91L98Z28

This is a pretty simple one, but I don't recall seeing it mentioned before (or in tunercat) so thought I'd mention it.

IAC steps compensation for fan coming on is at 862b (fan1) and 862c (fan2). my L98 always bogs a bit when the fan comes on, so I'm going to try bumping it up a bit.

also nearby is 862f .. start up delay. I wonder if that helps contribute to the idle flare gm has programmed in, that is to say, i wonder if this is the delay that the IAC is left in the start up park position before being reducing the steps count.

will post results after playing with these parameters.

Grumpy

One other thing to watch is the injector vs battery voltage correction. When the fans click on there is a voltage drop.

91L98Z28

Good point grumpy. I never thought to look at that. Now that I have a dataQ DI-194RS i'll have to monitor the batt voltage when the fan comes. this thing has to be the most useful $25 ever spent.

I just got back from my lunchtime testdrive and can confirm that (through one fan power on cycle so far) the location above does seem to work and that the behavior of the engine after fan coming on is much better with a few extra steps thrown in.

Grumpy

Look at what the voltage does, and the injector correction at that voltage. You might just reduce the correction to the same factor as what it is at 14.2 and then see what you have. And/or look at what the corrrection is for the application to match your injectors and see how they compare to what you have.

If you want to get crazy, disconnect the alternator, and just run off the battery, and as the voltage drops, see if the AFR remains constant.

Z69

91L98Z28, I not an electronics wiz, but the 194rs is only rated for 10vdc IIRC. So bat volts may be out. I'd think Craigs software would catch it. I need to get a 194rs also. One of those and a DIYWB & the Doctors rpm converter is all that would be needed for most cars.

91L98Z28

Man, I'm just not thinking these days!

I forget the max V it can read, but 10v does sound right.

the reason for using 194rs is beause i suspect the transient may be quite fast, faster than the aldl data stream can catch.

it should be relatively easy to use a few resistors to divide the voltage down into the 194rs's range. A simple case scenario which should work fine, would be two 470ohm resistors in series across the battery terminal, and then pick up the voltage reading with the 194RS beteween the two resistors. The two resistors (940 ohm total) would draw about 14mA total, for a dissipation per resistor of 91mW - well within a 1/4 watt resistor. I don't think the 194rs will load the circuit it's reading (otherwise it woudln't be very useful), so it should work just fine in this way (and will read exactly 1/2 battery voltage). You could probably even use 1k resistors.

Z69

I tried to e-mail you but you have it turned off.

After I posted, I realised you could use resistors.

ok, remember more of the equations now
PIE etc...
How would you use it on a 24vdc variable 4-20ma circuit?

jeepguy553

I can't tell you much about your ECM, but I can tell you that this is good advice. On a basic level of electrical theory, this is great advice IMO. If you add a load to an electrical system, you add amperage requirements. The increased amperage requirement may cause a voltage drop in other parts of the circuits.
It all goes back to Ohm's Law...V=IR (volts=current x resistance). There are all sorts of ways to manipulate this equation. If V is to remain a constant with an increase in current (I), resistance (R) has to drop by a proportional amount...at least that's what they taught us in Nuke School.

91L98Z28

Not sure i follow. are you trying to measure the variations in the 24vdc supply, or the current itself?

Z69

Another nuke on this site. About time I ran into one.

The current will vary from 3.9-21ma. Real good PS. Holds voltage constant up to rated load. I think. Never measured the voltage drop. I may be confused. Been up too long.

jeepguy553

NUKES HAVE HIJACKED THE THIRDGEN.ORG BOARD!!!!

I got plenty of sleep on the ship...Engineering Lab Tech (ELT).