MAP vs. MAF

[Legacy777]

So I'm starting to get things together for the Link install and I'm thinking more about the downside to MAP based systems and how if you change any part on the engine that effectively changes the engine's volumetric efficiency, you really should have the car retuned.

So for example, if I put a borla header on, I would need to have the car's tune adjusted more then likely. Verses, if I use a MAF based system, the system adjusts for itself.

Beyond the restriction issue, and possible range issues of the MAF sensors, what other downsides would there be?

What would be so wrong with getting an STi MAF sensor and using that to calculate engine load?

Thoughts or comments?

Thanks

[PhyrraM]

I would stick with the MAF. Because your going with a standalone it's easy to choose one that is large enough to encompass your future goals. Going big would eliminate the 'restriction' that many talk about when comparing MAP to MAF.

There are many off-the-shelf MAFs that can support 400+ horsepower. Fords (Cobra, DOHC Lincoln) and Nissans (300z, Q45) can be cheap. Many of the Nissans can even be bolted to the stock location if desired.

The only real advantages I can see for going MAP are (1)when desiring a non-recirc BOV and (2)if your worried about being able to drive the car if a intercooler hose blows off. I suppose you might have to pay attention to intake design with some MAFs to avoid "bad flow" that can cause some MAFs to lose resolution.

[93forestpearl]

Even with a mAF based system you'd still want to do some datalogging after doing any breathing mods. They are flexible, but they don't completely account for changes. There's a reason companies like Cobb and whot not have different maps for various mods, even when staying MAF based. For instance, their "Stage 1" is on essentially a stock car. Their "Stage 2" map is when you add a TBE. And so on. I originally thought that a WRX ECU, sicne it's MAF based, could account for a 257 shortblock. I ended up getting chastised for giving the ECU that much credit.


Both work fine. A speed-density will be more legwork in the beginning to get your air temp compensations dialed in.


In the end, there are ups and downs to each style of engine management. Almost every Honda ever made is speed-density. Its the other way around for Subaru.


For my setup, I like speed-density. Its not everyone's cup of tea though. I tune all my own stuff so I don't mind tweaking things if I have to. I haven't felt the need to enable the 4D fuel overlay map just yet. My car runs fine and I've had no tuning related issues thus far.

[Legacy777]

Thanks for the comments, and I do agree with you Dan on not trusting that the MAF sensor will accomodate all mods.

I will be having the car tuned initially, so if there's any difference in tuning, I'd probably go with what they're familar with.

[tmarcel]

MAF systems can be forgiving but are a PITA compared to a MAP set up. MAP is so stupid easy and you never run into problems like turbulent airflow around the sensor as can happen with MAF set ups. MAF setups from the factory have tons of man hours into housing design.

The voltage vs airflow scaling isn't that bad but still more time consuming than a nice MAP install. The best MAP set up is MAP against TPS. A very basic MAP setup will go dry or wet fuel (intake manifold) making tuning difficult.