PowerFC: Some DIY tuning comments please

[Busky2k]

I cant see why when on highway cruising the engine should be on boost. It should still be in vacuum when maintaining steady highway speeds for sure...

Btw I still reckon you can stay with 14.7 AFR for boost upto approx 5-7 psi underneath 3500 rpm. I know that my standard ECU (S14 SR20DET) does this, with no qualms.

[Robo's]

At cruise, it isnt on boost at all, i think he is meaning accelerating to 100 but then again i can accelerate there with no boost.

[Busky2k]

Mostly because by the time you are at 110kph, you are slightly on boost.

<{POST_SNAPBACK}>

Just going by what was said.

Anyways...

[paulr33]

did i enable it while tuning or do you mean now ?

im going to borrow the sensor again and re-check them soon

[rob82]

did i enable it while tuning or do you mean now ?

im going to borrow the sensor again and re-check them soon

<{POST_SNAPBACK}>

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

[JimX]

At cruise, it isnt on boost at all, i think he is meaning accelerating to 100 but then again i can accelerate there with no boost.

<{POST_SNAPBACK}>

Sorry, I worded it badly. I didn't mean on open constant throttle on flat road meant you were in positive manifold pressure, I meant at normal cruising, you will go up and down hills unless it's the nullabor or something. Up a hill the turbo can start to come on boost which will make the fuel economy suffer more than it otherwise would. I didn't mean to say that it's always on positive boost constantly at 100kph+. Also I'm sure it doesn't need to be in positive pressure to be using more fuel, just slightly less vacuum than NA would have a similar effect. Even the extra bit of back pressure keeping the turbine spinning will have a slight cost on the engine efficiency. Nothing is free.

[paulr33]

My understanding is that ultimately the airflow decides final fuel economy, as the signal given to the ECU predicates what load cell to use, which in turn is translated to the INJ map so this decides how much fuel to dial in. It shouldn't have anything to do with boost or if the turbo is spinning or not. I can cruise along at 2500rpm with my foot hardly on the pedal and airflow meter may say 2.4v if I keep my foot the same and being to drive up an incline engine load will increase (despite thorttle sensor the same) and as a result, more boost may be built up, this will also move the map cell as airflow meter load increases.

Boost driving fuel economy would only be an effect on a map sensor ECU

Airflow driving fuel economy will be the driver on an airflow ECU

if that makes sense? (sorta)

[JimX]

You're probably right. What else are we left with then? The lower compression of the turbo'd versions?

[ZILLA01]

hey guys,

just installed my pfc and my engine check light is on. what the go with that? any help would be great.

[rob82]

I cant see why when on highway cruising the engine should be on boost. It should still be in vacuum when maintaining steady highway speeds for sure...

Btw I still reckon you can stay with 14.7 AFR for boost upto approx 5-7 psi underneath 3500 rpm. I know that my standard ECU (S14 SR20DET) does this, with no qualms.

<{POST_SNAPBACK}>

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?

[paulr33]

hey guys,

just installed my pfc and my engine check light is on. what the go with that? any help would be great.

<{POST_SNAPBACK}>

The FAQ (in my signature) clearly outlines why the engine light would be on for a new install

[paulr33]

yes i turned 02 feedback back on. why?

what should i have done instead?

i will be hopfully getting it again soon to recheck them

currently going to struggle to make 300k's to a full tank of city driving

GO FIGURE!!!!

[rob82]

yes i turned 02 feedback back on. why?

what should i have done instead?

i will be hopfully getting it again soon to recheck them

currently going to struggle to make 300k's to a full tank of city driving

GO FIGURE!!!!

<{POST_SNAPBACK}>

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.

[paulr33]

Is there a map or chart / guide i can look at to suggest some AFR's to aim for when wideband tuning. i have an AFX guide which i had a look at it and also some comments on the forum

idle load 16 afr is ok

light load 15 afr is ok (upto say around 70km/h - 80km/h)

around 100km/h aim for 14.7

i wont be touching any full load or WOT

merely light load / cruise

1) turn off 02 feedback

2) plod around and check out the 02 wideband values

3) fix speed at 30kmh light load then dial it to be around 16.5afr

4) fix speed at 50kmh light load then dial it to be aroudn 16.0afr

5) fix speed at 80kmh light load then dial it to be around 15.5afr

6) fix speed at 100kmh light load then dial it to be around 14.7afr

the reasons for my afr aiming are engine safety based on heat, keep the afr lower near 100kmh to keep the exhaust heat down and down kill the valves (thanks gary for that tip)

any comments / ideas / feedback / criticism welcome as im doing it tonight

[paulr33]

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.

<{POST_SNAPBACK}>

so is the idea to tune as close to 14.7 as possible and have 02 feedback on and just deal with whatever economy i get or to tune the light load / cruise areas to say near 15.5 ish (as listed above) and then have 02 feedback off permentantly as ive dialed in my own afr's?

[rob82]

so is the idea to tune as close to 14.7 as possible and have 02 feedback on and just deal with whatever economy i get or to tune the light load / cruise areas to say near 15.5 ish (as listed above) and then have 02 feedback off permentantly as ive dialed in my own afr's?

<{POST_SNAPBACK}>

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.

[paulr33]

completed the wideband tuning again. i had closed loop off and you could see the difference, even if you dialed in a lean INJ cell value after a few seconds closed loop would run and richen it back up to 14.7 which is kinda not helpful for light load / cruise areas. so ive tuned it with 02 feedback off and left it completely off as i've checked most of the load areas and im happy with the afr's coming out. i had to make a fair few adustments and i ended up loading the apexi rb25 default map for the first 8x8 cells and then leaning it out from there using datalogit, the hand controller was taking far too long. once i had adjusted the cells in 8x8 area the afrs were happy for light cruise on streets and also on the freeway

i must have done the previous tune with 02 feedback still on because as soon as 02 feedback was off the afrs coming out were too lean so my bad. but its off for good now and will see how it runs with it being off for a week.

[paulr33]

latest tune (rename from .txt to .dat) and also inj table

paulr33_194rwkw_wideband_02_closed_loop_off.txt

[paulr33]

ok so is what i have done an ok'ish principal ?

tuned it fairly lean on cruise / light load and as the load cells increased richen it up in steps and kept the rest of the cells how they were (max power tuned). this does mean some parts of the crusing along are at afr's of 16 or 15.5 in some parts, siuch as the first row of the rev points upto 2400rpm.

jack all load so why rich? then as we increase load up the afr and i aimed for 14.7 for 100km/h cruising. done all that with keep 02 feedback off completely

[paulr33]

will run out this full tank with 02 feedback off and see how it goes

then will try it with 02 feedback back on. but 1 question i dont understand

whats the point of tuning say the first 8x8 cells and you dial in whatever AFR you feel is cool or right and then have 02 feedback turned on again when you are done and as soon as the throttle is steady closed loop comes along and dials the AFR back down to 14.7 so even if you decided AFR 15.5 is fine, as soon as you cruise for a few seconds it begins richening up to 14.7 again.

so is the ideal economy land

1) lean out the say 8x8 area with whatever AFR you feel is right / safe and have 02 feedback off

or

2) dial in 14.7afr in all of the 8x8 areas and have 02 feedback on and always run with 14.7 everywhere, at least in that 8x8 area regardless of rpm and/or load.