Is fuel injector pulse different for each cylinder?

[greenberet]

Does anyone know whether the stock engine management system in an NSX is capable of sending a different fuel injector pulse width to each cylinder or is it only able to vary the pulse width per bank?

I heard that some engine management systems can tell which cylinder is running rich or lean even without having separate O2 sensors for each cylinder by correlating what the common O2 sensor is reading with which cylinder has just fired. So it can tell not just if a bank of cylinders is running rich or lean, it can figure out which cylinder is running rich or lean in that bank and adjust the fuel for that cylinder accordingly.

Does anyone know if ours does that?

 

[enkrypt3d]

Does anyone know whether the stock engine management system in an NSX is capable of sending a different fuel injector pulse width to each cylinder or is it only able to vary the pulse width per bank?

I heard that some engine management systems can tell which cylinder is running rich or lean even without having separate O2 sensors for each cylinder by correlating what the common O2 sensor is reading with which cylinder has just fired. So it can tell not just if a bank of cylinders is running rich or lean, it can figure out which cylinder is running rich or lean in that bank and adjust the fuel for that cylinder accordingly.

Does anyone know if ours does that?

No the OEM ECU does not do that... All injectors should be running at the same capacity... if u are having issues I suggest having them balanced and cleaned or replaced if that doesn't work.

 

[Hugh]

Since we're on the subject of injectors, is it a good idea to have the injectors balanced, cleaned, inspected based on time? Mine have 230,000 miles on them and to the best of my knowledge have never been removed.

Everything seems fine but sending them to RC Engineering can't hurt right?

 

[nigel]

Correct o' wise one.
In your case you might send a spare set so as not to have any down time and that would make certain they're good. No change, no foul.
You use the same fuel brands I do but I still shove a bottle of "Chevron Techron" injector cleaner in the tank every four or five tanks to be sure the intake tract is kept as clean as possible. It's only six or seven $ at Advance.
After all, 230,400 isn't much for a well maintained car like yours and it's a fairly inexpensive process.
That's also a good time to replace the inexpensive o-rings, (all) that can, (and will) after time fail from heat and cause fuel and air leaks. Your are overdue.

Cheers
nigel

 

[theman1990]

I have 92,XXX miles on mine and just sent them out, they were "ok" but one was really jacked and listed as "dripping." They all came back as "Excellent." Haven't run it yet though.... no suspension and all....

 

[greenberet]

I recently checked the spark plugs on my front bank of cylinders to see whether I should switch from the standard NGK PFR6G-11 to PFR7G-11. Two of the plugs looked like they had almost gotten too hot, but the plug closest to the throttle body looked a bit carbon fouled. Not wet, just dark.

If the engine management system varies the pulse width to each injector, then that most likely wouldn't be due to running rich. It would more likely be due to that cylinder starting to burn a little oil - despite religious oil and filter changes every 3750 miles and babying the engine until it's warm. If the EMS doesn't vary the pulse width per injector, maybe the injectors for the cylinders with the clean plugs were a bit clogged so the EMS increased the pulse width far enough that the fuel/air mixture was correct on average. Two may have ended up a little lean and one a little rich, but correct on average.

In any case, I've had the injectors cleaned and on Tuesday they're going to be installed along with fresh spark plugs, new O2 sensors, etc. Since the injectors are never perfectly balanced, I'd like to put the injectors that flow a bit more to the cylinders that tend to run a little lean in an NSX - whichever those are.

But if an NSX's stock engine management system cannot vary the pulse width per injector, that's good to know - thanks enkrypt3d.

 

[enkrypt3d]

Since we're on the subject of injectors, is it a good idea to have the injectors balanced, cleaned, inspected based on time? Mine have 230,000 miles on them and to the best of my knowledge have never been removed.

Everything seems fine but sending them to RC Engineering can't hurt right?

yes you should definitely have them balanced and cleaned... 2 of mine were dripping after only 80K miles... and I could feel an immediate improvement after they were cleaned...

Also be SURE to replace all the O-rings and seals that go around the injectors and coils... Replace all your coils and spark plugs too while you are in there! Its pretty cheap and it will also improve performance!

 

[Hugh]

Correct o' wise one.
In your case you might send a spare set so as not to have any down time and that would make certain they're good. No change, no foul.
You use the same fuel brands I do but I still shove a bottle of "Chevron Techron" injector cleaner in the tank every four or five tanks to be sure the intake tract is kept as clean as possible.

