, so sont use gasoline for warm up. For now Im keeping the 300mixer on top for really cold morning starts. But I'm hoping I can fix cold morning starts with an inline coolant heater like the diesels use or heating the injector rail. But I'll pursue that more, when I get to installing the propane injection parts.
storage/project: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.10 gears - IMPCO425 mixer
driver/project: 1977 GMC C15 Suburban - 454 big block - 4L80E- LPG VSI - 3.08 gears
sold: 1986 Chevrolet Suburban K20 Silverado

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