Just got in new 4" calibrated MAF ->
10-20-2003, 07:44 PM
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Just got in new 4" calibrated MAF -> Which should be able to meter all the air my s-trim can pump out - it's a PRO-M 4" Univer, and I have a calibration for it up to 800 g/sec at about 10.5 kHz. (Have exact values of course - it calibrated out very nicely).
Just need to do the divided by two trick and I should be able to meter all the air - negating the need for any PE vs RPM trickery. Plus I don't think the meter will be a restriction
. The holes are actually sampling orifices which go to a vaned tunnel until they get to the sensor - so it doesn't make a large difference what is before the maf (90, straight pipe, filter, etc.) as it does a good job at internal smoothing.
Coupled with LJ's Acceleronics box I think this will allow the stock computer to cope with boost very well - plus MAF is 1000x easier to tune than SD (and much more accurate).
Chris
Just need to do the divided by two trick and I should be able to meter all the air - negating the need for any PE vs RPM trickery. Plus I don't think the meter will be a restriction
. The holes are actually sampling orifices which go to a vaned tunnel until they get to the sensor - so it doesn't make a large difference what is before the maf (90, straight pipe, filter, etc.) as it does a good job at internal smoothing. Coupled with LJ's Acceleronics box I think this will allow the stock computer to cope with boost very well - plus MAF is 1000x easier to tune than SD (and much more accurate).
Chris
10-20-2003, 08:58 PM
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Re: Just got in new 4 So when's the ChrisB maff-tastic special going to start ?
Have you had it on the car yet ?
reason i ask is I'm having all kinds of maff issues set a p101 code and the maff is jumping all over the place and can't figure out why
Have you had it on the car yet ?
reason i ask is I'm having all kinds of maff issues set a p101 code and the maff is jumping all over the place and can't figure out why
10-20-2003, 09:41 PM
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Re: Just got in new 4 Chris,
Does that MAF output a frequency directly, or do you have some electronics between it and the PCM?
Can you provide details on cost...
Does that MAF output a frequency directly, or do you have some electronics between it and the PCM?
Can you provide details on cost...
10-20-2003, 10:42 PM
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Re: Just got in new 4 No, it outputs a 0-5V signal, I built a little converter to swap it over
http://www.slowcar.net/MAF%20Circuit.jpg
from that design I just added a few small caps on the outputs of the Voltage regulators basically. You can use the potentiometer to skew it for ls1 frequency output range easily. Then you just need a voltmeter, power supply, and frequency counter (my DVM did this, plus checked it on a oscilloscope) to determine the voltage vs. frequency function. From pro-m you can get a calibration of flow vs. voltage - then you just swap it over.
The meter retail is about 350 I think. Pro-m also makes a converter box, but it was a bit pricey (250ish I think) - but if you get theirs they will take care of the frequency output calibration and just give you airflow vs. frequency. But then even with a pcb made the circuit above was like 30 bucks in parts.
http://www.slowcar.net/MAF%20Circuit.jpg
from that design I just added a few small caps on the outputs of the Voltage regulators basically. You can use the potentiometer to skew it for ls1 frequency output range easily. Then you just need a voltmeter, power supply, and frequency counter (my DVM did this, plus checked it on a oscilloscope) to determine the voltage vs. frequency function. From pro-m you can get a calibration of flow vs. voltage - then you just swap it over.
The meter retail is about 350 I think. Pro-m also makes a converter box, but it was a bit pricey (250ish I think) - but if you get theirs they will take care of the frequency output calibration and just give you airflow vs. frequency. But then even with a pcb made the circuit above was like 30 bucks in parts.
10-21-2003, 12:26 AM
#5
Re: Just got in new 4 I had a similar MAF on mine before, 3.5" though.
Worked out nicely. My only warning is temperature shift on your V to F. Watch very carefully for it.
I had Pro-M box, it took a ****, i'm not using the Univer or box anymore
It does work though.
Worked out nicely. My only warning is temperature shift on your V to F. Watch very carefully for it.
