lpg feed pipe size on 500 bhp engine.

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robertXX
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Re: lpg feed pipe size on 500 bhp engine.

#321 Post by robertXX » Tue Jul 02, 2019 9:51 pm

ok ...quick question ,

im getting much higher pw on the front engine with the brc orange normal old type injectors , are they calibrated with different sized nozzles at the injector block ,or at the inlet manifold connection ? i am wondering if i should/can put bigger nozzles on the injectors. .


merci
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Re: lpg feed pipe size on 500 bhp engine.

#322 Post by LPGC » Wed Jul 03, 2019 10:27 am

At the injector block end, it doesn't work the other way around - If you put a smaller restriction than injector nozzles at the manifold end the engine still gets the same amount of gas that injector nozzles flow at low engine loads and/or low rpm but starts to restrict gas flow at higher engine loads/higher rpm, i.e. it serves as a bottleneck rather than the accurate metering device that you need.

Orange injectors should be good for the Jag engines. You're running group injection so the injectors have to pulse every rpm instead of every 2nd rpm as is the case with sequential injection, so injector latency will have twice the effect that it has on sequential engines which will be reflected in pw... The Keihin have less latency and would expect them to need lower pw at idle.

But still you shouldn't need 8ms pw on either type injector for idle. Normally a sequential petrol injection system on engines of this type will have pw of between 3ms and 4ms for idle with warm engine, a group petrol injection system on an engine of this type might have 2 to 3ms pw. The pw for gas injectors would be those figures plus injector latency/dead time, which we said in earlier posts was about 1ms (taking into account closing time).

Also got to remember that if mixture isn't right the engine will run less efficiently, so usually need more fuel, so lead to higher pw than necessary.
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Re: lpg feed pipe size on 500 bhp engine.

#323 Post by robertXX » Wed Jul 03, 2019 10:53 am

Thank you simon ,

i just didn't know , or notice when i put it all together , whether the pipe stubs on the orange injectors were a calibrated size you select or if they are all the same size and you calibrate at the manifold . on my engines the manifold stubs are all the same size at 3.5mm i think it was .

i did have a look for brc injector stubs to see if there was a load of different diameters , but couldn't find any so assumed those injectors simply come with a set size and yo calibrate at the port like normal .



my first bit of mapping readings for afr and pw are ..

engine 1 afr..


Image


engine 2 afr ..

Image


engine 1 pw

Image



engine 2 pw..

Image




that was a quick 30m on the dyno , also i am at 15 psi gas pressure , so today i will raise that on E1. on independant throttle bodies you get a big jump from 95% map to 100% as you can see.


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Re: lpg feed pipe size on 500 bhp engine.

#324 Post by LPGC » Wed Jul 03, 2019 3:01 pm

Looks good! Few points though in trying to be helpful..

Is 0.5 map supposedly the same as 0.5 bar manifold pressure? And, if so, are there no figures below 0.55 because of some aspect related to the vac signal from your individual throttle bodies, or because the engines really done't draw that much vacuum, or because you just haven't mapped that part yet, or because the engines were cold so tight? Would guess it's looking like a vac signal thing judging by afr at idle is good but map signal is at 75% around idle - If that's the case we hope driveability at low rpms is good because it'll mean control over fuelling at low rpms isn't ideal having only a few boxes between no load and full load.

Pulse width - The high load figures would be OK for a sequential injection setup but group injection needs to pulse twice as often so there's only half the available pw window with group injection. With those pw's you may run out of window at higher rpms. E.g. window at 6000 rpm for group injection is only 10ms, and though the engine probably won't stay on cam to 6000rpm might still expect pw to need to be above available window at high rpms particularly if you'll be dialling in high load enrichment. But I noted you're going to up the pressure and that should help.
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Re: lpg feed pipe size on 500 bhp engine.

