COBB Stage 2 - How Bad is Humidity?

[SubieGuy4]

Couldn't quite determine where this should go but this seemed logical since the tune has a lot to do with the air entering the car.

I recently installed a 3" downpipe and flashed my 05 STi to Stage 2. The evening I did it and the following day it was around 70 degrees and humidity was pretty low. The car absolutely ripped and felt very together.

The few days since have been hot and I know what effect heat has, but how much does humidity screw with the car? Heat just makes the car less powerful but it seems as if humidity leads to rough running.

Lets say I'm at neutral throttle at 2500RPM in 2nd and I go WOT: It seems to buck a little and hesitate until getting up to 3-and-a-bit-000RPM and then when it gets there it doesn't feel all that smooth as it accelerates. I'm not expecting power under 3k, because I know the turbo needs to spool up, but the bucking is frustrating.

Thoughts? Is this just a matter of lots of humidity?

 

[Bluedemon_II]

Living on a very humid place I can tell you that it sucks. Humidity accounts for loss in air density and makes the engine work harder so you will feel a loss in power.

 

[SubieGuy4]

Right. I get the loss in power and it doesn't bother me, as it's expected. What I want to know is if that would be the cause of the rough running that I'm experiencing (which is mostly prominent off boost but heavy on the throttle).

 

[Vermont]

That sounds a lot more like knocking..... Is it most predominate in say 5th gear at low RPM's when you go WOT? IF so you might be looking at either bad gas causing the knock or something else. Either way you might want to log FBKC and FLKC on your access port....

 

[SubieGuy4]

No it happens predominantly in 2nd and maybe 3rd. If I ease on the throttle and go to full it doesn't happen. Only if I throttle suddenly.

 

[Vermont]

You should not be experiencing any bucking or lurching in 2nd or 3rd gear at low rpm's now, in 5th that is rather common just do to the gearing and the engine having to over come it. Although humidity and heat do sap power, you should not be experiencing rough acceleration.

You should do a log using your access port. Logging, Feed Back Knock Correction (FBKC), Fine Learning Knock Correction (FLKC), RPM, Manifold Relative Pressure corrected (boost), Engine Load (Calculated) (g/rev) and Accelerator Pedal Angle (%). Try and replicate the problem while logging said parameters. Try and keep the log as short as possible. Then take it and toss it up online using Google spreadsheet. Post the link up on here and I will see what I can do.

The person who has the most experience with tunning using Cobb would be HolyCrapItsFast. He uses Access Tuner Racer all the time. I use Open Source so I will only be able to help you are so.

 

[Bluedemon_II]

No it happens predominantly in 2nd and maybe 3rd. If I ease on the throttle and go to full it doesn't happen. Only if I throttle suddenly.

That is not caused by humidity. You have a throttle tip in problem. You need to log and see if you are to rich or to lean while tipping in.

 

[Rice Rocket]

Ive had this exact issue. I had to go to Cobb Plano TX to have Calvin fine tune my pro tune. I suspect your car is actually leaning out. Mine started when it got hot out also. Im sure you know the disadvantages to a OTS map. But contact Kevin Heist at Cobb Plano. He'll tell you how to data log the parameters they want to see. You send them the log and they can diagnose your issue.
On a side note going WOT from so low in the RPM range has been suspected to be the reason so manu cars break ringlands in the GR engine. So be waaaaay careful with that. STi are rev happy cars and do best above 3k RPM. When you accelerate from such a low RPM you place your motor under extreme load. I know the EJ has a ton of torque and its fun But i think this is actually how i blew my motor.

 

[Rice Rocket]

p.s. have you thrown any "PO171" fault codes / CELs?

 

[HolyCrapItsFast]

All good advice so far!!!

Get us a log and let's analyze it for you. The only things I would like to add to the log list is Throttle Position, Injector Duty Cycle, A/F correction #1, A/F Learned #1, A/F Senor #1 Ratio, Intake Air Temp and Closed/Open loop Switch.