I replaced my injectors a couple months ago because I had two go bad. As I mentioned in some other threads back then I swapped in a fuel rail full of Nissan injectors, but they were red top. They still had the rectangular shape like the original pink top ones for my '89, but it seems that they were from a VG30ET engine. Well, long story short, they worked to get the car running, but now my MPG is crap (about 220 miles on my first full tank) and it seems that I am having some problems from running rich (shuddering, strong fumes, bad mpg...).

Does anyone know what is the CC output for the original VG30E injectors? I think I read somewhere that they are 168cc or something like that, and a guy who works at a specialty Nissan shop around here where they work on a lot of older Z's said he thinks the turbo injectors are about 222cc's. Besides the bad fuel economy there is a slight shuddering problem that seems to happen when the throttle is just starting to open. I assume that must be from the combustion chamber getting flooded from too much fuel. Do you think that is right? When I gas it, though, there seems to be plenty of juice to get the car moving. It's been so long I don't what it was like before, but now at 2500 rpms it is getting up to about 70-75mph and 3k takes it up to 90mph+. Is that normal?

So, it seems I either have to go back to stock injectors or find some way of tuning my fuel management setup. Any suggestions? Would adjusting my timing help?

Thanks in advance.

-Mrkanda

 

If the flow rate of the injectors you are using are higher than stock, then you have 2 options. Replace them with the correct injectors, or use something like this http://www.nistune.com/ to adjust the injector constant in your ECU.
Messing with the timing won't help correct for a rich mixture.

Personally I would go back to stock injectors. Larger injectors are less accurate when small amounts of fuel are required, so your idle may suffer even if you modify your ECU to suit. And if your engine doesn't need more fuel than stock, there is no advantage with larger injectors.

 

+1

 

I do plan on running boost in the car later, but that may not be for a year or more. So, probably I will just go back to stock injectors (used for now )

Any idea if the RPM/Speed range I mentioned is within spec?

 

i don't know what rpm vs speed has to do with anything... that's a function of your transmission, not your fuel system

anyhow stock inectors are 180cc. feel lucky you only had 222cc... i have 259cc and will be replacing the engine (AGAIN) because of potential lubrication issues that were caused by the rich condition.

 

Before, I don't remember getting so much speed out of my engine at such a lower rpm range. My wife's Mazda hardly does 65 at 3k rpms.

Anyway Caped, why do you have larger injectors? Did they come from a Z32 or something? And do you have that shuddering feel at low throttle because of the un-tuned larger injectors?

 

on my vg5, that is about what my speedo/tach read.

 

It looks, from the Nistune website, that the board for our cars (type 1) is only about $160 USD plus about $25 registered shipping from Australia. Is that right? If so, maybe that's easier route than swapping out injectors.

Who on here is running Nistune with an N/A VG Maxima? What are the gains?

 

eh, regardless, it's just mental. there is no way that using the wrong fuel injectors is gonna change what speed vs rpm you run when locked up in OD.

i have VE/VQ inectors cuz they're more reliable...... but apparently at a cost if they're on the wrong engine. I mean they work just fine on a VE or a 4th gen at low speeds and all... but you'd have to tune them properly for the VG. It can certainly be done; they aren't THAT big compared to, say, z32tt injectors (which also work fine on a 3.0 liter V6 at idle) that are 370cc... but all i have is an adjustible potentiometer on my MAF signal wire to crutely reduce the aout of fuel the ECU thinks the engine needs... but without a wideband i have no idea what AFR i'm actually running. based on narrowband readouts, it appears that the resistor is causing the reaponse to be non-linear compared to an un-resistorized signal (gets richer at higher rpms and leaner at low rpms)

 

gearing is different on all 4 3rd gen transmissions.... no legitimate comparison can be made between any un-like trans.

 

You will also need a software license ($160) and the chip installed ($32). Still, I highly encourage you to get NIStune so you can learn about tuning and see all thats going on inside your ECU/engine. Even while NA, you can tune for maximum power and/or fuel economy.

 

that is 100% a function of gearing.
my old 79 camaro was doing 120mph @ 3500 rpm
this POS accord does 65@3500 rpm or so
my minivan does 55@ <2000 rpm

you may be getting more "speed" because you are running right and that is how it feels.

 

it's possible that if his car is down on power that he's having to press the pedal more, which might keep lockup from working, and thus running higher revs.

 

true, anything is possible when it comes to cars.

 

Do you have a cel? You said you swapped out your fuel rail for one full of nissan injectors. What year maxima did you obtain the injectors from? Did you have to wire in pigtails for the newer style 93-94 gxe sohc injectors? Sound like one of two senerio's, Either you have injectors from a ve30 or possibly a vq30 i think those are the only injectors that are red at the connectors (maybe z32) but not sure. Or the injectors you put in may have a leaky o-ring at the nozzle leaking fuel in the combustion chamber after pulse from the ecu cycle. The vg30et like found in the z31 use a totally different fuel injector than ones used in the 3rd gen maxima fuel is supplied through the top instead of the sitting in the fuel rail. i dunno if this helps but i had these experiences with my max. 410 miles to a full tank with 301,000k on the odometer and burns about a 1 to 1 1/2 quarts of oil between oil changes.