Aftermarket EFI, speed density etc.

[Jonathan R. Lusky]

Peter Wales writes:
> 
> The user *will* require a constant air fuel ratio! Stoichiometric to be
> exact.

You only want stoichiometric A/F under conditions you see on the FTP.
Non emissions applications should never be running at stoich (a point
which I've argued with several F-SAE judges :(  ).

> The EPA defined a test schedule which each manufacturer has to go through
> and the total emissions allowed during this test are defined. The test is
> usually very low throttle and accelerations, I suppose typical of a cruise
> through rush hour traffic.

The FTP-75 is broken up into 3 parts (not sure the proper name for each
part, we called 'em Bag 1, Bag 2, & Bag 3).  Two hot starts and one cold
start.  Both city/traffic and highway driving.  Supposedly the test was
developed by following some EPA employee on his trip from home to work
and back to home.

> Thus the manufacturer has the option of staying
> stoichiometric just in this schedule, or as most have done, all of the time
> the throttle is less than fully open.

My 91 GMC 2500 with TBI350 kicked into power enrichment mode at 40%
throttle or 3400rpm.  Power enrichment mode goes open loop, turns
off the EGR solenoid, and grabs desired A/F from a lookup table.

-- 
Jonathan R. Lusky                        lusky at knuth.mtsu.edu
http://www.mtsu.edu/~lusky/                 (615) 726-8700
-------------------------------------   ------------------------------
68 Camaro Convertible - 350 / TH350  \_/ 80 Toyota Celica - 20R / 5spd