Finally, I got the 2G MAF installed and refuelled with Husky 94. Took the car out and did some pulls. I tuned it with a wideband and a datalogger. Got the A/F to be around 11:1 and a few counts of knock.

Now, in the evening, I took the car and found the settings I had were richer at some points and giving me higher counts of knock. I thought the 2G MAF was more forgiving then the GM-T when it came to temp adjustments. Was I wrong?

Just thinking out loud here - but maybe now that you have a functioning IAT sensor pre-turbo, the ECU can enrich in the cold by its design.

With the MAF-T you were supplying a translated air volume which was read after the turbo and intercooler, so I expect the fueling would be less adapted to intake air temp.

Basically, now it's behaving more like OEM.
I'm guessing the MAF-T is less forgiving because you would end up lean on a cold day if tuned in the heat.

Also, I wouldn't just yet draw a direct correlation between the extra fuel and the knock. Maybe the knock got the timing pulled and caused the unburnt fuel?

I had this same problem with the MAF-T. When the weather gets colder, the A/F would read richer. I would get up to 20 counts of knock when the weather changes. It's really bothersome.

I thought changing to 2G MAF would solve this problem, but I guess my car is cursed.

How about: The volume of air has gone up, and eventhough you are supplying the necessary fuel there is actually too much timing, so it knocks and the timing is pulled and it shows rich on your wideband.

It's akin to just turning the boost up on the warm day that you are tuned for.

I had the notion that the 2G MAF will compensate for the air density and temp and adjust the fuel delivery once its set. No?

Yes but keep in mind you are running higher than stock boost, so the stock fuel and timing maps aren't quite worth their weight anymore.
The 2G MAF should be more graceful with varying temps, but you still have to tune the fuel & timing to handle the cold weather.

I feel like I just lost the war on DSM.

A hot wire MAF is STILL a MAF. It calculates the MASS of the air going through it.

The GM maf still compensates for air temperature. (I'm amazed at how many times I hear people say they don't) It does it in a different way than the DSM MAF, but it still does it. If you're getting fluctuations in "tune" due to air temp, it's not because you're running a GM MAF.

Thinking out loud on this one: An 02 sensor is basically a thermocouple, correct? If your Exhaust temp is the same, but the outside air temp is colder, wouldn't there be a difference in voltage output between the runs (ie: showing a different A/F ratio)? Or, do they compensate for this somehow?

We can't ignore that the DSM ECU requires an intake air temperature reading for its own calculations.
The MAF-T just clamps that value. So, we are at the mercy of the MAF-T's calculations to properly convert the GM MAF signal to an airflow HZ which is adjusted for the clamped IAT (and Baro) value.
It probably doesn't do a very good job.

On the O2 sensor, I think they actually work on the difference of oxygen levels between exhaust air and atmospheric air, via a chemical reaction. Unless a difference in "under the hood" air temperature has a great effect on oxygen level, I think temperature does not have much to do with it.

Ahhh.. but we AREN'T. A hotwire MAF works on how much current it takes to heat a wire to a specific temperature. (Sort of.. it's based on resistance, but that's sort of what's going on). If the air temperature drops, there is more mass to take heat away from the wire. If the Baro increases, there is more mass to take heat away from the wire(and vice versa).

The Hz signal that the translator outputs isn't "adjusted" for the clamped IAT (and Baro). Both are accounted for before the signal even makes it to the translator.

It doesn't matter if you're using seperate sensors (and some calculations ie: DSM MAF/ECU), or one sensor, to calculate MASS flow. Mass is mass, any way you calculate it.

The temperature is not accounted for in the Translator part of the MAF-T set-up, it's accounted for at the sensor itself. The ONLY reasons the Translator "clamps" the IAT and Baro inputs are 1) They aren't needed with a hotwire MAF, they're measured a different way. and 2) so you don't get a CEL when you run a MAFT.

I'd actually guess that the GM MAF is more accurate at giving a correct mass of air than the DSM set-up.

...and this is coming from a guy who didn't like the MAF-T set-up for a long time....

