Lambda gauge / Air Fuel Ratio experience

David Oslo · Post by **David Oslo** » Fri Nov 28, 2014 2:17 pm

I am considering mounting an Lambda / AFR gauge and sensor.

Has anyone done this and have any experience to share?

I'm wondering how much of a 'toy' it is during the first day, does its job in terms of getting engine, timing, carbs, needles etc to run optimal. Then it's just static and gathering dust. More of a workshop tool (say like Colourtune and Carb Balancer) than something to have permanently wired onto the car.

Comments ?

christopher storey · Post by **christopher storey** » Fri Nov 28, 2014 2:52 pm

I have not done it, but if you are going to do it on a Jaguar, you really need 2, one for each downpipe , and even then they are not ideal on an E type because each pipe is fed by 2 carburetters, any adjustment of the centre carburetter affecting both pipes' readings ( as to a lesser extent do adjustment to the carburetters at either end because of the balance pipes in the inlet tract )

David Oslo · Post by **David Oslo** » Fri Nov 28, 2014 3:28 pm

Yes I am considering 2 sensors and a selector switch before the AGR unit.

I am also considering putting just a single sensor in the single bore section of exhaust given that I am 'blessed' with that section on my 2+2. Reasoning being that if modern cars can manage with one lambda sensor then so can I. Would have to be ultra careful to get the three needles identically fitted, bridges adjusted identically, and air balanced. Got the tools to do that already.

Hence the lambda would be reading an average for all three carb settings, e.g. average burn ratio for entire engine. As my boss (himself former Chief Engineer at Rolls Royce) used to say "engineer it down to the 'good enough' level".

jag68 · Post by **jag68** » Fri Nov 28, 2014 8:28 pm

Hi David

I had one in my E Type race car. Only one as the headers went into a single pipe on a side exhaust. Didn't find it was of much use really. A look at the color of the exhaust exit and a spark plug check was better. If you follow the manual tuning instructions and use a stock needle in your triple SU's and tune to a smooth idle you've got it right (carbs will be balanced and mixture strength right for the needle) , and you probably can't get it any better by using a sensor. If you can't get it to a smooth slow idle you probably have something wrong with the carbs / fuel level etc. Jaguar did all the hard work for you when they picked the needle. You can vary the air fuel ratio under power (not at idle) by changing the needles but the sensor is not going to help you decide what's "best". For example are you looking for economy (thicker needle) or power (thinner needle)? For that you need a dyno.

Of great assistance in tuning your car is a hand held infrared thermometer used as a final test. Check that the temps of each exhaust header near the head are similar. Variations are generally caused by minor mixture imbalances carb to carb. Leaner mixtures are generally hotter than richer mixtures. Also air flow volume on carbs not in sync will cause temperature variations.

Terry

Post by **Heuer** » Fri Nov 28, 2014 9:09 pm

Everything Terry and Christopher have said. Only way you can really get value is if you have tubular manifolds and drill every other to take a sensor. No need to use three sensors at once, you can do one SU at a time. They are really only of value to confirm you have set things properly - mine has been used on a couple of occasions. Spend your money elsewhere unless you really like gadgets.

christopher storey · Post by **christopher storey** » Fri Nov 28, 2014 11:19 pm

David Oslo wrote:
Hence the lambda would be reading an average for all three carb settings, e.g. average burn ratio for entire engine. As my boss (himself former Chief Engineer at Rolls Royce) used to say "engineer it down to the 'good enough' level".

That sounds like Ken Lea ??

David Oslo · Post by **David Oslo** » Sun Nov 30, 2014 3:24 pm

Thanks for advice, makes common sense. My "lambda" money has already been spent multiple times on other stuff :D So I have no problems to toe the line and follow the best advice :D Maybe the kids will get a Xmas present now....

Cheers!

KingRichard · Post by **KingRichard** » Sun Nov 30, 2014 5:30 pm

Hi, any experience in what temp to get at correct set idle?

