Tuning and LTFT (Long Term Fuel Trims)

[michael.konor]

Tuners and others in the know:

Is it common for tuners to turn off the LTFT and why? Fuel mileage? Performance?

 

[BruceH]

It's common during the tuning process. All it takes is turning off adaptive learning. I've left it off before when I had a paxton because of the maf backwash in their standard suck through maf location. The car still ran fine and it didn't learn any bad habits from the poor maf location.

 

[michael.konor]

It's common during the tuning process. All it takes is turning off adaptive learning. I've left it off before when I had a paxton because of the maf backwash in their standard suck through maf location. The car still ran fine and it didn't learn any bad habits from the poor maf location.

Should it be done automatically by tuners? You mention that you left it off before, but not always?

Thanks.

 

[BruceH]

Should it be done automatically by tuners? You mention that you left it off before, but not always?

Thanks.

It's a good idea to do it while dialing in the maf transfer. I've made corrections with it on too. You just have to add the lt and st together to get the correction. The maf adaptive would still have to be turned off though.

I can only speak for myself. I'm sure that pro tuners do things differently than I do. I have forever to figure something out. Their time is money.

Like I said I left it off with my Paxton when it was suck through. The backwash onto the maf made the trims unstable during transitions. When I had it on the trims "learned" bad habits and would have even wider swings because of the ltft.

You probably already know this but I'll say it anyway just in case. Short term trims are instant feedback from the o2 sensor. Long term corrections are predictions that are learned from short term data. As long as the maf transfer function is good the motor can run perfectly fine with stft only.

Why are you concerned with it?

 

[TurboX]

Bruce,
Would you ever consider a thread on tuning ? Im a pretty mechanic hands on type guy but I dont know shit about tuning a modern vehicle. I leave this to the expert(Lito) but I would really enjoy reading about tuning and differences between lets say, NA, SC or Turbo.

 

[BruceH]

Bruce,
Would you ever consider a thread on tuning ? Im a pretty mechanic hands on type guy but I dont know shit about tuning a modern vehicle. I leave this to the expert(Lito) but I would really enjoy reading about tuning and differences between lets say, NA, SC or Turbo.

I don't have the skills or experience to be a ring leader. I'm just a hobbyist with software. I do enjoy sharing my experiences or what I do know and helping when possible but that's about it.

I will say that a very good resource is the book "Advanced Engine Management" by Greg Banish. He covers a lot of internal combustion theory.

Eric Brooks has a tuning section on modularfords you could check out if you haven't already.

 

[one eyed willy]

Just adding to what Bruce said, adaptive learning needs to be turned off during the tuning of the maf transfer process. It will sku what you are trying to accomplish by making corrections on its own. You dial in the MAF transfer with it turned off so you have actual numbers based on the actual transfer, not something the computer is manipulating. Tune your MAF to around 500 and from there set your open loop chart. Also look at what you have your closed loop/open loop throttle position set to. Make sure it's not too high.

Once you get your MAF transfer dialed in, turn the adaptive learning back on. It will help with drive ability depending on how well the transfer is actually dialed in.

 

[michael.konor]

Thanks to everyone for the responses. When I get back, and get the re-tune based on the changes I'm making I'll have him do that.

Mike

 

[Mustangk]

You probably already know this but I'll say it anyway just in case. Short term trims are instant feedback from the o2 sensor. Long term corrections are predictions that are learned from short term data. As long as the maf transfer function is good the motor can run perfectly fine with stft only.

if this is true why does the LTFT seem to add up the STFT, for example: i have stft each bank hovering around 0-2 but once my engine goes closed loop the LTFT climbs up to 20%. indicative of my vacuum leak i think is coming from exhaust bolt hole repair i tapped crooked and leaks oil, a first top manifold hole and i oversized the hole and it broke into valve spring area where theres oil. and leaks at idle.. ???

