rob82

S4 Dataman

I dont mean to sound patronising but why would you spend all that money on a build and then not have it tuned correctly??

Shit mate if your having problems tuning a MAF based PFC then a speed density based system isn't for you.

As in independant exhaust and inlet phasing and hell why not do lift as well.

My Jinglish isn't so good. Sounds good though. Suprised nissan hasn't done more with cam phasing.

This is just a learning proceedure for idle control vavle. Its just a loop it performs until it determines what the optimal position of the vavle is to acheive the desired idle RPM. It just needs to learn 2 modes neutral AC on and neutral AC off. Its the same proceedure the AU fords use and if its auto it has 4 modes as in neutral AC off and On and Drive AC on and off. Note this proceedure doesn't have anything to do with mixtures. Chances are you will pull more load with AC on so it look at what cell its on and check the cells around it as it might be interpolating around that cell. Make sure you tune the with 02 feedback off and once your done turn it back on. Aim for stoic at idle. Drop me a PM if you need some more help.

F/C1 - decel fuel cut recovery 1 (AC not on) F/C1 - decel fuel cut recovery 2 (AC on) VTC - Variable cam timing change over point

Just wondering if anybody is running these prepped rods at any sort of decent power 350awkw or above??? From the picture it looks as though they have ground off the piston squirter from the side of the rod. I would have though that this would cause a stress location along the side of the rod. I know its not on the thrust side but while one side is in tension the other is in compression via simple elastic beam thoery. http://www.nismo.com.au/pricelists/General...s/conrodshd.jpg

What he said!!!! Something to think about.

I've found on the RB25's that a knock reading around 40-50 can be heard through a chassis ear but is not audible to the ear, however a knock reading around 80 is most defintely audible to the chassis ear and the naked ear.

If your happy enough with your mixtures and dont worry about accelleration enrichments then I would leave the O2 sensor off otherwise enable the O2 feedback and tune as close to stoich as possible. I would say once your happy with your timing numbers dial in the say 13.5:1 at zero boost and hold it at constant load. If after a sustained load at this boost it introduces a higher knock figure on the PFC then enlean the mixtures futher until the knock numbers start to increase. This is the point at which the chamber temps are sufficiently high to cause detonation so you richen it up just a little to reduce cylinder temps. For a standard cast bottom end RB25 I would aim for around 13.2:1 at zero boost, 12.5:1 at around 6psi, 12:1 at 10psi going off to 11.8 high in the rev range.

If your mixtures are around 15:1 AFR open loop and you command a closed loop AFR of 14.7:1 then the O2 sensor slowly trims more and more fuel until it reaches 14.7:1. The further from stoic you open loop mixtures are the more it has to trim and you using more fuel this is why the call it feedback as it waits for a conditon and then trims. What you want to do is tune as close to stoic as you can, this way the O2 sensor will have very little trimming to do. Alternatively you could just turn off closed loop and tune whatever you want.

Thats correct they do stay closed loop until about 7psi of boost pressure however the standard ECU has a time at load until additional enrichment function as well. This way if you just coming onto boost for a bit and then back off it will stay closed loop to save you feul however if you are on boost for too long cylinder temp sky rocket. This is why they introduced this function. And paulr33 I still very sceptical on your aiming for 15:1 AFR as the PFC doesn't have a lean cruise function. Do you turn the 02 sensor feedback on once your finished?

Like what? Please elaborate.

Was it disabled while you were tuning and did you re-enable it after tuning?

Did you enable the 02 sensor feedback function?

I would say they are better then motec but thats just me. The guy that designed it, software and hardware(Richard Orbit) was the brains behind motec before he left. The autronic uses a thermodynamic model to determine fuel delivery. Thats why you must enter engine capacity, compression ratio, amount of cylinders etc etc. Its very smart and lots less mapping than motec as the maths is done for you.

and standard injectors

You can make about 250 260rwkw on a GTR with standard FPR.

THe xr6t's have a cylinder head temp sensor right in the middle between the two valves on the back of the head no 6 cylinder. At 300rwkw a 10 second dyno ramp can yeild a rise temperature from around 90deg to 110-115 degrees. I would have though at this temp the coolant would start to boil?

Like I said what timing numbers, if the ignition is overly retarded then you will generate a miss as the combustion event will be under more load since the piston is closer to the top of it stroke hence more combustion pressure. And also what plugs?

What kind of timing numbers are you running and is your base timing correct? Try adding a couple of degrees and see what happens. Check for little white track marks around the boot also.

Hmmm the old speed density vs MAP debate. Airflow meter based ecu's are the most consistent and efficient means of determining how much fuel is to be injected bar none. Not even fords 32bit floating point PCM is able to match the consisency of holdens, nissans, subaru's mitsubishi, porche, ferrari MAF based systems. That said I believe for went back to speed density due to the numerous amount of MAF's that were failing in the eariler model v8's and this is something that all manufacturers have to deal with. Downside to speed density systems - cam timing. The way the ford PCM works(which I think is the best) is to apply a linear equation (flow on y and manifold pressure on x) for each cam phase angle for every 500 rpm. This requires alot of processing speed and is highly complex. Speed density based computers do have their advantages on the big horse power race cars over a MAF based ECU as eventually MAF's do cause a restriction and this can occur at lower power numbers then what most think.

Did they use a chassis ear when tuning?