What pressure should a Single point vapouriser/reducer be set to?

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Re: What pressure should a Single point vapouriser/reducer be set to?

#21 Post by LPGC » Tue Feb 18, 2020 11:10 am

Can expect to maybe have to use a different mixer and/or reducer sensitivity settings between running LPG and running CNG.. They have different stochiometric ratios (CNG needs more air to burn same weight of fuel properly), this would mean that for same reducer sensitivity the mixer should make less signal for CNG. But offsetting this, if reducers in both cases output gas at atmospheric pressure the gas outputted by the CNG reducer would have less mass per volume because CNG is lighter than LPG (for volume at certain pressure), we know LPG will sink whereas CNG will rise is air. It gets more complicated still when reducer and signal response are factored in, would say though that you've been going down the right lines but shouldn't have to use 2 x mixers / Blos's, kind of implies reducer sensitivity needs increasing.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#22 Post by CNG » Tue Feb 18, 2020 8:01 pm

Well here it is... still not sure why this abortion runs better than it ever did? There's two reducers in there at the mo' as well?
First no better than second, but still in situ. Seems 2 x BLOS helps a lot. Used to run lean no matter what, now rich. But we're getting there. Reckon LPGC has it wrt 'stoich'. Reducer now wound fully in to get nearer to stoich, but still too rich. Whereas 1 x BLOS or any mixer - too lean no matter how I set sensitivity.

Power-valves go in next.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#23 Post by LPGC » Tue Feb 18, 2020 8:46 pm

Started out with one reducer which wasn't proven to work properly since you rebuilt it... now there's an additional reducer fitted - what's the story with that reducer?

Don't know if there are any parallels with R89's but R90's went through a period where signal sensitivity was lower than older 'legendary' spec units. My usual go-to mixer system reducer switched from being the R90 to a Romano unit during that period because I found the Romano a lot more consistent and predictable (unit to unit) than R90s then.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#24 Post by Gilbertd » Tue Feb 18, 2020 10:02 pm

I'll second that. The original R90E with the 10mm and 8mm adjusters was dead easy to set up, the later ones with two 6mm adjusters can be a real pig, the slightest touch on the adjuster had the mixture swinging back and forth. The weren't available when I needed to replace mine so have the BRC AT90E in there now, that needed no stetting up at all, worked perfectly straight out of the box.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#25 Post by CNG » Tue Feb 18, 2020 11:25 pm

Thanks for your thoughts gents... You both point at the OMVL? I shall looksee.

Best I recap, and clarify where I've got to, I will admit logic went long since. Reduced to changing parts at random.

1) Initial install was a BLOS (Increased Flow D Needle) with Tomasetto AT04 140HP Reducer. It would run weak, no amount of messing with Tomasetto AT04 140HP would make it run richer. 19-20AFR. Stoich fro CNG is 17.7. Changed BLOS needle for richer. Slit A: much increased flow. No difference, BLOS still required the needle near dropping out of BLOS body to run.

BLOS needles are:
Slit E: normal flow
Slit D: increased flow
Slit A: much increased flow
Slit P: weak flow

Suspected Tomasetto AT04 140HP, thus swapped this for Tomasetto AT04 Super 185HP Version. BLOS still required the needle near dropping out of BLOS body to run. No improvement

2) Did a smoke-test. Found minor leaks on SU carb throttle-shaft and float-bowl vent. Sorted. Yet no real improvement in AFR.

3) Suspected issues with Tomasetto AT04 reducers. OMVL 90e have a good reputation. Now hard to find, yet found 'New Old stock' 2 x OMVL 89e reducers. (CNG version of 90E). No change... BLOS still required the needle near dropping out of BLOS body to run. Suspected both OMVL 89e being 'New Old stock' that the membranes might be 'past-it'. Inspected these, and they looked fine. Changed them anyway. Have two OMVL, tried two. Still ran weak. O2 gauge AFR 19-20ish AFR. No change.

