EGT and O2 sensors time resolution AND LED tach

[crdotson]

>===== Original Message From diy_efi at diy-efi.org =====
>I asked the questions because I am interested in designing a Sequential fuel
>injection system on a 4 cylinder bike engine.  Doesn't look like I'll be put
>on that team though, and this project may be postponed until next year, but
>I'm still interested.  The engine is on our FSAE car which is basically a
>mini race car.  One of the main ECM designers for the car is interested in
>going to sequential injection this year, and I was wondering is a closed
>loop system might be worth the effort to implement.

I too am on a FSAE team, and I am responsible for the ECU/tuning aspect of 
this year's race car.  I have talked at length with the guy who tuned our EFI 
last year, and he contends that there is no need to run closed-loop in a race 
application.

One of the reasons for this is that race cars typically run much richer than 
street vehicles.  In some vehicles, you have to inject more fuel that would 
otherwise be desired in order to cool the intake air to prevent pinging.  In 
order to control to a rich condition you would likely need a wideband O2 
sensor, and of course you would need an adapter box that would allow your ECU 
to read the sensor's output (or an ECU capable of reading it, both of which 
are expensive for an FSAE team).  The incorporation of these devices also adds 
considerable weight, which as you know can knock you out of competition!

You should always run some form of O2 during dyno tuning to tell what A/F 
ratios you are getting.  You definitely do not want it to be lean, as that can 
be disastrous at full engine load.  It can also be helpful for tuning in that 
you can tell how much difference in torque/hp you have compared to changes in 
A/F ratio.  This can help you lean out the mixture (never leaner than stoich, 
of course) as much as possible without degrading your torque, which I believe 
is called tuning for "lean best torque."

Good luck this year, just might see you at competition!

Craig Dotson
2002 VT FormulaSAE

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