drilling LPG injector bigger, but loosing power

[kikkegek]

hi guys,

i have nog been around a while. Been tuning my LPG injection setup:
Im keeping update in my MSEXTRA topic:
https://www.msextra.com/forums/viewtopi ... 4cd5e0853e

I was having 105-110% duty cycle at max rpm, that is around 4500 rpm with my Big Block and wanted to fix that. My reducer has more then enough power for my engine and pressure is fine. So wanted to drill out the injector nozzles a little more.

They were 2.65mm and I opened them up to 3mm. It didnt fix it. I changed nothing after reinstalling, started my engine and thought I noticed the wideband correcting and adding fuel. At first I thought could be low pressure in my LPG tank, but then took it for a spin and it wont pull over 30-50% TPS and or about 2000-3000rpm. It will get very bad lean spikes and stutter and puff really bad...

I then thought it could be the nozzles I had used in my intake. So i replaced them with the little bit bigger nozzles that came with the Valtek 30 BFC injectors. But theat also didnt help.

I have had nothing but trouble with these Valtek 30 BFC injectors. So Im at the point of tossin them and getting other bigger injectors. But hope somebody can share a light on it, maybe there is something Im not seeing?

[storm]

They were 2.65mm and I opened them up to 3mm. It didnt fix it. I changed nothing after reinstalling, started my engine and thought I noticed the wideband correcting and adding fuel. At first I thought could be low pressure in my LPG tank, but then took it for a spin and it wont pull over 30-50% TPS and or about 2000-3000rpm. It will get very bad lean spikes and stutter and puff really bad...

Bearing in mind I have read your MS forum thread I am wondering if you have changed the injector setting in TunerStudio yet. If you have what did you change it to? What you are describing are classic symptoms of incorrect injector settings in any tuning software. Also I am wondering if your injector dead times would change because of drilling the injector out.

Have you changed the tune itself since this change?

[kikkegek]

nope, I havent changed anything in the settings. nothing. I wanted to see if it would go rich, because of the bigger flow.

[storm]

If your duty cycle was 105-110% WOT @ 4500 rpm with a 2.65mm orifice your settings were out to begin with. It isn't uncommon to see 101 or 102% but any higher indicates an incorrect setting. Before you drilled them out to 3mm what was the AFR reading at WOT @ 4500 rpm?

It is possible, because in effect you have not told the ECU you have changed anything, you have gone so rich that the O2 sensors are "confused" and read lean due to higher amount of fuel burn changing the exhaust gas composition. I've seen it happen on E10 (but that is an oxygenated fuel) so wonder if it could happen on LPG. This is just a theory and is probably implausible.

What you need to do is calculate your fuel flow and change your settings in TunerStudio. Just as an aside what's the internal size of your hose between the injector fittings you drilled out and manifold fittings?

[kikkegek]

If your duty cycle was 105-110% WOT @ 4500 rpm with a 2.65mm orifice your settings were out to begin with. It isn't uncommon to see 101 or 102% but any higher indicates an incorrect setting. Before you drilled them out to 3mm what was the AFR reading at WOT @ 4500 rpm?

14.5 - 15.0

It is possible, because in effect you have not told the ECU you have changed anything, you have gone so rich that the O2 sensors are "confused" and read lean due to higher amount of fuel burn changing the exhaust gas composition. I've seen it happen on E10 (but that is an oxygenated fuel) so wonder if it could happen on LPG. This is just a theory and is probably implausible.

it runs fine below 30-50% TPS. But when I slowly increase the throttle

see this log:

What you need to do is calculate your fuel flow and change your settings in TunerStudio. Just as an aside what's the internal size of your hose between the injector fittings you drilled out and manifold fittings?

5mm

[storm]

14.5 - 15.0

Ok it was leaning out.

it runs fine below 30-50% TPS. But when I slowly increase the throttle

Is this slowly increasing free reving or slowly increasing under load?

see this log:
Valtek 30 BFC drilled to 3mm - max lean aboven 30pTPS.png

Spiking!!! before you do anything else pull your plugs and check them. If they are ok refit them but if they look dodgy at all replace them.

5mm

Ok, so that's not a restriction.

EDIT: I just looked at the screenshot again. It's difficult to identify the labels for each line colour but it looks to me like you have a spark misfire. If this is correct it will create the lean condition you are experiencing.

[kikkegek]

14.5 and 15 is rich...remember LPG is 15.5 stoich....16 and beyond is leaner....below 15.5 is richer

plugs have al been replaced recently and are brand new. like 100km ago.

slowly increasing free revving its fine. Under load is where it will go lean above 30-50% TPS

[storm]

14.5 and 15 is rich...remember LPG is 15.5 stoich....16 and beyond is leaner....below 15.5 is richer

Not at WOT it isn't. WOT needs approx 0.90 Lambda which is about 14 AFR.

slowly increasing free revving its fine. Under load is where it will go lean above 30-50% TPS

Edited my post above, I think you have a spark misfire. If it free revs fine but does this under load you are probably loosing spark.

