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Basically, use your resistor value divided by 199,500 to get the percentage out will attenuate the signal. Put all the voltage points in excel, then make the column next to it equal the first column divided by that attenuation factor. Then manually move the data word values that correspond to the voltage values for thefirst column to their matching voltage values for the second column. Extrapolate the ones that don't directly correspond. Then load the new curve into uprev and smooth it out. Divide it down until the whole scale fits into the ~65000 value limit and multiply your k value by that divisor.
We really need to find the max voltage of the sensor and start there from the beginning. I requested a datasheet from Hitachi, but haven't heard back.
51k was an arbitrary guess, honestly. If Hitachi can tell me the voltage that the sensor maxes out, we can do something more meaningful in terms of maximum flow. Could be higher, could be lower. I'll update if Hitachi can tell me anything useful. I suspect they're not allowed to give out much info.
Ok, it seems Hitachi only tests the sensors to 5v in a given tube to tune them to the airflow requirements of a particular engine, so they can't tell me what the sensor will max out at.
From some searching on the MAF extenders other cars are using, it seems that we can at least cut the signal by 26%.
so 51kohm is probably the ideal resistor value to get to 26%. and to help extend it even more, we can use a larger tube with 3", maybe even 3.5" I.D. to spread out volume of airflow through the MAF. does that seem correct? or do you think anything 500hp+ should just move to HPX maf?
If the MAF can actually read 8-12v (which is what the MAFia tuner says it can, depending on year), it should be able to do 600+whp in the stock tube. They attenuate the signal by as much as 70% on their max setting. I wouldn't do that much division with just a resistor though, I'd build a proper signal circuit with an opamp and use a pot to control it, which is probably all that $200 box does.
Problem is that the more you divide it down, the worse driveability gets, especially at low load.
I do my own tuning to an extent and can get it running good, idling good and drivable but take it in for fine tuning on a dyno as I dont want to, or know a place to safely street tune and dont have knock amp or headphones and dont want to mess it up. id rather have it tuned in a safe more controlled environment. if it was n/a no problem but not taking risks when f/i and going for 13-14psi. I just would like the maf to be good for 500hp and have some room for error is all.
Is the 199,5k pulldown resistor the same value through all ECMs? Specifically, my 03 ECM?
Tried 40k today on the dyno but we couldn't get the car to run after. It would just start, stumble and die, throttle wouldn't even keep it running. Resistor was installed on the orange wire, which I believe was the center pin on the harness. I didn't have my tools, and was working faster than I should have been because of the $$$ dyno rental. I ended up just taking the resistor out after about 30 minutes of trying to get it to run.
Without the mod I ran out of MAF (5.19v) on the dyno at ~5000rpm, ~10psi. Made 407/348 on a rough tune, and a dynojet that has a tendency to read low apparently. Couldn't do too much after running out of MAF.
It's a vortech with 2.87 jackshaft pulley, 34/28 cog pulleys, added 'GTM' mod, Treadstone TR1045 Intercooler, and a 3" MAF pipe.
I was under the impression I would be good with the stock MAF in the 3" pipe because the 3" pipe increases the range ~20%, I guess not.
Based on my setup, anybody knowledgeable care to comment if running out of MAF at that point seems about right? I was a bit surprised, I thought I'd be good with the 3" MAF pipe. Will this mod be enough, or should I just buy the UpRev MAF?
W/out the resistor I ran out of my MAF at 5300 with stock piping with my prochrager, with the mod I was only hitting 3.8 or something at the same point.
I think U hit same 3.8V at redline... MAF generates voltage output depending of air flow... you didn't change airflow, you only cut voltage output by resistor...
Hi, it worked great!, but now when car is at working temp, it strugles to start, sometimes it won't and I have to wait until it cools down and will start fine...
Before this mod, it always started perfect... Any ideas?
Originally Posted by kilogram
Basically, use your resistor value divided by 199,500 to get the percentage out will attenuate the signal. Put all the voltage points in excel, then make the column next to it equal the first column divided by that attenuation factor. Then manually move the data word values that correspond to the voltage values for thefirst column to their matching voltage values for the second column. Extrapolate the ones that don't directly correspond. Then load the new curve into uprev and smooth it out. Divide it down until the whole scale fits into the ~65000 value limit and multiply your k value by that divisor.
We really need to find the max voltage of the sensor and start there from the beginning. I requested a datasheet from Hitachi, but haven't heard back.