#325 Post by robertXX » Thu Jul 04, 2019 9:33 am

Appreciate the input simon ,:)

the map , yes that's .5 bar , its a tendency of independent throttles to have a low vacuum at idle . i have a bit more ignition advance to add ,so vac will come up a bit ...however... i now find there is a megasquirt mode called ,appropriately ,itb mode ...which mixes throttle position and map to create a hybrid scale .this means you use the whole map , and i can also adjust the % of map versus throttle position .


so i decided to use this mode , and instantly had the whole map working ,also with the higher gas pressure , now 24 psi on E1 and 20 psi on E2.. i have pw in the 5 to 6 range at tickover ,so getting there .

It was noticeable that the map was way too lean now . since i was operating in the lower parts of the map more ,where it had not been adjusted , so it would rev but any full throttle had it falling flat on its face ,i made a few manual adjustment and had another try , and it revved very well , and just as a test i gave it full throttle up to 2800 on a load ,and pulled over 200 bhp 375 lbs ft ,and it climbed right up the front roller on the dyno , so making progress .

speed density map where it would not rev when changed to ITB mode.....

Image


a Very rough map that would rev brilliantly..

Image

you can also see how i have changed the vertical scaling to cater to the thrttle % at low rpm.


i hope to take it for a drive today ,with it set on auto tune , and go to a car show in witney .



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Re: lpg feed pipe size on 500 bhp engine.

#326 Post by LPGC » Thu Jul 04, 2019 9:44 am

Great stuff Rob!

Know what you mean about not getting much vacuum at low rpm with individual tb's and think I mentioned earlier in thread I thought this could be a problem for calibration 'resolution' (for want of a better term) especially at low rpms.

I nearly asked in my last post if there was a 'mixed mode' that used TPS for low rpm and Map for higher rpms but now you've said there is I'm curious to know more about how that's implemented... Is there a hard rpm switchover point or some sort of sliding transition between using Tps and Map ?

I can imagine such sliding transition to be implemented something like: a table for Tps, a table for Map (which you had originally anyway), an additional table holding proportional values for how much notice to take of Tps versus rpm, the final fuelling pw then calculated as (Tps x Tps proportion) + (Map x Map proportion). Then you might set all boxes in the additional table to 100% TPS and calibrate for TPS in full, set all boxes in the additional table to 100% map and calibrate fully for map, then set the proportional values. But I doubt this is how it works in practice? And in practice it might not be feasible due to 'resolution' to set all boxes in both maps (especially the manifold pressure map) accurately anyway.
Last edited by LPGC on Thu Jul 04, 2019 10:06 am, edited 1 time in total.
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Re: lpg feed pipe size on 500 bhp engine.

#327 Post by robertXX » Thu Jul 04, 2019 9:50 am

Image


you have thee two maps to set it with Simon .

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Re: lpg feed pipe size on 500 bhp engine.

#328 Post by LPGC » Thu Jul 04, 2019 10:09 am

I edited my last post and asked a few questions, the edit crossed with your last post.. But your last post answers most of my questions, I can see the TPS% which is kind of what I expected. Thanks Rob.
Or to address you in full... Mr Robert Burnett (according to the TunerStudio registration). Or is it Professor Burnett, or Batman lol ;-)
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Re: lpg feed pipe size on 500 bhp engine.

#329 Post by robertXX » Sat Jul 06, 2019 8:58 pm

haha i think i am just known around here as that crazy inventor bloke .

an interesting problem i now find is ,


Went for a mile on the rd to see if i thought it would make it to the local car show 6 miles way , and it felt good , so set off in the evening after supper to drive the 6 miles ,fill up the tank ,and pop into the show .


this all went well ...


Image



and of course on the exit it had to accidentally break traction in 1st and 2nd , and ,later on , accidentally punching the throttle broke the tyres free at 60 in 3rd ...its definitely a lot more pokey ,,and very smooth ,not perfect , there are lean bits and rich bits ,but happy i made the change and hopefully less fuel used .


one anomaly i found this morning is ,

here is my timing map ..

Image



and here is the timing i logged ..



