Lambda/tuning Sensors in a KZ or shifter kart


(Jason Allan) #1

Does any one have any experience with using a lambda sensor or tuning lights with a KZ or shifter kart?
After a quite frustrating weekend racing KZ, seizing 2 motors with no apparent cause apart from them running lean, (Going progressively richer all weekend) I am thinking of putting a bung in the exhaust and running sensor just to see what is happening. Just a little warning before a 1 way ticket to the sand trap would be helpful.


(Marin Vujcich) #2

Watching with interest. Have a friend in the same predicament. Mychron do a nice wide band kit.


(Nik Goodfellow) #3

Lamda sensors are nice if you know how to read them. I’d be more concerned that something else is going on for you seize two KZ engines while going richer.

I’d consider rebuilding you carb (giving its a good clean) and rebuilding the fuel pump. Then check there are no air leaks in the fuel system.

Where in the cylinder did it seize? By that I mean, front, back round the exhaust ports, did it nip or did its seize around the half the circumference of the cylinder?


(Jason Allan) #4

All you are saying is correct and will be checked/rebuilt.
Do you have any experience using lambda sensors in KZ?


(Mat Nipperess) #5

Hi Jason

I’m running KZ2 and I am using an Exhaust Gas Temperature sensor. When I first got involved in KZ2, the chap who sold me the kart basically said to me “don’t even think about putting in a Lambda sensor. Some guys have tried the Easi-Tune and Supa-Tuna stuff and the sensor cracked the exhaust” and at $800 a pipe, I’d rather not do that. Most KZ2 pipes should have a small thread near the exhaust port on the engine. That is for the EGT sensor. I’m running a Modena KK-1 and I normally aim for between 570 and 590 degrees celsius and run the engine at around 50-55 degrees celsius on the water temp.
Out of interest, what engine are you running?


(Jason Allan) #6

A BMB, which has been quite good up until now.
I would just like to know if it works. $150 worth of insurance, is not expensive in my opinion.


(Mat Nipperess) #7

The EGT works very well and is used by amateurs all the way up to the professional teams. Most data loggers will have an EGT option. I don’t know anything about the BMB engine, so, I would talk to an engine builder about an EGT target range. It would probably be around the 580 degree Celsius mark, but, I would ask first.
As I said, the Lambda probably works, but, it will crack your exhaust. The sensors are just to big for the exhausts and the exhausts are made really thin. $150 for a Lambda sensor realistically is the path to an $800 bill.


(Andrea Nieri) #8

BMB is a good engine. Laudato was very fast in WSK in 2013.


(Andres Malovos) #9

Curious what you ended up trying? I have a Lambda on a CR125, and it’s a handy way to know you’re not risking the engine with AFR.


(Jason Allan) #10

@Andrace I have not got the engines back yet. A mate of mine is rebuilding them for me, both barrels needed re-coating with nikosil, and it was cheaper to re-coat them rather than to re-barrel. I should hopefully get them back in the next couple of weeks.
I spoke with the manufacturer of one set of tuning lights and they think that oxygen sensor should work fine in the KZ, and I have picked up a cheap exhaust to use the sensor in, just in case it does crack the exhaust.

The reason I have gone with the tuning lights over another way, is because the Mychron that I have on the kart will not accept another data input and I have experience using the tuning lights I am going for. They are cheaper than replacing a working Mychron with a unit that has all the bells an whistles.
I suppose also in the back of my mind is that most of the other input types are a number, where to me tuning lights are doing a job for me, converting numbers to an outcome. I know it’s still the machines interpretation of a number but it takes a little bit of thinking out of it for me.
I will be sure to update when I get it back to the track.


(Andres Malovos) #11

I think the lights are a great way to go. When I check on track I’m glancing down to see is a value above or below 1.0, so lights doing the same would be handy, and perhaps, easier to see as well.

What kit are you going to run and does it log?


(Jason Allan) #12

Supa tuna is the kit, the guy that makes them is, in my opinion a super smart bloke, and has done a heap of R&D on them. They don’t log any values, I’m not that data hungry at this stage. The lights are nearly too bright at night (I’ve had to turn them off on the rare occasion I’ve been out at night with them) so the are really easy to see most of the time.

It will be interesting to see the different stages of throttle ranges working and being indicated by the lights, hopefully it will also be a good tool for driving style etc. actually using the whole of the throttle range rather than just flattening the throttle and hoping for the best. Something I have been working on, so to be able to see it rather than guessing should be a great help.


(James McMahon) #13

It will be interesting to see what the Supa Tuna guy has to say about partial throttle. It’s not uncommon for unburned gases and fuel to pass into the exhaust under those operations. That’s one of the reasons you often just can’t jet out four cycling at partial throttle. The cylinder isn’t being filled fully and the pipe is also not in it’s ideal state to hold the charge in the cylinder until the exhaust port closes.


(Jason Allan) #14

I managed to recover one of my BMB barrels without having to have it re-coated and was able to run the engine again with a Lamba sensor in place. However…

It is a good thing this is not the Kart I race regularly.
After bedding in the new piston I took it out for another run and midway through the last session it again seized. The tuning lights I installed were showing a good tune, and I was running a rich set up in the carby. The piston was weird, showing signs of both being rich around the edges and lean at the top of the dome. I showed it to some people I believe to be very good at this sort of thing and even they couldn’t really explain why.
Of course it also tore through the coating, so the quick fix I thought I had has moved through to the more expensive send away and re-coat both barrels.

So yes, there is obviously something wrong somewhere and I’m going to get everything looked at again, top to bottom and fingers crossed next time out will be more fun.


(James McMahon) #15

Possible causes… without seeing it.

Too much ignition advance
Spark plug heat range too hot
Too low octane fuel
Stale fuel

Throw up some pics of the skirt and crown. Plug and head too.


(Jason Allan) #16

It happened in November last year and my phone has died in the mean time, so I’ve lost those photos. My engine builder is onto it


(Paolo Nunzio Licary) #17

First guess would be intermittient fuel delivery based of the going richer and sticking comment. One person already mentioned fuel pump or lines but also check that the floats in the carb didnt get bent when handling. May be hanging up now and then if the g’s or vibrations are just right. If the engine has sat for a while pull the fuel line and hit the carb fuel inlet with brake clean to make sure the float valve isnt gummed up.


(Alie Leite) #18

Hi…in my case when I first got involved in KZ2, the chap who sold me the kart basically said to me don’t even think about putting in a Lambda sensor. Some guys have tried the Easi-Tune and Supa-Tuna stuff and the sensor cracked the exhaust” and at $800 a pipe, I’d rather not do that.

assemblage PCB


(James McMahon) #19

People tested on track and on dyno with a wideband, which is the most ideal. Of course leaded fuel reduces it’s life significantly, but that doesn’t mean there’s no value in testing with it

You’ll have to throw conventional wisdom on reading the numbers though, unilike a four stroke you’re pulling air into the exhaust chamber as well as sometimes losing it along with fuel out the exhaust port.

So rather than tuning by the ratio number, you’ll be tuning by other factors and noting the ratio.


(Thomas Williams) #20

I have done it with excellent effect on 4 stroke motorcycle engines (motocross) for Keihin FCRs. It was mainly helpful for tuning partial throttle jeting, something not as critical in kart motors. A concern on a 2S is that the the extra oil will gum up the probe and ruin it in short order.