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Thu May 30 05:48:45 GMT 2013

for aftermarket applications because it is easier, cheaper, more reliable
and requires less work to interface.  A fully mapped speed-density system
(such as the one on my Daimler) can be tuned very satisfactorily on the
road within a short amount of time (including the ignition system).  Of
course, a dyno session is required to get the best out of any system but
I personally haven't bothered yet for my own street car eventhough I have
a full EPA style chassis dyno and emmissions bench at my disposal.

Mass flow system still require a mapping between engine speed and mass
air flow and injector output (which can exist in many forms such as
desired AFR maps and/or volumetric efficiency maps).  In fully tuned form
they perform as well as speed-density systems and are more suitable for
many production systems.  Aftermarket EFI is a totally different matter. 

MAP and MAF sensors are both useless for much serious performance work.
Throttle position is the only reliable method in such cases.

> 2)  I recently read that when Chevy changed from throttle body to port injection
>     with the rest of the engine the same, it gained about 17% in economy and 
>     about 2/3 that in performance.  How much improvement could be expected
>     by going to timed-sequencial?

Full sequential (which I haven't bothered to implement as yet) offers marginal
improvements in performance, a little bit more in economy, lots for idle speed
stability and lots and lots for emissions.  The improvements would be very
application specific.  Full sequential systems have the potential to have
very advanced injection diagnostics and have the facility to individually
trim the outputs for each cylinder.

>     What manufactures are using timed sequential?  Both Ford and Chevy said they
>     were going toward it but . . . .

Here in Australia, Ford uses twin sequentially fired banks on its six 
cylinder engine (local) and full seqential on the V8 (imported).  I believe 
the sequential system has been around for years.  (EECIV)

I can't remember waht the local GM cars (Holdens) use.

>     Again, are those of you with projects going with timed seq. ?

Yes, eventually.

> 3.  Oxygens sensors:  Several years ago there were wide A/F range sensors 
>     available for about $750 each.  Clearly,  the slick solution is to use 
>     something like that.  Has the price come down enough so they are being used?
>     A bolt on aftermarket that could build it's own table would make things 
>     so much easier.

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