O2 Clamp

Discussions relating to Turbochargers, Superchargers, Induction, Engine Mods, Exhaust Mods, and other items specifically to make your MX5 or Roadster put out more power.

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WideOpenThrottle
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O2 Clamp

Post by WideOpenThrottle » Sat Oct 09, 2010 8:44 am

Hi to all-i had a lovely OE but now i am itching to tinker with my project so i would like to know if i can build my own O2 clamp & does anybody have the relevant info?
Much appreciated :D
1989 NA 1650
1998 NB 1800
2005 NC 2000
1990 Landcruiser
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SLYDIT
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Post by SLYDIT » Tue Oct 12, 2010 12:30 pm

youll need a pressure switch that operates at about 2-3 psi. a small pcb mounted relay and some elctronics bits...i'll try and find a circuit diag of mine.
The factroy fuel mapping runs off the O2 sensor even at full throttle up to about 4000rpm so when you get into boost and add fuel the ECU tries to pull out all that fuel as it sees the rich mixture. Adding an O2 clamp tricks the ecu into thinking everythings ok so it doesntpull out all that extra fuel that you SHOULD be adding in via bigger injectors or a rising rate fuel pressure regulator.
basically how it works is that when you go into boost and the boost switch operates it switches the relay from the o2 sensor to a fixed voltade of about 0.35-0.40 volts. this voltage is not to rich and not too lean so the ecu stabilises the fuel mixture.

what you need to make is a voltage divider circuit to generate the 0.40 volts.i used a 5 volt regulator and a few variable resistors so i could tweak the voltage.
RED '90 TURBO.
SCARING PRIUS DRIVERS SINCE 2002

broomfish
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Post by broomfish » Tue Oct 12, 2010 9:00 pm

sounds like your pretty clever on that stuff so i wonder if i can run an ongoing problem past you for your thoughts.

i have an NA8 auto and it had a problem that it lost power after driving for 50km or so. it felt like it was running out of fuel and in neutral with foot to the floor it revs to around 4500rpm and no more. stop on the side of the road for a few minutes and it clears for a bit

so i replaced the fuel filter and pump and pressure regulator and drove 100km up and down the motorway and it seemed ok.

we went to the snowball run and it started playing up after 150km so i tried a few things and found that unplugging the AFM fixed the problem. That night when it was cold i had to replug the AFM as it ran like crap, and talking to a guy at the run he mentioned the o2 sensor runs via the AFM so i unplugged the o2 sensor and it ran great for the day round the mountain and the 360km drive home

then last weekend we were driving to the club run and got about 40km and the same thing happened again!

I have removed the fuel pump relay and the contacts didnt look so good so i was going to replace that, but then i read your post and wondered if from your obvious knowledge of the circuitry if you might offer a alternative viewpoint?
regards

Peter Lee
Broomfish
www.broomfish.co.nz

sprsta
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Post by sprsta » Wed Oct 13, 2010 7:33 pm

hi peter

have you tried checking any trouble codes?
try disconnecting the battery
this might help
http://www.miata.net/garage/Engine_Diagnostics.html

cheers

cole

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