Most Efficient way to tune with a loaded chassis dyno WB? STFT? LTFT?

[Midnite Magic]

I have accesses to a Mustang chassis dyno and I was wondering what the most efficient way to tune the MAF & VE tables? I have done it using a NGK AFX wideband with the OL set to 13.5:1 AFR, but it seems when I have all the cells close to or under 1% and then check it in CL the LTFT are around 7-10%. Would I be better off using the LTFT or STFT to dial in the tables if I am going to enable CL once the tune is finished? On a really good tune or OEM tune what do the fuel trims look like min to max on a daily basis?

[a.graham52]

I can answer that on own, 4 or less long term is preferred. But that's all I can tell ya

[5FDP]

Sadly no one knows what car you drive nor the mods (if any) that are done to it.

Post a "tune" files up and I'm sure someone could help you more.

[Midnite Magic]

2000 Firebird, Futral F14 camshaft, SLP headers, & bolt ons. Also upgraded to a 2002 OS

[Ben Charles]

You can use STFT's for part throttle and what not, but if your on the dyno, Just plot AFR against the WB and it would be the same as doing it with STFT's (disable LTFT's, much easier to tune), but you can easily do WOT as well.

[Midnite Magic]

You can use STFT's for part throttle and what not, but if your on the dyno, Just plot AFR against the WB and it would be the same as doing it with STFT's (disable LTFT's, much easier to tune), but you can easily do WOT as well.

Just trying to figure out what I am missing here then. I can command say 13.5:1 in OL and tune with the AFX WB to that target. I can get very close like less than 1% usually. However when I set everything back to CL and check the tune the LTFT are high. Not sure what I am missing

[Ben Charles]

Reset the Fuel trims or turn them off. With fuel trims they are going to shoot for around 14.7 so you will never be able to get 13.5 with CL enabled, you would have to leave it in OL to get that AFR. LTFT's are high b/c its adding fuel to get the AFR around 14.7 (probably off about 10 percent or fuel trims ADDING 10 percent)

[wyochimneysweep]

why you shoting for 13.5?

[Midnite Magic]

Reset the Fuel trims or turn them off. With fuel trims they are going to shoot for around 14.7 so you will never be able to get 13.5 with CL enabled, you would have to leave it in OL to get that AFR. LTFT's are high b/c its adding fuel to get the AFR around 14.7 (probably off about 10 percent or fuel trims ADDING 10 percent)

Ben I am not saying that I leave the table at 13.5:1. I just do that on the dyno because of the load and I turn the PE off completely. Only the VE or MAF is dialed in I set the OL table back to 1.00 and the CL should then be 14.68 (14.7:1) but the fuel trims are off. It was my understanding that you can turn to whatever target AFR you want in OL. I know most people suggest around 13.0 for boosted cars but once the everything is dialed in they got back to CL Stoich with PE enabled

[Ben Charles]

13.0 for a boost app??? I don't run that lean naturally aspirated

[Midnite Magic]

13.0 for a boost app??? I don't run that lean naturally aspirated

NOT for WOT, just for dialing in the VE and MAF tables instead of 14.68

[wyochimneysweep]

why? my understanding is tune ve and maf to 14.68 then when you go closed loop it will be trimming right and then your pe and be will be correct also. if you tune to 13 ve then your always rich and if you set pe to .82 then you'll be even richer

NOT for WOT, just for dialing in the VE and MAF tables instead of 14.68

[06GMC5.3L]

why? my understanding is tune ve and maf to 14.68 then when you go closed loop it will be trimming right and then your pe and be will be correct also. if you tune to 13 ve then your always rich and if you set pe to .82 then you'll be even richer

This

Wouldn't you want to tune your VE and MAF to stoich for your fuel, with PE commanded to 1.27 (14.68/11.5 or so) for turbo applications. Then it was my understanding as well that your trims should be correct after. I also thought that once your VE and MAF were dialed in, you could disable LTFTs and the STFTs would be enough to keep the trims in line. I know of a bunch of people who disable LTFTs after tuning, and run only CL STFTs.

