Rb25 Problems

[95_240]

I have run out of success on North American forums and I have searched through here and haven't quite found the answers I'm looking for. So here is my problem.

I have a series 2 rb25 with greddy manifold, q45 throttle body, and I'm running 10 psi. I hooked it up to a consult program and when it is running ok the idle is at 1400 rpms, maf voltage is about 1.5, tps is .45, injection time is 2.5 ms, and my vacuum is at 20Hg. The afr reading fluctuates from 14.5 to 15.5. After i rev the engine a few times the afrs read 10. The idle fluctuates between 500-800, the maf reads 2.5 volts, tps remains the same, and the injection time jumps up to 7.5 ms. The vacuum also drops to 10Hg. The timing increases to about 35 BTDC when I rev the engine and when it drops back to idle the reading is between 5-10 BTDC. I've unplugged individual sensors and the only one that did anything was the maf. When it was unplugged the car would stall.

Some more notes.

I used 1M ohm 1/4 watt resistors to trick the knock sensors. Still nothing it keeps on dumping a ton of fuel and you can hear the maf actually sucking in more air. I've tried multiple mafs, tps's, and have checked the wiring numerous times. I did notice that when the car reached 115 degrees F or 46 degrees C it started acting up. The coolant sensor readings on the consult do agree with my aftermarket temperature sensor so I'm ruling out the coolant temp sensor unless someone else can suggest that it is bad.

Thanks for any help.

[DVS JEZ]

Are u using the stock bov still?

[95_240]

I'm using a synchronic bov but right now I have it bypassed so it is closed and not bleeding of any air.

[The Mafia]

Between a q45, no bov, and Freddy intake manifold, the factory ECU won't be liking that at all.

Can you get decent aftermarket management and tune it?

Also, have to checked your base timing?

[95_240]

It runs the same when the bov is hooked up or not. I've seen plenty of setups that run a q45 throttle body and aftermarket manifold without any problems. It isn't like it is barely missing or anything it is not driveable. Base timing is set to 20 BTDC.

Edited April 9, 2012 by 95_240

[GTSBoy]

Why would anyone think they can change the AFM without needing to tune around the different shape airflow-voltage curve?

[95_240]

Not sure what you are saying. If you are suggesting that I changed the AFM I did not it has the stock one on it.

[KiwiRS4T]

Should base timing not be 15 deg? Why did you put a Q45 throttle body on it? Which TPS did you use? Pretty sure your problem is tune related - you need to find a PFC or the right Nistuned Z32 ecu or as you are in the US maybe get a Link and then you can run your Synapse BOV and ditch the afm.

http://www.linkecu.com/dealers/north-america-dealers/dealersusa

[95_240]

I have tried the timing at both 15 and 20 with the same results. I put on the greddy style manifold and the q45 throttle body is a bolt on and that is why I used it. I'm using the q45 tps. I don't see how the manifold and throttle body can affect the ecu that much. The only problem I could see it causing is a little bit of lag since it is larger. The AFM is still reading all the air so I don't see why it would need a tune yet. I actually talked to a distributor over here about getting Nistune but he advised that I address the problem and fix it. He told me not to tune the problem out.

Edited April 9, 2012 by 95_240

[GTSBoy]

Not sure what you are saying. If you are suggesting that I changed the AFM I did not it has the stock one on it.

Haha, sorry. Wrong thread and wrong forum!! Two windows open, 50/50 chance of getting it wrong I suppose.

[KiwiRS4T]

OK but here is a rare opportunity:

http://www.trademe.c...n-465141160.htm

Dumping fuel sounds like the rich and retard function of the ecu - does the timing change suddenly at any point? I think you should get a tunable ecu regardless but maybe if you can find one swap out your stock ecu for another just to eliminate it as a problem.

ecu to Nistune: http://www.trademe.co.nz/motors/car-parts-accessories/nissan/ecus/auction-463835153.htm

stock ecu http://www.trademe.co.nz/motors/car-parts-accessories/nissan/ecus/auction-464840539.htm

[The Mafia]

Should base timing not be 15 deg? Why did you put a Q45 throttle body on it? Which TPS did you use? Pretty sure your problem is tune related - you need to find a PFC or the right Nistuned Z32 ecu or as you are in the US maybe get a Link and then you can run your Synapse BOV and ditch the afm.http://www.linkecu.com/dealers/north-america-dealers/dealersusa

Base timing should be 15 degrees but it never hurts to check.

