Why 300zx MAF are important on RB26?

[cobrAA]

Why people change to 300zx MAF? I always thought the RB26 was the ''top', from Nissan. So why would skyline owner need to use 300zx parts..

Again, I plan in the future to swap my turbo in order to increase my PSI and have a btter feeling when driving my GTR. Should I need those MAF?

P.S: Someone has the part # of that MAF?

[Daryl @ RightDrive]

The Z32 MAF sensors are rated for higher flow. The RB26 MAFs are rated up to around 450hp, and the Z32 and Nismo MAFs are rated up to around 650hp.

The Z32 or Nismo MAFs are 36,750 JPY each.

[Skym]

Bigger turbo's or higher boost levels tend to make turbo suck more air in, so make stock MAF voltage max out earlier. Also stock MAF's can max out if it's a cold day, night while running higher boost levels due to cooling hotwire inside MAF more.

MAF works by incoming air from podfilters that cools hotwire sensor. The MAF reheats this hotwire and measures the voltage needed to do this. That voltage is sent to ECU, which is then converted (software wise) by a table to a load figure. The ECU uses this load figure to select the correct load cell on ignition, fuelmaps, which it then injects a certain amount of fuel or has a certain amount of ignition timing. If MAF voltage maxes out, ECU uses the highest load cells on ignition, fuelmaps, which might be not rich enough (engine leans out) with fuelmaps for the higher boost levels. With higher resolution MAF it keeps within the map load cell limits.

Z32 MAF is calibrated differently, so more air = less voltage and is 80mm vs GTR MAF's that are 65mm. Also the 80mm diameter allows more air to enter turbo's. There's a dynoproven 6awkw (8rwhp) gain after retune of ECU when switching to Z32 MAF's from stock GTR MAF's.

Z32 MAF is rated to around 480hp at engine. Times 2 MAF's that's nearly 960hp. Another common upgrade is RB20DET or RB25DET 80mm MAF x 2, but are only rated to 300hp per MAF.

[BlackAura]

Wow Skym....you really do know everything....always wondered how they determined the air flow rate electrically, thanks!

[Skym]

Na, don't know everything.

You can see ECU hit the higher load cells when engine is transistioning to boost in a higher gear (more load on engine) with tuning software (Nistune). Also you can see exactly what voltage (MAF, etc) that ECU is looking at on every table in realtime.

I gather if hotwire sensor gets dirty (due to oil deposits that attract dirt), it probably would cool hotwire less (less voltage) thus run in the lower load / leaner part of maps and might knock, switch to richer knock maps on ECU and engine runs rough.

I presume when they tune outside the limits of MAF voltage (I think is around 5.1???mv), they run the higher load cells richer than they need to be to make sure engine doesn't go lean. I gather alot of tweeking while monitoring the wideband A/F ratio.

From what I understand MAF hotwire can adjust to less, colder air at altitude due to hotwire being cooled. With MAP setup it measures pressure at intake manifold (converts to voltage that is sent to ECU) and ECU switches between 2x sets of ignition, fuel maps (one set for cold day and one set for extreme hot day) for temperature compensation. ECU gets this temperature information from stock or aftermarket IAT (Inlet Air Temp) sensor. It's either on hot or cold correction maps, no inbetween which affects drivability. Because MAF uses a table graph on ECU to convert hotwire voltage to load, it provides smoother transistion (engine feels smoother / better drivability) between cells in colder / less air environments like high altitudes, cold days, hot days, etc. I presume that's why factory uses MAF instead of MAP.

MAP is good if your aiming for more hp due to removing MAF's that have the restrictive gauze screens. Also if turbo's slow down enough (due to BOV problem making the turbo's or turbo slowdown more) that sends air backwards (known as reversion), towards MAF thus affecting hotwire/voltage readings. But is the extra cost to setup correction maps with MAP setup worth it?? In some cases it might be.

[M13]

are the voltage readings on the Q45 MAFs larger than that of Z32s?

[Skym]

I think they are the same. Ford Lightening MAF (I think is used in supercharged applications) is rated to 700hp and is an option in Nistune for MAF.

[cobrAA]

I'M about to get tuned again and was wondering if 300zx maf were still needed. my tuner tell me its not needed up to about 600whp but then I read Skym's post and I'm wondering if the extra 15mm wouldn't maybe give me another 10-20whp, just for that, I would be interesting in doing the swap.

anyone know more info about the added powergain on 300zx maf vs gtr ?

[NismoS-tune]

3500 posts and you're not sure if they're need? you don't NEED them but the rb26 get limited around 500whp or something? Get some nismo or Mines ones. that's where it's at

[Skym]

From what I understand, you need to look at MAF voltage on ECU side and if maxing out you upgrade MAF. With higher resolution MAF you can tune higher load cells correctly for amount of air entering engine, not run higher load cells rich enough, adjust ignition timing to suit and hope it's rich enough, ignition timing is set correctly if goes off the map. Also the boost cut / load cut stops ECU going off the high load side of maps under higher boost levels. Most people remove or adjust boost cut, but it's a safety feature to prevent engine blowing up. Only time you would adjust it is when upgrading MAF.

Better explanation (better than my explanation) of how MAF circuitry works is here (of the different types of MAF, including hotwire) -

http://www.autoshop101.com/forms/h34.pdf

There's the ECU, IAT part which I didn't mention.

[markdett]

For those interested,

I use to work in a fairly reputable tuning shop here in Perth Australia called Xspeed. We found that the MAP sensors supplied by Apexi in there power FC kit (3bar), would limit the resolution somewhat when tunning higher HP/higher boost engines.

After a bit of research we found out Trust do a 4bar sensor which comes in their boost control kit. Managed to get the part number of just the MAP sensor and ordered up.

To our suprise they use the same connector as the map sensor supplied by Apexi, Just 2 of the wire's are around the wrong way. A quick de-pin/re-pin and we got the ball rolling.

We now have 2 fairly wild animals running twin Trust 4 bar sensors with their power fc. One is making 680hp on twin low mounts (GTX2863's) and E85, and the other is still limitied to 19 psi (because of waste gate spring) but still making 550hp (HKS T51R) on pump gas. Both cars are 2.8 strokers.

[cobrAA]

3500 posts and you're not sure if they're need? you don't NEED them but the rb26 get limited around 500whp or something? Get some nismo or Mines ones. that's where it's at

well I'm past 500whp and theres still fine. I was interesting in the powergain, not the part if its needed or not

[Skym]

From what I understand, power gain comes from correct ignition timing, fueling for amount of air, not guessing what it might be. Also like you have already said, bigger MAF housing = more air into turbo's, engine (get a power gain when removing MAF gauze screens, retuning ECU to suit, but some MAF's supposedly work best with gauze screens due to straightening air out). HKS twin Power DLI is another way to increase spark, hp, if that's what you are after.

[cobrAA]

just trying to get the max potentiel out of my actual setup.

[MattiasJacobs]

Is robin tuning your car? What fuel are you using? I maxed out at 490whp at 1.25bar because of octane (shell v-power). I think robin mentioned something about modding the stock mafs to read more volts.