How are you calibrating / adjusting for water injection AFR?

[Forum Admin]

The injection of water and alcohol mixes in the induction system will dilute the exhaust and alter the partial pressures being measured by wide band lambda sensors.

I have not been able to nail down the exact degree or amount of potential error - though feed back would suggest that a meter would read leaner than the actual induction mix is.

Has anyone calibrated or otherwise adjusted their readings for water injection?

[willwren]

I never felt the need to. My aftermarket chip seems to have made enough of an adjustment to my MAF readings to make up for the small amount I was injecting.

As I get my new system going, I'll be watching my AFR like a hawk. My solution, should I need one, will probably be the ZZP Mini-AFC controller.

[Philip]

Hi,
when I eventually get my engine blown Im going to keep the water off whilst tuning, retard ignition to help avoid deternation during boost. Then turn the water on and see what happens to the AFR from my WB sensor. Will let you know how much it changes. Ive programmed the ecu to turn off lambda correction during water injection, but do you think the readings will be constant? What I mean is if I find out what the AFR is when water is on can I set that as my target or will it vary due to things I haven't thought of like temperature, etc?
Phil

[AKWRX]

What I mean is if I find out what the AFR is when water is on can I set that as my target or will it vary due to things I haven't thought of like temperature, etc? Phil
Using the "conventional wisdom" tuning to a target AFR when injecting alcohol, or a water mix does indeed introduce all kinds of new variables. The oxygen sensor data via either A/F, or Lambda units, is affected by many new unknowns. Determining a target A/F ratio in advance of the tuning process may be beyond just difficult. After wrestling with this issue for some time (until my head hurts from reading), the complexities are more than I would like to tackle.

So, my approach will be a more practical, proven path to tune directly from real time peak cylinder pressure, and adjust its position in the power stroke with the iginition timing. The optimum A/F ratio should essentially just fall out by default. It is an "end run" way to figure out the best A/F ratio. From that point, A/F will just be used to monitor the tune for safety purposes only. The techique is well established (Formula 1, Indy, NASCAR, top fuel dragsters, etc.), only the hardware is very, very expensive. Once I can afford the $1250 pressure sensor (spark plug integrated), a DIY system may be able to be put together for about $2K total cost. Anyhow, that's the plan...

[Forum Admin]

Alternative fuels will definitely move the reference point for sensors calibrated to gasoline.

Additional steam in the exhaust will mess with diluted partial pressures.

I have been corresponding with someone that understands the impact very well - but that does not make it measurable. He basically said that anytime you are really relying a lambda you should calibrate it, the best way to do so is with a gas analyzer. Of course that only works with catless systems.

As I thought about this I was talking to someone about the idea of using water injection eliminating unburned hydrocarbons from the induction charge. And I started wondering about skipping the lambda sensor and just using a gas analyzer. Theorectically, with water injection I want to tune right to the point where the CO is minimized - that should be the maximum power mixture. The person I was talking with mentioned not to my surprise that there are quite a few performance tuners who tune to CO rather than lambda settings for any number of reasons but they find it quite accurate for what they seek to do.

I might realize some things on my own some times but rarely will I have been the first to realize it. :)

[Philip]

Hi,
So is it OK to tune the AFR with the water off using the WB Lambda, then turn the water on and then dont use the Lambda sensor for AFR correction while water is on? That was my original plan, or do I need to use a gas analizer to retune when water is on?
Phil

[Sato]

Hi,
So is it OK to tune the AFR with the water off using the WB Lambda, then turn the water on and then dont use the Lambda sensor for AFR correction while water is on? That was my original plan, or do I need to use a gas analizer to retune when water is on?
Phil

Please forgive my ignorance but couldn't you get just as good results by monitoring the EGT's closely and use a scanner to see if timing is being pulled by unheard detonationby the computer? I understand that air fuel ratio is a good tool but you can detonate still even if your in a so called safe zone because of poor fuel,,high ambient temps etc.
I would think that knowing when detonation happens would dictate any setup's variables,,timing/fuel,water jet size,etc. I have a AFR guage;not the kind you speak of though but it's the last thing I check after EGT's and knock with a scanner. Fill me in on this sensor
Sato