Image



Image



so that is very bad on a 11.6:1 compression ratio .



research continues ,,maybe a ITB mode glitch , but more likely me doing something stupid with the setup ...


EDIT : i think what is happening is , the map for the ign is written for a MAP signal , and it's using mostly throttle position ,so i can be at 100% MAP ,and the throttle is only at 35 % so its giving me timing on the 35% line . i am going to try running the ITB mode on the fueleing ,and the Speed density mode on the ignition ...


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Re: lpg feed pipe size on 500 bhp engine.

#330 Post by robertXX » Tue Aug 06, 2019 2:15 pm

well would you believe it, one of the brc injectors is leaking a good un at anything ovr 5psi , its going full open .

Now, a new injector is 70 quid , or i could go with the omvl's at a much lower price and get 6 of those .

the question is , if one brc in the row of 6 has gone wrong ,is this an age thing and are the others going to do the same ? i am guessing the pintle spring has fractured .

it looks like they are swaged to seal after construction so not serviceable.

poxy pox !

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Re: lpg feed pipe size on 500 bhp engine.

#331 Post by robertXX » Wed Aug 07, 2019 9:28 am

hmm , well a bit of experimentation has ocurred .

connected the compressor up to the injector , and tried various pressures and clicked it open an closed with a 12v battery (watching for hot coil).

result was that it would leak then the leak would gradually reduce to nothing . if i then opened and closed the inj, it would stay sealed up to any pressure all the way to 50 psi.

let the gas feed off , then repressurise and it's leaking again, for less time, then seals itself again ,and will hold any pressure .

so i imagine its gummed up in the spring area . popped it in some inj cleaner last night ,and today with get some carb cleaner and wd40 and see if drenching it with those will help.

i dont want to lash out on another brc if they all start to go wonky , it would be way cheaper just to get 6 omvl's new .

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Re: lpg feed pipe size on 500 bhp engine.

#332 Post by LPGC » Wed Aug 07, 2019 10:35 am

Possibly an age/use thing, do we know how old the BRC injectors are? Or a lube thing (if the injectors were previously used with a through injector type lube), or just bad luck. Yeh not serviceable and not something any cleaning fluid will fix.

OMVL's beat a lot of more expensive injectors on performance but in your position even with OMVL's on shelf I'd consider buying a set of MJ's, especially since the very recent price drop of the older style bigger MJ's. Can now buy singular older type MJ's for around £10 each but with the single injectors you obviously need a 6 way feed (splitter manifold or splitter filter).
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Re: lpg feed pipe size on 500 bhp engine.

#333 Post by robertXX » Wed Aug 07, 2019 11:38 am

thank you simon !

i cannot find the MJ's that cheap ......may i have a link ?


aha , did you mean these pre vat ..?


https://www.lpgshop.co.uk/magic-jet-sin ... cng-spare/

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Re: lpg feed pipe size on 500 bhp engine.

#334 Post by LPGC » Wed Aug 07, 2019 12:58 pm

No probs Rob. Yes I did, and you could have the single injectors mounted directly in position on the vac side of each individual throttle body with pipe lengths between injectors and gas entry points only about an inch long, also drill the injector nozzles out to whatever size you want (can't do that with OMVL SL's)
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Re: lpg feed pipe size on 500 bhp engine.

#336 Post by robertXX » Tue Aug 13, 2019 9:07 pm

okay dokay !


new magic jet injectors fitted ,and i smugly try to start car ....


er that will be a no chance on the front engine then ,and gas pressure is at 34 psi not 24 where it should be .

i have removed the jets from the new inj and am using the 3.75 mm stub in the inlets as my orifice , so i thought maybe these inj are flowing a lot more than the old brc's did ,and

a) flooding the engine ,and

b)flowing so much the reducer gets frozen before the water can warm it up .



so tomorrow i try dropping reducer pressure to 15 psi , see what that does , then try dropping pulse width if the reducer does not freeze up gain .


oh fun .

