JECS unknown injectors too big?

[antus]

One of my mates owns a 300zx which we have converted to Delco. Its been resting for a while but we have recently pulled it out of moth balls and I have had an opportunity to look at the tune.

We have been able to get the higher load and higher rpm map area pretty sorted, but are having huge issues at idle, which I think are to do with the physical characteristics of the injectors and/or their calibration.

The injectors are ebay injectors mate bought from the states in about 2013. At the time we thought they were genuine 800cc Denso, but being ebay and from around 2013 they could be high flowed in some dodgy way. They did come with a flow sheet (since lost) so assuming that was genuine they should at least have usably similar flow.

I am trying figure out if we should just get rid of these injectors, or need to spend more time getting them figured out (possibly by getting the1 to do some testing and dead time measurements for us).

The car used to have about 8psi of boost, and at full load the injectors were at about 20% duty cycle. Much head room. Idle was never good. In order to enter a different class he has now remove the turbo but we have left the 2 bar in place so that we can boost it again in the future.

I dont really have a good idea of what normal physical limits of injectors are. At idle were seeing BPW of about 0.56ms. Looking at the data in the injector bias vs battery voltage table, at running volts there is 0.46ms bias. Im not sure where this number came from. I think we made it up from spec details of similar style Japanese injectors. Then in injector bias add-on for 0.49 ms we have 0.14. Even at full load were seeing only 2.6ms of BPW.

So what im wondering is if were injecting for 0.56 ms and .49 is coming from one adder table, and .14 is coming from another, does that mean the pcm is looking for < 0.1 ms of fuel delivery? This sounds like a crazy small amount of time to be looking for. Symptoms we are seeing is we take the car and blow come cobwebs out then pull over and it idles ok with the right AFR. Then after it sits for a while the AFRs start jumping all over the place, then it leans right out off the limit of the wideband.

Being that this is a Japanese car which requires side feed injectors, and that the delco requires high impedance there are few options and of the options available injector data is hard to come by.

Should we persist with these injectors and try and improve the quality of the dead time settings or are we up against the physical limits of these garden hose injectors and should be sourcing something smaller?

[Holden202T]

yeah I reckon your definitely going to have a hard time regulating them at such small openings, depending on the actual minimum pw specs, they might not be opening properly at idle, but without the right dead time data its hard to know for sure - I know my 200lb injectors don't do much below 0.5mS

maybe rip them out and setup a test bench at that pw and see what the spray looks like .....

I reckon as a minimum you'd want to get them tested .... but also if you can find a set of smaller injectors that will drop straight in and aren't super costly they are probably going to be the best option for N/A use ..... then you'll have the others there for when you go back to boost.

That said 20% DC at 8psi and full load is pretty low hehe maybe it really needs 50/60lb injectors, or some alcohol fuel

[antus]

Alcohol fuel, thats not a solution i had thought of yet

It seems we have jecs phase 1 rails which are problematic for the subaru phase 2 injectors I got cheap, and no time to get phase 2 adaptors or top mount rails which i think would still need different founts on the manifold side too.

Phase 1 jecs have failing coil problems but its measureable with a multimeter so we can probably confirm what we have is ok. Will try and get maxima injectors i think. Quite small just cheap and easy to get at the wreckers, and high impedance. I had a look at the maxima tune in nistune last nightb it seems they have .75ms dead time @ 14v so if the ones we have now are modified stock the opening times could be .75ms and so if the ecm is trying to inject .2ms of fuel it might be injecting nothing. Def will have a play with dead times on the garden hoses too and see if that can help too.

[delcowizzid]

Turn it onto single fire mode it should run ok

[The1]

sounds like possible case of indy blues, you maybe commanding 1ms but the injector just simply can't control itself that low or with any kind of stability. Im yet to be inspired by anything ive seen in side feed world.

[antus]

Yep, this is in single fire mode for < 2ms. Will play with dead times first and see if that helps.

Im regretting the decision to set this up how we did now, but live n learn. I had no idea how slow and problematic side feeds were, after all they're working fine on my sr20 gem. This engine was built 10 years prior to the S13 and Im getting the impression that Japanese injector tech was behind American and euro back then.

I see why they mostly ran low impedance. With such slow opening times on the first gen stuff being able to sink far more amps in to it to speed them up probably was a good idea until better high impedance design came along.

[The1]

nar top feed was crap still back then to, search indy blue, same issue, getting higher flow rates ment bigger holes but then it couldn't then operate at idle properly, hence one reason the saying dont buy to big of an injector, nowdays it's not a worry the low pulse rate is no problems for the newer tech, you can fit 1000cc injectors in a stock V6 and still idle like stock, but yeh if you can upgrade nowdays do it!

[vlad01]

Jap was way behind the US in EFI in general, by up to about 20 years on average with some of their cars. Subaru is a great example. still using bi-metal thermostatic valve to control idle with engine temps even though there was an electronic IAC but they some how forgot to code it into the ECU? so slapped on a thermostatic on the IAC's ass end lol

Believe it or not, that was mid 90s when they did that, they also didn't go away from the trap door style MAF until the late 90s.

[pman92]

0.5mS does sound very small.

Ive found most OEM stuff is around 2.5mS at idle and 12-14mS at full load (naturally aspirated).

[The1]

he might command 0.5ms but in reality the injector can't do it and may only be capable of 2ms or so, hence it slowly leaning out once it tries to go to low pulse width. It is likely just failing to open when demanded and would give lean or erratic fueling. This is one part of the battery offset pulse in most ecu's to keep the injector in a working range where it works consistanly then also adjust for voltage.