Switch To Include AFRtarget

[Scottie-GNZ]

For as long as I have used and tuned MS, I always used don't include AFRtarget. The engine is tuned fairly well, but constant VE table tweaking is getting tiring. From everything I have read, it appears Include AFRtarget simplifies tuning. So, my question is, what does it take to make the switch without having to do a complete retune? The engine is a turbocharged V8 running E85. The car is street-driven but is not a DD. It is mainly driven to the drag strip, so a finite street tune is not a high priority but I still want decent startup, idle and driveability. The priority is the most accurate tune under boost.

BTW, I will be firing up the engine in about 10 days with fresh bearings and rings and need to be sure I don't run it overly rich on the initial startup. Can I safely make the switch prior to startup or should I do it after?

TIA,

[Yves]

When I made the switch I had to retune.

[Scottie-GNZ]

Thanks for the reply.

Is there any documented procedure for making the switch or is it as simple as just changing the parameter? Does the VE table or anything else need to be changed before using it for the 1st time? Is the extent of the retune just tweaking the VE values? I am asking these questions because I would like to avoid any overly rich conditions with the fresh rebuild.

[Matt Cramer]

What "Include AFR Target" does is it takes each VE cell, multiplies it by what you have set for the AFR, then divides it by the AFR target at that RPM / load combination.

So to change a VE table from one that does not have that setting checked to one that does, you do the procedure in reverse: Take the VE number, multiply it by the AFR target, and divide it by the set AFR.

[Scottie-GNZ]

What "Include AFR Target" does is it takes each VE cell, multiplies it by what you have set for the AFR, then divides it by the AFR target at that RPM / load combination.

So to change a VE table from one that does not have that setting checked to one that does, you do the procedure in reverse: Take the VE number, multiply it by the AFR target, and divide it by the set AFR.

Matt,

thanks for putting it in layman's terms. That really cleared it up for me, but I do have a couple of questions:

1. By "set AFR", are you referring to the Stoichiometric AFR Value in General Settings? In my case that would be 9.8:1.
2. I might be misunderstanding what I have read, but the advice seems to be to set the VE table and adjust the AFR as needed. That doesn't make sense to me if the values in my target AFR table are what I desire. Am I missing something?
3. On the same note, does EGO Correction and VEAL work the same, i.e., changing VE values to match target AFR?

[Matt Cramer]

thanks for putting it in layman's terms. That really cleared it up for me, but I do have a couple of questions:

1. By "set AFR", are you referring to the Stoichiometric AFR Value in General Settings? In my case that would be 9.8:1.

Correct.

2. I might be misunderstanding what I have read, but the advice seems to be to set the VE table and adjust the AFR as needed. That doesn't make sense to me if the values in my target AFR table are what I desire. Am I missing something?

In this case, you would first set the VE table to hit your AFR targets, then adjust the AFR targets to whatever AFR gives you best power. The advice you've picked up seems to be backwards.

3. On the same note, does EGO Correction and VEAL work the same, i.e., changing VE values to match target AFR?

Yes. They're unchanged.

[racingmini_mtl]

... the Stoichiometric AFR Value in General Settings? In my case that would be 9.8:1...

Have you calibrated your wideband O2 sensor(s) to that stoic value? If you haven't, you will have a completely wrong AFR because all wideband sensors come calibrated by default to have 1.0 Lambda correspond to 14.7 AFR. And the sensors read Lambda regardless of the fuel used; AFR is just an artificially computed value.

Jean

[Rick Finsta]

So how exactly does this make tuning easier?

I can't use it as I run E85 but display/tune to gas AFRs just because it is familiar territory and makes for easier comparison with other tuners, but I've never understood the advantage it conveys.

[pit_celica]

The only advantage is that you can change the fueling tune by changing only the AFR target table when you want a different AFR target.

If you use "Don't include AFR target", to do the same thing (attain a different AFR target after the VE table is fully tuned), you will need to change the VE table (where you want a different AFR) and you will also need to change the AFR target so that your EGO correction is correctly applied.

If you are sure that your AFR target is what you desire and you do not plan to change it anytime soon, then this feature can't do anything to you.

Sam

[Scottie-GNZ]

So how exactly does this make tuning easier?

I can't use it as I run E85 but display/tune to gas AFRs just because it is familiar territory and makes for easier comparison with other tuners, but I've never understood the advantage it conveys.

This is exactly my situation. I tried using Lambda and willing to admit I did something wrong, but my VE table got royally screwed up. Have stuck to the gas scale and have no issues with it making a substantial amount of hp.

If you are sure that your AFR target is what you desire and you do not plan to change it anytime soon, then this feature can't do anything to you.

Bingo! I started to confuse myself looking for an answer.