4) Thought I had a timing issue. Guessing now... Advance on CNG is reputed to be 15Degs up on liquid. This engine seemed to run on the maddest advance, so ‘cooking’ it still refuses to pink. No change to AFR no matter what I did. Stock is 38 Degs advance at 4200rpm. I had 56 degrees advance and STILL it would run. No pinking. But weak 19-20ish AFR.
I run a 123 ignitions system and can flick curve to curve on the button. 12V feed changes curves 'on-the-fly'
123.png
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.

See piccy. Mad curves made no change. Whatever the curve, some better than others, but all ran weak. 19-20ish AFR.

5) Suspected the BLOS. Swapped the BLOS. No change. 19-20ish AFR.

6) Came on this forum. Followed suggestion to remove BLOS. Tried a cooker-ring in the inlet 70mm. No change. Ran weak. Tried a cooker ring sited on the SU carb, (see it still there in piccy).
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No change. Ran weak. 1 x BLOS was better than either type of cooker-ring.

7) Messed about with lever height in OMVL 89e. Hoping to get more 'sensitivity' adjustment. Failed. No change in AFR. Thought I’d put the Tomasetto AT04 Super 185HP back in to supply - as a wild guess. No change. Thought it was a bit too large at 185HP but I was losing the will… we've now had four, yes four reducers on this thing. That's 1 x AT04 140HP, 1 x AT04 185HP, and 2 x OMVL 89e.

8) Thought, to hell with it. ."It likes the BLOS, I've got two, give it two" So I did. Damn me, first time ever, it runs RICH! Not weak??? 14-16AFR. And Stoich at idle. GREAT.

9 ) Got some weaker (Normal Flow) needles placed in both BLOS, now runs slightly weaker 15-16AFR but still not stoic under load. Tomasetto AT04 Super 185HP adjustments screwed ‘fully’ home. Both BLOS set as weak as adjustment and needles with allow. Needles screwed fully 'home'. 'Rich', still not stoic under load.

Runs better than it’s ever done before, but a little rich. I’ve never seen ‘Rich’ before. I must have have done something right, but I’m not sure what? Or why? Suction?

I’ve no power-valves in the vapour-feeds to each BLOS. And I'm running on the AT04 185HP. Hope power-valves will cure 'rich-under-load' issue. Matched power-valves on order. Set to try these next. If this fails, set to swap back to OMVL. OMVL may give control for a weaker supply under load.

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Re: What pressure should a Single point vapouriser/reducer be set to?

#26 Post by Gilbertd » Wed Feb 19, 2020 1:14 am

Just a couple of thoughts. On your pic it looks like the mixer is fitted before the carb and not between the carb and inlet manifold where it would normally be fitted. Secondly, you've got a K&N style air filter on there and it is well known that a mixer will not work with a K&N type filter as there is too little restriction so the manifold vacuum is greatly reduced.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#27 Post by CNG » Wed Feb 19, 2020 1:40 am

Ah... thank you.
it is well known that a mixer will not work with a K&N type filter
I'm sure it is, sadly not to me. Have I done all that, and for nothing? Seems maybe I have - this is a suction-issue. For my set-up anyway.

If you're right, and I suspect you are, I'm left confused. I had two cooker-ring type mixers because I've run this engine in the past with LPG. Placed as shown. Also with a 70mm cooker-ring in the inlet tract. Both with a K&N, and before the SU. The 'triangle' SU type cooker-ring/mixer is definitely designed to sit upsteam of the carb. An HS6 is 'kinda-triangle' in form, upstream. Which is what led me to think a K&N etc would work again. It seems we have it, this set-up won't work for CNG, even if it will for LPG. No enough suction? 2 X BLOS find the suction required, 1 x mixer with a K&N won't.

Which is odd. That first piccy (with the orange-hose, and not my engine-bay) is a recognised route. For LPG anyway.
The clue might be in the name, it does say 'SU HS6 LPG Mixer'. Not sure where this places me, leavign 2 x BLOS in there or restricting the filter a tad?

The irony is, I don't like K&Ns, regard them as a boy-racer/quack-physics bodge over a proper 'mahoosive' decent flowing paper job. Was going to put one on once I had this issue sorted.

