Replacement Fuel Injectors for 3.2's - Why's it so hard?

Why's this so hard? Well, it doesn't help that these cars are now around 30 years old and the standard Bosch 0280 150 158 injectors haven't been manufactured for well over a decade. Sure, you could buy NOS replacements in drips and drabs off eBay at around $360USD each! Or you can buy generic 24lb/hr "158" low impedance style replacements made in China for about 80 bucks each from AFI. Or you could do what I did with my last 3.2 and just get them cleaned and have new caps, screens and o-rings installed for about $130 a set.  But surely at 25 years the insulation on the windings and the pintels have got to be near the end of their life.  And they weren't that sophisticated to start with even when new. With my latest 3.2 suffering a leaky injector I thought do I really want to continue to run these old injectors, particularly since technology has come along in leaps and bounds and surely there has to be alternatives? Searching through Pelican and Rennlist wasn't much help as most people were recommending 0280 150 360's and 364's as a substitute but they are also almost impossible to source like the 158's and a barely a step forward in the evolutionary ladder anyway!  There were a few other part numbers suggested but not a whole lot of evidence provided to support these suggestions. Then I recall one of the more vocal independent workshops posting about 18 months ago that they use modern 4 hole injectors as replacements for their customer's cars. Unfortunately I couldn't get them to spill the beans on the part number.   I admit I was disappointed but appreciate that they took the time to post as it did open my eyes to existence of alternatives. It also confirmed my thoughts that it was possible to safely run a high impedance injector (12ish ohms) with our Motronics in place of the low impedance (3ish ohms) standard injectors Anyway, after nights of research I bought a set of 0280 155 931's The Motronic gives some leeway with the fuel/air ratio by providing a switch that allows you to choose a fuel correction  of -3.9%, 0%, +3.1% & +6.3% that gave me some comfort that I could use this to give some element of tuning to match these new injectors to my engine. BTW: My 88' is the 217hp version that has a Steve Wong chip, cat delete and M&K muffler which is probably the same to many out there. After driving it and then resetting the Fuel Quality Switch to +6.3% I was very happy with the results of my $129 worth of new injectors.  Lovely idle, willing part throttle and smooth and revvy WOT. However the bum dyno is infamously inaccurate and I wondered how my air fuel ratio would stack up, particularly at WOT on a dyno with a lambda probe? Edited 2June, 2017 by Peter M

That's what you get for owning a modern 911

Turned up at the dyno tuner this morning. He doesn't know me and I don't know him.  It's cold and there isn't much chit chat.  His bread and butter is obviously WRX's and XR6 turbos.  I just say I've changed the injectors and just want to check the a/f ratio is OK at WOT. Oh, and sorry it might be a bit smoky on overrun as the valve guides are worn. He takes the car and his offsider straps it down ready for a run. He does a bit of part throttle loading and two WOT runs.  All over in about a minute.  The M&K sounds magnificent I think to myself. He shuts it down and bounds over with a spring in his step and is very animated. Lovely car, WOT perfect, part throttle perfect, idle perfect, wouldn't change a thing, you've done a good job he says.  Tune is safe and fuelling is where you want it on a street car he continues. Talks about the A/F being right for best torque but part throttle is right for best mileage as well.  Torque curve is nice too. And not smoky at all.  He is talking a bit fast for me to take it all in.  I smile in relief and then realise he thinks I know what I'm doing! I joke the power is pretty modest but pulls he me up with "they're only a light car". After a bit more chit chat, a few photos for his Facebook page, I pay my 88 dollars and I'm on my way in less than an hour.  Relieved that I don't have to look at any more Bosch part numbers, flow data or bloody forum posts. http://i1315.photobucket.com/albums/t598/PeterM00001/Dyno%20run%2010617_zpspga46nlh.jpg

For the Newcastle guys I used: https://www.facebook.com/NewcastleDynoCentre/ He got those photos up pretty quickly! Edited 1June, 2017 by Peter M

Yep the newer Bosch stuff like the EV14 series of injectors are very very good. As you say it is just a matter of finding the best replacement. Looking at the Lambda graph It looks like a very safe tune that on OEM would do. I.e to rich. For a pre CAT converter car best cruise economy is around 1.05 to 1.10. For a NA engine best torque /power will be around 0.9 say 0.85 to for a bit of margin. 0.70 is the domain of high boost turbos to help with detonation and charge cooling. If the dyno shows more power at this very rich mixture then there is a problem with the dyno repeatability or the lambda measurement. It is also suspicious that there is such a difference in the lambda from the two runs assuming nothing was changed between the two runs. One  difference between the old and new injectors will be the dead time compensation. With the newer ones generally having a lower number. This differance will show up most at lower pulse width and have least influence at full throttle. There should also be big improvements in atomization of the fuel with the 4 hole compared the the old pintel/cone injector.

