please educate me on lb rating of fuel injectors

[gwb72tii]

I'm getting to the point of late stage reassembly of my motor, and find out the PO was using Ford Mustang injectors. Near as I can tell they are rated at 27lb.
Jim at Metric Mechanic suggested going completely stock on my motor, from injectors to the ECU (no chip). I believe stock Bosch injectors are rated at 19lb?
Seems like a big jump going to 27lb injectors, yet on the 3 day adventure home from Mesa, AZ, the car ran fine (when it was running lol).

So what is a lb rating on an injector other than more fuel being delivered at the same psi? A 27lb injector seems like it would flood the motor?

[Mike W.]

I thought I'd heard the Mustang injectors were rated at something like 22 pounds. At least a couple of things are at play here, the first is the ECU has significant capabilities to tweak things correctly due to the O2 sensor input. I think 22 to 18.5 would be well within it's abilities. Next is what fuel pressure is it being rated at? 2 bar, 2.5, 3 bar, while it's not linear, it has a strong influence on flow obviously. Using an L jet injector from a BMW M30 they show ratings of 22.9 or 29 depending on pressure. And for more stats than you ever wanted to know, check out the list on this page, http://www.users.interport.net/s/r/srweiss/tableifc.htm

I can't say I've actually needed it, but it's helped my satisfy my curiosity over the years, he's had it up for a while.

[Blue Shadow]

The higher flow injector will have a much lower flow time. Going too far isn't going to be good.

but on another note for these injectors, I replaced the original injectors in my car with whatever the mustang 4 hole jobs were when the originals were getting tired. Hot starts were taking some time.

The change going to the Ford parts made the hot start equal to the cold start, ok that is fine but the cold start suffered.

Weatherford BMW in Berkeley would change the ICV on any used bimmer they took in. I was in NorCal 88-91. Reason was one could reach in and bump the key and the car would start. This is the cold start I had. But the Ford parts made it a couple turns of the motor, not bad but not like the car did before the change.

I might swap back when the ford parts get tired but I would have to send out the original injectors for a refresh.

[Mike W.]

The higher flow injector will have a much lower flow time. Going too far isn't going to be good.

but on another note for these injectors, I replaced the original injectors in my car with whatever the mustang 4 hole jobs were when the originals were getting tired. Hot starts were taking some time.

The change going to the Ford parts made the hot start equal to the cold start, ok that is fine but the cold start suffered.

I had similar problems with the -203 injectors, 85/86/? They tended to get dirty and leaky with my driving patterns. Went thru 3 sets I think. I switched to the later -714 and no more problems. But cold start was always good, if they were leaky it just made it like an extra prime, but it was too much so if the engine was hot.

Weatherford BMW in Berkeley would change the ICV on any used bimmer they took in. I was in NorCal 88-91. Reason was one could reach in and bump the key and the car would start. This is the cold start I had. But the Ford parts made it a couple turns of the motor, not bad but not like the car did before the change.

They swapped the ICV on 85+ 535's? I found that system to be rock solid as long as the TPS was adjusted correctly. Now the earlier 2 wire on etas and especially 533s were very problematic. Those I could see a preemptive changeout.

[gwb72tii]

What I am realizing is the e28 535i version is more complicated than I am used to when wrenching.
Where is the TPS located?

Also, what is the pound rating on a fuel injector referring to?

[Mike W.]

What I am realizing is the e28 535i version is more complicated than I am used to when wrenching.
Where is the TPS located?

Also, what is the pound rating on a fuel injector referring to?

Sorry, so many of us are so used to usual acronyms we can sometimes, unintentionally, talk over people. TPS is Throttle Positioning Switch, which is located on the Throttle Body. Except on 535i EH auto transmission cars, it's a pretty simple switch input to the ECU, closed throttle which is idle, above idle, but not wide open, and wide open, which is really more like 2/3 or more.

FPR is fuel pressure regulator.

Pound rating. The link I posted details it a bit more, but it's "pounds per hour" in maximum fuel flow. It kind of doesn't matter as long as they're all using the same rating system.

[Galahad]

You want to make sure you stick with whichever of high / low impedance your ECU expects, mixing them can cause problems. Also, the stock injectors are going to be single spray, the 2 / 4 hole injectors work well for 4 valve heads but can end up spraying most of the gas on the walls of the intake port in a single valve intake runner like the M30 has.

I thought I'd heard the Mustang injectors were rated at something like 22 pounds. At least a couple of things are at play here, the first is the ECU has significant capabilities to tweak things correctly due to the O2 sensor input. I think 22 to 18.5 would be well within it's abilities. Next is what fuel pressure is it being rated at? 2 bar, 2.5, 3 bar, while it's not linear, it has a strong influence on flow obviously. Using an L jet injector from a BMW M30 they show ratings of 22.9 or 29 depending on pressure. And for more stats than you ever wanted to know, check out the list on this page, http://www.users.interport.net/s/r/srweiss/tableifc.htm

I can't say I've actually needed it, but it's helped my satisfy my curiosity over the years, he's had it up for a while.

Going 2.5 bar to 3 bar is very close to linear - accidentally used the wrong regulator in my eta for a while so I have a few tanks worth of data on that.