Making a 1/4-mile pass, datalogging and letting MLV suggest the VE changes has worked well for me. Not sure if I am brave enough yet to rely on VEAL for autotuning during a pass. Any thoughts on this?

[racingmini_mtl]

... the Stoichiometric AFR Value in General Settings? In my case that would be 9.8:1...

... Have stuck to the gas scale ...

Those two statements contradict each other. You either use the gas scale with a 14.7 stoic setting OR you use 9.8 and set everything (AFR targets, WBO2 calibration) according to that.

Jean

[nathaninwa]

I've tuned a LS turbo sandrail using veal and darn near nailed our targets up to 14psi, my 1j buddy had soley used veal to tune his gas and ethanol tunes, and I tuned my ve table to 28psi manually, then fattened the tune up a half point afr and tried autotune, with in 4 pulls on the dyno the afr's were back in target

Initially I'll roll in and let veal tune the low revs till I can see a trend, scale the remainder of the table and let veal finish it off. Comes in handy in the spool up section where cell weighting is hard to dial in manually

[EspeNS]

Making a 1/4-mile pass, datalogging and letting MLV suggest the VE changes has worked well for me. Not sure if I am brave enough yet to rely on VEAL for autotuning during a pass. Any thoughts on this?

I have used VEAL on a rallycross car during a heat. It worked just fine. But we used it just first 2-3 heats to get a basic shape to the VE map. Most of the tuning was done the way you describe.
I consider logging and tuning with help from MLV safer in this type of tuning, when you really need all your attention at driving. Safer both for the driving and the tuning.

Espen

[Rick Finsta]

Jean I think he is saying he uses 9.8 for the req_fuel calculation and then uses 14.7 for everything else. This is exactly how I do it so my req_fuel is calculated based off my fuel's actual stoich but I can read everything in gas scale. I would think this is how the majority of E85 users run for the reasons we've stated.

[racingmini_mtl]

Jean I think he is saying he uses 9.8 for the req_fuel calculation and then uses 14.7 for everything else. This is exactly how I do it so my req_fuel is calculated based off my fuel's actual stoich but I can read everything in gas scale. I would think this is how the majority of E85 users run for the reasons we've stated.

If that's what is meant then yes, that is the correct way to go. But there is a setting in the general settings for setting the stoic value which is used in the fueling computations and that needs to be consistent with the rest of the settings/calibration.

Jean

[Scottie-GNZ]

As Rick clarified, the 9.8 generates the Req_Fuel value and the VE table is built for that Req_Fuel. If the Stoich value was 14.7, a different Req_Fuel value would have been generated and the VE table would have different values for that Req_Fuel. As far as I can see, the end result would be the same. Maybe I am doing this all wrong, but whatever fuel calculations are being done with my values is working for me. I am making 900hp with more on tap and hitting my AFR targets.

EspeNS and nathaninwa, thanks for your feedback on you experience with VEAL. nathaninwa, I like your approach.

[racingmini_mtl]

As I said, using 9.8 for your req_fuel computations is fine and what you need to do. However, if you have set the stoic value on the general settings to 9.8 then you will have a problem if you want to switch to "Include AFRtarget" unless you also change your targets and your wbo2 calibration. If not, you will always have an artificial factor of 14.7/9.8 in your fueling computations; this can be compensated for by a different VE table but it should not be needed if you set things correctly and coherently.

Jean

[BigLou240sx]

See the following thread for a discussion on how to get a from a tuned VE table without incorporating AFR to a rough VE with incorporating AFR.

http://www.msextra.com/forums/viewtopic ... 34&t=55583

I haven't personally tried the things we were talking about yet, but it should work assuming you tuned your VE table to what your AFR table is reporting.

[Kev5.0]

As I said, using 9.8 for your req_fuel computations is fine and what you need to do. However, if you have set the stoic value on the general settings to 9.8 then you will have a problem if you want to switch to "Include AFRtarget" unless you also change your targets and your wbo2 calibration. If not, you will always have an artificial factor of 14.7/9.8 in your fueling computations; this can be compensated for by a different VE table but it should not be needed if you set things correctly and coherently.

Jean

I think I may have done this by mistake. Just to clarify. I have my req_fuel calculated from 9.9 for E75 (75% Ethanol) and I also have my Stoich value set as 9.9 also. I however, have AFR Table values that reflect gasoline.

So what can I do to effectively correct this without having to re-tune the entire tables?

What problems would this artificial factor cause? I notice if I estimate what to scale or change my VE table based on target AFR and actual AFR it is never right. Ex. target is 11.5 and actual is 11.0, 11.0 / 11.5 = 0.957. Is this the cause?

Thanks,
Kevin