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Red, He suggested the difference in the lambda was the result in the change in engine temp between run one and two.  The second run is the red trace.  He didn't recommend leaning it back to the next increment at all even though I had the ECU out on the floor and likely to be only a 15 second task. I suspect because it's air cooled and has no knock sensor protection. Edited 1June, 2017 by Peter M

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There will be some enrichment in these older ecu as the engine warms and becomes less air mass flow efficient but what you have is more than I would expect and the fact it makes more power at the richer mixtures is a concern but could be explained by internal losses in a cold engine being higher than a warm engine and greater than the power loss due to being richer than 0.90 lambda. Hindsight is great but a 3rd run would have been very informative as well as knowing the oil temp for rach run. What you have is a very safe tune which is fine for road use. Enjoy the benifits of the updated injectors it is a worthwhile update that any classic should look at. FYI I run my EVO X at 0.74 Lambda at 26psi boost.

Ha! Nathan aka Ned the owner is a very good mate of mine. If Ned thinks you have a good car. You have a good car. He is the only person in Newcastle who works on my cars other than me. P.S I’ve prolly got a couple spare sets of these injectors in the bottom of my toolbox if you want them.

Hah!  Martin, your ears must have been burning this morning as you did get a mention or two! Thank you for the offer but if these new injectors last as long as the original ones I'm OK until they take my licence away. Actually reread your great thread on the blue car a few days ago.

I’ve been thinking about contacting the current owner of the blue car to see if he wants to sell it back lol.

And to think I seriously considered buying the blue car...before it went to the big island to be radicalised...

I've done around 2000km on these new injectors and couldn't be happier.  Over the weekend it spent 3 nights in the open in Armidale and each morning at 5 to 10 degrees C would start easily and idle perfectly steady from the get go. Following on from Red's comments above and another reason why everyone errs on the side richness at WOT besides protecting from destructive expensive detonation and aiding cooling, this protection comes at little cost to power: Edited 26June, 2017 by Peter M

i think I have just traced my hot start problem back to a leaky injector. Now I'm beginning my search, as Peter did, for some new injectors that won't break the bank. Peter, can you recall this part no. 280 150 786? It's a 3L running a 3.2L fuel system. Any advice where to start looking?

280 150 786?  They're the standard injectors in 993's? I thought about using those but I considered if I was going to try something different I wanted the modern style 4 hole pintel rather than the old style centre needle and went for 0280 155 931's Is the car running a standard 3.2 Motronic with aftermarket chip?  Does it have an oxygen sensor?

I have some standard 964 injectors if they are of any use to you?

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993, that's interesting. It's got a 3.2 inlet manifold and running an Autronic computer. I think from memory it does have an oxygen sensor, but would need to double check. The car runs great and I really don't want to mess with it, so hoping to find the same injectors. Thanks, Mick are they the same part number?

Mick, Given your comments I suggest you just get the ones you have ultrasonically cleaned and tested (about 20 bucks each and about a week turnaround) as buying a new set of 786's is eye wateringly expensive and using anything else will involve some study, some gumption and a dyno run to confirm fuelling is all well.

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ok, good advice. Will give that a go first. Thanks Peter

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So looks like a happy ending with my injector issues. I sent them off for cleaning / testing and got some bad news that 2 were stuffed. But that was quickly followed up by 'we can supply new ones for $75 each'. I was a bit sceptical about the price but they assured me the new ones, even though they were a different part number, sprayed exactly the same. anyway, I just fitted them and the car now runs perfectly with no tweaking, plus a touch more power. Big smiles all round. Thanks everyone for your input

Not really on this topic, however has anybody purchased and is using one of those newer type solid state DME's? PS: I'm new to this site, so excuse me if I asked a different question not related to this topic. I have a 89 3.2 and 2007 997S

DME Relay? I think most people just carry a spare conventional replacement in their glove-box, just in case as you can probably buy 2 or 3 standard types for the price of a solid state one.  I also understand that the cracked solder joints - that causes the vast majority of failures - can be repaired pretty easily too.

The maker of these solid state DME's will not sell them outside of USA. I have 2 on order (for late 911 & 993) via a friend, & should get them soon for testing. I will report back then.

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Thanks, I would be most interested in knowing of the prognoses on these solid state units. I have a few acquaintances in the US, so I may do the same. In any case, I appreciate yours and Peter M's feedback.

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Did you get a sneak peek at the part number for those new injectors at $75 each? That would be helpful.

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hi Peter did you change injectors when going up to 3.4 litres? mike

