RAB

Is the VAFC worth getting if 96+ Prelude that have the OBDII, Becuase as I understand it the OBDII makes a car run clean no matter what mods you put on it. i.e. I/H/E. If I change the air/fuel ratio with the VAFC will those settings always remain in the computer, or does the fukin OBDII over ride the VAFC, and yes I know the VAFC is a piggyback system; so it should override the OBDII right.

also anyone read up or done this DIY from NTPOG
http://www.ntpog.org/mods/fifth-afc/ecu.shtml
basically you cut the back up power for the ECU so it has no memory so each time you turn off your car the ECU is reset; but once you drive the ECU and the OBDII with adjust settings to make your car run clean.

OBDII=

DsITR

this is a theory....it has been argued continuosly, it seems there is some truth behind it because 4th gen (OBDI's) usually seem to be quicker and dyno higher.

I would just run the OBDII workaround from ntpog.org like you are saying..

satan_srv

Just do the workaround and you'll enjoy v-afc settings for the vast mojority of the drives you do.

RAB

so just to make sure: that work around will just allow me to turn "off" and "on" the memory function of the ECU. So each time I start the car fresh settings. Right.

rjr162

what i did was just use a relay off of the ignintion to turn my backup memory on (of course you don't really need a relay, you can just run a link over and fuse it). I did this so the ECU does have the two +12's when the car's going. No real point, but sorta a "just in case".

satan_srv

Dude that's BS. Show me evidence of OBDIs dynoing higher. The 96 was a very well tuned car from the factory, and from my own experience kills many OBDI ludes mod for mod...

Boostless97Lude

i had a V-AFC on my 97, it improved with minor tuning, i never had a dyno available to really tune it in perfect, but i did notice a slight gain in power, plus you can chnage your VTEC to give you a more continuous power curve, instead of the idle lobes dying out and then VTEC engaging, you can make VTEC ingage just as, or even right before the idle lobes die out, giving you consistant power

LordVtec

Running a VAFC on my 98 lude, and i have had no complaints as of now.. i am waiting till i finish my turbo kit before i have it dyno tuned..

DsITR

[QUOTE}Dude that's BS. Show me evidence of OBDIs dynoing higher. The 96 was a very well tuned car from the factory, and from my own experience kills many OBDI ludes mod for mod...[/QUOTE]

Satan I'm not sure I really understand your post?? Are you saying that 96 (which was the first year w/OBDII) dyno's higher than other ludes..or you mean it is the most mod friendly?

On anoter note, you may be right....I have only seen a couple dyno sheets, but from what I remember it seems like 5th gens dyno @bout 156-160 and 4th gens dyno @ 160 an up...I could be wrong though.

LordVtec

Ryan,
I sent you the wiring instructions for the VAFC via email... i figured i would post it here in the hopes to maybe help anyone else that might be thinking of installing the VAFC in their 5th Gen prelude... hope this helps.. let me know if you have any questions.. (i have pics and and EXCEL file that i can email should anyone want it..)

First Connector: is a 32 pin and will be used for connecting the RED, ORANGE, BLACK, BROWN, PURPLE, PINK, and GREEN wires from the VAFC
(then there is an empty space)

Second connector: is a 31 pin and will be used for connecting the BLUE wire from the VAFC.

Third Connector: is a 16 pin and will be used to connect the YELLOW, WHITE, and GRAY from the VAFC.

Red Wire
Orange Wire
Both the RED and the ORANGE wire from the VAFC go connected to the Yellow with Black Stripe Wire on the 32pin connector- this should be
The 1st wire counting from right to left..)

Black Wire
Brown Wire
***make sure to install the brown wire closer to the ECU than the black wire…
so you will have to tap the ground wire twice, just make sure the brown wire is closer to the ECU***

Both the BLACK and the BROWN wire from the VAFC go connected to the Black wire on the ECU - This would be the
2nd wire counting from left to right. (right next to the IG Power wire from above)


Purple Wire
Pink Wire
The PURPLE and PINK wires from the VAFC use the same wire, but the input wire will go into the ecu, while the output wire will go out towards the VTEC solenoid..
Best thing to do is to cut the wire so that you have two pieces of wire then solder or connect the purple wire to the piece going into the ECU,
and the PINK wire to the one going out towards the VTEC Solenoid.) - Cut and use the Green with the Yellow Stripe on the 32pin connector.
(on the 32 pin connector it will be the 4th wire, in the first row from right to left)

Green Wire
The Green wire from the VAFC goes connected to the Yellow with Green Stripe on the 32 pin connector.. (this will be the 4th Wire, Second Row from right to left.)
(This is the last wire you have to connect to the 32 pin connector..)


Blue Wire
The BLUE wire from the VAFC will go Connected to the solid blue wire on the 31pin connector - this will be the 5th wire, second row from right to left.
This will be the only wire you will connect to the 31 pin connector.

White Wire
Yellow Wire
The WHITE and YELLOW wires from the VAFC use the same wire, but the input wire will go into the ecu, while the output wire goes out to the sensor.
Again, the Best thing to do is to cut the wire so that you have two pieces of wire then solder or connect the WHITE wire to the piece going into the ECU,
and the YELLOW wire to the one going out towards the Sensor.) - Cut and use the Red with Green Striped wire on the 16pin connector.
(this will be the 3rd wire, first row from right to left.)

