tici

iTrader: (1)

Do you need a different fuel tune for summer - winter?
Do you notice a difference in LTFT?

In summer I see LTFT's around +1 / 0% and now -2 / -3%
At wot in summer I see 12.5 - 12.7 and now 12.3 - 12.5 AFR...

Not a big difference, but I'd like to know.

Thanks

Xtnct00WS6

iTrader: (8)

Are you mafless? If you are then I think there's a benefit to having a tune for each of the 4 seasons. I doubt most people do though.

tici

iTrader: (1)

Stock untouched MAF, stock internals and same configuration and tune since last June.
Stock VE and MAF tables. I tuned it only by IFR using LTFT & STFT versus MAP values (so it's the real IFR curve and not theoretical values).
36 lbs Bosch injectors and an additional oline Raptor fuel pump.
O2's are about 20'000 miles old. Both banks show the same vaues (+/- 0.5%).
PE is road tuned using a WB fix installed in the stock exhaust system (before the passanger cat).

Theoretically the MAF should compensate air temperature, pressure and humidity (as it measures air by weight), but somehow something is different.

I don't know if in winter the fuel is different, if the manufacturers add some additive to reduce emissions or so. I know this happens in some places, but I don't know if it affects fuel trims.

chrisj6

Tune it by your MAF and VE table and you will have better results. Your trims will swing a little bit with the seasons, but thats not enough to matter.

ringram

Im pretty sure fuel is different in the seasons actually. See here http://i-r-squared.blogspot.com/2006...-gasoline.html

Doc

iTrader: (9)

Here's an idea, upgrade/swap the 98 pcm for a 99+up and run custom OS. You really don't have the full capability with that OS. The 98 OS is your biggest obstacle.

tici

iTrader: (1)

Already tried: MAF is not so accurate as IFR and is difficult to tune at high air flows. G/sec also influences torque measurement and timing (G/Cyl) and as long the MAF is stock I won't mess with that table.

VE is VERY wheater sensitive.

So far I have the best results tuning by IFR.

Why is the 98 OS a problem?

Steel Chicken

iTrader: (3)

no need. MAF or SD tunes will compensate for temp and pressure changes.

MeentSS02

iTrader: (11)

I had to change my tune when they went to the winter oxygenated gas here in OH. I'll have to change it back when they switch to the other gas this spring. No big deal...

GuitsBoy

iTrader: (4)

Im constantly tuning, but ill notice that in both the extreme heat and in the cold, i need to add fuel. Straying away from that 55*-75* zone, and she wants more gas.

tici

iTrader: (1)

Interesting.
In my case It needs less fuel in winter.
In winter lower MAP values need a bigger fuel reduction (-4%) than high MAP (-2%).

How does this gas affect fuel trims? Rise them? lower tham?

MeentSS02

iTrader: (11)

I don't run in closed loop, so I don't have any trims, but my wideband was reading leaner after the switch...if the narrow band O2 sensors acted the same way, it would send the trims positive because it would dump more fuel to compensate. That's pure conjecture though...

tici

iTrader: (1)

Ii it much better constantly in open loop?
What AFR are you running? I can imagine 14.xx low load, 13.xx middle load and 12.xx high load... like a carburator?

Do they show over there what kind of gas they sell? I mean, standard or oxygenated?
Over here it's theoretically always the same juice...

MeentSS02

iTrader: (11)

I wouldn't say much better, but I don't have to worry about my narrow band O2 sensors going out. That's what prompted the move to open loop...one of my O2 sensors crashed and was causing it to idle around 11.0:1 AFR. Pissed me off enough that I ditched them completely. You do have to stay on top of the tune, but I only have to tune it about 2-3 times per year at most.

As for the kind of gas, I've never seen any indication of when they switch over to oxygenated gas. I realized it as soon as they did it (my wideband O2 sensor runs full time, and outputs to a gauge), and I knew this area of the US uses the oxygenated gas in the winter.

Doc

iTrader: (9)

MAF is not going to be so accurate with an underlying VE problem....Also the 98 OS's other MAF problem is a lack of resolution at high airflows...the exact problem you are facing. The 98 MAF table stops short, the newer OS's go up to 12000Hz.

Your Injector Flow rate is what it is...one lie leads to another until the music stops and you have no chair to sit on.

Another bigtime PITA of the 98 OS is the need to be in the reduced resolution backup VE table in order to tune. Then when you go back to the main VE table in closed loop you are forced to guess what values to fill in the higher resolution Main table.

No realtime tuning-short of a custom Moates 98 setup. No offense Craig...this could actually be a prime potential customer for a 98 Road Runner. Overseas, not that many LSx based cars around, limited need, sole user/ owner.

Real time tuning will propell your EFI learning curve by galatic proportions. You will actually see how the pcm responds to your inputs with direct results. You will find out that the pcm "samples" all adjacent cells in tables to come up with end resultants and will get your car to run better than the factory ever dreamed.

I feel for your situation being a 98 owner myself. All of my comments made are purely my own experience. I am not on anybodies payroll.

Given your overseas situation, and depending on how comfortable you are with wiring, the least amount of hassel for Real Time Tuning is a Moates Road Runner(Plug and Play).

If have access or skills to do wire/component swaps then you have both EFI Live and HP Tuners to choose from... (provided you upgrade to 99+up for HP Tuners.) Moates RR is the only RT tuning for 98s

tici

iTrader: (1)

Good explaination, thanks.

MAF: it actually goes up to 11250 Hz, is it that wors than 12000?
11250 means 439 G/sec and even with the blower I never maxxed it out (I never saw more than 356 G/sec).

IFR: I don't understand what you mean.

For the rest: ok, I can imagine that a newer, faster PCM with another program would be better. But I honestly prefer to keep it as it is.
This is my daily drive and I already spent too much time and money in it.
The next one will be something more serious (a C6 or so), and then I'll may start up with new tools.

I'm an old scool guy :Autotap + LS1Edit + Wideband + a lot of Excel . I never screw up the engine and I was able to learn to "tune" it with decent results.
I tried VE, MAF, calculated IFR curves... and honestly: the measured IFR curve based on LTFT and STFT gave me the best result.
AFR at WOT is constant too.

The only variation is winter summer: in winter it's out of just 2-4%. Not too much. But I wanted to know about the experience of the other members.