Richard

jag68 · Post by **jag68** » Wed Dec 03, 2014 6:28 pm

Hi Richard I use the infrared thermometer only to balance the carbs and as I currently have headers and Webers as opposed to stock manifolds etc I suspect my absolute temperatures would not be of universal application. Maybe of more importance I haven't tuned the car since spring and can't actually recall what the temperatures were. (I recollect that they were between 450 - 600 f) If you run SU's set the car up according to the procedures in the manual and get it idling as best you can. Then take the temperatures. They should all be within 50 -100 f of each other. If not adjust the individual idle mixture screws to equalize. Do not expect that the pipes coming off each of the two cylinders serviced by one carb to be the same. The unequal firing order as between the two cylinders in each pair means one cylinder will be richer than the other - so temps will mildly vary, but you can tell which carb is different from the others and adjust if necessary. As an aside I've always found that # 1 and #6 cylinders run cooler for reasons I can't explain.

Terry

David Oslo · Post by **David Oslo** » Wed Dec 03, 2014 7:36 pm

Check out the temperatures on these exhaust stubs (on another great british engine)

Skip to 3:30 to see them up to temperature and then enjoy the noise. You can see a few pipes colder than the neighbours.

KingRichard · Post by **KingRichard** » Thu Dec 04, 2014 5:41 pm

Hi Terry,

I took the opportunity to take the measures before reading your mail. First I also find numbers 1 and 6 to be a slight cooler. So, that can be confirmed. My readings were between 225 degrees Celsius to 260 degrees Celcius (437 F to 500 F). So well within a reasonable range of each other.

By the way I have wideband sensor; I like gadgets, sorry :D

You can see a vid here:
https://www.youtube.com/watch?v=0nGdvh4YP60

I tried different settings to see what effect it has. I know that our engines don't like running at stoich (14.7) at all. Best is around 13. I has little use in setting idle other then checking it is around 13 or so. But during driving you can monitoring what is going on. I learned a lot by it, which is part of the hobby. I have UB needles instead of UM.

I now set idle by measuring dept of the jet at about 1,2 mm as start and fine tune by driving and by colour of spark. Not to sooty, grey color and even on all 6.

Thanks,
Richard

jag68 wrote:Hi Richard I use the infrared thermometer only to balance the carbs and as I currently have headers and Webers as opposed to stock manifolds etc I suspect my absolute temperatures would not be of universal application. Maybe of more importance I haven't tuned the car since spring and can't actually recall what the temperatures were. (I recollect that they were between 450 - 600 f) If you run SU's set the car up according to the procedures in the manual and get it idling as best you can. Then take the temperatures. They should all be within 50 -100 f of each other. If not adjust the individual idle mixture screws to equalize. Do not expect that the pipes coming off each of the two cylinders serviced by one carb to be the same. The unequal firing order as between the two cylinders in each pair means one cylinder will be richer than the other - so temps will mildly vary, but you can tell which carb is different from the others and adjust if necessary. As an aside I've always found that # 1 and #6 cylinders run cooler for reasons I can't explain.

Terry

jag68 · Post by **jag68** » Fri Dec 05, 2014 11:02 pm

Hi Richard
Your engine runs very sweetly at idle. Wish mine was like it! Your choice of needle is interesting. As I'm sure you are aware it's a little bit richer than the stock needle at the mid and top end. All the needles we'd use in an E Type are the same at idle (same thickness at the idle station on the needle). The stock needle (UM) is quite lean. My experience is that these engines generate the most power the richer they get (UO needle) - and happily pink and detonate less as well.

PeterCrespin · Post by **PeterCrespin** » Sat Dec 06, 2014 12:45 am

KingRichard wrote: You can see a vid here:
https://www.youtube.com/watch?v=0nGdvh4YP60

Idles nicely but I thought your starter had stuck in engagement. What's the whining noise Richard?

Pete

christopher storey · Post by **christopher storey** » Sat Dec 06, 2014 10:49 am

Gearbox very, very noisy Peter - he silences it at the end of the video by depressing the clutch pedal

KingRichard · Post by **KingRichard** » Sat Dec 06, 2014 6:07 pm

Hi all,

Absolutly correct diagnoses Christopher. It is the gearbox whining. It is waiting to be rebuild next year in summer (I hope); it will also get an overdrive, which I already rebuild. Pete advised about the overdrive when buying from eBay 1,5 year ago. All new rebuild parts came from Sheffield; great service, great fun to rebuild.

