How does Nissan handle the flow from 2 different MAF sensors to begin with? Are there 2 different airflow curves for each MAF?

I am used to tuning Ford and GM cars with a single MAF, but when you change the MAF size or location on either of those applications you just build a new airflow curve for the calibration.

Couldnt you do that with 2 maf's in 1 pipe or is it just one table even though theres 2 MAF's?

The problem is the MAFs would max out their voltage much earlier. Tuning the MAF tables in the ECU just changes how much airflow the ECU interprets the MAF voltage levels as. Doesn't help if you're maxing out the voltage.

Edit: see post below.

I hate MAFs altogether. Give me MAP metering any day!

As someone else pointed out, 2 MAFs in 1 pipe wouldn't work well because they are sized to handle half the airflow and would max out. Even though you can recalibrate them, it would still be a mess.

The air from both intakes (and MAF's) all ends up in the same place. They are not divided inside the plenum/manifold, and the runners are in a row down the middle so they are pulling air from both intakes at the same time as it is mixed inside the plenum. The ECU just sees the air flow (voltage) from both MAF's and calculates the two together as the total amount of air going in. If each intake only went to one bank of (3) cylinders, the OP would have to re-do the piping to have somewhat even airflow to each side. Since the air is mixed inside the plenum, they are going to overcome the issue by allowing more airflow on one side than the other, and upgrading the MAF's to handle more airflow/voltage on that one side that has more airflow (really a band-aide for the uneven airflow, but it will work with the way our intake plenum and runners are setup).

Edit: The above is not correct. After looking at some pics and the service manual, it is split inside the manifold, and the ECU is looking at the MAF signals as Bank 1 and Bank 2.

Ahhhh, DUH! Not having experience with the innards of the plenum I assumed there was some other reason for the dual MAFs. Editing my post above to not spread false info.

So, I was wrong. It does look like it is split in some way, and the MAF's are specifically referred to as for "Bank 1" and "Bank 2" in the service manual. I am assuming that there is something to even out the airflow to each side, but not sure what it is.

Here are some good pics of the inside of the manifold. http://www.the370z.com/diy-section-d...take-swap.html

you could put both sensors in one pipe you just need a larger pipe with twice the flow of a single pipe and tweak in the maps. The reduced velocity from the larger pipe will keep the MAF sensors form maxing. <-- also the piping around the problematic sensor could just be bulged out to do the same thing and keep it from maxing. you don't need new MAF sensors you need a new pipe + tune. Also i'm sure his shop already knows all of this so we could all just shut up and wait for it to be finished?

So are the MAF's represented in the processor tables as Bank 1 and 2 or just 1 whole airflow table?

Exactly, thats how its done on Ford and GM's, A larger diameter pipe will produce a lower voltage reading but with a higher airflow level, but you can still max out the sensor. It just buys you a little more room. If you do this and you still max out the sensor then you still need a re-calibrated sensor.

Well, here's an update for eveyone...

I picked up the car last Thursday. I drove it to work Friday and noticed the oil temps at 250. Saturday, I was running some errands and oil temps were up there again...but this time the coolant temp was 1 dot away from the far right. I also heard the car knocking at around 30mph in 4th gear. It was around noon with temps around 88 degrees. So I dropped the car off again Sunday with Shawn.

He moved the oil cooler to the front of the engine bay and made the air deflector for it. He also made a custom overflow tank because there was air in the system. I picked it up yesterday and drove it straight to S&R to check the tune. We did some street tuning for about an hour or so. Very first LIGHT pull (not even 50% throttle) and there was very noticeable knock. I pull over while the tuner is working on the timing/fuel, so the car sat at idle for about 5 minutes. As soon as there is no airflow to the radiator (aka sitting at idle), the temps shoot up! We were seeing 240 degrees at idle and around 215 degrees when driving. Airflow is key to cooling this damn car!

