Cliff Harris

I recently replaced my stock injectors with the yellow Bosch III 280-155-700 injectors. They have been in my car about 2 weeks and I drive this car every day, mostly in town, but I also drove some highway miles. We have a stretch of I-5 near where I live and speeds usually get up around 80 MPH. I figured that after 2 weeks the ECM has settled down and adapted to the new injectors. It was really rough when I first started it with the new injectors but smoothed out after about 5 minutes.

I wanted to see how these injectors worked with a completely stock tune, so I took a little drive from my house to the local recycling center to drop off the oil from my car. The engine was completely warmed up when I started and the whole time was in closed loop mode. This trip is about 5 miles, all on surface streets. I had the trans in Drive for the whole trip. I used Diacom to do the data logging. Diacom sets a buffer size and stops recording when it fills up the buffer, which did happen at 5600 records. I don't know when that happened during the trip. I have a vague recollection that I set the limit higher, but 5600 was what I got. I imported the data into Excel and sorted it by BLM cell number. Then I did some calculations on the data, as explained below.

My '86 has a BUA 9340 EPROM (auto trans, 3.07 rear axle ratio, unleaded gas). There were two versions of this EPROM, 1728 and 9340. I have never seen an explanation of the differences between these two versions. My guess is that the 9340 is for cast iron heads and the 1728 is for aluminum heads.

Here's a chart I made of my BLM table that shows the relationship between the various cells (RPM on top, air flow down the side). I have never seen a chart like this anywhere, so I guess I'm the first one to publish it (readers of the Forum have seen this before, as I have posted it in several threads):

Based on the boundary values, I didn't think it was possible to get into cells 3 and 12. We'll see...

I put the data I logged into a chart using the above table as a guide. The cells all correspond to their positions in the above chart. Notes:

The top numbers are the range of BLMs that I datalogged. For example, 118 - 120 in cell 0 means that the lowest BLM was 118 and the highest was 120.
The lower numbers are the average of all the BLMs for that cell. I rounded at 1 decimal point because I didn't think being more precise would be meaningful.
The numbers in parentheses are the number of records that were in that cell. (1625) in cell 0 shows that I spent a lot of time idling at traffic signal lights.

Looking at the data log of RPM vs. MPH: 700 RPM = 16 MPH, 1200 RPM = 31 MPH and 2000 RPM = 48 MPH. I added those numbers to the chart because they give more meaning to the cell boundaries. The highest speed recorded was 55 MPH.

I wasn't too surprised to find that the ECM never got into cells 3 and 12.

Cells 8 and 13 only have 1 entry each, which I also expected based on the RPM vs. air flow boundaries.

I've said in the past that based on air flow vs. RPM that the ECM would spend most of its time "on the diagonal" in cells 0, 5, 10 and 15, so I was surprised that very little time was spent in cell 5. Apparently traffic flows faster than I thought. I was also surprised to see so much time spent in cells 1 and 2. I guess those were times where I was coasting with the throttle closed.

The lower BLM limit is 108, so I was surprised to see how much time was spent near or at the limit. When the ECM calculates the BLM value, if it's below 108 it sets it to 108. The problem with this is that you can't tell how low it would have been. I see 108 in cells 1, 2 and 6. The ECM also subtracts some fuel for "deceleration enleanment", so that is also a factor. Based on the air flow rates, I suspect those were times when I was coasting so being on the rich side isn't too much of a cause for concern. I did see some times when the injector pulse width went to zero, so DFCO (Deceleration Fuel CutOff) was kicking in.

The BLMs look nice in cells 5, 10 and 15. Those are the important ones, so I think I'm in good shape with my new injectors.

Now WOT in open loop is another story. I haven't data logged there yet...

