Adding an elec. fuelpump to an Impco vaporizer+425 setup

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BigBlockMopar
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Fri Jan 04, 2019 7:20 pm

The restrictor-plate has been removed in the 425. This was one of the first things I did.
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'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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Fri Jan 04, 2019 10:30 pm

C3H8 wrote:
Fri Jan 04, 2019 5:51 pm
Bennet's LPEFI system was sold to Schwan's Food Delivery company which operates thousands of trucks.
Not the same guy then, The guy I was referring to (from memory spelled Bennett and some, including myself, confused him with Dave Bennet from Yella Terra) had a website and he was based in Australia. The website is long gone.
BigBlockMopar wrote:
Fri Jan 04, 2019 7:20 pm
The restrictor-plate has been removed in the 425. This was one of the first things I did.
It's not something basic like the gas valve is it? Is it the right valve? is it lifting fully?

How much HP is your engine making throughout the rev range?
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Sat Jan 05, 2019 6:27 am

The 360ci put out a max 234hp on the wheel-dyno last year.
Here's the chart (I notice the AFR' are leaning out even before 4K rpm.)

Image
Last edited by BigBlockMopar on Wed Jan 09, 2019 2:56 pm, edited 1 time in total.
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'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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Sat Jan 05, 2019 12:58 pm

Looking at that afr curve 3 things come to mind.
1 you are running very rich under 4000 RPM (just my opinion).
2 if that was a petrol powered car I'd say your fuel pump isn't keeping up above 4000 RPM. To fix that I'd rewire it to get full battery power via relay and/or fit a bigger pump (in the case of LPG bigger fuel line from tank to regulator and the best flowing lockoffs I could fit). However I'm not convinced that is the issue.
3 high compression engine with a dramatic change, there is nothing gradual about that change, of AFR reading below VE is a good indication of the ignition not being powerful enough for the job.

If I were you I'd run 8mm, at least but preferably 10mm, fuel line from the tanks to the reg. Find the best flowing lockoffs you can and fit them. If the problem still occurs on the dyno check and upgrade the ignition system so it can keep up with high cylinder pressures created by >11 to 1 compression ratio.
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Sat Jan 05, 2019 5:59 pm

The AFR curve shown is based on Gasoline AFRs.
In this case I would rather have seen the actual Lambda-value, which can be converted to the proper value afterwards.

Installation of an 8mm line is in the works, as well as a new 8mm lockoff and IMPCO filter/'storage pot'.

I have no real doubts about the ignition system myself. I think misfires would show up as a more jagged line on the dyno-chart, and not show as a gradually leaning out AFR. And I know what they feel like.
With the digital ignition I have full control over the coil's dwell time and sparktiming.
The coil is an MSD e-core coil. It is fired by a relayed powered 7-pin HEI module, which again is controlled by the MegaSquirt ECU controlling timing and dwell-time.
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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by Steptoe » Sun Jan 06, 2019 3:31 pm

Couple comments on posts above
Leaning out..
On my basically std , built for LPG 350, on data logger.. real time and recorded, it would start to lean out around 4500, 4800 was getting to be of concern, then as happens in real life on road.. ie passing a long cattle truck (approx 45 mph) and trailer (very long in NZ ) one is backing off to pull back in before rpms and end of truck...well over 100mph.
I believe this was in the 450 mixer rater than the lock off, as I had to re machine the lock off due to worn case/ pin, and did so to a larger diameter.. cant rem what ended up with but made no difference on the data logger.
I also messed with spring weights etc inside the 450 mixer, it made changes but not to the leaning out range.

Pumps.. posts by Frank CH .. on pump.. I dont se it being a soln to the problem... the problem I see is the liquid in the tanks climbing the walls, leaving the pickup uncovered by liquid in the bottom...Also applies to race cars , straight line and track, climbing rear of tank and/ or up the sides in long cnrs, and the initial acceleration out of a cnr where rate of acceleration is greatest... and being noticable when further down the track as fuel is held up high.

Fuel line diameter/ length acceleration... Again happens predominantly in straight line track cars...baffles fuel tanks.. The weight of the fuel over comes the inlet suck power of a pump mounted up forward... or the pressure of a rear mounted is less than the pressure created by a tank/ rear mounted pump. A non return valve doesnt help actual delivery but will help to have fuel resupply when the pumps , suck/ pressure is greater than the forces from acceleration... which in most real would cases is too late.
I dont believe this would apply under normal operating conditions, but may apply under low temps. Under normal operating conditions the tank pressure would be greater than the G forces applied by acceleration....as temps decrease so does that pressure.
Fuel line diameters.. same as for petrol.. too small creates restriction, requirement for bigger pumps, issue of 'stored' volumes withing the line.. ie recover after fuel has climbed up the side/ back of the fuel tank.

I dont see his issue any different to that of petrol tanks , delivery pressure / draw or fuel lines size. .. except under abnormal operating temps.
Get the fuel climbing the tank walls/ sides sorted... then maybe the fuel line diameter maybe also an issue, thu I doubt it under normal temps.
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Sun Jan 06, 2019 5:48 pm

There are probably 2 different problems here. The 1st being the stumble that prompted the creation of this thread. The 2nd being the mid to high RPM lean out as shown by the dyno graph.

