[Shotimes] MAF vs. Speed Density

[Don McKinnon (AST)]

It's not just GM, Subura is doing the same thing on many of the post 99
models, cheaper probably has every thing to do wit it I'm sure.   I found
this today on-line:

----
So which is better, MAP or MAF?
While Air-Flow systems are still favored by most manufacturers due to their
accuracy, speed-density systems are slowing gaining favor once again due to
advances in electronic engine management. In order for a speed-density (MAP)
based system to offer the accuracy in A/F ratios to pass the stringent
vehicle certification tests, advanced ECU technology must be used to cope
with the speed-density's inability to optimally handle transient driving
conditions (compared to an air-flow system).
...
The facts remain the same though, the air-flow systems are slightly more
accurate at calculating proper Air/Fuel ratio under a wider variety of
driving conditions. At Wide Open Throttle (WOT) though, they are both very
similar. It's primarily under transient conditions (partial throttle
changes/city driving) where they differ the most. Again, the differences are
primarily in theory and hardly sometime you'll notice by the seat of your
pants. Those of you with speed-density systems don't think your system needs
to be improved by going to a air-flow setup. Keep this comforting thought in
your head; nearly every aftermarket engine management system uses a
speed-density system (ie: Haltech, TEC II, Motec, EFI, etc.).
----

Don McKinnon
95 MTX - White/Mocha 91k miles
Stage 1 Power Package with Stage 1cams
Canyon Carver Road/Race Suspension
Quaife & HiRevs Competition Clutch


-----Original Message-----
From: Kevin & Cheryl Airth [mailto:clubairth@peoplepc.com]
Sent: Wednesday, June 04, 2003 4:38 PM
To: Don McKinnon (AST); shotimes@autox.team.net
Subject: Re: [Shotimes] MAF vs. Speed Density


Don:
 I am surprised that a new motor would have a speed density system on it?

The speed density is cheaper and simpler. Uses less sensors. It usually is a
stop gap setup used after carburetors and before a full on MAF system. Most
aftermarket EFI setups use speed density.

The MAF is a much more precise engine management system. Almost all vehicles
were forced to a MAF system to meet the fuel economy standards as well as
emissions and drivability.

Maybe GM found an advantage going back to the speed density?
.
.

> What are the advantages again of using a MAF vs. Speed Density, if any?
>
> My 2003 Trailblazer XL has a nice motor I wish could show up in a car,
DOHC
> 4.2l Inline 6 with VVT, coated pistons, etc., and uses Speed Density.
>
> Don McKinnon
> 95 MTX