Drilling out a kei hin injector

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robertXX
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Drilling out a kei hin injector

#1 Post by robertXX » Sun Oct 21, 2018 5:43 pm

Hello chaps !

My cheapo injectors on the astra are starting to not work quite right, and i have a set of green spot kei hins , brand new .now a green spot is a 20 odd bhp per inj size ,with a 2.2mm hole in the body .

this hole size equates to 20bhp ,each , so the question is , what is inside ? is this hole i can see the continuation of the pintle area , so a drill would basically /probably destroy them , or is the pintle area the same on all of them and the 2.2mm section is the metering area some way down from the pintle ?


regards
robert.

EDIT , ok it appears the 2.2mm section is a 2mm long section , which then opens out again before the pintle , so it should be drillable ....

ps , anyone got an old keihin 4 cyl inj rail to mount them on, knocking about ?

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Re: Drilling out a kei hin injector

#2 Post by LPGC » Mon Oct 22, 2018 11:44 pm

I haven't investigated this yet (as I've often intended - by cutting injectors up!) but I think there's more to different flow rate Keihin's than just the nozzle size.

Also haven't investigated if Keihins will mount on Hana rails... I was recently sent 4 Hana bare rails by mistake by a supplier when I'd actually ordered some aluminium 12mm inlet to 4x6mm outlet and 12mm in to 3x6mm out 'gas distribution rails' (little manifolds really), but I have to send them back.

I do have a few Keihin rails but since they have good injectors on them I don't want to split them, might as well keep the injectors on them... sorry!
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robertXX
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Re: Drilling out a kei hin injector

#3 Post by robertXX » Tue Oct 23, 2018 1:44 pm

Thanks simon , i will drill one out and compare flow with an un drilled one , i see a rail on ebay for 25 quid odd so that's an option , also the ecu connector plugs seem odd , ,they might be another 25 quid so i will prob wire with small brass speaker connectors .

robertXX
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Re: Drilling out a kei hin injector

#4 Post by robertXX » Tue Oct 23, 2018 5:02 pm

ok drilled to 3mm , and then puffed down with the compressor , its definately made a big difference , now i just need to decide on the resistors value , since they are 1.9 ohms not 3 ohms like my valteks , i will try a 1 ohm bigger than my valteks have and see if it will still open on 40 psi.

robertXX
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Re: Drilling out a kei hin injector

#5 Post by robertXX » Fri Nov 23, 2018 8:09 pm

orl righty..to wrap this up a bit .

New, drilled out , Keihin injectors fitted , 1 ohm resistors added to the 1.25 ohms .

any difference i hear you ask ..

massive ..

Much smoother , and the ecu holds a much more stable air fuel ratio ,whereas with the valteks it would ,at tickover, be held in a range of 13.80 to 14.50 :1 now its more like just the last digit changing .

Power wise , i had it up to 4k on full boost , and it was fine , i did have to double the rq fuel in the ecu , so they may be ok , or i might have to turn up the gas pressure , set at 15 psi at the mo .

With the resistor packs i have on there , i tested that they will open up to about 50 psi ...so with 13 psi boost that gives me 37 psi gas pressure max, oh that test was on 12v not 13.8v running car volts .


As to the original problem, after 7 odd years i think it is, since they were fitted ,and they were 2nd hand ,it was running really rich when cold , then fairly normal , then it started missing on one cylinder .i took the valtek 30's apart and cleaned them , bit better for a week, then missing again , read up on them ,and found the piston throw can be set , so made a test rig with my dial gauge , and found they were all opening around .9mm , so set them to .5mm as per specs ..this all made no difference .


then look fine , piston seals look good , and i can hear them ticking with the stethoscope ,so all i can assume is the opening and closing is being slowed ,so they hang open to much , and as for the missing cylinder , maybe its being drowned ..or the seals are leaking .no idea really . i did pressure test after i took them off them to to 40 psi ,and no leakage .


regards
robert

robertXX
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Re: Drilling out a kei hin injector

#6 Post by robertXX » Wed Nov 28, 2018 11:00 am

ok dokey , not sure if this is being read by anyone but i will put up latest news ,

had it up to 6500 rpm on max boost yesterday , it went lean at 4500 ,then richened itself up to 12.5 at 6500 , so that looks fine , just a bit of mapping to do .

interestingly ,i had to basically double the map values to get it in the ball park , but then it reduced its low rpm values by 10%, increased mid range about the same, then needed to reduce top end by 10% ,so, no general rule ...

i imagine these inj are far more consistent ,and the valteks were changing their behaviour as they went up the rpm range .

