Injector Duty And Timing

[T.D]

Just wondering, I have an interesting problem which hopefully someone can shed some light on.

I've got some JDM S15 injectors (440cc or 480cc, depending who you ask lol) in my S2 R33 GTS-t which used to make 263rwkw @ 18psi (Injector duty ~93%), and around 14-degrees of timing up top.

My car now only makes ~220rwkw @ 18psi (Injector duty ~98%), and around 8-degrees of timing up top. Any more timing and the motor will just knock dangerously, verified by both hand controller and headphones.

Had a very reputable mechanic go over the car and found no leaks (other than a small leak from the idle screw), fuel pressure is good (had a working fuel pressure test done, but not a flow test), fuel filter replaced (old one was completely clogged) and compression results came out good. Car idles perfectly and feels smooth.

So, the question is: are my injectors stuffed, seeing as the car is making less power but injector duty has increased?

[MrStabby]

I'd say you're making less power because of the reduced timing, so the question is why is it knocking now in a way it didn't before.

Are you running the same fuel? Is the AFR the same on both runs?

[T.D]

I'd say you're making less power because of the reduced timing, so the question is why is it knocking now in a way it didn't before.

Are you running the same fuel? Is the AFR the same on both runs?

Yeah, we're down on power because of the timing and as to why it's knocking, that's what we're trying to find out as we can't figure out why it's knocking now. That's why I'm wondering if it's possible that one (or more) injector is getting lazy or is clogged from the dirty fuel filter enough for it to be running overly lean in one cylinder.

Yep, same fuel (BP 98 Ultimate) and AFRs are the same still.

Any ideas?

[(OO)Firty Free(OO)]

have you checked the fuel rail pressure. could be a dying fuel pump

[T.D]

have you checked the fuel rail pressure. could be a dying fuel pump

We did a on-load fuel pressure test, which came up good. The pump is a Bosch 040 and was put in less than 6 months ago

[Lithium]

What has changed in between? You obviously decided to do some kind of re-tuning at some point seeing the injector duty cycle has changed.

What ECU are you running? And where do you experience knock?

[T.D]

What has changed in between? You obviously decided to do some kind of re-tuning at some point seeing the injector duty cycle has changed.

What ECU are you running? And where do you experience knock?

For the full story, I'll have to go back to day one of the problems so bear with me here LOL

Basically, when I had my PFC first tuned (263rwkw) the car was great and knock never went past 18 when giving it a boot.

Then one day, out of the blue, a quick boot saw knock rise up to 126. Thinking it was a "phantom" noise that set it off, I didn't think too much of it.

Few days later, another quick boot saw knock at 93. Since I had my car booked in for a tune in a couple of weeks, I took it easy until then.

One week prior to the tune (I planned this all in advance by the way), I installed my Plazmaman plenum and Hdi intercooler and went in for my tune the following week.

And that's when we found timing issues and the car won't make power.

It should also be noted that around the time that the first big knock appeared, I had removed the charcoal cannister but I'm pretty certain I plugged up the lines correctly. Eitherway, all throttle body and manifold lines that used the cannister were plugged up, leaving just the hardlines from the tank and the ones venting.

[T.D]

Oh forgot to mention, knock usually occurs in the upper RPM range. At first we thought it was a VCT issue as that's when the knock starts becoming very unstable but we've ruled out the VCT by running it both plugged and unplugged.

Also worth mentioning that the fuel rail around cylinder 4,5 and 6 has gone from the factory greeny-metallic colour to a heated titanium sort or bluey-rainbow colour.

[MrStabby]

Also worth mentioning that the fuel rail around cylinder 4,5 and 6 has gone from the factory greeny-metallic colour to a heated titanium sort or bluey-rainbow colour.

Weird. It would be nice to know if is a different temperature on that end. I'm guessing it will to cool enough to touch to check....

Cooling system properly bled?

Re: fuel pressure, if there was a problem with that you would have seen lean AFRs under load, so I think that's highly unlikely.

Might be worth pulling the new cooler to inspect for any blockages.

[T.D]

Yeah, I'm gonna have a check to see if there's a differentiable difference in temp of the rail.

Cooling system is bled properly and even dropped the coolant before putting fresh stuff in so not a cooling issue.

Yeah, we don't think it's a fuel pressure issue but more so a fuel flow issue (dodgy injector?) as even if one or two of the injectors are getting lazy, it wouldn't affect the overall AFR as it's measured from the exhaust the two tuners told me.

There's no blockages in the cooler but I am contemplating trying a different cooler and see if it makes a difference. I wouldn't think so though as it seems to be cooling pretty well, using a laser temp sensor.

[T.D]

BUMP?

Anyone know what it means if power is down but injectory duty is up? Is it a sign of injectors playing up?

[Don Dada]

How do the plugs look? Is the color consistent across all?

