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High Impedance vs. Low Impedance Injectors, why, not what?

I was searching for threads on using high impedance injectors on a low impedance system.

On my 280Z, I added high impedance newer injectors - 0280 155 712. /205cc
I forgot that the car has ballast packs for the stock low impedance pintle style injectors, so I didn't remove or bypass them.
I have driven it this way for the past few days, and can't identify any issues running it this way. Cold & hot starts are good, throttle response is good across the board, AFR's are good. Removing the ballasts will be somewhat of a PITA. Searching isn't coming up with much help. The question is, will running it this way actually compromise the new injectors?
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^^^ 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.
 
As bobxyz notes, not a good idea. It will not compromise the injectors; but, it may compromise engine operation.

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.

With the 1979 280ZX Nissan added O2 sensor feedback. If you have a 1979 or later 280 the O2 feedback may be correcting for some / most of the fuel error caused by the increased offset once it goes into closed loop. However, relying on closed loop control for fundamental fuel control is never a good thing.

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. O2 feedback might correct the fuel mix when the car is running and up to operating temperature; but, it does nothing to correct fuel mixture during the start cycle because your injectors are delivering a lot less than the expected fuel amounts.

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. If it happens that the combination is higher than the 0280 155 712 injector resistance then all you do is have to add in a new power resistor with a resistance that adds up to the original total resistance. Note that this may not be perfect because even with the correct operating voltage for the new injector the offset of the new injectors may still not match the offset of the original injectors.
 
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Thank you for the detailed responses. Mine is a 75 280Z, so no O2 feedback.
I will bypass the resistor packs. The stock injectors are around 3ohms, and the ballast are 6ohm per injector, so about 1/2 the value of the new injector

I haven't driven the car aggressively (no WOT or hard throttle) since the conversion earlier this week, as there were fuel seepage issues that arose with the new rail install.

My Datsun voltage regulator needs to be adjusted as it currently appears to be overcharging most of the time, more so over 2500 rpm - the gauge shows over 15v. That may be why I'm not seeing such a large discrepancy in AFR's. It is definitely leaner at idle once warm.

I'll address it today & get it out of the way.
 
OttoB said:
I never fully understood the idea of low impedance injectors and resistor pack. LH computer is definitely not a Peak and Hold driver. B230 ET Motronic has separate injector amp (Luxor), maybe that is a P&H driver?
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As far as I can recall Volvo only ever used them on the LH2.2 Turbo models. Not sure why. I don't recall the explanation in the Fuel System Design & Function manual. I'll have to see if I still have one that describes the rationale.
 
The original (1968 - 74ish) D jet system was low impedance 2.4 ohm injectors with a 6 ohm injector resistor. That looks remarkably like the Nissan arrangement which should not be a surprise since I think Nissan licensed or outright borrowed the D jet design. If you look at the Nissan 280 Z fuel pump it looks remarkably / exactly like the Bosch 2 port pump on the D jet system. The only difference is the electrical terminal connection. I know because I am running a Nissan pump on my 1971 142E. Pump dropped right in. Same hose sizes and port location and same pump diameter and length. The hose barb style injectors on the first 280Z are also physically identical to the early D jet injectors and are the same injector as used on a bunch of European cars from the '70s to early '80s.

Why Bosch designed the injector with a low resistance and then added an external resistor to limit driver current is a bit of an unknown. The D jet was the first mass produced electronic FI and the coil design in the injector body may have set constraints on the minimum wire size (no substituting smaller wire to get the resistance up). Low impedance injectors with external resistors were very common on Japanese cars. I have an 2000 Acura NSX. The first few years of production Honda used low R injectors with an external injector resistor. Around 1996-1997 they switched to a high R injector. Because it was a low production number car they did not revise the wiring harness. On my car they just inserted a shunting plug where the injector resistor pack used to be connected into the harness.
 
142 guy said:
The original (1968 - 74ish) D jet system was low impedance 2.4 ohm injectors with a 6 ohm injector resistor. That looks remarkably like the Nissan arrangement which should not be a surprise since I think Nissan licensed or outright borrowed the D jet design. If you look at the Nissan 280 Z fuel pump it looks remarkably / exactly like the Bosch 2 port pump on the D jet system. The only difference is the electrical terminal connection. I know because I am running a Nissan pump on my 1971 142E. Pump dropped right in. Same hose sizes and port location and same pump diameter and length. The hose barb style injectors on the first 280Z are also physically identical to the early D jet injectors and are the same injector as used on a bunch of European cars from the '70s to early '80s.

Why Bosch designed the injector with a low resistance and then added an external resistor to limit driver current is a bit of an unknown. The D jet was the first mass produced electronic FI and the coil design in the injector body may have set constraints on the minimum wire size (no substituting smaller wire to get the resistance up). Low impedance injectors with external resistors were very common on Japanese cars. I have an 2000 Acura NSX. The first few years of production Honda used low R injectors with an external injector resistor. Around 1996-1997 they switched to a high R injector. Because it was a low production number car they did not revise the wiring harness. On my car they just inserted a shunting plug where the injector resistor pack used to be connected into the harness.
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Why different car companies opted for permutations of Bosch EFI is always interesting. Datsun used the L-Jet, like some Fiat & Porsche variants (could be others, I just am aware of those), with the Air Flow Meter instead of the older D-Jet MAP or mechanical K-Jet like mid 70's Volvos and others. Fiats' L-Jet uses the same injector design, with the hose & metal rail, but not low impedance. Much mix & matching, it seems.
 
Talking about mix and match. 1989 Volvos had Motronic, K-Jet, L-Jet, LH-Jet 2.2 and 2.4 all on red blocks. And same thing with ignition systems, maybe five different units: Renix, hall distributors (2x) EZK 117and 118.

Then we got PRVs and Renault engines on 400 series. And white blocks coming 1990.
 
lookforjoe said:
Resistance value checks

Idles smoother now with Ballast bypassed.



Glad your 280Z is running smoothly with the new injectors! Running high impedance injectors on a low impedance system, while not ideal, might work short-term. However, it's not recommended for long periods. The ballast resistors may affect injector performance and lifespan. Consider bypassing or removing them for optimal results and injector longevity. If you’re like me, you’re always on the hunt for the ultimate online gaming experience. So, when I decided to try out some new online casinos in the new year of 2023, I was excited but a little overwhelmed. That’s when I stumbled upon the https://bestcasinoplay.com/online-casinos/new-online-casinos/ reviews. BestCasinoPlay’s team of experts carefully reviews over 1000+ Canadian online casinos, giving you detailed insights before committing to anything. It’s been life-saving, saving me from disappointment and guiding me to the best platforms out there. If you’re serious about finding Canada’s best online casinos this year, you’ve come to the right place.
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Edit: I am sorry, my bad, I missed post 25.
 
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Chatbot001 said:
Glad your 280Z is running smoothly with the new injectors! Running high impedance injectors on a low impedance system, while not ideal, might work short-term. However, it's not recommended for long periods. The ballast resistors may affect injector performance and lifespan. Consider bypassing or removing them for optimal results and injector longevity.
Click to expand...
I guess you didn't read all the posts 🙂 I bypassed them back in post 25
 
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