[Diy_efi] Speed Density fueling and throttle position

[William Shurvinton]

A map 'could' react fast enough and in some cases does react where a TPSdot
algorithm might not. A great example of this was posted a couple of months
back by JC on the EFi-332 list.

But it does depend upon the whole system. If you have anything above a mild
cam the map signal shows a tendancy to bounce around as map sampling is not
'generally' time synched to the RPM signal, with the effect being prominent
at low RPM. To get around this you low pass filter the map, often with a
mechanical  RC filter. This filter will also filter out Mapdot transients to
a degree. Whether this is then extended to a sluggish response from the car
is another matter. Your car may weight 2600lbs and have a 30lb flywheel.
Mine is around half that and has a 10lb flywheel. A lean transient that the
first car wont even notice would cause a significant bog on the second.

But if you always sampled MAP at the same point relative to TDC I see no
reason (or have missed the reason) why you could not just use MAP. However
from the point of view of ECU design its much easier to add TPS than sort
that lot out.

Caveat: The more I read, study and play with enrichment strategies the more
I realise how tricky it is.

Bill
----- Original Message -----
From: "Grant Beaty" <gbeaty at ufl.edu>
To: <diy_efi at diy-efi.org>
Sent: Friday, December 20, 2002 9:57 PM
Subject: Re: [Diy_efi] Speed Density fueling and throttle position


> I've always wondered that too. I can see why a TPS would be necissary on a
> MAF car, but the MAP should react fast enough, right?
>



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