Gray Wire
The GRAY wire from the VAFC goes connected to the Red with Black Striped wire on the 16 pin connector. (this should be the 5th wire, first row from right to left.)

(after you wire it make sure to follow the instructions in the manual to perform the initial set up..) anyhow, hope this post helps...

drift

my 1997 dyno'd 174 bone stock when i got it back in 1996.

i cut the backup power line on my ecu cuz i did notice the timing begin to retard itself after 3-4 drives.

piotrush

WOW, nice #s. Do you mean you cut the backup power on a stock car, or after vafc install? Also, did you get any CELs after cutting the power? Did you use a switch?

RAB

Hey LordVtec:
Great write up, a long time ago when I was doing research about this unit I found instructions. So I just compared them to yours and they match. Also, I have the Helms manual, so I was able to match all of your wire description (i.e. the wire colors of the ECU) and verify the match with the Helms manual, they all matched I can't get a pic of the Helm but I'm gonna scetch something.

LordVtec

Glad i could help... Hope this helps as well:

RAB

As the Helm manual states for color of wires.

<U>Pin 32</U>
Slot 8:
Color of wire: GRN/YEL
Function:Drives VTEC solinoid valve
Slot 10:
Color of wire: BLK
Function: Ground for the ECM control circut.
Slot 11:
Color of Wire: YEL/BLK
Function: Power source for the EMC control circut.
Slot 20:
Color of wire: YEL/GRN
Function: Sends ignition pulse
<U>Pin 31</U>
Slot 15:
Color of wire: BLU/BLK
Function: Detects VTEC pressure switch signal.
<U>Pin 16</U>
Slot 1:
Color of wire: RED/BLK
Function: Detects TP sensor singnal
Slot 3:
Color of wire: RED/GRN
Function: Detects MAP sensor signal.

LordVtec that pic helped a lot. Funny I posted the samething as you did. Great minds must think alike.


EDIT
Just for fun I throw monkey wrench in the machine. LordVtec I found this a long time ago while I was doing research. It conflicts with your diagram, it concerns the ground wire.

The difference is #9 is logic ground and #10 is power ground. I think yours is right just makes sense that you'd ground the power.



[Modified by RY8127, 12:58 PM 11/24/2002]

drift

i did it after i installed the VAFC and noticed power levels dropping after a couple months. i didnt install a switch. i just extended th wires after cutting them so i can reattach them for diagnostics.

LordVtec

(i agree, great minds do think alike...lol) It makes sense to me to use #10 for the ground... the diagram i posted is off of Apexi's website.. (i was just bored at work and highlighted the specific pins... lol)

lildrgn2.0

Todd (JG Luder) did the conversion on my car... CUT THE WIRE ... with out really telling me.. only noticed when I heard a *snip* and looked up and he was just smiling... /sigh

anyway, the car did run stronger after it forgot that my secondary O2 is not there...

piotrush

SO its safe to just cut the damn thing and leave it there? ANy problems that could arise from this?

rjr162

BTW&gt;&gt; i just noticed something the other day flipping thru my prelude shop book for fun.. happened to stop on the section of the ECU, and to reset the computer you only have to pull the radio fuse under the hood for 10 seconds. Here i've been thinking you had to let it sit for a few mins! lol. My CEL light's comming on because of a stupid secondary O2, and i tried this.. 10 seconds works.

cuban

Has anyone ever done a dyno comparo of their car before, after resetting the factory ecu or is all this OBD2 "detuning" ASSumptions?

sharkcohen

Woah, old thread with some bad information. The OBDII 'workaround' is ****, it's worthless. Resetting the ECU is worthless. When you reset the ECU, you cause the car to run alot richer in open loop for about 10 minutes, during which time the ECU recalibrates its Long Term Fuel Trim back to where it was before you reset.

As long as VAFC adjustments are made for only open loop, the ECU will not do anything to change what you have done. Any VAFC adjustments that affect closed loop operation will be adjusted by the ECU with Short Term Fuel Trim, and Long Term Fuel Trim will be modified, screwing with your open loop tune.

Mr Black

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sharkcohen &raquo;</TD></TR><TR><TD CLASS="quote">

As long as VAFC adjustments are made for only open loop, the ECU will not do anything to change what you have done. Any VAFC adjustments that affect closed loop operation will be adjusted by the ECU with Short Term Fuel Trim, and Long Term Fuel Trim will be modified, screwing with your open loop tune.</TD></TR></TABLE>

How do you ensure that your VAFC adjustments ONLY affect open-loop running?

sharkcohen

The stock ECU enters open loop after about 35%-37% throttle. VAFC adjustments above 37% throttle should affect only open loop.

Mr Black

So if you leave the settings alone below 40%, just to be safe, there is no risk of the ECU starting to adapt and screwing up your full-throttle maps?

VAFC allows you to define 'low-throttle' and 'high-throttle' regions to your own liking, right?