DIY_EFI Digest V4 #460
Jensen, Mike
MJensen at etcusa.com
Tue Aug 10 13:35:09 GMT 1999
Has anyone ever built a home dynamometer? If so does anyone have any
plans or could someone explain how they did it? Perhaps there is a site
on the web that I have yet to find. If anyone could point me in the
right direction it would be most appreciated!
Michael H. Jensen
Mechanical Designer
Environmental Tectonics Corp.
125 Jamesway
Southampton Pa. 18966
Phone (215) 355-9100 Ext. 276
Email mjensen at etcusa.com <mailto:mjensen at etcusa.com>
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From: DIY_EFI-Digest-Owner at efi332.eng.ohio-state.edu
[SMTP:DIY_EFI-Digest-Owner at efi332.eng.ohio-state.edu]
Sent: Tuesday, August 10, 1999 5:00 AM
To: DIY_EFI-Digest at efi332.eng.ohio-state.edu
Subject: DIY_EFI Digest V4 #460
DIY_EFI Digest Tuesday, August 10 1999 Volume 04 :
Number 460
In this issue:
Re: DIY_EFI Digest V4 #457
Re: DIY_EFI Digest V4 #457
Re: DIY_EFI Digest V4 #459
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----------------------------------------------------------------------
Date: Mon, 9 Aug 1999 19:07:29 +0000
From: xxalexx at popd.ix.netcom.com
Subject: Re: DIY_EFI Digest V4 #457
I have 16 pin connectors, and looking for new sources.
Alex
http://www.obd-2.com
and a welcome back to CSH-HQ
> Subject: ALDL Connectors
>
> Been posted in the DIY archives. Both 12+16. Try OBD for the
16 in search
> Bruce
>
>
> Date: Sat, 7 Aug 1999 19:58:45 EDT
> >From: Mikepoore at aol.com
> >Subject: Looking for ALDL connectors
> >
> >Does anyone know where I can find 12 pin and 16 pin GM ALDL
connectors? I am
> >looking for the male ends. I've got my interface working, but
I would like to
> >connect and disconnect it a little easier than pin by pin.
> >
> >Mike Poore
> >
------------------------------
Date: Mon, 9 Aug 1999 19:08:17 +0000
From: xxalexx at popd.ix.netcom.com
Subject: Re: DIY_EFI Digest V4 #457
I have 16 pin connectors, and looking for new sources.
Alex
http://www.obd-2.com
and a welcome back to CSH-HQ
> Subject: ALDL Connectors
>
> Been posted in the DIY archives. Both 12+16. Try OBD for the
16 in search
> Bruce
>
>
> Date: Sat, 7 Aug 1999 19:58:45 EDT
> >From: Mikepoore at aol.com
> >Subject: Looking for ALDL connectors
> >
> >Does anyone know where I can find 12 pin and 16 pin GM ALDL
connectors? I am
> >looking for the male ends. I've got my interface working, but
I would like to
> >connect and disconnect it a little easier than pin by pin.
> >
> >Mike Poore
> >
------------------------------
Date: Mon, 9 Aug 1999 22:03:31 -0700
From: "John Dammeyer" <johnd at autoartisans.com>
Subject: Re: DIY_EFI Digest V4 #459
Phil wrote
>
>Hi All,
>
John wrote
>> Why would Honda put the MAP sensor just behind the throttle
>plate?
>
>Good question. I guess from the tone of what you wrote that you
>suspected that this could be an issue.
>
Well, I thought it a bit odd. After all, the Fuel Pressure
regulator
is attached to the middle of the plenum.
>I agree with you it probably is. They could of course have a
>table of correction factors for air temp vs non linearity vs
>volume.
True, and perhaps at the high end it really doesn't matter.
>Next issue is why are they using an ambient sensor ? Doesn't
the
>engine
>know what air pressure it is subject to ?
Guess you've never owned a SAAB 99 with mechanical fuel
injection. ;-)
Whenever we took it on holidays from home at 2200' ASL down to
Sea Level
we always found the engine ran poorly. Got it back up to home
altitude
and that wasn't a problem. The 900 series etc. use MAF so they
don't
care; they already know how much air is being sucked into the
engine.
Other vehicles with MAP use some sort of ambient air pressure
sensor. I
even disected an after market fuel injecton box and sure enough,
they
had two Motorola Pressure transducers inside: one for ambient
and one
for MAP.
The 'Grippo' formula uses MAP/(MAP at WOT) to scale the PW.