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Yes, to another set that I had on hand at the time.  They are actually higher flow than ideal (max actual duty cycle around 60% according to my data logging) so wouldn't normally recommend these larger ones for a naturally aspirated 3.4 engine at all. Currently I'm running a set of 0280 155 868's (261g/min @ 3 Bar N-Heptane).  In hindsight the 0280 155 931's (187g/min) recommended in this thread  would have coped fine with the bigger engine  capacity as 60% of 261g/min is only 156g/min. (Interesting! I've never done this calculation before today! According to Greg Banish's recommendations I should aim for about a 20% overcapacity in flow rate or 187g/min which matches the 931's perfectly!) After saying all this the Motec manages the oversize 868's fine so the practice doesn't always reflect the theory fortunately.  The engine actually runs so well that I've never been tempted to change the injectors even though it only involves an easy couple minute update of characterisation data in the tune software. Irrespective of my sloppy injector sizing practices, I still recommend these modern multi-hole injectors over the old tech ones any day.  Plus they are relatively inexpensive and very available as the two models referenced here for example are widely used in Holden engines. For a turbo'ed street version of my 3.4, you could proportionally increase my calculated  injector flow rate to get a pretty sound indicative size based on my requirement of 187g/min being required for a MAP of 84kPa.  ie For a 0.5 Bar increase in intake manifold pressure (ie.to 134kPa absolute), the injector would need to increase to around 134/84 x 187 = 299g/min. (Note my WOT MAP of 84kPa is lower than most because my data logging has been done at around 1100m elevation but this reduction is safely covered by the 20% buffer in the injector sizing calcs.)

I've had this thread bookmarked for awhile... I have an '88 with Steve Wong chip as well, though my exhaust is all stock. As far as I know the injectors have never been serviced, and the idle has never really been as smooth as I'd like, especially when cold. I'm now debating whether to just send my injectors out for cleaning ($240) or make the jump to the newer injectors Peter used ($450). New injectors are tempting, I'm just a little wary of messing around with fueling when I don't really know what I'm doing.

Jack, The only extra messing around might be a couple clicks on the Fuel Quality switch on the ecu under the passenger's seat.   However, I would still recommend a dyno run to check AFR's are satisfactory.  That's probably not a bad idea as it will confirm the rest of the fuel system is operating satisfactorily as well, particularly the Air Flow Meter that is subject to aging.   So "yes" some extra messing about, I agree. Before I changed my injectors, I had a very unstable cold start where the engine revs would isolate wildly for the first 10 -15 seconds before settling down. Both solutions have their merits.

Thanks Peter! My idle is not that bad, but just doesn't feel as smooth as it seems like it should. A bit rumbly and uncertain, with a bit of vibration. I think I'm going to go the cleaning route first and see how I go. If they are mechanically fine for now and that buys me a couple more years, I think I'll be satisfied with that. If the cleaning guys report bigger problems, maybe I'll go down the route of the replacements you used.

I ended up having mine cleaned. The guy said it did take a bit of cleaning to get them flowing back to spec. but the car continues to run really well.

All that tech stuff beyond my standard knowledge,  But in saying that, Have had injectors cleaned before on other cars, Worked OK for 6 months, But if old I think new is best. 2 c worth

FWIW, I emailed Steve Wong to see what he thinks about this. I was surprised that he isn't offering an updated chip matched to modern injectors, if there is a need for that. He responded that he doesn't think there is anything inherently wrong with the stock injectors, as long as they are clean and working correctly. He definitely thinks having them cleaned and serviced is worthwhile, but otherwise doesn't see a need to replace them just because they are an older design. Just figured I would share that here. I responded and told him about Peter's research and the newer Bosch injector he is using, in case that's ever of any use to Steve.

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He might have got it Wong

Hi Pete and everybody else, I've been researching replacement injectors, as my 3.2 only runs on 5 cylinders after sadly being parked for almost 2 years. Injector signals and spark all tested fine, so I think it's the injector. Are you still recommending the 0280 155 931 for a stock 3.2, or is there a better option nowadays? Do they bolt right in or require any adapters? I'm surprised that nobody else on Pelican or Rennlist seems to have tried them, given their cheap price and that you have recommended them several times since you installed them 9 years ago. Cheers, Lukas

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Hi Lukas, As far as I'm aware, they're the way to go. I'm about to do mine with the part number listed above. For the price, it doesn't make sense for me to send the current ones away.

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Hi Lukas, Have you confirmed which cylinder isn't firing?  You can do that by starting the engine and running it momentarily and then feeling which of the exhaust stubs is cold.  Or you could start it and pull each plug lead in turn while it is running until you find the one that has no effect on the engine speed.  I would then pull that particular plug to see if it is wet with fuel or dry.  If it is wet you have an ignition problem, if it is dry you have a faulty injector or wiring to it.  (Remember 3.2's are batch fired even though the injectors are powered by two separate ECU outputs) I would still recommend the 931's and I still recommend you spend 150 buck for a dyno run to confirm your AFR's.  And, yes they are a direct replacement without having to use adaptors.  Just be aware that some of the "Bosch" branded injectors on eBay may not actually be genuine. As for Pelican, I do get frustrated by their propagation of old wive tales, which I think is unfortunately getting worse as the real practitioners are dying out. My favorites are: You can't replace low impedance injectors with high impedance ones AC upgrades are measured by vent temperatures alone. AC can only be upgraded to R134a You got to run 8" rims on the back There is nothing better than a Wong chip The only benefit to running twin plugs is that it allows compression over 10:1 Anything that references "analog" Fitting a larger throttle body is like fitting a boost button The G50 vs 915 bullshit Being adamant about something but not having any data to back up your assertion. etc