Modern injectors, new fuel rail - no heat soak problem

[HusseinHolland]

9 minutes ago, Captain Obvious said:

Page EF-56 of the 76 Manual says the dropping resistors should be 6 Ohms. I have not measured anything to verify.

And I didn't find a spec for the injectors, but I measured a couple here and came up with about 2.4 Ohms. No accounting for the absolute accuracy (or inacuracy) of my meter, but that's what I got.

Do you know the resistance of the high impedance injectors you are using?

I do not. I can measure one tomorrow & post back 🙂 

 

EDIT - looking up the Bosch # online, 16ohm is the listed resistance value

 

So 16+6 ohm vs 2.4+6 ohm

Edited November 18, 2023 by HusseinHolland

[Captain Obvious]

Cool. I think that would be interesting to compare against stock.

Make sure you short your meter lead tips together and subtract that number from the injector resistance measurement. That shorted reading is lead resistance.

For example... When I was measuring the injectors here today, I stuck both meter leads down into the injector connector and made connection to the blades in the JPT connector. I got 3.0 Ohms. Then trying not to move much, I shorted the tips of the leads together while also still connected to the JPT blades. I got 0.6 Ohms. In theory that 0.6 Ohms is lead resistance (plus crappy meter accuracy).

Subtract the 0.6 from the 3.0 and I got 2.4 Ohms.

The smaller the resistance you're trying to read, the more important it is to account for your lead resistance. Hoping this makes sense?

[HusseinHolland]

14 minutes ago, Captain Obvious said:

Cool. I think that would be interesting to compare against stock.

Make sure you short your meter lead tips together and subtract that number from the injector resistance measurement. That shorted reading is lead resistance.

For example... When I was measuring the injectors here today, I stuck both meter leads down into the injector connector and made connection to the blades in the JPT connector. I got 3.0 Ohms. Then trying not to move much, I shorted the tips of the leads together while also still connected to the JPT blades. I got 0.6 Ohms. In theory that 0.6 Ohms is lead resistance (plus crappy meter accuracy).

Subtract the 0.6 from the 3.0 and I got 2.4 Ohms.

The smaller the resistance you're trying to read, the more important it is to account for your lead resistance. Hoping this makes sense?

Yes - I always check the (meter) lead resistance first - I'm used to doing that for doing resistance checks on ground circuits. My leads are usually .1-.3ohm, depends whether I'm using the probe or clamp set.

[Captain Obvious]

Yeah, I figured you were on top of that, but couldn't hurt to bring it up.

And I hope you get your O-ring stuff worked out. Workmanship stuff is a real pet peeve of mine.

[HusseinHolland]

8 minutes ago, Captain Obvious said:

Yeah, I figured you were on top of that, but couldn't hurt to bring it up.

And I hope you get your O-ring stuff worked out. Workmanship stuff is a real pet peeve of mine.

Thanks  -yes - having to re-do stuff due to product quality control issues is a pain in the butt. I really can't move on to other things (in my head) until I have the issue resolved. 

Edited November 18, 2023 by HusseinHolland

[HusseinHolland]

I asked about the high/low ohm injector combination issue on one of the Volvo forums, as this applies to some early Volvo LH systems.

One of the members had this to say:

"sorry, you don't want to do that. If you use high impedance injectors with a resistor pack, it roughly doubles the resistance. This means the current flow through an injector is ~1/2, which results in ~1/4 the opening force on the injector pintel. This can cause slow injector opening and/or the injector not fully opening."

Another gave more detailed response:

"Your injectors are clearly opening; but, the injector offset (which some people refer to as injector opening time) is affected by the injector operating voltage which is now much lower than design. When you reduce the injector voltage the offset increases and the actual injector pulse width is reduced compared to the commanded pulse width. At wide open throttle or close to wide open throttle where the commanded pulse widths are large the error caused by the increased offset may be less significant although the engine will run with a slightly leaner fuel mixture. At idle and low engine load where the injector is operating with small pulse widths it will have a larger % effect on the actual pulse width. At worst, if the reduced pulse width intersects with the injectors non linear region you can cause extremely unstable idle. At best, the reduced pulse width will result in a leaner than ideal fuel mixture at idle and low engine loads."

and

"I assume that 205CC means 205 ml/min flow rate for the injectors. If so, that is not a particularly large injector which means that your idle pulse widths are fairly large and probably well out of the non linear region which means the increase in injector offset may have a less significant effect. So, the car may still operate right now; however, if you ever have to do a cold start on a cold day with a compromised battery you may run into a no start condition. The reduced battery voltage may result in a complete injector non opening condition at worst or really difficult starting"

finally

"The good news is that this should be easy to correct. This may be as simple as just deleting / by-passing the original injector resistors. What you need to do is measure the resistance of the original injector and the injector resistor. Add the values together. The 0280 155 712 injector appears to be really high resistance - 16 ohms. As long as the added value of the original injector and injector resistor is less than the resistance of the new 0280 155 712 injector it is 'safe' to just delete / by-pass the injector resistor. I suspect that this will be the case because most low impedance injectors were around 2-3 ohms with external injector resistors in the 5 - 10 ohm range so a total resistance in the 7 - 13 ohm range."

