Re: programmable engine management

["Dan Bubb" <jdbubb@ix.netcom.com>]

Really what is needed it to measure mass air flow. This will compensate for
all variables and is the system of choice for all new cars. But, MAF systems
still have some inlet restrictions, (less than a CIS @ ~1psi loss, as an
example, but there is still a pressure drop @~.5psi loss) so performance
fuel injection needs to dispense with the MAF sensor.
A MAP based system infers mass air flow by assuming that flow is
proportional to manifold pressure, or at least that flow is consistent for a
given manifold pressure and engine RPM. The system applies a temperature
correction to this. A MAP based system doesn't compensate for humidity. So,
a MAP based system doesn't measure mass air flow, it effectively calculates
it.
A TPS based system assumes that pressure drop across the throttle valve is
consistent for a given throttle angle and engine RPM. It can then, in
effect,  subtract the pressure drop from ambient to infer intake manifold
pressure. Because it has a MAP sensor measuring barometric pressure it has
altitude compensation and it can also use temp correction just like a MAP
based system. TPS system also do not compensate for humidity. A TPS system
also doesn't measure mass air flow, it calculates it with one additional
input.
Haltech (as an example) can be either TPS or MAP based. If TPS based it uses
the MAP sensor to measure barometric pressure, so it does have altitude
compensation and, of course, it still has the intake air temp sensor so it
compensates for temp.
Interestingly, all racing fuel injection systems were essentially TPS based
(with no ambient pressure correction) until 1972 when Porsche was
turbocharging the CanAm 917. A TPS system, of course, does not have the same
flow into the cylinder for a given throttle plate angle as the turbocharger
spools up. Porsche/Bosch had to add manifold pressure into the fuel
injection control (via a 3D cam) to what was essentially a TPS system to
approximate the correct A/F ratio.
Getting back to the Badger TB's, the issue here is that the volume in the
intake manifold between the throttle valve and the intake valves is very
small and it only has one cylinder sucking from it. So, the pressure
fluctuation is dramatic compared to a plenum type manifold. The question is
can this fluctuating pressure signal be "conditioned" by combining a feed
from all 4 cylinders and perhaps restricting that feed. Personally, I'd be
asking Badger if their TB's will work with a MAP based system since their
website makes no mention of MAP sensor input for their kits. (The DTA ECU
offered with the Badger kit can do either MAP or TPS based FI, but Badger
only mentions the TPS input.)
TEC II used to offer "Super Blend" software that used TPS input for low load
conditions where the MAP signal wasn't stable enough then transitioned to
MAP based at higher load. Don't know if they still offer this as they have
now gone to WinTEC software which may or may not do this. TEC II was the
only affordable system that could combine TPS and MAP. It would be nice if
it still did.
My $.02
Dan


----- Original Message -----
From: Neal Tovsen <sixteen.volt@verizon.net>
To: Lauri Pettai <lauri.pettai@netexpress.ee>; Scott F. Williams
<sfwilliams@home.com>; Cheapass Ron <rapieper@yahoo.com>; Scirocco-L
<scirocco-l@scirocco.org>
Sent: Sunday, September 16, 2001 2:46 PM
Subject: RE: programmable engine management


> So it **only** runs off of the throttle position? I'm not an EFI expert,
but
> that doesn't sound much different than a carburator!
>
> How does it know if it is running rich or lean? How does it accomodate
> altitude, temp, or humidity changes? Only through the O2 sensor? That's
> *after* the combustion. Shouldn't it be able to predict and adapt the fuel
> settings, rather than wait for an 02 sensor reading?
>
> Neal
>
> > -----Original Message-----
> > From: owner-scirocco-l@scirocco.org
> > [mailto:owner-scirocco-l@scirocco.org]On Behalf Of Lauri Pettai
> > Sent: Sunday, September 16, 2001 2:03 PM
> > To: Neal Tovsen; Scott F. Williams; Cheapass Ron; Scirocco-L
> > Subject: Re: programmable engine management
> >
> >
> > > > > So where does the airflow meter
> > > > > go????   Where am I stupid here?  What is my wrong assumption???
> > > >
> > > > Yo, Cheapass! Your amusing incorrect assumption is that the
> > state of the
> > > > fuel injection art is still stuck in an eighties timewarp! :^) We
> > > > don't need
> > > > no steenking airflow meters anymore! Consider that the load on the
> > engine
> > > > must be measured somehow. There are two ways of doing this: either
> > measure
> > > > the amount of the air flowing in (our scenario), or measure
> > the manifold
> > > > pressure plus other related functions.
> > >
> > > I don't think Ron's stuck in the 80's, though he /is/ an old chap! I
was
> > > wondering the same thing too. And I'm not looking for a floating
> > mechanical
> > > plate, either!
> > >
> > > I think we were both just wondering if there was a place to
> > mount a MAP or
> > > MAF sensor. On any car I've known, the MAP or MAF is mounted to
> > the intake
> > > before the individual cylinder runners split, but on a separate
> > TB system,
> > > there is no such place. I suppose it could be only mounted on
> > one TB with
> > > calculations to account for four cylinders, but at a glance, it
doesn't
> > even
> > > look like there's room for any such sensor below the air horns.
> > Where does
> > > it go?
> >
> > Hmm... Scott is probably stuck in nineties. :) We do not even need a MAP
> > sensor
> > for TB conversion. The engine load is only measured by TB sensor.
> > TB sensor
> > is
> > usually used for acceleration enrichment, but when doing a TB
> > conversion it
> > has
> > to be used for both. As you said that there's no place to connect a MAP
> > sensor
> > and even if you run a separate vacuum wire from each runner then you get
a
> > MAP
> > pressure that is so jumpy that you can't map nothing with it so TB
sensing
> > is the
> > only way to do it right. At least my system is set up like that and it
> > works.
> >
> > Lauri!
> > '84 2.0 16v Scirocco GTX Kamei X1 Bodykit (VIN025736)
> > http://www.eabc.edu.ee/~laurts/scirocco
> > I finally added something new to my site!
> >
> >
> >
> > --
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> >
>
>
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