Rb25det Running Rough, Rich And Smokey After S15 Injector Install.

[Peter]

Hi Everyone,

Wondering if I could get some help please?

Car is a 1994 Skyline with an RB25DET (Series 1) with basic mods – exhaust, FMIC, pod, Apexi PFC, EBC etc.

Just finished installing some second hand side feed S15 injectors bought from this forum (upgrade from stock R33 RB25 370cc side feed injectors).

Before starting the car I adjusted the PFC (which is yet to be tuned) to compensate for these new injectors - 370/448 = 83% and 0.584 – 0.528 = 0.056 (0.06) following the recommendations of the Apexi PFC thread found within this forum.

No other changes were made with the PFC nor mechanically – it was running fine before this.

Started the car, it ran really rough – it wouldn’t idle smoothly. My wideband AFR was reading quite rich between 10 – 11, smoke (I assume unburnt fuel) was coming out the exhaust, gave it a bit of a rev and it seemed to miss…

What have I done wrong, what could I do to fix this?

Any suggestions will be much appreciated, because I was looking forward to getting this tuned once I had installed the injectors…

Thanks,

Peter

[JonnoHR31]

arent s15 injectors 480cc?

[saliya]

Hi Everyone,

Wondering if I could get some help please?

Car is a 1994 Skyline with an RB25DET (Series 1) with basic mods – exhaust, FMIC, pod, Apexi PFC, EBC etc.

Just finished installing some second hand side feed S15 injectors bought from this forum (upgrade from stock R33 RB25 370cc side feed injectors).

Before starting the car I adjusted the PFC (which is yet to be tuned) to compensate for these new injectors - 370/448 = 83% and 0.584 – 0.528 = 0.056 (0.06) following the recommendations of the Apexi PFC thread found within this forum.

Hey,

I had to adjust the bat volt/lag correction table to get mine nice on a stockish map (stock RB26 -> 700cc Sard).

I got my figures from http://injector-rehab.com/kbse/lag.htm and calculated the offset manually for the voltages that are in the PFC (they don't exactly line up with what's on that page).

I wound up subtracting 0.3 of correction basically everywhere.

It would be awesome if we had our own database of PFC settings for our cars. If I get bored I'll start something that's compatible with FC-datalogit and/or Copilot.

I don't know that this will help since I'm not sure that either set of injectors you have are listed there

But since you have a wideband, and you are observing that the car's rich (both from the readings and the fuel-laden exhaust) - you should probably just pull some fuel out of it and drive it to the tuner's.

Regards,

Saliya

[bradsm87]

370/480 = 0.77

S15 injectors are 0.52, stock injectors are 0.58 so the latency should be MINUS 0.06 aka -0.06

Should be sweet after that.

[Peter]

arent s15 injectors 480cc?

Yeah, I thought they were, but I seem to see the 480cc and the 448cc figure floating around and the "PFC bible" labels them 448cc?

[Peter]

370/480 = 0.77

S15 injectors are 0.52, stock injectors are 0.58 so the latency should be MINUS 0.06 aka -0.06

Should be sweet after that.

Thanks for the help mate, and I will give it a go - I hope it fixes the problem!

The reason I did it my way cause the "PFC bible" says:

If changing 440[cc/min] to aftermarket 600[cc/min]

440 / 600 = 0.73

Enter the value "0.73" for each cylinder.

Bolt-on turbo spec. POWER FC applications assume that the injectors have been upgraded. This is why "1.000" is not entered as the starting data for the injector values.

Injector Lag Time Setting

The POWER FC includes factory vehicle injector data. If you switch to any other type of injector, be sure to perform the calculations below and input the correct values.

Changing the factory 440[cc/min] with 0.78[msec] injector lag time to an aftermarket 600[cc/min] injector with 0.85[msec] injector lag time is:

"Injectors to be used" - "Factory Injectors" = "Correction Value After Changing"

0.85[msec] - 0.78[msec] = 0.07[msec]

Enter "0.07" into the [msec] parameter for each cylinder.

*If the aftermarket injectors have a shorter lag time, add a "-" (minus) before the value.

So what I did was 370/448 = 0.83 and 0.584 - 0.528 = 0.06....

I will alter it to what you suggest though...hope it works!

Thanks,

Pete

[Peter]

Hey,

I had to adjust the bat volt/lag correction table to get mine nice on a stockish map (stock RB26 -> 700cc Sard).

I got my figures from http://injector-rehab.com/kbse/lag.htm and calculated the offset manually for the voltages that are in the PFC (they don't exactly line up with what's on that page).

I wound up subtracting 0.3 of correction basically everywhere.

It would be awesome if we had our own database of PFC settings for our cars. If I get bored I'll start something that's compatible with FC-datalogit and/or Copilot.

I don't know that this will help since I'm not sure that either set of injectors you have are listed there

But since you have a wideband, and you are observing that the car's rich (both from the readings and the fuel-laden exhaust) - you should probably just pull some fuel out of it and drive it to the tuner's.

Regards,

Saliya

Thanks for the link mate, pity they don't have my injectors though!

Peter

[STATUS]

make sure the o-rings are NOT nicked, if so it will run like shit.