Sorting out the tanks may have a positive effect on the 1st. The 2nd needs investigation and will also probably have a positive effect on the 1st.

The way I see it leaning out at well under VE rated CFMs means a mismatch of parts causing a restriction.
In Australia an AMR lock off GL30 (most common usage) will support 400 HP at the crank, Century lockoffs apparently flow more but do not fit our tanks. AMR has a 3 mm seat some people drill them with a 3 mm drill to ensure manufacturing tolerances are all within spec. Testing with water on redrilled seats apparently shows an increase in flow potential. I don't know what lockoffs are used in Europe so cannot comment on them.

The 360 is putting out 234 HP at the wheels, assuming 33% drivetrain losses the engine is putting out approx 351 HP at the crank. What HP can a 425 flow? The manual says 287 HP at 460 CFM at 1.5"HG depression or 333 HP at 533 CFM at 2" HG depression. I have no doubt a 425 will flow more HP but the depression (i.e. restriction to airflow) will get higher (vacuum gauge or MAP reading would be very helpful). What regulator is fitted to the combination. An L will flow 325 HP peak, 200 HP continuous, an E flows the same. 351 HP at the crank outflows the mixer and regulator, assuming the reg is an E or L I have no doubt there are margins with these numbers that probably mean they will flow more (C3H8 do you know the absolute limits of these products?) but their rating is at these numbers is a starting point.

I'd start with the point of highest restriction (6mm fuel lines running full length of car) and work my way from there.
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Mon Jan 07, 2019 3:13 pm

Regulator is an E.
I have datalogs from most of the dynoruns.
kPa was ranging from 93 to 83 kPa during the dynorun (1.5" to 4.5" vacuum).
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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Mon Jan 07, 2019 5:10 pm

BigBlockMopar wrote:
Mon Jan 07, 2019 3:13 pm
kPa was ranging from 93 to 83 kPa during the dynorun (1.5" to 4.5" vacuum).
That's "HG, you have a vacuum restriction. 4 barrel carbs are measured 1.5" HG, 2 barrel and 1 barrel carbs are measured at 3" HG. the 425 with a 4 barrel baseplate should flow approx 450 cfm at 1.5" HG. You are in effect forcing it to flow more but at a higher vacuum. You have untapped HP in that engine if you could free up that airflow restriction but having said that you still need to supply enough fuel to feed it and that may require another regulator.

Have you got a chart for RPM, 100% TPS, and vacuum?

EDIT: A couple more questions for you.
Is this reading with an air filter? If yes, what are the air filter dimensions? Is it in an OEM housing or is it open?
What baseplate do you have on the 425?

The reason I ask is the 425 should be big enough for your engine up to approximately 5000 RPM.
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Wed Jan 09, 2019 3:33 pm

The housing is a stock late '70s unit from a Chrysler with 400ci 4-bbl engine. Attached to the housing is large diameter tubing routed to the front of the car through the radiator-support.
But, we tried with and without airfilter housing, made no difference at the time.

Baseplate is a stock-type Holley 4-bbl plate.
Looking at the pic I remembered there's also a 1" 4-hole spacer under the 425. This improved throttle-response.

Image

Below is a screencapture of the log-file.
No TPS-sensor present.
The redline is "kPA", which is engine-load. This is inverse-related to engine-vacuum.
Engine load decreases slightly during the run as the RPM climbs.

Image
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'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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Wed Jan 09, 2019 7:58 pm

BigBlockMopar wrote:
Wed Jan 09, 2019 3:33 pm
The housing is a stock late '70s unit from a Chrysler with 400ci 4-bbl engine. Attached to the housing is large diameter tubing routed to the front of the car through the radiator-support.
But, we tried with and without airfilter housing, made no difference at the time.
Interesting, can't really tell from the picture how large the intake is but there are sites that show how restrictive OEM air cleaner housings are. I am surprised there was no difference with no air cleaner housing but that may be an indication the 425 itself is a restriction.
BigBlockMopar wrote:
Wed Jan 09, 2019 3:33 pm
Baseplate is a stock-type Holley 4-bbl plate.
Traditional Holley 4150/4160 style baseplates come with 4 different size butterfly plates. I've not seen anything on the net that shows what each size flows but there are 4 throttle bore sizes for 4150/4160 style carbs (1 1/2", 1 9/16", 1 11/16", and 1 3/4").
BigBlockMopar wrote:
Wed Jan 09, 2019 3:33 pm
Looking at the pic I remembered there's also a 1" 4-hole spacer under the 425. This improved throttle-response.
I remember you posting about that.
BigBlockMopar wrote:
Wed Jan 09, 2019 3:33 pm
No TPS-sensor present.
I hope you are going to fit a TPS when you fit the LPG injection. It is difficult to analyse without a TPS, the driver may think they are getting WOT when they are not. TPS also helps with failsafe if other systems go down with EFI.
BigBlockMopar wrote:
Wed Jan 09, 2019 3:33 pm
The redline is "kPA", which is engine-load. This is inverse-related to engine-vacuum.
Engine load decreases slightly during the run as the RPM climbs.
The reduction of load (lowering of kPa) can be because of 1 of 2 things. 1, 425s are essentially a vacuum operated carburettor so some level of vacuum is required for them to operate this changes as vacuum signal changes. 2, the airflow restriction is creating a higher vacuum (lowering the kPa) indicating a drop in engine load. In an ideal world the vacuum reading should not be higher than 1.5" HG at WOT during the engines operating RPM with a 4 barrel base plate. Anything higher than 1.5" HG (e.g. 2" HG) indicates a restriction of air flow and this limits potential power output.

