USDM STI Idle and DBW throttle Issues

[Mr.Baer]

Hi, I have tried to change my profile info to give some info about me but it keeps asking me to log in to do so.

Car: 2004 Subaru WRX STi with every single thing changes I could
Location: Washington, PA USA
Occupation: Manager @ car dealership
Tuning Skill: Some learning as I go.
Diagnostic Skill: Relatively high gone through alot with this car.

About the Car:

Sleeved USDM ej257 block 9.5:1
+2mm Rods
Over sized valves on USDM WRX 25b heads
Single AVCS
Halleffect cam sensor
mag crank sensor
GTX3576r
45psi fuel pressure
ID2000 injectors
motec m800
motec PDM30
CDL3 dash
motec Wideband sensor
aem oil temp, oil pressure, fuel pressure, boost control solenoid
laille crank pulley
motiv TGV housings
Cosworth intake manifold
Custom Twinscroll Manifold
dual Tial 44mm wastegates


Onto my issues.

my idle, which I believe is coming from my DBW throttle set-ups.

as well as the ID2000 injector setups

The way that the Subaru adjust Idle is with the actually TB butterfly on these DBW cars. The butterfly on the TB stays open a crack and never closes.

My tuner thought that the TB was warped and that was causing this issue. However it is not, all of these TBs stay open a crack, so he didn't try to dial in the idle any better saying that he couldn't because the TB was broken.

The car also has a terrible bucking problem at low throttle inputs especially in 2nd gear where you spend most of your time when you are in any sort of stop and go traffic or puttering through a neighborhood to get home. It isn't as bad in the other gears as you typically have to give more throttle input to go the same speed at such a low speed.

Any help would be great.

M800 DBW settings3.pdf

(60.97 KiB) Downloaded 1352 times

M800 DBW settings2.pdf

(137.42 KiB) Downloaded 1202 times

M800 DBW settings1.pdf

(24 KiB) Downloaded 1380 times

[PQatPIT]

What fuel?

Those 2k injectors are not the easiest to get right at low loads and low rpm's.

[stevieturbo]

What fuel?

Those 2k injectors are not the easiest to get right at low loads and low rpm's.

A few years ago I switched from ID1000's to ID2000's on an M800 pnp 2.35 Subaru, 2002 EDM STI model

The transition was smooth, and were very impressed by the 2000's, still idling and driving happily in the 14.x AFR range

Not saying they'll be perfect in all applications, but they worked great on that one. The 1000's were just too small.

[Mr.Baer]

The car has a Flex Fuel Sensor and is tuned to BP 93 octane, then was tuned for E85.

I am being told that I have a mechanical issue with my throttle body. I had a ferrule welded onto the TB for a wiggins clamp, that I am being told warped the TB. So I measured the gap around the butterfly of the TB and it is .005" around it. I feel that this not an excessive amount of area around the throttle body, but I do not really know. I know it should be as tight as possible but damn that seems like a pretty tight tolerance.

[stevieturbo]

Does the blade move freely and as expected ?

I assume you can log both pedal position and blade position ?

[Mr.Baer]

As far as I can tell it is moving freely, I am not sure how to measure the blade position vs the tps. I know where to see tps but not as sure about blade position.

[stevieturbo]

Ive never used DBW on a Motec so cant say.

But I'm sure there must be some way to view both blade position and pedal position. It would be crazy not to have these logable or viewable.

All DBW units I'm aware of use this feedback both for control and safety, and usually there are two tracks, again for safety reasons.

ie 2 on the pedal, and 2 on the blade for safety/fault detection.

[Scott@FP]

First off, both sets of sensors (pedal and throttle body) need to be properly calibrated.

If you don't have aux2 set to function 'DBW-Idle' you don't HAVE DBW idle control, just pedal position translation. TPD 0% should NOT equal TP 0%. Also set your min TP% to a true 0% by forcing the blade closed, they won't close all the way by themselves.

You can get a pretty good idle by using the translation tables alone, but it will be better with some time using DBW Idle. Start with very small numbers in the PID settings, minimal possible (.01)for P and D, 5x more for I works best for me.

Street car- should set pedal position translation at 0% TPD (driver request) to desired idle speed at various coolant temps and let DBW idle take over once you are below max vehicle speed for Idle Control.

Bucking at low throttle isn't usually idle control related (esp if it is turned off) its usually fuel or timing.

Tuning WOT is easy, its all the 'little things' factory ECU's do well like idle control that take time.

And for gasoline, get the 3D inj battery comp table from ID for the ID2000's.

[Mr.Baer]

I calibrated the TB. It came in at 12 for closed and 94 for open , then I recalibrated for TB2 thinking that is how it controls the idle. Not sure if I did that right or not.

I also go the 3d Battery table from ID. I am going to work on the idle this morning.

[Scott@FP]

TP and TP2 are the sensors in the throttle body, they both need to be calibrated at the same blade position. Blade needs to be held closed so it knows where actual, fully closed is, most have a spring loaded mechanical default position which is slightly open (think limp in) and will not fully shut on their own. Most round blade throttle bodies flow more air when the blade is not quite 90 degrees to the bore, hold it to slightly less than 90. Watch your fingers around live, powered up DBW throttle bodies, them sumbucks can take a finger off. Temporarily disconnect pins A1 and A18 (aux 2 and aux 1) so the motor won't power up when calibrating.

TPD and TPD2 are the pedal sensors, they both need to be calibrated at the same pedal position.

Enable DBW Idle on aux2, fill in Idle Control tables but leave PID's at zero until your position translation tables (and comps) and fuel/timing at 0% TPD are close to maintaining a decent target idle, then play with DBW Idle settings.

Idle Control Setup-

dead band- 10 to 50
activate TP 1 to 2%
activate gnd speed- I like higher speeds, 40-60
activate RPM- 100-200 higher than highest idle aim RPM
RPM filter works hand in hand with PID values, higher PID values like higher filter values, low filter + high PID's = jumpy hyperactive control, low PID's + high filter= lazy control. TP and TP2 input filtering also play a role, but start low and increase if inputs noisy.

Idle Control tables-

Aim RPM- desired idle RPM, use Engine Temp X axis
Idle min/max output- TP% min and max during idle, approx. 1% to 10%
Idle min/max int limit- use small values, like -3/+3 or less.
Normal position table- Engine Temp X, Idle AIM Y, fill table in as you get proper data for various temps and idle aim RPM's. This table is important to get right.

Make a strip charts showing idle position, RPM and Idle AiM RPM, Idle AIM Error. Watch for smooth control that reacts when needed and is not hyperactive or too slow to react.