An r33 should just about run fine (rich but not miss) with s15 injectors bolted in place of the original 370cc items

Edited October 19, 2009 by URAS

[Dale FZ1]

When I had S15 injectors installed, it ran perfectly with 82.5% and 0.12 lag correction figures and using the stock FPR. There was some discussion on this forum in the day regarding lag, and considering that their design is very similar to stock there may be little if any practical purpose in entering a correction figure. Another member was using a difference lag correction and we each claimed to have good results in terms of power, starting, driveability, and fuel consumption.

Even the arguments over whether they are 448 or 450 or 480cc injectors is a bit academic because it's just a number that will determine what numbers go into your fuel map. My homework at the time suggested S15s were 450cc @ stock rail pressure, and they can/will flow more with higher pressure.

If you hadn't bench tested them prior to install, could be worth pulling the rail out and crank it over to check that the fuel sprays without dribbling, and/or that they don't appear to be sticking open. Make sure your ignitor is disabled at the time, and limit the number of times you do it - don't want excess fuel vapours floating around the engine bay with potential ignition sources.

[MrStabby]

Since you're running rich, it indicates you've used too small a size or too small a latency value. Latency makes a big difference at idle and low throttle, size makes a difference everywhere. So, if idle is rich but WOT is good change the latency, if its rich everywhere change the size

[Peter]

Hi Everyone,

Thanks for all your replies. I'll try adjusting the PFC some more. If this fails I'll begin to remove the fuel rail again to see if I have messed up anything mechanically - I'll let you know how I go! (Hopefully adjusting the PFC will fix the problem!)

Anymore suggestions? (Please feel welcome to add as I really want to get this sorted!)

Thanks again,

Peter

[D_Stirls]

the reason why you are thinking 440cc is because ADM S15 = 440cc it's the JDM S15's that have the 480cc injectors

[Dale FZ1]

Sorry, but the only difference comes about from whether the S15 was fitted with manual or auto gearbox.

Manual = 450cc = brown/terra cotta colour

Auto = 370cc = purple colour (same as the RB25)

The ADM / JDM story was kicked off in a HPI magazine article and has remained ever since. Head to a Nissan spare parts counter and you'll find the truth via parts numbers. I know because I did it.

I do believe the problem as above is not in the PFC settings, but something more likely with the install (probably) or the injectors themselves (possible but not as likely).

[Dose Pipe Sutututu]

ADM or JDM they're all 450cc, same part number

The BS hyped up 480cc rating comes from that chart which rates them at 480cc BUT at a different fuel pressure.

If you compare the stock fuel pressure of the R33 injectors and S15, then the S15 ONLY flow at 450cc

I'm running S15 injectors too, the previous owner had them set at 77% with 0.10 lag time, I know its fully out of whack, but I don't have a problem with them, I've connected a datalogit to it and fiddle with the A/F and Timing and the A/F is spot on to what I want.

[Birnie]

Yeah, i put those babies in Johnny.

I originally went to 82.5 and whatever on the latrency, as Dale says, i tried a few values on latency but found no noticable difference...and i don't think anyone still has found a decent definition of what this value is used for.

In fact (as i've never replaced em before, 1st go) when i turned the key i was wishing/hoping/crossing fingers that i had it all right, and it was as if nothing had changed at all....super stoked! Drove like normal, no change in fuel consumption, and i drove it like that for 1-2 months (excluding WOT's) until the full tune was done

The 77% is only usable as it's had a full tune.

The tuner at the time said he would find his own setting for that and re-tune the car to suit.

You should be able to (theoretically) have any number there if getting a 'from scratch' tune.

[Tangles]

mine went in today (I think)

with the aem fic-8 ecu, you simply open airfuel, right click, type in new injector size vs old size, and whola it makes the map

[STATUS]

as i said previous im sure it is nothing to do with the pfc, the car will hardly notice the 440 (480cc) injectors. I drove my old car round for a week on 440cc (yes its rich but not enough to make it splutter)

One other thing how long did it run for? it will take a few minutes to clear out the cylinders from all the extra fuel dumped in the cylinders when the injectors were removed....

[JonnoHR31]

i tried a few values on latency but found no noticable difference...and i don't think anyone still has found a decent definition of what this value is used for.

latency or dead time is the amount of time the injector takes to open after being pulsed by the ecu. just changing the correction will get the afr's close enough under high load but under light load and at idle the latency has a much bigger effect, as its a set opening time. unless you have some injectors that no one has even heard of then theres no excuse for not setting them up properly before starting the car.

[Peter]

as i said previous im sure it is nothing to do with the pfc, the car will hardly notice the 440 (480cc) injectors. I drove my old car round for a week on 440cc (yes its rich but not enough to make it splutter)

One other thing how long did it run for? it will take a few minutes to clear out the cylinders from all the extra fuel dumped in the cylinders when the injectors were removed....

I only ran it for 20 or so seconds...maybe (hopefully this will be the issue?) How does the fuel get dumped in the cylinder when you remove the injectors? When I pulled out the stock rail and injectors no fuel came out until I popped out the stock injectors - then the rail was quite dry when I put in the S15 ones?

[Peter]

Hey Guys!

Once again thanks for all the replies! I still haven't had a chance to adjust anything as yet, due to being so busy at work!

As stated before, when I do get a chance I will try adjusting the PFC to see if it fixes the problem - I hope it does. If this fails, I will look into the engine bay once more and start working my way towards removing the rail and injectors...

Any more suggestions would definitely be helpful - and I'll add it onto my list of things to do!

Thanks!

Peter