R33 Series Ii Fuel Injectors - Need To Know The Lag Time

[The Mafia]

well, I noticed on cruise, boost, off boost, everything, my car is pouring black smoke.

Even with the AFR's running at 15.7:1. I'm going to assume the injector setup by my "mate" of a wanker tuner is set up incorrectly... (this guy really was a waste of money..)

I have just had a look at the Datalogit Settings, and it says that my injector size adjust is 77.0, and my lag time is 0.40.

Now, the datalogit says that to work it out:

Old Size Divided by the new size = Difference.

370cc / 555cc = 66.7% (the tuner has entered 77.0%...wtf?)

old lag time minus new lag time = final lag time.. The tuner has entered 0.40ms.. I want to see if this is stuffed up too..

I don't know the standard lag time for R33 injectors, can anyone help me?

Edited May 29, 2006 by The Mafia

[The Mafia]

can anyone help at all?

I really need to know this..

[Color_Of_Green]

I might be able to help but I am just learning this stuff myself.

From what I know the stock injectors have a lag time of 0.58ms. Google tells me that nismo 555cc injectors have a lag time of 0.71 ms but not sure if you have these. Best bet to ring nissan dealer and ask the question.

From what I understand, the injector lag column is the difference between stock and your new injectors so in your case should be (0.71-0.58) = +0.13ms, however you will notice that you can only select in increments of 4 or something so 0.12 is probably the best bet.

As for the injector trim calculation 370/555*100 = 66.7% is correct but be careful that your "tuner" hasnt also applied a 11% trim to each cell in your INJ settings.

Hope this helps.

[Cubes]

The inj. correction really doesn't make any difference providing the base map has been tuned to suit, as Color_of_green has stated.

Its pretty much the same with lag time but it IS best to get the lag time right.

I'm curious as to how its pouring black smoke?

On idle? Under boost? Under quick heavy throttle?

Mine with a flat 12:1 afr still trickles a little black smoke on wot, it can especially be seen at night time in the head lights of the dissapearing car behind.

If its dropping a puff here or there look at the accel enrichment. I believe with the pfc you are able to reduce the sensitivity of the accel enrichment which 'MAY' pick up a little fuel economy as it doesn't drop out of closed loop as easy. I know with mine it is very sensitive to throttle input, the slightest little quick flick of the throttle and it drops out of closed loop.

[BHDave]

i don't know about the 550's but the difference between stock sr (which are the same as rb25 anyway) and nismo 740's is only about .02ms i think (it's been a while since i set it up)

The difference between my stockers and my 550 single pintle (laggy) injectors is only .12 from memory.

I'll dig up my apex engineering sheets when i get home and check. Are you sure the lag isn't .04, .40 is way off?

[Lunatic Dancer]

Sorry Mafia dude, since we are on the topic i'd like to ask a few too..

So just say that the tuner has inputted wrong settings for the injectors and went ahead

to tune the whole thing. Once you change the settings afterwards to the 'right' settings

does that mean the injector table will be leaner across the board?

BHDave - can you please check if that 0.2ms is correct? Because i'm running the nismo 740's on my

sr and the settings were already wrong.... but using the calculations shouldn't the lag time be 0.08?

50% - 0.08ms (0.66-0.58).

[The Mafia]

thanks for the replies guys.

Does this mean my lag time of 0.40ms is shithouse, and should be 0.13ms (0.71- 0.58)?

[Color_Of_Green]

thanks for the replies guys.

Does this mean my lag time of 0.40ms is shithouse, and should be 0.13ms (0.71- 0.58)?

Yeah, I'm not sure it would run properly with that much...

Put your lag time to +0.12 dude.

As for the trim % on each injector I wouldnt touch those unless you are absolutely sure he didnt apply the trim straight to the INJ correction map [ which is very easy to do in datalogit ].

[BHDave]

BHDave - can you please check if that 0.2ms is correct? Because i'm running the nismo 740's on my

sr and the settings were already wrong.... but using the calculations shouldn't the lag time be 0.08?

50% - 0.08ms (0.66-0.58).

I'll try and remember to check tonight.

If the lag times that you have listed are corrent then you will be right. I just seem to remember .02 for some reason. Either way if you have a higher number and the car has been tuned with those setting s in already then there shouldn't be a problem.

[Lunatic Dancer]

ok thanks BHDave..

I did some searching...and found these

nismo injectors

555cc lag time - 0.71ms

740cc lag time - 0.66ms

from pfc manual

ecr33 rb25det

370cc lag time - 0.528ms

sr20det

370cc lag time - 0.58ms

for example if the figures were wrong, say proper was 50% - 0.08ms and 50% - 0.20ms was put in,

will that make the idle or the rest of the map extra rich?

[paulr33]

ok to add those figures to powerfc FAQ ?

[BHDave]

I checked my apex chart and it shows the nissan 370's as .64, the 550's at about .67 and the 740's at .66

So thats where my .02 came from.

Either way, if it's tuned right then a slight difference in lag time will make little difference as lag is added to the open time to get a certain amount of fuel.

From my basic understanding of the whole thing (and i could be wrong here)

Say for example that the engine needs a certain amount of fuel to acheive correct a/f ratios, then the ecu triggers the injector for a set time (lag time) plus the user (or tuner) entered value of say 3.00ms for an example.

With stock injectors it will provide power to the injector (according to my info anyway) for 3.64ms.

chuck in a set of 740's (double the size, makes it easy) the injector needs to be powered up for .64ms (stock lag) plus difference in lag (.02) plus 1.5ms (due to the injector being double the size not considering all the fluid dynamics and stuff involved) so total powered time will be 2.16ms.

If you have a different lag time (say .12) with the same 740cc injectors, to get the same amount of fuel in you will have .64 + .12 + 1.4ms (user/tuner entered) for a total powered time of 2.16ms if you get my drift.

The only thing that i'm missing is the point in time when the injector gets powered up as i think that will make a difference, particularly when you are talking about such small open times, what i'm getting at is if you input a really big lag time will the injector be powered up earlier than with a small lag time or is the opening time fixed and the closing time altered? If it opens too early is the fuel hitting the back of the valve rather than getting pulled/puhed into the cylinder?

Edited May 31, 2006 by BHDave