Megasquirt Only runs good with really low AFR's
Thread Starter
Full Member
Joined: Nov 2001
Posts: 206
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From: Springfield, MO
Only runs good with really low AFR's
Okay, here's my setup:
Premixing 64:1 for break-in purposes
No oil injection
S4 13b rotors and housings
S5 irons
intermediate iron ported to match stock secondary ports
exhaust ports matched to S4 exhaust sleeves
Holset HX35W 60mm 7-blade turbo
Extensively modified eBay exhaust manifold
Mazdatrix 4.5# racing flywheel
Quartermaster 5.5" 2-disc clutch
4x 800cc injectors
AEM 35-5130 Wideband gauge and controller
I've disabled AFR integration for initial tuning purposes (an automatically-correcting computer makes it hard to manually correct a VE table). Heres the deal: For whatever reason, this car refuses to run well with an AFR higher than ~12.4:1. If I trim things out to any thing around 13:1, it starts hunting and the AFRs go wild from 13 to 16. I'm only tuning idle and low-load part-throttle at the moment. Any ideas? At around 12.4:1, I get a nice, steady idle and snappy response. It doesn't burn my eyes like mace, nor is there any smoke.
The only thing I can think of is that I've got a non-standard HEGO setup (35-5130 analog gauge, not the digital gauge), but I calibrated to the voltages specified, and the MS is seeing the same AFRs as the gauge shows. I have no reason to believe the gauge or sensor are malfunctioning, but who says the AFR sensor is accurate, or even the correct one, right? I bought it new on eBay, and it looks authentic.
Anyways, maybe I'm freaking out over nothing; I honestly have limited knowledge regarding tuning, but everything I've heard says to tune for around 12.8 - 13.2 for an idle and low-load conditions.
Thoughts?
Premixing 64:1 for break-in purposes
No oil injection
S4 13b rotors and housings
S5 irons
intermediate iron ported to match stock secondary ports
exhaust ports matched to S4 exhaust sleeves
Holset HX35W 60mm 7-blade turbo
Extensively modified eBay exhaust manifold
Mazdatrix 4.5# racing flywheel
Quartermaster 5.5" 2-disc clutch
4x 800cc injectors
AEM 35-5130 Wideband gauge and controller
I've disabled AFR integration for initial tuning purposes (an automatically-correcting computer makes it hard to manually correct a VE table). Heres the deal: For whatever reason, this car refuses to run well with an AFR higher than ~12.4:1. If I trim things out to any thing around 13:1, it starts hunting and the AFRs go wild from 13 to 16. I'm only tuning idle and low-load part-throttle at the moment. Any ideas? At around 12.4:1, I get a nice, steady idle and snappy response. It doesn't burn my eyes like mace, nor is there any smoke.
The only thing I can think of is that I've got a non-standard HEGO setup (35-5130 analog gauge, not the digital gauge), but I calibrated to the voltages specified, and the MS is seeing the same AFRs as the gauge shows. I have no reason to believe the gauge or sensor are malfunctioning, but who says the AFR sensor is accurate, or even the correct one, right? I bought it new on eBay, and it looks authentic.
Anyways, maybe I'm freaking out over nothing; I honestly have limited knowledge regarding tuning, but everything I've heard says to tune for around 12.8 - 13.2 for an idle and low-load conditions.
Thoughts?
MegaSquirt Mod
Joined: Sep 2004
Posts: 4,721
Likes: 1
From: Maryland
I've always tuned about 12-12.5:1 at low load and idle. Some have said advancing the timing a bit can make it run on leaner mixtures but I've had the best luck at idle for example with 5 ATDC timing and around 12.3:1 AFR.
The incorporate AFR feature doesn't enable closed loop, it just multiplies the requested AFR into the fuel equation so that after tuning, if you want to change the AFR, you just change the AFR table instead of messing with the VE table again.
Ken
The incorporate AFR feature doesn't enable closed loop, it just multiplies the requested AFR into the fuel equation so that after tuning, if you want to change the AFR, you just change the AFR table instead of messing with the VE table again.
Ken
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