Some units will substitute their own signal based upon actual inputs from
the sensors and others will modify the signal x% from actual.
Inputs/Outputs from APEXi:
MAP (Signal Intercepted and Modified - Input/Output)
TPS (Signal Monitored - Input)
RPM (Signal Monitored from Ignition Coil - Input)
Since there are 16 cells that the APEXi modifies (range can be changed - I
use 800-5200rpm in 400rpm increments), it's not like a Roe or Split-Second
MAP modifier (which only modifies the entire signal x%). It allows for a
huge range in each cell (can go as high as 50% but not recommended as the
factory fuel trim% is +/-30% already...you change them 5% for fine tuning).
Example (my old fuel curve running without nitrous - rpm/fuel% points):
800 = -15% (it was too rich at idle)
1200 = -10%
1600 = +5%
2000 = +5%
2400 = 0%
2800 = -5% (start correcting factory fuel curve)
3200 = -12%
3600 = -10%
4000 = 0%
4400 = +5% (add a little bit on the top end to help prevent detonation)
4800 = +5%
5200 = +5%
I used the APEXi to correct the fuel curve I had - only to fine tune it -
and also used the second program on the box to modify the fuel curve for
nitrous use. I tried using a Roe controller (Split Second has the same
thing) but it only moved a broad range and would allow for specific RPM
point changes. The two fuel program options were the main selling point
since I could change it on the fly with minimal relearn time. The negative
percentages in the middle of the RPM band were to correct the overly rich
condition that Dodge programs into the PCM's and put my A/F right at 12.0:1
under WOT across the board. Yes, the PCM will "learn" a little bit and you
will have to recheck the A/F after about 400-500 miles...but once that was
done - it stayed right where it needed to be. One thing though...once you
modify the actual signals to the PCM, you can't monitor the PCM fuel
adaptives anymore unless you also include the correction factor from the
piggy-back.
You can use the APEXi (SAFC-II or "Neo") to fine tune just about any fuel
system for a minimal cost and also gives the customer a few extras in the
process (if you enjoy having the live monitor functions that the unit
offers).
- Bernd
-----Original Message-----
From: Dan Kramarsky [mailto:dkramarsky68@yahoo.com]
Sent: Tuesday, March 18, 2008 11:40 PM
To: dakota-truck@dakota-truck.net
Subject: Re: DML: RE: Fuel Mix Computer
Bernd,
Can you explain to me how these piggy back computers work? Do they send
signals to
stock PCM to make it think the MAP sensor is reading something its not? etc
etc...
Maybe you can explain it best to me this way:
Input signals To Apexi Output signals From Apexi
======================= ========================
yada yada yada yada
thanks!
-dan k.
This archive was generated by hypermail 2b29 : Tue Apr 01 2008 - 00:20:40 EDT