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Re: Drilling out a kei hin injector

#7 Post by Brian_H » Wed Nov 28, 2018 11:15 am

I think from whats been said its the time taken to close and open the injector fully - as in both those states your getting less than the full flow through them, Ideally the shorter time its in either of those states the better, as you have a more consistent amount flowing when its fully open. Equally some injectors may struggle with a higher pressure to open, which might account for your problems with the valtek ones.

The topic has had 250 views so far, so its definitely being seen!

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Re: Drilling out a kei hin injector

#8 Post by LPGC » Thu Nov 29, 2018 6:19 pm

Sorry, I've been meaning to reply here... Just as an acknowledgement really because I don't really have anything to add, it seems you're on the right lines with everything!
But on your most recent post - With some injector response / nozzle / pressure combinations on slave type systems you can find that if there is any need for pulse length adjustment for rpm there will be need for most adjustment around the torque peak rpm of the engine and around moderately low pulse duration (part throttle). The turbo aspect(?) can alter this a bit and highlight other factors such as when manifold pressure gets higher and gas pressure is manifold pressure referenced you don't need pulse duration to be as long (or sometimes nozzles to be as big) as might be expected. On a standalone system the difference for rpm would be more emphasised because on a slave type system the petrol map will already account for the torque peak (edit volumetric efficiency at varying rpms). I can imagine various reasons for the effect but it's probably due to a combination of factors, mostly related to the fact that there's need for the multiplier in the first place down to lesser degree points such as injector plunger bounce. Keihins are usually run at closer to 2 bar than 1 bar, it would be interesting to measure how different pressures and resistors in series affect response of these and other type injectors.
Last edited by LPGC on Fri Nov 30, 2018 10:55 am, edited 1 time in total.
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robertXX
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Re: Drilling out a kei hin injector

#9 Post by robertXX » Thu Nov 29, 2018 8:57 pm

Thanks Brian ,and Simon , i agree , , what i am most curious about though is what happened to my valteks to make them go rich ..they seemed to click and work ,just very very rich .

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Re: Drilling out a kei hin injector

#10 Post by LPGC » Fri Nov 30, 2018 11:07 am

Can often identify worn injectors by them clicking louder or sounding different, I sometimes use a bit of pipe as a stethoscope on them. They can wear on the shafts, get lateral play / grooves which might slow the opening/closing or both. Springs going soft might speed up the opening but slow down the closing. A circle wears into the rubbery plunger end seals where they seat on the gas exit tube. All things combined make the injectors response change slowly over time... a lot of change can occur in the first quarter hour of running them (kind of a bedding in stage), then they seem to have bed in and response changes very slowly over a long time, then as they get nearly worn out the response changes quickly again. Provided the bottom seal remains OK you usually notice most difference in response when pulsing injectors near their minimum pulse duration.

But sometimes when injector response might seem to have changed it hasn't changed, what might have changed instead is gas pressure and/or temperature, then it can be due to how accurately the ECU compensates for pressure / temperature. E.g. Most ECUs over compensate for pressure at low pulse duration... they do the math correctly but don't allow for the fact that higher pressure can slow the opening stage as gas pressure is pushing the plunger shut against the outlet.
Last edited by LPGC on Fri Nov 30, 2018 11:18 am, edited 1 time in total.
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robertXX
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Re: Drilling out a kei hin injector

#11 Post by robertXX » Fri Nov 30, 2018 11:14 am

i think the springs might be it Simon , i will get some pics up .

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