How to tune a big cam without O2s??
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From: Port Tobacco, MD
How to tune a big cam without O2s?? I have a wideband and have pulled the O2s to get the tune down. I was under the impression that you tune the VE table but I have read that the ve table is only used when the maf is unplugged. Should I tune with the IFR table.
Phil
Phil
Last edited by Phil99vette; Oct 28, 2004 at 04:41 PM.
No, the VE table is the only thing left to use, when
the MAF is unplugged. It is also used at lower RPM
and in unsteady-MAP conditions, even with the MAF
there. However if you unplug the MAF -and- the O2s
you will be looking at the bare, uncorrected-by-
closed-loop, speed-density tune.
If you didn't change the pump and/or injectors then
I would leave the IFR be. Though you would want to
be sure there is no degradation from stock, e.g. fuel
filter in need of changing. Otherwise you might as
well believe the IFR is right, and not mess it around.
If you have a Secondary VE Table then you should be
tuning that and populating the Primary matching rows
with the same values, interpolating between and
extrapolating the end rows. If you have only a Primary
then that does everything.
If you can get the car to run with the bare SD tune then
scaling by (wideband AFR / commanded AFR) pointwise
on the VE table should have you tuned up after a session
or two.
the MAF is unplugged. It is also used at lower RPM
and in unsteady-MAP conditions, even with the MAF
there. However if you unplug the MAF -and- the O2s
you will be looking at the bare, uncorrected-by-
closed-loop, speed-density tune.
If you didn't change the pump and/or injectors then
I would leave the IFR be. Though you would want to
be sure there is no degradation from stock, e.g. fuel
filter in need of changing. Otherwise you might as
well believe the IFR is right, and not mess it around.
If you have a Secondary VE Table then you should be
tuning that and populating the Primary matching rows
with the same values, interpolating between and
extrapolating the end rows. If you have only a Primary
then that does everything.
If you can get the car to run with the bare SD tune then
scaling by (wideband AFR / commanded AFR) pointwise
on the VE table should have you tuned up after a session
or two.
Last edited by jimmyblue; Oct 28, 2004 at 03:26 PM.
Thread Starter
7 Second Club
iTrader: (11)
Joined: Jul 2002
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From: Port Tobacco, MD
My MAF is still plugged in but the O2s are unhooked. So would you still adjust the VE table if the MAF is plugged in or would you adjust the MAF table.
Phil
Phil
I think I'd take the time and get the VE dead-nuts first.
The MAF and VE interplay too much in the low-mid throttle
to do it cleanly with them both arguing. At best the MAF
onscures things, at worst it may be lying too. If you have
a well behaved VE table then when you hook the MAF
back up you can attribute any tune errors (esp. above
4000RPM) to it with more confidence. Not either or, but
one battle at a time.
The MAF and VE interplay too much in the low-mid throttle
to do it cleanly with them both arguing. At best the MAF
onscures things, at worst it may be lying too. If you have
a well behaved VE table then when you hook the MAF
back up you can attribute any tune errors (esp. above
4000RPM) to it with more confidence. Not either or, but
one battle at a time.
Unplug the MAF. 
Philly my Wide band integration cable is on its way. We can sit down and tune the car in open loop next week sometime. Free of charge i just want he hear you car idle 
Few things for open loop tuning
Set the open loop f/a table to 1.13 (this should command 13:1) set the pe table to 1.0 (no power enrichment since the computer takes the riches value from both tables). Hook WB up and log how far off you are in AFR then adjst the ve table accordingly (by percentage).
This can be acheived a lot faster in HPTuners since the scanner plots AFR ratios for you via the cable. I wont be getting mine back till Monday, Tuesday sometime and you are free to use it and make changes with edit and reflash.
Big cams can run off of the o2 sensors but the ve table NEEDS te be dialed in close to get it to idle and have good driveability.
I can offer you all the information i know to start tuning the car from there. I will also explain some other stuff you may be interested in. Shoot me a pm or AIM me at lhas9978
I also have a peice of silicone hose you may want in case you get rid of the MAF
Few things for open loop tuning
Set the open loop f/a table to 1.13 (this should command 13:1) set the pe table to 1.0 (no power enrichment since the computer takes the riches value from both tables). Hook WB up and log how far off you are in AFR then adjst the ve table accordingly (by percentage).
This can be acheived a lot faster in HPTuners since the scanner plots AFR ratios for you via the cable. I wont be getting mine back till Monday, Tuesday sometime and you are free to use it and make changes with edit and reflash.
Big cams can run off of the o2 sensors but the ve table NEEDS te be dialed in close to get it to idle and have good driveability.
I can offer you all the information i know to start tuning the car from there. I will also explain some other stuff you may be interested in. Shoot me a pm or AIM me at lhas9978
I also have a peice of silicone hose you may want in case you get rid of the MAF
