I am about to swap a motor in my car to turbo, and im wondering will my set up be to much for the stock mass air? I have 460cc injectors, safc1, sr smic, log manifold, 2.5 inch down pipe to 3 inch exhaust, and t3/t4 t04e I will be boosting around 7-8lbs of boost. will this be to much for my stock mass air flow?

Much over 8psi and you'll max out the MAF. Get a 300ZX MAF, thats what I did.

You are fine, you dont need a z32 mafs. You can get a better tune using the stock mafs with lower hp numbers, and 7-8psi wont be much over 220 to the wheels im betting. Stock maf is good to ~275hp ive heard.

8-9 psi on my t3/t4 and stock mafs was at its limit. If you are looking to go any higher than 8 psi down the line switch to a z32 now.

Does the AFC have the option to use a MAP? I use MAP with the E-Manage and have rock steady AFR's at 11 psi

nope, emanage only. My favorite feature.

the only thing you can max out is the actual diameter of the MAF, if you are pushing so much air into it that it becomes restrictive. That shouldn't happen until 300whp, because it is around 2" in diameter and that would mean that your FMIC piping is also maxed out, since it's usually around 2-2.5" (unless you run 3" FMIC piping).When you are at WOT, and your MAF is actually electronically maxed out, you can still add fuel with the SAFC, but you should probably do so with a wideband or a dyno.

When the stock MAF is maxed out it'll just read out the maximum air that it can possibly let go throug it, but since that has already happened when you boosted less than 8psi (In fact ANY boost is already more than the stock MAF can account for, since it's made for vacum only), it doesn't matter anyway.

sil80

sil80drifter wrote:When the stock MAF is maxed out it'll just read out the maximum air that it can possibly let go throug it, but since that has already happened when you boosted less than 8psi (In fact ANY boost is already more than the stock MAF can account for, since it's made for vacum only), it doesn't matter anyway.

sil80

umm well if hes running the stock mafs, then the mafs never actually sees positive air pressure, (boost) its before the turbo, which it would read vacuum only not boost. with the turbo on the car and the increased airflow that the engine sees, the mafs just sees a larger draw of air.

sil80drifter wrote:the only thing you can max out is the actual diameter of the MAF, if you are pushing so much air into it that it becomes restrictive. That shouldn't happen until 300whp, because it is around 2" in diameter and that would mean that your FMIC piping is also maxed out, since it's usually around 2-2.5" (unless you run 3" FMIC piping).When you are at WOT, and your MAF is actually electronically maxed out, you can still add fuel with the SAFC, but you should probably do so with a wideband or a dyno.

When the stock MAF is maxed out it'll just read out the maximum air that it can possibly let go throug it, but since that has already happened when you boosted less than 8psi (In fact ANY boost is already more than the stock MAF can account for, since it's made for vacum only), it doesn't matter anyway.

sil80

Way Wrong. Flow is always a function of pressure differential. The higher the pressure differential, the more flow. A hot-wire MAF maxes out when the MAF can no longer heat the hot-wire to the temperature it is supposed to maintain. Since a MAF measures the voltage required to maintain the hot-wire temp, when airflow becomes so high so that the MAF can not provide enough current to do this, the MAF is maxed out. The signal maxes out at at least 5 volts. I speculate it's slightly higher based on some observations I made when I ran an e-manage on my S14.

And boost, in that of itself, does not max out a hot-wire MAF. Even if you ran the MAF as a blow-through(in the pressurized pipes), it would still read the actual Molecular mass of air. A hot-wire MAF works by essentially measuring how much heat the air takes away from the hotwire, it automatically accounts for pressure, density, temperature and flow.

So if that is true, then the stock MAF will keep telling the ECU that that is more air coming in under boost than under NA conditions? What does the ECU do? Increase fuel? You knwo what I mean? Like if the max voltage under NA condition would be 3volts, and when you boost it goes up to 5 volts, would the ECU be able to compensate for it? I'm thinking no, because it's only programmed for NA conditions... Right?

What I was actually referring to is that "maxing out" the MAF electronically (voltage at the max), does not mean you are maxing it out volumetrically, which to me would be the only reason to replace it with a bigger diameter 300ZX unit. Just because you maxed it out (and I think it should get maxed out prety quick if you are boosting), doesn't mean you can't still put more fuel into the engine using a piggyback or standalone, as long as you know that you ARE beyond the MAFs limits and you need to use a windeband/dyno as your guide for how much fuel is needed.

sil80

Modified by sil80drifter at 2:33 PM 3/27/2005
Modified by sil80drifter at 2:34 PM 3/27/2005

sil80drifter wrote:So if that is true, then the stock MAF will keep telling the ECU that that is more air coming in under boost than under NA conditions? What does the ECU do? Increase fuel? You knwo what I mean? Like if the max voltage under NA condition would be 3volts, and when you boost it goes up to 5 volts, would the ECU be able to compensate for it? I'm thinking no, because it's only programmed for NA conditions... Right?

the mafs isnt programmed for n/a conditions, its programmed to measure airflow. once its on the compressor intake, its just getting more air drawn through it. whenever the mafs flows more, the load value is increased and more fuel is injected.

also....once the mafs is "maxxed out" at 5+ volts, doesnt the ecu cut fuel? i thought ive heard that before.

my friend dynoed 284 whp with a stock maf at nine psi. if ur looking for over 300 whp, get a larger maf.......

