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afr adjustment where to start
i have a newly rebuilt 76 3.0l row turbo new stock Mahle P&C sc cams new k27 evergreen raptor turbo long neck IC . nos throttle body 3 way adjustable wur. ( cold hot and boost) rebuilt balanced fuel distributor 2 and 5 running 5% more fuel more than the other cylinders new injectors new twin 044 fuel pumps .. so basically everything is new built for reliability not HP basically stock with a few upgrades .
The fd and wur set up by Brian (rawly8) perfect fuel pressure curve . The car starts a little hard 5 seconds of cranking then idles high about 1100 a little black smoke for the first 5 seconds or so runs super rich when hot and cold. I can watch the single point afr gauge go for 12 to 13.5 to 14 then *** off the scale all within about 2 seconds of running. ( cold start injector is disconnect for now ).. i need to lower the idle and lean out the afr . as mentioned nos throttle body not sure if it is set correctly . what the big knob for? so where do i start i would assume there are steps to follow? Thanks in advance Regards Ned |
"Where to Start?"
Put a set of CIS gauges on and post your numbers , This will be your starting point. |
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Maybe try jumping the fuel pump relays to run with the key on, let it build pressure for 10-20 seconds before start - still the same? Mine used to (usually) fire immediately if daily driven. If I'd left it for a few weeks, it might want longer to wake up. Quote:
I forget whether it's the AAV or the AAR that bleeds extra air into the motor for initial cold running. It's the one that looks like an ally version of the air freshener you plug into a wall socket. A little column thingy... It's powered, and should slowly close the orifice over a few minutes with the motor running. I knocked the power plug off mine once when messing with the WUR and didn't notice; cold start/idle was exactly the same as usual - but some miles down the road, no power to it resulted in hot idle of 1800 RPM, LOL... Quote:
At least, mine always did on CIS. Quote:
Working temp for a narrowband sensor is 600F; any reading before it reaches that is, uh, "not reliable". Or "noise". Or "garbage". A Bosch 4.2 or 4.9 wideband sensor doesn't provide usable readings until it reaches a working temperature of 1200F. Despite a dedicated heater, my Motec doesn't log readings from my 4.9 for a good 3-5 minutes after motor start. Any unheated sensor variant just takes longer to get up to temperature (as it relies on the exhaust gas to do the job). As the gauge reads down to 12:1 - and a narrowband only works between 14:1/15:1 or so - I'm going to presume that this is a wideband. Quote:
Can't help with your other questions. But my advice would be not to even think of touching anything until you've at least got usable readings from the lambda sensor - and preferably not before the motor is fully up to temperature as well (eg oil at working temperature). You say the WUR is in spec - so I wouldn't touch that at all. Unless there was a compelling reason to do so, and not without more research. If you do adjust the idle CO2, as a data sample size of 1, I found mine would idle perfectly with 3% CO2 - but setting it this would lean caused a lean surge in the mid-range at a constant (light) load and throttle setting (like climbing a hill at the speed limit). Which went away entirely when set a little fatter. Really made no difference to the idle though, apart from the CO2 reading (checked on both a Gunson and a 5 gas analyzer). |
If its hard starting when its cold, but ok when its hot, it could be the csv. most likely culprit in my experience is the temp sensor. the injector itself is pretty ironclad
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good information thanks .. guessing i will leave well enough alone until i get her out on the road and up to temp .. i did jump out the fuel safety switch doesn't make a difference when cold starting. i also tried starting with and without the cold start injector being connected no difference either ... |
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However, I think it contributes less than many think it does. On some CIS systems, it doesn't even come into play until ambient drops below "pretty darned cold" - like temperatures folks aren't choosing to use toy cars in, much less temperatures you're seeing in July in the contiguous 48. I don't know what the 930 TTS is rated at (did look, but could never find it). I do know that my 930 motor would start immediately on the key after being left outside overnight in hard frost, with enough ice (1/2" or more) on the windshield that non-serious screen scrapers were useless. (Factory exchangers would get that steaming within 90 seconds of start on defrost settings though...) And that with no functional CSV. Because sometime in the spring, tracing an intermittent crank issue due to a bad pin 14 connection, noticed the themotime switch was disconnected. Flag terminal just dangling. Eventually, I stopped bothering to put it back on and never noticed any difference, regardless of weather conditions. Yes, I daily drove the car, sometimes in snow. Pretty sure the CS injector did nothing for me the entire time (14 years?) it ran CIS. It usually started from cold just fine. Except for when the original 911 fuel accumulator got a bit tired after 250,000+ miles. |
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You may also find that it'll start better once it has some carbon in the heads. Quote:
Do be aware of time spent cranking it over; think the handbook says 10 seconds or so max, and then let the starter cool for a while (30 seconds?). Dunno, years since I looked at it :D And I've blatantly ignored that advice with no observed ill effects anyway (like to get gas to the injectors the time some muppet at the docks drove it around until he used up the gas it shipped with). If I left mine undriven for a few weeks, it'd sometimes (not often or always) take until the second set of cranking to wake up. If it'd been used 2-3 days ago, it usually seemed to fire immediately, like it was eager to go, LOL. If it'd just been used the day before, it'd either fire immediately (most often) or within a few seconds. |
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[QUOTE=spuggy;11736372]Eh, I know why people fixate on the "cold start injector" circuit. It does seem logical.