It makes a lot of noise, but the gearbox works normal and no difficulty in shifting.

I now are happy with idling, but still can't get smooth rpm. Rpm waves from 680 to 760 or so. Perhaps it is as it should be.

I picked the UB needle after much reading on this forum (EDIS thread) and Jag lovers. I find UB a bit better to get idle less richer and having better mixture up the range mid and top. With UM my idle must be set way to rich to get good mixture at the end. After installing the UB's I learned much more, so I still have the idea of putting the UM back and see again what the differences are.

Regards,
Richard

christopher storey wrote:Gearbox very, very noisy Peter - he silences it at the end of the video by depressing the clutch pedal

jag68 wrote:Hi Richard
Your engine runs very sweetly at idle. Wish mine was like it! Your choice of needle is interesting. As I'm sure you are aware it's a little bit richer than the stock needle at the mid and top end. All the needles we'd use in an E Type are the same at idle (same thickness at the idle station on the needle). The stock needle (UM) is quite lean. My experience is that these engines generate the most power the richer they get (UO needle) - and happily pink and detonate less as well.

Woolfi · Post by **Woolfi** » Wed Jan 28, 2015 11:48 pm

I have a lambda sensor wide band in my V12 6,0 L permanently. The motor is from a XJ81 limousine with the e-type runners and the 4 Stromberg. Without the lambda sensor it is absolutely unpossible, die grind the 4 needles for perfect mixture. Without the lambda i have been blind. Checking spark plug colour or colorune does not help really.
If your motor and the exhaust system and the air filter is original, you don't need lambda measuring. If you change silencer or air filterig system you need lambda sensor or you get information about the best fitting needles from another e-type owner, who has the same systems on his car.
If I prepare a race car, I dont need exact lambda information. I make the mixture fat, fat, fat. If you are driving an OTS with fat mixture, your girlfriend soon will not enter anymore the car, because she smells very bad for exhaust gases.
My EV12 is running with AFR 16 at part throttle very well. The sparks plugs are bright gray, the smell is low and the gas consumption is roundabout 18 - 22 mpg when crusing. This is a very low gas consumption for a V12 (5-gear Getrag + 2,88 diff).
If somebody is sending his email to me, I can send information about lambda sensoring of roundabout 10 pages. Very interessting. Written in a car magazin from a car enthusiast, who has been told from experienced mechanics many times, that lambda sensoring is not neccessary.
Lambda sensoring is much more exact than "popometer" ( checking the kick in the ass, when accelerating).
For me it was the best "tool" I evey had bought for my EV12. Innovate LC-1 for roundabout 170 pound.
It is NOT possible, to run one gauge with two lambda sensors, changed by a switch. If I remeber correct, the normal narrow band sensor is becomming demaged soon, if it is not connected to the electronic system. Maybe it is possible to avoid damage, if the sensor, which is not connected to the measuring system, is connected via a resistor to negativ earth. I think this issue has to be claryfied, before mouning two sensor with one gauge in a car.
I know a lot of V12 owners, who have a sports exhausr system in the cars. The cars are loosing ponies, because the mixture is becomming leaner at half or full throttle. Without "reshaped" needles the motor is not running well. For this reshaping a lambda sensoring system ist absolutely neccesary. I have tried it in the beginning to do this without lambda sensoring. The result has been far away from good. I saw this, after I had mounted the lambda system to the car.
iKind regards Wolfgang Gatza

KingRichard · Post by **KingRichard** » Thu Jan 29, 2015 5:48 pm

Hi Wolfgang,

There are systems you can connect 2 sensors to. See TechEdge or 14point7 for dual units (perhaps others). But I guess you knew that. But you are of course correct you can't switch 2 on one gauge, because the sensor has to be heated or destroyed.

I recently checked my springs in the carbs. Way too soft (2.5 and 2oz). So replaced them with new correct springs (4.5 oz). I immediatley saw a richer mixture on my gauge. I replaced my UB needles back to UM and the difference again was huge (A/F 11.5 to 14.5 difference). I think I couldn't have seen the difference without my O2 sensor.

