Hey guyz, The time has come for a bit of a power upgrade/tune refinement where this time using 550cc injectors instead of the stock 370cc. What do you guys know about JECS yellow top 550cc? or JECS in general, other than being the OEM manufacturer for Nissan and I'm sure other brands too. A set of the 'new style' are now installed in my Z and the car idles and revs 'smooth as' with a 'base tune for 555's' just to allow the car to start and check for any issues prior to a proper tune. What baffles me though, is that I've been informed that JECS 550's are just normal injectors re-drilled to make them Hi-Flow. I thought... really? Z1 sell JECS as genuine new units of various flow rates here: https://www.z1motorsports.com/fuel-system/jecs/jecs-high-performance-fuel-injectors-p-4293.html so... what's going on? Also, I don't have latency times etc... the rough tune in the car currently is setup for 555's as mentioned earlier. Will the correct/appropriate latency/duration be determined during the tuning process? I'm asking this because I'm wondering... is the 555's injector values entered as a constant on Nistune or will they be adjusted during the tuning process based on air/flow ratios or whatever other data? What do you guys think?
While it is helpful to have the injector data, it isn't the end of the world. And 555 injectors aren't large enough to cause too many issues. Tuner will sort it out. More importantly, did you have them flowed before installed?
I did some digging around last night into this issue and NISMO do sell NEW proper 550cc and so does TOMEI. They are identical, JECS. I've also discovered, that some tight asses, have drilled the OEM injectors to make them 'high-flow' with shit workmanship & therefore results in terms of flow & spray pattern. I looked at some examples and OMG... cringe.
The new style yellow top nismo injectors are 615cc, if you have a S1 engine you'll need rails also, no big deal. I'm sure you know czp or z1 do a kit, rails with injectors and connectors if you need them.
Got the new style injectors with adaptors and wiring to suit S1 plenum. Plug and play, its perfect. Identical to the Z1: https://www.z1motorsports.com/fuel-...-style-injectors-early-fuel-rails-p-3348.html The original 28YO injectors were so brittle. They just fell apart while removing them. WOW.
That's to be expected. The plastic caps covering the injector tips are pretty much rooted after 15 years, let alone leaving them in there for 28 years! I'm impressed they haven't turned to little crumbs yet.
A little more about injectors, had mine flow tested, the tests were carried out @3 bar of pressure, all injectors flowed pretty much the same @ 540cc, good.. problem is the injectors are nismo 615. I questioned why the drop in flow, and they (aznew)said It was possible they were flow tested @4 bar, which was a common way to bump up the flow rating of the injectors. They gave an example of a brand name injector that was claimed to flow 1130cc but in actual fact was flowed closer to 900cc at 3 bar. It would seem 555-615 flow the same cc, with the 615 having a different spray pattern and connector.
This is true. The Bosch EV14K I run in the 13B have 2 ratings. When you buy them some places quote them as 2200CC but that's at 60 PSI (4 bar). At 45PSI (3 bar) they flow 2000CC. Most aftermarket fuel pressure regs will allow 60 psi so it's only the factory regulators that can't drive the injectors to their max rating.
While researching the net about Nismo 550's I found out that they are also referred to as 615cc. Interesting and confusing at the same time. I reckon anyone getting second hand injectors has to ask the supplier to ensure they are 'NOT DRILLED'. My personal opinion is as long as they are flow matched with consistent good spray pattern I don't see an issue. Yes, the 28YO injectors were well and truly stuck in there! Needed a crow bar to get them out. By the way, the lag time for Nismo/Tomei/JECS 550's/555/615/whatever... is 0.71 (seconds) Source: https://www.rhdjapan.com/tomei-fuel-injectors-set-555cc-rb25det-c34-ecr33-wgnc34-vg30de.html
While the plenum was out, I cleaned the AICV... refer below... https://www.z1motorsports.com/idle-...air-control-valve-iaa-iacv-new-oe-p-1751.html removed and cleaned all solenoids. Check resistances and applied pawah and they click OK. I also removed the idle screw completely and found it has a specific 'O' ring on it. Upon removal, I noticed the O-ring got somewhat chewed up by the threads. I put the screw back in and took my chances re-fitting the AICV unit. Started the car and idles at 1000rpm. Oh no.... vacuum leak. I screwed the screw in as tight as possible to drop the revs and 'nothing'. I think I screwed the screw! and it has formed a vacuum leak. I should have left it. I have a new AICV unit coming but would it be fair to say, don't screw with the AICV idle screw? as in, DON'T REMOVE IT? Has anyone had any 1st hand experiences with these AICVs?
The idle screw on my car had some of the thread covered in some kind of rubber shrink wrap. I didn't notice an on ring on either of the two valves I have, both had the rubber stuff on the screws .
That's the rubber I'm referring to. I call it an o-ring. Upon removal, I could see pieces of it coming out as in being chewed up by the threads. Tried to fit a normal O-ring in it's place but eventually the screw just goes through it. Something tells me this screw is not meant to be completely removed, but I could be wrong and maybe there's some other vacuum leak somewhere but stuffed if I know where it is. I've checked all hoses around the plenum. One step at a time, in the process of elimination. I guess I can always spray some WD40 on that, while the car is running, and see if it has any effect on the idle or block the hole altogether temporarily. Something to try out tonight!
Butane is the go for vac leaks, the stuff in a throw away can with the long nozzle is the one. Put a few wraps of Teflon tape on the idle screw, it works fine.