However, I think it contributes less than many think it does. On some CIS systems, it doesn't even come into play until ambient drops below "pretty darned cold" - like temperatures folks aren't choosing to use toy cars in, much less temperatures you're seeing in July in the contiguous 48. I don't know what the 930 TTS is rated at (did look, but could never find it). I do know that my 930 motor would start immediately on the key after being left outside overnight in hard frost, with enough ice (1/2" or more) on the windshield that non-serious screen scrapers were useless. (Factory exchangers would get that steaming within 90 seconds of start on defrost settings though...) And that with no functional CSV. Because sometime in the spring, tracing an intermittent crank issue due to a bad pin 14 connection, noticed the themotime switch was disconnected. Flag terminal just dangling. Eventually, I stopped bothering to put it back on and never noticed any difference, regardless of weather conditions. Yes, I daily drove the car, sometimes in snow. Pretty sure the CS injector did nothing for me the entire time (14 years?) it ran CIS. It usually started from cold just fine. Except for when the original 911 fuel accumulator got a bit tired after 250,000+ miles.[/QUOT i found the same with my 74 911s it never worked and never made a difference. This is why i disconnected it on my 76 while looking into the running rich issue so it wasn't a factor |
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Oh, just saw your answers embedded in my quoted text. Let's touch on some of those:
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http://forums.pelicanparts.com/uploa...1657306588.jpg Jim's CIS primer https://jimsbasementworkshop.com/CIS/pages/comp_page.html#aar says: Quote:
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In practical terms, my MoTeC M800 disregards the lambda sensor entirely for 3 minutes after start, doesn't even log any values from it while in C3 (warmup) state. And won't read/use it at all if there's no heater, or the wiring is broken incorrect etc. I'm currently tinkering with my warmup compensation tables without lambda readings, like an animal. "Seems a little rich", followed by (next day) by "bah, overshot, too lean now" etc. It is also, absolutely, important to calibrate the lambda sensor for accurate readings, they do change over time - I also had one foul from fuel contamination. But if you got this as a kit (eg both the gauge and the sensor together), sensor controller/gauge was probably calibrated when you got it. IIRC, you can get the calibration number for the lambda sensor with a DMM too; I did it both ways when I fitted the new sensor, and the numbers were very very close (like within 0.002 V of each other). Also, even when the sensor is up to temp, be aware that a rich misfire (which may not even be audible) will read lean, not rich, on lambda. The clue is when you keep fattening up that cell in the map, and the sensor reads leaner and leaner for each change... Lambdas are a useful tool - but they really don't react instantly and are most accurate for readings in steady-state conditions, although they do give a vague idea of what happens when you accelerate etc. Quote:
I'm sure some folks can do it. I decided I didn't have the patience/skills to keep fiddling and was just grateful it started/ran - and lived with it balking on anything other than very slow/gentle throttle tip-in during the first few miles of warmup. I also don't miss 6-12 mpg stoplight-to-stoplight in town one little bit... HTH - good luck! |
Hello Ned. Jumping in here to say that I am really suspicious of your AFR sensor readings. Are you sure the sensor is properly connected? My AFR sensor (also the bosch) doesn’t begin to read right for about 10 sec or so. For example. If I power the sensor only, with the car cold and off, after around 10 sec, the afr reading starts to change and goes off the scale in about 3-4 more sec.
Also, while the car may run as high as 17 afr, it will be clear to you that it is not happy. Cold starts at 12 afr is not unusual. Car needs to be rich on first startup. That is the warm up part of the wur- low control pressure makes for rich start and pressure increases to lean out as engine warms. My advice is that you double check the sensor. |
Well, TIL (Today I Learned). LOL.
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Not all aftermarket kits have any "motor running" indication - but heating the sensor before the motor is running is apparently a big no-no. Quote:
Or, from the Bosch spec Quote:
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