Ho hum. Least I'm getting there...
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Re: What pressure should a Single point vapouriser/reducer be set to?

#28 Post by robertXX » Wed Feb 19, 2020 8:16 am

a few thoughts , i ran a k & n on all my venturi engines , with no probs , also if the mixer ring was downstream of the carb , then on full decceleration with the throttle closed and a very high vacuum in the inlet ,wouldn't that pull a huge amounts of gas through the mixer ?

re lean ness...I wonder if there's a gas flow restriction in the cuttoff valves /filter/piping from the tank to the reducer ?

if there is a misfire in the engine that can read as lean on the wide band ,as a long shot is it worth closing up plug gaps to see if it affects things .


apologies if this is all already addressed and i missed it :)


regards
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Re: What pressure should a Single point vapouriser/reducer be set to?

#29 Post by CNG » Wed Feb 19, 2020 9:13 am

Thank you for your thoughts, interesting that you manage K&N. I did too with this same engine on LPG with that very SU mixer. This with a OMVL 90e mind - which is why I went with a OMVL 89e.

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Forgot to say in my 'recap' I had all the solenoids out, and checked each. I've two tanks and a proper analogue pressure-gauge on the reducer, fired each individually. There's no pressure drop on the gauges when running. . I suspected the stopcock too. Clean. Not too many are familiar with CNG - believe me, LPG tanks are toys, aerosol-cans by comparison. Not much stops 200Bar. Now it's running rich, seems to prove this is not rooted in supply to the reducer.

Plugs new and set 0.7mm. It’s a wideband ‘Innovate’ O2 gauge. It was indicating 'daft' lean, AFR 21-22 and dying at WOT. Not now. Suspect it was misfiring too.
Today I fit power-valves to each BLOS. My reasoning… it runs ’stoic’ at idle, rich under load.

I've no adjustment headroom on the Tomasetto AT04, both screws nailed ‘fully home’ Runs worse, and richer still if I open these. Idle goes rich and away from 'stoich'. Will put the OMVL 89e back in, I've hopes of it giving more control.

I'm fully aware, 2 x BLOS is madness. I've going to attempt to strangle the filter a bit to see if I can get it to run 1 x BLOS.

And remove my 'legacy-experiment' with that SU cooker-ring. It won't be helping. One thing we have proved (I think)... for this install, BLOS rules.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#30 Post by robertXX » Wed Feb 19, 2020 9:36 am

i run only gas on my cars , no petrol ,and i wonder what effect it would have on the gas mix to take out the su piston ? ,so the blos got the full suck so to speak...

obviously if you are using petrol that would not be viable as a permanent solution .

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Re: What pressure should a Single point vapouriser/reducer be set to?

#31 Post by CNG » Wed Feb 19, 2020 9:46 am

Thank you! Do you know what? I had thought to do that. But then in muddled confusion trying everything else, forgot about it. For all time, the SU is a glorified throttle-body. Won't take five minutes, and like yours, this is a gas engine. Might lift vacuum that tiny bit.

If it works, for the odd occasion I run the liquid, it's 3-4 x screws, and 3-4 minutes. Thank you again.
It also occurs to me, the reason 2 x BLOS works is the second BLOS provides sliding variable-vacuum to the first. If I take the vapour hose off the second, I wonder...

I kill a chicken over my socket-set.
Can't hurt. Might help.

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Re: What pressure should a Single point vapouriser/reducer be set to?

#32 Post by robertXX » Wed Feb 19, 2020 10:56 am

"I kill a chicken over my socket-set."


small maroon glove eating tapioca .


see , i can do too ! ;)

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Re: What pressure should a Single point vapouriser/reducer be set to?

#33 Post by LPGC » Wed Feb 19, 2020 12:30 pm

Can use a free flowing straight through type air filter like K&N, only difference is it can lead to a bit less signal around idle loads, so sensitivity might need to be higher than if a box type filter is used.

Checking plug gaps and ignition is a good idea.

