Injector latency - Power Gains?

[rx-line]

I've recently fitted some RC 720cc Injectors and had to do a bit of a re-map on my RB20det. So far things are fine at WOT as per normal. However the idle hunts a bit, but too be expected with 720 low impedance injectors. I have Nistune by the way.

However when adjusting the injector latency I began to think about what the correct latency should be and if there is horsepower (kilowatts for you guys) and reliability (Knock resistance) by having the fuel spray early (which may result in pooling at valve) or late (which could be incomplete burn/ reduced atomization). But when is the factory injection time @ 14v and rated injector impedance?

Perhaps I am getting to far into this? Is there power to be made?

Edited September 19, 2016 by rx-line

[rx-line]

As well I am thinking ignition timing would have a large impact on injection timing as well?

[GTSBoy]

The latency difference is microseconds.  Going to have precisely 3/10 of f**k all effect on any of the factors you ask about except for the simple one of how much total fuel is being injected.  And obviously enough, at high pulsewidths it has even less effect and therefore even less likelihood of affecting total power or economy.

[Dose Pipe Sutututu]

Nope, if you pool or don't pool the fuel at the valve it's not going to make a difference.. as the air/fuel will be drawn down when required as a whole when the valve opens for the intake stroke and the piston "vacs" out the air/fuel then the valve shuts. That mixture is set now with the proportion of fuel you've commanded... Then once it's ready to boogie, the spark will ignite with the flame front starting closer to the spark plug side then extending down to build pressure thus the bang.

Either way you're not going to make more power. Power comes from ignition timing and mixtures (of course other shit too like fuel octane, air density, air temperature ra ra ra).

[zebra]

Pooled fuel is bad mang!!!

Needs to stay in suspension, fuel pooling can show as an engine being stupid rich but still detonating like it is lean.

Ideally you would pulse the injector just as the valve is passing 1mm of lift so their is airflow past the valve.

 

 

[rx-line]

13 hours ago, zebra said:

Pooled fuel is bad mang!!!

Needs to stay in suspension, fuel pooling can show as an engine being stupid rich but still detonating like it is lean.

Ideally you would pulse the injector just as the valve is passing 1mm of lift so their is airflow past the valve.

 

 

 

This was my thought, just as the fuel/air entry was almost at the valve, the valve should be opening.  So far injection timing is only related to detonation and not power?

For these RC injectors I was told to get them to the point where they were spraying a little early for best idle. 

However in say an ECU with tunability like nistune, would setting my latency to match my injectors (Suggested Latency) be optimal? I.e. Spraying "the injector just as the valve is passing 1mm of lift so their is airflow past the valve." Does Nissan do this from factory? Assuming everything is in check.

[GTSBoy]

Dude,

As I said above, latency is measured in microseconds.  The difference between one injector and another injector is a few micro seconds (alright, a few hundred microseconds).  Adjusting latency is not a tuning tool for setting the start/end timing of the injection event.  it is just a tool for making sure that the delay in the injector opening is accounted for when calculating the total injector opening time.  A Nistune ECU does not offer you the ability to set either the start or end time of the injection event.  it happens on the schedule decided upon by Nissan when they designed the ECU.  If you want to play with the actual injection end point (which is what you really want if you're aiming to time it in some specific relation to valve opening or to try to avoid whatever fuel pooling scenarios are running through your nightmares) then you need an aftermarket ECU that gives you that knob to turn.

With respect to trying to tune the injection end point and/or minimise any fuel pooling, keep in mind though that unless you injectors are quite a lot larger than you need, you only have ~16ms to get your injection even done at the top end of the rev range and your injectors are therefore open for a very significant fraction of the total time available, thereby negating most of the perceived benefits of careful event timing.  Careful event timing is really good for optimising cruise and mid rev range performance.

[mr skidz]

The only time I would be touching the injector opening time in relation to crank angle would be if you are spraying far away from the intake ports.

For example using long ass velocity stacks where the fuel will require a little bit of a head start to meet the valve at correct opening time as fuel has mass and can delay in those situations especially at idle and small throttle inputs where pulse widths are very short.

The fuel really does need to get in at the right time which can effect idle quality,but on an RB the intake manifold is literally right in front of the valve I really wouldn't bother even prime pulse injection enrichment be turned off with no ill-effects as Crank injection will occur instantly anyway on cold starts so really there's no need for it it's a very short path on an RB.

If you're just worried about idle quality try adding a few degrees of timing and a bit more fuel at 0 throttle tables.

[rx-line]

22 hours ago, GTSBoy said:

Dude,

As I said above, latency is measured in microseconds.  The difference between one injector and another injector is a few micro seconds (alright, a few hundred microseconds).  Adjusting latency is not a tuning tool for setting the start/end timing of the injection event.  it is just a tool for making sure that the delay in the injector opening is accounted for when calculating the total injector opening time.  A Nistune ECU does not offer you the ability to set either the start or end time of the injection event.  it happens on the schedule decided upon by Nissan when they designed the ECU.  If you want to play with the actual injection end point (which is what you really want if you're aiming to time it in some specific relation to valve opening or to try to avoid whatever fuel pooling scenarios are running through your nightmares) then you need an aftermarket ECU that gives you that knob to turn.

With respect to trying to tune the injection end point and/or minimise any fuel pooling, keep in mind though that unless you injectors are quite a lot larger than you need, you only have ~16ms to get your injection even done at the top end of the rev range and your injectors are therefore open for a very significant fraction of the total time available, thereby negating most of the perceived benefits of careful event timing.  Careful event timing is really good for optimising cruise and mid rev range performance.

Missed your first post. I had questioned this myself, but proceeded to assuming latency had more of an effect on injection timing.

[mr skidz]

Yea nah[emoji4]

[AngryRB]

Anyone know what the latency value would be 1000cc Xspurts on Power FC?  From what i've read so far, you put this value in a leave the other stuff alone yeah?

[mr skidz]

What do you mean by leave the other stuff alone??

Are you going from one brand of 1000s to the xspurts 1000s?

If so the tune will need to be checked as different brand injectors have different characteristics at different millisecond opening times hence the term injector characterization so one injector at 10 milliseconds may flow more fuel than the same size injector of another brand this needs to be rectified.

https://goo.gl/images/vrr7E6

[AngryRB]

Im not sure bout this stuff, going from stock r33 power fc tune to rb3025 neo 1000cc xspurts, if i can get it running would save towing it an hour on the road..

 

[mr skidz]

Tow it cheaper than a rebuild

[emoji106]

[mr skidz]

For it to be explained to you in detail to someone that's not familiar with what I'm trying to explain your gonna probably f**k your engine just leave it with the experts bro

[Scott Black]

For what it's worth I can tune, have my own dyno, yet I'm currently building an rb2530neo and when it's finished I'll be installing the engine at home then paying to have it.towed to my work for the first time it fires up. I could very easily drive it into work and adjust a few settings as I go however an hours drive on a fresh engine with an ecu that isn't tuned for it is a bad idea. If it's at your tuners they can have the wideband in, fire it up and adjust settings to have it running optimal in no time and have the motor bed in properly. Where as we could tell you how to adjust settings, not be able to confirm it's right. Have you run to rich or to lean for an hours cruise at stable rpm to a tuner and almost garrenty you will glaze the bore from the Rings not bedding right.