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Air Fuel Ratio Readings
https://www.ausmini.com/forums/viewtopic.php?f=2&t=94003		 Page 1 of 2
Author:  IndigoBlueCooperS [ Sun Oct 16, 2016 3:57 pm ]
Post subject:  Air Fuel Ratio Readings
What AFR readings do people get from their Minis? That is old technology A series, with SU's and distributors with springs that work.
I have a big bore with single 1 3/4 worked road engine. Needle is KV, RE83 cam.
Under load it is often around 13, 14, and full load high speed sometimes up to 15, 16. A little leaner than I would have liked, but will it do damage?
Cruising is 13, 14 so happy with that.
On over- run / take your foot of the accelerator down hill it goes up to 30 or 40. Is this standard?
This is using a Innovate LM1 wide band meter.
What are peoples experiences on the road?
Author:  drmini in aust [ Sun Oct 16, 2016 5:30 pm ]
Post subject:  Re: Air Fuel Ratio Readings
Full load aim for 13-13.5 with an SU.
KV should be richer than you have.
Author:  simon k [ Mon Oct 17, 2016 8:33 pm ]
Post subject:  Re: Air Fuel Ratio Readings
Where are you testing from? is it with the O2 sensor in the tail pipe?

I have a similar setup - 1275 + 0.72", RE83, HIF44 but my static compression is low - around 9.5:1, I'd set it up for boost but took the blower off

I'm using a BBC needle, which shape-wise is similar to your KV, but leaner across the board. You probably have the KV set up with the top of the jet very close to the bridge?

Is the nylon plug that keeps the piston from touching the bridge intact? the piston should be sitting 1mm up from the bridge, funny things happen if it can fall all the way down

Any idea what spring you're using?

needles compared: http://www.morrismini.com/SUNeedlesV2.a ... &size=.100

I can't remember what needle I started out with, but it was like you described so I researched and came up with the BBC. The only problem with that was too lean on cruise so I sanded it around S6,7,8 which cleaned it up. There's a distinct change in shape you can see on the chart

Now I get idle at around 12, cruise & normal driving at 14.5 and power in the 12-13 range
Author:  oldblade [ Mon Oct 17, 2016 8:47 pm ]
Post subject:  Re: Air Fuel Ratio Readings
I had to look up what a "Innovate LM1 wide band meter" was so thank you now i need one
Author:  IndigoBlueCooperS [ Mon Oct 17, 2016 8:55 pm ]
Post subject:  Re: Air Fuel Ratio Readings
I found the main problem. The needle was an OA6, not the KV, which explains why it was on the lean side.
So I will try the KV again and maybe something between the two.

But what do you guys see on the over run - when you take your foot off going down hill?

I am testing from the tail pipe so the idle readings don't mean much, but the rest should be good.

Thanks for the reply's.
Author:  simon k [ Mon Oct 17, 2016 9:07 pm ]
Post subject:  Re: Air Fuel Ratio Readings
indigo wrote:
The needle was an OA6, not the KV, which explains why it was on the lean side.


it sure does explain it!! I didn't want to say "are you sure you have that needle??!!"

I get a rich (11:1 ish) spike on overrun (like reaching the peak of a hill then backing off over the other side), then it leans off to a normal mixture after a few seconds

oldblade wrote:
I had to look up what a "Innovate LM1 wide band meter" was so thank you now i need one


get one of these instead, install it permanently... pretty gauge to look at...

https://www.diyautotune.com/product/inn ... auge-3802/
Author:  drmini in aust [ Mon Oct 17, 2016 9:28 pm ]
Post subject:  Re: Air Fuel Ratio Readings
IndigoBlueCooperS wrote:
I found the main problem. The needle was an OA6, not the KV, which explains why it was on the lean side.
So I will try the KV again and maybe something between the two.

But what do you guys see on the over run - when you take your foot off going down hill?

I am testing from the tail pipe so the idle readings don't mean much, but the rest should be good.

Thanks for the reply's.


Laingy went through all this recently, from OA6 to KV then to others. it's running real good now, I'll post tomorrow what he's using.

As for wideband meters, I put an Innovate MTX-L into a Jaycar box so it's portable. Probably cheaper than LM-1.

Image
Author:  IndigoBlueCooperS [ Mon Oct 17, 2016 9:41 pm ]
Post subject:  Re: Air Fuel Ratio Readings
I like something portable so that I can use it on different cars. Plug one end in the exhaust and the other in the cigarette lighter.
Author:  oldblade [ Mon Oct 17, 2016 9:48 pm ]
Post subject:  Re: Air Fuel Ratio Readings
so how do you plug it into the Exhaust all the ones i am looking at are screw in how do you make that portable
Author:  DOZ [ Mon Oct 17, 2016 10:52 pm ]
Post subject:  Re: Air Fuel Ratio Readings
oldblade wrote:
so how do you plug it into the Exhaust all the ones i am looking at are screw in how do you make that portable


Make a tube to clamp inside the end of the exhaust and weld sensor thread bung into it...

or buy one https://www.amazon.com/Innovate-Motorsp ... B000CO9MF8

Image
Author:  IndigoBlueCooperS [ Tue Oct 18, 2016 9:10 pm ]
Post subject:  Re: Air Fuel Ratio Readings
This is what I use on the exhaust. Basic but works - only down side is the need to put an extension on it to check the idle mixture to overcome the "hunting" from the cam. (I put the clamp on properly when it is on the road).

Image
Author:  drmini in aust [ Tue Oct 18, 2016 9:40 pm ]
Post subject:  Re: Air Fuel Ratio Readings
Here's mine- pipe is 1" OD, spud nut is M18.
It slips into the tailpipe.

Image
Author:  Laingy [ Tue Oct 18, 2016 10:12 pm ]
Post subject:  Re: Air Fuel Ratio Readings
I'm using an RB needle in an HS6 on a stroker 1387cc with 1.3 roller rockers & 10.4:1 CR. The KV needle was used for dyno testing the motor on its own - it didn't matter how much fuel was being used as long as the engine didn't "starve", and produced as much output as it could. But when it came to road use, the KV was just too rich. I did go from an RE83 cam to a 266SS cam also and this gave an even larger torque curve - can pull away in 4th from 1500 rpm. The air/fuel ratio is 11 - 13 which is spot on according to Doc.
Author:  simon k [ Wed Oct 19, 2016 10:49 am ]
Post subject:  Re: Air Fuel Ratio Readings
Laingy wrote:
I did go from an RE83 cam to a 266SS cam also and this gave an even larger torque curve - can pull away in 4th from 1500 rpm.


I think I'm going to do the same for my next rebuild....
Author:  Laingy [ Wed Oct 19, 2016 2:14 pm ]
Post subject:  Re: Air Fuel Ratio Readings
simon k wrote:
Laingy wrote:
I did go from an RE83 cam to a 266SS cam also and this gave an even larger torque curve - can pull away in 4th from 1500 rpm.


I think I'm going to do the same for my next rebuild....

It was GR's recommendation when I had to do a rebuild due to ring failure at 2600km - one hell of a shock, but with GR's pistons and Nippon rings all seems to be ok, and the cam is that much better too.
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