924Board.org

[bureau13]

I acquired a used Zeitronix wideband sensor and gauge, and installed it on my 931 in place of the narrowband sensor. I did not hook up the narrowband emulation, at least not yet. It is actually running much better this way, so I'm not inclined to mess with that, tbh.

I'm not sure what to expect to see on the gauge, however. At cruise or idle I see mid-11s, at WOT and, well, pretty much everywhere, I seem to be in the 11s. Once at cruise I was at 12 pretty consistently. Even on decel it didn't change that much. I guess I just expected more of a difference between different modes of operation.

FYI it's a Bosch LSU 4.9 sensor, no calibration required (or possible, from what I can tell).
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1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[morghen]

Maybe you messed up the calibration?
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https://www.the924.com

[bureau13]

[Fasteddie313]

It would probably seem to run real good in the 11s everywhere..

It should be more like high 14s in cruise and 11s in boost, but you say boost isn't further dropping the AFRs?

Sounds like the boost sensing part of your WUR isn't working..
You aren't still running those old original cloth covered small vacuum lines to the things such as the WUR and distributor are you?

If you have replaced those vac lines, and are sure they are good, then maybe you need to test the WUR to see if control pressure is dropping when applying pressure to it's line..


You could also turn your fuel mixture screw on the AFM to get your idle and cruise into the 14s, and then see what that does to your boost..
Boost over like 13 is starting to get unsafe though so watch it..

Crack that AFR screw 1/4 turn lefty loosie at idle and see if it raises your idle AFR.. Idle AFR should be about 14.7..

Boost between 10.8 and about 12 seems to work good for me.. Under about 10.8 I can tell it's down on power from that much fuel.. Leaner makes more power but I don't know how lean is ok so I like to see it under 12..

But I don't have it really dumping on the fuel until like 7 psi of boost.. From 0 psi to about 7 psi I have it tapering from high 14's down to low 13's/high 12s and then after 7 psi I'm trying to get it down to right under 12.. But I think yours should fully drop by time your stock WG spring pressure is reached, full stock boost..
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80 Turbo - Slightly Modified

[Carrera RSR]

Zietronix ZT-2 that I have does not need to calibrate the 02 sensor.

Don't worry about the other fuel discussions in this thread, other than that on boost, the WUR should be enriching the fuel from 0.5bar boost. There are a few ARF tables pulled from my Zeitronix showing AFR changes on boost/WOT

Link http://www.924board.org/viewtopic.php?t=42373&postdays=0&postorder=asc&start=45

Ideally you should be in the 14's on cruise and idle. No need to aim for 14.7 on a non IC'd turbo. The fuel is needed to help cool combustion.

WOT/full boost should be in the low to mid 10's. Again a non IC'd turbo needs the fuel to avoid detonation

For non IC'd turbo on mid throttle boost AFRs' of 11's would be OK. 12's starting to go into lean area. Above 13's would not be ideal unless very low boost/cruise
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

[Cedric]

Steve, i don't think the us cars goes that rich on the low boost that they run an full load. Mid 11s should be fine. My car has always been in the 14s at cruise, something seems a bit of. Probably a measuring of the fuel pressure would be good here.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Fasteddie313]

US cars have lambda so they idle at 14.7 if the lambda is operating..
If you set them correctly with a dwell meter to 50% duty on the FV your idle is set to a natural 14.7 and the rest of the fuel curve is correct from there given a properly operating system..
Though it is often set to like 45% to put the whole curve safely a bit on the rich side, the act of the FV going to 45% makes it idle at 14.7 but the natural/WOT curve is still bumped rich..
Cruise too to some extent, lambda will fight it to 14.7..

With the original O2 unplugged the lambda should operate in failsafe mode, and it needs to keep operating in failsafe mode for the overall fuel curve to be correct, or it will go very lean with no reduction of lower chamber pressure and you lose a lot of flow capability..

So, set the idle to 14.5-14.7 with the lambda operating in failsafe (because unplugged O2), and the rest of the fuel curve should be right from there..

If it does not richen in boost it is probably the WUR not doing it's boost richening job, or you are running out of fuelpump due to a poor pump or clogged filters..


I recommend a full CIS pressure test and pump flow test but what really needs tested for is control pressure drop when pressure is applied to the WUR line and maintaining full system pressure at full injector flow..
If you can maintain full system pressure during full injector flow into bottles then your flow is good enough..
Or you can do the fuel flow test like the book says if you are willing to do a FULL CIS pressure checkup by the book, which would be best..


Maybe you should be running in the 10's on boost in a stock car and not 11s, I don't really know, but I do know that 10.5 and down is losing a lot of power and by 10.0-9.8 it's basically misfiring for me..

High 11s to about 12.2 is the fastest but might be too lean for having no intercooler.. Might even be too lean for having an IC but it friggin rips like that..
And crossing into the first couple psi of boost in the low 14s to high 13s makes it spool better than dumping to the 11s immediately when crossing into boost..


Want your car right?
Full CIS tests by the book..


I have a foot and a half of snow.. My car is put away for the year.. Excited to swap the legals over to the Subaru.. I miss the Subaru, it's been awhile..
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80 Turbo - Slightly Modified

[bureau13]

Wow, lots of good info in here, thanks guys. I need a bit to digest it. I don't have the equipment to do a full CIS test I think, but it's probably something I should get and learn how to do.

Btw, I know SOME of my vacuum lines are old and brittle, and some are not. I just broke one for the emissions the other day. That's the first thing I'll check out...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Fasteddie313]

[bureau13]

You mention a "Hoffman Tester." I think I've heard of that before...that's just a specific brand of tester for the CIS system, right? Is it basically the same thing at the link below? I've thought about buying something like that before but was never sure if the various kits I saw were actually what I needed. Also, until I got this AFR, fuel is the one area that seemed to be working OK. I'm now thinking it's pretty silly to assume that, especially on a car from the early '80s!

[Fasteddie313]

[bureau13]

Perfect...thank you!

[Carrera RSR]

[Fasteddie313]

Are the euro speedos not green?
I somehow have a green 160 speedo..
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80 Turbo - Slightly Modified

[Carrera RSR]