I'm still thinking out loud of course, to understand
I agree the GM MAF should be more accurate, even without the other sensors.
I guess the translation in the MAF-T must be more direct than I had thought.

Would there be no effect to say, adding a resistor to the IAT wire to change it by 10deg?
Why is or isn't 80F a magic number?

//edit
I guess it somehow spits out the right HZ number for 80F at sea level, and it can do so directly from just the GM MAF signal? (basically the same calculation for any car with a karman MAFS)

Now that I am running higher then stock boost and higher fuel and timing map, would it help if I were to change the maps to a higher then stock map? Is this what people do with the DSM link, and change the maps to coordinate with the higher boost and fuel and timing?

Yes, essentially that's what tuning is.
Not really "higher than stock" maps, they're just "different from stock".

If you're using an S-AFC to adjust the fuel, that's only part of the picture. You can run into a situation where no matter what you do with the fuel it still knocks, because the ignition timing needs adjustment too.
For you this might only be happening in the cold when the air is so dense.

Still not understanding this. Even if I remap the timing and fuel, wouldn't I still get knock when the air gets colder and denser, when I tuned for warmer climate.

You'd have to tune it in the cold to get rid of the knock there for sure.

If you had a more conservative boost level and tune in the warm, then it would have less chance of knocking when it does get cold.

Basically, it's knocking because you are not tuned for the larger mass of air that's going in.

Tuning with an SAFC is a little rough since it is only RPM based (not load & RPM like in the ECU).
So, you could tune out the knock in the cold, but that might rob you of some power when it is warmer out.

I'd rather tune it for the warm and then run a little lower boost in the cold, though

Thanx.

I just thought that switching over to the 2G maf would be a lot easier then the MAF-T, meaning, I wouldn't have to constantly tune whenever the weather changes. Just frustrating that when I switched over, I get the same result and issues I've had in the past. The only thing I've noticed is the timing is a lot higher now then before. Last year, the highest timing I could get is about 18 degrees with no knock. Now, I've noticed that the timing is highest at 24 with 5 counts of knock.

No prob!
Arguably, the 2G MAF is easier to tune than a MAF-T in blow-thru.
I'm sure you're among others who have switched back.

Hmm.. you raise some good points. Changing the IAT/BARO "clamped" values WOULD affect the car because the ECU uses these in it's calculations to figure out mass.

It would appear that we ARE more at the "mercy" of the translator's "conversion" than I thought...Although with the mods mjost of us do on our cars by the time we NEED to change the MAF, I'm not sure this is REALLY an issue (it IS adjustable..)

I'm going to think about this some more. For now though, the MAF-T set-up DOES compensate for IAT/Baro. that much I'm SURE of, so if you get it "tuned" at one temp/baro atmospheric changes shouldn't affect it any more than the stock set up.

I have found myself chasing that "perfect tune" a few times. After a while I've decided that "perfect is the enemy of good enough". YMMV.

Gabriel: Are you pulling some airflow signal out with the SAFC?

If you're on the top airflow map (which shouldn't take much) you shouldn't be seeing anything over 20* of timing.

24* with a knocksum of 5 means the ECU is TRYING to get 25*.

Not sure what you mean by pulling the airflow out with the SAFC.

^^^
He means leaning it out, negative % on the SAFC.
You have bigger injectors on the stock ECU, right? So you probably are negative quite a bit, which results in that aggressive timing (since you're not in the top map).

That's exactly what I mean.

Gabriel has a chip with injector compensation, so unless he's gone to something larger than 650s, he shouldn't be pulling TOO much out...

HI,

thanks for clarifying that for me. Yes, I am using 650 or 660's, not sure what L&R racing sent me. I originally ordered delphi 660 but later I was told they were FIC 650's. Anyways, I'm not pulling that much out. On the high setting in SAFCII, I'm pulling about -10 across.

Is the chip also set up for 2G MAF? If not, I wonder if that has something to do with it... Although then I think he'd have to add some fuel. So even if it's closer to zero that could be more lean & lots of timing compared to "stock".

Yes, the 2G MAF is in there as well.

What are you using to log, Gabriel? Can you send me one?