[MrStabby]

There's no blockages in the cooler but I am contemplating trying a different cooler and see if it makes a difference. I wouldn't think so though as it seems to be cooling pretty well, using a laser temp sensor.

You can only know for sure that there are no blockages if you've measured the pressure either side. That said, it's pretty unlikely unless someone left a rag in the intake piping somewhere during the install....

Considering that you just changed stuff, it would be a co-incidence if something else went bad at the same time (ie injectors) so I'd focus on the new and weird stuff first, so;

- verify if the fuel rail temperature is normal

- swap out the intercooler

Also, do the spark plugs look normal? If you do have an injector problem you should see some inconsistency in the colour.

[Adriano]

Is there any chance the boost has crept up? Could explain the knocking, reduced timing and the duty cycle

[Torques]

What A/F ratio are you running at WOT?

Just wondering, I have an interesting problem which hopefully someone can shed some light on.

I've got some JDM S15 injectors (440cc or 480cc, depending who you ask lol) in my S2 R33 GTS-t which used to make 263rwkw @ 18psi (Injector duty ~93%), and around 14-degrees of timing up top.

My car now only makes ~220rwkw @ 18psi (Injector duty ~98%), and around 8-degrees of timing up top. Any more timing and the motor will just knock dangerously, verified by both hand controller and headphones.

Had a very reputable mechanic go over the car and found no leaks (other than a small leak from the idle screw), fuel pressure is good (had a working fuel pressure test done, but not a flow test), fuel filter replaced (old one was completely clogged) and compression results came out good. Car idles perfectly and feels smooth.

So, the question is: are my injectors stuffed, seeing as the car is making less power but injector duty has increased?

[Guilt-Toy]

check your cat. its possible it could be blocked or its falling appart

[The Mafia]

whent he injector duty cycle is maxing out and you're making less power, it usually means the car is starving for fuel. Did you hook the fuel lines up the right way? Sound stupid but you need to check everything.

- Get the injectors professionall cleaned, having a clogged filter means shit when through them

- What AFRs are you running?

- Drop the exhaust just before the cat

- Check the plugs, look for colour differences

- Borescope inside plenum, look in each runner

- Check fuel flow, not pressure

[T.D]

Thanks for all the replies guys

How do the plugs look? Is the color consistent across all?

Plugs are all fairly consistent and according to the mechanics, nothing out of the ordinary.

You can only know for sure that there are no blockages if you've measured the pressure either side. That said, it's pretty unlikely unless someone left a rag in the intake piping somewhere during the install....

Considering that you just changed stuff, it would be a co-incidence if something else went bad at the same time (ie injectors) so I'd focus on the new and weird stuff first, so;

- verify if the fuel rail temperature is normal

- swap out the intercooler

Also, do the spark plugs look normal? If you do have an injector problem you should see some inconsistency in the colour.

No blockages, I've pulled it all apart a few times now as I thought it was a boost leak so alll is good on that front. Spark plugs seem pretty uniform in terms of colour

Is there any chance the boost has crept up? Could explain the knocking, reduced timing and the duty cycle

Boost has crept up 1.5psi, but both tuners/mechanics have dismissed that as the problem, due to the fact the amount of timing they have to back off in order for it to not knock (8-degrees as opposed to 14-degrees).

What A/F ratio are you running at WOT?

Can't remember off the top of my head but from what both tuners have told me, it's still fine. However, they also mentioned that if it's just one cylinder running elan, it won't come up on the AFR as it's measured from the tailpipe.

check your cat. its possible it could be blocked or its falling appart

Exhaust has been dropped and checked. Had a pressure gauge hooked up to it and the exhaust produces less the 1psi of restriction hehe

whent he injector duty cycle is maxing out and you're making less power, it usually means the car is starving for fuel. Did you hook the fuel lines up the right way? Sound stupid but you need to check everything.

- Get the injectors professionall cleaned, having a clogged filter means shit when through them

- What AFRs are you running?

- Drop the exhaust just before the cat

- Check the plugs, look for colour differences

- Borescope inside plenum, look in each runner

- Check fuel flow, not pressure

Yeah, fuel lines are all connected up correct. When I did the plenum change, I only had to replace the FPR pressure hose onto the new plenum.

I had the injectors cleaned and tested around 5 months ago (brought them second hand).

How do I check for fuel flow? Is there a test I can do or my tuner can?

[Lithium]

How does the dyno plot look? If you look at your datalogs, how does the rpm signal look?

[STATUS]

How does the dyno plot look? If you look at your datalogs, how does the rpm signal look?

unfortunately with nissans the rpm signal is rock steady even with a knackered cas had a few cars log perfect but would not push past 190rwkw, swapped cas and cars pulled mid 300's .

Already has had another Cas tried in this car from memory.

I could not sort it before plenum and cooler it tuned up fine, after mods it would not take any timing.