pcmhacking.net

Calling clever tuners!

My friend (budwizer) and I have been working on my turbo 202 project on and off for a few years now.

It was NA first, and running on a tune we tweaked on a standard 202 a while back that originally came from this forum. It has wideband, NVRAM 2bar.

I guess my thoughts right now are - are we missing some fundamentals or some key knowledge that's giving us gremlins.

The main issue I am struggling with now is idling and free-revving. It will idle a bit rough at around 950rpm and 12.5afr, given time it will start to oscillate up and down by say ~50rpm until the high speed fan turns on which will stop the oscillation immediately. It will start again once the fan turns off. It will also stumble over itself and oscillate badly with light throttle on the spot (say 2-5%tps) between 1200 and 2000rpm.
And at low speed and low load it will jerk back and forth.

Thing is, I can 'fix' all of that by increasing the VE values under IAC-idle MAP threshold and putting what looks like way too much fuel in the VE table at 30-40kpa across the rev range. But it then runs rich under some light driving scenarios and it 'idles' at 1300-1500rpm. And the idle variation value sits at zero which makes me think it doesnt consider itself idling. The IAC wont close to under about 50steps to reduce the idle and the throttle stop screw seems to have no effect
I have several bins and logs from various times I've tried to resolve this which I can post. As there will be other cleanup bits probably required too. But it's driving me nuts that my knowledge isn't good enough to figure it out!

I'd like to know also from some of the elite tuners out there how you go tuning something where there isn't a factory tune, but it needs to run smoothly, idle smoothly, warm up and drive well. Because I feel like maybe we missed some foundation items

What injectors are you running? Are the injector bias vs battery voltage tables configured to suit them? Ive just been fighting with poor idling and unstable results at idle on a mates car which came with no factory tune and improvements to the bias helped hugely.

They are Deka 60lb injectors and we had set up the bias from some info somewhere. But looking again now i cant find any official bias table, only a graph at http://www.sonicperformance.com.au/docu ... 114961.pdf

What i have in the bin is:
4.8 3.86
6.4 2.70
8.0 1.66
9.6 1.17
11.2 0.79
12.8 0.60
14.4 0.35
16.0 0.26

Here is the current BIN in use. Just after changing the IAC idle MAP threshold to lower the idle RPM
My understanding was that table should be set for the max kpa at each RPM that idle will be active underneath - is that correct?

I also noticed today there are quite a few scalars and curious what they do:
IAC Params - Max MAP load limit (mine set to 42.09kpa which is close to idle kpa)
Idle fuel param - RPM threshold for filtering VE (mine is 0RPM)
Idle fuel param - RPM above desired to begin lowspeed enrichment multiplier (mine is 0RPM)
IAC - Transient IAC params - Throttle crack decay rate (mine is 3.13secs) is this for when you rev slightly and the IAC brings things back to idle slowly?
Idle fuel param - delay before using idle A/F ratio(manual & auto in drive) (mine is 18seconds) - when does this come into effect?

I'm keen to learn how to fix this issue but also just keen to learn tuning in general for other projects!

Your bias figures are quite different to what I settled on for the same injectors, someone else asked about this just a couple of days ago:
https://pcmhacking.net/forums/viewt ... =28&t=5548
I was having trouble with off-idle tuning until I got these sorted too.

I will try those values this morning and see how things change
What is your flow rate with these injectors? Mine is at .650

It may clean up the lower rpm idle but I imagine it won't make a difference to the partial throttle free-rev nonsense I'm getting between 1200-2000rpm
I will report back soon

just a question on 12.5 at idle, that seem awfully rich, does it need to be that rich ?

I went to change the values, but have a question - wouldn't this affect the rest of the tune fuelling too? Should I have to also adjust the injector base rate?
Yours is double mine at 14.4

Yeah I don't like that it's so rich, but if I take fuel out it is more erratic.
Probably the cause is that we're missing some fundamental settings somewhere.

I also think the boost spark tables and boost spark charge temp table need to be redone and a few other small things

I would welcome anyone with experience that wants to have a look at the bin and make some suggestions to do so

ok I've had a bit of a look at the bin above with the worlds longest file name

first thing I can see, idle timing ..... actually the whole timing map is a bit odd ... I'm not sure what map value this thing idles at but 20-50kpa range of the idle spark I would suggest is too high.

also the idle spark table values should be mirrored into the main spark table for the idle rpm area then the rest smoothed in, and generally for tuning idle spark I try to aim for the number that gives the most vacuum.

also the timing should generally increase with more vacuum, whereas with yours it peaks at 70kpa then drops back to 20kpa column.

I would smooth out the VE table too, and make the 20-30kpa columns level with the rest of the map.

also with the idle AFRs ... make the actual wideband reading match the target AFR at idle, then if the car is hunting or such change the values in the idle AFR table to what you want, as currently your saying it wants to idle at 12's but the idle table is commanding 14's, which probably means the VE table is out in that area to get the number you desire.