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RB20DET lean on cold start

MidnightR32
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MidnightR32 Rookie

MidnightR32

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I'm running a Haltech Platinum Pro with the stock map for the RB20DET + tweaks for my build. When I started it this morning, the IAT was at 32F/0C (Outside temp was ~42F) and the AFRs went off the scale for my AEM gauge. I let it run for ~30 seconds then turned it off. I then did a smoke test, by hooking into a vacuum line directly behind the throttle body, and confirmed there was no leaks ( i let the smoke tester run for ~5 minutes / confirmed it was generating smoke before hand ). I then started the car again, after fixing a power steering leak.... and it seemed to be happy for ~30 seconds (was at ~11/12), but then seemingly shot back up to ~18 again. I then let the car run for a few minutes, thinking this was just cold start related, but the AFRs never came back down. I didn't let the car fully warm up, so maybe this makes sense, but I'm not sure what to do?

The AFRs, when I last ran it, were normal, but because of personal reasons I haven't been able to break in the car. It was rebuilt last year. 

 Engine / Mod list:

    Supertec pistons

    Spool rods

    Kelford 270 cams and Springs

    Stock crank

    Deatschwerks 900cc injectors

    Walbro 255 (Wired directly to the battery relocated in the trunk)

    NKG Audi R8 Coil packs + Conversion Harnesses from Wiring Specialties

    Holset HY35 turbo

    Haltech Platinum Pro ECU

    Haltech boost controller (wired in for high boost

    RB25 Neo transmission + needed bits for the speedo to work

 

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https://www.sau.com.au/forums/topic/485960-rb20det-lean-on-cold-start/
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MidnightR32 Rookie

MidnightR32

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Oh, my misunderstand.

When the car was running, it sounded ok, but if I gave it any gas it wanted to die but caught itself afterwards. It's very different from how it was a couple months ago when it was warmer outside. The logs show that the AFRs are better during, what I assume, is warmup enrichment. Because it's cold, and air is more dense, should I work on the enrichment bit?

GTSBoy Grand Master

GTSBoy

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1 hour ago, MidnightR32 said:

Because it's cold, and air is more dense, should I work on the enrichment bit?

You shouldn't need to massively fatten up the mixtures for cold conditions. For one thing - 0°C is not that cold. For another, the Haltech will be using the IAT sensor to tell it how dense the air air, and calculate the correct amount of fuelling. Then the cold start enrichment is added as a % on top of that, so it should scale with the main fuelling.

You might also doubt the IAT sensor at this time. You're not using one from an RB26 are you? Using a nice Bosch sensor or similar?

2 hours ago, MidnightR32 said:

Unless my sensor just died, was only a couple months old,

Happens. Some wideband units take great pleasure in killing their sensors.

2 hours ago, MidnightR32 said:

How can I test it?

Put another wideband in the tailpipe and compare. Or just swap the sensor to a brand new one and see.

MidnightR32 Rookie

MidnightR32

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Update on the car... I took video of about 9 minutes of it running, shortly after start up, and the car sounds OK? I replaced the ATS and confirmed that the new/old one are showing warming than freezing teamptures. I will replace the wideband tomorrow, but maybe this video can give some insight.

Logs of warmup - https://drive.google.com/file/d/1bpvfmsLfZEjg_rBZw8IseAuM3iWq3BGN/view?usp=sharing

joshuaho96 Veteran

joshuaho96

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23 minutes ago, MidnightR32 said:

It was the wideband. 🤦‍♂️

Yeah not a mystery here. Those AEM wideband controllers kill sensors incredibly quickly. They go full heat the moment they get power. If you don't put them on a switch to only turn on a few seconds after engine start the condensation cracks the sensor and you get results like what you described.

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  • 2 weeks later...
MidnightR32 Rookie

MidnightR32

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On 12/8/2024 at 11:25 PM, joshuaho96 said:

Yeah not a mystery here. Those AEM wideband controllers kill sensors incredibly quickly. They go full heat the moment they get power. If you don't put them on a switch to only turn on a few seconds after engine start the condensation cracks the sensor and you get results like what you described.

how would I do that?

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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Posted

Just get a Haltech CAN wideband, no need to wire any delay circuits, or relay, etc.

Since I've moved to a Haltech CANbus wideband, I have not replaced a single sensor for over 5 years (if not longer, can't remember when moved to Haltach).

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