Please correct me if I am wrong.

[Midnite Magic]

why? my understanding is tune ve and maf to 14.68 then when you go closed loop it will be trimming right and then your pe and be will be correct also. if you tune to 13 ve then your always rich and if you set pe to .82 then you'll be even richer

Not sure you understand how the MAF, VE and OL Fuel Table works.

This

Wouldn't you want to tune your VE and MAF to stoich for your fuel, with PE commanded to 1.27 (14.68/11.5 or so) for turbo applications. Then it was my understanding as well that your trims should be correct after. I also thought that once your VE and MAF were dialed in, you could disable LTFTs and the STFTs would be enough to keep the trims in line. I know of a bunch of people who disable LTFTs after tuning, and run only CL STFTs.

Please correct me if I am wrong.

If you tune your MAF & VE in open loop with a wideband the OL Fuel table is your target. If you set the whole table to 1.000 and your Stoich value is 14.63 then your tuning target is that 14.63. If you set the OL fuel table to 1.125 then your target will be 13.0. You can tune the VE & MAF to this value and when you return the OL fuel table to 1.000 your fueling will return to 14.63

[06GMC5.3L]

If you tune your MAF & VE in open loop with a wideband the OL Fuel table is your target. If you set the whole table to 1.000 and your Stoich value is 14.63 then your tuning target is that 14.63. If you set the OL fuel table to 1.125 then your target will be 13.0. You can tune the VE & MAF to this value and when you return the OL fuel table to 1.000 your fueling will return to 14.63

Agreed, but why would you want to tune your VE and MAF to an AFR that you won't be running in CL? Also, did you give enough time for your LTFTs to settle? If your LTFTs are still off after you dial in the VE and MAF, it is my understanding that something went wrong during the VE and MAF calibration. Also, why are you disabling PE, wouldn't you want to tune the entire VE and MAF tables, not just up to 4000 RPM or whatever? 13:1 seems way too lean for a boost application. Everything I have read targets for around 11.5-11.8 or so for a safe AFR while in boost. 13 seems to be asking for trouble as far as I am concerned. 13 might be good and safe for cruising/no boost/low boost. I have read a lot of guys run stoich in cruise as well, then dont start to richen out till the boost hits, looking for 11.5-11.8 around peak torque/hp.

Again, anyone please feel free to correct me if anything I say is wrong.

[Ben Charles]

Ive ran boost setups at VERY light loads (crusing) around 15.5 for fuel economy and just enrich the mixure when in boost (goes off a different portion of the VE or MAF tables). No need to run 13.1 driving around IMO.

[silverbullet08]

I run the majority of my boosted applications at 14.7 cruising and set up PE early with a gradual blend from 14 to 11.7 based on how the setup makes boost. This usually gives a smoother VE table from what I have noticed. Never had a issue with running stoich on any boosted app unless its a high compression big cam engine which tend to have their own liking.

I do not see the reason for tuning it at a 13 then switching back to stoich though... That's probably where your getting the issue. On paper it should work like your saying but is just throwing another multiplier in the equation that doesn't need to be there.

[wyochimneysweep]

what fuel you using that is stioch at 13 afr?

[Midnite Magic]

Why do you keep talking about any form of Forced Induction?? I never said anything about boost

[Red01Z]

Ben I am not saying that I leave the table at 13.5:1. I just do that on the dyno because of the load and I turn the PE off completely. Only the VE or MAF is dialed in I set the OL table back to 1.00 and the CL should then be 14.68 (14.7:1) but the fuel trims are off. It was my understanding that you can turn to whatever target AFR you want in OL. I know most people suggest around 13.0 for boosted cars but once the everything is dialed in they got back to CL Stoich with PE enabled

Why do you keep talking about any form of Forced Induction?? I never said anything about boost

Never said anything, huh? It sounds like your comment was interpreted pretty literally.