I said the ECU is programmed for NA conditions only. So if the MAF gives it voltage beyond what the maximum corresponding fuel points are on the fuel map, the ECU will just dump as much fuel as possible. Hence, my saying that since the MAF will show more airflow under boost than any NA conditons, the ECU will go to WOT map anyway (unless it also cares about load, in which case it'll retard timing AND go to WOT map). So, you're technically maxing out the fuel map at any boost.Hence, the only limiting MAF factor is the size. Hence don't need ZX MAF until you're pushing a lot of air though (like mentioned above, around 300rwhp).Hence... *does little dance* my notion was correct. I just didn't use the right words before.

sil80

sil80drifter wrote:So if that is true, then the stock MAF will keep telling the ECU that that is more air coming in under boost than under NA conditions? What does the ECU do? Increase fuel? You knwo what I mean? Like if the max voltage under NA condition would be 3volts, and when you boost it goes up to 5 volts, would the ECU be able to compensate for it? I'm thinking no, because it's only programmed for NA conditions... Right?

What I was actually referring to is that "maxing out" the MAF electronically (voltage at the max), does not mean you are maxing it out volumetrically, which to me would be the only reason to replace it with a bigger diameter 300ZX unit. Just because you maxed it out (and I think it should get maxed out prety quick if you are boosting), doesn't mean you can't still put more fuel into the engine using a piggyback or standalone, as long as you know that you ARE beyond the MAFs limits and you need to use a windeband/dyno as your guide for how much fuel is needed.

sil80

No. The amount of fuel needed for a given amount of air is failry linear. If the MAF registers more air, it will dump more fuel. Likely, it will be fairly conservative and not optimally tuned, but the point at which fuel delivery actually maxes out first will likely be from the injector's limitations. How I know this is because people run the 240sx with stock injectors and a FMU. When I installed an E-Manage on mine, I actually ran it with the FMU for a while to datalog and make sure everything is working before upgrading to larger injectors. The datalogs showed the MAF was hitting 5 volts with only 6.5 PSI. The injectors were maxed at 100% from about 4800 RPM and up which means fuel delivery was at that point dependent solely on the higher fuel pressure from my FMU. The MAF was at 5 volts around the same time.

skatanic28 wrote:also....once the mafs is "maxxed out" at 5+ volts, doesnt the ecu cut fuel? i thought ive heard that before.

No. Since the injectors are maxed at about the same time, the injectors stay open 100% of the time.

sil80drifter wrote:I said the ECU is programmed for NA conditions only. So if the MAF gives it voltage beyond what the maximum corresponding fuel points are on the fuel map, the ECU will just dump as much fuel as possible. Hence, my saying that since the MAF will show more airflow under boost than any NA conditons, the ECU will go to WOT map anyway (unless it also cares about load, in which case it'll retard timing AND go to WOT map). So, you're technically maxing out the fuel map at any boost.Hence, the only limiting MAF factor is the size. Hence don't need ZX MAF until you're pushing a lot of air though (like mentioned above, around 300rwhp).Hence... *does little dance* my notion was correct. I just didn't use the right words before.

sil80

That is not what you said. You referred to a physical max point due to the maximum flow that can actually make it through the MAF. The fact is you can flow a lot more air through the MAF than it is able to measure.

The ECU is certainly optimized for N/A. But it will read the additional airflow from a turbo until the MAF maxes out. And up until that point, it will add additional fuel. It has no idea the turbo is on there and frankly, it doesn't care. At WOT, the WOT program you refer to will still compensate for the amount of air read by the MAF. The only thing it ignores is the Closed-loop feedback of the O2 sensor, which means it is not trying to fine tune the mixture and adjust injector pulsewidth accordingly to try and obtain a certain A/F ratio. The 270cc injectors will max out at about 4-5 psi. While the ECU may not be optimally tuned for boost up to the MAF's max voltage, it will, however, add close to the right amount of fuel up until you reach the point where the signal to the injectors reach 100% duty cycle. So technically, you are not maxing out at any boost.