benefit of 19lb injectors

[Bimmer_man]

I have a M20B27 that im thinking on putting some money into and i may consider a B25 head if i can find one in the yard. but what is the benefit of 19lb injectors on a M20B27?

[frankenbeemer]

I don't think they have any benefit unless you are doing other mods to the engine.

[Bimmer_man]

other mods would be

Exhaust manifold
chip ( not sure from where yet )
Maf or M30 AFM depends on what head im using

that would be all for now i suppose

[jlevie]

Since I can tune a stock M20B25 for an AFR below 13.5 (richer than you'd want on the street), I can't see any performance advantage over the stock (14lb) injectors other than the better spray pattern. Which might help fuel economy at lower engine speeds.

I'd think that you'd need some serious internal engine work to increase the mass flow though the engine before larger injectors were needed.

[Bimmer_man]

yeah im just curious cause i see a lot of people with M20s using the 19lb injectors and i wanted to know why really

[dnguyen1963]

yeah im just curious cause i see a lot of people with M20s using the 19lb injectors and i wanted to know why really

And yes, you would find that many of them complain about poor idle and gas mileage. 19 lb injectors are for serious modders.

[Herr Faust Schinken]

the PO of my car installed 17.5 pound M50 injectors they seem to work fine idles great gas mileage seems fine (18mpg which is ok considering i almost never drive on the freeway) and it nice because i have a bit of headroom if i decide to mod the m20

[CarsSuck]

I'm skeptical of the gas mileage claims. I've been running 19lbers (w/ chip) for years. Mostly highway driving gets me 24 mpg. Low speed/stop and go driving will drop me to 17. Car runs okay, but it idles too high, I'm pretty sure it's got an air leak somewhere, but I'm too cheap to get it smoked and it runs damn good otherwise.

[JinormusJ]

I've always wondered this myself
Always wanted to try out the 17lbs + chip combo

[MonkeyMan]

I'm running 19# with a miller psik and war chip.. zero issues and perfect idle (although slightly lumpy with cam), average around 25mpg mostly highway driving

[jlevie]

yeah im just curious cause i see a lot of people with M20s using the 19lb injectors and i wanted to know why really

My guess is that folks think that bigger injectors are going to yield more power. But if you understand how the DME works you will see that fallacy in that. Assuming the O2 sensor works, the DME will adjust fuel delivery to try to achieve stoich operation (14:1). Which is why the engine runs poorly for a while after swapping in larger injectors. There is enough trim available to accommodate 17lb injectors, but 19lb injectors are a bit too big for the available trim. A chip tuned for 19lb injectors is almost a necessity.

There are claims that the better spray pattern of later vintage injectors will help mileage at lower engine speeds. Since I'm perfectly happy with OE injectors, I can't say if that is true or not. But from lots of dyno time I can say that the OE injectors (if clean and working properly) are all an M20B25 can possibly use unless serious mods to the engine internals have been done.

The limiting factor on an M20B25 is the head, not the AFM. To increase mass flow through the engine displacement and head flow must be increased. The Metric Mechanic folks have this figured out and I suspect the folks at Korman have also.

[SlamedIAm]

the PO of my car installed 17.5 pound M50 injectors they seem to work fine idles great gas mileage seems fine (18mpg which is ok considering i almost never drive on the freeway) and it nice because i have a bit of headroom if i decide to mod the m20

I also use 17.5# injectors.

From what I understand M50 (17.5#) injectors run at 3.5 bar.

M20's run at 3.0 bar

17.5# at 3.0 bar = 15#/hr

Somewhere around those lines.

[digger]

find a good set of B25 injectors and get them cleaned and flow matched.......... or get the M50 ones which are only slightly larger when the difference in rated pressure is considered. The M30 engines use ~19lb and these are good enough for a much larger engine and even when modded so 19lb is overkill on the majority of M20's. I used 18lb ford ones on a stock engine many moons ago when i was diagnosing a propblem and it works but it is not ideal

[MR 325]

19lb injectors are too big. I am also a fan of the 17lb M50 injectors.

[CarsSuck]

Okay gents, this is the magic question. I have a miller MAF and chip for 19#ers. Miller will no longer answer my emails ( haven't answered any emails since I gave them my money a few years ago). Do you guys think I can run M50 injectors on that tune?

The whole point of getting the Miller kit was to replace my junk AFM, I already had the 19#ers/MarkD combo and it was great. I really don't want to revert back to a stock system because I'd have to buy injectors and a new AFM.