I'm using the MMCD datalogger v8. I can't seem to get the datalogger to syn with my computer. I'll try again when I get home from work.

RPM TPS TIMA O2-R MAFS KNCK INJP AIRT
1563 32.9% 33° 0.02V 81.8Hz 0 3.84ms 25.6°C
1781 34.5% 29° 0.02V 88.1Hz 0 4.10ms 26.9°C
1969 27.5% 31° 0.04V 88.1Hz 0 3.84ms 27.8°C
2156 23.1% 33° 0.76V 88.1Hz 0 3.33ms 28.7°C
2313 21.2% 35° 0.84V 69.2Hz 0 2.56ms 29.1°C
2375 21.2% 37° 0.14V 69.2Hz 0 2.82ms 29.1°C
2500 21.6% 37° 0.45V 69.2Hz 0 2.82ms 29.1°C
2563 22.0% 37° 0.76V 75.5Hz 0 2.56ms 28.7°C
2656 21.2% 37° 0.76V 75.5Hz 0 2.30ms 28.3°C
2469 10.6% 38° 0.94V 25.2Hz 0 1.28ms 27.4°C
2063 23.9% 38° 0.92V 50.3Hz 0 2.82ms 26.9°C
1781 33.7% 30° 0.02V 88.1Hz 0 3.84ms 26.5°C
1875 27.1% 30° 0.02V 88.1Hz 0 3.58ms 25.6°C
1969 24.3% 32° 0.06V 81.8Hz 0 3.58ms 24.8°C
2031 24.3% 33° 0.78V 81.8Hz 0 3.58ms 24.3°C
2094 24.3% 33° 0.74V 81.8Hz 0 3.58ms 23.9°C
2156 24.3% 34° 0.74V 81.8Hz 0 3.33ms 23.4°C
2219 24.3% 34° 0.76V 81.8Hz 0 3.33ms 23.0°C
2313 24.3% 35° 0.78V 88.1Hz 0 3.33ms 22.6°C
2438 24.3% 36° 0.18V 88.1Hz 0 3.33ms 21.7°C
2469 24.3% 36° 0.16V 88.1Hz 0 3.33ms 21.7°C
2531 24.3% 36° 0.14V 88.1Hz 0 3.33ms 21.3°C
2594 24.3% 36° 0.16V 94.4Hz 0 3.33ms 21.3°C
2719 100.0% 31° 0.90V 195.0Hz 0 6.66ms 20.8°C
2906 100.0% 29° 0.90V 251.6Hz 0 7.68ms 20.4°C
3156 100.0% 27° 0.88V 320.8Hz 0 8.96ms 19.9°C
3438 100.0% 24° 0.88V 440.3Hz 0 13.06ms 19.5°C
3844 100.0% 18° 0.90V 572.4Hz 7 15.10ms 19.1°C
4219 100.0% 18° 0.90V 622.7Hz 8 15.62ms 19.1°C
4594 100.0% 16° 0.90V 691.9Hz 7 15.87ms 18.6°C
4844 100.0% 19° 0.90V 704.5Hz 6 15.10ms 18.2°C
5188 100.0% 21° 0.90V 748.5Hz 5 15.87ms 18.2°C
5375 100.0% 20° 0.90V 798.8Hz 5 16.13ms 17.8°C
5594 100.0% 19° 0.90V 842.9Hz 4 16.38ms 17.3°C
5844 100.0% 21° 0.90V 880.6Hz 4 16.13ms 17.3°C
6094 100.0% 25° 0.88V 905.8Hz 4 16.13ms 17.3°C
6219 100.0% 24° 0.88V 924.6Hz 3 16.38ms 16.9°C
6594 100.0% 23° 0.88V 956.1Hz 2 16.13ms 16.4°C
6688 100.0% 22° 0.88V 968.7Hz 2 15.87ms 16.4°C
6938 100.0% 20° 0.88V 968.7Hz 1 15.62ms 16.0°C
7188 100.0% 20° 0.88V 981.2Hz 0 15.10ms 16.0°C