So we do another 10 minute drive and the tuner adjusts the tune again. I now have 5 of the same fuel maps, but each map differs in timing by nearly 2 degrees. Currently at map 3 (middle aggressive timing), there was no knock. Weird thing is at idle, the AFR will be anywhere from 15.0-12.0. At cruising, same thing...sometimes it's ideal and then a few minutes later at cruising, the AFRs will be in the 12s. My gas mileage is going to SUCK for ZDayz.

So I dropped the car back off with Shawn last night at around 10:30. He said he'd hook up a remote switch so I can turn on the fans whenever, rather than giving the car a headstart to warm up and then the fans kick on. On my way to the shop, it was unusually cool (66 degrees) and the coolant dot never moved from 2 dots to the left of center and oil temps hovered around 200-205. Feeling comfortable with the temps, I did go WOT once and didn't hear any knock. Shawn texted me this morning saying he got his hands on Flex-a-lite fans! Once the cooling issues are taken care of, I'll go with bigger injectors and the upgraded MAFs and a new tune. :driving:

Shawn continues to amaze me with his dedication to making me satisfied with my car. He's going the extra mike to get me on my way to ZDayz...because as of last night, I wasn't going to risk anything and I was going to stay here.

I want to mention that I appreciate everyone's comments/feedback/criticism. This is a learning experience for everyone involved. That's what these forums are for...bouncing ideas off each other and helping the community out. Being that this is a true custom build, I know issues are going go arise... and Shawn has been willing every step of the way to help me out. :tup:


I'm not sure what brand they are. S&R ordered them for me.
Thank you for the reference! With the way the VQ35 motors were, I was under the assumption that the air did disperse from the upper plenum into the lower plenum, then into the runners. It doesn't look to be that way in the VQ37s. The good thing is I was watching the AFRs when we were street tuning and the AFR from each bank is nearly identical. It was off by maybe 0.1 at some points.

That was thought about to, but with the way the hood angles down, Shawn could not fit any piping bigger than the 2.5" piping that runs among the front of the motor.

In the tuning SW I have seen, there is only a single MAF table (total voltage=total amount of airflow). The service manual is not very clear about what the ECU actually does. In the diagrams, it looks like it is eventually treated as a single value. It looks more like the "bank 1" and "bank 2" reference is more for identification of each throttle body.

I thought the same thing based on the VQ35DE, but I was surprised at the way the runners were setup on the VQ37VHR manifold. I am sure the airflow is equalized at some point, and the fact your AFR's were that close indicates that is the case.

Most people use the HPX MAF sensors (this is what UpRev recommends/sells).

Anyway, good luck. I am sure you will get it sorted out. You obviously have some good people supporting you, and these are pretty minor bumps in the road for a custom setup.

Thank you. The HPX MAFs are the only aftermarket ones I've heard of, so I can only assume those are the ones on order.

I think you were right the first time, it's not a huge plenum where you can see straight through to the other side, but I've seen myself, shining a flashlight in one throttle body, and peeking in the other, the light is visible(indirectly) from the other side.

Also, I didn't see in your pics, but where are the bank 1 and 2 wideband O2 sensors? If you have them sharing the same pipe after the two banks merge, the ECU will not like that either. It will try to trim one bank slightly, see no difference between the O2s, trim it more, see no difference, etc. until the banks are off by up to 25% or so.

Are you tuning with UpRev? I know with that you can log the fuel trim levels for each bank to check if something like this is happening.

I always felt you should upgrade the radiator and fans when FI. There's just so much heat generated from are cars in a tight cramp area especially when FI.

There is definitely some shared space in the manifold to equalize the airflow, but there is also a distinct plenum on each side that feeds 3 runners. On the VQ35DE, it was pretty much open space above the runners and a single large plenum (which makes sense with only 1 throttle body).

A/F sensors are in each exhaust manifold/header, and O2 sensors are in the cats. The O2 sensors are not used for engine control, only the A/F sensors. I am pretty sure the O2 sensors are only for emissions purposes and are used to monitor the emissions (cats) performance. You can disable these in the Cobb/UpRev tuning software if you are running test pipes or HFC. I am using the Cobb AccessPort and tuning software. Pretty sure the OP is using UpRev (I will be soon).