Rb26 Running Rich... Why?

[gawdzilla]

Setup: Motor has a built bottom end 87mm bore. Running PFC with just hand controller, regular narrowband o2 sensors, 550cc nismo injectors (injector compensation set ~ 78.5%, lag time 0.00ms), RB25 80mm MAFs x 2 (set in PFC). Fuel pressure @ 43 psi off vacuum(supra TT 290 lph fuel pump with hardwire kit), AAC tested and working. Timing is set correctly. Injectors have been flowed and cleaned.

My motor is just running rich in general. I havent stepped on the motor at all. Mostly just tuning the idle up to 3k rpm, no load. It doesnt enter closed loop at ALL with the above settings. When i leaned it out with the rough injector % compensation a little bit at a time, it runs better and actually goes into closed loop(can see rich/lean back and forth on PFC). b/c of richness, my motor BOGS and often chokes out after a quick rev/let off. I don't want to play around with the PFC settings too much b/c I still believe that the base map should be OK. Not trying to put a band-aid over a possible bigger problem if there is one.

Idle sounds OK, although still reading rich on both o2s. There is what sounds like a slight miss sometimes, not sure if its because the ignitors are on their way out, or b/c of richness and backfire?? AFM readings are ~ 1.1-1.2V across the RB25 mafs on idle.

My BOV isnt recirculating but there isnt enough pressure difference to pull them open. Just in case I have capped it off. My car isnt on the road yet or boosting at all. I have ~ 17 inHg of vacuum on idle, pressure tested intake tract for leaks.. all ok.

Questions:

-How accurate is the PFC in general with such a rough tune?

-One of the factors of my richness MAY be my injector lag time. What is the proper setting for Nismo 550cc pink tops? I have moved it around some, but left it at 0 just to be "safe". Perhaps they have less lag time than standard injectors, and thus my injectors are opening for too long??

-Is it normal for people to have to mess with injector numbers so much before they can run remotely right?

-Same for ignition maps?

Please offer some advice if possible. Thanks!

Edited October 24, 2005 by gawdzilla

[WetGTR]

I know it's not want you want to hear but maybe you should get a tuner to tune all this up on the dyno. I'm sure you have thought that but there are so may factors and with what your doing, I beleive that the hand controller is good if you want to fine tune something but I think in your case a full tune on the dyno will get your engine running as it should if its all functioning properly.

Then again I'm no expect on the PFC - hopfully a simple setting could solve your deilema

[GTR32]

go to a good tuner buddy, you're taking chances imho. just let us know if you find one.

[gawdzilla]

go to a good tuner buddy, you're taking chances imho. just let us know if you find one.

<{POST_SNAPBACK}>

i'm by no means against going to a tuner to fix the issues. However, the car is basically undriveable to get there, and I would rather not hassle w/ a tow if possible. I wanted the car to be driveable- then drive to a dyno.

I just want to know if theres something (other than tuning) that is wrong with the car.

Edited October 24, 2005 by gawdzilla

[WetGTR]

Not sure if this helps but I know the Nismo injectors have a low lag time compared to other brand injectors.

[Sydneykid]

Setup: Motor has a built bottom end 87mm bore. Running PFC with just hand controller, regular narrowband o2 sensors, 550cc nismo injectors (injector compensation set ~ 78.5%, lag time 0.00ms), RB25 80mm MAFs x 2 (set in PFC). Fuel pressure @ 43 psi off vacuum(supra TT 290 lph fuel pump with hardwire kit), AAC tested and working. Timing is set correctly. Injectors have been flowed and cleaned.

My motor is just running rich in general.  I havent stepped on the motor at all.  Mostly just tuning the idle up to 3k rpm, no load.  It doesnt enter closed loop at ALL with the above settings. When i leaned it out with the rough injector % compensation a little bit at a time, it runs better and actually goes into closed loop(can see rich/lean back and forth on PFC). b/c of richness, my motor BOGS and often chokes out after a quick rev/let off. I don't want to play around with the PFC settings too much b/c I still believe that the base map should be OK. Not trying to put a band-aid over a possible bigger problem if there is one.

Idle sounds OK, although still reading rich on both o2s. There is what sounds like a slight miss sometimes, not sure if its because the ignitors are on their way out, or b/c of richness and backfire?? AFM readings are ~ 1.1-1.2V across the RB25 mafs on idle.

My BOV isnt recirculating but there isnt enough pressure difference to pull them open. Just in case I have capped it off. My car isnt on the road yet or boosting at all. I have ~ 17 inHg of vacuum on idle, pressure tested intake tract for leaks.. all ok.

Questions:

1. How accurate is the PFC in general with such a rough tune?

2. One of the factors of my richness MAY be my injector lag time. What is the proper setting for Nismo 550cc pink tops? I have moved it around some, but left it at 0 just to be "safe". Perhaps they have less lag time than standard injectors, and thus my injectors are opening for too long??

