MSCAI as SRI = LTFT better

[Trader]

I have been having high LTFT since I installed the MSCAI with air straighteners so yesterday I switched the CAI into a SRI. I had a theory that the fuel trims were off due to the bend in the pipe just before the MAF causing turbulance and not letting the MAF read the air accurately. Well it seems to have helped a lot.


LTFT with MSCAI as CAI
idle = 5-6%
tip in = 10 %
Light throttle = 7%
WOT = 9 %

LTFT with MSCAI as SRI
Idle = 0%
tip in = 2%
light throttle = 6%
WOT = 3.5%

AFR on my logs are smoother as well.

 

[bykeryder4life]

nice info, I may switch mine over to SRI as well. log your boosted temps between the two and get a comparison....

 

[Trader]

nice info, I may switch mine over to SRI as well. log your boosted temps between the two and get a comparison....

Will do. It was 65 degrees here today and I was sitting in traffic here in Center City philly. Temps are definately higher with the SRI over the CAI. I would rather have my LTFT stable though. Going to get the TMIC when it gets hotter anyways.

 

[eg6motion]

I have been having high LTFT since I installed the MSCAI with air straighteners so yesterday I switched the CAI into a SRI. I had a theory that the fuel trims were off due to the bend in the pipe just before the MAF causing turbulance and not letting the MAF read the air accurately. Well it seems to have helped a lot.


LTFT with MSCAI as CAI
idle = 5-6%
tip in = 10 %
Light throttle = 7%
WOT = 9 %

LTFT with MSCAI as SRI
Idle = 0%
tip in = 2%
light throttle = 6%
WOT = 3.5%

AFR on my logs are smoother as well.

looks like your LTFT is simply compensating for the extra air from the CAI... seems normal...and makes sense.

 

[matsuda]

looks like your LTFT is simply compensating for the extra air from the CAI... seems normal...and makes sense.

Extra air???

The changes in the long term fuel trims (closer to zero) simply indicate that incoming air is being metered more accurately.

 

[eg6motion]

Extra air???

The changes in the long term fuel trims (closer to zero) simply indicate that incoming air is being metered more accurately.

no it doesn't, Long Term Fuel Trim is a measure of the adjustment your ECU is making to keep your Air/Fuel ratio at a set number. I am not sure what the mazda LTFT range is, probably around +/-10%, but when you add mods, like an intake, you are increasing the available air into your engine, changing the AFR. This will then cause the ECU to adjust your LTFT for the difference. In this case, he's measuring a higher LTFT for the CAI, meaning his AFR is farther off than as a SRI, indicating more air-to-fuel.

 

[mazdaspeed32007]

my ltft with the ms intake as a cai was 15-20 at idle, 10-20 at medium throttle and 7% at WOT.

I ran mine as a sri and added the straightener and now im at 7-10 at idle, 7-4 medium throttle, and about the same at WOT/little less.

why would my % be totally opposite from his. higher at idle and lower at WOT? but his is lower at idle and higher at WOT?

when i reflash the ecu they obviously go back to a value of 0 but then as time goes by they creap back to their correction. ill check again today on my way home and post again tomorrow morning but last time i checked my ltft's were completely opposite his....

 

[eg6motion]

my ltft with the ms intake as a cai was 15-20 at idle, 10-20 at medium throttle and 7% at WOT.

I ran mine as a sri and added the straightener and now im at 7-10 at idle, 7-4 medium throttle, and about the same at WOT/little less.

why would my % be totally opposite from his. higher at idle and lower at WOT? but his is lower at idle and higher at WOT?

when i reflash the ecu they obviously go back to a value of 0 but then as time goes by they creap back to their correction. ill check again today on my way home and post again tomorrow morning but last time i checked my ltft's were completely opposite his....

location maybe? Elevation can play a major roll as well... I know my trims would be drastically different in CO than someone in California or AZ with the same mods...

 

[Trader]

no it doesn't, Long Term Fuel Trim is a measure of the adjustment your ECU is making to keep your Air/Fuel ratio at a set number. I am not sure what the mazda LTFT range is, probably around +/-10%, but when you add mods, like an intake, you are increasing the available air into your engine, changing the AFR. This will then cause the ECU to adjust your LTFT for the difference. In this case, he's measuring a higher LTFT for the CAI, meaning his AFR is farther off than as a SRI, indicating more air-to-fuel.

