V6 CO Adjusting Screw

[smally Junior Member Find all posts View Profile Close smally]

Does anyone know anything about the CO adjustment screw next to the airflow meter? I'm chasing better fuel consumption.

[smally Junior Member Find all posts View Profile Close smally]

Re: V6 CO Adjusting Screw

I have posted this on 3 forums and not one reply, looks like I am a pioneer with this one! I will be hooking the Prado up to an exhaust gas analyser tomorrow and will check what this screw actually does. Stay tuned ........

[smally Junior Member Find all posts View Profile Close smally]

Re: V6 CO Adjusting Screw

From what I could tell it only altered the fuel mixture at idle. Without a dyno I could only free rev it and the readings didn't seem to alter regardless of the screw position. I plan on fitting a narrow band oxygen sensor and a gauge so I can monitor the fuel mixture on the road. In the meantime I will see what the consumption is now that I have cleaned the throttle body, replaced the spark plugs and air filter and also removed the spring flap from the main muffler. Doing my weekly trip to Broken Hill (430km) on Tuesday and returning home a week later. I will try the trip up at 110 and return at 100 to see the difference that makes. I'd love to be able to get 12l/100 @ 110.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Re: V6 CO Adjusting Screw

Thanks for the info and keep it up.
The best I've had was 12.8L/100km.
I've been thinking about (the lack of) fuel economy recently. Hydrogen has come to mind...

[VL400 Member Find all posts View Profile Close VL400]

Re: V6 CO Adjusting Screw

Ive been doing some testing on mine and a mates petrol V6 with a wideband oxygen sensor for sometime now. There is lots to be had with some tuning..

Cold idle - ~12:1
Hot idle - 13.5-14:1
Wide open throttle - 11.5:1
Cruise - 14:1
Light cruise < 60kms - 13.5:1

And yes that screw is just mixture control at idle.

[westy90 Junior Member Find all posts View Profile Close westy90]

Re: V6 CO Adjusting Screw

I'm probably preaching to what has already been considered and disregarded, but if you convert to lpg, you will reduce your running cost to a little over half of what you now spend. The 3.4 loves the stuff.

Another thing to consider is your oil. I put some Valvoline engine armour semi synthetic blend in it 15-40 and this increased my range on lpg by 15%. Not sure what garbage my mechanic used in it before so I can't directly compare before and after but the range increase in like for like driving was certainly noticable.

Westy

[smally Junior Member Find all posts View Profile Close smally]

Re: V6 CO Adjusting Screw

I have been looking at hydrogen for a few years now myself, for different cars. The main reason I didn't go that way on them was because they used a closed loop fuel system with an O2 sensor and I couldn't see how the system would cope with it (in theory anyway). Given that the Prado is just an open loop system I reckon it could be worth a shot. I know a guy from the Gold Coast that builds and sells them as a hobby so I might be getting in touch with him soon.
My engine oil is due for its first change since I have owned it and was considering going to Valvoline 15/4o Engine Armour. I use it in my Wifes Lancer and it seems ok. Not really convinced on the LPG thing myself, had a few cars over the years on the stuff and was always fiddling around trying to stop backfiring, hard starting etc.
Seeing as how I'm only chasing economy at cruise speeds I may use a narrow band 02 sensor instead of a wide band due to the costs involved. Thoughts?

[VL400 Member Find all posts View Profile Close VL400]

Re: V6 CO Adjusting Screw

Narrowband will show you which side of stoic you are but not a huge amount else, WOT prob see 850mV if your getting 11:1 like mine and around 15.6:1 (approx best cruise economy) might be lucky to get 100mV (generally they flatline at 0v so totally useless).

For wideband controllers I have an LM1, LM2 and MTX-L from innovate. The LM2 has been the worst purchase ever (dont even consider it usable anymore) but the MTX-L the best for permanent install - it was just over $200 delivered to my door thanks to a group buy we organised on a tuning forum.

Still got the issue of making changes to the AFR ... stay tuned for an update on that soon :wink:

[smally Junior Member Find all posts View Profile Close smally]

Re: V6 CO Adjusting Screw

Well that will be the next challenge!

I guess altering the MAF signal would be one way.http://waterforgasblog.com/hydrogen-map ... i-kit.html . I guess these kits are just a trim pot anyway?