7313 96.5% 21° 0.88V 968.7Hz 0 14.59ms 16.0°C
6063 10.6% 35° 0.59V 1088.2Hz 011.78ms18.6°C
5281 99.6% 31° 0.88V 647.9Hz 0 14.59ms 18.6°C
5438 100.0% 12° 0.88V 824.0Hz 0 16.64ms 17.8°C
5500 100.0% 23° 0.88V 780.0Hz 0 15.10ms 17.3°C
5594 100.0% 26° 0.88V 798.8Hz 0 15.62ms 16.9°C
5719 100.0% 25° 0.88V 842.9Hz 0 15.87ms 16.9°C
5719 100.0% 24° 0.88V 861.7Hz 0 16.13ms 16.4°C
5875 100.0% 25° 0.88V 861.7Hz 0 15.87ms 16.4°C
6000 100.0% 26° 0.88V 893.2Hz 2 16.13ms 16.4°C
6094 100.0% 26° 0.88V 912.1Hz 1 16.13ms 16.4°C
6125 100.0% 24° 0.88V 918.3Hz 1 16.38ms 16.4°C
6281 85.5% 26° 0.88V 930.9Hz 0 16.13ms 16.4°C
6344 33.3% 27° 0.90V 509.5Hz 0 6.91ms 16.9°C
6125 10.6% 41° 0.60V 880.6Hz 0 8.70ms 19.9°C
6063 10.6% 32° 0.64V 320.8Hz 0 4.86ms 19.9°C
5938 10.6% 45° 0.60V 31.5Hz 0 1.28ms 19.9°C
5875 10.6% 45° 0.57V 25.2Hz 0 1.28ms 20.4°C
5781 10.6% 45° 0.57V 25.2Hz 0 1.28ms 20.4°C
5719 10.6% 45° 0.59V 25.2Hz 0 1.28ms 20.4°C
5500 10.6% 45° 0.59V 25.2Hz 0 1.28ms 20.4°C
5469 10.6% 45° 0.59V 25.2Hz 0 1.28ms 19.9°C
5375 10.6% 45° 0.60V 25.2Hz 0 0.00ms 19.9°C
5281 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
5125 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
5063 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
5031 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
4906 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
4844 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
4719 10.6% 32° 0.00V 25.2Hz 0 0.00ms 19.9°C
4625 10.6% 31° 0.00V 25.2Hz 0 0.00ms 19.9°C
4594 10.6% 31° 0.00V 25.2Hz 0 0.00ms 19.9°C
4500 10.6% 31° 0.00V 25.2Hz 0 0.00ms 19.9°C
4438 10.6% 31° 0.00V 25.2Hz 0 0.00ms 19.9°C
4344 10.6% 30° 0.00V 25.2Hz 0 0.00ms 19.9°C
4281 10.6% 30° 0.00V 25.2Hz 0 0.00ms 19.9°C
4219 10.6% 30° 0.00V 25.2Hz 0 0.00ms 19.9°C
4094 11.0% 29° 0.00V 25.2Hz 0 0.00ms 19.9°C
4094 20.8% 29° 0.00V 62.9Hz 0 1.79ms 19.9°C
4031 13.7% 41° 0.88V 31.5Hz 0 1.28ms 19.9°C
3938 10.6% 41° 0.78V 25.2Hz 0 1.28ms 19.9°C
3906 28.6% 41° 0.72V 106.9Hz 0 2.82ms 19.9°C
3531 10.6% 41° 0.92V 31.5Hz 0 1.28ms 19.5°C
3125 22.0% 39° 0.86V 69.2Hz 0 2.30ms 19.5°C