Assuming the throttle is opening 100% you have an intake airflow restriction somewhere above the baseplate. If running the engine without an air cleaner does not change anything then the restriction is the 425 itself. This may be because of the vacuum operation of the gas valve.

Here's a video of a Holden 253 (4.2 litre) with a 425 at WOT from idle to 5000 RPM https://www.youtube.com/watch?v=vb9oqHr4U00 I am wondering if your gas valve is opening fully.
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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by gottago » Wed Jan 09, 2019 9:19 pm

Hey been awhile since I've looked in here. Good to see some action still happening. Global warming increased emission checking etc on the way. Propane may outlast petrol by the time its all said and done..

See lots of good advice and numerous things to check in regard this setup. I have a friend who used almost that same cam in a 400 cu.in. 12:1 engine. He too had advanced the cam when first installed. It had gobs of low end torque but signed off well below 5000 rpm with a single 450 mixer. Last year during a reseal, he was convinced to try the cam in a retarded position. He notes very little difference at low rpm but a much stronger mid to upper rpm range. He had an afr gauge in the vehicle at all times but can't recall the original afr readings prior the cam being retarded. Now it leans out at 5200 rpm but he says it is much nicer to drive and always surprises him when he steps on it. Not exactly applicable to whats happening here but there are limits to everything including the smaller duration cams which have their own peculiarities and can amplify other conditions. Just something to keep in mind. It can get a bit confusing but you have some good advice on what to check and test.. Hang in there.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by C3H8 » Thu Jan 10, 2019 1:55 pm

Sorry, I can't remember the highest HP we ever achieved with a 425. I vaguely remember hitting 280 RW. I believe it was with a Dodge 440 but with a really aggressive rear end set up. Keep in mind all of our testing at our research center was strictly on OEM engines built in the 80's and 90's. Most of the engines were relatively low rated HP compared to today's engines and we did not test any modified engines. Most times we had engines that topped out at a maximum RW hp of 150 to 205. And, in most of these cases the rear end gearing was in the normal ranges found on automatics with OD transmissions. In the end I can only point back to the IMPCO manual and the numbers Storm referred to. I can say that on the dyno and using a really high quality gas analyzer we always had very good AFR numbers with the 425's. The only issue we had was higher rates of wear when they had to be mounted on their sides, which is to be expected of course.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by BigBlockMopar » Thu Jan 10, 2019 3:14 pm

Storm,
The throttle fully opening was the first thing I checked before doing the dyno-runs. I always try to learn from other's mistakes I happen to come across :)

Here's a pic of the throttle plate. Don't know the bore diameters but I have a spare one to measure on.

Image


The large air filterhousing on the engine with its 'budget' cold air intake...

Image


When EFI will be installed, a TPS will find its way onto the engine as well.


-

The cam is installed (degreed) according to the camcard.
I wanted to focus mostly on torque in this engine at the lower rpms (<3500), since that's where it spends its life at about 99%.
I could try and play with camtiming in a program like Desktop Dyno for instance to see if it thinks it will do much for the HP-number.

All the dyno runs were done in 2nd gear, in fear of the transmission kicking down another gear. Which still happened occassionaly during the first few runs. Besides readjusting the kickdown-level a number of turns, the dyno-operator in addition also kinda rolled into the throttle at the start of a run, which did skew the numbers down a bit most likely at the lower rpms.

On a related note;
I have a pair of aluminium heads on order, which I plan to install.
The heads currently on the 360ci engine are actually 318ci heads with small ports. These alone could act as a restriction on the engine perhaps, but I don't think believe the heads alone will cause an obvious lean out above a certain rpm.
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.

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Re: Adding an elec. fuelpump to an Impco vaporizer+425 setup

Post by storm » Thu Jan 10, 2019 9:28 pm

The heads may be a restriction but they aren't the restriction that you see in the logs. Vacuum reading is taken under the throttle plate so the restriction in the logs is above the location of the vacuum reading. If the heads were the restriction you would feel a definition rpm limiting (old VW Beetles suffered this badly).

The air filter housing snorkel would be a restriction eventually, it may even be a restriction now. I, personally, like a 4" or equivalent, "neck" that feeds to a cold air source. In Australia HDT fitted large snorkel Chevrolet air cleaner housings to their engines because the OEM Holden air filter housing snorkel was tiny in comparison.
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