So I finally get my Racepak O2 sensor and module working and currently set up to read lambda, what is a recommended value to look for at WOT, 548 BBC on gasoline. I don't plan to make any changes to the tune up just yet, just want to gather some data and see where we go from here. I feel like the car is lean, I did make a jet change several weeks ago and picked up 2mph, so I still believe it is on the lean side. Any help with suggested starting point is appreciated.
The trend seems to be going toward using lambda. I have never used that scale, and have always used the gasoline scale....even when running alky. It is just the scale that I have history with.
It really makes no difference if you are starting from scratch other than talking with other people about it.
Foxtrot Juliet Bravo
If max power is your goal jet it to get the best MPH and use that number....
.85 is around 12.5 on the gasoline scale. .8(rich) to .87 approx is starting point. Every motor is different and even changing O2 sensors will give you a different lamda #.
Hopefully Greg Kelly will chime in on this.This message has been edited. Last edited by: 790G T/D,
|DRR Top Comp|
I to use the gas scale and run alcohol. I also tune to best MPH and ET and THEN read the O2 and use what ever that number is to tune in the future.
For me on my car the best performance is 12.9 to 13.10 but yours may be significantly different. Just like tire gauges are different and if you use a different gauge you may be way off what you normally run.
-a type of Cognitive bias where people with little expertise or ability assume they have superior expertise or ability. This overestimation occurs as a result of the fact that they do not have enough knowledge to know they don't have enough knowledge.
Before you argue with someone ask yourself, "Is this person mentally mature enough to grasp the concept of a different perspective?" If not there is no point to argue.
4X NE2 CHAMPION. 2020 TDRA NE2 Champion
IMO Bucky stated the scales exactly right.
I always recommend using the scale for the fuel you are using just to be able to better work with your carb or injection guy.
And yes, time slip is king; more MPH = more power (same wind, weight etc).
I'd like to see you on the gas scale, make a pass, record everything, put the jets back to the previous setting, verify the 2 mph loss (compared to 20 minutes before) and then keep making it richer till mph falls off. then post the MPH and O2 numbers.
AF's are a great tool.
Since you say you are running on gasoline, I would chose to use A/F as your scale. Do as the other posters have said, and you stated, make some passes and start gathering data!
Lambda is simply a calculation of the stoichiometric value of the fuel you are using, and the actual A/F you are running at.
AlkyIROC has a spreadsheet that shows you different Lambda values at various A/F ratios. As you can see, you still need to know your actual A/F, plus you need to know the correct stoichiometric value for the fuel you are using.
That value is not the same for all fuels. Gasoline has various Stoich values, as do different types of Alky. You must check with the manufacturer for those numbers if you chose to tune via Lambda numbers.
Stick with A/F numbers, much easier!
From past experience, I have found that the higher the octane I run, the leaner I need to run it for the same overall performance. I have never found that running higher octane than needed hurt performance, once tuned to use it. I don't touch timing, only A/F.
Typical pump gas has a Stoich value of 14.7, therefore for a Lambda of 1.000, you would run your engine at 14.7:1 A/F. Under load, you will melt it. A safe target would be 12.5 to 13.0, depending on the combo and application. For a long tow uphills, this would be a terrible target, going down the track, nice and safe.
But a higher power higher compression engine using race fuel, completely different! Mine would barf at that! I have to run mine 13.0 to 13.5 for best performance, on Sunoco Blue. If I have to run Sunoco Red, that changes things I have to run it 13.5 to 13.8 to keep the performance the same.
So read your timeslips, look at your pipes and plugs, they will point you in the right direction!
Wow I really appreciate all the comments, I watched Greg Kellys videos last night and learned a lot. I had already printed out AlkyIROC spread sheet and have it in my logbook. I don't have any experience with A/F or Lambda, this is my first time with Racepak. I bought this dragster turn key several months back, but the previous owner had replaced the Terminator on methanol with a gas dominator, but never took the car out. The fuel system was new all the way from the tank to the manifold. The track testing was disappointing at first, but some timing changes and launch RPM adjustments, we picked up almost 4 tenths in one afternoon. We then focused on fuel system, a slight regulator pressure change saw a small improvement, but collector color told me we were still lean, fairly consistent but lean. During this time the O2 sensor never produced any meaningful data, and at one point stopped working all together. Many phone calls to Racepak and finally returned the V300, O2 sensor and module. The V300 is pretty old and had outdated firmware, the O2 sensor was dead and the module was intermittent. Now that I have all of it back and working it's time to use this tool to see what the A/F or Lambda are doing. Timeslip and collector color have been my only tools up till now, hopefully the data collection will pay dividends, thank you again to all that provided input, I love this forum.
|Powered by Social Strata|