fuel injectors - 3-hole spray pattern vs single

[Anthony P]

looking at racetronix website, for stock 30pph replacement injectors, there are two choices:
a 3-hole spray pattern and
a single hole pattern that's been around for decades.

3-hole, 30pph is Lucas 01D034x link=> 31.2 lb/hr Disc High-Z Fuel Injector (01D034x): Fuel Injectors - High Impedance

single hole 30pph is Lucas D1720xx (old 5207009; 621020 ) link => 32 lb/hr Disc High-Z Fuel Injector (D1720xx): Fuel Injectors - High Impedance

fluid mechanics modeling question: is 3-hole spray pattern is better choice today? this is for a bone stock engine where only mods are injectors, TT chip, fuel pump and fuel pump hot wire kit.

not looking for an answer of "at stock levels, it doesn't matter."

what I don't know is the velocity profile of the air stream thru each runner into the combustion chamber or the flow volume profile. So,

---the 4-degree pencil spray pattern of the single nozzle is preferred because....? OR

---the 3-hole spray pattern yields better atomization, perhaps better fuel economy just cruzin' around and doesn't do much more? it's just a newer injector design that can be used on our engines as well?

perhaps someone who knows could say the single spray pattern keeps the atomized fuel centered in the runner where air flow velocity is highest, albeit turbulent + eddies?

perhaps a 3-hole spray pattern at stock levels (air velocity and volume) is not desired as the angle of the three nozzles actually ends up wetting intake runner walls due to stock low velocity profile + low volume profile?

the 42pph Lucas 01D030x uses a 3-hole spray pattern as does the 66pph and 79pph injector. sure, those fuel volumes are probably best delivered via a 3 nozzle set up for those air volumes and velocities at 80%-plus duty cycle.

Has anyone modeled this to conclude that either one is preferred at stock levels with the corresponding lower velocities and air densities seen on unmodified engines?

Thanks.

 

[dynoman]

I believe that all fuel injectors that GM makes are multi hole injectors including the direct injection ones . I just retired from the GM plant that makes the injectors , rails and truck manifolds . The spray pattern is checked with a camera and must meet certain parameters on very tenth injector built . They build approximately 30,000 injectors per day . On the new injectors they are laser drilling the holes the size of a hair and i believe there are 5 of them on each injector . This is some of the equipment I serviced .

 

[Anthony P]

Thanks Sam. I'm probably looking at this with too large a lens, like nearly 40 years, considering the progression from the OE pintle injectors to the new-fangled "rotary disc" single hole units I referenced above to the updated designs of today using multi-hole designs.

the D1720AA 30pph injectors (single nozzle) installed in the full size die cast (LOL) that occupies a garage bay are from 1995. tested and flow fine. I gave up on the OE pintle injectors. have multiple new sets. even with fuel stabilizers, for me, the OE Bosch *218 pintle injectors would foul under very limited use in today's pump gas over a few years.

Going forward, I'll probably select the newer 3-hole design. Actually thinking of picking up another set plus some spares to have on hand. if one of the 1995 vintage D1720AA's gives me a problem, they'll all come out for a new set.

 

[SCOOBY DOO]

I used the injectors that Eric sells. Worked mint.

 

[Anthony P]

Thanks Scoob. Yes, I had looked around on Eric's redesigned site. now, he only lists 30pph injector set if purchased with a new chip. the injector only page begins with 42pph set.

what he shows in the 30pph injector set with chip is the D1720BA injector - zoomed in on that pic to read inj #. that is the single hole noted in the D1720xx series. these and the 42pph units do not come painted black anymore - just a stainless steel body. for me, I would paint those black.

I can get the 30pph, 3-hole 01D034x with the black body, saving me the steps of painting. didn't want to bug him about availability of 30pph injector set of 6 when I'd have to paint them anyway.

with the 30pph, 3-hole, I would buy a set of 8, flow them to confirm and know what the two spares flow should I ever need them.

 

[dynoman]

What is also pretty cool is watching the pintle ball welders , 360 degree laser weld that little ball onto the end of the pintle shaft smaller than a toothpick . That has a camera on it also and on the screen it looks like it's the size of a baseball !!