I'm not sure that the Q45 TPS will be able to talk to the ECU properly? Have you checked the TPS voltages in consult to see if they are scaling properly?

[95_240]

The Q45 tps uses the same as a series 1 tps. It is scaling fine and it actually has a brand new one on it.

[95_240]

I thought it was going into rich and retard as well. I thought I could prevent this by tricking the knock sensors but that didn't work. My initial plan was to get Nistune and have both the knock and normal maps the same. However, the distributor for Nistune told me to try to fix it first. I actually went out and bought a z32 ecu today.

Edited April 10, 2012 by 95_240

[GTSBoy]

R&R is not as simple as just changing maps. The high load end of even the normal map is spastically rich and retarded, and the knock map just takes that to extremes. And R&R is not just triggered by knock. You actually get it from high TP. High TP essentially just equates to a higher AFM signal than the arbitrary limit that Nissan put into the ECU.

Nistune actually makes it trivial to fix that, as you can adjust the max TP value in about 3 seconds, and then you remap the high load ends of the fuel and ignition tables to get rid of the excess caution (and of course retune everywhere else while you're at it).

[95_240]

I think that explains a lot. I guess it might be freaking out because it is getting such high voltages through the AFM at 800 rpm. About 2.5 volts. It is fine at first but as soon as it is given partial throttle for a split second everything goes wacko. I think this might be related to a problem the tps is having. I didn't state this before because it is acting normal for now. The tps has always had a good ground and 5 volts but the signal sometimes would drop to .15 volts closed and .5 volts fully open. I tried 4 different tps and even put a new one on. I don't know what would cause the signal to sometimes be fine and other times not.

I do have to say this forum is awesome. It took one week for someone on another popular forum to respond and it was not helpful.

[zebra]

are you using a skyline loom or a bitsa?

could be a wiring issue if you are seeing voltage fluctuations

my AFM usually read around 1.2-1.5 at idle

[95_240]

It is made by a company called Wiring Specialties. It is one of their premade harnesses that uses all new wiring and made to fit my car specifically. When the car is idling fine the AFM is seeing close to 1.5 even though it is idling at 1400 rpms. The only thing that has been noticeably weird is the tps. I even hooked up the 5 volt directly to the ecu bypassing the harness and grounded it directly to the chassis.

[89CAL]

your probably better off just unplugging the knock sensors all together then running resistors in there. It doesnt run off voltage feedback from memory, it runs off frequency (It's early, I could be wrong but its not as simple as voltage)

It looks tune related. Timing and fuel changing as they are suggests that after some driver inputs the ECU is not happy with how the car is running and is adjusting the tune to fix the problem. The R33 ECU's are sensitive and all seem to be a bit different. For example when I had a stock ECU and some mild mods, car would not run on 10psi, would just cut out when it got to certain RPM, and when it was dynoed on 8psi only managed 141rwkw. Where as I know other R33's with the same mods got alot more power then that. Others wouldnt just cut the engine like mine did, but would hit R&R

Take out the resistors in your knock sensor circuit, i dont think thats working, maybe try just unplugging them. I think you will find, as suggested already, find a programmable ECU

[95_240]

I've already put resistors in place of the knock sensors. I also don't think it really has anything to do with how much boost I'm running because it is acting up at idle and when the car doesn't have boost. I'm thinking the ecu may be bad. The person I bought the swap from let it sit outside for 2 years and the ecu may have gotten wet and screwed something up. I just ordered a Nistune board to use with the z32 ecu. Hopefully that will help correct the problem or make it easier for me to diagnose.