power dip at 3.5k rpm??

[engr]

Hi Guys,

I need your help.. west minist and I are trying to tune my 2002 4eat wrx with the following mods

helix up
brullen bellmouth 3" DP with high flow cat
Genie 2.5" exhaust
samco intercooler hose
stock ecu flash using ecuedit with boost target set for 17psi or so.

We can't seem to figure out why the power dips at 3.5k so drastically, The dip existed in stock form, but not as big.. we've tried adjusting the timing, the fuel, o/c loop delays.. any idea what can be causing this? or how to tune it out? or what could cause this?





logs are attached..

[west_minist]

Please also note that this dip exist in a stock ecu.

Dips exist in all tuning from stock >> Cobb >> Ecuedit.

Do veiw the Fuel Injector too much, since outside is cold and more tuning (lo boost) is needed in the high range.

Theories are:-

1) Ignition system
2) Spark Plugs
3) Leaking turbocharge system
4) Tumble vavle issues

I am trying to get some logs on the Tumble vavles.

[calvinc]

1 or 2) does the car stutter/surge on acceleration?
3) if your boost does not match your targets then possibly

calvin.

[engr]

there is not stutter during accel, only a decrease in power in that rpm range, and then it picks up again.. the car runs fairly smoothly otherwise..

[x99percent]

Compare your torque curve to your boost, AFR, and ignition timing...?

[west_minist]

From the logs, everything looks good. You can see small changes in the affected region, but nothing to highlight the problem.


THe car makes good boost.

It looks like when the car goes to make full torque, some thing happens.

I wonder if it could be the transmission, but the rpm does not increase in that area.

That torque curve shoudl not look like that at all. This behaviour is even in the stock map.

It would be nice if the up/dp can be replace w/ stock to see if this issue still occurs.

What I can stay, the car loves timing. The first I ever tune that loves timing. Normally the stock map is be too much. Not with this model @ all.

[JRSCCivic98]

Lower your boost in that section... you're hitting 17.xx psi in that area. Also your KC drops to 7 and timing takes a big dive in that area as well. There's either something wacky with the fuel or you're getting det in that portion of the map. I'd be willing to say that the ECU is pulling timing. Drop your boost and see where you are. Could also be some kind of false knock sending the ECU for a loop. A slight side note... - or + A/F corrections of your amount is not a good sign and sometimes points to a bad primary O2 sensor... which could easily cause the issue you're describing.

[west_minist]

I am very sorry that Engr posted this log w/o the stock and Cobb stg.

As stated before, this behaviour effect is in Stock, Cobb stg2 and tuning rom.

IT IS NOT RESTRICTED TO THIS ROM.

The kc is correct in that area.

Nothing wrong @ all. Since the actuator change, the car is now outside of the load range on the maps and would need to be rescale now.

[JRSCCivic98]

What is the exact history of this problem? (Something that's always happened before any OpenECU tuning took place.) Or something that surfaced after that which doesn't seem to go away even if you go back to a stock ROM?

[west_minist]

The car was noted tohave a little dip in that region was suppose to be some slack pipes, since it occurs when the car is alnost @ full spool.

The dips shows themselves up more since the poer have increase, making that change more felt, butthe dip is still around the same range.

He is not sure if the new up/dp is causing the problem.

The thing is, he feels it. If he didn't, we could blame the tranny.

At this point, we are just lost. If he could put the system back stock, we could see.

[west_minist]

Hey, could it be the valve seals? The car is over 140KM.

Alright. Let have some fun here.

The really issue seems to be around 3300-4500rpm.

We tried some stuff, but I feel its related to boost or something happening when boost crosses a certain point. I will disable boost and see what will happen. But look below.

Now remember, its has nothing to do with the tune.

All from a Stock ECU ROM. No mods to it.

[west_minist]

This rom boost curve with actuator tight, dp/up + 2.5" exhaust.

[engr]

the dip had always been there, even on stock map with stock pipes.. but was not as noticable since power was mild, now with more power on tap, the dip is very noticable..

I just did some readings on the TGV valve, and they both pegged at 0.30V and 0.32V.. shouldn't they be at like 4V+ off idle?

[calvinc]

Lower your boost in that section... you're hitting 17.xx psi in that area. Also your KC drops to 7 and timing takes a big dive in that area as well. There's either something wacky with the fuel or you're getting det in that portion of the map. I'd be willing to say that the ECU is pulling timing. Drop your boost and see where you are. Could also be some kind of false knock sending the ECU for a loop. A slight side note... - or + A/F corrections of your amount is not a good sign and sometimes points to a bad primary O2 sensor... which could easily cause the issue you're describing.

- timing will traditionally drop on high load/boost, you should map it to do that
- AM doesn't drop so KC should be at max of ignition correction map, for that RPM vs Load cell
- false knock signal would induce lower AM
- there should be no A/F correction for WOT, they are not used in open-loop

calvin.

[calvinc]

its possible that your ignition timing is too low. if you have a trough in the map (for safety) it could well be the reason of lower torque. cylinder pressures will drop = less power.

try adding more ignition correction values to that range of the map. adding to the main ignition map is risky because you might induce det. go as high as 12 for the range 3200RMP - 4000RPM, engine load 2.4 - 5.3. 7 is quite low already.

calvin.