 

[Anthony P]

Thanks for the suggestion Sam. always enjoyed the behind the scenes take of how things are made - the details. something to add to the lunchtime break viewing to feed the learning quest. that tv series "how it's made" ran for maybe two decades. never gets old. Cheers to your new daily schedule. You put in your time, now reap the rewards of your efforts.

 

[dynoman]

Thanks for the suggestion Sam. always enjoyed the behind the scenes take of how things are made - the details. something to add to the lunchtime break viewing to feed the learning quest. that tv series "how it's made" ran for maybe two decades. never gets old. Cheers to your new daily schedule. You put in your time, now reap the rewards of your efforts.

One of my favorite shows . I always learned better by doing something than from reading books .

 

[Anthony P]

I can appreciate that. yes, there needs to be a better balance of theory and application in education, regardless the level. I had instructors spend the entire course (16 weeks) lecturing about the centuries of evolution for various theories to what is the accepted equation today while never offering any discussion regarding real world application. It was only in the hands-on lab assignments where a portion of what we were taught in theory could be applied to real world. makes for a lot of self-instruction and questions the huge cost of this higher education. well, I'm way off topic so I'll stop.

 

[Chuck Leeper]

I believe that all fuel injectors that GM makes are multi hole injectors including the direct injection ones . I just retired from the GM plant that makes the injectors , rails and truck manifolds . The spray pattern is checked with a camera and must meet certain parameters on very tenth injector built . They build approximately 30,000 injectors per day . On the new injectors they are laser drilling the holes the size of a hair and i believe there are 5 of them on each injector . This is some of the equipment I serviced .

Some of the multi hole design is no doubt revolving around emission requirements.
Aftermkt units with very tight patterns, and higher flow rates may be better on the performance end but can affect idle quality and smog output.
It would be nice to be able to do the "inj end angle" adjustment on the older ecms.
Bigger injs with better idle control are a benefit of that feature.

 

[Anthony P]

thanks Chuck, I was thinking about contacting you but didn't want to bother you with seemingly basic fluid modeling for those that know.

you summed it up better than my sometimes long winded, round about way getting caught up in the details.

that 3-hole 30pph injector I referenced seems to be a choice for the honda b-series guys in some capacity. was thinking it should be something to be aware of and possibly utilize going forward rather than continuing to select the same style green stripe / green band 5207009 units that have been around since the revolutionary disc injectors became mainstream in early 1990s(?).

For stock replacements at 30pph, a single hole 4-degree pencil spray pattern probably won't make a hill of beans difference to an equivalent newer design 3-hole spray pattern. perhaps the newer design 3-hole yields better atomization as Chuck noted for fuel economy and emissions.

just something I could spend an afternoon on at an inj flow bench staring at what the injectors do at various pressures. ahh, the details and always wanting to tinker and learn...

 

[SCOOBY DOO]

Some of the multi hole design is no doubt revolving around emission requirements.
Aftermkt units with very tight patterns, and higher flow rates may be better on the performance end but can affect idle quality and smog output.
It would be nice to be able to do the "inj end angle" adjustment on the older ecms.
Bigger injs with better idle control are a benefit of that feature.

Chuck, how much better are Erics chips for idle control for injectors. I ran 80's with that 212/212 and you could put a cup of coffee on the hood and you wouldn't get a ripple out of it. I THINK they were Siemens as I got them from Eric.

 

[Chuck Leeper]

Chuck, how much better are Erics chips for idle control for injectors. I ran 80's with that 212/212 and you could put a cup of coffee on the hood and you wouldn't get a ripple out of it. I THINK they were Siemens as I got them from Eric.

I've not done that comparison.
We had some connections to ATR as they were about an hr+ from us.
They did some chips that they didn't sell to the general market. However, this was back when the inj choices were much smaller.
We also had some of Joe Lubrant chips, a couple from Red, and a few we tried to do ourselves.
I sold my chip burner to a guy in Sweden, many yrs ago.
After that, we did the aftermkt ecm systems. Speedpro, Accel, FAST, etc.
The hi end was the Motec, but it was on the SBC.
I think Eric has the chip business down pat. For anyone ordering his stuff the key is ACCURATE input!