fuel injectors????

[RICH MUISE]

Any of you guys out there knowledgeable on fuel injectors? I spent a few days trying to find out what the Mark VIII's OEM fuel injectors were rated at, to no avail. Even though Motorcraft replacements are no longer available, even the Lincoln dealer service dept had no clue what the originals were rated at. Two pages of details of the injectors in the service manual, but no mention of # ratings!! The original injectors were made by Denso, but even with the number, I could not find the ratings.
I found some rebuilt injectors on eBay (not to buy but looking for info) that were rated at 30#.
With Motorcraft not available in either injectors or coil-on-plug coils, I decided to go with Accell for both. They make injectors in a dozen different ratings, so with what little info I could find I ordered 30#. They came in yesterday, and wouldn't you know it, all the info I needed was printed right on the box!! Going by horsepower Apparently, my originals were probably somewhere around 23-26#.
So, my question is, what are the pros and cons of going with a higher-rated injector on a stock engine? Is it akin to having too much carburation on an old-school motor? Is going from 26# to 30# going to make that much difference? (particularly adverse difference). Will it adversely affect MPG? My motor's injection control is timing (time open), btw.

[81TTA]

So, my question is, what are the pros and cons of going with a higher-rated injector on a stock engine? Is it akin to having too much carburation on an old-school motor? Is going from 26# to 30# going to make that much difference? (particularly adverse difference). Will it adversely affect MPG? My motor's injection control is timing (time open), btw.

Your ECM is calibrated for the flow rate of the original injectors.  So, when running open-loop, you'll be running richer with the new injectors compared to the old ones.  This will affect MPG (lower) and potentially first-start idle quality.  You'll have more fuel delivered at wide-open-throttle (WOT) as well. 

Once things are warmed up and in closed loop, the O2 sensor should bring the injection timing down so the engine will run just like it had with the old ones.  There's usually a "window" of allowed +/- fuel correction before a DTC will set.

My guess would be that if your originals were on the high side (i.e. 26-ish or 10-ish percent), you probably won't notice a lot of difference.  But, if they were closer to 23, the difference could be noticeable.  There are usually a number of operating conditions where the injector timing is directly "tweaked" (i.e. engine start, cold engine operation, throttle transitions, etc) that will now result in more fuel than you had before.

Not unlike so many other engine component changes (carb, camshafts, exhausts), the answer to "what will happen" is "it depends".  I wish I had a detailed answer for your situation....

[RICH MUISE]

Not sure if my OBD 1 ECM is capable of making adjustments on the open time of the injector. Guess I'm fixing to find out. I bought the coils and injectors from Holley performance parts, just found out they have a pretty cool website with a video explaining how injectors work. A comment he made was a higher rated injector could solve issues such as a code saying a bank is running lean. That happens to be a code thrown on my car since day one.......also a reason why I'm not sure if my ECm can adjust that. The injector set is $400+, and I'm waiting to find out if I can return them if they do not work out, or if not, I'll return them unopened.  I tried calling their tech line today, no answer. Maybe I'll have better luck getting thru on Monday.
Thanks for your response.

[81TTA]

Your ECM definitely has the ability to adjust the injector timing.  All domestic OBD1 controllers have that capability.  Even the ones used with electronically-controlled carbs.  Effectively, anything with an O2 sensor will use that to adjust fuel delivery under the right conditions. 

The issue is the adjustment is generally only made when the O2 sensor is operating (i.e. closed-loop).  In any open-loop operation, you'll have more fuel with the new injectors than you had before.  Some ECMs will apply their "long-term" learned fuel adjustments to open-loop.  There's a possibility your ECM might do that.

If the code you're throwing for lean operation is really due to fuel delivery and not due to a bad O2 sensor, misfire or exhaust leak, the larger injectors will move things in the right direction to keep the code from setting.  The root of that code would likely be that the fuel adjustment system is hitting the limits on how much longer it can open the injector to compensate for the lean condition.  If this was on one bank and not the other, it would seem like the cause wouldn't be so much the injector size but something else?

[RICH MUISE]

"If this was on one bank and not the other, it would seem like the cause wouldn't be so much the injector size but something else?"
 That was my thoughts exactly. Very true especially on the Lincoln DOHC versions. The 16 runner intake is supposed to run on 8 of the 16 until 3,ooo rpm's when the additional runners open up. I'm not 100% sure the butterflies that open/close those 8 extra runners are operating correctly, so it's possible that the one lean bank is getting too much air causing the lean condition. It's very difficult to see the vacuum mechanism that operates those butterflies because of their location, but I'm going to figure something out......maybe a camera scope thingy. They were operational when I installed the engine.

[RICH MUISE]

OK........got the new plugs, injectors, and coils installed. It runs soooooo much better. even sounds better. I always had an issue with the car not wanting to respond when at highway speeds, in overdrive, going uphill. giving it a little gas did nothing, so I'd take it out of OD or hammer it. Not so anymore! It accelerates just fine going uphill in OD now. Yay!!! Runs smoother at idle also.
LOL, Yeah, we have some hills around Amarillo, just had to drive a bit to get to them.

[Fairlane62]

That's great Rich.  Might even result in fuel mileage improvement.  Take it over to Palo Duro and see if it kicks down coming out of the canyon. 

[RICH MUISE]

Sounds like you know my area........The area of Palo Duro near my house (6 miles) is not anything like what the locals call "the overlook" near Silverton (an hour south of me). My jaw dropped open the first time I saw that area, definitely not anything you'd expect in N. Texas.
I took it 25 miles north on 287 to the Canadian river area. Lots of miles-long inclines that was perfect for my testing.

[RICH MUISE]

Did a car show in Kansas yesterday. The car ran so much better than the same trip last week. 360 miles. Almost no difference in gas mileage at 19.5.

[81TTA]

That's great to hear!  I didn't think to ask why you wanted/needed to replace the injectors.  Sounds like your originals might have been so bad that the difference in the new ones isn't making a big difference?