Ideal AFR for highway cruising for economy

Hey Guys,

What is the ideal AFR for my RB30 carby on highway for economy, rather than power?

Currently cruising AFR on 60-70km/h is around 12:1, too rich obviously, hence the apparent reason for poor fuel economy and soot.
Not sure, how to go about fixing it, but reckon some carby fiddling involved(and hopefully not the jets :) )

Above is on petrol. Dunno about LPG yet, 'cos the wideband I bought need to connect to a PC to change the fuel type, and I
haven't got the correct adapter for that, yet. It's a real bummer, 'cos if I knew early, I would've bought a one that doesn't need
a PC connection to change fuel type.

Thanx in advance for any advice.

Dom

14.7 would be the one i'd move it to and see, should be good for economy but you will lose power. i always tune the carby by the seat of the pants feeling, gas i use a lamba value.
don't make it too lean.

14.7 is the ideal but close to it would be alright. i've always run my carby's on the rich side for a bit more go.

you should have a mixture screw on the carby, small movements on this until you find the correct reading

Quote:

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Originally Posted by garett

14.7 would be the one i'd move it to and see, should be good for economy but you will lose power. i always tune the carby by the seat of the pants feeling, gas i use a lamba value.
don't make it too lean.

14.7 is the ideal but close to it would be alright. i've always run my carby's on the rich side for a bit more go.

you should have a mixture screw on the carby, small movements on this until you find the correct reading

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Hi mate,

Yes, I used the mixture screw to get idle mixture to 14.7, which is good, but as you know, that has little or no effect on half or wot throttle when cruising or revving for power. I guess(meaning I don't know :) ), when revving high on WOT for power, mixture getting rich is ok?
Cruising AFR is 12 or less. Do you reckon that's not good for economy? (My guess is it is probably not?)
If I wanna fix that to closer to 14.7, how would you go about it, with a RB30 Nikki carby?
The secondary throttle valve doesn't get stuck. Secondary throttle valve is vacuum operated(rather than mechanically operated) in this Nikki carby.

Any tips from you, I would be grateful.

Thanx
Dom

I haven't got to the LPG tuning yet.

One reason is 'cos I don't have the correct adapter to connect the gauge to a PC(It uses serial port, new computers don't have it,
so I need to USB to serial converter adapter, the old laptop I have doesn't work with the Innovate software, I dunno why)

The other reason is that I wanted to make sure I get the petrol side of AFR tuning right first, before I get to LPG.

In the days of old tuning a carb by "ear" meant turning the mixture screw say
clock wise till it spluttered, then you turned it anti clockwise counting the turns
till it spluttered. Then you would calculate how many turns divide that in half.
that was your sweet spot.
or

Rev it to 2000rpm turning the screw [mixture] you could hear the "sweet" spot
very easily,,,,,,,,,lol

Remember you'll never get economy and performance at the same time

Quote:

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Originally Posted by threedogs

In the days of old tuning a carb by "ear" meant turning the mixture screw say
clock wise till it spluttered, then you turned it anti clockwise counting the turns
till it spluttered. Then you would calculate how many turns divide that in half.
that was your sweet spot.
or

Rev it to 2000rpm turning the screw [mixture] you could hear the "sweet" spot
very easily,,,,,,,,,lol

Remember you'll never get economy and performance at the same time

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Thanx mate.

Yes, and I'm only aiming at economy atm on both idling and cruising. It it get rich a little bit on WOT, I'm ok with that,
'cos I think that's way it suppose to be, but cruising AFR of 12 or less is probably not ideal for me atm.

There's a backyard carby tuning procedure for RB30 in Gregory's manual. Basically, I turn the mixture screw all the way in until it seats, the back down anti clockwise four turns or so. Then adjust the rpm to 800. Then keep turning the screw in until I get the highest idling rpm. Stop the mixture screw at that spot &
set the idling rpm to 800 or so using idle speed screw. The engine has to be warmed up before the above.

Now, I don't need to do that 'cos of the wideband gauge.

I'll try the mixture screw technique above and see how it goes.
I didn't try it before, 'cos i was told at cruising and above, idle mixture screw doesn't play an vital part in AFR.
Another thing I thought about was that even if the idle mixture screw affect the cruising AFR, I would still have to find a
happy medium between idling AFR & cruising AFR by turning the mixture screw.
I hope I won't have to, and hopefully can keep idling AFR & cruising AFR as separate settings.

Thanx
Dom

Quote:

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Originally Posted by dom14

I haven't got to the LPG tuning yet.

One reason is 'cos I don't have the correct adapter to connect the gauge to a PC(It uses serial port, new computers don't have it,
so I need to USB to serial converter adapter, the old laptop I have doesn't work with the Innovate software, I dunno why)

The other reason is that I wanted to make sure I get the petrol side of AFR tuning right first, before I get to LPG.

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What operating system on the laptop and have you a link 2 the Innovate software?????

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Originally Posted by NissanGQ4.2

What operating system on the laptop and have you a link 2 the Innovate software?????

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The software says it's compatible with Win2k to Win10, so I'm assuming it's a 32bit software application. My desktop has no serial port, but an old laptop does(winxp), but the software demands to upgrade to
DotNet 4, which refuses to install DotNet4 in the end of the installation. I haven't had a chance to muck around with the old laptop software issues to find out
the exact reason. So, I'm waiting to get hold of a USB to serial adapter which I haven't had a chance due to Easter weekend.

