Pompiuses

I'm soon going to tune my vafc myself on a dyno with a wideband o2. Tuning WOT is a pretty straight foreward thing, but I'm a bit uncertain about the partial throttle setting. How presicely do I do that? Do I just do pulls with say 30% throttle (or something) and tune the vafc accordingly? How do I know how much throttle to apply?

Asahi

Depending on the dyno you can't really do it on the dyno. That said I have not seen any benefit to tuning partial throttle with a VAFC. It just doesn't seem to help noticably.

Pompiuses

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Asahi &raquo;</TD></TR><TR><TD CLASS="quote">Depending on the dyno you can't really do it on the dyno. That said I have not seen any benefit to tuning partial throttle with a VAFC. It just doesn't seem to help noticably.</TD></TR></TABLE>

So your saying that it's not possible to tune partial throttle on the dyno? Please elaborate.

When lowering vtec engagement to say 5000rpm one might think it would be wise to tune partial throttle from 5000-5800rpm so the car won't run lean when cruising at high speed on the freeway.

ITR981002

Very hard to tune partial throttle on a dyno unless its a Dynapack. You can hold the car at whatever RPM you like under load.

I've read that Vtec engages at 5700 WOT and 5900 otherwise in a type R. Does a VAFC alter both of these values at once or just the WOT one?

Asahi

You car is still in open loop if you are not at WOT so the ECU will compensate for the VAFC and you won't run lean from 5000-5800. AT WOT you are not needing to alter partial throttle so it can be done easily on a dyno. Make sure the graph their Air/Fuel readings for you.

Mustnag Dynos as well as mentioned Dynap[acks can maintain loads aso you can tune partial throttle. Dynojets cannot.

Padawan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Asahi &raquo;</TD></TR><TR><TD CLASS="quote">You car is still in open loop if you are not at WOT so the ECU will compensate for the VAFC and you won't run lean from 5000-5800.</TD></TR></TABLE>

That's actually closed-loop.

Pompiuses

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Asahi &raquo;</TD></TR><TR><TD CLASS="quote">Make sure the graph their Air/Fuel readings for you. </TD></TR></TABLE>

Yepp... I plan AF ratio as close as possible to 13.1:1 from idle to redline at WOT.

btw ; Does anyone know precisely what the "V/T Unmt" - function do on the vafc?


Modified by Pompiuses at 8:52 AM 10/17/2003

Nerv2g

What can't you just mimic the setting for WOT for Partial throttle? Wouldn't they be the same? I always wondered that.

Black R

Just like Trey said, partial throttle tuning on the dyno is useless unless you've got hondata and are checking the fuel trim.

My suggestion is to ride around town and lean it out a bit from 1k-5k. If you have a wideband, this is ideal. Basically you want it as lean as possible without detonating. Anywhere around 15:1 and as high as 17:1 is fine since it's not really under load. Once you are under load, you go closer to WOT and that's a different map reference. Try -10 to -20 and watch your gas mileage improve.

UNMT = unmatch. It's how much fuel the vafc adds at the crossover from HI to LO and vice versa.

Pompiuses

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Black R &raquo;</TD></TR><TR><TD CLASS="quote">Just like Trey said, partial throttle tuning on the dyno is useless unless you've got hondata and are checking the fuel trim.

My suggestion is to ride around town and lean it out a bit from 1k-5k. If you have a wideband, this is ideal. Basically you want it as lean as possible without detonating. Anywhere around 15:1 and as high as 17:1 is fine since it's not really under load. Once you are under load, you go closer to WOT and that's a different map reference. Try -10 to -20 and watch your gas mileage improve.

UNMT = unmatch. It's how much fuel the vafc adds at the crossover from HI to LO and vice versa.
</TD></TR></TABLE>

hehe I don't think I'll butt tune partial throttle without a wideband (which i don't have). Don't want to risk detonation to save a few drops of fuel. I think I'll stay away from tuning partial throttle altogether. Just do the WOT maps.

Thanks guys. Good stuff

euclid

what is the best way to connect a wideband 02 for a street tune, is the only option welding another bung into the header?

Asahi

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

Yepp... I plan AF ratio as close as possible to 13.1:1 from idle to redline at WOT.

</TD></TR></TABLE>

Why 13.1:1? I have found and I bet Black R will agree that, 13.7-13.8:1 will make more power safely at WOT.

Pompiuses

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Asahi &raquo;</TD></TR><TR><TD CLASS="quote">Why 13.1:1? I have found and I bet Black R will agree that, 13.7-13.8:1 will make more power safely at WOT.</TD></TR></TABLE>

Well after searching through posts seeing what others have done I've come to the conclusion that 13.1:1 is safe for regular street driving all year. Winters can be cold here in Norway, and sometimes temperatures can be as low as -20 degrees celcius. Won't the car run very lean under those conditions considering that AF is adjusted indoors?

Pompiuses

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Pompiuses &raquo;</TD></TR><TR><TD CLASS="quote">Won't the car run very lean under those conditions considering that AF is adjusted indoors?</TD></TR></TABLE>

Anyone have thoughts about this?

mafay2

I saw a Prelude tuned to A/F of around 13.5:1 in WOT during day time when it was 25 degree C. At the same night, the temperature dropped down to near 0 degree C, the car was running way too lean, so he added like 5 point of fuel on his VAFC.

IN VTEC

iTrader: (3)

Dynojet 248's have a loading option that allows you to load vs. rpm, speed, or braking effort presets.