Cobb AccessPORT Discussion
03-07-2009, 10:16 AM
#5377
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What type of percentages should the primaries be scaled by when making adjustsments?
Is it ever necessary to make adjustments to the injector latency?
Is it ever necessary to make adjustments to the injector latency?
03-07-2009, 11:35 AM
#5379
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In simplistic terms: Volumetric Efficiency.
The ratio of the theoretical mass flow of the engine at that RPM based on it's displacement in naturally aspirated form, compared to the actual mass flow.
So if the engine takes 300 g/s at 6000 RPM, and you are seeing 150 g/s, then the engine is being held back by the throttle. In this case it would be at 50% load.
Cheers,
Hymee.
The ratio of the theoretical mass flow of the engine at that RPM based on it's displacement in naturally aspirated form, compared to the actual mass flow.
So if the engine takes 300 g/s at 6000 RPM, and you are seeing 150 g/s, then the engine is being held back by the throttle. In this case it would be at 50% load.
Cheers,
Hymee.
thats what i thought however every time i do the math and compare it to the load the pcm is spitting into my AP - they do not match
03-07-2009, 11:59 AM
#5380
...and BARO comp and IAT comp and ECT comp..
etc.
BTW - I know this is condescending and I know it will be taken as some sort of nefarious suggestion aimed at quashing "competition" or something or other, but if you don't have an innate "feel" for what is going on in these calculations and how the scaling and curve shaping affects engine output, you probably are not going to ever "get it".
You will just find yourself running in ever tighter circles, trying to wrap your head around the numbers and getting more and more frustrated as seemingly simple and carefully crafted and calculated inputs yield wildly varying and often contradictory outputs from the motor.
Mazda (Denso) gave us a wonderful tool with which to correlate sensor inputs and produce actuator outputs. It is very precise and has so many overlapping layers that, like Photoshop, is able to produce a very nuanced result.
However, unlike Photoshop, there are no "filters" or "actions" that do some of the magic for you and crafting a decent calibration is a bit like trying to edit in Photoshop using a 10-year-old CTX CRT monitor with an intermittent red gun and a ton of gamma error and barrel distortion.
You have to do a LOT of creative mental correction to the absolute numbers to produce a result that will be correct in the "real world".
etc.
BTW - I know this is condescending and I know it will be taken as some sort of nefarious suggestion aimed at quashing "competition" or something or other, but if you don't have an innate "feel" for what is going on in these calculations and how the scaling and curve shaping affects engine output, you probably are not going to ever "get it".
You will just find yourself running in ever tighter circles, trying to wrap your head around the numbers and getting more and more frustrated as seemingly simple and carefully crafted and calculated inputs yield wildly varying and often contradictory outputs from the motor.
Mazda (Denso) gave us a wonderful tool with which to correlate sensor inputs and produce actuator outputs. It is very precise and has so many overlapping layers that, like Photoshop, is able to produce a very nuanced result.
However, unlike Photoshop, there are no "filters" or "actions" that do some of the magic for you and crafting a decent calibration is a bit like trying to edit in Photoshop using a 10-year-old CTX CRT monitor with an intermittent red gun and a ton of gamma error and barrel distortion.
You have to do a LOT of creative mental correction to the absolute numbers to produce a result that will be correct in the "real world".
Last edited by MazdaManiac; 03-07-2009 at 12:10 PM.
03-07-2009, 03:42 PM
#5385
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03-07-2009, 03:47 PM
#5386
Set the target lambda to 1 = 14.7 AFR.
But use lambda makes math easier. Then go find a level place where ou can load your car to 4500 rpm or so and hold it for 20 seconds. Note the actual lambda and adjust the maf scale by the % deviation.
So if you load it to 4500 and your average lambda is 1.1 and you are aiming for 1 - then just add 10% to your MAF scale at that voltage point.
Repeat for as many scales on the MAF as you can.... if they all trend the same way you can make some educated guesses about how to scale the MAF... IE if 1.1,1.2,1.3..... all the way to 1.6 volts are all off by 10% you can be pretty confident that scaling the whole MAF 10% will get you closer than your stock calibration.
But use lambda makes math easier. Then go find a level place where ou can load your car to 4500 rpm or so and hold it for 20 seconds. Note the actual lambda and adjust the maf scale by the % deviation.
So if you load it to 4500 and your average lambda is 1.1 and you are aiming for 1 - then just add 10% to your MAF scale at that voltage point.
Repeat for as many scales on the MAF as you can.... if they all trend the same way you can make some educated guesses about how to scale the MAF... IE if 1.1,1.2,1.3..... all the way to 1.6 volts are all off by 10% you can be pretty confident that scaling the whole MAF 10% will get you closer than your stock calibration.
03-07-2009, 03:51 PM
#5389
Well yeah they dont always scale together.... but you can test as many as you can in the cruise range. You can keep scaling all the way from 0-5v - but for us boosted folks that can be a bit dangerous..... LOLZ
Ultimately you will scale the whole MAF; but to get the higher portions closer to actual you want to start down low where it is safer.
Ultimately you will scale the whole MAF; but to get the higher portions closer to actual you want to start down low where it is safer.
03-07-2009, 04:10 PM
#5396
If you are scaling the injectors first; how do you know your MAF is accurate in order to scale it?
I was recommending idle because every RX8 I have ever plugged into all idle at 5.5-6 g/sec.... so if your MAF reading is accurate (in that range) and your fuel trims are still off; I would chalk it up to an injector scale issue.
I was recommending idle because every RX8 I have ever plugged into all idle at 5.5-6 g/sec.... so if your MAF reading is accurate (in that range) and your fuel trims are still off; I would chalk it up to an injector scale issue.
Last edited by Kane; 03-07-2009 at 04:16 PM.
03-13-2009, 02:22 PM
#5400
Recently I installed a AEM intake, RB header, and catless midpipe with this setup I would think that my STFT and LTFT would be way out to lunch but they are not. My STFT bounces around from -11 to +4 while my LTFT is 0 throughout the rpm band. Does this sound right? I'm running the Cobb stage 1 map because it seems to run better than the stock map. The only thing that I see that isn't right are that my AFR's are in the 11's at high rpm's.