[kikkegek]

from all I have read that is not quit true. LPG is a gaseous fuel and has no benefit for rich mixtures under WOT.
liquid fuels like gasoline will get a cooling benefit from running rich mixtures, while with gaseous fuels anything more then stooich just adds heat and not power.

source:
check out 5th rcomment from the topfrom Michael_au
https://www.hpacademy.com/forum/general ... ion-tuning

as for the spark. I find that hard to believe, but Ill check it. I have swapped to LS D585 truck coils and run them at a very safe 30ms dwell time. these coils are considered indestructible. and wouldnt dropping spark cause pisrich mixtures from unburned fuels in stead of these lean spikes?

[storm]

from all I have read that is not quit true. LPG is a gaseous fuel and has no benefit for rich mixtures under WOT.
liquid fuels like gasoline will get a cooling benefit from running rich mixtures, while with gaseous fuels anything more then stooich just adds heat and not power.

source:
check out 5th rcomment from the topfrom Michael_au
https://www.hpacademy.com/forum/general ... ion-tuning

Lol mate thanks for quoting me, did you see this part?

I, personally, wouldn't go lower than 0.92 - 0.90 (lambda) on a naturally aspirated engine unless dataloging was able to verify if any increase in richness is actually benefiting the engines output.

as for the spark. I find that hard to believe, but Ill check it. I have swapped to LS D585 truck coils and run them at a very safe 30ms dwell time. these coils are considered indestructible. and wouldnt dropping spark cause pisrich mixtures from unburned fuels in stead of these lean spikes?

O2 sensors "read" combusted fuel and create a voltage output that tells the ECU what the mixture is based on the combusted fuel. If the fuel is not combusted, and this is what I think is happening in your case, the molecular structure of the fuel hasn't changed so the O2 sensor is not "reading" actual combusted fuel but rather is "reading" air/fuel mix of which 90% is oxygen.

[storm]

Looking at the screenshot of your datalog I see an event in graph 1 that appears to preceed (albeit momentarily) corresponding events in the other graphs.

Graph 1 the yellow line drops dramatically momentarily before the lean spike in graph 5. You also have a rise in MAP (red line in graph 1) at the same time as the yellow line drops.
Graph 2 the rpm drops at the same point.
Graph 3 green line increases (is that gas pressure?).
Graph 4 white line (pwm?) and red line (duty cycle) both have momentary increases and then drop dramatically.
Graph 5 as mentioned above shows the lean spike.

So we know the engine runs fine free revving, this only happens under load. If I am reading the screenshot correctly all your vital signs are good except for spark which I think is the yellow line in graph 1. After spark drops out the other vital signs react. If I have read the screenshot incorrectly I'll blame my old eyes, I am waiting for my new glasses to arrive next week.

[kikkegek]

we seem to meet everywhere ...doesnt help to meet you under different aliasses

but yeah, that was very valueable indeed. And youre welcome for qouting

as for the ignition. here is my ignition table. As you can see above 80 kPa MAP the timing drops from 34 to 29. Never had problems in that area. But then again, I never drive like this, slowly increasing the throttle to WOT...I usyally either drive easy like in the 10-20% TPS range or stamp it and make the transmission kickdown and drive at 80-100% TPS. hahaha

So I guess Im pulling my plugs and see what they look like. I had ACDELCO #2 (rapidfire single platinum) for while I bought from a friend that ordered them for a big block. Never had problems, untill lately the #1 started fouling and I found out #2 is cold as ice hahaha...then bought a set of stock temp R45TS (stock premium replacement).

[kikkegek]

Looking at the screenshot of your datalog I see an event in graph 1 that appears to preceed (albeit momentarily) corresponding events in the other graphs.

Graph 1 the yellow line drops dramatically momentarily before the lean spike in graph 5. You also have a rise in MAP (red line in graph 1) at the same time as the yellow line drops.

correct. see timing table in previous post

Graph 2 the rpm drops at the same point.

yes, probably from the drop in timing

Graph 3 green line increases (is that gas pressure?).

yes thats (railpressure - MAP) = LPG injection pressure....some LPG injection suppliers call it Psys in their tuning-software

Graph 4 white line (pwm?) and red line (duty cycle) both have momentary increases and then drop dramatically.

correct pw and duty and they increase because MAP increases

Graph 5 as mentioned above shows the lean spike.

So we know the engine runs fine free revving, this only happens under load. If I am reading the screenshot correctly all your vital signs are good except for spark which I think is the yellow line in graph 1. After spark drops out the other vital signs react. If I have read the screenshot incorrectly I'll blame my old eyes, I am waiting for my new glasses to arrive next week.

[storm]

we seem to meet everywhere ...doesnt help to meet you under different aliasses

lolololol. I've been a member of HPA for years, started out as Storm but someone asked me to use my real name so I changed it to Michael AU.

If your plugs are ok check the rest of your ignition system.

[kikkegek]

checked the plugs on the side where my wideband reads. They look fine.

Whats else in the ignition system should I look for?