3. -Is it normal for people to have to mess with injector numbers so much before they can run remotely right?

4. -Same for ignition maps?

Please offer some advice if possible. Thanks!

<{POST_SNAPBACK}>

Suggestion to your questions follow;

1. Very accurate

2. There is a thread on here somewhere with the common injector lag times listed, do a search, I am sure the Nismos were on the list. From memory they were pretty close to the standard injectors (ie ~0.5mS at 14 volts)

3. Yes, you have made a lot of changes all at once.

4. Yes, ditto

Some other suggestions;

A. why have you chosen 78.5% as the injector compensation? Have you just done the simple 550/444 calc? You can't do that because you are running higher than standard fuel pressure (36 psi versus 43 psi). So ether reduce the compensation (to around 70%) or the fuel pressure (to 36 psi), whichever is more appropriate.

B. While we are on that subject, why have you set the fuel pressure at 43 psi? The Nismo injectors flow 550 cc's at the standard fuel pressure (36 psi).

C. The ECU is not going into closed loop because the A/F ratios are outside the lambda sensor's range. You have to get over 10 to 1 before the S&N lambda sensor has any accuracy at all.

Hope that was of some help

cheers

[gawdzilla]

Thanks for the input. Here are some replies..

Suggestion to your questions follow;

2. There is a thread on here somewhere with the common injector lag times listed, do a search, I am sure the Nismos were on the list.  From memory they were pretty close to the standard injectors (ie ~0.5mS at 14 volts)

I'll do a search on that, thanks. I saw a .73mS somewhere, but wasn't sure if it was correct.

EDIT: according to the TOMEI website, the Denso 555cc pink tops (identical to Nismo's 555cc top feed pink tops) are .61 ms lag. I will dial that in... so .61-.772 (stock) = -.16mS

i did find contradicting info here though... anyone want to clarify??http://gtr.co.uk/forum/upload/showthread.php?t=26406

Some other suggestions;

A. why have you chosen 78.5% as the injector compensation?  Have you just done the simple 550/444 calc?  You can't do that because you are running higher than standard fuel pressure (36 psi versus 43 psi).  So ether reduce the compensation (to around 70%) or the fuel pressure (to 36 psi), whichever is more appropriate.

Accordding to the FSM, priming and idling w/o vacuum to the FPR is supposed to be 43 psi. 36 psi is with the vacuum hose ATTACHED to the FPR on idle. Both of those settings are correct on my motor. I've dialed in the fuel press to 43 psi, and the running psi with vacuum is ~36psi.

C. The ECU is not going into closed loop because the A/F ratios are outside the lambda sensor's range.  You have to get over 10 to 1 before the S&N lambda sensor has any accuracy at all.

Hope that was of some help

cheers

<{POST_SNAPBACK}>

Yes, I suppose the ECU cannot compensate for my richness because I am out of the o2 sensor's resolution range. When i leaned it out a bit, I could enter closed loop. The main question I am trying to solve is, WHY am i running so rich if PFC should be somewhat accurate? I shouldnt be running so rich that the motor bogs with no load...

Edited October 25, 2005 by gawdzilla

[Beer Baron]

i would look to the switch to the RB20 AFMS. i will assume that you have selected the correct AFM from the lift, but in my experience that is just enough to get the car running, often they will run stupidly rich when swapping to Z32s etc without doing some more tuning.

[gawdzilla]

Not sure if this helps but I know the Nismo injectors have a low lag time compared to other brand injectors.

<{POST_SNAPBACK}>

yes, it just might help. In THEORY, if i were to select a lower lag time, my total injector opening would be less, thus less fueling and leaner.

According to the tomei website, 555cc injectors are .61ms lag vs the stock .77ms.

I have had my injectors flowed and cleaned, and they vary a bit from 555cc, mostly around 560. I will put them in exactly and see how it goes.

My guess is still rich though. I had to lean it out a lot more than that just to get into closed loop.

[gawdzilla]

i would look to the switch to the RB20 AFMS. i will assume that you have selected the correct AFM from the lift, but in my experience that is just enough to get the car running, often they will run stupidly rich when swapping to Z32s etc without doing some more tuning.

<{POST_SNAPBACK}>

cool, that is somewhat reassuring. My motor is doing exactly that.. stupidly rich.

So you guys think it is ok to very conservatively lean it out (just enough to get into closed loop and avoid bogging/stalling) just to get to the dyno?

Next question:

If it is, what would be the best way to go about it?

1) perform the rough % injector reduction

2) perform the rough % AFM voltage reduction

2a) What exactly is the effect of doing this? will it move me closer to rpm 1, load 1 of the map tracer? Are only injectors affected by this change, or both injectors and timing?

3) modify and lower the first say... 10x10 of the injector map

4) modify timing? not sure on this one.. more advanced??

Thanks a lot for the pointers guys.

Edited October 25, 2005 by gawdzilla

[gawdzilla]

bump, could use some more input, thanks.