Fuel injection -- speed density vs MAF

[VettePilot]

Two things surprised me when looking at the Pilot Service Manuals:
1) The i-VTEC engine in the 2WD Pilot does not have variable valve timing -- it has VCM (Variable Cylinder Management). The 4WD Pilot has variable valve timing.
2) The Pilot does not have a Mass Air-flow (MAF) Sensor.

i-VTEC means many things, depending on the model of the vehicle -- on some models, i-VTEC does have variable valve timing, but on the Pilot 2WD in 2006 it doesn't.

Fuel Injection systems with a MAF are generally considered more accurate. With a MAF sensor, the air ingested into the engine is measured directly by the sensor -- no calculations are needed to determine the air ingested.

Systems without a MAF, but have a MAP sensor and an Intake Air Temperature sensor (along with other sensors), usually calculate the air ingested from these sensors -- this is known as a "speed density" system.
Speed is determined by the RPM and Density is calculated mainly by the intake manifold vacuum and intake air temperature.
The point is: a MAF system is usually considered more accurate in determining the amount of fuel to inject to mix with the air because there are less calculations needed.
However, the Pilot is considered a low-emissions vehicle.

Many, if not most, other manufacturers went from Speed-Density to MAF for lower emissions.
But, the Pilot didn't do this.
I wonder why.

[TheEaglePilot]

Originally posted by VettePilot
Many, if not most, other manufacturers went from Speed-Density to MAF for lower emissions.
But, the Pilot didn't do this.
I wonder why.

The Pilot is already an ULEV (at least my 2007 2WD is) -- no need for extra help, perhaps?

Chris

[whizmo]

This is one of hundreds of complicated engineering tradeoffs made in the design of an engine. Either system can do the job fine. MAF systems are generally superior in their ability to adjust to engine modifications, but in the Pilot, Honda figures 98% of engines remain bone stock so it probably matters little. MAF tend to have a small amount of intake restriction so that's a minus.

With a closed-loop system and multiple O2 sensors, you can get a speed density system to meet very stringent emissions requirements and it probably costs less.

- Mark

[tfrain]

Re the ULEV - my 2007 4wd has is a ULEV vehicle. My 98 civic is just a LEV. Interesting that they can improve an engine so much (from civic to pilot) and it get better emissions while making much more power.

(i know the engines are different - pilot is twice as big and all that, but it is still interesting what they can do nowadays)

[one8t]

MAF based systems are better for tuning but the sensors used can have a short life span. CEL, trip to service, $150-250 bill, unhappy customers. I tune turbo VW's, the simplicity and low maintenance of the Pilot gives me more time and money for the VW!

[jcantanixon]

Originally posted by one8t
MAF based systems are better for tuning but the sensors used can have a short life span. CEL, trip to service, $150-250 bill, unhappy customers. I tune turbo VW's, the simplicity and low maintenance of the Pilot gives me more time and money for the VW!

Welcome to the board! I've also got a 1.8T sitting next to my Pilot in the driveway. There are a couple of other dubbers on here too...