I had Pro-M box, it took a ****, i'm not using the Univer or box anymore
It does work though.
10-21-2003, 06:09 AM
#6
Re: Just got in new 4
No, it outputs a 0-5V signal, I built a little converter to swap it over
http://www.slowcar.net/MAF%20Circuit.jpg
from that design I just added a few small caps on the outputs of the Voltage regulators basically. You can use the potentiometer to skew it for ls1 frequency output range easily. Then you just need a voltmeter, power supply, and frequency counter (my DVM did this, plus checked it on a oscilloscope) to determine the voltage vs. frequency function. From pro-m you can get a calibration of flow vs. voltage - then you just swap it over.
The meter retail is about 350 I think. Pro-m also makes a converter box, but it was a bit pricey (250ish I think) - but if you get theirs they will take care of the frequency output calibration and just give you airflow vs. frequency. But then even with a pcb made the circuit above was like 30 bucks in parts.
http://www.slowcar.net/MAF%20Circuit.jpg
from that design I just added a few small caps on the outputs of the Voltage regulators basically. You can use the potentiometer to skew it for ls1 frequency output range easily. Then you just need a voltmeter, power supply, and frequency counter (my DVM did this, plus checked it on a oscilloscope) to determine the voltage vs. frequency function. From pro-m you can get a calibration of flow vs. voltage - then you just swap it over.
The meter retail is about 350 I think. Pro-m also makes a converter box, but it was a bit pricey (250ish I think) - but if you get theirs they will take care of the frequency output calibration and just give you airflow vs. frequency. But then even with a pcb made the circuit above was like 30 bucks in parts.
then ls1edit to rescale?
is that right, so your looking at $380 or $600?
10-21-2003, 07:09 AM
#7
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Re: Just got in new 4 Chris, you are an f'ing GENIUS! 
I hope to see you as the billionaire engineering mogul one day on the cover of Times magazine.
Anyway... I could see an 800 g/sec MAF as being a definite help to me. Please keep us aprised.
I hope to see you as the billionaire engineering mogul one day on the cover of Times magazine.
Anyway... I could see an 800 g/sec MAF as being a definite help to me. Please keep us aprised.
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10-21-2003, 07:37 AM
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Re: Just got in new 4 Harlan: Yep, your old setup is what originally gave me the idea for it Thanks for the heads up on the temp variance - I will check that out, and if it's too high I might just swap over to a pic to do the sampling and conversion with. The LM131 is used for the F-V is a military/aerospace part that is *supposto* be fine for the temps the box will see, but I will check it out!
smokinHawk: Yep, that's pretty much it. I think the 350 is retail on the maf - I paid a bit less than that, but I don't know what it generally goes for. 350 was msrp I think, so it should be that for sure, or less.
Black LS1: Thanks, but I have to give Harlan credit for the original idea of using the maf. I'll definitely let you all know how it works out!
The nice thing is on a LS1, if you do the 1/2x airflow trick, the timing tables will now actually scale up to 2x what the say - so 1.4 g/sec would actually be 2.8 g/sec, etc. - so you can effectively scale timing by "boost", or at least airflow/load (which is what you want to do anyway).
Thanks for the heads up on the temp variance - I will check that out, and if it's too high I might just swap over to a pic to do the sampling and conversion with. The LM131 is used for the F-V is a military/aerospace part that is *supposto* be fine for the temps the box will see, but I will check it out!smokinHawk: Yep, that's pretty much it. I think the 350 is retail on the maf - I paid a bit less than that, but I don't know what it generally goes for. 350 was msrp I think, so it should be that for sure, or less.
Black LS1: Thanks, but I have to give Harlan credit for the original idea of using the maf. I'll definitely let you all know how it works out!
The nice thing is on a LS1, if you do the 1/2x airflow trick, the timing tables will now actually scale up to 2x what the say - so 1.4 g/sec would actually be 2.8 g/sec, etc. - so you can effectively scale timing by "boost", or at least airflow/load (which is what you want to do anyway).
