Sequential VS Batch fire systems

Dirk Wright wright at uspto.gov
Fri Sep 6 16:19:53 GMT 1996


On Fri, 6 Sep 1996, Fred Francis wrote:

> Would anyone like to comment on batch fire vs sequential injection
systems?  > What are the real world advantages to each under specific
circumstances?  GM > went to sequential systems recently on the new
camaros and corvettes, WHY?  Is > anything really gained with a sequential
system in terms of performance, > efficiency or driveablility?
> 

Off the cuff, I'd say that batch fire vs sequential fire might not make
much difference at very high revs, since the fuel injected to the closed
intake ports woudl only sit there for a short time, while at low revs the
sitting time is longer, which would reduce drivability. For a 4 cylinder
engine at 6,000rpm, 180deg of crankshaft rotation takes 5msec.  If the
fuel is injected at the begining of the exhaust stroke (intake closed,
batch injection of 2 at a time, this is the "odd" injector), the fuel sits
there for 5msec before the intake opens. At 1,000rpm the fuel will sit
there 30msec. 

Assuming the evaporation and droplet enlargement follow an exponetial
function of the general form y(t) = y(0)*e^at, and that the amount of fuel
injected at the initial time y(0) is the same for each case (a gross
simplification), and normalizing by letting a = 1, gives a simple
expontial function. The value of e^0.005 = 1.005012520859 and e^0.030 =
1.030454533954. Which I calculate as only a 2.5% increase. Unless y(0) is 
very different for each case, then there isn't much difference between 
the two. Of course, this could be completely wrong..... 


****************************************************************************
Dirk Wright 					            wright at uspto.gov
"I speak for myself and not my employer."               1974 Porsche 914 2.0
"A real hifi glows in the dark and has horns."            1965 Goodman House
****************************************************************************




More information about the Diy_efi mailing list