I understand exactly what was being asked and since he asked for the pressure above ambient I gave that to him as well. My original post mean 12-13 PSI is the amount of pressure above ambient that I measured and the flow rate of the compressor at the time it maxxed out was greater then 40 lb/min. I'm not assuming ANYTHING with that statement. I measure the pressure above ambient with a boost gauge and the dyno's map sensor and the flow rate can be easily gathered from the power production at the wheels. My car made well in excess of 400 WHP on that run. The flow rate was actually closer to 48-49 lb/min given the recorded power output at the wheels for 1 lb/min of flow on this motor. And as an FYI I didn't state anything close to max flow on a 60-1. Max flow on a 60-1 full size compressor is 57 lb/min.

 

Just for reference heres a rough compressor map plot of that run...

 

I was stating flow numbers that actually show up on the efficiency islands at a 1.5 pressure ratio (approx. 8 psi) Sure, if you go up to 17.5 psi, you can find 57 lb/min in the far edge of the chart.

I do not wish to further drag this post down and away from its original intentions as we have.



To the O.P., have you thought of trying a big MAF from a Ford Lightning.....I beleive Aubidle Mayhem was able to succesfully get one to work on his 350Z. PM him as to what he did.

 

And I was stating ACTUAL flow numbers as recorded with my car strapped to a dyno not from reading a flow chart and coming up with theoretical numbers. There was no assumption made as the dyno spit out the data for us to look at. [/threadjack]

JWT may have something for you to use. Check this link: http://jimwolftechnology.com/custome...asp?PartID=466

 

Measure the air temperauture inside the plenum............ODB2 ecu reports in grams per second from the MAF voltage.

Agree psi is pretty useless without correcting for density.

 

q45 tech is the the infiniti MAF the same plug as the the 350z? And it would have a temp sensor in it? Would you happen to know the diameter of it.

 

Q45, yes this is consstent my my finding. At 8 psi the car was around 400whp, which is in the 450-500hp crank range for this AMF.

I meant to ask you a question, since you would know. We know that MAF hotwire voltage drop is directly proportional to the mass (or moles) of air getting passed it. How does this change with pressure in whcih the hotwire operates. If you look at all OEM setups that are Fi and utilize the MAF, the locations are all pre-turbo, i.e. the operating pressure of the hotwire is between 0 and -3 PSIg (really dirty filter with the latter). Will a MAF positioned post-turbo still have a consistent voltage vs mass curve.

 

Yes it is and it does. The ID is 2.87".

 

The factory cars that use a MAF sensor preturbo are usually using a bypass valve or none at all so the car doesnt stall. I am going to use a blowthrough MAF with a bov infront of the MAF sensor. I am trying to find one that will plug in and be able to meter around 500hp worth of air at the wheels. One more question what year of q45 should i try and get a maf sensor from? I may try one out from a junkyard.

 

actually, the maf sensors used on teh g35's through teh 5.6L V8 titans are the SAME unit. They only sit in different diameter pipes (4"+ on the case of the V8 titan).

 

The Q45 (late 90s) will not plug directly into your harness I'm sure you'll need to re-wire it. 500hp...I would be running standalone with a map if I were you.

If you insist on running a MAF I would run a Z32 as they flow hella high rates.

 

The Z32 one does not have a temp sensor in it. Im going to use a MAF sensor.

 

Not sure any MAF is designed to flow enough air with a low restriction to allow 500Whp as that would be ~~ 900 CFM [corrected for STD density].

A CF of air weighs ~37 grams so 900CFM = 555 grams per second almost double the normal max design point of most MAF 300 grams per second.

It really depends on how much of the boost you want to waste in forcing the extra air thru the MAF diameter.

If you have 7" H20 drop across a stock MAF and double the flow thru supercharging the pressure drop will quadruple so a full 1.0 psi [27.7" H2O]loss will be the result. Obviously a larger diameter MAF will be required

http://autospeed.drive.com.au/cms/article.html?&A=0652

The OEM early G35 MAF tops out at 4.9 volts flowing 245 g/sec

 

In that article the guy is using a draw through setup. I am going to use a blow through setup, with the MAF sensor in a 3.5"-4" or bigger pipe to slow the air down so it will meter it correctly. Ill look at a titan one day and if its MAF is not built into the airbox i wont have have to worry about making a pipe for it i can get one out of a wrecking yard. MAF works fine under boost, i do not need a MAP sensor. Anyway in a blowthrough setup the air going through it is compressed so it doesnt really matter, if it did you would see people using something like a 5" intake lol.

I used a draw through setup in my merkur with a vane air flow meter and made over 350hp. A vane air flow meter has a spring loaded door in it. Now that is restriction. It looked like this inside.

 

The point of the 6 part GENERIC article was to show how to use a manometer to MEASURE COMPONENTS and to decide what you want to do.

Actually these early flipper MAF were not very restrictive [in the scheme of things] since they were larger than necessary and didn't need protective screens or things [sensor hanging down in the middle of air flow path].


Yep until you exceed 400 HP almost any system will do.

The bulk of the restriction is always in the intake valves at max rpm.

 

Late model Ford Lightning MAF is good for your goals. Its a 0-5v set up and will work. Look on ebay for good deals.

 

I actually had a very long discussion with Sharif about this two years ago. I'm too lazy to find and post the thread link. It was way back when he was a GQ Model. OEM places the MAF pre-turbo because of longevity issues in the old set-ups like on SR20's, and because it reads more accurately that way. Here's why:
The MAF voltage is compared against the thermistor reading from the incoming air. Most MAF's operate on a cross circuit that uses a balanced bridge to determine the proper voltage reading from the cooling air mass. As a result, the air coming in pre-turbo is cooler and of a higher velocity, which is exactly how the MAF is set-up to measure. The air coming out of the turbo is hotter and of lower velocity, and this proves to be less accurate with a MAF. I'll post more later when I have time if any one wants a more detailed description.
Will

 

To the OP: Most are using a Cobra R MAF. It is easy and cheap. SR boards have hundereds of posts about it.
Will

 

The MAF transfer equation is exponential in order to provide good resolution at idle and cruise and wide dynamic range.............after all we are measuring 5 grams at idle and 15 at cruise and ~~255 at max.

MAF are usually calibrated at 70F [lab flow bench] as are all engine parameters.

G35 MAF have an integrated extra air temp sensor to help OBD2 understand summer vs winter vs mountains vs seashore during a hurricane.

It is rare for a stock MAF to see 150-200F air [except summer hot soak crank or AC on traffic jam or CONE FILTER].

I agree that the MAF is probably more accurate mounted on the inlet side of supercharger [any type] especially in summer or any time the air flowing thru it doesn't exceed 100F.

One would need a flow bench and a external air heater to calibrate under hot air conditions.

Most don't understand how much the air is heated by compressing it and that MAF may have a maximum operating temp that is exceed by the pressurized air.

In a hot-film MAF, a foil grid is heated 167 degrees F above ambient air
temperature.

 

Well i logged my car with cipher and the MAF hits 4.48v at its peak somewhere around 6500rpms then trails backdown to around 4.38v. So that tells me technosquare rescales the MAF in the ecu to compensate.