In closed loop the ecu "trims" what is being read from the MAF sensor via feedback from your O2 sensor. Not the other way around. So if you are running more air from an intake/exhaust or whatever the MAF sensor will pick up more air going thru the pipe. The ecu will take this value and "check" how close the readings from the MAF are to stoich via the O2 sensor. If it is off from its intial MAF reading, it will then make short term adjustments by STFT. Eventually your LTFT will be an avge of your STFT.

So your LTFT should not be higher as a function of just flowing more air. Your LTFT are just the adjustments the car makes to its own readings. The higher the numbers the less accurate the readings were initally made by the MAF.

 

[mazdaspeed32007]

ok so new ltft's with my reflash. 7 at idle, 2 at mid throttle, 6 at WOT.

 

[tru-boost]

You can get the ms cai to have very good fuel trims you just need to know how. You can change the clock position of the tube the MAF sits in or the pipe closer to the filter. You can also loosen the screws that hold the sensor in the tube and slightly twist the sensor to a different angle. It all has to do with how the air hits the sensor. You do also realize i hope that fuel trims dont mean a damn thing ! It simply shows that your ecu recognizes there is a difference in the way the maf is reading your airflow and is compensating to fix it. Your LTFT can be off by 10000% and it wouldnt mean s***. The car would still run fine because that what fuel trims are designed to do. My car made 300hp and did multiple 12 second 12 mile passes with LTFT's in the 30%. Afterremoving the cai to install an inlet pipe my trims are damn near zero now, but i dont care either way. Just some info for those who think LTFT has ANY effect on the way your car drives..... It doesnt !!

 

[matsuda]

no it doesn't, Long Term Fuel Trim is a measure of the adjustment your ECU is making to keep your Air/Fuel ratio at a set number. I am not sure what the mazda LTFT range is, probably around +/-10%, but when you add mods, like an intake, you are increasing the available air into your engine, changing the AFR. This will then cause the ECU to adjust your LTFT for the difference. In this case, he's measuring a higher LTFT for the CAI, meaning his AFR is farther off than as a SRI, indicating more air-to-fuel.

No, not close.

As long as the air is being metered properly, changing the amount of air will not change the fuel trims.

If you were to rotate the MAF sensor slightly while the engine is running, the fuel trim would change significantly. It is the metering of the air (and not the amount of air) that is being changed.

Why do you think that an air straightener can have such a large effect on fuel trims?

 

[Trader]

You can get the ms cai to have very good fuel trims you just need to know how. You can change the clock position of the tube the MAF sits in or the pipe closer to the filter. You can also loosen the screws that hold the sensor in the tube and slightly twist the sensor to a different angle. It all has to do with how the air hits the sensor. You do also realize i hope that fuel trims dont mean a damn thing ! It simply shows that your ecu recognizes there is a difference in the way the maf is reading your airflow and is compensating to fix it. Your LTFT can be off by 10000% and it wouldnt mean s***. The car would still run fine because that what fuel trims are designed to do. My car made 300hp and did multiple 12 second 12 mile passes with LTFT's in the 30%. Afterremoving the cai to install an inlet pipe my trims are damn near zero now, but i dont care either way. Just some info for those who think LTFT has ANY effect on the way your car drives..... It doesnt !!

I think you are right as long as the correction needed is linear with the amount of flow. So I agree except in two circumstances.

1. The STFT's can be less stable if there is more turbulance. So if your STFT are ranging between +5 and +15 eventually you will average +10 and your LTFT will be set at +10. Like wise your STFT could range between +8 and +12 (more stable) and still end up with at LTFT of +10. Because when you have turbulance due to a bend the amount of air being disturbed is not linear with the amount of flow. Meaning you can need more correction sometimes than others. This means crap when in closed loop because the ecu is adjusting but when you are WOT the ecu can not self adjust therefore you will see more volitile AFR.

