Cobb AccessPORT Discussion
03-15-2008, 01:09 AM
#276
03-15-2008, 01:30 AM
#277
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03-15-2008, 08:12 AM
#280
Even with my crappy intake, and 2 5/8" maf tube (see video above), my car idles and drives fine. It only has issues when I accelerate because of it being unable to track the air properly.
Last edited by mysql; 03-15-2008 at 08:16 AM.
03-15-2008, 08:28 AM
#281
03-15-2008, 08:39 AM
#283
I will forever miss my 8!
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03-15-2008, 08:41 AM
#284
I can try it out, but Jeff would once again have to give me new maps since the stuff he sent me was scaled for 3" and then later 2 5/8" maf housings.
The scaling techniques he uses seem to be spot on. Injectors on my car are larger but the car idles and cruses at low speeds at the exact afr's you'd expect.
03-15-2008, 08:45 AM
#285
Finally Boosted!!!!!!!
Can you take a picture of the Greddy MAF tube? I would like to see how it makes the transition from 3 to 3.5 and how long it is. I am still working on my MAF tube and any information is valuable. Thanks!
03-15-2008, 08:51 AM
#286
The large opening has an ID of exactly 3.5"
The smaller side isn't perfectly round, but it's just under 3" wide.
It's almost 5" long.
03-15-2008, 09:12 AM
#287
Finally Boosted!!!!!!!
Yeah, I that seems like it would mess up the MAF readings quite a bit. The transition is too close to the MAF and the 3.5" id is larger than the 3 3/8" ID of the OEM tube. It's probably a good idea to wait on the replacement that Jeff is making for you.
03-15-2008, 09:15 AM
#288
my new intake has a long alumn tube with supposedly a 3.5" ID. If that's true, then whenever Jeff has time to make a 3.5" maf housing map for me, I can test out the greddy intake just to see if it works even a little bit. The intake I have now does not work even slightly - it will not read properly and I cannot go into boost because the car goes spastic rich.
03-15-2008, 09:22 AM
#289
Finally Boosted!!!!!!!
Yeah, I saw that from your video. Doesn't Jeff have a 3 3/8" ID MAF tube? I thought he was using 3.5" OD polished tubing with a 1/16" wall thickness. If so, that matches the ID of the OEM MAF tube pretty closely.
I will post a picture of my MAF tube when I get it. Should be any day now. It was shipped early last week.
I will post a picture of my MAF tube when I get it. Should be any day now. It was shipped early last week.
03-15-2008, 09:27 AM
#290
I'm not using Jeff's maf tubing - I bought mine from TeamRX8... but now that I think about it, he was running with the AP on a custom map, so chances are he would have wanted to replicate the stock intake's ID closely.
03-15-2008, 09:38 AM
#291
Finally Boosted!!!!!!!
3.5" OD with a 1/16" wall thickness is pretty common and easy to get. My MAF tube is supposed to be made from this and its supposed to be 8" long. I will need to cut it down a little but I'm hoping to keep it at least 6". 3"-3.5" before and after the MAF. Hopefully, that gives a good reading because thats about the best I can do in the space I have.
03-15-2008, 03:19 PM
#292
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A mole is nothing more than a number, so by saying moles of air, it's saying you have x number of air particles. So I'm guessing you're just talking about air, being mostly molecules of dinitrogen and dioxygen, are just particles flowing by, colliding with this detector and carrying the heat energy away, so staticlag's description is quite accurate except he left out heat exchange. I don't think the sensor actually measures moles of air. I'm pretty sure the detector doesn't count the number of collisions of these particles, but what do I know.
03-15-2008, 03:37 PM
#294
2005 Ti Gray RX-8 - SOLD
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A mole is nothing more than a number, so by saying moles of air, it's saying you have x number of air particles. So I'm guessing you're just talking about air, being mostly molecules of dinitrogen and dioxygen, are just particles flowing by, colliding with this detector and carrying the heat energy away, so staticlag's description is quite accurate except he left out heat exchange. I don't think the sensor actually measures moles of air. I'm pretty sure the detector doesn't count the number of collisions of these particles, but what do I know.
The 'hot wire' style of mass air flow measurement simply heats a filament (of platinum or some other wire metal) to a prescribed temperature above ambient.
A certain voltage is required to maintain this temperature, as referenced by a thermistor circuit.
Resistance of this wire increases as its temperature increases.
As airflow, (i.e. molecules of the various gases that comprise 'air' of which the thermal conductivity properties [affected by temp, density and humidity, so allows for good mass calculation] are known and assumed) moves over this heated wire, the wire is cooled.... so now, the resistance of the wire is.....you guessed it, lowered.....and therefore, the circuit has to decrease its electrical drive to the wire to maintain that 'prescribed' temperature.
This constant analog swinging of electrical drive to this wire (again, based on the resistance of the wire to maintain a set temperature) is what provides your root mass air flow values, which are then converted to something that your ECU can use in it's fuel calculations, many times a second.
The volume and dimensions of the tube are known, so yes, the whole process in fact does accurately calculate true mass air flow (i.e. Standard Liters Per Minute, moles/hour, kg/s whatever you like).
This is why you want as close to the nicest, smoothest, laminar air flow in the region of your hotwire sensor....for nice and smooth analog sensor behavior.
-C
Last edited by Chamberlin; 03-20-2008 at 01:34 AM. Reason: added more tech info
03-15-2008, 04:05 PM
#295
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The 'hot wire' style of mass air flow measurement simply heats a filament (of platinum or some other wire metal) to a prescribed temperature above ambient.
A certain voltage is required to maintain this temperature.
Resistance of this wire increases as temperature increases.
As airflow, (i.e. molecules of the various gases that comprise 'air' of which the thermal conductivity properties [affected by temp, density and humidity, so allows for good mass calculation] are known and assumed) moves over this heated wire, the wire is cooled.... so now, the resistance of the wire is.....you guessed it, lowered.....and therefore, the circuit has to decrease its electrical drive to the wire to maintain that 'prescribed' temperature
This constant analog swinging of electrical drive to this wire (again, based on the resistance of the wire to maintain a set temperature) is what provides your root mass air flow values, which are then converted to something that your ECU can use in it's fuel calculations, many times a second.
This is why you want as close to the nicest, smoothest, laminar air flow in the region of your hotwire sensor....for nice and smooth analog senor behavior.
-C
A certain voltage is required to maintain this temperature.
Resistance of this wire increases as temperature increases.
As airflow, (i.e. molecules of the various gases that comprise 'air' of which the thermal conductivity properties [affected by temp, density and humidity, so allows for good mass calculation] are known and assumed) moves over this heated wire, the wire is cooled.... so now, the resistance of the wire is.....you guessed it, lowered.....and therefore, the circuit has to decrease its electrical drive to the wire to maintain that 'prescribed' temperature
This constant analog swinging of electrical drive to this wire (again, based on the resistance of the wire to maintain a set temperature) is what provides your root mass air flow values, which are then converted to something that your ECU can use in it's fuel calculations, many times a second.
This is why you want as close to the nicest, smoothest, laminar air flow in the region of your hotwire sensor....for nice and smooth analog senor behavior.
-C
03-15-2008, 04:12 PM
#296
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03-15-2008, 04:54 PM
#297
