I may have lost it here

[huw scourfield]

Hi Bill, the tps signal is linear over degrees of throttle angle, airflow
through the throttle body is not. I would guess that the map signal is
linear over manifold depression, whether this is a linear indication of load
I really don't know-(I suspect it might be). Anyway, the chances of these
two curves agreeing are very unlikely to say the least! I would think it
should be possible with a pair or three of op-amps but personally I'd invest
some time in flash progammable pics, 16f874 etc.
This would take the tps as an input and allow you to use lookup tables to
convert to a suitable map signal-effectively a mappable system. Ideally it
would need some interpolation but with just one dimension this is pretty
easy. I've done some work with these pics and found them to be perfect and
cheap, even if it takes some time to get "into" them. Where in the UK are
you bye the way? If you decide to go this route let me know, I need an
excuse to restart my engine management system. Also this would have massive
potential for conversion of thousands of "Kevmobiles" in the UK.
    Huw
----- Original Message -----
From: <bill.shurvinton at nokia.com>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, January 09, 2002 1:41 PM
Subject: I may have lost it here


> Hi,
>
> I'm looking at trying to help out some of the vauxhall engined kit car
> guys in UK. From the scrappy these engines come with a motronic 2.5,
> which is promptly binned in favour of 45DCOE. A few years later they
> want EFi and drop big bucks on an aftermarket.
>
> Now the problem with the motronic is that it uses MAF, which isn't best
> for DCOE throttle bodies. I spent last night trying to work out how to
> infer MAF from MAP using a few op-amps, and was then hit with the
> following thought, which may be very stupid.
>
> PROVIDED that you chassis tune the ECU, MAF is a measure of load. You
> then look up fuelling as load vs RPM. Throttle position is also a
> measure of load. So, if it is a voltage output MAF (rather than a
> frequency output) you SHOULD be able to plumb the TPS into the MAF feed
> and off you go.
>
> Or am I being really dense and missing something?
>
> Bill
>
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