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Discussion Starter #1
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.
 

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Stephen Max said:
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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Discussion Starter #3
morepower2 said:
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?
 

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Stephen Max said:
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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Discussion Starter #6
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.
 

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Discussion Starter #7
Yet another question.

Does JWT reference the throttle position at all in determining afr and timing maps, or are they determined entirely by maf voltage and rpm?

By the way, thanks to all of you for your help.
 

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Sentra_Industies said:
This is only with JWT or simularly reprogrammed ECU's right? Cause I know plenty of people that run SAFC's with no problem at all.

With other cars...who knows bout ours
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
 

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Stephen Max said:
Yet another question.

Does JWT reference the throttle position at all in determining afr and timing maps, or are they determined entirely by maf voltage and rpm?

By the way, thanks to all of you for your help.
JWT's ECU and the stock ECU looks at Throttle position, RPM and MAF voltage.

Mike
 

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Discussion Starter #10
morepower2 said:
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.
 

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Stephen Max said:
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.
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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Discussion Starter #12 (Edited)
chimmike said:
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?
 

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Stephen Max said:
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.
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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Stephen Max said:
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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Discussion Starter #15 (Edited)
morepower2 said:
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.
 

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Stephen Max said:
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.
Thats why I think the AFC is ok to use for a fine tuning device but when used to compinsate for larger injectors, etc, its sort of sketchy. Some people will argue all day about this but they also seem to be the guys that are blowing up all the time as well!

Mike
 

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I'm going to make this a sticky for the time being. It'll stay open as long as it pertains to this subject.

keep in mind, I ran SAFC because JWT wasn't an option for me. It worked, but you always want to go with a better, more thorough option, full ecu replacement or eventually standalone (very expensive)
 

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I was running the SAFC and JWT ECU for about 6 months on my turbo'd 200. I even had it tuned on a dyno, but the car never ran right. I corrected lots of little problems and adjusted everything from timing, tps, spark plug gap to see if that was the issue. It finnaly came down to removing the SAFC. Once I did that the car ran 100% better, the idle was steady, the part throttle acceleration had no hesitation or hick ups, no backfiring and much better gas millage.
Now maybe I never had my SAFC tuned properly, and that may have been the issue, but I read all the posts and did lots of research, and it never worked for me. I wish it did, because the SAFC is one cool piece of hardware
 

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Stephen Max said:
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.
This is what I am wanting to know also. Since JWT ECU's are known to run rich could you just put a correction factor of -5% without having your car run like ass?
 
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