I don't know if the older ECUs would be able to compensate the ~15% between 22 to 18.5, that seems like quite a lot of range.

[turbodan]

27lbs/hr is the mass of fuel delivered if that injector was open for 60 minutes at a given fuel pressure, usually 3 bar. They operate on pulsewidths on the order of milliseconds so fuel is metered into extremely small doses. Another unit of measurement is cc/min, which is easier to verify if you're testing on the bench. Same idea though, except it's volume over time instead of mass.

Sticking big injectors into an engine just for the hell of it is never a great idea. The Motronic version used on the B34 does have the ability to adapt to a certain extent. How much it can do is unknown. At best, big injectors will end up running the same as the original injectors once the DME dials the fueling back down to where it wants it.

I don't think it's going to be able to pull back enough fuel to make 27 lb injectors work, so it's going to force the engine to run rich. This doesn't make more power, it just uses extra fuel and leaves a trail of stink everywhere you go.

Larger injectors make sense if you're revving high enough that the stock injectors can't deliver the required fuel in the available time. Never seen anybody pull that off. Turbo engines need bigger injectors because the air is compressed, more density means more oxygen requiring more fuel to maintain appropriate air/fuel ratios.

My turbo M20 is running 30lb injectors right now, and at .8 bar they are running close to their limit in terms of duty cycle. A non-turbo M30 would likely never be able to max out a 24 lb injector in any state of tune, and for a mildly modified or stock M30 the original injectors will be perfectly fine.

[tschultz]

Note with bigger injectors the wide open throttle is not scales down, so you could be running richer than originally planned. The ecu will not adjust the wot map, so you could be burning more fuel and losing power if you go with injectors too big and run like 10:1afr instead if the original 12.5:1 mix...

Most people don't consider this when they swap to bigger injectors and have mediocre performance. Hence the need for standalone to really dial everything in for cruise, wot and all other operating conditions.

[gwb72tii]

I ordered stock Bosch injectors. Like a lot of other things I’ve taken apart and worked on, it’s going to be fingers crossed time.

[gwb72tii]

This is what came with my car, Ford injectors. I have new Bosch injectors to replace these.
I believe the spec on this injector is 27lb which is significantly more than stock, even though the motor that came with Maeve is stock.

As I've done previously, first person to reply to this post can have the injectors free, you pay shipping. FYI Maeve ran fine before yanking the motor out.

[kojo96]

If they're still available, I'd like to take them.

[gwb72tii]

they are yours kojo. pm me shipping info and I'll get them off to you as soon as I get the Bosch injectors installed, next week.

[kojo96]

they are yours kojo. pm me shipping info and I'll get them off to you as soon as I get the Bosch injectors installed, next week.

[turbodan]

Might be worth verifying the fuel pressure regulator is still stock. It may have been changed to a 2.5 bar to help alleviate the overfueling. AFM tampering is an unfortunate possibility as well. That was the trick in the old days to get Motronic to run with big-ass injectors for turbo setups, just crank the spring up until it runs okay off-boost.

If that DME was able to dial in a 50% larger injector on it's own I would be amazed.

[gwb72tii]

Seems like a big jump to me, but I'm a noob with he e28. I can wrench but the e28 is way more than just nuts and bolts like my tii.

[ahab]

Great point by tschultz. At WOT you're getting a set of "canned maps" and the ECU isn't reading O2 sensor input to compensate for overfueling. Motronic 1.3 is significantly better at managing pulse width, IIRC it's a wider data path and a faster processor which enables it to respond more quickly. Although I agree that 27lb seems like it would overwhelm anything but a standalone system so it's likely there's some other wizardry is taking place. And only since it hasn't been pointed out, the OE injectors are single pintle and most folks upgrade to the Ford "Mustang injectors" because of the superior 4 pintle design which results in finer atomization of the fuel through 4 small orifices rather than one larger one. The M30 was known for excessive carbon buildup back in the day from condensed fuel pooling around the valves and those injectors should help in that department. The last time I checked Stan's injector reference sheet I believe OE and Mustang injectors are both rated at 19lbs/hr.

[gwb72tii]

I'll post a pic later but the stock Bosch injectors are a four pintle design as well.

[ahab]

Correct, but single instead of four.

[gwb72tii]

here's the pic:

[ahab]

That is indeed a four pintle injector however I don't believe that's an OE M30B34 injector. OE was 280150714 and was single pintle.

[Mike W.]

That is indeed a four pintle injector however I don't believe that's an OE M30B34 injector. OE was 280150714 and was single pintle.

The -714 is the later, and better IMO, OE 535 injector. The early ones were a -203 and more prone to getting dirty and leaking. And 714s do flow about 3.5% more.

[gwb72tii]

The model injector is Bosch 62417. Apparently there is an OEM style and a newer 4 pintle style. Both fit the 535i motor, and I'm assuming the 4 pintle design is superior?

[ahab]

The -714 is the later, and better IMO, OE 535 injector. The early ones were a -203 and more prone to getting dirty and leaking. And 714s do flow about 3.5% more.

Interesting. I've owned and/or parted no less than a dozen E28s with an M30 and have never seen anything beyond single pintle 714s in them.

[Mike W.]

Yep, mid 86 change. The 203s are also single pintle, but somehow different. Quoting from you know where.