DFI, Batch Fire, and other myths

Greg Hermann bearbvd at sni.net
Mon Jan 25 14:42:29 GMT 1999



>
>One thing that might work would be to have a 2 or 4 injector TBI setup,
>with those injectors sized to get you up to maybe 25% of max power,
>and relatively huge TPI injectors in each port. This way you can have
>really big TPI injectors without worrying about idle quality. And, as
>an added bonus, you probably will get a higher % of the fuel from the
>TBI injectors to evaporate, which is probably a *good* thing for BSFC
>at cruise. (Actually I don't know how the pumping work vs. compression
>work numbers pan out... Greg?)
>
Before I got into the idea of air boosted, staged TPI injectors, I wuz
considering staging a Barry Grant VFI unit (primary) with big TPI secondary
injectors!! :-)
>

>
>Someone asked a bit ago about low-pressure sensors. I'm gonna come
>off sounding like a damn Motorola ad here, but I really like their
>pressure sensors. They have a couple designed specifically as MAP
>sensors, and some others in lower and higher pressure ranges. The
>ones I use are mostly temperature-compensated, and have a
>conditioned 0-5v output. The bandwidth is reasonably high, though
>you can get better accuracy if you filter it down some. (They don't
>spec it as -3dB bandwidth, they spec it as 1msec response time from
>10%-90% given a full-scale pressure pulse. I'm too tired to do the
>math but think 500Hz or more.) Accuracy is conservatively spec'ed
>at ~1%-1.5%, you can do better if you're willing to limit the
>temperature extremes, filter down to lower bandwith, and do some
>math on the output signal. (Also the lower pressure range units
>have more error.) Not instrument-grade but damn good. More
>importantly short term drift is low. Best of all they're cheap,
>the last set of 2.5 bar absolute units I got were ~$16 each in
>onesies. Anyways sorry for sounding like a damn ad, I don't get
>a kickback, honest! I just like the damn things.
>
>http://mot-sps.com/senseon/pressure.html

These sound awfully good for less than 10% of the cost of Ashcroft, Dwyer,
etc. instrument grade pressure transducers!!

Regards, Greg
>
>
>   Whew, ok, hope this interests someone.
>   Chris C.





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