They say it interferes with their program. Interferes how? Ben isn't too informative. Has anybody experienced this?
For reference, I have a 95 Maxima with a V1 blower, 3" pulley (~11.5 psi), 370 cc/min injectors, Z32 maf and the JWT modified ecu.
It doesnt work so well, you tweak the a/f ratio with the AFC, you are also moving where you are in the spark map because MAF voltage is what drives the engines running location in the maps and the AFC works by tweaking the MAF output.
This makes you run in a different cell on the map on the spark side than originaly intended. In extreme cases this can cause engine damage.
Mike
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It doesnt work so well, you tweak the a/f ratio with the AFC, you are also moving where you are in the spark map because MAF voltage is what drives the engines running location in the maps and the AFC works by tweaking the MAF output.
This makes you run in a different cell on the map on the spark side than originaly intended. In extreme cases this can cause engine damage.
Mike
By spark map, do you mean the timing map? So the AFC will have unintended effects on timing as well as afr?
By spark map, do you mean the timing map? So the AFC will have unintended effects on timing as well as afr?
You are correct sir
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Another question: will just having the SAFC connected, but with all the correction factors zeroed out, result in problems? Doesn't seem like it would, unless the very act of cutting the maf wire and routing the voltage through the SAFC is enough to significantly change the voltage the ecu eventually sees.
Any ECU stock or otherwise. Most people don't know how to tune SAFC's and don't even know if their car is running correctly.
Mike
Thanks, Mike.
Do you have any tips, or do you know of any references that talk about tuning with the SAFC?
It seemed pretty straightforward to me, but I'm finding out it's a bit trickier than I thought. For one thing, with Maximas at least, don't bother with low throttle position afr adjustments since the ecu will try to adjust back to what it is programmed to think is right.
Do you have any tips, or do you know of any references that talk about tuning with the SAFC?
It seemed pretty straightforward to me, but I'm finding out it's a bit trickier than I thought. For one thing, with Maximas at least, don't bother with low throttle position afr adjustments since the ecu will try to adjust back to what it is programmed to think is right.
Never tune the SAFC without a correct wideband O2 sensor to reference........I highly suggest only tuning an SAFC on a dyno with wideband support.
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Never tune the SAFC without a correct wideband O2 sensor to reference........I highly suggest only tuning an SAFC on a dyno with wideband support.
I use an Innovate LM-1 with a Bosch LSU4.2 wideband O2 sensor and do my tuning on the road.
Getting back to what morepower said earlier about timing maps. The timing maps I have seen (300ZX for example) show that, in general, for increasing engine load the timing is decreased from the maximum advance (there is an exception at low load and mid-rpm). So if the SAFC is used to increase the maf signal (with the intent of lowering the afr), the ecu interprets that as increased engine load and for the general case will lower the engine advance as well as increase injector pulse width. Is this understanding correct?
Last edited by Stephen Max : Feb 27th, 2004 at 11:08 AM.
Do you have any tips, or do you know of any references that talk about tuning with the SAFC?
It seemed pretty straightforward to me, but I'm finding out it's a bit trickier than I thought. For one thing, with Maximas at least, don't bother with low throttle position afr adjustments since the ecu will try to adjust back to what it is programmed to think is right.
The main thing is not to try to go more than 10% or so or the ECU's long term fuel trim will try to dial it back. Go a lot farther (usualy like 20%) the ECU will think somethings wrong and go into limp home as well.
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There can only be one Icy Hot Stunta, Don't Hate.
I use an Innovate LM-1 with a Bosch LSU4.2 wideband O2 sensor and do my tuning on the road.
Getting back to what morepower said earlier about timing maps. The timing maps I have seen (300ZX for example) show that, in general, for increasing engine load the timing is decreased from the maximum advance (there is an exception at low load and mid-rpm). So if the SAFC is used to increase the maf signal (with the intent of lowering the afr), the ecu interprets that as increased engine load and for the general case will lower the engine advance as well as increase injector pulse width. Is this understanding correct?
well thats on a turbocharged engine, with your Max, the timing table was developed for NA cars and the advance could increse more, not good for your supercharged motor.
Mike
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There can only be one Icy Hot Stunta, Don't Hate.
The main thing is not to try to go more than 10% or so or the ECU's long term fuel trim will try to dial it back. Go a lot farther (usualy like 20%) the ECU will think somethings wrong and go into limp home as well.
That's good to know and explains some odd behavior I've been seeing lately. At WOT, though, when the ecu is in open loop, there is no correction attempt by the ecu, either with afr or timing, right?
If so, the idea then is to allow the ecu to control partial throttle operation by itself without any interference from the SAFC. So low throttle settings are kept zeroed out, and then the threshold value for transition from low to high settings should be set pretty high, say 80%, and then use SAFC high throttle settings to adjust when boosting at WOT.
The difficulty then may be in the 50-80% throttle regime where I do see boost developing, but can't effectively use the SAFC to lower afr. Fortunately that is an area that I can pretty much stay out of if I'm careful. At least for the type of driving I do.
Last edited by Stephen Max : Feb 27th, 2004 at 12:26 PM.
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