[AKWRX]

Tuning from EGT does not work that well once you are injecting water, or alcohol, and are taking advantage of the more agressive ignition advance injection allows because of the higher knock threshold. As ignition is advanced, EGTs will always decrease (without any other tuning changes), because the cylinder combustion process simply has more time to be more complete before the exhaust valve opens. EGT is better used as a reference point for A/F changes, and as a safety monitoring input after everything is tuned.

[Sato]

Tuning from EGT does not work that well once you are injecting water, or alcohol, and are taking advantage of the more agressive ignition advance injection allows because of the higher knock threshold. As ignition is advanced, EGTs will always decrease (without any other tuning changes), because the cylinder combustion process simply has more time to be more complete before the exhaust valve opens. EGT is better used as a reference point for A/F changes, and as a safety monitoring input after everything is tuned.

In my application more advance simply brought on detonation on my scanner AT THE DYNO] WHAT IS INGNITION ADVANCE INJECTION?
Ingition[too much]advance WILL cause an increase in egt's if it it's advanced enough! As will retarded base timing!
EGT's can go up from too much advance as well as to little advance!!
I have heard of guy's advancing the timing too much and blowing up their engines,,,and it ain't cause the egt's went down. YOU CAN DETONATE WITH TOO RICH A MIXTURE ALSO!!!l ALWAYS DECREASE EGT'S WITH MORE ADVANCE IS VERY INCORRECT!
You have not told me why this AFR is the way to go with this new sensor.
So far I do not agree. You can waste a motor at low throttle and boost if the conditions are not corect LIKE LATE OR EARLY TIMING WITH THE INCORRECT FUEL RATIO AND IF SEVERE ENOUGH IT WILL DO IN THE MOTOR INSHORT ORDER
I still feel that the REAL SENSOR IS THE KNOCK SENSOR,,,AS YOU CAN TALK ALL YOU WANT AND DO ALL YOU WANT BUT IF THE FRICKEN THING DETONATES ON A SCANER BEFORE YOU HEAR IT ,,,,THAT IS THE DETERMINING FACTOR.
I DON'T CARE WHAT AFR SENSOR YOU GOT PLACED ANYWHERE,,IF IT DETONATES YOU GOT A PROBLEM.
SATO

[Sato]

One last thing, if the AFR read ok at a given rpm./boost //advance //etc
BUT, my scanner showed that the computer sensed detonation and pulled 10 degrees of timing out of cylinder#1 ,,6 degrees out of cylinder 3 and less in the other two cylinders........what sensor would you believe?
This has happened to me and others and I'm sure many others that don't even know it because they don't have a scanner. They just use a cheap i will admit AFR sensor with a stock O2 sensor[4 wire],,but it reads rich.
Many don'y understand that if you know when knock happens and how much timing is being pulled ,,you could run alot less boost and make alot more HP!!! When detonation is sensed by the computer it takes ALOT of ingition retard and time to remove it . By then the race could be over!!\
The whole purpose in my mind is to never have the computer remove ANY timing at ANY time. Once it does you have comprimised the whole performance aspect of the car. And without the proper info[like a computer scanner to read the cars brain] most will never know it and perhaps add more boost or timing because they haven't HEARD any detonation and all the while the computer is retarding the timing BIG TIME to save the motor
Please fill me in on this AFR sensor,,,what the hell does it do excactly? And how is it more informative than a knock sensor as far as the bottom line goes?
Thanks,
Sato

[Forum Admin]

An EGT reading will tell you that you are in a dangerous state - but it doesn't tell you why. It could be timing or fuel ratio.

AFR readings from anything other than a wide band lambda sensor is pretty much uselsess. When people talk about monitoring AFR for engine tune - it should be with a calibrated wide band limbda sensor.

