Should LTFT be this high with Cobb SRI?

[Lee456]

I checked the LTFT with my Cobb SRI installed today and was surprised when the numbers were much higher than with the factory airbox (with several holes cut in it and the snorkle removed) last week. With the Cobb the Dashhawk read +10.2 at idle, +15.6 when accelerating (whether mildly or wide open), and +8.6 when driving a steady 70 mph in 6th gear.

After seeing that I put the modified factory airbox back on. With it I got -3.1 at idle, 0.0 when accelerating, and -2.7 when driving at a steady speed. In each case after changing the airbox I double checked all the connections to insure they were tight, disconnected the battery and drained the charge, let the car idle for 10 minutes before driving it and then drove it about 15 or 20 miles in mixed conditions before writing down the numbers.

The performance definitely feels better with the Cobb, but aren't those number way too high? I read the other day that the Mazda standard is between -14.0 and +14.0 at idle, but the closer to zero the better and 10.2 at idle and 15.6 accelerating sounds way too high.

 

[scatt nasty]

that might be too high. Someone on the other forums mentioned anything above 8 or 9 is bad, so If your in the 15's and 16's thats no good. Im using the AP of course with upgraded internals and mine are always at 0

 

[DaleNixon]

Sounds high to me. I'll check mine out when my Cobb intake arrives on Monday.

 

[Moonpie.Express]

Just a question here. Did you reset the ECU each time (disconnect the battery)? I think that even then it takes awhile for it to adjust to the changes.

 

[LBV]

Just a question here. Did you reset the ECU each time (disconnect the battery)? I think that even then it takes awhile for it to adjust to the changes.

Quote from what he wrote: "In each case after changing the airbox I double checked all the connections to insure they were tight, disconnected the battery and drained the charge, let the car idle for 10 minutes before driving it and then drove it about 15 or 20 miles in mixed conditions before writing down the numbers.
"

 

[phillyb]

st00pid ******* fuel trims.
is your sri new?
when i changed my filter, my fuel trims went down

 

[Lee456]

Yep, it is new. One thing I forgot to mention is that I have an Amsoil filter on it. It's new, too. It is the one that was shown here a couple weeks ago that is considerable larger than the Cobb filter. I put it on right away because of a past bad experience with an oiled cloth filter. Suppose that is the problem? The car runs fine with the Cobb on it. Noticably more power and seems to respond faster. If I hadn't bought the darn Dashhawk and looked at the LTFT I won't have though anything was wrong at all.

 

[phillyb]

dh ftw
disconnect your negative battery terminal for 20 minutes, put the cobb filter on there, drive the car for 50-100 (maybe even more, just drive) miles, and report your ltft's

 

[DaleNixon]

Oh hell I don't want to hear that the Amsoil filter throws off trims. Mine hasn't even arrived in the mail yet :\

 

[phillyb]

d00d, i have no idea...just check the s*** out

 

[Moonpie.Express]

Quote from what he wrote: "In each case after changing the airbox I double checked all the connections to insure they were tight, disconnected the battery and drained the charge, let the car idle for 10 minutes before driving it and then drove it about 15 or 20 miles in mixed conditions before writing down the numbers.
"

Yep, Reading comprehension = fail.

and I read it twice!!!
(hand)

 

[Lee456]

I'll put the Cobb back on with the Cobb filter and try it. It will probably be a couple days before I get 100 miles on it since we've got plans for this afternoon and all day tomorrow, but when I do I'll post the LTFT with the Cobb filter. If it looks different than what I got yesterday with the Amsoil filter, I'll throw the Amsoil filter on and go through the whole process again and see if that changes it and will let you know.

 

[Lee456]

I don't know if anyone is still watching this, but here's the result. I unhooked the battery for 30 minutes, stepped on the brake to drain the charge, and put the Cobb intake back on with the Cobb filter. The LTFT numbers were:

After 18 miles: acceleration 13.3, constant 55 mph 4.7, idle 8.6
After 50 miles: acceleration 13.3, constant 55 mph 8.6, idle 10.2

At that point I put the Amsoil filter back on, didn't reset anything and drove 30 miles in a similar manner. There was no change, so the Amsoil filter does not seem to matter and 30 more miles of driving didn't either.