MrWillys

I'm very surprised you ran rich with this injector, because it is shown as a 20 lb injector. I've programmed several vehicles running this 280-155-700 who were experiencing lean conditions, and after resetting flowrate to 20 lbs the blm's came back down closer to 128.
My guess is that some make internal modifications to this injector to increase flowrate.

http://www.witchhunter.com/flowdatapix/b0280155700.jpg

MikeT 90 C4sixer

Interesting post. So why are you using the yellow Bosch 3 in your 350 TPI motor?? Just trying them out, to see what they can do? Lots of posts on these boards, about these injectors not being true 22lbers. I put in the blue Bosch 3's (24lbs) last summer, and actually my tune came in real good with the stock settings. My BLMS were way off with the stock injectors, but in all fairness, i had 1 bad inj and some mismatched units.
My motor is nearly stock, and i havent done much in the tune. But did change the injector constant to 24, which was recommended by FIC.
Also, scanning with Diacom? wow, that is an old DOS base scan tool, yes? I started with that eons ago! Must try Tunerpro RT ver5. Can make a histogram tables of what ever you want, showing BLMs vs airflow vs RPMs. Very powerful stuff!

Cliff Harris

I bought these injectors in December 2011 but never installed them. Back then everybody was raving about how good they were, etc. These were the so-called "rebuilt" injectors that Jon of FIC sold and they were a super deal at the time.

Some of the stuff that MrWillys said about these injectors sort of scared me, so that was another reason I put off installing them. I wrote an email to the support email address on the FIC web site asking if I could trade them in on the orange 22 lb. Bosch III injectors they show for my car. I never received a reply. I decided to install them anyway since I had the engine apart replacing a blown head gasket.

I was checking them out today and the idle is definitely smoother than the old injectors. The old ones were the original injectors (118K miles) and I had them cleaned and flow tested a few years ago.

I haven't seen any knock counts (from going lean) in my data logs, but I haven't pushed the engine very hard either, so that's an area I need to explore. I've been trying to figure out where I can do some WOT runs but where i live those places are hard to find nowadays.

I don't have a wideband O2 sensor (one of the items on my shopping list), so I can't really evaluate these injectors. I did put an extra O2 bung in my new front Y pipe, so that part is covered. A future project...

Bandit1977

Cliff,
Are those orange 22 lb. Bosch III injectors (as supplied by FIC) a true 22lb injector, or do they also require the fuel pressure to bumped up to compensate that they're not actually 22lb injector at 43.5 psi?
Ken

MrWillys

Cliff,
If yours are not giving you hign BLM's in closed loop then I would say you're okay. WOT can be observed from a datalog from the narrow band watching for .860 to .900 volts. The set I tested back in 2012 gave me counts all above 150 until I modified flowrate, but if your are within reason then there's no reason to complain. My experience has been that more people complain they're lean than not.
FWIW, FIC is no longer selling these as 22 lbs.

RossyHusker

Cliff. I am curious how it is running now that you have had the Bosch 3's in for a while? I am considering buying a set. Thanks

Cliff Harris

Runs great. I drive this car every day and haven't seen any problems.

I haven't gotten the wideband O2 sensor hooked up yet so I don't know how it behaves at WOT. Things keep getting in the way. I have an appointment on Monday for Magnaflow to look at the problems I have with their front Y-pipe, for example.

I have a vague recollection that two years ago when I bought these injectors that FIC was drilling them out for higher flow. They are still showing them as the correct injectors for my car, so they could still be doing that.

RossyHusker

Thanks Cliff!

samsonb

Yeah, I put in the 22# yellow Bosch III, and I ran super lean. Ended up putting in the blue 24# Bosch III, and my BLM's were dead on in the "safe" range stock setup.

fl_799

Great post Cliff, thanks for sharing. Glad to see that that the injectors are working out. Goes to show you that there is no better piece of mind than data-logging and seeing what the heck is going on! Hope your WOT is with the wide band. Should be in the ball park!

Whats your fuel pressure?

Cliff Harris

I am running a stock style pump with the stock non-adjustable fuel pressure regulator. Right now my fuel pressure gauge is not working (the highest it will go is 20 PSI and it sticks there when the engine is shut off -- if I tap on it then it will go to zero PSI), so I don't know what the actual pressure is.