A wide band lamda sensor measures partial pressures in the exhaust to interpret the components of your induction charge. Unlike O2 sensors which are only accurate around a very narrow range near stoic a good wide band lambda can provide you with your AFR from 10:1 to leaner than 20:1 - if it has been calibrated for your fuel inputs (i.e. gasoline, methanol, propane, etc.) and has been calibrated for any water injection rate (since water injection dilutes the partial pressures and apparently tends to cause readings closer to stoich than truly exist).

In knock limited tuning situations, most setups have known AFR limits. For instance a given engine may run fine at 20psi and 11.25 AFR at MBT with 93 octane, but need to be at 11.00 AFR with 91 octane and 10.50 AFR with 89 octane. This is why many prefer to tune by AFR - the target is known from many uses. Once you are at the target AFR the tuner is able to tune to MBT. This becomes the "preferrred" tuning and monitoring tool for tuners that want to run at MBT and use fueling levels to suppress knock.

Yes if you run past MBT you will get knock at appropriate AFR levels even rich AFR levels.

With water injection and other knock suppressing technologies AFR no longer becomes a target - but a result. Without knock limits you can tune for maximum AFR power - using either a dyno or cylinder pressures. Then you can advance from there to MBT.

There is no single best monitoring tool. EGT is a quick check if everything is OK, but will not tell you what exactly is out of tune fuel or timing. AFR is good only if you know what your AFR is supposed to be for the components your charge mixture in the cylinder (including correct octane) and the sensor is calibrated for your charge mixtures. To the extent possible good quality knock monitoring with timing retard will protect your engine - but does not necessarily resolve a bad tune.

[Philip]

Hi all,
the trouble with knock detection is if your engine hasnt got a system on it, like mine hasn't, then i think its very difficult to detect as the after-market systems Ive heard of are a compromise, so im led to beleive. I did hear of a chap who recommended making a tube with a horn type of arangement on the top and bolting that to the cylinder head to amplify any noises, but thats a bit impractical in my mind,
Phil

[Brad]

That is a good way to detect knock. The Aquamist manual for the 2s installation gives directions for doing that.

[Philip]

Brad,
Im sure your right but would it amplify it loud enough to hear it while driving do you think? Also my bonnet line is close to the engine so they would need to be quite small,
Phil

[chevyeater]

If you don't have knock detection a Steelman Chassis Ear or something similar would be a good listening device. Comes with headphones, an amp etc..

[Brad]

A peice of copper tubing smashed on one end and bolted to the block with a doctors stethascope(?) connected to the tube. Have seen this used on a chassic dyno by the tuner.

[AKWRX]

EGT's can go up from too much advance as well as to little advance!! I have heard of guy's advancing the timing too much and blowing up their engines,,,and it ain't cause the egt's went down. YOU CAN DETONATE WITH TOO RICH A MIXTURE ALSO!!!l ALWAYS DECREASE EGT'S WITH MORE ADVANCE IS VERY INCORRECT! SATO
Of course, too much ignition advance and/or bum A/F ratios can raise EGTs to dangerous levels (and increase risk of engine damage from knock). My comment that EGT will always be reduced with more ignition advance with injection of alcohol or water, is ONLY up to the point of not exceeding the new injection produced knock threshold while maintaining the proper A/F. That's a tuning common sense given, but guess I didn't stress that completely enough. TuboIce has explained it much better in his response above.

[Philip]

Brad,
I like the sound of the idea, especially as its quite cheap and not too difficult to do, would anywhere on the heads do to bolt it on? As I have 2 heads, no im not a monster (wife probably disagree) I assume i could just connect both copper tubes together with a tee peice and use some form of ear peice connected to that?
Phil

[Brad]

Philip, Any where will be fine. the nosie will travel through the engine. A head bolt or a place on the block will do. The is a company, Diamond Racing that has a knock sensor the taps into the water jacket. It can be adjusted for sensitivity. I gives a 0-5 volt output as knock increase. Do not beleive they have a web site. The price is about $600.00.