Perhaps these numbers are normal with a Cobb. It seems like additional fuel would be required with the extra air the intake lets in and these numbers indicate that fuel is being put in. The car is running great with it.

Anyone else with a Cobb and a Dashhawk, I'd be interested in what yours says. Also, if you've got an SRI on your car or any intake that lets you see the top of your transmission, please take a look at my other recent post about the hole in the transmission and let me know if your car has anything attched to the bolt hole in that picture. I'd go over to the dealer and look at another Speed3, but you can't see that area with the factory air box installed. Thanks.

 

[DaleNixon]

I think it's a bit early to measure LTFT's... don't you have to let the ECU relearn? Those numbers are really high compared to mine with the stock airbox or my old HKS intake.

 

[Lee456]

Yes they do seem high for sure. My stock airbox with three 1 1/2" holes cut in it and the snorkle removed was -3.1 at idle and 0.0 when accelerating. As for the ECU relearning, I didn't know how long that takes. The numbers were the same after 40 miles as they were at 50. The ones at 80 were also the same, so from 40 to 80 miles it didn't change. I would think that the relearning process would be reflected by gradually changing numbers like I saw from 0 to 30 or so miles after the reset, rather than not changing for 40 miles then suddenly making a massive adjustment. If I'm wrong about this and the ECU can be expected to have a revelation at 200 miles and suddenly bring these numbers down, please let me know.

I've swapped these back and forth a couple times and there's not a lot to do wrong, so I can't see how the high number can be a result of something installed wrong. If there's something I might have missed, let me know.

 

[DaleNixon]

I installed my Cobb SRI last night. LTFT's are around 8.8 when idle and vary between 5.5 and 8.8 when cruising/accelerating. Sometimes they sit at 0 but it's mostly 6.8 - 8.8.

I'll keep an eye on these numbers in the next few days as my ECU learns what's up.

 

[Lee456]

Thanks for the update, Dale. I finally said the hell with it and sold the Cobb. Unfortunately I think the bracket is a bigger issue and will take a substantial change in the mount. There's even a post from a Cobb rep over on the other forum saying that it is happening more frequently as time passes and they need to fix it. I was all set to build something that would attach to the larger bolts on the fender well near the Cobb mount, then have a section of rubber from an exhaust hanger running over to the Cobb bracket which I would have cut off. Needless to say, cutting the Cobb bracket would have made it hard to sell if this didn't work out. Late yesterday afternoon I found myself questioning why I should be doing all this work to correct at product I paid good money for.

The LTFT's went back to -2.3 at steady speed, +2.3 when accelerating, and -3.1 at idle with the factory airbox with holes in it. The car doesn't respond to the throttle as quickly, though, and I miss the sound. Maybe I'll try a Nano when they are back in stock, or maybe I'll just leave it. Anway, good luck with your Cobb. I'll be curious if your LTFT's go up over the next day or two as mine did or if they improve.

 

[DaleNixon]

Thanks man. I used some rubber to buffer the vibrations from the bracket, but I'm sure that's just pissing in the wind. Oh well. I'll continue to update this thread as I do more LTFT logging.

 

[DaleNixon]

I haven't logged, but I'm watching and the LTFT has started rising. I get around +11.8 when getting on it, then it goes back down to around +7 when cruising... very strange.

I reset my ECU today because I had to disconnect the negative battery terminal for a turbo timer install. On the drive home I was seeing the same behavior noted above.

Can anyone chime in as to whether or not these LTFT numbers are healthy? I read that anything beyond +4 or -4 is bad. But there are so many people running Cobb intakes. Maybe I should give Cobb a call to talk about this.

 

[john blutarski]

I finally monitored my LTFT's last night with the Cobb SRI. I'm seeing +5 to +7 at idle and +14.8 when on throttle/WOT. I ordered a CS intake/turbo inlet and will see how that compares...