What to look for in Data logging MAF Transfer Rate

[davedyno]

Question, I have a U7146 and a 01 GT. When data logging what do I look for to make sure the MAF Transfer Function rate is working right. The reason I ask is when race at a track that is 600' higher in elevation I lose about .25 tenths in ET. ,at the sea level track I get my best ET's. I did data log A/F readings with a Wideband Meter and I was running a little lean at 13.4 at WOT. I was told by a "Tuner" that this was a MAF transfer function problem. Another tuner told me the higher the Elevation the slower I will run even correcting A/F WOT reading. Should the MAF correct for this or not.
Car runs great, Predator does a great job also. I might just stay at the sea level track.
Dave

[concoursd]

You need to look at your LTFT's. They are your long term fuel trims that are gathered from the o2 sensor feedback as you drive PART throttle. This will give you feedback as to how many % off the MAF function is. You can then go in and globally adjust it. I recommend that you adjust it about 2% at a time and then go back out and datalog again. It is obvious that your car will run better at sea level where the air is more dense and therefore more powerful. That is also why you are run a little leaner. it really depends on how much you drove in high altitude. The long term fuel trims are aggregate values gathered as drive for about 20-30 miles at normal operating temps at highway speeds. So if the computer had not adjusted its fuel tables enough yet for the less dense high altitude air, then you would register lean at WOT where the computer defaults to a base fuel map and no longer considers o2 sensor feedback.

[davedyno]

I believe you are correct. Living in Md you have the best of both worlds the Ocean and Mountains just hours away. I live close to sea level area and race most of time at a sea level track, but about twice a year I go to a track near Western part of State with the higher elevation, is only about a hour Drive on the interstate away from where I live. When I do arrive at the track driving time in distance is very short,it would take a lot of quarter mile runs for the computer to adjust its fuel tables.
Thanks for Great Answer
Dave

[concoursd]

In theory, the computer should adjust to the change in barometric pressure but really datalogging your LTFT's will give you a better idea if the computer is adjusting properly or not or if there is something you can do tune wise to optimize everything.

[davedyno]

In theory, the computer should adjust to the change in barometric pressure but really datalogging your LTFT's will give you a better idea if the computer is adjusting properly or not or if there is something you can do tune wise to optimize everything.

Question, When datalogging LTFT'S the values show zero,this was a short drive. Do I need to take a long drive 30 min. or so before I start to see any readings on the Predator and once I have some data what do I look for to see if MAF transfer rate is working properly.
Thanks
Dave

[concoursd]

the LTFT's are a long term average so it is best to have a minimum 20 minute drive when the vehicle is warmed up and entered into closed loop (not cold start mode). Keep speeds at about 60-70 mph. Use cruise if possible. The issue you have is that you should think about doing this in the high altitude environment you are in. Pulling up a large grade with cruise will be too much load on the motor and will not keep you in the part throttle mapping of the computer to yield any useful LTFT results.

[Shaken]

Question, I have a U7146 and a 01 GT. When data logging what do I look for to make sure the MAF Transfer Function rate is working right. The reason I ask is when race at a track that is 600' higher in elevation I lose about .25 tenths in ET. ,at the sea level track I get my best ET's. I did data log A/F readings with a Wideband Meter and I was running a little lean at 13.4 at WOT. I was told by a "Tuner" that this was a MAF transfer function problem. Another tuner told me the higher the Elevation the slower I will run even correcting A/F WOT reading. Should the MAF correct for this or not.
Car runs great, Predator does a great job also. I might just stay at the sea level track.
Dave

Naturally aspirated cars will make more power at lower elevations the air is denser. Have you checked you 60' times? 13.4 seems really lean my stang likes 12.8 -13.0 the canned tune with out adjustment runs between 12.2 -12.5 on my car. Reading many posts from sponsered tuners on Mach1registry.com and on this site 12.8 seems to be the magic number.

[concoursd]

i agree that you were running lean but if you have faulty sensors or testing procedures then it is garbage in garbage out.

How old is your wideband sensor? Is it functioning properly? do you run race gas often? does your street gas have ethanol in it (all california gas oxygenated and has 10% ethanol? oxygenated fuels with ethanol will show leaner readings? race gas damages wideband sensors. wideband sensors also degrade over time.

[davedyno]

the LTFT's are a long term average so it is best to have a minimum 20 minute drive when the vehicle is warmed up and entered into closed loop (not cold start mode). Keep speeds at about 60-70 mph. Use cruise if possible. The issue you have is that you should think about doing this in the high altitude environment you are in. Pulling up a large grade with cruise will be too much load on the motor and will not keep you in the part throttle mapping of the computer to yield any useful LTFT results.

