17lb or 19lb for A Stock 325i

[Quinthirty]

Hi, I was trying to search for a comparison between 17lb and 19lb injector performance, but couldn't find any. My objective is to make the M20B25 perform optimally, considering both fuel economy and ample power in mind. I'm moving towards replacing the chip with one of those ebay ones, and also plan to replace the worn out injectors with it.

I want to know more about your experience with both 17lbs or 19lbs injectors specifically MPG and power.

Thanks in advance!

Mine is an A/T by the way.

[Earendil]

Stock motor, stock injectors. But clean well functioning injectors will make a huge difference!

Rather a pity (and yet awesome) that BMW designed these cars with no giant bottlenecks, and very very few tiny ones. The injectors are not a bottle neck if they are operating properly. And before anyone says I'm wrong, The Pro-3 racers run stock injectors and pull above stock HP figures from their cars.

[mbonanni]

17

[MR 325]

I recommend the 17lb M50 injectors to anyone with a M20 engine. Otherwise keep them stock.

[BMW_325i]

I recommend the 17lb M50 injectors to anyone with a M20 engine. Otherwise keep them stock.

Would that be part # 0280150415?

I have these and could never get a definitive aswer as to whether they are 17, 18 or 19lb/hr at 3 Bar.

[sayed ali]

19lb from m30 (black ones) + m30 afm + Ebay chip would be a good combo ..

[Sagaris]

There is no benefit to running old style single pintle 19# injectors. Get Bosch Design III injectors if you insist on running 19# injectors.

There is a reason that car companies don't just run 100# injectors on everything just to save money. Running injectors which have a lower maximum flow rate allows a much broader spectrum of injector pulse widths to be used to deliver fuel between idle and WOT. An injector with a higher flow rate will be less precise. It is much more difficult to achieve a good idle with high flow rate injectors ("high" flow rate = relative to the amount of air the engine can move)

There is definitely a benefit to running the M50 17.5# Design II injectors from an M50 or even 19# injectors as long as they are Design III due to their improved ability to atomize fuel which comes from multiple pintles, better pintle cap and internal nozzle design. The optimal scenario would be to run some 14.5# which have the improved design characteristics that the Design II and III's have. I do not know the availability of such injector.

Like MR325 said, run a set of rebuilt 17.5# M50 injectors and better yet, get a MarkD chip, not those stolen Dinan clone chips that only change the full throttle maps. Instead of an M30 AFM, get a refurbished M20 AFM.

[nando]

Im sorry to say this but if you are telling anyone to use 19# injectors on a stock M20 and are not specifically saying 19# Bosch Design III injectors then I invite you to justify your reasoning.

agreed.. sortof.

There is a reason that car companies don't just run 100# injectors on everything just to save money. Running injectors which have a lower maximum flow rate allows a much broader spectrum of injector pulse widths to be used to deliver fuel between idle and WOT. An injector with a higher flow rate will be less precise. It is much more difficult to achieve a good idle with high flow rate injectors ("high" flow rate = relative to the amount of air the engine can move)

this isn't really true. the problem isnt' that the injector is less precise (some of the common large injectors are extremely precise and very fast), it's that your injector PW at idle gets close and closer to the "dead time" of the injector, or the time that it takes to actually open and close the pintles. when you get into this region, fuel flow becomes non-linear and you end up with an unstable, difficult to tune idle.

however... you will NOT run into that on an M20 until you get to very large injectors, over 42# or so, but even some of the 60# high-z injectors have response times under 1ms, which could still have a quite good idle. Not that you'd want to try to run 60# on Motronic 1.3, but to say that large injectors are less precise or that you can't idle with anything over 19# is completely wrong.

There is definitely a benefit to running the M50 17.5# Design II injectors from an M50 or even 19# injectors as long as they are Design III due to their improved ability to atomize fuel which comes from multiple pintles, better pintle cap and internal nozzle design. The optimal scenario would be to run some 14.5# which have the improved design characteristics that the Design II and III's have. I do not know the availability of such injector.

Like MR325 said, run a set of rebuilt 17.5# M50 injectors and better yet, get a MarkD chip, not those stolen Dinan clone chips that only change the full throttle maps. Instead of an M30 AFM, get a refurbished M20 AFM.

agreed

[nomansland92]

I ran m50 green tops with my stock M20 and there was a nice improvement. I think it even help my mpg a little. I would recommend them and they can be used with the stock chip, anything bigger like those 19lb ebay ones aren't going to do any good unless you run a chip and a good afm or even better a maf.

[redsubdivisions]

17lb M50 injectors, 4.10 LSD, and a fleabay chip on my sedan. I noticed a difference...not turbo car fast, but still improvement enough for daily driving. it also seems the car runs a little bit smoother and uses a little bit less gas. Could be just my mind, though. either way, I thought it was a nice upgrade.

[AutoXinE30]

I used 19lb(199cc) Bosch 4pintle injectors from a 5cyl FWD Volvo on my DIYPNP 325i. Only other mods were, deleted AFM and 2.5in exhaust after the cat. I pulled many extras and I can grab the PN when I go home if you want it.

Didn't really feel much of a difference between the stock injectors to 19lb injectors through the MS but, I did like the fact that my duty cycle wasn't in the 90's anymore.

I did like the fact they are much quieter then the OEM ones were though.

[Gregs///M]

I run the plastic body Bosch #17 design III. They gave me more low end torque, better gas mileage, and better idle. I recommend them.

[kman_e30]

I used 19lb(199cc) Bosch 4pintle injectors from a 5cyl FWD Volvo on my DIYPNP 325i. Only other mods were, deleted AFM and 2.5in exhaust after the cat. I pulled many extras and I can grab the PN when I go home if you want it.

Didn't really feel much of a difference between the stock injectors to 19lb injectors through the MS but, I did like the fact that my duty cycle wasn't in the 90's anymore.

I did like the fact they are much quieter then the OEM ones were though.

how did you go about deleting the afm? special tune?

[nando]

MS = megasquirt

[fatsooo]

read a bunch of threads when considering switching mine up
ill make it real simple like above

17# for stock chip, some aftermarket chips run 17# too

19# for aftermarket chip only.

your choice of chip is up to you, but im gunna be saving up for a markd chip as opposed to ebay
i have the 17# m50 injectors i bought rebuilt from a forum member so i can just use these until i save up for the chip