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Re: lpg feed pipe size on 500 bhp engine.

#337 Post by LPGC » Tue Aug 13, 2019 9:28 pm

You'll need to drill the injector nozzles (jets) to 2.5mm and refit them, you can't meter the gas at the manifold end it has to be done at the injector end. If you try to meter gas at the manifold end the injector still pulses out the same amount of gas almost regardless of what restriction you put at the manifold end (increasingly so with diminishing pulse length and diminishing rpm), just that the gas then takes longer to flow from the pipe between injector and manifold into the manifold... you just end up with the inlet port getting the same dose of gas but just in a longer less intense 'squirt' (the flow takes longer). The fittings in the manifold are usually best as wide diameter as possible, they should certainly be wider than the nozzles on the injectors.

I've got drilling MJ nozzles down to a T... I hold the removed nozzle by the thick end but with the narrow end facing me very securely in the curved grip section of pliers and aim the drill at the narrow end in line with the nozzle like aiming a shotgun. Make sure you use a sharp drill bit, I even prefer it when the drill bit grips into the brass... you've got to be holding them very securely in pliers especially if the bit grips into the brass! After drilling through from the narrow end of the jet first I turn the nozzle around and drill through again starting at the wide (exit) end of the nozzle, then I moved the jet up and down the moving drill bit and spend a bit of time on the smooth shank section of the bit to kind of polish the inside of the jet. I do this when drilling them to 3mm, it's much easier drilling them to 2.5mm. I keep a set of preferred make/brand bits around especially for drilling jets, over time they pick up an outer layer of brass which seems to help. It's OK to drill holes slightly off-centre as long as they don't go through the side of the threads on the jet (ideally of course you want to drill straight through the centre - when the bit bites/grips into the brass it tends to be when they're following the centre a bit better). I have about a 97% success rate of drilling 3mm holes in MJ nozzles, this would be very close to 100% if I drilled them to 2.5mm first but that takes more time. I keep a lot spare MJ nozzles around, probably wouldn't need any spares or just a couple a year if just drilling to 2.5mm. I drill so many nozzles that if I have a spare few hours I'll spend it drilling nozzles and doing other prep work to save time for upcoming conversions.

Slightly different subject - MJ injectors will flow a hell of a lot of gas without nozzles. 2.5mm nozzles should be enough with the pressure you're using, without nozzles the MJ's will low something like the equivalent of 4mm nozzles which is about 2.5 times as much as a 2.5mm nozzle will flow (just the old pi r squared).
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Re: lpg feed pipe size on 500 bhp engine.

#338 Post by robertXX » Wed Aug 14, 2019 4:37 am

This for 40 bhp / cyl and 15 psi gas pressure Simon ? Yes j am used to drilling brass jets for webbers and dellorto' s when setting I carbs in the dyno. Oh that takes me back. 🤓

I had assumed the 3. 75 mm orifice in the inlets stubs would act like a calibrated nozzle like I used with the valtec 30 s. In the Astra. On medusa with engine no 2 and the matrix injectors this is what appears to be working ok ? The matrix are firing thier Gas into the same 3.75 mm stubs and seem mappable, maybe the matrix ones have a degree of restriction at the inj outlet.


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Re: lpg feed pipe size on 500 bhp engine.

#339 Post by LPGC » Wed Aug 14, 2019 12:51 pm

Sorry for the sucking eggs recap on drilling nozzles!

Most Valtek 30's have internals that will only flow as much as a 2.5 nozzle, so even if you fit bigger nozzles they'll only flow as they would with 2.5 nozzles anyway. The 3.75 manifold nozzles on your Astra won't be doing any metering, the restriction of the injectors themselves will be doing the metering. If you fit 3.75 manifold nozzles on Medusa and don't fit nozzles on the injectors you'll have kind of the reverse situation because the injectors without nozzles will flow as much as maybe 3.75 / 4mm nozzles (too big) and the manifold nozzles may actually be doing some of the metering (bad as explained below).