Is the wide band mixture gauge calibrated for CNG or for petrol? If it's calibrated for petrol then a chemically correct mixture will still read as 14.7:1 on CNG even though correct mixture for CNG is the higher AFR.

Wouldn't fit any type of venturi effect fuel introduction device such as a gas mixer or petrol carb where it's exposed to engine vacuum or it will dump loads of fuel into the vacuum.. Normally you'd have airflow coming through the air filter, inlet ducting, gas mixer, petrol carb, throttle body, plenum, individual cylinder inlet runners.. so the carb and mixer are not on the vacuum side of the throttle body. A lot of designs (Holly type setups) have a separate throttle body and carb but it'd still be normal to have airflow through the mixer before the carb before the tb. Going back to the point about K&N's making mixer systems need more sensitivity, I think it's partly because the free flowing filters don't cause micro vacuum in the ducting (like a more restrictive filter would, the micro vacuum would cause the gas to be sucked from the gas port in the venturi not only due to the venturi effect but also the real micro vacuum caused by the filter flow restriction) and partly because airflow is more turbulent when it comes from a shorter straight section between a filter and venturi... often see a bit of the latter effect in terms of lower MAF readings (so higher idle fuel trims) with a free flow air filter and shorter induction pipe compared to a standard filter and longer ducting setup on fuel injected cars.

Thought has occurred to me too that the 1st Blos piston will be causing extra vacuum so the 2nd Blos will suck more gas than it otherwise would.

Still I think at this point I'd be wanting to confirm the problem wasn't the reducer(s), I'd try a known good reducer even if it was an LPG rather than CNG reducer.

What happens to mixture if you remove the K&N and partially block off the inlet using a hand (or something else in case of a backfire lol).
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Re: What pressure should a Single point vapouriser/reducer be set to?

#34 Post by CNG » Wed Feb 19, 2020 2:56 pm

Thanks LPGC. For the moment I'm going to plod on with getting it to work with 2 x BLOS, simply because I think I'm nearly there. Once I have that, I'm going to work out why I need them. I think one creates more vacuum. Not sure why cooker-rings don't work at all.

O2 gauge is definitely calibrated for CNG. Gauge has a CNG calibration and scale. Spent ages getting Innovation Tech. support to run thru' it. Seems despite the gauge having this function, their own tech support were hazy on it. When indicating AFR 17.7 the thing even runs sweeter. 'Free-air' calibrated - I know it's right. The fact that when the gauge reads stoic, it runs best, confirms this to me.

i don't think this is an ignition issue, seems to run on any setting. I've got a curve in there 14 degrees advanced on the stock 'petrol datum'. Which won't be far out.

Will play some more and report back. Will be strangling the inlet a tad too.

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Re: What pressure should a Single point vapouriser/reducer be set to?

#35 Post by CNG » Thu Feb 20, 2020 8:32 pm

OK, progress. One point, earleir I gave stoich as 17.7. Incorrect, 17.2. Didn't get as much done as I'd like but now it runs, and for what it is, pretty sweet too.
After some confusion and mis-picks at TinleyTech, managed to source weaker needles for BLOS x 2. Made little difference, but worth a go. Not sure they were any weaker, but Tinley good about this, sent some more. Under a vernier, these were different again. We did our best.

1) Swapped the reducer from the in-situ Tomasetti to the previously used OMVL 89e. As expected little change, still too rich. With four reducers of various flavours, I really can't see this as a reducer problem. OMVL adjustment now wound fully home, just as Tomasetti reducer was, gives rich running. Whereas with 1 x BLOS and sensitivity screws falling-out of both of these reducers, this fails to give anything but weak running.

2) As with Tomasetti, OMVL reducer now idles to stoich. Under load AFR rich. OMVL has two vapour ports, running with both, one to each BLOS. As expected made things richer still. Not by much. This allowed me to try 2 x power-valves, one per BLOS. After a test drive and a tweak, I've a wagon that runs to stoic on WOT. Wound in 2/3 turns, the 2 x power-valves did their work. See piccy. I'm happy. Very happy. It's needed on the road. This vehicle might be a 'classic' but yours truly fails in the faker-with-facial-hair department. It's a 'daily' and gets driven. This vehicle gets as much use in Feb as August, never sees a showground, and never will.