This is Innovate website link to the software.

http://www.innovatemotorsports.com/support.php

It refuses to install saying it needs DotNet 4, and then DotNet 4 Installation craps itself in the middle.

Innovate software application installs fine on my Windows 7 machine. It's a 32 bit software application.

Carby's obviously had issues with idle circuit as well. Today it's running AFR 10 on idling, which indicates it's not just cruising throttle issue.
It's running rich like hell on idling, and the mixture screw does not respond at all.
Carby's getting heaps of petrol into the intake via something other than idle circuit, I think.
I wonder what that is!!!

Check your float levels :P
For a carby rb30 for good eco and running you should be around:
Idle- 14:1
Cruise:14.3-16:1 Depending on what your motor can take
WOT:12.8:1

Quote:

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Originally Posted by johno90

Check your float levels :P
For a carby rb30 for good eco and running you should be around:
Idle- 14:1
Cruise:14.3-16:1 Depending on what your motor can take
WOT:12.8:1

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Yeah, I adjusted the float to be around quarter of the sight glass, which improved the mixture "super" rich issue, but it's still too rich.
Soot build up is way way too much inside the combustion chamber.

Now, I have a real PITA problem with the Innovate MTX-L wideband gauge.
The damn thing won't work with the software.
I need to change the fuel type to LPG, so I can tune the LPG system, but still haven't been able to do that.

What carb is it running? Stock or something else?

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I bought a USB to Serial adapter to use the Innovate gauge with a windows 7 machine.

At this stage I dunno whether it's a software issue or an adapter issue.
Either way I'm getting the below message.
The software( LM Programmer ) won't recognize the gauge at all.
I assumed the sensor need connected, so I plugged the sensor into the gauge as well.
I powered the gauge using a 12v battery.
Everything was done according to the guide in the manual.

Since my windows 7 desktop hasn't gota serial port, I used a USB to serial converter adapter, as guided by the user manual.
The adapter was a good quality one from Officeworks.

This is really frustrating.

If I knew any better, I would NOT have bought this particular gauge, and instead would've bought a one that doesn't need a PC connection to change the fuel type. It's too late now.

Typical usb adapter. Boot the computer up with forced hardware signature disabled then plug in adapter. Then power up the gauge. Then open the program.

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Quote:

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Originally Posted by johno90

Typical usb adapter. Boot the computer up with forced hardware signature disabled then plug in adapter. Then power up the gauge. Then open the program.

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Windows 7 is not detecting the adapter or the gauge, at all.

Yes.... try booting up with hardware sig disabled. Its a windows 7 and on security thing. Even if its plugged in windows will disable it and shut it down. You have to disable it to let the chip run. Smash the f8 button when u boot ur computer and it will give u options for startup pretty sure its the last one :)

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Quote:

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Originally Posted by johno90

Yes.... try booting up with hardware sig disabled. Its a windows 7 and on security thing. Even if its plugged in windows will disable it and shut it down. You have to disable it to let the chip run. Smash the f8 button when u boot ur computer and it will give u options for startup pretty sure its the last one :)

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Finally, got it going mate.
The damn adapter was stuffed, hence the reason for windows for not detecting the adapter at all.
I got it replaced & still it took quite a bit of fiddling for the driver to get to work.
Absolute PITA these wideband gauges that need PC connection with PITA adapters to do something simple like switching the fuel type.
Never again I would buy something like this without doing some homework on it.

Would hate to think what mine is running at. Can smell the fuel out the exhaust at idle haha. When I turn the idle mixture screwn, nothing happens, it never seems to seat - I'm guessing something is broken.

But, it keeps running and I don't have the time to strip it, or the money to pay someone to do it, so I've just gotten used to that lovely petrol smell at idle :P

nothing better than that petrol smell in the morning...

the old laser i had you could smell the petrol in the car behind...

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Originally Posted by Throbbinhood

Would hate to think what mine is running at. Can smell the fuel out the exhaust at idle haha. When I turn the idle mixture screwn, nothing happens, it never seems to seat - I'm guessing something is broken.

But, it keeps running and I don't have the time to strip it, or the money to pay someone to do it, so I've just gotten used to that lovely petrol smell at idle :P

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i wouldn't touch the idle mixture screw at all if I'm you mate.
Even with Gunson Colortune spark plug, it was absolute PITA to tune it or even try turning it.
It's with the wideband AFR gauge now I'm getting a good picture of what's happening inside the combustion chamber.
Both carbies are stuffed and need some serious work on them to get them to run anywhere near AFR, either on idling or cruising.

If the idle mixture screw keeps turning without seating, probably it's was turned too hard in the past and the thread is damaged.
You can take it out completely(don't lose the spring & tiny rubber washer) and examine the thread.

Follow the Gregory's manual temporary carby tuning procedure that I mentioned above to tune it.
Your carby should be in good nick 'cos it's been running on petrol only and the low kms on it.

Quote:

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Originally Posted by garett

nothing better than that petrol smell in the morning...

the old laser i had you could smell the petrol in the car behind...

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And the diesel smell in the morning, it's like smelling cocaine in the morning, so wonderful. ;) :D

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Originally Posted by johno90

What carb is it running? Stock or something else?

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Stock Nikki carby that comes with RB30 Patrol. It's been running dual fuel since the beginning.
So, the carby's not in the best condition, I think.