I can demonstrate this with two of my Dash hawk logs

MSCAI as CAI
with this set up I saw my STFT more volitile, and you can see the AFR is not very stable here at WOT:

MSCAI as SRI
My STFT are more stable with this set up... as you can see the AFR is much more stable.

2. If the ecu is always self correcting via means of STFT the LTFT at WOT may not be very accurate representation of the needed correction. And may be set too low or too high. This kind of dovetails with the first reason. The LTFT at medium throttle is a summation of the STFT at medium throttle, but the ecu also uses these LTFT at WOT where there is more flow. So if the amount of correction needed is not linear with the amount of flow, then the LTFT could be to low or too high at WOT therfore running more lean or rich.

 

[Wurf]

I think you are right as long as the correction needed is linear with the amount of flow. So I agree except in two circumstances.

1. The STFT's can be less stable if there is more turbulance. So if your STFT are ranging between +5 and +15 eventually you will average +10 and your LTFT will be set at +10. Like wise your STFT could range between +8 and +12 (more stable) and still end up with at LTFT of +10. Because when you have turbulance due to a bend the amount of air being disturbed is not linear with the amount of flow. Meaning you can need more correction sometimes than others. This means crap when in closed loop because the ecu is adjusting but when you are WOT the ecu can not self adjust therefore you will see more volitile AFR.

The turbulence and maf sensor position info brings to mind something I thought about the other day, having come from the world of 5.0 Mustangs. There is a company called C&L which makes a MAF that compensates for injector sizing in Ford 5.0 motors by changing the size of the sample tube that holds the MAF sensor inside the MAF housing. A caveat to using this meter was you often had to tweak the orientation of the meter in your intake setup by twisting it and positioning the sample tube in a sweet spot to make it read and work properly. Otherwise you would have issues with surging during cruise, and bucking.

Another problem that can arise is air buffeting the sensor right through the intake filter. Without much intake tubing in front of the MAF housing, if it's windy outside I wonder if this has a negative effect on readings? Just something I considered when comparing a SRI vs CAI in these cars. The filters for most SRI setups are right behind the headlight housing though, so I suppose it's not a huge concern but wondered if anyone had observed a problem.

 

[tru-boost]

Personally i would spend the $15 to buy an air straightener for the aem/MS cai before i butcher it and turn my cold air intake into a hot air intake.

 

[Trader]

Personally i would spend the $15 to buy an air straightener for the aem/MS cai before i butcher it and turn my cold air intake into a hot air intake.

Read my first post. I do have the air straighteners.

 

[mazdaspeed32007]

Personally i would spend the $15 to buy an air straightener for the aem/MS cai before i butcher it and turn my cold air intake into a hot air intake.

i checked my intake temps from the CAI to the SRI and there was not to much a difference. not sure about really hot areas since i live in MA so its not a huge difference.

 

[Mid_Life_Crisis]

Personally i would spend the $15 to buy an air straightener for the aem/MS cai before i butcher it and turn my cold air intake into a hot air intake.

It isn't being butchered. It's almost like they designed it to be dual use. Goes back with no problem.

 

[noobinacan]

I have been thinking for a while now to go SRI. (mostly cause its easier to clean the filter over time)
Does going to SRI mean that I won't get the pull from3k to 5k range.
but from 4k to 6k range ? like the COBB SRI does ?

How many folks have been running in SRI ?
any cel's or problems ?

thanks
I have the air straighter thingy installed.

 

[speedyM]

I have been thinking for a while now to go SRI. (mostly cause its easier to clean the filter over time)
Does going to SRI mean that I won't get the pull from3k to 5k range.
but from 4k to 6k range ? like the COBB SRI does ?

How many folks have been running in SRI ?
any cel's or problems ?

thanks
I have the air straighter thingy installed.

I have been running this SRI and so far so good. No CELs. One of the guys has mentioned in earlier post that since MAF is so close to the filter there might be some air turbulence that can cause misreads. I have seen that on my setup before. I had a CAI on before I went to SRI. I would say that the spooling is quicker with SRI but higher RPM range is not as strong, probably because I am pumping warmer air from the engine bay instead of a colder one from the fender well. I like the CAI a little better but it is "weather sensitive". A lot of rain and snow, means wet filter and that is not good for performance at all. In any case, anything is better than the Stock air box.