If anybody has a Vitesse MAF and multimeter, I would like to know what the resistance is across your IAT, and at what ambient temp. I believe it's the first and last pin of 6 pins.
Car is starting up extremely rich, lamda 0.7 or so on cold (~32f) starts, eventually leans out to normal 1-0.95 lamda as the car warms up. I know there's a little bit of fuel enrichment on cold starts, but this is much richer than I recall it being. I did rop the MAF from hood level onto the ground by accident last time I had the pipe off, wondering if I might have broken the IAT.
MAF IAT testing
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Tom
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I'm not sure they are all the same -- I thought he switched MAFs at one point, no? I can test mine though. But are you really trying to start the car at -32F?
~ not -
0c
I think there was a 4pin to 6pin switch long ago, but no idea if he switched MAF calibrations .. I know Autothority use to use ProM MAFs, the Vitesse kit appears to be similar plug and etc shape as what ProM still sells but he unbrands them so I’m just taking a guess. I’m assuming he would keep the same calibration curves with the different MAFs for simplicity of not having to remap the tunes with each batch of MAFs
0c
I think there was a 4pin to 6pin switch long ago, but no idea if he switched MAF calibrations .. I know Autothority use to use ProM MAFs, the Vitesse kit appears to be similar plug and etc shape as what ProM still sells but he unbrands them so I’m just taking a guess. I’m assuming he would keep the same calibration curves with the different MAFs for simplicity of not having to remap the tunes with each batch of MAFs
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Tom
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Ah, my old eyes saw the ~ as a negative sign. Sorry bout that. Still chilly, but well within range of the MAF. Post a picture of yours and I'll let you know if I have the same one. MAFs have that filament, which seems pretty delicate, so dropping it may have done something. Have you checked the voltage on DME7 when it's running so rich? The basic air mass signal might be compromised. And what are you getting for the IAT? Worth testing even without knowing the specs just to make sure it's not open or shorted.... Does the car warm up and run well, stay in closed loop, etc.? My car can drop into the 10's on first start up when cold like that -- not sure that's all that unusual really?
There’s a pic in this thread the PO made a long time ago. https://rennlist.com/forums/924-931-944 ... -pics.html
Once warmed it does go into close loop and leans out normally. I never really paid attention to cold start AFR, but I’m fairly certain it never went quite so rich, I want to say 0.8-0.85 lamda?
O2 sensor is new. The DME temp sensor was replaced in the past by PO. Havent yet had the chance to get into the passenger footwell to check measurements at the DME.
Other possibility I suppose is the WBO2 has some sensor drift.
Once warmed it does go into close loop and leans out normally. I never really paid attention to cold start AFR, but I’m fairly certain it never went quite so rich, I want to say 0.8-0.85 lamda?
O2 sensor is new. The DME temp sensor was replaced in the past by PO. Havent yet had the chance to get into the passenger footwell to check measurements at the DME.
Other possibility I suppose is the WBO2 has some sensor drift.
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Tom
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That's the same MAF I have, so I'll try to get a reading. It's on a shelf right now, so shouldn't be too hard. I'll also start my car up in the morning and let you know what the AFR is. Widebands take a while to warm up and give accurate readings too -- so the readings may be off until it warms up a bit. If the car starts up ok and isn't giving you problems, I'm not sure I'd worry about it myself....
From what I recall while troubleshooting my MAF install, my AFR at cold startup was perfect at 14.7 or so.
I did end up having a bad TPS which caused the car to go rich after warming up, which sounds opposite to what you’re experiencing.
I did end up having a bad TPS which caused the car to go rich after warming up, which sounds opposite to what you’re experiencing.
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Tom
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I'd guess that's just because your wideband wasn't warmed up? Mine will show 14.7 to start, then drop into the 10's as the sensor warms up, then slowly climb back up to 14.7 closed loop as the engine warms up. Cold start fuel enrichment is a universal thing -- starting with the manual choke on early cars (and planes), which evolved into various mechanically-automated chokes on carburetors, and is now built into the fuel maps of modern cars. Here's a nice article explaining why it is needed...944m3 wrote: Wed Feb 19, 2025 12:25 pm From what I recall while troubleshooting my MAF install, my AFR at cold startup was perfect at 14.7 or so.
I did end up having a bad TPS which caused the car to go rich after warming up, which sounds opposite to what you’re experiencing.
https://www.hpacademy.com/technical-art ... -starting/