drilling LPG injector bigger, but loosing power

Propane, Butane, LPG, GPL, C3H8, C4H10
storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: drilling LPG injector bigger, but loosing power

Post by storm »

Resistance of plug leads.
Coil output (pull the lead off each coil 1 at a time during the misfire to see what coils are not firing enough).
General integrity of wiring.
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: drilling LPG injector bigger, but loosing power

Post by kikkegek »

I just recently uppgraded the complete ignition system to D585 LS ignition coils.

All wiring is brand new. Even checked continuity recently, because of a different problem I was chasing. Plug wires are also brand new.
LS_truck_D585_coils_driverside.jpg
[youtube]https://www.youtube.com/watch?v=n13QNC5Y0hM[/youtube]

Im suspecting the injectors or the peak&hold boards for some reason. Its acting exactly like when I replaced the 2 ohm injectors with these 3 ohm Valteks. I had to upgrade the Rsense resistor in the P&H adapter to get the injectors to respond correctly to the P&H boards.

[youtube]https://www.youtube.com/watch?v=G29iRxUa77w[/youtube]

with adjusted Rsense
[youtube]https://www.youtube.com/watch?v=YXcEGOAAwKg[/youtube]
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: drilling LPG injector bigger, but loosing power

Post by storm »

I'm just going by the evidence in the screenshot that clearly indicates an ignition issue before the other signals change. To my logic, which is not fullproof, If it was an injector or another part of the fuel system the first thing to show in the gauge timeline would be one of them rather than an ignition misfire.

I know the ignition testers work, I've got 2 for wasted spark systems, and they are a great tool but they don't always show what the problem is. The only way to test properly is to pull a plug lead while the engine is running and misfiring, just be careful not to get zapped because it hurts :shock:
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: drilling LPG injector bigger, but loosing power

Post by kikkegek »

That's the thing. Engine idles fine and is good up to 30%tps... So pulling leads at idle will not do a thing.
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: drilling LPG injector bigger, but loosing power

Post by storm »

kikkegek wrote:
Wed Jul 07, 2021 2:57 am
That's the thing. Engine idles fine and is good up to 30%tps... So pulling leads at idle will not do a thing.
I'm going to quote myself so it's clear I never said do it while the engine is idling :P
storm wrote:
Wed Jul 07, 2021 2:22 am
The only way to test properly is to pull a plug lead while the engine is running and misfiring, just be careful not to get zapped because it hurts :shock:
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: drilling LPG injector bigger, but loosing power

Post by kikkegek »

hahahaha...how am I going to pull plug leads under loads over 30% TPS on the road hahahaha
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: drilling LPG injector bigger, but loosing power

Post by storm »

kikkegek wrote:
Wed Jul 07, 2021 4:07 am
hahahaha...how am I going to pull plug leads under loads over 30% TPS on the road hahahaha
dyno :wink:
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

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

Re: drilling LPG injector bigger, but loosing power

Post by storm »

Been thinking about this through the night, when I should have been asleep.
What's your plug gap? Try changing the gaps on all the plugs to smaller gaps.
Many OEMs are now about 1.5mm, go down to 1.3mm and test it, then try 1.1mm and test it, then try 1mm and test it.
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: drilling LPG injector bigger, but loosing power

Post by kikkegek »

ignition is fine.

I went to a friend with a scope. He had no experience too bad, but we made a image of the voltage signal. He didnt have a current probe.

Is this OK?

this was idle, 700rpm and about 10ms puslewidth was commanded.
scope_voltage_700rpm_10ms_valtek30bfc.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: drilling LPG injector bigger, but loosing power

Post by storm »

If the problem happens under load you're not going to see it at idle.
You really need to do the tests under load where the engine is misfiring.
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: drilling LPG injector bigger, but loosing power

Post by kikkegek »

FIXED IT!
Only 70% duty cycle at WOT at allmost 4300rpm and LPG pressure is still around 150 kPa...BOOM!

When I got my injection setup installed I had 2.65mm nozzles that resulted in over 100% (sometimes 108%) of duty cycle at full throttle and lpg pressure dropped.

Replaced the reducer. Fixed the LPG pressure. But still had duty cycle of over 100% at WOT.

The bought bigger Valtek 30 BFC injectors, but ever since was chasing weird tuning problems. Then tried to increase the nozzle size from 2.65mm to 3.04mm . That resulted in really weird lean spikes at low rpms when stepping on the throttle.

Finally decided to swap the coils on the injectors. Original ones had 2 Ohm and Valteks are 3 Ohm. No improvement. The deiced to just swap the whole top part. So coil and the part where the pintle moves inside. And voila...

Idle is now back down from 11ms to only 6.5ms at 675rpm and full throttle is around 70% duty cycle and only 20ms.

Im so glad I got this figured out. Still no clue why the 3 ohm coils dont work with this Peak&hold setup. But dont really care for now ;-)
Valtek 30BFC and Femitec 2 ohm coil and pintle.png
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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