[Philip]

Thanks Brad,
$600 is a lot of money compared to a bit of copper tube, so I think I'll try that,
Phil

[Sato]

An EGT reading will tell you that you are in a dangerous state - but it doesn't tell you why. It could be timing or fuel ratio.

AFR readings from anything other than a wide band lambda sensor is pretty much uselsess. When people talk about monitoring AFR for engine tune - it should be with a calibrated wide band limbda sensor.

A wide band lamda sensor measures partial pressures in the exhaust to interpret the components of your induction charge. Unlike O2 sensors which are only accurate around a very narrow range near stoic a good wide band lambda can provide you with your AFR from 10:1 to leaner than 20:1 - if it has been calibrated for your fuel inputs (i.e. gasoline, methanol, propane, etc.) and has been calibrated for any water injection rate (since water injection dilutes the partial pressures and apparently tends to cause readings closer to stoich than truly exist).

In knock limited tuning situations, most setups have known AFR limits. For instance a given engine may run fine at 20psi and 11.25 AFR at MBT with 93 octane, but need to be at 11.00 AFR with 91 octane and 10.50 AFR with 89 octane. This is why many prefer to tune by AFR - the target is known from many uses. Once you are at the target AFR the tuner is able to tune to MBT. This becomes the "preferrred" tuning and monitoring tool for tuners that want to run at MBT and use fueling levels to suppress knock.

Yes if you run past MBT you will get knock at appropriate AFR levels even rich AFR levels.

With water injection and other knock suppressing technologies AFR no longer becomes a target - but a result. Without knock limits you can tune for maximum AFR power - using either a dyno or cylinder pressures. Then you can advance from there to MBT.

There is no single best monitoring tool. EGT is a quick check if everything is OK, but will not tell you what exactly is out of tune fuel or timing. AFR is good only if you know what your AFR is supposed to be for the components your charge mixture in the cylinder (including correct octane) and the sensor is calibrated for your charge mixtures. To the extent possible good quality knock monitoring with timing retard will protect your engine - but does not necessarily resolve a bad tune.

I understand now . Thanks for the info but how do you find one,buy one and have it calibrated?[lamda sensor] What info do you need from the car? How much is this sensor?
Like you said I refer to my stock O2 sensor last after EGT's and a scanner for knock. I let the knock sensor with timing retard in my computer be the safety valve and never pull timing in any of my attemps at tuning.
Looks like I have much to learn about this!
Sato

[Sato]

Hi all,
the trouble with knock detection is if your engine hasnt got a system on it, like mine hasn't, then i think its very difficult to detect as the after-market systems Ive heard of are a compromise, so im led to beleive. I did hear of a chap who recommended making a tube with a horn type of arangement on the top and bolting that to the cylinder head to amplify any noises, but thats a bit impractical in my mind,
Phil


I don't know if you're interested or not but J&S Electronics makes a very good stand alone knock retard system. I had used one for a race computer that did not use a knock sensor at all. It will pull timing on all cylinders at once or individually. You can program it to pull timing at different rates at the sign of knock. It also has a guage that will tell you if knock is detected and how much timing is being pulled and from what cylinder. Since it's stand alone it can be used on any car with or without computers. It costs about 450 dollars or so. I have heard of them on Ebay for 200.
Sato

[Forum Admin]

There are many places that sell wide band lambda sensors.

My prefered ones because they work as well as high end ones are the one that was developed from a DIY board and is sold by Tech Edge:

http://www.techedge.com.au/vehicle/wbo2/default.htm

And the new one from Innovate that just won the best new product at SEMA:

http://www.innovatemotorsports.com/

Innovate has a mailing list on their product and would be a good place to ask questions about AFR and lambda readings and how to use them as a tuning tool.

http://autos.groups.yahoo.com/group/InnovateLM1/

[Brad]

The DAK1 from Mechtech is what I use. Lots of things can be recorded at one time. www.mechtech-ms.com/html/dak.html
Wide band O2, boost, EGT(4 if you want) air temps, oil temps, throttle position, MAP sensor output and a lot more if you get creative.
I have recorded 30 minutes at a time the only limit is the size of your labtop computor.
By recording so many things at one time you get a true picture of what is going on and why.