While trying to datalog I came across a problem. After driving car for almost a hour Predator will not data log LTFT's using the Performance Tune, yes the Predator does say I'm in closed loop. No codes , at first I thought EGR Vacuum regulator was not working right causing a problem, it check out Ok. Next I reinstalled the original factory tune and now Predator will datalog the LTFT's. So today I put the Performance tune back in again, still Predator not datalog the LTFT's when using Performance Tune.
Dave

[davedyno]

Question, I have a U7146 and a 01 GT. When data logging what do I look for to make sure the MAF Transfer Function rate is working right. The reason I ask is when race at a track that is 600' higher in elevation I lose about .25 tenths in ET. ,at the sea level track I get my best ET's. I did data log A/F readings with a Wideband Meter and I was running a little lean at 13.4 at WOT. I was told by a "Tuner" that this was a MAF transfer function problem. Another tuner told me the higher the Elevation the slower I will run even correcting A/F WOT reading. Should the MAF correct for this or not.
Car runs great, Predator does a great job also. I might just stay at the sea level track.
Dave

Naturally aspirated cars will make more power at lower elevations the air is denser. Have you checked you 60' times? 13.4 seems really lean my stang likes 12.8 -13.0 the canned tune with out adjustment runs between 12.2 -12.5 on my car. Reading many posts from sponsered tuners on Mach1registry.com and on this site 12.8 seems to be the magic number.[/quote
60' times that day at the higher Elevation was 2.02. 60' at sea level just about the same, but every now then I will dip into the 1.9's . At sea level I alway's have WOT fuel adjusted to achieve a 12.8 ,with same settings on Predator at higher elevation was the 13.4. I could have dial A/F in to 12.8, but ran out of time that day to make any more runs.
Thanks
Dave

[davedyno]

i agree that you were running lean but if you have faulty sensors or testing procedures then it is garbage in garbage out.

How old is your wideband sensor? Is it functioning properly? do you run race gas often? does your street gas have ethanol in it (all california gas oxygenated and has 10% ethanol? oxygenated fuels with ethanol will show leaner readings? race gas damages wideband sensors. wideband sensors also degrade over time.

My FAST Wideband is about a 1 1/2 years old. But most time it's in the box with Sensor removed. I never ran or will use race gas. Maryland only uses oxgenated gas in the winter months, I only race in the summer. I know all 87 gas in MD has 10% ethanol not sure about the 93 HighTest in MD. Performance wise I'm very pleased with my GT Mustang with just a few bolts on's, I sure I can do even better, It's all in the timing and A/F setting.
Thanks
Dave

[concoursd]

I keep mulling your post over and keep confirming that there is probably nothing wrong with the tune. Your 60' times look ok. The car makes consistent LTFT's with the factory tune used at sea level. That confirms that the MAF transfer curve is accurate and the MAF is working properly. If you had a bad transfer curve or even a bad sensor, then you would have some significant LTFT's. The Diablo tunes would not touch the MAF curve.

It seems given the above, the scenario is as follows: You have a mass air sensor that measures thinner air at high elevation and therefore drives the fuel injectors less. Remember, at WOT the o2 sensors are not used for feedback. Such feedback in the form of LTFT's would be used by the computer to add a correction factor to the fuel commands at part throttle and WOT. The o2 sensors are also going to be reading less oxygen content in the exhaust as the thinner air in high elevation relates to having less oxygen density in the air which makes retuning of non-efi vehicles necessary and another reason why there are olympic training centers are located in Colorado at 6000 foot elevation (less oxygen content in every breath increases muscle stamina at sea level competition).

I would like to see your LTFT's in the high altitude area where you have this lean condition indicated on the wideband sensor. I understand that there is an issue with your tool logging the LTFT's with a diablo tune installed. I am not sure why that is, I would need Mike L to chime in on that. But it shouldnt matter really. You have already confirmed that the WOT fuel maps work fine for your car at sea level. And you can confirm with the stock file datalogs if the MAF is working properly with a good transfer function.

I am still wondering if maybe there were not enough miles on the car in the high altitude to build a proper fuel trim from the o2 sensors to compensate for the lean nature. The barometric pressure tables in the computer should also be adding a correction factor for the altitude change. I dont believe Diablo tunes modify those tables but that would be something that Mike L would have to let you know about. You may also want to log the BAP sensor at sea level and high altitude.

[davedyno]

Concoursd...Thanks again for your feed back, yes I don't think I have problem with my Tune or LTFT's. Car runs just to good with the few mods I done to it. I would like to be able to log the LTFT's values to see what they look like and learn more about this area. The Predator is a great tool, it beats changing carb jets and getting the old timing light out. By the way just curious by any chance due you ride a Kawasaki Concours.
Dave
01 Gt Vert
92 Concours COG 1191

[Shaken]

So you MPH must have dropped to loose the 2 tenths probably from the lean A/F you where running. Yeah and the wideband data is nice too. No more burned hands from having to check your plugs for proper jetting.

[davedyno]

So you MPH must have dropped to loose the 2 tenths probably from the lean A/F you where running. Yeah and the wideband data is nice too. No more burned hands from having to check your plugs for proper jetting.

Yes, MPH did drop also. The wideband is a nity tool to have. A lot of things have changed over the years with tuning. Sounds like you burned your hands a few times also. Thanks for your feedback too, this how you learn how the computer & sensors work. It's just not as simple as changing jets anymore.
Dave