Can anyone tell me where in the menus the "car selection" is in MMCD? If this isn't selected properly, it offsets the timing by 5*. (Which is what I think is causing the high timing readings.)

I looked it up and it is set properly. It is under the options, preferences. The MMCD is set for DSM at 5' timing.

Hmm.. Should have known it wouldn't be that simple.

What kind of timing is it showing at idle?

I had my hopes up, but crushed when I checked up the settings on the MMCD. The car is idling at around 1400 rpm's (can't get it to lower) and sometimes surges, so it's kind of hard to really know what the timing is at. I had the timing set at 3 degree's last year or the year before when you burned the chip with the 3 degree's lower at the higher timing map range.

Although, from the log you posted above, I'm not sure I'd worry about it too much. A knocksum of 8 isn't too bad. Try adding some more fuel around the 3500 - 4000 range.

Also, it's VERY common for the engine to show some knock when you mash the gas. You'll almost never get a "knock free" log when tuning this way. Try "rolling" onto the throttle more, and see if you get different results.

The high idle indicates something else is wrong as well. Have you checked for any disconnected vaccuum lines? Checked for intake leaks?

Thanx. I've been battling the idle problem for years now and I guess I'm just adapted to it now. I've checked for air leaks and replaced the ISC to the 2G. Just don't know what else is left to do.

ok, as for the high idle thing, have you actually done a complete base idle set adjustment and base timing set? EG, car warmed fully, air off, in neutral, lights off, stereo off. Then ground the pin behind the battery. Then set the timing, then set the idle speed?

As well, have you checked that the idle stop switch is adjusted correctly? IE, it JUST opens the throttle plate and just turns the switch on? If its too far screwed in, it holds the throttle plate open too far and it will NEVER idle any lower.

Third thing to look at is if the throttle cable is too tight. Even if it looks a bit slack, its probably a bit tight. If you can manually close the throttle a bit more, then you need to loosen the 2x10mm bolts on the intake manifold and slide the cable stay a bit more towards the throttle body. And don't worry about it being too loose, you can go way way over and still have full throttle. I've seen this many times and the idle stop switch one a few times too.

now, onto the knock problem.

2 things. how long has it been since you did a real good decarbonization? Like, lots of chemical(GM Kleenz or MCCC)sprayed into a hot engine, and then lots let sit overnite in the chambers. then the next day, warm it up, the spray lots of water mist into the throttle body, at least a liter of it in a fine spray. If its carboned up in there, its gonna be hard to control knocksums.

the other thing is, I am not sure if people know you are running 9:1 compression. This will change your basic tune a good bit. you simply may have to run lower timing, peroid.

As well, -10 in the safc is a fair amount of extra timing added. if you need that much fuel to be pulled, get it burned in your chip. You don't need much less timing, if you are under 10 counts of knock, and a clean engine along with a couple of degrees of timing would do it I would think.

I have pretty much have done everything on your list John. I've used Seafoam to carbonize and the timing is set at 3 degrees. I have also set the higher end of the timing to reduce 3 more degrees on the ECU. Also using water injection kit with methanol to help clean the cambers.

Is the Idle stop switch on the throttle body, with a little clip? If so, I had a friend of mine come help me set that to the correct voltage.

Either then that, I have no clue why my car is acting the way it is

Did you do a thorough cleaning of the TB? Cleaned out the carbon build up?

I had the high idle as well. Grounded the ISC and followed the VFAQ and it was idling high. Took the TB and cleaned the funk out of it and i dont have a high idle anymore.

The TB is pretty clean. Replaced the seals as well. I guess I pretty much got used to the high idle and surge cuz it doesn't bother me anymore. LOL.

its not a correct voltage issue on the throttle stop switch. its either on or off

You can check this with a logger, or just a test light. If its too far screwed in, it holds the throttle plate too open and you will never get the idle down.

And did you physically check that the throttle cable is not too tight, by actually manually moving the throttle closed more?

I didn't physically check the throttle switch. I looked at the SAFC II reading and the datalogger to see if it was closed or not when I adjusted it.

As for the Throttle switch, I think i might be talking about something different from what you are referring too. The plug on top of the TB that has a ground wire?

Like Rob says. I tune with a 3G maf and run into the same thing thing in cooler weather with a knocksum of up to 12 which pulls 4 degrees of timing. I think if we were able to fillup with 98 octane that the europeans get to it would solve that problem or at least minimize it. Blame the bastard that decided for us that we go from 100 octane leaded in the 70's to 94 octane today.

Nah, if we had 98, we would tune the fuel and timing for 98 on a hot day - and here we go again!

Or tune it for 98 on a cold day, and don't worry about the resulting conservative hot day tune because we're making the same or more power? But I want all the power!