 

I'm going to go ahead and bypass the resistor pack, after I measure the values.

Edited November 18, 2023 by HusseinHolland

[Zed Head]

You can find the same discussions on Hybridz.org.  You're in that theory versus practice conundrum zone.  The theory can be correct, but not matter in practice.

[HusseinHolland]

Took a number of resistance measurements today

lead resistance .3ohm

harness resistance, with ballast 17.1ohm (all the same)

Injector resistance - All 15.6ohm

stock injectors 1.9-2.0ohm

Ballast pack - very clean terminals

4.8-4.9ohm

Harness resistance with Ballast pack bypassed 7.6ohm

2 bypass plugs to maintain the integrity of the original harness.

4pole (3 wire)

sleeved with heat shrink to approximate stock boot

6pole (5 wire)

 

Edited November 19, 2023 by HusseinHolland

[HusseinHolland]

Warm idle, AFR's are now steady 14.7-14.8, with the pot set back at .8 (800ohm). The last few days, I had to enriched the pot value to 1, 1.1 1k-1100ohm) to get the AFR back down form 16.3-16.7

YouTube Vid

EDIT - test driving under varied conditions, including WOT - AFR's are good across the board, until I go WOT, then it's way too rich (high 10's-11), so I reset the WOT TPS contact so it's not in effect until 70-75%

YouTube Vid

 

Edited November 19, 2023 by HusseinHolland

[Captain Obvious]

The AFR numbers look good. I'm no engine tuner, but I don't think 10-11 at WOT is that bad. Maybe a tad rich, but you usually want it rich at WOT, don't you?

As for the resistance measurements, most of them look good. The two where you are sticking the probes into an empty injector socket (to measure back into the harness) really don't tell you much though. You're just reading a combination of ballast resistors and injector resistances in series parallel combination. Didn't hurt anything, but really no good data to be gleaned from that.

If you're not sure what I mean... here's a pic that highlights the situation. You're just measuring a couple injectors and their dropping resistors in parallel, etc. 

In theory, if you're measuring back into the harness with the key off, you should read open circuit. But you would have to disconnect all the injectors (or at least the correct three) to see that. if you crank the meter up to the 2 MegOhm range. you might be able to pick up the leakage current through one of the output transistors in the ECU, but that's about it.

So for the rest of the resistance measurements... You measured the ballast resistors at 5 Ohms and the injectors at 15.5 Ohms. Those measurements look great. Let me think about those numbers a little.

In the end, if your AFR's are good, all that theory by the Volvo folks doesn't really matter. Might be applicable, might not. But your AFR's are on target, so who's to say there's a problem?  

[HusseinHolland]

17 minutes ago, Captain Obvious said:

The AFR numbers look good. I'm no engine tuner, but I don't think 10-11 at WOT is that bad. Maybe a tad rich, but you usually want it rich at WOT, don't you?

As for the resistance measurements, most of them look good. The two where you are sticking the probes into an empty injector socket (to measure back into the harness) really don't tell you much though. You're just reading a combination of ballast resistors and injector resistances in series parallel combination. Didn't hurt anything, but really no good data to be gleaned from that.

If you're not sure what I mean... here's a pic that highlights the situation. You're just measuring a couple injectors and their dropping resistors in parallel, etc. 
 

In theory, if you're measuring back into the harness with the key off, you should read open circuit. But you would have to disconnect all the injectors (or at least the correct three) to see that. if you crank the meter up to the 2 MegOhm range. you might be able to pick up the leakage current through one of the output transistors in the ECU, but that's about it.

So for the rest of the resistance measurements... You measured the ballast resistors at 5 Ohms and the injectors at 15.5 Ohms. Those measurements look great. Let me think about those numbers a little.

In the end, if your AFR's are good, all that theory by the Volvo folks doesn't really matter. Might be applicable, might not. But your AFR's are on target, so who's to say there's a problem?  

10-11 is just dumping gas. Even with a high pressure Turbo, you really don't want much under 12 for good power.

I was mainly checking that I had uniform values at all the injector sockets, since they all originate from those 2 wires that feed the ballast.

Just to be clear - the AFR's weren't on target with the ballast in place - I had the lean condition at warm idle, and some unevenness under load conditions. It did feel better than the stock injectors, but now it feels really smooth by comparison, so I'd say removing the ballast is wise with high impedance injectors.

[Captain Obvious]

30 minutes ago, HusseinHolland said:

the AFR's weren't on target with the ballast in place - I had the lean condition at warm idle, and some unevenness under load conditions. It did feel better than the stock injectors, but now it feels really smooth by comparison, so I'd say removing the ballast is wise with high impedance injectors.

Excellent. With newer injectors so much easier to find than the old ones, it's great to figure out alternative!