I send you a pm for the article. Many thanks.

richard

MarekH · Post by **MarekH** » Thu Jan 29, 2015 7:41 pm

Dear Richard,

I think that might need a little clarification:- the lambda sensors being referred to here are all wideband lambda sensors. These all need to be fitted in tandem with their controllers which accurately regulate their operating temperature. The controller will then output a linear signal of 0 to 5v representing very rich (~8:1) to very lean (~22:1) air to fuel ratio. Leaving a sensor mounted in the exhaust without its controller will damage the sensor.

The output signal from the controller can then happily be displayed on a gauge or datalogged and you can display, mix, process or ignore the signals as you like.

Another reasonably common feature, though usually proprietary to each wideband controller manufacturer, is to output the signals digitally via a CAN signal which can also be fed to a gauge or datalogger if it has the corresponding interface.

The other (older style) lambda sensor is a narrowband sensor which has a non-linear output and does not regulate its temperature with a controller. (It is still heated though.) The two can be differentiated easily as the widebands all have at least a five wire connection but the narrowbands a maximum of four wires - two for the signal and two for the heater connection. These heated but non-regulated sensors typically just feed into a car's ECU to tell it which side of rich or lean the mixture is. As such, they are rarely if ever used for tuning purposes.

The hand held thermometer to measure exhaust gas temperature ("EGT") as mentioned by Terry should be used with caution. The characteristic curve of temperature versus air fuel ratio ("AFR") is a parabola, so you also need to know which side of rich or lean you are as to where you stand with temperature - you can measure the same number and be lean on one exhaust port and get the same reading but be on the rich side of the curve on another. At the top of the curve, the same reading may appear over quite a band of AFRs. The reading will also vary with load and rpm.

As an example, on my v12, I have twin widebands mounted in place of the crossover tube plus individual EGT sensors embedded into the cylinder heads at the former air injection ports. The whole lot is sent digitally to a datalogger over the car's CAN network and it neatly shows up ignition or fuelling inconsistencies and problems on a per cylinder basis. (The car runs a Megasquirt-3 sequential dual fuel petrol and lpg setup.)

Using these tools to set the mixture at idle is really only ever a proxy for wanting it to be correct under load and at varying rpm. If your needles and jets are old and worn then the result may not be as successful as you hope as you aren't measuring it when it really matters..

kind regards
Marek

Woolfi · Post by **Woolfi** » Fri Jan 30, 2015 12:04 am

Hello Marek !
Very interessting to read about the EGT in yor motor. I am thinking also, to mount a EGT-sensor in the holes of the cast iron exhaust runners.
- How is the temperatur if you drive 3 minutes full throttle, if the mixture is lets say AFR = 12,5 - 13,5 (rich) for best torque and safe exhaust gas temperature ?
- How is the temperature if the car is running 3 minutes full throttle with a lambda of 1 ? This is too lean for full throttle.
- Which Lambda have you "adjustetd" with your injection for full throttle ?
- Have you ever tried to mount a knock sensor system to your V12 motor ?

Regards Wolfgang Gatza

KingRichard · Post by **KingRichard** » Fri Jan 30, 2015 7:06 am

Hi Marek,

I think we say the same.

I mean they need to be connected with their unit/controller for power or else they will be damaged because carbon built up can't be burned of. I understand the question was 2 sensors a switch and one controller, so by switching there is in fact only one sensor connected. But there are dual units meant to be with two sensors.

The only option is only wide band sensors. I have a Bosch 4.9 installed. Narrow band are in fact useless for direct A/F ratio when driving.

I have a MAP sensor (for load) built in and can also connect rpm in my controller/unit, so I can log A/F, rpm and MAP in one graph. Still playing with it. On basis of that I'm trying to get the best A/F in relation to needle or make my own needle (see Des Hammills excellent book).

I also want my ignition advance to be included in the log. I have a 123/TUNE. I don't know how to do that. Of course can see advance and log when using the software from 123/TUNE, but I want to combine it in one graph/log.

Richard

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