[Philip]

Brad,
I use the DIY-WB (NTK Sensor) it works very well but only gives 0-5V signal out, but the Megasquirt ecu it feeds then gives me the facility to monitor and log all the sensors you talked about. Cost me under ?300 for everything.

Sato,
I would be interested in a knock detection system, even if it were for the future, any idea if they have a website?

thanks
Phil

[Sato]

Sato,
I would be interested in a knock detection system, even if it were for the future, any idea if they have a website?

thanks
Phil

Here's the website. This guy used to work for Hughs aircraft electronics I believe before starting his own company.
Sato
J&S electronics in CA
www.jandssafeguard.com

[Brad]

Philip,
My data logger is moved from car to car. It has tuned 10 different cars the the last 6 months, but I am going to check into the WD O2

[Philip]

Brad,
that sounds like a good system, couldnt change mine between cars due to it being a function of the ecu. This is a link to the WB I use, its probably the least useable type about as it only has the output coming from it, no programmable stuff on it, but it is cheap and it works, just depends what you want and how much your willing to spend,
Phil
http://www.diy-wb.com/

[pbonsalb]

Consider a knock monitor. There is an inexpensive kit out there that works well on cars equipped with knock sensors and that can be tuned for ones that do not have them. I have one and it works well. It cannot retard like the well respected J&S Safeguard, but it is much cheaper and will alert you to knock via an LED.

http://www3.sympatico.ca/borism/

Philip Bradley

[Philip]

I have looked into that one, but surely youve got to make the engine knock so you can tune it for the knock or do you just tune it onto the edge of triggering when engine running without knock?
Just thinking I could add the input into my ecu, write a bit of code that would retard ignition by a fixed amount if knock detected, I do have the MSD 6BTM unit as well that I can dial in retard against boost, so if light still on I could then dial in some more, worth thinking about I think. Might order one after Xmas and have a play,
thanks,
Phil

[Forum Admin]

With a properly implemented water/methanol injection system, you should be able to arrive at maximuum power AFR and MBT without ever experiencing knock.

I tune without water injection to the threshhold of knock and then pull back a bit to find my base tune that I revert to in the case of a WI system fault.

Generally I only monitor for knock during tuning - I use this:

http://home.netcom.com/~bsundahl/knock/sound/KnockSounds.htm

And the DIY knock cans:

http://home.netcom.com/~bsundahl/knock/listen/listen.htm

I attach this to my tuning computer while tuning.

Of course I am relying on my ECU's knock sensing / timing retard response if I cross the edge somehow.

[Philip]

Thanks, that seems the easiest to use and I could just keep an ear peice in whilst tuning and listen out for anything unusual. Would be a very nice facility and peice of mind whilst tuning. Where would you recommend putting the mic? I have a V8 so would it be possible to bolt it onto the inlet manifold?
Thanks again really pleased with that suggestion as it would be very cheap,
Phil :lol:

[Forum Admin]

This particular DIY relies on a factory knock sensor and taps into its signal. I use my laptop amplifier to listen in.

Another DIY that includes information on building one with a microphone -

http://www.autospeed.com/cms/article.html?&A=0353

If you do not have a factory knock sensor the mechanical one brad mentioned also works very very well and likely would be easier than building one with a microphone unless you already have the audio electronics skills.

You can get a stethoscope and tubing routed to a 4" copper tube with 2" flattened and a hole in the end for bolting to the engine.

The intake may work but attaching to the block would be preferable.

[blown408]

I made that DYI unit it works great and it is very cheap to make, try radio shack.