This 'thing' is not fast, but it was getting slower and slower. Something had to be done. The principal concern was to get what grunt it has, back. Now, 'why' this mess works better than it ever did, I'm still not sure. Ran out of time today. Getting to the bottom of that question comes next. My money sits on lack of suction, and the vacuum leaks making it ever slower. Don't reckon the crankcase-breather pipe missing on the back of the K&N helps. I want to try the 'missing piston' and 'strangling' suggestions. To be continued...
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Re: What pressure should a Single point vapouriser/reducer be set to?

#36 Post by LPGC » Fri Feb 21, 2020 1:40 pm

Probably a lesson in sucking eggs! All air that enters the manifold must come through the mixer/Blos or it will run lean, including any air that enters the manifold from a crankcase breather. If there's a crankcase breather to the manifold and the engine case has any air leaks (oil filler, dipstick, cam covers, etc) it can cause lean running.
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Re: What pressure should a Single point vapouriser/reducer be set to?

#37 Post by CNG » Fri Feb 21, 2020 3:49 pm

I did a 'smoke-test' on the inlet-tract and found minor leaks. Now sorted, I've not tested the c/case. Goes on my list. Next outing in the order that comes easiest will:

a) Try running with SU piston removed
b) 1 x BLOS - choking off inlet
c) Filter >> 1 x BLOS >> 70mm mixer >> SU >> Manifold
d) Filter >> 70mm mixer >> 1 x BLOS >> SU >> Manifold
e) A long length of hose between Filter and 1 x BLOS
f) 1 x BLOS + full paper-filter airbox - removing K&N.
g) Gouging lumps out of a spare BLOS needle. Might be all it needs?
h) Smoke-test the lot.

Then I want to put in a clsoed loop, AEB Leonardo/Galileo w/stepper to feed the BLOS.

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Re: What pressure should a Single point vapouriser/reducer be set to?

#38 Post by Brian_H » Fri Feb 21, 2020 8:14 pm

CNG - I notice you seem to crop up in the logs a lot getting posts blocked, if it happens again can you drop me a pm with what it is saying the problem is with the post?

Cheers

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Re: What pressure should a Single point vapouriser/reducer be set to?

#39 Post by CNG » Mon Feb 24, 2020 12:16 pm

Had a spare half hour so removed the SU cooker-ring type mixer. Now by 'leaf-sprung' Land rover standards, this 'thing' is rocket-ship-fast. It's been breathed-on a lot. Has a hot-head/cam etc. However be clear, by any other measure, it's slow. Driving old Land rovers is a little like riding a bike; Hills that you won't see in a car, you can't fail to feel on a bike. It's like that. You find yourself looking for all the power you can muster.

The cooker-ring experiments failed miserably. Still in situ, and not doing much after my experiments with cooker-rings I took out the SU jobby. I had it WOT would be restricted, but now it's off I can't say I see any difference. Nope, none whatsoever. I'm surprised.

However I do know this engine likes BLOS. I think one BLOS aids suction for the other. Next I'm going to take out one of the BLOS and put in that 70mm mixer seen in the pic. If the assumption is correct, 1 x BLOS will aid that 70mm mixer, and/or, the mixer aids the BLOS...

This 70mm mixer used to to run this engine on LPG. I think - as Simon suggests, this is an AFR issue with CNG.

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Re: What pressure should a Single point vapouriser/reducer be set to?

#40 Post by CNG » Tue Feb 25, 2020 9:02 am

To quote LPGC
CNG needs more volume of gas in relation to volume of air flowing through the mixer than LPG does despite CNG having the higher AFR - a small difference in correct AFR between LPG and CNG but a large difference in mass per volume at a given pressure and temperature of LPG and CNG. A helium balloon has higher pressure than atmosphere but has less mass per volume (density) than atmosphere
I think we have it. Those mixers ran LPG, which because of relative AFR/fuel density means they might not be up to the job. We'll soon see.

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