 

[Juice]

I want my LTFT as close to no correction as possible. I use it as an indicator of how good the tune is.
At first reset, both STFT and LTFT are zero until some miles are driven. At first, LTFT will remain zero, and STFT will have a larger swing. Once LTFT matures, the pcm 'learned' the difference between what the engine wants vs what the calibration is set at. At this point, STFT swings will be much less as the pcm is applying the learned (LTFT) corrections.
Turning off adaptive is done to dial in an aftermarket intake where tube diameter at the maf has changed. After that is done, I turn adaptive back on and leave it on.
The more changes, (injectors, maf, cams, stroker, FI) the more difficult the tuning process.

 

[jamiewellman]

My tune guy says to leave long term fuel trims off because the car can learn bad habits,my mechanic says it needs to be on for driveability,I've got a 2007 mustang gt..vortech supercharger long tube headers Ford racing intake throttle body cams forged internals who right who's wrong

 

[Juice]

They are both somewhat right. But, the only way the pcm can learn "bad" LTFTs is if the tune is not right, in more than one aspect. Also, with LTFTs disabled, not all monitors will complete and you fail smog test.

This has been an issue since the late 80s when we started tuning the fox body cars. Ford applies LTFT at WOT, and this is the issue. Could lean out WOT, and there goes yout engine.

There is no reason to disable LTFTs. On the fox platform, you just fix the adaptive learning table so at WOT it does not apply fuel trims learend at part throttle. There has to be an equivalent table in the Spanish Oak pcm.

Remember, it takes a lot of time to perfect a highly modified combo. Tuners tune to make money, they dont want to wreck your engine. Disabling LTFTs is a shortcut to a safer tune.

You may want to find another tuner. Like Lito.

 

[jamiewellman]

How do I contact lito ? can I call them or do I have to email them

 

[Juice]

By email. His contact is around here in several threads. Sorry, I dont have it handy. Someone will post it Im sure.

 

[Juice]

manuel at tudyno dot com.

 

[jamiewellman]

This Manuel guy don't know his ass from a hole in the ground., I've been emailing this crackhead for two days give him all the information he needs and he want call you..but he emailed me back he can't help me because I hadn't give him proper information he said...I told him my mods built motor so forth so on sent pictures..I think this dude does like cold air intakes and simple mods I'm out of his league

 

[FredB66]

You have no idea what you're talking about. Manuel (Lito) is literally one of the best 3V tuners on the planet. He operates out of Venezuela and therefore does his business via email. If you give him what he asks for he will work with you and at a VERY reasonable price. Sometimes it takes a few days, but its worth it.

 

[jamiewellman]

I know exactly what I'm talking about I give him all the Pacific's on my motor and he can't help me..

 

[Flapjack]

This Manuel guy don't know his ass from a hole in the ground., I've been emailing this crackhead for two days give him all the information he needs and he want call you..but he emailed me back he can't help me because I hadn't give him proper information he said...I told him my mods built motor so forth so on sent pictures..I think this dude does like cold air intakes and simple mods I'm out of his league

You won't get anywhere in this forum dissing Lito. To second what Fred said, Lito is one of the best 3v tuners out there... period. My combo was an absolute monster that NO ONE could tune. I was running my own tune using the old Predator system and the car was barely driveable. Lito wrote both gas and E85 tunes for my setup (5.4L 3v w/twin turbos) with custom heads/turbo cams, custom exhaust, custom turbo headers, no VCT, and 50 million other nit-noid things that I can't remember... at an altitude of 7300ft. My car made 1018 rwhp on E85.

I would go back and re-read your email chain and see what he asked for vs what you gave him. I'm guessing you missed something, but if it was Lito that missed something, a little kindness goes a long way. He tunes many of the hardest-to-tune cars out there for WAY less than what most "tooners" ask. He is a good guy who does what he does for love of the platform, not for $$$.

 

[jamiewellman]

I gave him everything he ask for and just give him all the information again even sent all the information about my supercharger..and I'm not on here to be popular if he can't tune my car he's not the best in the world mines should be around 750,+ hp