Need advise...A/F ratio\'s

[Oliver]

A few weeks ago I ran my first dyno test. I mainly wanted to check my A/F ratio\'s, not purely hp numbers.
I went in looking to tune the ratio\'s in the 11.4 area but found out that the tuner\'s computer only plots CO% and Lambda graphs (not like they do in the States) Can anyone help me understand how to tune a/f ratio with system. The tuner does not specialize with rotary motors but he said I should be in the 5.5 to 6.0 range...which I was at 4000 rpm\'s but then it climbed after that. He said I was plenty rich, but until I better understand how to read A/F reading this way. I decided to stop there. Looking at my Lambda he also thinks my O2 sensor may not be working correctly? I am changing the sensor and I hope to make another dyno run soon.
Can anyone help me out here?
Thanks!!

I made 282.7 rwhp at 6185 (11.5psi or .79 bar) and 352.5 Nm at 4849 rpm

[Oliver]

Co% and Lambda graph

[Oliver]

Hp and Nm graph...sorry they are so hard to read.

[Fish]

From my limited knowledge thats very rich.

You dont want to be running at 5/6 AF.  At top end, full throttle you want to be looking at around 9/9.5 and thats still on the rich side. Idle should be around 13.5.

Someone who has been playing with their PFC\'s and wideband please post some figures.

Dan

[Oliver]

Thanks Dan!

Are there any tuners in the UK who can help me better understand how to tune with Co and Lambda?
The only person I have spoken to that might know tuning is Geff at Reworx, what do you think? or there must be some people on this forum who have dyno tested? How do you do it in the UK to read your A/F ?? if some could show me there charts, that might help.


Thanks again,
Oliver

[Oliver]

I found some information with numbers on reading Lambda to a/f readings, near the middle of the page. Looks like a nice unit from australia.
http://www.techedge.com.au/vehicle/wbo2/info5301.htm
 
Still need to figure out how to us the CO chart for tuning?

[maximtaylor]

Right, I shall do my best to help

Sorry in advance if you already know the basics, but I\'ll take it from scratch!!

First off, Lambda 1 = 14.7:1 air/fuel ratio, where a lambda of 1 represents the so called \'ideal\' air fuel mix or stoichometric value (sp?) for cars.

A lambda of 0.9 is the same as an air/fuel ratio of 13.23:1.....but....

Rotarys love fuel, and so do high boost applications, so you need to be richer than this.

When you are off boost ie in a vacumn or neutral state of driving you can aim fairly close to a lamda of 1, as the engine is off load, off boost and low throttle and hence not liable to knock. My car runs between about 14.1:1 and 13:1 off boost

On rolling roads, you are generally looking at the load area of your map, so you are looking to be richer still.

I would recommend aiming for 11:1 a/f or .75 lamda throughout your boost period throughout the rev range. Maybe go a little leaner at about 6.5k revs to about 11.5:1 or 0.78 lambda.

You could go leaner and generate a little more power with about 12:1 a/f or .81 lambda, but one reason that rotaries love rich fuel mixes is because the fuel is partly used to help cool the compressed air charge going into your engine, helping to prevent detonation.

Always err on the side of caution and run rich!

If you go too far rich, any more than 10:1 or 0.68 lambda, you car will start to stutter at about 6k revs (peak load for most rotaries), which will sound like a misfire.

Hope this helps!!!

Regards

Max

[BlitzBoy]

Nice info Max, always wanted to know the relationship between Lamda and Air/fuel ratios, and what is lean and rich for a Rotary

 :cool

[Fish]

Lean is anything above 12.5:1 on boost and rich is anything below 9.5:1 on boost.

Dan

PS. I only quoted on boost, as we only ever drive them that way.

[JimboRX-7]

I\'d be interested to monitor the A/F ratio on my car when it arrives.   Is there a sensor on the car somewhere I can use?  Can I monitor the gas out the exhaust?  Would ideally like to watch it while I\'m driving.  Not particularly interested in getting it done on a rolling road.

I see there are several devices for monitoring the data in the ECU, can I take a reading from there, or do I need a special ECU?

Sorry, but my knowledge is pretty weak when it comes to ECUs and the like.

[20B_boy]

The stock oxygen sensor is a very basic narrow band item - totally useless for tuning.

You need a wide band lambda sensor (and some thing to see the readings it\'s providing on) in order to see whats going on A/F or Lambda-wise.

Max has the MoTeC PLM (professional lambda meter); this is a pucka WBo2 with its own LCD display. They go for between £750 and £1000. You can get cheaper widebands for upoward of about £450 I would say.

Not cheap then :rolleyes:

R.

[BlitzBoy]

looks like we will be renting off Max then, how much ya charging Max??? lmao

[Oliver]

Thanks Max and everyone for your help!

I didn\'t understand the ratio relationship between Lambda and A/F reading until I found the Tech edge website the other day. Now it\'s very clear, and I appreciate the added info Max and Fish. I have always been able to get straight A/F reading from the dyno\'s in the States. But like I said, found out it\'s not done the same here in Denmark.


Fish-
I am still a bit confused with reading C0%??  When I wote 5.5 to 6.0. I was speaking of CO%. I think you thought I was saying A/F ratio?? From 4500 to 6000 rpm\'s I was near or at 9.0 on the CO%.  Everyone here thinks that is rich?? But if you look at my Lambda at 6000 rpm\'s. I am Lean at .85.

One more thing. I veiwed my video tape of the dyno test and noticed the Lambda sensor was coming out during the pull. Maybe?? this had a effect on the reading?? not sure.

I also changed my O2 sensor today. Using my O2 sensor volt readings.
- at idle (with lights on)     0.07 V
- 4500 rpms, 4th gear, 12 psi  1.09 V

Anyone with a PFC ...are you seeing the same volts on the O2??

After work today I visited a friend who just installed the Tech Edge WB unit in his Subaru WRC. It\'s very nice and I ordered one for myself today. This unit should make dyno testing, track days and even emission testing a hole lot easier.

Still, if anyone can explain CO% reading while I wait for the unit to arrive, I would appreciate it.
Thanks again






Sorry for the confusion on my part.

[Oliver]

Here is another Wide Band unit from the States.
http://www.innovatemotorsports.com/lm1.php

Here is a group buy for those who don\'t visit the RX7Club forum?
http://www.rx7club.com/forum/showthread.php?s=&threadid=220439

[maximtaylor]

CO (carbon monoxide) and CO2 (carbon dioxide) are directly related to air fuel ratio.

As a general rule, as CO goes up, CO2 will go down. It is possible to use conversion tables to convert your CO content or CO2 content to an air/fuel ratio.

This method is only generally used for setting up vehicles to within manufacturers tolerances (where they normally quote a standard CO or CO2 level).

For tuning, a good wideband (oxygen sensor) setup is far more accurate.

Hope this helps a little!

Regards

Max