AFR Tracking questions

TrinaBabe · Nov 7, 2005, 06:28 PM

I just ordered this unit earlier today. Honestly, my only real reason for getting it is the ability to toss the maf but the AFR tracking does make me curious on how it works. I am assuming that it simply modifies the maf signal to constantly keep the AFR at the correct (Set) point. Im just very curious to see how it works, what options you can have it set to, ie. Autotrack AFR start at 5,000, end at 9,000rpms only if tps =>80% You get the idea at least... how do you turn it on and off automatically? HOW good is it really? I can get my AFR to exactly where I want it repeatedly with the UTEC easily but I also am installing an alcohol injection system so if this is honestly very good at what it does perhaps it could be a failsafe to the alchy? If it is, that right there would help market the hell out of your product. If it can compensate fast enough to keep the AFR in line even if alcohol fails, granted the boost would be too high to sustain it for long but the loss of the fuel would be the first line in the destruction so providing this could help save motors.

Also, this is for the creators of the product... You should really make a psuedo-guide on how to adjust the VE of your specific vehicle. Like, adding more aggressive cams will usually alter the VE rise at higher RPMS and lower at low, etc.... maybe make a few maps for people to start with? Another good idea would be a how-to on how to calibrate the system closely by adjusting the VE until you can match the stock MAF pretty well before throwing it away completely. Just an idea.... Since I will be doing the latter I may end up writing up something to help others do it. I would write up some info on the first part but I already have aggressive cams, large turbo, intake manifold, etc..

Anyways, those are just some ideas.

I also have a simple yet effective log parser to measure my relative gain/loss in HP without a dyno so once I get it working I will post up my relative gain/loss in HP after tossing the MAF. I am guessing somewhere in the 5% range but we will see. I will also do it with an intake, without an intake but with a filter and lastly no intake and no filter. I will also show the difference in spoolup on paper with graphs. Granted, all of my findings will probably be amplified because I have a large turbo and lots of mods.

TurboBob · Nov 7, 2005, 06:58 PM

The AFR tracking has enable settings for TPS, RPM, and MAP. It has target AFR setpoints for 2000 - 8000 RPM, and an % shift for when the aux input is activated.

There is a gain setting to control how agressively you want it to track the AFR's. It works very well.

There is a screenshot posted on Full Throttle showing the afr tracking compensating for alky.
http://www.fullthrottletech.com/showthread.php?t=1213
I did not have the aux input connected, so the Pro had to deal with a large dose of additional fuel. It would perform as a failsafe to the alky to the limits you have programmed. Perhaps a lean-out failsafe needs to be added to the future feature list. I.e. cut the engine off if it leans out past 13:1 for 1 sec over 20 psi....

Documentation has been an ongoing project, your suggestions are good ones. Keep them coming.

Bob

TrinaBabe · Nov 7, 2005, 07:49 PM

Well your failsafe idea is actually a very good one even I didnt think of

Considering it also can act as a boost controller you could have it progressively step until finally shutting down (ie a limpmode) so first, attempt to catch AFR, second drop off boost, third and finally shutdown motor. I dont know but that is a neat idea to work with. I can see you guys taking leaps and bounds from here. Is any part of your coding open source by any chance?

I am wondering about the TPS, RPM and MAP settings, Can you actually set it on only if two or more variables meet the condition you set or is it only done by one? And what does % shift mean for an aux input? I am assuming aux inpout would be something like nitrous or alchy injection by what do you mean by % shift... would that be an automatic gain or drop in fuel? And about the gain setting... I would have thought it just uses a cap on the max percent it will modify to hold the AFR but you do it through a gain level. So I am assuming the gain level is how much percentage each step it will take... low gain = .5% every sample high gain = 3% every sample?

TrinaBabe · Nov 7, 2005, 07:53 PM

The only reason I am somewhat apprehensive about using the auto track AFR option is because I am currently using the Utec to cheat the Ecu. Using your product would be cheating the Utec... cheat enough times and youll get cought so to say

The reason I am thinking it should work fine is because I can tune the Utec using the MAP sensor to judge the load % and not the MAF Hertz... if it was using Hertz I could see serious problems of the translator dropping and raising the hertz levels between multiple load levels screwing with my timing map. But since I can use the MAP load site instead of MAF I should be fine.

TurboBob · Nov 7, 2005, 08:11 PM

Quote:

Originally Posted by TrinaBabe

Well your failsafe idea is actually a very good one even I didnt think of

Considering it also can act as a boost controller you could have it progressively step until finally shutting down (ie a limpmode) so first, attempt to catch AFR, second drop off boost, third and finally shutdown motor. I dont know but that is a neat idea to work with. I can see you guys taking leaps and bounds from here. Is any part of your coding open source by any chance?

The multistep function is a good idea, depending on how long you want to allow the over-limit condition to continue...... but configurability is the name of the game.
Open source.....? no, but I am happy to "bench - engineer" anytime.

Quote:

Originally Posted by TrinaBabe

I am wondering about the TPS, RPM and MAP settings, Can you actually set it on only if two or more variables meet the condition you set or is it only done by one? And what does % shift mean for an aux input? I am assuming aux inpout would be something like nitrous or alchy injection by what do you mean by % shift... would that be an automatic gain or drop in fuel? And about the gain setting... I would have thought it just uses a cap on the max percent it will modify to hold the AFR but you do it through a gain level. So I am assuming the gain level is how much percentage each step it will take... low gain = .5% every sample high gain = 3% every sample?

The enables are ANDed together. If you set any of them really low, you are just left with the other two (and so on). The aux % shifts the target AFR by the programmed %. The gain setting is essentially a control of how fast the algorithm will correct. The algorithm is a "proportional gain integrator" of my own design if that makes any sense. There are lean and rich correction limits that are user settable.

Bob