You're reading my mind. I'm gonna pull the injectors from one of my extra motors then swap them into Charlotte when they come back.

Using a Top Tier rated gasoline gives you all the cleaning you should require but tossing in a bottle of Techron every few tanks certainly can't hurt. I throw in a can of Sea Foam every 2 or 3 months.

 

[greenberet]

yes you should definitely have them balanced and cleaned...

After speaking with Bosch and DeatschWerks and reading the websites of RC Engineering and WitchHunter, I think calling the injectors "balanced" is a bit of a misnomer. All these guys ultrasonically clean and backflow the injectors, which improves the spray pattern and increases the flow a bit. None of them actually modify the nozzles to proactively "balance" the amount each injector flows.

That the flow is more even after the treatment is simply a byproduct of cleaning them. To balance them, you'd have to modify the nozzles or have a large pool of injectors and then match up the ones that have the same flow rates. As far as I'm aware, the way it actually works is that you send in six injectors, they clean them, and then they send you back the same six injectors. They will most likely have more even flow rates than before, though.

I read that the design specs of the OEM NSX injectors are that they should flow within 3% of each other from the factory. That means that one cylinder could have an air/fuel ratio of 13.0:1 and the next cylinder could have 13.4:1. If your injectors are more balanced that than, you got lucky (assuming the 3% OEM balance spec is correct).

 

[Gansan]

Does anyone know whether the stock engine management system in an NSX is capable of sending a different fuel injector pulse width to each cylinder or is it only able to vary the pulse width per bank?

I heard that some engine management systems can tell which cylinder is running rich or lean even without having separate O2 sensors for each cylinder by correlating what the common O2 sensor is reading with which cylinder has just fired. So it can tell not just if a bank of cylinders is running rich or lean, it can figure out which cylinder is running rich or lean in that bank and adjust the fuel for that cylinder accordingly.

Does anyone know if ours does that?

IIRC, BMW has a system where the ECU reads the ionization of the compressed charge in each cylinder by reading how much current leakage there is across the spark plug gap before it fires. This tells the ECU how each individual cylinder is running. As enkrypt3d says, the NSX can't do that.

 

[enkrypt3d]

After speaking with Bosch and DeatschWerks and reading the websites of RC Engineering and WitchHunter, I think calling the injectors "balanced" is a bit of a misnomer. All these guys ultrasonically clean and backflow the injectors, which improves the spray pattern and increases the flow a bit. None of them actually modify the nozzles to proactively "balance" the amount each injector flows.

That the flow is more even after the treatment is simply a byproduct of cleaning them. To balance them, you'd have to modify the nozzles or have a large pool of injectors and then match up the ones that have the same flow rates. As far as I'm aware, the way it actually works is that you send in six injectors, they clean them, and then they send you back the same six injectors. They will most likely have more even flow rates than before, though.

I read that the design specs of the OEM NSX injectors are that they should flow within 3% of each other from the factory. That means that one cylinder could have an air/fuel ratio of 13.0:1 and the next cylinder could have 13.4:1. If your injectors are more balanced that than, you got lucky (assuming the 3% OEM balance spec is correct).

Haha dude I think thats a long way of saying yea its all the same shit...

When I say balance I mean they clean all of the injectors so they spray at or very close to OEM specs which would mean all injectors would be "balanced" again right? No need to over-explain it.

Like I said 2 of my injectors were dripping when I sent them in so yea after I got the same ones back (I never said they modify the injectors btw), they all flowed like a champ...

 

[greenberet]

I wonder whether your injectors were dripping while they were in your manifold, before you removed and shipped them. WitchHunter recommends, "Don't let injectors dry out when they are out of the car. Store them in a plastic bag...". DeatschWerks says their injector cleaning service includes, "Lubricate and Bag: Preserves optimum working condition". If the fuel in the injectors dries out and leaves deposits while being shipped to the cleaning company, that may make any "before" flow and spray pattern assessments look worse than they actually were while in the car. In this thread, people were wondering how accurate RC Engineering's "before" measurements really were.

In any case, thanks for the input. It's too bad an NSX's engine management system can't send different injector pulses to each cylinder. That makes it especially important to have the injectors flowing properly and now it's time to take my NSX to the shop and have some cleaned and flow tested injectors installed.

 

[theman1990]

I zip-lock bagged and shipped mine after I took them out and 4 were rated as fair, one poor, and the other dripping (if I remember right.) They certainly "looked" better when they came back...