Ill start out by saying im nowhere near proficient with tuning yet, but ive been reading and trying to learn as much as i can, so any help is greatly appreciated. I recently purchased an 03 evo with nothing more than an exhaust. A few minor bugs like adding the restrictors back in to get the appropriate amount of boost(1.3bar) were no problem, but im kind of at a loss with this issue. Basically i believe the car is hitting the airflow cut around 5k-6k in 3rd and 4th gears. I logged a few pulls with mitsulogger today and it appears the airflow is maxing out at 159.375. Ive also noticed that the temperature reading seems to be fluctuating wildly, and if anything i would expect it to go up during a full throttle run, but its dropping over 30 degrees between cruising and accelerating at full throttle. Ive posted a csv of the log i just made, and the lines of interest are around 698, 712, 1013,and 1134. Im basically just trying to figure out what component is causing my issues. I originally had planned on swapping out the MAF but now it seems like i may want to look into the temperature sensor, if such a thing even exists separately from the MAF. Sorry if ive managed to ramble on too long, but any help would be greatly appreciated.

 

Airflow maxing out?

That 159.375 is ECULoad and thats not even half the bits the real load is at the very end called "Load" in your table. No suprize that the temp drops while doing a pull becuase the temp sensor is in the MAF not in the intake. So of course once all the engine heat is sucked out it drops like a stone in cold weather.

There is no such thing as "airflow cut" but there is fuel cut. Read the tuning sticky.

https://www.evolutionm.net/forums/ec...-tune-evo.html

 

if what is happening is like you are hitting a wall then you are hitting your boost cut. try adjusting your boost limit table a little

 

Nothing out of the ordinary there? This is a stock car and I was assuming that unless something is wrong I shouldn't need to raise boost cut. I think something is causing it to think it's reading more airflow than there actually is.

 

Sounds like Boost cut or Fuel cut. Does the car have a Walbro FP.

 

Yes car has a walbro, but the problem was there before it was installed as well. Stock turbo and stock boost on the car. Im really confused as to why its doing this.

 

bump... I find it hard to believe that a stock turbo, stock boost car can actually be hitting boost cut without something being wrong. Anyone have any ideas?

 

Actually its really easy and happens all the time all you have to do is up the boost.

 

I decided to do a couple pulls tonight, and hit my first "boost cut". Felt like I hit a wall, and the first time it popped out of gear... Might have been a slip of the hand on the stick, though.

Now, Im not sure if its cause of the temp. change, or because of the new .xml (all of new boost/knock/periphery blobits patches) I just added last night, per mrfred,jcbanks and tephra, for the next ecuflash version. Temp change (which Im thinking is the culprit) was a ~ 20* difference. My question is would 20* difference in temp. (colder) cause overshoot of 3.5+ psi? I hit 28+ psi... My last log @ peak was @ 24.5. This is w/ "Direct Boost Control". I thought this method minimized the fluctuation in load/temp to make boost a bit more consistent...

I took the new .xml for the new ecuflash version (per mrfred) thank you! when it comes out, and added the map sensor stuff, the new boost tables, etc. to my version 1.39. Now Im not familiar w/ the periphery blobbits, (I know if you dont understand them, than dont add them, but I am assuming that the stock values are all correct...

 

I'm not using the direct boost patch yet, but with a GM 3 port, I've noticed about 1 PSI per 10 degrees dropped. This is just eyeing the gauge though.

 

seems to be fairly close... Im not exactly sure, but it might have been colser to a 30* change in temp. Which would account for ~ 3+ psi overshoot.

 

I think im gonna try to go for the direct boost control and see if it still happens. Is there a parameter for boost cut that i can log, or does that only show up with the MIL?

 

the parameters to log, for boost cut are load/rpm. "Boost cut" is load based (even w/ "direct boost control) you need to figure out if your overboosting, and if so you need to lower WGDC. If you are boosting where you wanna be, you will need to look up your boost limit table in ecuflash and increase your load value @ that rpm range.

 

Yep, im understanding that overboosting is the issue. The thing that threw me off is theres a delay between the overboosting and then the hitting of the wall. The load i have logged there is definately higher than my boost limit. I didnt understand that boost cut was just load until yesterday either. I have a JDM MAP on the car, so i need to set up mitsulogger to log that, as im going off a gauge now.

 

About 2-3 options down from the boost limit table is one labeled "Boost Cut Delay Timer". This is the one that's confusing you. Basically, when you overshoot the "boost limit" there is a countdown dependent on the number entered into the BCDT table. Usually the stock number is 1000ms, or 1 second. So if your peak load goes over the limit but drops back down within that 1 second time frame, you won't trigger boost cut.

The plain and simple truth is get used to hitting that limiter or raise it up a bit. One you decide to free up the flow a bit more you'll find yourself hitting back into it again. Take it up just a bit at a time depending on the max load of your logs if you want to retain the safety of the design.