If you're only running 15psi (1 bar) pressure drill the nozzles to 3mm instead of 2.5mm, I read 24psi above ;-) And fit the jets/nozzles directly on the injectors. Would expect about 17psi (above manifold pressure) to be about right for 3mm nozzles... You have referenced reducer pressure to manifold pressure by connecting the vac pipes(?).

The metering needs to be done at the injectors not at the manifold. Picture the volume between the injector plunger and the jet, the jet is usually fitted directly on the injector so is a very small volume, the very small volume soon gets up to injector feed gas pressure when the injector plunger is open and the jet meters gas from this volume to the vacuum/engine side (of course this volume is replenished anyway while-ever the injector is open. If the jet isn't mounted directly on the injector but is moved closer to the engine we vastly increase that volume, then depending on flow rate of injectors (now without jet/nozzle directly attached) versus flow rate of jet/nozzle that's now further away the now larger volume still very quickly gets up to injector feed gas pressure when the injector opens but when the injector is closed there is still the volume of gas under pressure in the pipe between injector (no nozzle) and nozzle (all the way down the pipe at the manifold end). That volume of gas will still be delivered to the engine regardless of the injector being closed. Another effect of moving the metering jet from injectors to manifold is that the gas will be delivered to the engine in more of a half sine wave flow pattern than a half square wave flow pattern (for want of better terms), this is due to the pressure in the feed pipe building more slowly behind the nozzle due to increased volume between the injector and it's metering jet and falling more slowly as it takes more time for the gas in the volume of the pipe to get through the metering jet at the manifold end.

The effect screws up linearity because (say) a 3ms pulse length may flow more than half of a 6ms pulse length, whereas usually with nozzles mounted directly on injectors a 3ms pulse length will flow less than half of a 6ms pulse length. Screwing up linearity can reach unworkable extents such as for high load you need 14ms but for idle you need 1ms, the injectors would be incapable of accurately metering gas at a 1ms pulse length. Whereas with nozzles directly on injectors in this example you'd still need the same 14ms pulse for high load but probably need a 3ms pulse for idle, well within the capability of the injectors.

Another point about running injectors without nozzles - particularly if they're from different batches you need to make sure they all flow the same without nozzles... can be done if you have loads of them around like me but if you've only bought enough for one vehicle you might not get a good flow match. Nozzles a bit smaller than injector internals are a great equaliser for injector internals manufacturing tolerances, even I only fit injectors without nozzles in very limited circumstances where I need mega flow rates. All makes/models of injector have a sweet spot where performance aspects such as linearity etc peak, this can again be related to the volume between plunger and metering jet, MJs are very happy with 3mm nozzles. An example engine might be set up with 3mm nozzles at say 1.1 bar or 2.5 nozzles at say 1.7 bar and be almost as equally happy in both cases but in such situation with MJs I'd usually opt for 3mm nozzles at 1.1 bar... the higher pressure of 1.7 bar very slightly slows the opening response time compared to 1.1 bar and the volume between plunger and jet has more effect (at rounding off the square of the end of the gas pulse because it takes longer for the gas in the dead volume to flow through it) with 2.5 nozzles than with 3mm nozzles so effectively also increases closing time.

Simon
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Re: lpg feed pipe size on 500 bhp engine.

#340 Post by robertXX » Wed Aug 14, 2019 1:28 pm

coolio thank you for the detailed exp simon ,very useful.


they are all off ,and drilled to 2.9mm drill shank size ,so prob 3mm with drilling clearancing .

this makes me wonder about the matrix ones i have on engine 2 , they are injecting through the 3.75mm stubs on the inlet rubbers , so i assume there was a smaller orifice on the matrix injectors ....i dont remember measuring it because i assumed the rubbers stubs would work , i wonder if dai remembers .


re gas pressure i was using 24 psi , but want to run lower to get more cranking voltage tolerance ,this drops to 9v , so less gas pressure more chnge of inj openning.



regards
robert

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