Additionally there is a second part of the formula that uses MAP
at Wide
Open Throttle (I had assumed Ambient Air Pressure due to the
location of
the HONDA MAP sensor) minus Fuel Vapour pressure divided y the
temperature. This number gets smaller as either ambient
pressure goes
down or temperature go up thereby reducing the PulseWidth; less
air,
less fuel required. Kind of like reaching 8000' ASL and
adjusting the
Lycoming's mixture on on your Cessna till EGO readings are
correct
again.
Does anyone know what the Fuel Vapour pressure for Gasoline is
or where
to look it up on the WEB? I'm assuming (perhaps wrongly) that
it's the
pressure generated by the fuel as it evaporates. The number
used in
Grippo's document suggests 3.1Kpa but that's at 85F. What would
it be
at -40F.
Interesting too, if the MAP is taken somewhere further inside
the
plenum then the WOT value will probably be lower than Ambient
Air
Pressure. If you used one sensor, then you could save Ambient
Air
pressure the moment the ECU powered up just before cranking.
Of
course if the vehicle runs for an hour straight up a mountain
then the
fuel ration will just get richer and richer. So the trick is to
reduce
the PW as the air density decreases.
Al Grippo's equation reads:
Air Density = (0.0391568(Barometric Pressure - 31))
-------------------------------------------------
(Manifold Temp/10) + 459.7
Barometric Pressure, Manifold Temp and the 31 (3.1 Kpa) are all
scaled
by 10. Bruce Bowling does the same thing but in "Hg. In either
case,
this provides the number required to shorten the PW as altitude
or
plenum temperature increase.
Next we get to drag our test frame with GCF (remember... Giant
Computer
Fan) up a small hill from Sea Level to 2500'. Hopefully I
should see
the O2 sensor keep the same values but I'd like to test at
10,000
without leaving the ground.
>
>> For a race car calculating a new injector value PW every
stroke
>may be a
>> requirement but is that really needed for marine or aircraft
>> applications?
>
>Yes. and on second thoughts Yes.
>
>If the calculations are done per cycle then the sudden throttle
>and/or
>load change will encounter maximum of 2 bad combustions.
>
>Now that probably sounds excessively picky but if your engine
>goes from
>250 hp to 125 hp in 1 revolution and then back again the stress
>cycles on the crank are enormous. Even bailing wire has a
cyclic
>strain limit.
Good point. We'll call that the BWCSL. ;-)
I understand what your saying though. I'll check through my
code and
see how many lean combustions I might have. Obviously MAP will
lag TPS
so a change in TPS is probably a better indication that it's
time to
enrich the mixture.
>
>Question ? Who blows up all those F1 engines.
I'd like to try!!!!
>
>Try creating a 4 byte map.
>
>MAX. Vacuum 1000 rpm Max Load 1000 rpm
>Max vacuum 6000 rpm Max Load 6000 rpm
>
>if you interpolate b/w these 4 points and each on it's own is
>correct
>then you will be on average spot on. (This doesn't include
>camshaft timing alterations) this would require the 6 point
map.
>
>By 65,000 points I didn't mean memory locations I meant
possible
>calculated values from rpm 8 bit X vacuum load 8 bit.
>
>thus 255 x 255 = possible outcomes.
OK. I see what you mean.
>
>You will at some stage have to get those 4 measurements as they
>are the basis for all further corrections.
>
>Full load 6000 rpm is easy just pull the stick all the way and
>the prop will do the rest.
>
>Full load 1000 rpm has more air per cycle than 6000 rpm so
give
>it 10% more
We can bog the engine down with the dyno to get that.
>
>Light load 1000 needs the rubber band to be removed.
Hmmmmm.. I think you forgot the page number of the Bosch Blue
Book for
RB (rubber band) analysis. ;-)
>There ! that's 4 bytes of eeprom all used up.
You make it appear really simple. I guess in many ways it is,
after all
a simple SU carburator can do it.
>
>You have only to get rpm from the timer ticks vs a single A/D
>Vacuum Load and you are ready to go. Your last air, water and
>accel corrections are waiting from the last stored calc. apply
>these and squirt.
>
>Given a 1 mHz internal clock and 6000 rpm you have 10 ms or
>10,000 clock cycles to get this done. say 2000 instructions
>executed
>at worst.
Yes, but I want to be able to play space invaders too. 8-).
>
>
> P.S. if this to and fro is boring the pants of others please
>chime in and tell me firmly.
Shussh everyone. This beats the pants off the standard
questions of "I
have a xxx ECU for my sports car and I want to modify the tables
...
what do I do?"
regards,
John
------------------------------
End of DIY_EFI Digest V4 #460
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